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The formation of gaps serves as a pivotal force in shaping forest dynamics, especially in highly disturbed environments like coastal shelterbelt forests, but few studies have delved into evaluating the gap features in these forests and their impact on seedling regeneration. We investigated the gap features, microhabitat heterogeneity, and seedling regeneration of the woody species within canopy gaps of different sizes (small, medium, and large) in a mixed coastal forest of eastern China. We also evaluated the effects of gap features and microhabitat factors on seedling performance. The coastal forests under investigation had predominantly small gaps (56 %), with the large gaps only accounting for 16 %. Irrespective of gap size, the gap center was associated with higher light intensity, wind speed, and herb coverage but lower air humidity, litter thickness, and soil salinity than the gap edge positions. However, large gaps stood out with higher light intensity and wind speed but lower air humidity, litter thickness, herb coverage, and soil total nitrogen than small or medium gaps. Gap size also exerted a significant impact on the seedling regeneration pattern of woody species, for example, in small gaps, Robinia pseudoacacia seedlings had the highest species importance value, while in medium and large gaps, Ligustrum compactum showed the highest importance value. Upon the monitoring of seedling growth, we observed significant interspecific variations in the survival and growth rates of the seedlings, with R. pseudoacacia and L. compactum had the most potential to serve as the gap fillers. Gap size, within-gap position, and their interactions all significantly affected the seedling regeneration, but within-gap position was the primary feature affecting regeneration. A path analysis provided further clarification on the direct and indirect impacts of microhabitat factors on crucial metrics pertaining to the seedlings, in which light intensity and soil total nitrogen exhibited significant positive effects enhancing seedling regeneration. By contrast, wind speed and soil salinity exerted inhibitory influences that hindered the regeneration process. These findings bridge the knowledge gap in understanding the regeneration dynamic of woody species and the critical factors that shape seedling regeneration in natural gaps of coastal shelterbelt forests, which would facilitate the gap-based silviculture in the future to restore the degenerated shelterbelt forests of eastern China. [Display omitted] • The size of canopy gaps in coastal forests were relatively small. • The effects of within-gap positions on seedling regeneration should be considered. • Light intensity and soil total nitrogen greatly advanced the seedling regeneration. • Wind speed and soil salinity suppressed the regeneration. • Robinia pseudoacacia and Ligustrum compactum are most suitable species for gap filling. [ABSTRACT FROM AUTHOR]

As soil structural units, soil aggregates are crucial in soil total nitrogen and organic carbon sequestration, which has been gradually discovered by scholars. However, how aggregates affect the storage of soil organic carbon and soil total nitrogen pools through aggregate proportion and their carbon and nitrogen content, remain unclear. Here, we examined soil aggregate composition, and the characteristics of aggregate-associated organic carbon and total nitrogen under different recovery years (15, 30, and 45 years) to explore the contribution in different sizes aggregates to soil carbon and nitrogen accumulation and its driving factors across different vegetation types of Natural grasslands (NG), Caragana korshinskii plantations (CK), and Robinia pseudoacacia plantations (RP) on the loess hilly areas. The results indicate that microaggregates dominated all soils, with the average proportions of 44.91 % in NG, 44.47 % in CK, and 42.19 % in RP. Yet, with the increase of recovery years, the proportion of microaggregates reduced and the proportion of macroaggregates rised. After vegetation restoration, the contents of carbon and nitrogen in soil and aggregates were increased. In addition, macroaggregate contributed more than 71.5 %, 67.0 %, and 67.9 % to organic carbon and total nitrogen stocks in NG, CK, and RP, respectively. The result that highlights the fact that macroaggregate is critical drivers of soil organic carbon and total nitrogen accumulation in different vegetation types. The growing percentage of macroaggregates was a key factor in the accumulation of soil organic carbon and total nitrogen stocks in NG, while the increasing percentage of macroaggregates and their associated carbon and nitrogen contents jointly led to an explicit increase in soil organic carbon and total nitrogen stocks in CK and RP. Overall, our findings revealed the soil organic carbon and total nitrogen accumulation process mediated by macroaggregates during vegetation recovery period on the Loess Plateau, providing a scientific basis for a deeper understanding of the potential of soil organic carbon and total nitrogen sequestration during the vegetation restoration in fragile habitats. [Display omitted] • Revegetation decreased microaggregate and increased macroaggregate proportions. • C and N contents in bulk soil and aggregates were promoted after restoration. • Macroaggregates plays a key role in C and N accumulation in all vegetation types. • Increased macroaggregate proportion promoted C and N accumulation in NG. • Increased C and N contents and proportion of macroaggregate promoted C and N accumulation in CK and RP. [ABSTRACT FROM AUTHOR]

Forests are exposed to human-induced and natural disturbances generating opportunities for new species to establish, including non-native woody species. Understanding how disturbance characteristics interact with the site context and invasive species traits to drive invasion processes is crucial for designing sustainable forest management. Here, we use the case study of the deciduous broadleaved forest belt of Canton Ticino (Switzerland) to identify the main factors determining the presence of non-native invasive woody species in recently disturbed forests. We identified and selected 851 forest gaps caused by natural, silvicultural or other anthropogenic disturbances between 2008 and 2015. For each gap, the presence of non-native invasive woody species as well as the characteristics of the corresponding landscape, site, and the gap itself were determined. For the six most frequent non-native invasive woody species, we identified the parameters that influenced their presence by means of modelling approach. The resulting variable coefficients were then used to create maps of colonisation risk. Among the six target species (i.e., Ailanthus altissima, Buddleja davidii, Robinia pseudoacacia, Paulownia tomentosa, Prunus laurocerasus, and Trachycarpus fortunei), the factors influencing their presence were either shared (e.g., distance to the next colonisation hotspot), partially shared (e.g., distance to buildings, altitude, aspect), or completely species-dependent (e.g., topography, slope, distance to powerlines). Like in other mountainous areas, non-native invasive woody species concentrate at low altitudes and near densely populated areas where hotspots of seed-bearing individuals can be found. Moreover, different life-history groups (i.e., wind-dispersed pioneer species vs. animals-dispersed evergreens) shared specific invasion patterns characteristics. In addition to general management strategies, we argue that more species-specific strategies should be adopted to prevent the colonisation by non-native invasive woody species. In this context, the consideration of seed-bearing individual hotspots should be given highest priority, followed by the type and the characteristics of the disturbance. [Display omitted] • Disturbances and landscape feature modulate invasive woody species colonisation. • Colonisation patterns are either shared or species-specific. • Invasive woody species concentrate at low altitudes near seed-bearing individuals. • Removing seed-bearing individuals before a silvicultural intervention is crucial. • Colonization risk maps are provided to plan accompanying measures after a disturbance. [ABSTRACT FROM AUTHOR]

Highlights • Black locust plantations are always lighter, warmer and less humid. • Contain more non-forest, ruderal and significantly higher number of alien species. • The largest impact of black locust was recorded on the mixed oak-hornbeam forests. • The smallest impact was recorded on the floodplain forest. Abstract Information about invasive alien species and their interactions with the environment and native ecosystems is very important to prevent widespread loss of original habitats and biodiversity. Black locust (Robinia pseudoacacia) is one of the most widespread alien plant species in Europe and has become a dominant forest tree species, which is frequently planted. We analysed how environmental factors (light, temperature and humidity), species composition and level of invasion changed in black locust stands compared with those in different neighbouring native forest types (floodplain, oak and mixed oak-hornbeam forests). The aims of this study were to determine (i) how the microclimatic conditions of the native forests changed after replacing the native trees with black locust, (ii) how black locust changed species composition and level of invasion of the understory and (iii) whether black locust equally influenced the three types of native forests. The results showed that compared with those of the other forest types, the conditions of black locust stands were always warmer and drier with more light from the sparse canopy of trees. In the black locust forests, we recorded more non-forest and ruderal species with significantly higher percentage number and cover of alien species in the understory vegetation than in the native forest stands. Different native forest types and their black locust twins were mutually influenced in a different way. The mixed oak-hornbeam forest was the type most influenced by replacement with black locust, whereas floodplain forest changed the least. Black locust plantations replacing native forests cause decreasing native species biodiversity, because of the occurrence of alien, ruderal and non-forest species. The dry and warm character of black locust stands contributed to an acceleration of microclimate change. This information can be useful for forest managers and planners participating in the replacement of native forest stands by alien tree species, which has ecological and economic impacts with consequences for nature and society. [ABSTRACT FROM AUTHOR]

Highlights • Accurate and quickly evaluate forest quality based on satellite images. • Four MLAs were implemented and compared to estimate forest parameters. • RF obtained the highest accuracy and was used to estimate forest parameters. • The RF predicted forest parameters can be used to assess forest quality effectively. • Forest quality in different stand age classes was a foundation of forest management. Abstract Forest parameters have been estimated using various regression methods based on satellite data. However, there are a few concerns regarding further application of these predicted parameters. Current forest quality (FQ) assessments are mainly based on forest parameters collected in the field. To evaluate FQ quickly and comprehensively, forest parameters estimated from satellite images can be used. Black locust (Robinia pseudoacacia) plantations have experienced increases in tree mortality and reductions in tree growth caused by human destruction and poor natural conditions on the Loess Plateau. Assessing the FQ of the black locust plantations in these areas is critical. In this study, four machine learning algorithms (MLAs) – classification and regression tree (CART), support vector machine (SVM), artificial neural network (ANN) and random forest (RF) – were first implemented and compared regarding their ability to estimate forest parameters of black locust plantations on the Loess Plateau. The results indicated that among the four MLAs, the CART method achieved the lowest accuracy, the SVM and ANN methods had moderate performances, and the RF obtained the highest accuracy and lowest error for all forest parameter estimates. As a result, the RF algorithm was chosen to predict the forest parameters. The highest R2 values among the forest parameters were predicted for the diameter at breast height (DBH, R2 = 0.85 and relative root mean square error (rRMSE) = 0.18), and the lowest R2 values were predicted for the forest aboveground biomass (AGB, R2 = 0.66 and rRMSE = 0.25). These predicted forest parameters as well as the topographic factors derived from a digital elevation model (DEM) were used to assess the FQ of the study area. Among the four stand age classes, the middle-aged forest had the lowest proportion of poor quality forests (7%) and the highest proportion of good quality forests (52%), whereas overmature forests presented a moderate proportion of poor quality forests (23%) and good quality forests (21%). These results provide the necessary foundation for forest management and guidance for regional reforestation on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Highlights • Our study adopts a dynamic contrast method to accurately quantify the effect of planting Robinia pseudoacacia (RP) on soil moisture. • The greatest amount of soil water consumption under RP was observed at 150–180 cm. • Soil water consumption under RP mainly occurred in the first 20 years. Abstract Soil moisture is crucial for the sustainable development of artificial forests in arid and semi-arid regions, and an accurate quantification of the influence of artificial vegetation on soil moisture has profound implications in the assessment of the ecological effects of artificial vegetation in arid and semi-arid regions. This study analyzed the variations in the soil moisture content (SMC) following the conversion of croplands into forests with Robinia pseudoacacia (RP) at different vegetation ages (5, 20, and 40 years) in the Loess Plateau and attempted to regard abandoned cropland (AL) with different restoration years (5, 20, and 40 years) as control samples to accurately quantify soil moisture depletion in the absence of RP at different ages. The results showed that the SMC of the 0–500-cm soil profile, which the zone that supports the whole growth processes for RP in the study area, was in a state of depletion, with an average water depletion of 40.75% and a maximum water depletion of 68.39%. RP mainly consumes shallow soil moisture (0–100 cm) during the early stage of afforestation, and with increases in forest age, RP mainly consumes soil moisture at increasingly deeper layers (100–500 cm). The largest soil water consumption in the presence of RP was observed at 150–180 cm. As RP forests grow, the water demand increases and shifts from the upper to deeper soil layers, and when the deeper soil water consumption reaches a certain level, the water consumption shifts upward. This phenomenon results in different degrees of drying between surface and deep soil layers over time. Abandoned cropland has a decreased influence on the SMC of the whole profile and appears to benefit water conservation at deeper soil layers in the mid-recovery period. Therefore, the vegetation succession in control plots should be considered to enhance the accuracy of the findings in future soil moisture research and afforestation practice. To maintain the sustainability of afforestation, succession should progress from less to more advanced plants (grasses-shrubs-forests), and the cultivation of shallow-rooted herbaceous plants (the main herb species in abandoned croplands) and natural restoration should be prioritized. Moreover, the ecological importance of natural restoration should be considered, the degree of blind artificial transformation should be reduced, and the strong adaptability and evolutionary ability of tree species to survive should receive proper attention. [ABSTRACT FROM AUTHOR]

Highlights • Phosphorus and water are the key belowground resources for growth partitioning. • Significant interaction between above- and belowground resources. • Large trees grow disproportionally more, if competition is aboveground. • Plant available nitrogen as belowground resource has no influence to competition. Abstract Competition for above- and below-ground resources depends on their availability and results in varied growth partitioning. This becomes clear as the supply and limitation of the main resources influence the slope of the size-growth relationship in stands. Nevertheless, growth partitioning among trees, especially among black locust (R. pseudoacacia) trees is not understood in sufficient detail. To scrutinize and estimate the mode of competition of R. pseudoacacia, this research analyzed 1333 trees in Germany in 10 study sites, consisting in total 27 sample plots, with similar climate but varying soil conditions. The stand age ranged from 2 to 32 years, with a diameter at breast height ranging from 0.6 to 29.1 cm. The main focus of the study was to evaluate the impact of nitrogen, phosphorus, and water supply on the competition mode of R. pseudoacacia by varying growth partitioning. We applied the size–growth relationship in a mixed-effects model with a random intercept and slope. Fixed effects were the basal area, phosphorus, water, the sunlight competition index, and the interactions between below- and above-ground resources. Site specific effects of the analyzed stands were quantified with the aid of the random effects. Depending on the supply and limitation of phosphorus and water, this study determined how the competition mode as well as the growth partitioning among R. pseudoacacia trees were influenced. Hence, if phosphorus and water availability increased, then the competition for above-ground resources (primarily sunlight) and the slope of the size–growth relationship increased. Large trees grew disproportionately more than smaller trees. If the available phosphorus and water decreased, then the competition for the below-ground resources increased and the slope of the size–growth relationship decreased – to be more flattened. Moreover, it was found that available nitrogen as a below-ground resource had no influence on the mode of competition. In summary, phosphorus was the most important nutrient and, together with water, was the main driver of growth partitioning among R. pseudoacacia trees. [ABSTRACT FROM AUTHOR]

• Understory and soil responses to stand density varied with stand age. • The shrub layer was less responsive to stand density changes than the herb layer. • Soil and understory quality peaked at medium density in young and middle-aged stands. • In mature plantations, low stand densities increased understory diversity and soil quality. Robinia pseudoacacia is the most important tree species used for afforestation on the Chinese Loess Plateau. However, most R. pseudoacacia plantations face environmental problems due to inappropriate initial densities. The sustainable development of R. pseudoacacia plantations is challenging due to significant knowledge gaps regarding the appropriate stand densities for maximizing ecological benefits. Herein, R. pseudoacacia plantations of three age classes—young, middle-aged, and mature—were sampled in the loess hilly-gully region of northern Shaanxi Province, China. Based on stand density, R. pseudoacacia plantations in each age class were categorized as low (<1000 trees ha−1), medium (1000–1500 trees ha−1), and high (>1500 trees ha−1) density. We analyzed the effects of stand density on soil physicochemical properties, understory vegetation community structure, and ecosystem multifunctionality. In young stands, a medium stand density significantly increased the Shannon-Wiener index, species richness, and above-ground biomass of herbaceous communities. In middle-aged stands, stand density had no significant effects on understory diversity, whereas medium-density stands showed increased understory above-ground biomass. In mature stands, low-density stands significantly increased understory above-ground biomass and species richness of herbaceous communities. In all age classes, stand density did not significantly affect shrubby community composition, but herbaceous communities shifted compositionally towards shade-tolerant and drought-tolerant species as stand density increased. In the soils of young and middle-aged stands, organic carbon, ammonium nitrogen, nitrate nitrogen, available phosphorus, and water content were highest in medium-density stands, whereas in mature stands, these variables were highest in low-density plantations. In young, middle-aged, and mature stands, the ecosystem multifunctionality indices were highest at densities of 1000–1500, 1000–1500, and < 1000 trees ha−1, respectively. We concluded that the effects of stand density on ecosystem functions in R. pseudoacacia plantations varied with stand age. Our findings highlight a need to implement age-based stand density management strategies for R. pseudoacacia plantations to improve their ecological benefits. [ABSTRACT FROM AUTHOR]

• Robinia pseudoacacia changes abiotic conditions to warmer, drier and lighter. • Various taxonomic groups react differently to planting R. pseudoacacia. • R. pseudoacacia influences the diversity of the understorey vegetation significantly. • Gastropod and carabid beetle groups are less affected by Robinia planting. • Native forest has higher acoustic diversity due to food and shelter options. There is much knowledge about the impact of non-native Robinia pseudoacacia on native ecosystems, but mostly it is related to one group of organisms. In this article, we provide an analysis of the impact of R. pseudoacacia on the surrounding biota with a broader scope in a model area with homogeneous abiotic conditions compared and analysed by the twin plots method. Microclimatic conditions and the changes in the species composition of vegetation, terrestrial gastropods, carabid beetles, bats, and acoustic diversity were analysed. The planted Robinia stands were always brighter and warmer and had lower canopy closure than the control plots in the native floodplain forest. More nitrogen and phosphorus were recorded in the soil of the Robinia stands. The floristic composition changed the most based on the planting of Robinia trees. Compared to those in the adjacent floodplain forest, more heliophilous neophytes, archaeophytes and grasses were found. Assemblages of gastropods and carabid beetles were less affected by the planting of Robinia trees and more by the microclimatic conditions of the studied locality. The number of recorded bats and acoustic diversity were higher in native floodplain forests due to food and shelter options. All results show that the planting of Robinia trees changes the microclimatic conditions and species composition of forest stands. The warmer and less humid environment under Robinia stands is not desirable in the face of ongoing climate change. The alien (including invasive) and ruderal plant species in the understorey are supported due to the more favourable brighter conditions and nitrogen fixation in the soil. Additionally, the other groups of organisms react negatively to changes under Robinia trees in terms of microclimatic conditions, food and shelter sources. Therefore, forest managers, policy-makers and conservation workers should choose stratified management when deciding whether and where to plant R. pseudoacacia. [ABSTRACT FROM AUTHOR]

• Walnut growing on mine spoil banks, alone or associated with a N-fixer, was studied. • Italian alder positively influenced walnut growth, also by improving stem shape. • Black locust enhanced soil quality more than alder, increasing organic matter and porosity. • Due to its invasive nature, black locust eventually depressed walnut, nearly eliminating it. Mining activities have a major impact on the environment, depressing several ecosystem services. Afforestation is an efficient approach to recovering abandoned mining areas. This paper aims to assess the suitability of common walnut (Juglans regia L.) for planting on mine spoil banks for wood production, hydrogeological protection, and climate change mitigation. The paper also examines if associating walnut with a nitrogen-fixing species, such as Italian alder (Alnus cordata (Loisel.) Duby) or black locust (Robinia pseudoacacia L.), is advantageous compared to monoculture for the mentioned objectives. For this purpose, contiguous stands of pure walnut and walnut intercropped with one of the two nitrogen-fixing species were studied. The stands had been growing for 34 years on the spoil banks of a lignite mine in central Italy that was abandoned in the 1980s. Overall, walnut in monoculture showed good performances on the infertile substrate, in terms of both growth and stored carbon. On average, in fact, walnut showed a mean height of 16.2 m and a woody volume of 70.1 m3/ha, and had stored 16.5 Mg C/ha between above and below ground. However, walnut significantly benefited from the association with Italian alder, which stimulated the early growth of walnut (up to 15 years) and improved the commercial quality of woody assortments. At the current age, walnut showed significant differences in diameter at breast height (DBH, 44.6%) and total height (H, 17.9%) between the stand where it was originally interspersed with 75% Italian alder and the stand where it grew in monoculture. Alder did not improve soil carbon sequestration, while black locust showed a greater soil improving capacity than alder when associated with walnut, both in terms of organic matter enrichment and bulk density decrease. However, black locust impressive growth rate and strength in chasing suckers induced high walnut mortality. Our results demonstrated that Italian alder is to be preferred to black locust as a nitrogen-fixing species to be associated with walnut, at least in the pedoclimatic and environmental conditions we dealt with. [ABSTRACT FROM AUTHOR]

• N and P requirement of Robinia pseudoacacia increased significantly with stand age. • The dependence of plants on nutrient resorption decreased after afforestation. • The nutrient competition between plants and soil microbe is a win–win mechanism. • Soil EEAs were the factors directly affecting the mineralization process. Plant nutrient requirements and acquisition strategies are critical to understand the net primary productivity and community stability in terrestrial ecosystems. However, the current knowledge regarding this subject is limited, especially in the case of afforestation. Therefore, we selected four Robinia pseudoacacia (RP) forests (15-, 21-, 31-, and 46-year-old forests) in the Loess Plateau, and analyzed the nutrients in the plant organs, litter, and soil, along with the extracellular enzyme activities (EEAs), microbial biomass, and mineralization rate. In addition, the biomass of RP was determined using an allometric growth model. The results showed that during afforestation, the nitrogen and phosphorus requirement of RP increased significantly, from 3.97 to 18.14 g·m−2·year−1 and 0.17 to 0.71 g·m−2·year−1, respectively, while the nutrient resorption efficiency and the contributions of nutrient resorption to the total nutrient requirements significantly decreased. Meanwhile, the ratio of nitrogen to phosphorus resorption efficiency (NRE:PRE) significantly increased with afforestation, but were less than 1 which may indicate the phosphorus limitation of RP decreased. In addition, the vector angle significantly increased form 44.80° to 49.51° after afforestation, which may indicate the phosphorus limitation of soil microorganisms increased. Meanwhile, the vector angle was significantly positive with phosphorus mineralization rate and NRE:PRE, which may show that soil microorganisms activity alleviate the phosphorus limitation of plants. Collectively, our study contributes to a better understanding of nutrient cycling above and below the ground. [ABSTRACT FROM AUTHOR]

Afforestation with single and mixed tree species on cropland alters soil properties and the composition and diversity of soil bacterial community. We investigated changes in soil properties and the soil bacterial community composition in the topsoil (0–20 cm) following afforestation on cropland on the Loess Plateau. Forests of six types ranging from 23 to 25 years in age were chosen in this study: Robinia pseudoacacia (RP), Platycladus orientalis (PO), Pinus tabuliformis (PT), Robinia pseudoacacia  +  Platycladus orientalis (RPPO), Robinia pseudoacacia  +  Pinus tabuliformis (RPPT), and Platycladus orientalis  +  Pinus tabuliformis (POPT). Afforestation with different tree species altered the soil nutrient contents, with total nitrogen (TN) and ammonium nitrogen (NH 4 + ) contents increased by 18.28–87.10% and 13.97–141.34%, respectively, and available phosphorus (AP) content decreased by 56.09–82.13% compared to cropland sites. Cropland afforestation reduced the soil bacterial richness and core bacterial genera abundance (relative abundance ≥ 0.1%), and significantly altered the bacterial diversity. Soil properties explained 73.41% of the total variation in the core soil bacterial community composition at the genus level, and soil organic carbon (SOC), TN, nitrate nitrogen (NO 3 − ), NH 4 + , AP, pH and the carbon:phosphorus (C:P) ratio were significantly correlated with first two RDA (redundancy analysis) axes. The results of hierarchical clustering indicated that the soil bacterial community composition in the RPPO, RPPT and POPT sites was largely affected by Platycladus , Pinus tabuliformis and Platycladus , respectively. Our observations suggest that soil bacterial community composition and diversity following afforestation were mainly affected by tree species, followed by soil parameters. The effect of afforestation on the soil bacterial diversity was larger than its effect on bacterial richness. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) partitioning is crucial for understanding the impacts of ecophysiological and physical processes on water balance and plant water use strategy. Black locust ( Robinia pseudoacacia ) is one of the most widely planted species in the semi-arid Loess Plateau, China. The effects of its water use on stand soil water storage (S) and its water use strategy raised much concern due to soil water depletion and its growth degradation. In this study, meteorological factors, soil water content (SWC), ET components and net primary productivity (NPP) were observed in a black locust plantation during a drier (2015) and a wetter (2016) growing season. ET was 160.0 mm in 2015 and 255.0 mm in 2016, which accounted for 104.1% and 68.6% of the precipitation (P), respectively. Soil evaporation (E) accounted for the majority of ET (45.4–69.4% at monthly scale), while transpiration (T) was the smallest component of ET (9.7–28.8%). These results showed that it is E that consumed more soil water rather than T in the black locust plantation. E should be carefully considered and improved in predicting or modeling water budgets (e.g. soil water, ET partitioning and runoff) in the reforested catchments in this area. Additionally, the monthly T/ET decreased with P increasing, suggesting that black locusts could transpire water more effectively to survive under drier conditions with less P. Our study can not only improve the understanding of water budget in the reforested catchment in the semi-arid Loess Plateau but also provide the significant evidences of investigating the plant water use strategy from the point of ET partitioning. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi are an important determinant of plant performance, and conversely their community composition greatly depends on host plants and their neighbors. Understanding how the interaction of host plants and their neighbors affects AM fungal communities in afforested zones is of primary interest in forest ecology. We sampled roots and rhizosphere soils in monocultures and mixtures of black locust ( Robinia pseudoacacia ) and oriental arborvitae ( Platycladus orientalis ) to define AM fungal colonization level, spore density and communities using 454 sequencing. Neighboring oriental arborvitae only affected AM fungal community in black locust rhizosphere. For oriental arborvitae, however, growing in a mixture with black locust changed AM fungal colonization, sporulation and communities in the roots and rhizosphere. In particular, neighboring black locust modified the rhizosphere- and root-inhabiting AM fungal pool through improving soil NO 3 -N and water contents and reducing soil catalase activity, and the modification in the root AM fungal resource, especially the Glomus and Rhizophagus genera, further affected AM fungal colonization and sporulation under oriental arborvitae. All the results presented here suggest that both hosts and neighbors can largely affect AM fungal attributes mainly through changing soil nutrient levels and enzyme activity, whereas the reciprocal effects are not always symmetric. [ABSTRACT FROM AUTHOR]

Soil moisture is the foundation of ecosystem sustainability in arid and semi-arid regions, and the spatial–temporal details of soil moisture dynamics of afforested areas can benefit for land use management in water-shortage regions such as the Loess Plateau of China. In this study, spatial–temporal variations in soil moisture under Robinia pseudoacacia plantations on the Loess Plateau were analyzed. A total of 147 observations of soil moisture content (SMC) data to a depth of 500 cm soil profile were collected in 23 counties via field transect surveys and analyses of published literature. The results suggested that (1) the depth-averaged SMC was generally lower under forest sites than under cropland, both in the shallow layers and in the deep profiles. This finding implied that, compared with the native vegetation, the introduced R. pseudoacacia plantations caused intense reductions in soil moisture. (2) SMC was positively correlated with climatic factors (mean annual precipitation (MAP), mean annual temperature (MAT), and the Palmer drought severity index (PDSI)), indicating that the SMC under R. pseudoacacia plantations was highly consistent with the hydrothermal conditions at the regional scale. (3) The decreasing amplitude of SMC was linearly related to the increasing number of restoration years, especially in the areas below the 500–550 mm precipitation threshold. This finding showed that the restoration ageing sequence was an influential factor that affected the regional SMC variation in R. pseudoacacia plantations on the Loess Plateau. Our results suggest that afforestation activities should be avoided if the local total precipitation is insufficient for replenishing the soil moisture and that local tree species with a lower demand for water resources should be considered a top priority for further afforestation of the Loess Plateau. [ABSTRACT FROM AUTHOR]

The possibility of using mixtures of species in an attempt to increase biomass yield in plantations managed in short rotation coppice (SRC) has received little attention in scientific literature. The hypothesis is that mixtures of two complementary species under SRC are more productive than monocultures. The objective of this study was to compare the growth and yield of mixtures and monocultures at the tree and stand levels. A mixed plantation of Populus alba L. genotype ‘111’ (P) and the nitrogen-fixing species Robinia pseudoacacia L. genotype ‘Nyirsegi’ (R) was established in 2012 in the centre of Spain, at a density of 10,000 trees per hectare (spacing 0.4 m × 2.5 m). The experimental design included pure as well as mixtures with different proportions of the species (100P:0R; 75P:25R; 50P:50R; 25P:75R and 0P:100R) following a completely randomized block design with 64 trees per plot. There was a positive effect of the mixture 75P:25R in terms of biomass yield, achieving a total yield of 13.66 Mg ha −1  yr −1 (26.83% higher than that of the P. alba monoculture and 89.99% higher than the R. pseudoacacia monoculture), with both species achieving a greater biomass yield per tree. In the other mixture treatments there was no significant positive effect of the nitrogen (N) fixing species on the non-N-fixing species. Within-row interactions were more important than between row-interactions. There was a positive effect on the yield of R. pseudoacacia when the neighbouring trees (within a row) on both sides were P. alba , while P. alba responded better with a P. alba tree on one side and a R. pseudoacacia tree on the other. The results point to the presence of competitive reduction or facilitation as the mechanisms for increased biomass yield under certain mixture ratios, and indicates the importance of mixing within the same row rather than row-by-row, in this type of plantation. [ABSTRACT FROM AUTHOR]

Many tree species have been introduced outside their native ranges, but there is little knowledge of their niche dynamics during afforestation in different regions. Here, we test the climatic niche dynamics of a species, black locust ( Robinia pseudoacacia ), planted worldwide, between its native range (southeastern parts of United States) and four introduced ranges (North America, Europe, East Asia, and Australia). A principal component analysis method with kernel smoothers was applied to species’ occurrence densities to investigate the climatic niche centroid, breadth and unfilling/expansion between native and introduced ranges of black locust. The niche equivalency test, the niche similarity test, and the niche centroid/breadth shift tests were used to evaluate the conservatism and dynamics of realized niche of black locust. Niche equivalency/similarity tests show that only the European population has the same identical climatic niche as the native population and all introduced population in four areas are similar to native population than expected by chance with niche overlap between native and introduced areas ranging from 0.13 to 0.4. Niche centroid/breadth shift tests reveal that the niche centroid of black locust will significantly shift to warm or colder areas, as well as drier areas, and the niche breadth of black locust will significantly broaden both in water and heat gradients in the four introduced ranges separately. Niche partitioning shows that the proportion of niche unfilling occurred from 0 to 27% and that of niche expansion occurred in the 42–83% range. Our results imply that the internal causes of realized niche dynamics of black locust are mainly due to the release of biotic constraints and change in dispersal capability, but the relative importance of these factors is different among the four introduced ranges. Our study suggests that black locust conserves its climatic niche in the afforestation process allowing future studies to use ecological niche models to predict areas with suitable habitat for introduction and cultivation around the world and respond to climate change needs. [ABSTRACT FROM AUTHOR]

• Plant composition and richness differs between sweet chestnut and black locust forests. • Sweet chestnut and black locust forests have a similar stand structure. • Ammonia-oxidising archaea abundance is lower in sweet chestnut forests. • Management regime can play a relevant role in shaping chestnut forest structure. Sweet chestnut forests in Europe are impacted by management abandonment, non-native species invasions and diseases, among other factors. Understanding the effects of these factors is crucial for forecasting future biodiversity changes, as well as proposing appropriate planning and management strategies. We studied sweet chestnut (Castanea sativa Mill.) and black locust (Robinia pseudoacacia L.) dominated forests within three hilly landscapes (Euganean hills, Montello, and Berici hills) of north-eastern Italy. We surveyed 25 paired sweet chestnut and black locust dominated plots of 100 m2 representing coppice or over-aged stands. We collected and analysed data related to vascular plant composition and richness, soil physical features (moisture content, shear strength and penetration resistance), ammonia-oxidising archaea in the soil, and stand structure features. Composition of vascular plants differed significantly between the two forest types, without the influence of management regime. Soil characteristics did not change comparing forest types, management regimes and their interaction, except for soil moisture that was higher in coppice forests. Ammonia-oxidising archaea abundance was lower in sweet chestnut stands. Sweet chestnut and black locust forests have a similar stand structure. The management regime played a role in determining mean diameter, number of stems and deadwood volume. We suggest adopting a heterogeneous array of silviculture practices to achieve the highest variety of forest structures and plant composition in Mediterranean hilly landscapes, coupled with management practices aimed at black locust control. [ABSTRACT FROM AUTHOR]

Mediterranean riparian zones act as vegetation shelters for several deciduous tree species at the edge of their bioclimatic distribution, e.g. alder ( Alnus glutinosa ), black poplar ( Populus nigra ) or ash ( Fraxinus excelsior ). Current global warming and human induced disturbances may worsen their growing conditions. Under such circumstances, black locust ( Robinia pseudoacacia ) is outcompeting autochthonous tree species. Here, we provide evidences of black locust better growth and water use performance than alder and ash. We compare the temporal and spatial patterns of transpiration and the stem basal area increments of alder, black poplar, common ash and black locust, all of them co-occurring in a mixed riparian Mediterranean forest. Black locust presented the lowest transpiration values per basal area unit (4.0 mm·m −2 ·growing season −1 ). Although tree transpiration was mainly driven by energy availability instead of water, ash transpiration was constrained by water availability at soil water contents below 0.08 cm 3 ·cm −3 . Black locust was the only tree species growing all over the water availability gradient present in the study site, and it did not present any significant difference in sap flow values across this gradient. Furthermore, black locust and black poplar were the species with higher growth-based water use efficiency (5.4 g·cm −1 ·m −3 and 3.6 g·cm −1 ·m −3 , respectively); ash and alder were the less efficient ones (2.8 g·cm −1 ·m −3 and 1.9 g·cm −1 ·m −3 respectively). The good performance of black locust is relevant to understand its great successful invasion of Mediterranean riparian forests, particularly after human-induced disturbances, as forest management. [ABSTRACT FROM AUTHOR]

• An ecological comparison of near-natural forests and various tree plantations. • Near-natural forests had high taxonomic, functional, and phylogenetic diversity. • Plantations of non-native tree species performed poorly in most respects. • Among the plantations, Populus alba plantations proved to be the most valuable. • The current large extent of Pinus and Robinia plantations is ecologically undesirable. While near-natural forest stands are dramatically diminishing, monoculture tree plantations are rapidly spreading globally, including the eastern part of Central Europe. Tree plantations are regarded as simplified and species-poor ecosystems, but their functional and phylogenetic diversity and ecological value are still mostly unknown. In the present study, we investigated near-natural poplar forests and the three most common tree plantation types (native deciduous Populus alba , non-native evergreen Pinus nigra , and non-native deciduous Robinia pseudoacacia plantations) in the Kiskunság Sand Ridge, central Hungary. Our aim was to find out how different the species composition of the studied habitats is, how taxonomic, functional, and phylogenetic diversity vary among the four habitat types (i.e., near-natural forests and three types of plantations), and what the ecological value of the studied habitats is. We found that the four habitat types had significantly different species compositions. Although each habitat contained some diagnostic species, near-natural forests had the highest number of diagnostic species. While many of the diagnostic species of near-natural forests were native shrubs, tree plantations had many weeds and non-native herbs as diagnostic species. Near-natural forests had the highest per plot richness of native species and the lowest richness of non-natives. Shannon diversity, functional diversity and phylogenetic diversity were higher in the near-natural forests and two types of plantations (Populus and Pinus) compared to Robinia plantations. Based on naturalness indicator values, near-natural forests were the least degraded and Robinia plantations were the most degraded. Near-natural forests contained the most species of high conservation importance. Overall, near-natural forests proved to be much more valuable from an ecological and conservation perspective than any of the studied plantations; conservation and restoration programs should therefore focus on this type of habitat. Among the plantations, Populus alba plantations are the best substitute option in most respects, although they harbored a relatively high number of non-native species. We suggest that the native Populus alba should be preferred to non-native tree species when plantations are established. In addition, decreasing the extent of Pinus and Robinia plantations is essential on the long run if we aim to maintain the ecological integrity of the region. [ABSTRACT FROM AUTHOR]

Forest management affects stands’ vegetation structure, which influences bird communities. Since the effects of forest practices are usually more pronounced if the exotic tree species are planted, we surveyed bird communities and mapped the vegetation structure in stands of non-native broad-leaved and coniferous trees, black locust and black pine, in a central European country, the Czech Republic. By means of spatial analysis – generalized least squares models – we investigated whether the positive relationship between bird species richness in various ecological groups and vegetation heterogeneity is weakened by an assumed negative effect of the exotic tree origin. Further, we tested whether the bird community composition is more impacted by tree origin (native and non-native) than forest type (coniferous and broad-leaved) using multivariate direct gradient redundancy analyses. We found that total bird species richness, species richness of habitat specialists, ground foragers and foliage gleaners significantly increased with increasing vegetation heterogeneity after taking tree origin into account. Since there was higher vegetation heterogeneity in non-native tree stands, we suggest that the potential benefits of this higher heterogeneity were suppressed by some other (unmeasured) characteristics (e.g. limited food supply) of these stands, which might also be the reason for lower richness of habitat specialists and canopy foragers. The most important gradient in the bird community composition was from broad-leaved to coniferous stands irrespective of tree origin. The effect of tree origin was expressed as the secondary gradient, albeit still significant. It seems that the birds’ adaptations to different leaf morphology play more important role in structuring bird communities than the influence of tree origin. Our results indicate that the forest management should focus on the increase of the vegetation heterogeneity in native tree stands to maximize total bird species richness, and on avoiding establishment of non-native tree plantations to prevent loss of habitat specialist birds. [ABSTRACT FROM AUTHOR]

Revegetation is one of the primary management approaches for solving the problems caused by severe soil erosion worldwide. Robinia pseudoacacia was considered a promising tree for afforestation in the highly eroded region of the Loess Plateau due to its fast growth and ability to fix atmospheric nitrogen. However, its beneficial role protecting soils from erosion has been now questioned and several negative effects on soil and vegetation have been described. In this study we aimed to analyze the effects of R. pseudoacacia plantation on plant community composition and dynamics through the effects that R. pseudoacacia has on light, soil fertility and soil water availability. We used a chronosequence from 10–40-year-old plantations and compared the environmental and vegetation characteristics of that areas with that of natural control areas with similar age. The results showed that R. pseudoacacia plantations reached maturity around 30 years and then declined in density and canopy cover. We also found that soil nutrients and moisture at the superficial soil layer improved with age until maturity of plantations, but photosynthetically active radiation at the ground level and soil moisture at deeper soil layers decreased with maturity in relation to control conditions. Plots with R. pseudoacacia of all ages had higher cover values, lower number of species but higher β-diversity values than control conditions and they also differed in species composition. These differences in structure and species composition were related to the fertilizer effect of R. pseudoacacia that favored colonization by weeds and ruderal species, and to the light interception by the canopy of trees that exclude light-demanding species, most of them perennial herbaceous species which were the dominant species in control conditions. [ABSTRACT FROM AUTHOR]

• Riparian forests are particularly vulnerable to non-native tree invasion. • Robinia pseudoacacia and Ailanthus altissima are by far the most frequent invaders. • Eucalyptus camaldulensis, Populus × canadensis and Ulmus pumila have spread recently. • Potentially invasible forests can provide information on the future threat posed by non-native trees. • Tailored strategies are needed for the management of non-native tree species. Many forest tree species have been moved outside their native range to provide goods and services elsewhere, but some of them have become invasive, causing negative impacts on biodiversity and human activities. The assessment and knowledge on the degree and scale to which forest ecosystems are invaded by non-native trees is of paramount importance for tailored policies and strategies aiming at forest conservation. By analyzing main databases and literature and applying a four-level scale of invasion (not currently invaded and with low invasibility; potentially invasible; moderately invaded; massively invaded), we assessed the current and potential occurrence of twenty-five invasive non-native trees across forest ecosystems in Italy. Vulnerability to invasion substantially differed across forest categories, with riparian forests being particularly vulnerable to invasion. Acacia dealbata , Juglans nigra , Populus × canadensis and Prunus laurocerasus invaded a relatively small number of forest categories but showed their potential to widen their impact on others. Furthermore, some non-native species showed a recent increase of their invasive status in Italy. This study identified the Italian forest categories and non-native tree species that deserve primary attention, and can support proper management and allocation of funding to protect forests from the spread of invasive tree species. [ABSTRACT FROM AUTHOR]

[Display omitted] • The production and quality of the leaf-litter are closely linked to the genotype. • Black locust and willow were the ones with the highest decomposition rate. • Poplar and plane tree showed the greatest retranslocation as a conservation strategy. • Species with high decomposition rate are more recommended to preserve soil fertility. • An advantageous strategy could be to mix species with different decomposition dynamics. Quantifying leaf-litter and the potential contribution of essential nutrients to the soil is key to guaranteeing the sustainability of forest systems, especially in plantations under short rotation coppice, insofar as it can condition crop management such as the requirement for nutritional amendments. Nutrient cycling is dependent on production as well as litter decomposition, so to compare the different strategies of the species in nutrient recycling it is important not only to determine the quality and quantity of leaf litter, but also the decomposition rate dynamics and the consequent potential incorporation of organic matter and nutrients into the soil. Therefore, this work aims to quantify and analyze the dynamics of leaf-litter as well as the retranslocation rate, to assess the decomposition rate of the foliar biomass and its nutrient concentrations, and finally, to assess the evolution of leaf-litter quality. For these purposes, eight genotypes were considered in this study: Populus deltoides ('Baldo'), Populus × canadensis ('Ballottino', 'I-214′, 'Orion' and 'Oudenberg'); Platanus × hispanica ('Girona'), Salix matsudana × Salix spp. ('Levante') and Robinia pseudoacacia ('Nyirsegi'). The plantation was established in central Spain with a density of 10,000 cuttings ha−1. Three rotations of 3 years each were applied, this study being carried out during the first growing season of the second rotation. Although the leaf fall dynamics were similar among the different species, the production and quality of the leaf-litter were highly species specific. Different strategies were identified; greater retranslocation of N and P being found in poplar, plane tree or only of P in the case of black locust as a conservation strategy, although lower retranslocation of all nutrients was observed in willow, which means that the leaf litter of the latter is very rich in nutrients. While willow, black locust or even some genotypes of poplar are capable of releasing many of the nutrients to the soil during decomposition, plane tree released a smaller variety of nutrients, N, P and Mg being immobilized in the leaf-litter. From the perspective of conserving the soil fertility resulting from the decomposition of leaf-litter, the plantations of species with the highest decomposition rates, such as black locust and willow, were found to be the most recommendable. However, the immobilization of some nutrients in the leaf-litter during the decomposition process could satisfy the nutritional requirements of these species in the medium and long term, thus an advantageous strategy could be to mix species with different decomposition dynamics. [ABSTRACT FROM AUTHOR]

Abstract: The non-native tree species Black Locust (Robinia pseudoacacia L.) from N America and Tree of Heaven (Ailanthus altissima (Mill.) Swingle) from E Asia are invading both anthropogenic and near-natural habitats throughout Europe. So far, few studies have focused on their invasion into forests and none has addressed the influence of coppice management, which is characterized through regular clear-cuts. To retrace the invasion during the last 50years, we studied the abundance in the canopy as well as the natural regeneration of these species in the coppice forest of Gargazon (South Tyrol, Northern Italy), which was ideal due to its patchy mosaic of different forest age (time since last coppicing). We analyzed which factors favor the presence and abundance of A. altissima and R. pseudoacacia regeneration. Tree saplings were sampled on 113 plots each measuring 7m2 in a total study area of 25.5hectares. On each plot, the following environmental variables were recorded: canopy cover per species, total herb layer cover, distance to clearing, stone cover, slope, and aspect. Soil moisture was derived from herbaceous indicator species. Hurdle models were used for data analysis to account for the zero-inflated data structure. The results showed that R. pseudoacacia has established earlier in the studied forest than A. altissima, but A. altissima has been spreading with higher speed during the last 30years. Our study exemplifies the invasion of both species synchronously to the coppice cycle, that means they colonize fresh clear-cuts, establish, and remain. We conclude that the currently applied coppice management, which consists of repeated clear cuttings each 20–30years, favors the spread of both invasive species. Thus, an adaptation of the management system is needed to avoid further invasion. [Copyright &y& Elsevier]

Abstract: Black locust (Robinia pseudoacacia L.) is a widespread alien tree species commonly thought to influence plant assemblages. The aim of this study was to compare the plant diversity between black locust and native recent secondary stands within the European Mediterranean Mountains environmental zone. Spontaneous reforestation was detected by comparing historical aerial photographs and the most recent images. Distributed throughout a 2700km2 hilly and piedmont area, 32 black locust and 32 paired native stands were selected and all vascular plant species were surveyed in a 100m2 area. Analyses of the α and β-diversity were performed separately for six identified plant groups. Despite a clear difference in the tree diversity between the black locust and native recent secondary stands and a homogenisation of the tree layer by the black locust stands, we found only inconsistent hints for homogenisation of the ground-layer vegetation by the black locust stands. There is no evidence to suggest that the presence of black locust in recent secondary stands plays a major role in shaping the diversity of the understory plant groups compared to native stands. [Copyright &y& Elsevier]

Abstract: Short rotation woody biofuel plantations on reclaimed surface mines in Appalachia can diversify domestic energy supplies and facilitate the reforestation of these disturbed lands. This study examined growth, survival, biomass accumulation and allocation, and nitrogen concentrations following two growing seasons in American sycamore (Platanus occidentalis L.) and black locust (Robinia pseudoacacia L.) seedlings receiving irrigation, granular fertilization, and irrigation+fertilization compared with untreated controls. Fertilization increased basal diameter, height, and stem mass of American sycamore following two growing seasons. Increased stem production was attributed to accelerated development and not shifts in biomass allocation due to treatment. Irrigation and irrigation+fertilization treatments did not enhance growth or biomass accumulation of American sycamore. Similarly, black locust basal diameter, height, and stem mass did not differ among the treatments. Browse surveys showed that more than 76% of black locust seedlings experienced arrested or retrogressed growth due to browse; less than 3% of American sycamores were browsed. This intensive browse by ungulates, likely including reintroduced elk, may have affected growth differences among species and confounded the effects of treatments on black locust. Survival was unaffected by treatment in both species, but mean survival was greatest in American sycamore (80%) compared to black locust (58%). Per tree total nitrogen uptake was highest in fertilized American sycamore (7.9g) and lowest in irrigated American sycamore (0.9g). The results of our study suggest that granular fertilizer applications can accelerate seedling growth on reclaimed surface mines in the Appalachian region. [ABSTRACT FROM AUTHOR]

Abstract: This study examined the factors that influence the size of a soil seed bank in Robinia pseudoacacia stands. We proposed two hypotheses: the amount of buried seeds of R. pseudoacacia is proportional to stand biomass rather than stand age, and apicultural utilization influences the size of the soil seed bank. R. pseudoacacia generally produces seeds with various degrees of physical dormancy. In addition, this tree is short-lived, and fecundity declines after 30–40 years in relation to tree vigor. However, R. pseudoacacia is intensively used in apiculture as an important honey source, and supply of honeybees by beekeepers could influence seed crops. We investigated 25 plantations in Hokkaido (Central, Hidaka, and Oshima) and in Nagano, Japan, where many naturally regenerated R. pseudoacacia stands occur. We found great variation in the size of the soil seed bank among stands, ranging from 13,757 to 6.4seedsm−2 per plot. A generalized linear mixed model revealed that both basal area (BARp) and apicultural utilization best explained the size of the soil seed bank. Both the positive effect of BARp and small contribution of stand age to the model implied that the soil seed bank is transitory, and will not persist for very long time. The large contribution of apicultural utilization to the size of the soil seed bank implied pollinator limitation under natural conditions. R. pseudoacacia often has large flower crops, and native pollinators can not keep up with the demand for pollination. Thus, the supply of honeybees by beekeepers should improve the pollination success of R. pseudoacacia. From these results, we conclude that we must consider stand history with respect to apicultural utilization if the land is harvested or a stand declines. [Copyright &y& Elsevier]

Abstract: On the Loess Plateau, China, several planted tree species such as Populus hopeinsis and Robinia pseudoacacia suffer occasional diebacks in the top shoots, reducing growth rates after maturation. However, this does not usually occur in other species, e.g., Ulmus pumila and Zizyphus jujuba. We compared stable carbon isotope ratios (δ 13C) as indicators of leaf water-use efficiency (WUE), leaf mass per unit area (LMA), and leaf area- and mass-based nitrogen content (Narea and Nmass) by tree height (1, 5, and 10m) in P. hopeinsis, R. pseudoacacia, U. pumila, and Z. jujuba. In P. hopeinsis and R. pseudoacacia, leaf δ 13C and Narea were significantly lower in 10-m trees than in 1-m saplings, indicating that leaf WUE and photosynthetic rates of both species decreased with tree height. In contrast, δ 13C in Z. jujuba varied little with tree height. The δ 13C of 10-m-tall U. pumila trees was significantly higher than that of 1-m plants, demonstrating an increase in WUE with tree height. Decreasing WUE, leaf Narea, and Nmass with height increases in P. hopeinsis and R. pseudoacacia may be related to water and nutrient limitations for these species in semiarid regions. In contrast, stable or increasing δ 13C with tree height in U. pumila and Z. jujuba may account (to some extent) for successful production of these species under identical environmental conditions. Diameter growth rate also decreased with maturity in P. hopeinsis and R. pseudoacacia, but increased or was stable for U. pumila and Z. jujuba. The differences in leaf WUE and LMA among species with tree maturity may be related to species’ growth patterns and susceptibility to drought stress, and are likely to be important new criteria for plantation species selection on the Loess Plateau. [Copyright &y& Elsevier]

• Afforestation has occurred over different periods in Central Anatolian arid lands. • Survival and growth rates of tree species have changed through afforestation. • Forest floor organic matter had accumulated as stands aged. • Soil carbon and nitrogen content had increased as stands aged. Restoration of degraded lands is among the major challenges in Arid and semi-arid ecosystems. Therefore, in many regions where arid and semi-arid climates prevail, afforestation studies are carried out for restoration purposes. This study evaluated long-term afforestation practices in terms of ecosystem restoration in the arid lands of Central Anatolia, Turkey. For the study, sample afforestation sites of different ages were chosen in the Tuz Gölü-Konya basin. Species in the sites included black pine (Pinus nigra), Russian olive (Elaeagnus angustifolia), sweet almond (Prunus dulcis), black locust (Robinia pseudoacacia), narrow-leaved ash (Fraxinus angustifolia), and mahaleb cherry (Prunus mahalep). For each sampling area, the survival rates, height, and diameter values of species were recorded. Litter on the forest floor was sampled and then representative soil pits were dug at each site to sample soil from different layers (30, 60, 90, and 120-cm deep) of the profile. Bulk density, texture, lime content, pH, salinity, cation exchange capacity (CEC), and carbon (C) and nitrogen (N) concentration were determined for each soil sample. Approximately 2/3 of the black pine seedlings had died in the first 8–10 years of afforestation. The mortality rate in almond and mahaleb seedlings was approximately 20%. After 25–27 years of afforestation, 1/3 and 2/3 of the initial almond and Russian olive seedlings were lost, respectively. The mortality rate for other species was about 80% for the same period. Black pine had reached over 6.5 m, increasing its height by about 11-fold over the last 10–25 years. In the same period, the increase in the height of black locust was 2.8-fold, almond 2.6-fold, and ash 2.5-fold. The least height growth (1.7-fold) for this period was recorded for mahaleb. The amount of litter had increased 3- and 5-fold, at 15–17 years and 25–27 years of plantation age, respectively, compared to its increase in the open control site. After 15 years from planting, soil nitrogen (N) concentration at the first 30-cm depth had increased by about 1/3 compared to the open area. At the same depth, the soil pH value had decreased by 0.15 units after 25–27 years compared to the rest of the profile. These data implied that soil restoration had been initiated at all sites. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the results of the effects of clonal selection on biomass production and quality in monophylla black locust (Robinia pseudoacacia var. monophylla Carr.) were studied. The genetic material included seedlings of open pollinated families, ramets of selected clones within them and seedlings of common black locust (Robinia pseudoacacia L.) as a control. Both seedlings and ramets were planted in the field in April 1994. At the end of the first and the subsequent growing seasons (1994–2002) all of them were cut at 20cm aboveground. Measurements were done at the end of October–beginning of November and included height and oven-dry weight of saplings, stem number, leaf/stem ratio of oven-dry weight and length of the longest thorn. It was found that height and oven-dry weight were increased in the first three years but they declined thereafter both in clones and families. Overall, however, clones were superior to families. Stem number was increased with age more in families than in clones. Leaf/stem ratio of oven-dry weight declined with time but clones were superior to families. Thorn length, finally, increased over the years but clones had significantly lower values than families. The results showed that the most productive clones were also better in quality characteristics (leaf/stem ratio of oven-dry weight and thorn length) than most families and the control. It is concluded that clonal selection can result in significant increase of biomass quantity and improvement of its quality. [Copyright &y& Elsevier]

Abstract: Litterfall production, the amount of organic matter on the forest floor, and litter decomposition rates were studied in an exotic nitrogen (N)-fixing black locust (Robinia pseudoacacia) plantation and an indigenous non-N-fixing oak (Quercus liaotungensis) forest near Yan’an, on the Loess Plateau, China. The chemical composition of litterfall and soil was also examined. Litterfall production was similar in the two forests; however, the amount of N in litterfall was greater in the black locust plantation than in the oak forest because of the high N concentration of black locust leaves. The decomposition rate of black locust leaves was higher than that of oak leaves, most likely because of the higher N content of black locust leaves. These results suggested that N cycling was greater and faster in the black locust plantation than in the oak forest. However, faster decomposition caused the disappearance of the organic layer from the forest floor in the black locust plantation. Furthermore, despite greater N cycling in the black locust plantation, the soil N content was lower than in the oak forest. Our results indicated that the black locust plantation might be more susceptible to soil erosion than the oak forest. In addition, our study suggested that the black locust plantation had advantages in short-term N uptake, growth, and N cycling; however, it had disadvantages in soil development and regeneration and sustainable land management. [Copyright &y& Elsevier]

Black locust (Robinia pseudoacacia L.) was introduced to South Korea from North America in the 19th Century and was heavily used in the 1960s for reforestation of denuded mountains after the extensive deforestation during the Japanese occupation periods and the Korean War. Nationwide distribution of black locust tended to positively correlate with human population size and/or density of the administrative districts considered. Results from field survey on the representative vegetation types, Quercus acutissima and Q. mongolica communities in lowland and upland, respectively, show that black locust have invaded other vegetation beyond originally planted zones in lowland but not the upland vegetation. Black locust occurs from the bases to summits of mountains in the urban centers, whereas its range is restricted to mountain bases in urban outskirts and rural areas. Although native oaks (Quercus spp.) are usually succeeding black locust colonies, changes to native vegetation are often interrupted by frequent disturbance by human activities, as evident from persistent sprouts and expansions of black locust suckers in the disturbed areas, such as urban center and rural areas. Responses of the black locust plantation in terms of stand dynamics to different disturbance intensities also reflected such trends. Our results suggest a correlation between disturbance regimes and occurrence of black locusts. We recommend incorporating this correlation to the management plan for control of black locust. [Copyright &y& Elsevier]

• C and N stocks in cropland following R. pseudoacacia afforestation were quantified by a national meta-analysis. • Afforestation with R. pseudoacacia on cropland generally increased C and N stocks. • Changes in C and N stocks varied with plantation attribute, climate, topography, soil. Afforestation made great contributions to ecological benefits across China. Robinia pseudoacacia is widely used in the Grain-for-Green Program. The responses of soil organic carbon (SOC) and soil total nitrogen (STN) to afforestation with R. pseudoacacia on cropland depend on plantation attributes, climatic factors, topographic features, and edaphic variables, thus making a synthesis of these studies necessary for understanding the magnitude and direction of SOC and STN to afforestation and the associated regulating factors. A meta-analysis was employed by compiling data of 1202 paired observations from 94 peer-reviewed publications to depict potential mechanisms of change in SOC and STN stocks following afforestation with R. pseudoacacia on cropland. Afforestation with R. pseudoacacia on cropland, on average, significantly and positively increased SOC and STN stocks. The changes in SOC and STN stocks increased with plantation age and altitude, but decreased with mean annual temperature, slope gradients, soil depth, soil clay content, initial SOC content and initial STN content. Greater accumulation rates of SOC and STN stocks after afforestation were detected in middle canopy density (0.6–0.8) and middle mean annual precipitation (450–550 mm). Among four kinds of biotic and abiotic factors, plantation attributes made greatest contributes to the variance in the response size of SOC and STN stocks. In particular, plantation age was the most essential variable on the response size of SOC and STN stocks. These results indicated that SOC and STN stocks following afforestation with R. pseudoacacia on cropland could be enhanced through plantation management practices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four bioclimatic clusters determine black locust distribution in Europe. • The eastern cluster overlaps with climatically suitable area in current and future distribution. • The black locust highlighted spatially and temporally variable climate sensitivity. • The plasticity in secondary growth may increase the black locust's invasive potential. As a consequence of native tree species decline and distribution range contraction in Europe, acclimation of the non-native tree species at the edge of their distribution is gaining importance. Although non-native tree species may provide sustainable ecosystem services, as a potentially invasive species they may be a threat to local ecosystems as well. In Europe, black locust (Robinia pseudoacacia) a non-native species, seems to meet the condition of acclimation as a multi-generational process. The acclimatization, however, may have consequences not only for growth performance but also for the species' invasive potential. This study investigates the spatiotemporal pattern of secondary growth and climate sensitivity among six black locust stands along continentality gradient in Eastern Europe with the respect to bioclimatic conditions of the species distribution in Europe. Despite comparable bioclimatic conditions, climate sensitivity of black locust stands is highly variable, both temporally and spatially. The winter and spring temperatures are a key climatic driver of the growth pattern in southern and western Poland. Growth response to previous winter and current summer precipitation distinguished stands in western and eastern Poland. A significant increase in the mean annual temperature during the last 70 years likely triggered temporal instability of the black locusts' climate signal. In general, drought conditions were found to be the main limiting factor at the edge sites within the black locust gradient. Thus, the climate sensitivity of black locust stands reflects rather site-specific microclimatic conditions then bioclimatically-based clustering pattern. Despite climate-related limiting factors, black locust seems to be characterized by high potential for acclimatization to Eastern European climatic conditions, suggesting high invasive potential. Thus, the replacement of native species by black locust or the conversion of local habitats into monocultures for biomass production should not be recommended, while species management should follow proactive measures to reduce the risk of uncontrolled spread of the species. Divergent growth reaction of black locust stands implies high plasticity of secondary growth and thus high probability of acclimatization to future climate. Given the expected range expansion to the East in Europe, we call for expanding dendroclimatic studies to the areas of future species expansion in order to test its climatic and edaphic limitations. This seems to be crucial for formulating non-native species management strategies in line with sustainable forestry, preventing the uncontrolled expansion of the species that threatens vulnerable habitats. [ABSTRACT FROM AUTHOR]

• Soil water carrying capacity was prerequisite to guide stand density regulation. • With stand density regulation, forest structure was complex. • Density regulation may increase soil water in topsoil and decrease it in deep soil. • The drivers influencing soil moisture varied before and after density regulation. • The optimum stand density ranges were initially hypothesized and then determined. How do forests respond to management practices designed to improve their ecological benefits? Clarifying how forest structure and soil moisture vary with the regulation of stand density can help us answer the question. Appropriate maintenance of stand density via thinning or complementary planting can optimize stand structure and increase soil moisture in low-efficiency stands. In this study, four 40 m × 40 m sample plots (each divided into four 20 m × 20 m subplots) were established in plantations of Robinia pseudoacacia L. (RP) and likewise those of Pinus tabulaeformis Carr. (PT) plantations. The recommended stand densities below the soil water carrying capacity for vegetation were set up, ranging from 1500 to 1800 plants·ha−1 for RP and from 1100 to 1600 plants·ha−1 for PT. Across the three years since stand density regulation practices were implemented, the significant dominant factors varied. Their corresponding contribution rates (CRs) were as follows: stand density, 0.766 (RP) and 0.857 (PT); canopy density, 0.814 (RP); leaf area index, 0.822 (PT); Pielou's index of herbs, 0.908 (PT); and water retention of litter, 0.932 (PT). Furthermore, soil infiltration (0.861, RP) had significant effects on shallow and deep soil water. With consideration of the above drivers, the optimum stand density range should be further determined in future experiments. These results can provide guidance to forest managers on how to remain within the carrying capacity of stands and their water resources, which is critical for constructing high-quality ecological systems on the Loess Plateau. [ABSTRACT FROM AUTHOR]

• Revegetation particularly the planted forest severely depleted the deep soil water. • Platycladus orientalis was better able to maintain the deep soil water status. • The soil water status worsened with time after restoration especially after 20 years. • Soil water depletion even increased in areas of high rainfall compared to drier zones. • Natural restoration was a better option in maintaining deep soil water status. Revegetation-induced water deficits in the deep soil (>100 cm) on the arid and semiarid Loess Plateau threaten the sustainability of its ecosystems. However, quantifying changes in deep-soil water status at the regional scale remains challenging. This study represents the first attempt to integrate meta -analysis with the digitization of map data from previous research to evaluate the effects of revegetation on the deep soil water status. A total of 4906 observations from 94 peer-reviewed publications related to soil water changes to a depth of 500 cm in planted forests, planted shrublands, natural grasslands and croplands were synthesized, and two regional-scale evaluation criteria, the stable field capacity (SFC) and the permanent wilting point (PWP), were developed by digitizing the map data. The results indicated that (1) compared with cropland, revegetation more severely depleted the deep soil water availability, and planted forest revegetation resulted in the most serious depletion; (2) the extent of soil water changes was influenced significantly by the tree species planted; Platycladus orientalis was better able to maintain the deep soil water availability than Robinia pseudoacacia and Pinus tabuliformis ; (3) the soil water status worsened with time after restoration, particularly at 20 years after restoration; (4) contrary to expectations, deep soil water depletion in forests and shrublands even increased in areas of high rainfall zones (>550 mm) compared to drier zones.; and (5) natural restoration (i.e., grasslands) was a better option than revegetation due to the resultant higher, more stable soil water availability. These results indicate that changes in deep soil water availability must be considered when planning revegetation initiatives. [ABSTRACT FROM AUTHOR]

[Display omitted] • Root nutrient resorption showed that first decreased and then increased with stand age. • Rhizosphere soil microbial composition responded positively to soil nutrient availability. • Nutrient utilization of the rhizosphere soil microbes negatively drives root nutrient resorption. Understanding root nutrient resorption strategies and their drivers is essential to explore plant nutrient acquisition strategies in restored ecosystems. However, the interaction between root nutrient resorption and the nutrient utilization of rhizosphere soil microorganisms in restored ecosystems has yet to be determined. In this study, we investigated plant fine roots and rhizosphere soils in Robinia pseudoacacia plantations at four stages of forest succession (14, 20, 30, and 45 years of age) on the Loess Plateau in China. We studied the characteristics of root nitrogen and phosphorus resorption efficiencies (NRE and PRE) at different recovery stages and analyzed the relationships among nutrient resorption and rhizosphere soil variables (nutrients and microbial communities). We detected a tendency of an initial reduction and subsequent increase in root NRE and PRE with stand age (the lowest value at 30-y sites), whereas the nutrient contents of rhizosphere soil increased with stand age, and soil available nutrients initially increased and then declined. The diversity of rhizosphere soil microorganisms also showed an initial increase and subsequent decline. Proteobacteria were considered to be at an advantage during the nutrient-rich stage of restoration (30-y sites), whereas Acidobacteria were found to be dominant during the low-nutrient restoration stage (14-y sites). Furthermore, the microbial nutrient utilization ratios of soil microbial biomass carbon: soil organic carbon, microbial biomass nitrogen: soil total nitrogen, and microbial biomass phosphorus: soil total phosphorus also showed an initial increase and then decreased (with peaks at the 30-y sites). Redundancy analysis indicated that the nutrient contents of rhizosphere soil were significantly related to microbial communities and correlation analysis revealed that microbial nutrient-use efficiencies were significantly related to rhizosphere soil nutrient contents and the dominant microbial communities. We also detected a significant negative correlation between root nutrient resorption and microbial nutrient utilization. Partial least squares path modeling revealed that forest restoration influences the contents of nutrients in rhizosphere soil and the composition of microbial communities, whereas microbial biomass and nutrient utilization efficiency were shown to have a negative effect on root resorption efficiency. Based on our findings, we propose that the highly conservative nutrient utilization strategies of the rhizosphere soil microbial community may negatively drive root nutrient resorption strategies during the succession of R. pseudoacacia. [ABSTRACT FROM AUTHOR]

• Nitrogen fixation by leguminous Robinia pseudoacacia was not obvious. • Soil organic carbons stocks in the 16- and 49-year-old plantations were similar. • Soil organic carbon was negatively correlated with soil pH. • Robinia pseudoacacia plantations showed soil acidification across entire profiles. Over the past several decades, a vegetation restoration project has been conducted in the southeastern Loess Plateau of China by converting cropland into forest plantations to combat soil erosion. However, the effects of land use change on soil fertility are poorly documented. Here, we assessed soil chemical properties in areas of the southeastern Loess Plateau following afforestation of cropland with Robinia pseudoacacia plantations that had been established for 16 years and 49 years, a 49-year-old naturally restored forest, and adjacent cropland. We found that the effect of afforestation on soil organic carbon and total nitrogen mainly occurred at shallow depths. Soil organic carbon and total nitrogen concentrations in the topsoil of both 49-year-old forests were significantly higher than those in cropland. However, the highest total phosphorus concentrations were observed in the topsoil of cropland due to the application of fertilizer. The nitrogen-fixing effect of leguminous Robinia pseudoacacia was not obvious through comparisons of soil total nitrogen within 49-year-old naturally restored and planted forests. Our results indicate that both natural restoration and planting can increase soil organic carbon stocks, but that the increase after 16 years is slight. In this experiment, we found that soil organic carbon concentrations were negatively correlated with soil pH for all four land use patterns, and that the strength of the correlation increased with time since restoration. In contrast to cropland and naturally restored forest, plantations of both ages showed soil acidification across their entire profiles. This may be due to the root exudate and rhizosphere environment created by R. pseudoacacia. These results provide important insights about the impacts of ecological restoration on soil chemical properties in the Loess Plateau and elsewhere. [ABSTRACT FROM AUTHOR]

• Soil microarthropod density was higher in non-native stands than in native stands. • Feeding activity was greatest in non-native Populus × canadensis (PC) stands. • Effects of non-native plantations on feeding activity depended on tree identity. • PC plantations promoted feeding activity via affecting soil microarthropod density. Afforestation with non-native tree species is regarded as a rapid management strategy to rehabilitate degraded ecosystems. Despite the well-documented effects of non-native forest plantations (NNFPs) on plant diversity, relatively few studies have explored the effects of NNFPs on soil fauna and ecosystem processes mediated by them. Soil microarthropods are key contributors to decomposition and soil biogeochemical cycling processes, and their feeding activity has been recognized as an important functional indicator in soil. Here, we investigated the soil microarthropod diversity (mites and springtails) and their feeding activity in non-native Robinia pseudoacacia (RP), Populus × canadensis (PC) and native Armeniaca sibirica (AS) forests on the Chinese Loess Plateau. We also investigated the soil properties and understory plant diversity to explore the potential links among these variables and feeding activity by using structural equation modeling (SEM). The abundance of soil microarthropods was significantly greater in the non-native RP and PC plantations than in the native AS plantations. The feeding activity in the RP and AS plantations was at a similar level to each other and was significantly lower than that in the PC plantations. Results from SEM showed that non-native PC rather than RP plantations significantly increased feeding activity by raising the abundance of mites and/or springtails. The results demonstrate that the effects of NNFPs on feeding activity depend on tree identity, and suggest that non-native PC rather than RP plantations contribute to enhancing soil ecosystem functioning, which provide guidance for non-native tree selection on the Loess Plateau. [ABSTRACT FROM AUTHOR]

• SOC significantly increase and reach a peak at the stand ages of 30–40 years. • N contents in leaf and litter increased with the stand ages. • Robinia pseudoacacia can enhance C and N contents in soils and microbes in the first 30 years. • Robinia pseudoacacia was P-limited and this limitation become increasing along with the forest stand ages. Ecological stoichiometry in plants and soils is an important indicator of element cycling and ecosystem stability that has been used to indicate nutrient limitation. However, the stoichiometric responses of plants and soils along a chronosequence on the Loess Plateau of China has not been studied. In this study, we chose four stand ages (5–10 years old, YF; 10–20 years old, NF; 30 years old, MF; 40–50 years old, OF) of Robinia pseudoacacia and abandoned land (AC) as research subjects to illustrate the C:N:P stoichiometry interactions among soils, plant tissues (green leaves, leaf litter, and roots), and soil microbes. The results demonstrated that the soil organic C, total N, soil microbial biomass C (MBC), microbial biomass N (MBN), and microbial biomass P (MBP) contents increased significantly with afforestation age and reached a peak in the OF stand. The soil C:N ratio showed a significant increase from 9.2 to 13.1, while no significant differences were observed in the soil MBC:MBN ratios. Compared with the R. pseudoacacia forests, AC had the lowest soil C:N, N:P, and C:P ratios. Forest stand age had different influences on the C, N, and P contents in leaves, leaf litter, and fine roots. The most obvious trends were that the N contents in leaves and litter increased with stand age, indicating that old forests could accumulate more N in their leaves and litter. The leaf N:P ratio increased from 16 to 20 along the chronosequence, which demonstrated that P was the limiting element for the growth of R. pseudoacacia plantations on the Loess Plateau. The P demand increased with stand age. Therefore, our results indicated that R. pseudoacacia plantations enhance the C and N contents in soils and microbes in the first 30 years of growth and show an increasing demand for P over time. Therefore, attention should be paid to the application of phosphate fertilizer for the management of R. pseudoacacia plantations. [ABSTRACT FROM AUTHOR]

• In plantation forests of forest-steppe species richness of forest specialist herbs is very low. • Site preparationdecreases stronger their richness than planting alien trees. • With site preparation alien plants appear and establish permanently in plantations. • Continuity of natural oak forests is the key to preserve richness of specialists. In forestry, several types of management practices are used, which have significant effects on species richness and composition. A number of studies concerning the effect of management on biodiversity have been conducted in the tropical and temperate forest zones. This topic is less studied in the forest steppe biome, where the reestablishment of plants from the surrounding patches is more limited than in the forest biome. Most studies compare alien plantations with seminatural forests. However, the effects of dominant tree species is mixed with the effect of the site preparation and site history in such comparisons, due to intensive site preparation in case of forest plantations. In this study, we separate the effect of these management elements. We examined the potential of currently used forestry protocol in preserving the plant biodiversity of the forest herb layer in the Pannonian sand forest steppe using 266 forest plots from the Kiskunság sand region in Hungary. The total richness and richness of habitat preference groups (forest specialists, grassland specialists, native weeds, and aliens) were compared in natural and plantation forests of different tree species to explore the effects of dominant tree species and site preparation on the species composition. Factors determining the richness of forest specialists in plantations were analyzed by fitting a regression tree, and the habitat preference of these species was described by their fidelity to the forest types. Our results show that total species richness is less sensitive to management than the richness of some species groups with a specific habitat preference. Forest specialist species can survive almost only in continuous seminatural oak forests, that is, in forests that are continuously present and do not undergo any site preparation. They are completely missing from young plantations, most likely because site preparation completely removes them. Their limited recolonization is possible only in plantations of native trees in landscapes where seminatural oak forests have been continuously present. Even under these conditions, only half of the forest specialist species are able to recolonize in the plantations. Grassland specialists, on the other hand, are present in every forest type but with low richness. Site preparation acts as a colonization window for weeds and aliens. However, while the richness of weeds is the highest in young plantations and decreases in established plantations, probably due to the canopy closing, the richness of aliens is the same in both young and established plantations. Considering our results, the current forestry protocol is hardly suitable for maintaining the plant biodiversity of forests in the forest steppe zone, therefore, management practices should be changed to focus more on the conservation of these endangered habitats. [ABSTRACT FROM AUTHOR]

• Nutrient resorption strategies were significantly associated with leaf lifespan and N-fixation capacity of tree species. • Plant growth rates were likely to be regulated by nutrient resorption strategies. • Soil moisture and available phosphorus were the primary drivers of nutrient resorption strategies. • Nutrient resorption was driven synchronously by the N and P in plants and soil. Nutrient resorption by senesced leaves is an important mechanism for the preservation of plant nutrients. However, our understanding of nutrient resorption patterns and drivers of plantations in Loess Plateau is limited. In this study, four main tree species (Robinia pseudoacacia [RP], Pinus tabuliformis [PT], Armeniaca sibirica [AS], and Caragana korshinskii [CK]) were compared in plantations on the Loess Plateau. We explored the relationships among nitrogen resorption efficiency (NRE), phosphorus resorption efficiency (PRE), plant nutrients (green leaf total nitrogen [TNgr] and total phosphorus [TPgr]), stand ages, growth rates (height growth rate [HGR] and diameter growth rate [DGR]), soil nutrients (soil total nitrogen [STN] and total phosphorus [STP]), available nutrients (soil inorganic nitrogen [SIN] and available phosphorus [SAP]), soil water content (SWC), and stoichiometries. We found that significant differences in nutrient resorption efficiencies among different afforested tree species. And the increase of N:P ratios of leaves and soil, and the decrease of SAP enhanced P-limited. Furthermore, the resorption efficiencies of different species differed in response to nutrients, stoichiometries, and plant growth. PRE was significantly negatively correlated with the DGR of deciduous species; however, NRE of N-fixing plant was positively correlated with plant growth rates. And the contributions of SWC and SAP were greater for nutrient resorption compared to other variables. The STN:STP and SIN:SAP were significantly correlated with leaf N:P, NRE, PRE, and PRE: NRE. Overall, plant growth rates may be regulated by absorption strategies due to leaf lifespan and N-fixing capacity of tree species. Resorption efficiencies were significantly correlated with SWC and SAP showed that soil moisture and available phosphorus were the primary drivers of nutrient resorption strategies. The association of PRE: NRE with N:P ratios indicated that nutrient resorption was driven by the coupling effect of N and P in plants and soil. [ABSTRACT FROM AUTHOR]

• 1. Pinus Sylvestris var. mongolica is more conducive to increasing the soil organic carbon and available phosphorus contents. • 2. Pinus tabuliformis is more beneficial for increasing the total nitrogen content. • 3. Robinia pseudoacacia and Caragana korshinskii are more effective for increasing available potassium content. Vegetation restoration in arid and semi-arid areas plays an extremely important role in improving the ecological environment and preventing soil erosion. The construction of the Three-North Shelter Forest (SF) in Northwestern China commenced several decades ago to increase forest productivity, improve soil fertility, and achieve better ecological benefits in arid and semi-arid zone. To date, many studies have researched the effect of SF on the soil nutrients in Northern Shaanxi, China, but their results have often been contradictory. Therefore, we could comprehensively review these studies to evaluate the impacts of SF on soil nutrients from the following three aspects: soil layer, planting year and tree species. This study compiles the results of 2308 observations from studies ranging from 1978 to 2018 to assess the effects of SF on the distribution of the soil organic carbon, total nitrogen, available phosphorus, and available potassium contents in Northern Shaanxi, China. Compared with farmland or abandoned land, the results showed that the greatest increases in the soil organic carbon (118.57%) and total nitrogen (86.19%) contents were observed in the 0–20 and 20–40 cm soil layers, respectively. However, compared with farmland or abandoned land, the greatest increases in both the soil available phosphorus (14.17%) and available potassium (71.13%) contents were observed in the 0–20 cm soil layer. Planting Pinus Sylvestris var. mongolica (PS) is more conducive for increasing the soil organic carbon (120.86%) and available phosphorus (74.33%) contents. Additionally, Pinus tabuliformis (PT) is more beneficial for increasing the soil total nitrogen content (73.82%). Meanwhile, Robinia pseudoacacia (RP) and Caragana korshinskii (CK) are more effective for increasing the available potassium (72.93%) content. This study demonstrated that soil organic carbon (104.07%), total nitrogen (130.28%), and available potassium (125.60%) contents were most affected in planting years >30 years, and the available phosphorus content was most affected in planting years 0–10 years (27.33%). In conclusion, SF can significantly increase soil nutrient contents in areas of Northern Shaanxi, China. Planting shelter forest is recommended to improve the soil environment and achieve the greatest soil fertility benefits. [ABSTRACT FROM AUTHOR]

• The effect of a woodland habitat can be influenced by another woodland habitat. • Nonnative woodlands are not detrimental when combined with native forests. • Nonnative woodlands are not a surrogate of natural forests. • Management plans should account for the entire woodland mosaic. In Europe land use change has produced loss and fragmentation of the original forest habitat. On the other hand, the area covered by tree plantations and altered stands dominated by exotic tree species is increasing. Forest specialist birds are considered to be among the best candidates to assess the consequences of this transformation on wildlife. Here we investigate the link between the abundances of three forest specialist bird species (the Eurasian Nuthatch Sitta europaea , the Marsh Tit Poecile palustris and the Lesser Spotted Woodpecker Dryobates minor) and the woodland habitats of a highly modified landscape located in north-western Italy. In the area, the cover of anthropogenic woodland habitats, such as poplar plantations and Black Locust (Robinia pseudoacia) stands, exceeds that of native oak and riparian forests. During breeding season, birds were counted for three times along 105 transects of 300 m each, scattered in all the wooded contexts of the study area. Using n-mixture models, we investigated the effect of the amount and configuration of woodland habitats on the abundances of each species. First we selected for each variable the strongest scale of effect, ranging from 0.1 to 4 km. Then we built a full model including all variables at selected scales, accounting for correlation among variables and possible interactions. Forest specialists' abundances were affected by the composition of the entire woodland mosaic, not of native forests only. A high cover of nonnative woodlands in the landscape showed a null or positive effect on the species, if combined with a high cover of native forests. However, at a local scale and when dominating in the landscape, nonnative woodlands had mostly a detrimental effect. Alongside with the protection of remnant native forests, it should be contemplated the retention of nonnative woodland habitats when these contribute to enhance the heterogeneity of the landscape. [ABSTRACT FROM AUTHOR]

• Manipulated rainfall reduction lowered transpiration and growth of black locust trees. • Simulated drought weakened the response of sap flow to meteorological variables. • It showed different behavior under long or severe drought from short term drought. • The plantations in semiarid area tend to suffer from future precipitation decrease. Black locust (Robinia pseudoacacia) plantations have been widely established in the semiarid and sub-humid areas of central China. Under the condition of global climate change, which is introducing much uncertainty of precipitation patterns in this region, it is of special significance to investigate their responses to precipitation. Here, we investigated sap flow response to reduced throughfall. Stem sap flow was measured from 2011 to 2017 using Granier-type sensors. By placing waterproof panels within tree rows, about 47.5% precipitation was excluded from treated plots since April 2015. Differences in soil water content gradually increased to 4.3% between treated and control plots with continued throughfall exclusion. Decreased precipitation input significantly reduced the average sap flux density in treated plots by 9.1%–45.3%. The extent of this reduction depended on precipitation in the previous and current years. Transpiration and forest growth were negatively affected by the treatment. Furthermore, sap flow response to environmental factors became insensitive, with the discrepancy increasing with increasing drought duration, but was regained by rainfall recharge to soil water in the first two treatment years. However, prolonged drought might damage transpiration resilience capacity, as the saturated sap flux after soil water recharging during the wet period was still lower than that in the control plot in the latter year. Predawn leaf water potential was significantly lower in the treated plot compared to the control plot, whereas midday leaf water potential was similar. Whole tree hydraulic conductance (G P) was also similar between the two plots, except in extreme drought months when G P was much lower in the treated plot. In addition, the specific leaf area and stomatal density decreased in the treated plot. Therefore, decreases in precipitation would cause a transpiration reduction, weakening the tree's response to meteorological variables and lowering growth and productivity, potentially damaging transpiration resilience. These results suggest that black locust is sensitive to water changes, its capacity of drought tolerant is restrained by the drought time scale or drought severity, the use of such species in reforestation in semiarid regions should be implemented with caution. [ABSTRACT FROM AUTHOR]

• Stable isotopes and root distributions were used to identify water uptake of R. pseudoacacia. • The water-use pattern of R. pseudoacacia exhibited variation during the transition period. • The percentage of water used in shallow soil layers increased from April to July. • Water uptake from the deep soil layers decreased from April to July. • Water-use patterns during the dry season can aggravate the development of dry soil layers. Soil water plays a critical role in determining plant survival and growth globally, especially in water-limited regions. This study explores water-use characteristics of Robinia pseudoacacia during the transition period between the dry and rainy seasons in the Chinese Loess Plateau (CLP). A stable isotope technique (δ18O and δD) and two complementary approaches (i.e., the direct inference method and the MixSIAR model) were used to distinguish water source changes during this transition period. Based on δ18O and δD distribution patterns, we subdivided a 500 cm soil profile into four potential water sources: shallow (0–40 cm), intermediate-shallow (40–120 cm), intermediate (120–200 cm) and deep (200–500 cm). During the transition period, R. pseudoacacia exhibited different water uptake patterns. In April 26.2% and 48.4% of water uptake derived from the 40 to 120 and 200 to 500 cm soil profile layers; in May, 21.5%, 24.5% and 37.4% of water was absorbed from the 0 to 40, 40 to 120 and 200 to 500 cm soil profile layers. In June and July, 51.6% and 53.6% of the water mainly derived from the 0 to 120 cm soil profile layer, respectively. During the dry season (April), the trend in water uptake shifted to the deep soil layer, potentially a key period for the onset of soil desiccation in this soil layer. As precipitation increased, the proportion of water uptake from the shallow and intermediate-shallow soil layers increased. Because water-use pattern characteristics could provide important information on the development of the dried soil layer (DSL), the stable isotope technique could help reveal the water sources used by trees while also offering insight into water movement mechanisms of local ecosystems. Given its usefulness, the application of the stable isotope technique should be expanded in analyzing practical ecohydrological issues that occur in deep soils in the future. [ABSTRACT FROM AUTHOR]

• A large-scale investigation of soil aggregate stability after afforestation in the Loess Plateau. • Evaluation of the sustainability of large-scale afforestation by using soil aggregate stability. • Soil aggregate stability and erodibility were significantly influenced by Latitude and MAP. • The improvement of SOC and TN by RP and CK plantations were controlled by latitude and MAP. • The 36° N or 500 mm MAP line may serve as the dividing line for the RP and CK plantations. Revegetation in fragile ecosystems is an efficient means to increase aggregate stability and thus reduce soil erosion. However, the influence of large-scale afforestation on soil aggregate stability and erodibility in the Loess Plateau is not well understood. To assess the sustainability and suitability of widespread, long-term planting of plantations in terms of soil aggregate stability (mean weighted diameter (MWD) and geometric mean diameter (GMD)) and erodibility (K), we performed a large-scale investigation of soil aggregate stability and soil erodibility of Robinia pseudoacacia (RP) and Caragana korshinskii (CK) plantations on the Loess Plateau. The results showed that the soil macroaggregate fraction (>0.25 mm) content under RP and CK plantations had a decreasing trend with increasing latitude. Moreover, soil aggregate stability and soil organic carbon (SOC) and total nitrogen (TN) contents in RP and CK plantations decreased with increasing latitude. RP and CK plantations did not always result in improvement of soil aggregate stability and the accumulation of SOC and TN, which depended on the latitude and precipitation conditions. Specifically, RP planting in the south warm temperate forest subzone (STFZ) and north warm temperate forest subzone (NTFZ) could enhance the macroaggregate content (>5 mm), soil aggregate stability and soil nutrients, while CK planting for the improvement of the soil macroaggregate content, soil aggregate stability and soil nutrients in the temperate forest steppe subzone (TFSZ) was more effective than was RP planting. Correlation analysis showed that the latitude, longitude and mean annual precipitation (MAP) were significantly correlated with soil MWD, GMD, K values, SOC and TN across the RP and CK plantations, and soil MWD, GMD, and K values were significantly correlated with SOC and TN in RP and CK plantations. The changing trends of SOC and TN with latitude and longitude were consistent with that of soil aggregate stability with latitude and longitude under RP and CK plantations, indicating that changes in the SOC and TN concentrations will cause changes in soil aggregate stability and erodibility. Additionally, the effects of RP and CK plantations on the soil aggregate stability, erodibility, SOC and TN content were different and distinguished by latitude and MAP. RP plantation resulted in more SOC and TN accumulation, enhanced the soil aggregate stability and decreased erodibility compared with CK plantation in areas with MAP >500 mm or latitude <36° N; in contrast, in sites with MAP <500 mm or latitude >36° N, CK plantation had slight advantages over RP plantation. This study indicated that the changes in soil aggregate stability, erodibility, SOC and TN accumulation following RP and CK plantations had different patterns along latitude and precipitation gradients. Therefore, the 36° N or 500 mm precipitation threshold may be the dividing line for planting RP and CK plantations. Overall, our study produces unique insights into the relative significance of environmental factors that influence aggregate stability at large scales and is useful for selecting suitable afforestation species and locations to optimize forest management with sustainable production. [ABSTRACT FROM AUTHOR]

• Field data about drivers of invasive trees seedlings (ITS) survival is scarce. • We evaluated the impact of environmental factors on ITS survival for three species. • We used a set of 186 study plots and 11,135 labelled ITS over three years. • ITS survival (mean 0.1–12.5%) depended mostly on light availability and competitors. • ITS are abundant, but survival is lowest beneath parent trees. Although invasive trees species spread effectively across different habitats, data on survival of their seedlings are scarce. We compared seedling survival after the first year from germination for the three most invasive tree species in temperate Europe. We also assessed the impact of light availability, parental tree stands and intra- and inter-specific competition. We studied seedlings of three invasive species: Prunus serotina Ehrh., Quercus rubra L. and Robinia pseudoacacia L., in a set of 186 study plots in W Poland over three years (2015–2018). In total, we labelled 11,135 seedlings. We assessed importance of variables using machine learning techniques. Mean seedling survival was 3.9 ± 1.2%, 12.5 ± 2.2% and 0.1 ± 0.1% for P. serotina , Q. rubra and R. pseudoacacia respectively, and was higher than for native species. Survival of Q. rubra seedlings depended mostly on intraspecific competition in understory, light availability and parental trees availability. Survival of P. serotina seedlings depended mostly on intra- and inter-specific competition, germination year (precipitation seasonality) and light availability. Our study explained that despite the high seedling densities of invasive species beneath parental tree canopies, their survival was lower than in surrounding forests. These two aspects of the establishment process (seedling abundance and survival) contribute to the dynamic equilibrium between limiting (low survival beneath maternal tree canopies) and facilitating (high seedling densities beneath maternal trees canopies) the growth of young generations of invasive tree species. [ABSTRACT FROM AUTHOR]

• Black locust growth is currently limited by low temperatures in Mediterranean region. • We inverse calibrated GOTILWA + vegetation model from observed sap flow data. • Increasing severity of climate change enhances black locust growth. • Growth enhancement is driven by an increased daily productivity and an extended growing season. Mediterranean riparian forests are comparably humid environments that provide shelter for several broadleaved deciduous tree species at their southernmost distribution margin. The stability of these communities, however, is threatened by climate change as well as invasive tree species, such as black locust (Robinia pseudoacacia L.). So far, black locust's European distribution appears to be mostly limited by low temperatures, but global warming might enhance its growth in colder areas. Moreover, R. pseudoacacia can better access water from the phreatic level than some native non-phreatophytic tree species such as European ash (Fraxinus excelsior L.). In this study, we compare the performance of European ash, a native deciduous tree species at its southernmost distribution border, with the invasive black locust, under a range of climate change projections, in a stand located at N.E. Spain. We first use Bayesian inference to calibrate the GOTILWA + vegetation model against sap flow data for both tree species. We then project each tree species' performance under several climate change scenarios. Our results indicate that increasing temperatures will enlarge black locust's vegetative period, leading to substantially increased annual productivity if the phreatic water table keeps reachable. For European ash, we project a slight increase in productivity, but with higher uncertainty. Our findings suggest that black locust will profit more from global warming than the native European ash, which is concerning because of the already detrimental impact of black locust for the local ecosystems. We conclude that climate change has the potential to stimulate black locust growth on Mediterranean riparian forests. Forest management should therefore include mechanisms to avoid black locust establishment, such as avoid clear-cutting and maintaining closed riparian forest canopies. [ABSTRACT FROM AUTHOR]