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ABSTRACT Plants, being immobile, are exposed to environmental adversities such as wind, snow and animals that damage their structure, making regeneration essential for their survival. The adventitious roots (ARs) primarily emerge from a detached explant to uptake nutrients; therefore, the molecular network involved in their regeneration needs to be explored. DNA methylation, a key epigenetic mark, influences molecular pathways, and recent studies suggested its role in regeneration. In our research, the application of 5‐azacytidine (5‐azaC), an inhibitor of DNA methylation, caused the earlier initiation and development of root primordia and consequently enhanced the AR regeneration rate in Robinia psuedoacacia L (black locust). The whole‐genome bisulfite sequencing (WGBS) revealed a decrease in global methylation and an increase in hypomethylated cytosine sites and regions across all contexts including CHH, CHG and mergedCG caused transcriptional variations in 5‐azaC‐treated sample. The yeast two‐hybrid (Y2H) assay revealed a RpMYB2‐centred network of transcriptionally activated transcription factors (TFs) including RpWRKY23, RpGATA23, RpSPL16 and other genes like RpSDP, RpSS1, RpBEN1, RpGULL05 and RpCUV with nuclear localization suggesting their potential co‐localization. Additionally, yeast one‐hybrid (Y1H) assay showed the interaction of RpMYB2 interactors, RpGATA23 and RpWRKY23, with promoters of RpSK6 and RpCDC48, and luciferase reporting assay (LRA) validated their binding with RpSK6. Our results revealed that hypomethylation‐mediated transcriptomic modifications activated the RpMYB2‐centred gene network to enhance AR regeneration in black locust hypocotyl cuttings. These findings pave the way for genetic modification to improve plant regeneration ability and increase wood production while withstanding environmental damage. [ABSTRACT FROM AUTHOR]

The invasion of alien woody species may have broad ecological, economic, and health impacts on ecosystems and biodiversity under climate change. Previous studies showed that disrupting the biodiversity conservation mechanisms in protected areas can seriously threaten natural ecosystems and the protection of rare and endangered species in such protected areas. However, there is currently no standard for evaluating the invasion risk of woody plants under climate change when establishing national parks in China. Therefore, we used a species distribution model to evaluate the invasion risk of 250 invasive alien woody species in potential national park sites in Xinjiang under climate change. The results indicated that the probability of forest invasion in the potential Altai Kanas National Park was determined to be significantly higher than that of the average level in Xinjiang nature reserves, both under current and future climate conditions. At the same time, the probability of invasive woody species invading coniferous forests, broad‐leaved forests, and grassland ecosystems is higher in the Altai Kanas and Tianshan potential national parks. We found that Acer negundo, Robinia pseudoacacia, and Amorpha fruticose in potential parks in Xinjiang have higher invasion potential and thus require heightened vigilance to stop their spread. This study contributes to the monitoring and management of national parks and provides an actionable foundation for protecting ecosystem functions and minimizing the potential risk of invasive alien species under climate change. [ABSTRACT FROM AUTHOR]

Rainfall redistribution plays a crucial role in the water cycle. However, the main factors affecting the redistribution of rainfall remain uncertain. We chose three different plantations—cork oak (Quercus variabilis Bl.), oriental arborvitae (Platycladus orientalis L.) and black locust (Robinia pseudoacacia L.)—to investigate the role of plantations in rainfall redistribution and to determine the main factors influencing rainfall redistribution. The results indicated that cork oak exhibited the highest stemflow (0.34%) and the lowest canopy interception (12.58%), whereas black locust had the lowest stemflow (0.21%), and oriental arborvitae displayed the greatest canopy interception (32.8%). Under different density conditions for cork oaks, the stemflow was highest (0.39%) in low‐density forests with 750 trees ha−2 and lowest (0.34%) in medium‐density forests with 1100 trees ha−2. Meanwhile, the highest canopy interception (17.68%) was observed in high‐density forests (1300 trees ha−2), while the lowest interception rate (9.22%) was found in low‐density forests. The main factors affecting rainfall redistribution and their contribution rates were as follows: bark roughness index (35%), wind speed (18.6%), tree species (14.2%), diameter at breast height (11.2%), stand density (9.6%) and rainfall amount (5.4%). Our findings suggested that structural characteristics of trees are the primary factors affecting rainfall redistribution. Planting cork oak in the rocky mountain regions of North China is recommended because of its substantial stemflow production, particularly under low‐density growth conditions. Therefore, this study has significant guiding implications for the selection of afforestation tree species in similar rocky mountain areas globally. [ABSTRACT FROM AUTHOR]

Soil water is a crucial factor for the growth of vegetation and sustainable development in water‐limited areas. After large‐scale vegetation restoration on the Chinese Loess Plateau, understanding the relationship between vegetation and deep soil moisture has become a crucial focus in current research. In this study, artificial forest (Pinus tabulaeformis [PT], Robinia pseudoacacia [RP] and Platycladus orientalis [PO]), apple orchard (AO), secondary forest (SF) and farmland (FL) were selected as the research objects, and grassland (GL) as the control, using soil‐drilling techniques. We systematically monitored the soil water content of 0–10 m soil layer over two hydrological years, and explored the effects of different vegetation types on soil water deficiency. The results showed that: (1) The deep soil water various significantly among different vegetation types. Compared with GL, the soil water content in all forest land was generally lower, and this difference became more pronounced in deeper soil layer (>7 m), which indicating the depth of the influence of vegetation on soil water has reached 10 m. (2) The mean soil water deficit size (SWDS) values of PT (0.14), RP (0.17), PO (0.07), AO (0.15), SF (0.10) and FL (0.27) in 0–1 m were all positive, indicating that surface soil water had accumulated during more than half of the sampling periods. In the 2–10 m soil layer, mean SWDS was negative in all vegetation types except in FL, leading to soil desiccation. SWDS was found to fluctuate with soil depth. (3) SWDS was affected by a combination of soil properties and vegetation growth. Our results indicate that the current afforestation model could lead to the deficiency of deep soil water. Therefore, it is imperative to make reasonable vegetation structure according to the available local soil and water resources in future vegetation allocation and management. [ABSTRACT FROM AUTHOR]

Due to the open‐cast mining activities, a large area in the Lusatian region in eastern Germany was left unproductive. Robinia pseudoacacia L. was planted within different ages in that large area as a short rotation coppice for woody biomass cultivation as well as to increase soil nutrients by increasing plant phosphorous (P) availability, accumulating organic matter input and biological nitrogen fixation. In this experiment, soil chemical analysis has been done to investigate the improvement and status of P in the mining soil depending on the ages of plantation (16, 17, 18, and 27 years old) of Robinia pseudoacacia L. The results show a higher P sorption in the oldest site, and the average P sorption capacity (PSC) obtained in the oldest site was 21.0 mmol Kg−1, which was 3–4 times higher than the youngest site. However, all the values were very low compared with the optimum plant growth level, and low P desorption indicates a low level of plant‐available P in the soil. The lower sorption properties with the small amount of oxalate iron (Feox) and oxalate aluminum (Alox) indicate the general P deficiency in the soil. However, a comparison from a previous study on the same experimental areas shows that not much improvement has occurred in soil P, and the change in soil P dynamics is very low. Nevertheless, the improvement of the values with increasing ages of Robinia pseudoacacia L. indicates that further improvement may be expected in soil nutrients with time. [ABSTRACT FROM AUTHOR]

Given the context of significant global warming and the intensification of extreme climate events in the last century, large‐scale reforestation and afforestation have been recognized as effective strategies to mitigate the climate crisis. Since the 1970s, China has launched several afforestation programs aimed at regional ecological protection, playing an important role in reaching carbon neutrality by 2060. This study provided a detailed analysis of the growth suitability of the main planted conifers (Pinus sylvestris var. mongolica and Pinus tabulaeformis) and broadleaves (Populus spp., Robinia pseudoacacia) in the semi‐arid northern China. We compared the radial growth trends of plantations and their responses to extreme droughts from 1980 to 2018. Growth of most plantations has significantly increased over time, but broadleaves showed recent growth reductions in the past decade, which may be related to tree age and reduced soil moisture. Nevertheless, under warmer climate scenarios, the growth of plantations is forecasted to continue increasing. Broadleaves showed a better post‐drought recovery, probably linked to their anisohydric behavior, than conifers, which presented a better resistance to drought. Growth of conifers depended more on warmer temperature and better precipitation conditions during the growing season, whereas broadleaves mainly reacted to warm temperature. Additionally, pre‐drought growth levels weakened resilience components, while post‐drought precipitation compensated for drought‐induced growth deficit. Growth and resilience were negatively related to tree age, while higher stand density reduced growth. This assessment and projections of growth and drought resilience indicate the sustainability of most plantations in semi‐arid regions, but future warmer and drier conditions may lead to an uncertain future regarding forest health and reduce their carbon sink potential. [ABSTRACT FROM AUTHOR]

Analyzing deep soil water use (DSWU) response to precipitation change and its impact on tree physiology is necessary to understand tree mortality mechanisms, especially in drylands. Using a process‐based model parameterized with in situ measured fine root distribution data for 0–2,000 cm depth, along with a root‐cutting (below 200 cm depth) numerical experiment, this study explored DSWU strategies and their contribution to total water consumption during different precipitation years, as well as their relationship to tree gas exchange traits, in mature apple (Malus pumila Mill) tree and black locust (Robinia pseudoacacia L.) plantations in both wetter (Changwu, 583 mm) and drier (Yan'an, 534 mm) sites on China's Loess Plateau. Results showed that DSWU at 200–2,000 cm depth in different precipitation years of both species mainly occurred during the early growing seasons. On average, DSWU contributed 22.9% and 25.1% to the total water consumption of apple trees and black locust, respectively, and its contribution increased to 26.0% and 36.7% in extremely dry years. Moreover, the lack of DSWU significantly decreased (p < 0.05) stomatal conductance (by 16.9%, 16.9%, 47.4%, and 11.4%, respectively) and photosynthetic rates (by 37.1%, 20.1%, 28.5%, and 16.4%, respectively) of Changwu apple trees, Yan'an apple trees, Changwu black locust and Yan'an black locust in extremely dry years. Similar reductions occurred only in Yan'an for both tree species in normal years. In contrast, no significant differences were found in gas exchange traits in extremely wet years. Our results highlight that DSWU is an important strategy for plantations in the deep vadose zone region to resist extreme drought. Key Points: A process‐based model parameterized with measured fine root data for 0–20 m was used to explore DSWU and its relationship to tree gas exchange traitsDeep (2–20 m) soil water contributed 20.3%–26.0% and 14.4%–36.7% to total water consumption for apple tree and black locust, respectivelyDWSU can compensate for the drought effect on gas exchange in dry years better than in wet years for dryland tree plantations [ABSTRACT FROM AUTHOR]

The role of diverse soil microbiota in restoring erosion‐induced degraded lands is well recognized. Yet, the facilitative interactions among symbiotic arbuscular mycorrhizal (AM) fungi, rhizobia, and heterotrophic bacteria, which underpin multiple functions in eroded ecosystems, remain unclear. Here, we utilized quantitative microbiota profiling and ecological network analyses to explore the interplay between the diversity and biotic associations of root‐associated microbiota and multifunctionality across an eroded slope of a Robinia pseudoacacia plantation on the Loess Plateau. We found explicit variations in slope multifunctionality across different slope positions, associated with shifts in limiting resources, including soil phosphorus (P) and moisture. To cope with P limitation, AM fungi were recruited by R. pseudoacacia, assuming pivotal roles as keystones and connectors within cross‐kingdom networks. Furthermore, AM fungi facilitated the assembly and composition of bacterial and rhizobial communities, collectively driving slope multifunctionality. The symbiotic association among R. pseudoacacia, AM fungi, and rhizobia promoted slope multifunctionality through enhanced decomposition of recalcitrant compounds, improved P mineralization potential, and optimized microbial metabolism. Overall, our findings highlight the crucial role of AM fungal‐centered microbiota associated with R. pseudoacacia in functional delivery within eroded landscapes, providing valuable insights for the sustainable restoration of degraded ecosystems in erosion‐prone regions. Highlights: Robinia pseudoacacia strategically recruited AM fungi to cope with phosphorus limitation.AM fungi interacted with the assembly and composition of bacteria and rhizobia.AM fungal‐centered underground network supported slope multifunctionality.The R. pseudoacacia–AM fungi–rhizobia association restores eroded ecosystems. [ABSTRACT FROM AUTHOR]

Forest plantations most likely promote exotic plant invasion. Using an in situ monitoring method, this study investigated the traits correlated with growth and reproduction of an understory invader, Phytolacca americana L., and ecological factors including understory irradiance, soil stoichiometry and microbial patterns associated with these traits in different exotic plantations of Robinia pseudoacacia L. and Pinus thunbergii Parl. at Mount Lao, Qingdao, China. We found that the traits of P. americana underneath the R. pseudoacacia stand might be situated at the fast side of the trait economic spectrum. The R. pseudoacacia stand appeared to "nurse" P. americana. Furthermore, we intended to explain the nurse effects of R. pseudoacacia stands by examining their ecological factors. First, the R. pseudoacacia stand created understory light attenuation, which matched the sciophilous feature of P. americana. Second, the soil beneath the R. pseudoacacia stand might benefit P. americana more since the soil has greater resource availability. Third, a higher microbial diversity was found in the soil derived from P. americana underneath the R. pseudoacacia stand. A greater abundance of plant pathogens was detected in the soil derived from P. americana in the R. pseudoacacia stand, while more abundant mycorrhizal fungi were detected in the P. thunbergii stand. We speculate that plant pathogens can defend P. americana from aggression from other understory competitors. The mycorrhizal fungi in the P. thunbergii stand might benefit P. americana while simultaneously benefiting other understory plants. Intensive competition from other plants might interfere with P. americana. The potential relationships between plant performance and ecological factors may explain the invasion mechanism of P. americana. The present study provides a novel insight on the facilitative effects of exotic tree plantation on an exotic herb through the modification of soil biota, with implications for the biocontrol of invasive species and forest management and conservation. [ABSTRACT FROM AUTHOR]

There is a long history of humans either intentionally or accidentally moving plant species to areas outside of their native ranges. In novel environments, populations of many of these plant species exhibit explosive population growth and spread, in part due to the absence of coevolved enemies such as herbivorous insects. However, over time such enemies can 'catch up' with their host and re‐establish host–herbivore relationships. Though this phenomenon has been documented in several systems, little evidence exists on how this re‐assembly of enemies results in increased levels of herbivory. In this study we focus on the case of black locust Robinia pseudoacacia, a sparsely populated tree species when growing on undisturbed sites in its limited native range in the eastern USA but a highly invasive species, especially in disturbed environments, in most temperate world regions. We recorded folivore damage on invasive populations in five continents, including both native and invaded portions of North America. Here, we investigated 1) how total foliage damage and damage caused by different groups of folivores differs among regions; 2) how seasonal development of folivore damage differs among regions; 3) how folivory varies with distance from the native range within North America; and 4) how the number of recorded specialist folivores correlates with the amount of folivory. We observed strong differences among regions in the amount and type of folivore damage, with the native range experiencing the highest damage, especially that caused by the native chrysomelid beetle Odontota dorsalis, which is limited to the native and invaded North American range of R. pseudoacacia. Among world regions, total folivory is negatively associated with the distance from the native range and positively associated with the number of established R. pseudoacacia specialist folivore species, supporting the hypothesis that global patterns of herbivore invasions are associated with diminished enemy release. [ABSTRACT FROM AUTHOR]

Soil heterotrophic microorganisms play crucial roles in soil biogeochemical cycles by secreting extracellular enzymes, but their metabolism is often limited by resource availability. Identifying major resources that limit soil microbial metabolism could help to create reasonable management practices for the maintenance of ecosystem function. Robinia pseudoacacia plantations perform crucial functions in reconstituting the ecological integrity of disturbed ecosystems; however, soil microbial metabolic limitations in R. pseudoacacia plantations remain poorly understood. Herein, R. pseudoacacia plantations of four age classes (10, 22, 37, and 47 years old) were sampled in the loess hilly‐gully region of northern Shaanxi Province in China. This study analyzed the effects of stand age on soil extracellular enzyme activities and soil microbial metabolic limitation. It also determined the main factor driving soil microbial metabolic limitation and extracellular enzyme activities. The results of ecoenzymatic stoichiometry showed that nitrogen (N) limited soil microbial metabolism in R. pseudoacacia plantations. Soil microbial metabolism at 10 and 22 years old were more carbon (C)‐ and N‐limited than that at 37 and 47 years old. Except for N‐ and phosphorus (P)‐acquiring enzyme activities at 10–20 cm, soil C‐, N‐, and P‐acquiring enzyme activities (in 0–10 and 10–20 cm of soil) at 10 and 22 years old were significantly higher than those at 37 and 47 years old. The enzymatic ratio of C:N:phosphorus(P) acquisition in all R. pseudoacacia plantations, regardless of stand age and soil depth, deviated from 1:1:1. Soil nutrients explained most of the variation (90.80%) in soil extracellular enzyme activities based on variation‐partitioning analysis. The partial least squares path model showed that soil nutrients had the highest total negative effect on microbial C limitation and microbial N/P limitation. Our results confirmed that microbial metabolic limitation was induced by soil resource deficits. The findings provide another visual that increases our understanding of soil microbial metabolic limitation in R. pseudoacacia plantations. [ABSTRACT FROM AUTHOR]

Afforestation is considered to be an important means to improve the ecological environment and mitigate climate change. However, inappropriate vegetation restoration can result in severe soil desiccation and ecosystem degradation in water‐limited regions. Here, we evaluated the effects of six different afforestation patterns on soil moisture content, soil organic carbon (SOC) sequestration, and especially the conversion efficiency of the two on the Loess Plateau, taking abandoned land (Al) as a control sample, and attempting to recognize a suitable afforestation pattern based on these parameters. The six afforestation patterns considered were two single‐species shrub plantations (Caragana korshinskii, Ck and Hippophae rhamnoides, Hr), two single‐species tree plantations (Robinia pseudoacacia, Rp and Platycladus orientalis, Po), and two mixed‐species plantations (Rp, Po, Pinus tabuliformis, Pt, and Ulmus pumila, Up mixed plantations (MP); Po and Pt with terracing [MP + T]). We found that mixed‐species plantations (MP + T and MP) have less soil moisture depletion than single‐species plantations, Ck had the highest SOC sequestration but also had a significant deep soil moisture deficit. MP + T had less deep soil moisture deficit but also had lower SOC sequestration than MP. MP show a better comprehensive effect when considering both soil organic carbon sequestration and soil water‐carbon conversion efficiency. Therefore, multispecies MP represent a potentially valuable approach to sustainable afforestation patterns for soil carbon sequestration on the Loess Plateau. This afforestation pattern has the potential to be applied in other similar semi‐arid and semihumid regions. Our results provide insight into vegetation restoration in areas with degraded land. In future afforestation activities, planners must alleviate regional water pressure, increase soil carbon sequestration by increasing species richness, and select the best combination of species to optimize the stability and sustainability of the plantation ecosystem. [ABSTRACT FROM AUTHOR]

Species composition of forests is a very important component from the point of view of nature conservation and forestry. We aimed to identify 10 tree species in a hilly forest stand using a hyperspectral aerial image with a particular focus on two invasive species, namely Ailanthus tree and black locust. Deep learning‐based training data augmentation (TDA) and post‐classification techniques were tested with Random Forest and Support Vector Machine (SVM) classifiers. SVM had better performance with 81.6% overall accuracy (OA). TDA increased the OA to 82.5% and post‐classification with segmentation improved the total accuracy to 86.2%. The class‐level performance was more convincing: the invasive Ailanthus trees were identified with 40% higher producer's and user's accuracies (PA and UA) to 70% related to the common technique (using a training dataset and classifying the trees). The PA and UA did not change in the case of the other invasive species, black locust. Accordingly, this new method identifies well Ailanthus, a sparsely distributed species in the area; while it was less efficient with black locust that dominates larger patches in the stand. The combination of the two ancillary steps of hyperspectral image classification proved to be reasonable and can support forest management planning and nature conservation in the future. [ABSTRACT FROM AUTHOR]

Rhizobia and arbuscular mycorrhizal fungi (AMF) are symbiotic microorganisms important for plants grown in nutrient-deficient and heavy metal-contaminated soils. However, it remains unclear how plants respond to the coupled stress by heavy metal and nitrogen (N) deficiency under co-inoculation. Here, we investigated the synergistic effect of Mesorhizobium huakuii QD9 and Funneliformis mosseae on the response of black locust (Robinia pseudoacacia L.) grown in sand culture to cadmium (Cd) under N deficiency conditions. The results showed that single inoculation of AMF improved the growth and Cd resistance of black locust, co-inoculation improved the most. Compared to non-inoculated controls, co-inoculation mediated higher biomass and antioxidant enzyme activity, reduced oxidative stress, and promoted nodulation, mycorrhizal colonization, photosynthetic capacity, and N, P, Fe and Mg acquisition when exposed to Cd. This increase was significantly higher under N deficiency compared to N sufficiency. In addition, the uptake of Cd by co-inoculated black locust roots increased, but Cd translocation to the above-ground decreased under both N deficiency and sufficiency. Thus, in the tripartite symbiotic system, not merely metabolic processes but also Cd uptake increased under N deficiency. However, enhanced Cd detoxification in the roots and reduced allocation to the shoot likely prevent Cd toxicity and rather stimulated growth under these conditions. [ABSTRACT FROM AUTHOR]

N2-fixing legumes can strongly affect ecosystem functions by supplying nitrogen (N) and improving the carbon-fixing capacity of vegetation. Still, the question of how their leaf-level N status and carbon metabolism are coordinated along leaf ageing remains unexplored. Leaf tissue carbon isotopic composition (δ13C) provides a useful indicator of time-integrated intrinsic water use efficiency (WUEi). Here, we quantified the seasonal changes of leaf δ13C, N content on a mass and area basis (Nmass, Narea, respectively), Δ18O (leaf 18O enrichment above source water, a proxy of time-integrated stomatal conductance) and morphological traits in an emblematic N2-fixing legume tree, the black locust (Robinia pseudoacacia L.), at a subtropical site in Southwest China. We also measured xylem, soil and rainwater isotopes (δ18O, δ²H) to characterize tree water uptake patterns. Xylem water isotopic data reveal that black locust primarily used shallow soil water in this humid habitat. Black locust exhibited a decreasing δ13C along leaf ageing, which was largely driven by decreasing leaf Nmass, despite roughly constant Narea. In contrast, the decreasing δ13C along leaf ageing was largely uncoupled from parallel increases in Δ18O and leaf thickness. Leaf N content is used as a proxy of leaf photosynthetic capacity; thus, it plays a key role in determining the seasonality in δ13C, whereas the roles of stomatal conductance and leaf morphology are minor. Black locust leaves can effectively adjust to changing environmental conditions along leaf ageing through LMA increases and moderate stomatal conductance reduction while maintaining constant Narea to optimize photosynthesis and carbon assimilation, despite declining leaf Nmass and δ13C. [ABSTRACT FROM AUTHOR]

This study aimed to determine the suitable reclamation ways of post‐mining magnesite. It was hypothesized that adding amendments and planting would decrease pH, increasing the nutrient availability and enhancing the soil microbial activity. Treatments included 200 g gypsum, 2 kg goat manure, and 200 g sulfur per square meter. Cedar (Cedrus libani A. Rich.), black locust (Robinia pseudoacacia L.), black pine (Pinus nigra J.F. Arnold), and sainfoin (Onobrychis sativa L.) were planted. Before and after the treatments, samples were taken from each experimental unit and analyzed. Analysis of the data indicated that the pH had decreased by 0.6 and 0.5 units on the gypsum + sulfur‐ and gypsum + manure‐treated experimental units, respectively, compared to the other treated plots. In addition, using manure significantly increased the organic matter N, P, and K content, by 3‐fold, 2.5‐fold, 7.5‐fold, and 2.5‐fold, respectively, and enhanced microorganism activity. The sulfur + manure treatment increased microbial C and N approximately twofold. Because the manure, sulfur, and gypsum treatments improved the tailings conditions for plant growth, the use of these amendments for mine tailing reclamation was strongly recommended. Across all treatments, cedar and black pine demonstrated 83 and 77% survival rates for the first 3 years of afforestation, respectively. For the same period, the black locust survival rate was 35% lower than that of the other species. The gypsum + manure application increased seedling height growth by about 20% for all three species compared to the other treatments. [ABSTRACT FROM AUTHOR]

The forest canopy affects the water entering the forest ecosystem by intercepting rainfall. This is especially pertinent in forests that depend on rainfall for their ecological water needs, quantifying and simulating interception losses provide critical insights into their ecological hydrological processes. In the semi‐arid areas of the Loess Plateau, afforestation has become an effective ecological restoration measure. However, the rainfall interception process of these plantations is still unclear. To quantify and model the canopy interception of these plantations, we conducted a two‐year rainfall redistribution measurement experiment in three typical plantations, including a deciduous broadleaf plantation (Robinia pseudoacacia) and two evergreen coniferous plantations (Platycladus orientalis and Pinus tabuliformis). Based on this, the revised Gash model was used to simulate their interception losses, and the model applicability across varying rainfall types was further compared and verified. The experiment clarified the rainfall redistribution in the three plantations, and the proportions of throughfall to gross rainfall in Robinia pseudoacacia, Platycladus orientalis, and Pinus tabuliformis were 84.8%, 70.4%, and 75.6%; corresponding, the stemflow proportions were 2.0%, 2.2%, and 1.8%; the interception losses were 13.2%, 27.4%, and 22.6%, respectively. The dominant rainfall pattern during the experiment was characterized by low‐amounts, moderate‐intensity, and short‐duration, during which the highest interception proportions across the three plantations were observed. We used the Penman‐Monteith equation and the regression method, respectively, to estimate the canopy average evaporation rate of the revised Gash model, finding that the latter provides a closer match to the measured cumulative interception (NSE >0.7). When simulating interception under the three rainfall patterns, the model with the regression method better simulated the cumulative interception and event‐scale interception for Platycladus orientalis and Pinus tabuliformis plantations under the dominant rainfall pattern. The results contribute valuable information to assess the impact of forest rainfall interception on regional hydrologic processes. [ABSTRACT FROM AUTHOR]

Robinia pseudoacacia (black locust), an alien species in Japan, has been commonly planted to rehabilitate degraded land and as a resource for the production of honey. Although very few R. pseudoacacia adult trees are found in established mature forests, the management of R. pseudoacacia is a vital and urgent matter because of astounding growth potential, which negatively affects biodiversity and native vegetation. For this reason, we evaluated the seasonal shade‐acclimation capacity of black locusts from the viewpoint of photosynthetic nitrogen use (PNU) and their partitioning. We assessed in situ photosynthetic N use traits of R. pseudoacacia leaves at open sites (relative photosynthetic photon flux density: (rPPFD) > 90%) and shaded sites (rPPFD < 22%) on the forest floor in larch (Larix kaempferi Carr.) plantations. Leaf unfolding started in late May and leaves turned yellow by mid‐October just before leaf shedding. Shoot length at open sites was three times longer than at shaded sites. R. psudoacacia at open sites has more the leaflet number of each pinnate compound leaf than shaded sites from mid‐August to October, and the size of leaflets at shaded sites was about 20% smaller than it was at the open sites. Leaf mass per area showed (mean ± standard deviation) 40.00 ± 2.14 g m−2 at the open sites and 22 ± 1.56 g m−2 at the shaded sites from June to October. The light‐saturated photosynthetic rate peaked at 22 μmol m−2 s−1 at the open sites in July. At the shaded sites, it gradually increased to 7–10 μmol m−2 s−1 around August, and then decreased at both sites toward zero in mid‐October. The total N content during the growth period was 1.60 ± 0.17 g m−2 at open sites and 1.16 ± 0.15 g m−2 at shaded sites. Unlike other tree species, N partitioning to photosynthetic organs was not affected by light conditions. These findings suggested R. psudoacacia cannot acclimate to shady conditions. [ABSTRACT FROM AUTHOR]

The interaction between novel saponification products (RCOONa or RCOOK) of Robinia pseudoacacia seed oil and cetyltrimethyl ammonium bromide (CTAB) in aqueous solution have been investigated by surface tension method at 25°C. The critical micelle concentration (cmc) of RCOONa/CTAB and RCOOK/CTAB mixture were measured. The surface properties of saponification products, CTAB as well as the mixed system were explored and compared. The composition, activity coefficient of mixed micelle, and the interaction parameters (βσ, βM) between surfactants were estimated according to the Regular Solution Theory, the Clint's model and the Rubingh's model in the framework of pseudophase separation model. The experimental results suggested that both RCOONa and RCOOK have synergism with CTAB in mixed micelle formation and surface tension reduction through calculating of βσ and βM in the mixed system. This could be attributed to the strong interaction between the head groups with opposite charges in the surfactant molecules. [ABSTRACT FROM AUTHOR]

Converting degraded croplands into perennials has been proposed as an effective method of soil N sequestration, however, the dynamics of deep soil N (>100 cm) following cropland conversion are not well understood. In this study, we synthesized 3049 observations to detect the changes in deep soil N content following cropland conversion on the arid and semiarid Loess Plateau. Our results showed that converting croplands into perennials significantly increased the soil N content by an average of 57.4%, 23.1%, and 29.5% in the surface (0–20 cm), subsurface (20–100 cm), and deep (100–200 cm) layers, respectively. The extent of the increase was influenced significantly by the land‐use conversion types and tree species. Specifically, the conversion of croplands into deep‐rooted forests or shrubs, particularly Robinia pseudoacacia and Caragana microphylla, exhibited higher advantages in deep soil N sequestration. Moreover, deep soil N sequestration increased significantly with time since cropland conversion (p < 0.001), and the rates in deep soils were approximately 26.1% and 66.7% of that in 0–20 and 20–100 cm soils, respectively. In the long term, converting croplands into forests and shrubs showed higher potential for deep soil N sequestration. Linear regression analysis showed that the changes of deep soil N sequestration were influenced significantly by initial soil N content (p < 0.001) and humidity index (p < 0.001), with the slopes in >100 cm layers being 2 to 3 times than that in the top meter, indicating higher sensitivity in deep soils. Overall, this study provides evidence that converting degraded croplands into perennials may contribute to deep soil N accumulation in N‐limited regions, which could potentially alleviate N limitation and sustain long‐term ecosystem carbon sequestration. [ABSTRACT FROM AUTHOR]

The network of natural forests and shelterbelts is a crucial element of agroforestry systems for the efficient and environmentally sustainable land use in Ukraine. From 2016 to 2021, we studied the quality of black soils structure under steppe wildland herbaceous vegetation, man-made tree plantations of Robinia pseudoacacia L. and Quercus robur L., and native forest vegetation of ravines and floodplains in the steppe zone of Ukraine. According to the visual evaluation of soil structure (VESS) scores, the content of the agronomically valuable fraction (AVF), soil organic carbon (SOC) and earthworm casts, native forest soils (Chernozems and Phaeozems) had a significantly (p < .05) higher soil structural quality in 0-25 cm layer as compared with the Chernozems under the steppe vegetation and shelterbelt plantations. In the conditions of steppe landscapes, VESS methods were shown to provide efficient diagnostics to differentiate the black soil structural quality of low-intensity land use systems, that is steppe wildlands, shelterbelts, native forests: VESS indicators significantly (p < .05) correlated with quantitative characteristics of soil structure. The most significant dependence was found between VESS parameters and earthworm casts content. The need to improve VESS method was demonstrated, that is to assign higher weight to the earthworm bioturbation process as one of the key indicators of soil structural quality. [ABSTRACT FROM AUTHOR]

Soil dissolved carbon (C) and nitrogen (N) are early sensitive indexes to evaluate the changes in C and N pools in terrestrial ecosystems. However, there are few studies on the changes in soil dissolved C and N with revegetation age and their stratification ratios (SRs), especially for deep soil. The changes in soil dissolved C and N and their SRs in one farmland and five Robinia pseudoacacia plantations (RP: 15a, 20a, 25a, 30a and 40a) were studied. The results showed that RP plantations significantly increased the soil organic C (SOC) and total N (TN) stocks with increasing restoration age for 30 years in the shallow and middle soil layers and improved the stocks of dissolved total C (DTC), dissolved organic C (DOC), dissolved total N (DTN), dissolved organic N (DON) and dissolved inorganic N (DIN) in most soil layers, especially in the 20a, 25a and 30a plots. In the 0-200 cm soil layer, the middle and deep soil accounted for 50%-82% of the SOC and soil dissolved C stocks and 63%-84% of the soil TN and dissolved N stocks, respectively. At all soil depths, the SRs of SOC, TN, DTC, DOC and DIN in RP plots were greater than those in farmland plots, and the SRs of SOC and TN in almost all RP plots were >2. These results demonstrated that restoration age and soil depth had significant influences on SOC, TN and soil dissolved C and N, and RP forestation increased the SOC and TN stocks in the shallow and middle soil layers, and the soil dissolved C and N stocks in 20a, 25a and 30a plots were the largest; additionally, the middle and deep soil layers played important roles in estimating the soil C and N pools. In summary, RP afforestation significantly improved soil C and N and their dissolved fractions and the SRs, thus soil quality and nutrient availability consistently improved. [ABSTRACT FROM AUTHOR]

Revegetation influences microbial biomass stoichiometry by altering the substrate conditions, yet the differences in microbial stoichiometry homeostasis and the underlying drivers under different revegetation approaches remain unexplored. Here, we selected sites across three age classes of Robinia pseudoacacia plantation (RP) and abandoned land (AL), and quantified the microbial stoichiometric characteristics during farmland‐initiated restoration. Plant community composition, leaf and soil nutrients, and microbial community composition and diversity were also measured. We found that revegetation of former farmland under both restoration types resulted in non‐isometric changes in soil carbon (C), nitrogen (N), and phosphorus (P) contents, that is, decoupling of soil C and N from P. However, AL and RP succession exhibited homeostatic and plastic microbial biomass stoichiometry, respectively, in response to altered substrate stoichiometry. These differences were associated with adjustments in the above‐ and belowground biomes. Specifically, the synergistic increase of Compositae and Actinobacteria in the late AL succession allowed the ecosystem to reduce P demand and maintain microbial stoichiometric homeostasis. In contrast, higher leaf C and N input during RP succession may have resulted excessive microbial storage of elements, which in turn leads to stoichiometric convergence between microbial biomass and soil resources. In addition, RP succession caused changes in microbial community structure, mainly the continuous increase of Proteobacteria (copiotrophs, r‐strategists), which also potentially increased the requirement for resources to maintain homeostasis and ensure the rapid growth. These findings demonstrate that AL has a comparatively greater efficacy in maintaining microbial stoichiometric homeostasis during long‐term revegetation. Our study also highlights the importance of appropriately managing existing RP plantations to alleviate the pressure of P deficiency and sustainably maintain this fragile ecosystem. [ABSTRACT FROM AUTHOR]

The water consumption mechanism of plantations is important to understand for the selection of afforestation tree species and sustainable watershed management in semi‐arid regions. In this study, Robinia pseudoacacia and Pinus tabuliformis, which are commonly planted on the Loess Plateau of China, were selected to investigate the possible difference in water uptake modes. In 2019–2020, the stable isotopic compositions (δ2H, δ18O) of precipitation and the xylem and soil water of these two trees were sampled and compared using the direct inference approach and MixSIAR model. The difference in soil moisture was also measured. The results showed that the δ18O content of surface soil water (0–40 cm) was closely related to precipitation, while that of deep soil layers (100–200 cm) remained stable. The MixSIAR model performed appropriately in quantifying water apportionment, especially in the drought year of 2019. In July–August 2019, R. pseudoacacia showed strong drought resilience by absorbing water from the deep soil. The 0–40 cm and 100–200 cm soil layers contributed 0.325 and 0.376 to water absorption of R. pseudoacacia, and 0.675 and 0.151 to that of P. tabuliformis, respectively. However, there was a minor difference in the soil water uptake modes between the two species in the humid year of 2020. Compared with P. tabuliformis, R. pseudoacacia increased its consumption of water by 9.9% and 25.1% in the drought and humid year, respectively, which indicated that R. pseudoacacia plantations may contributed to drier deep soil layers. This study helps to improve our understanding of the water uptake mechanisms of common afforestation tree species on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Most forests are recovering from human land use, making it critical to understand the effect of disturbance on forest recovery. Forests of the eastern United States have a long history of land use, but it is unknown whether historical disturbances have contributed to their transition from ectomycorrhizal (ECM) to arbuscular mycorrhizal (AM) tree dominance. Disturbance may promote nitrogen (N)‐fixing trees in early succession, which can elevate soil N availability even after they die. Higher soil N availability may facilitate the competitive success of AM trees over ECM trees, but such 'N fixer founder effects' have not been empirically tested.Here, we analysed data from three land‐use disturbances in a temperate forest historically dominated by ECM trees: selective‐cutting (ranging from 0 to 52 m2 ha−1), clear‐cutting and agricultural abandonment. These disturbances occurred at different times, but long‐term data capture 3–7 decades of forest recovery.We found that the AM tree fraction in contemporary forests was 2, 4, and 6‐fold higher following selective‐cutting, clear‐cutting and agricultural abandonment, respectively, compared to forest composition in 1934. Across these disturbances we also observed an increasing abundance of the N fixer black locust immediately following disturbance. Using a simulation model parameterized by data from black locust, we estimated historical rates of symbiotic N fixation to understand the relationship between N fixation and AM dominance in individual plots. We found that N fixation was positively associated with the growth of ECM trees generally, and oak and hickory specifically, only following light selective‐cutting (<12 or <18 m2 ha−1 basal area extraction, respectively). Following higher levels of selective‐cutting and clear‐cutting, N fixation was positively associated with the growth of AM trees, particularly red maple and tulip poplar. Agricultural abandonment led to AM dominance regardless of N fixation rates.Synthesis and applications. Our findings suggest that common land use practices and black locust, a native N fixer, can reduce the dominance of ECM trees. If N fixers are likely to proliferate following disturbance, we might maintain ECM dominance by cutting trees at low densities and by applying prescribed fire to remove N. [ABSTRACT FROM AUTHOR]

Aim: Many invasive plant species benefit from enemy release resulting from the absence of insect herbivores in their invaded range. However, over time, specialized herbivores may 'catch up' with such invasive plants. Black locust is a tree species with a relatively limited native range in North America but has invaded large areas in virtually every temperate continent including North America. We hypothesize that both intra‐ and intercontinental spread of black locust leads to a parallel, though delayed pattern of intra‐ and intercontinental spread of insect herbivores. Location: Global. Taxon: Black locust, Robinia pseudoacacia, and its insect herbivores. Methods: We compiled historical records of the occurrence of insect herbivore species associated with R. pseudoacacia from all world regions. Based on this list, we describe taxonomic patterns and investigate associations between environmental features and numbers of non‐native specialist herbivores in the portion of North America invaded by R. pseudoacacia. Results: A total of 454 herbivorous species are recorded feeding on R. pseudoacacia across the world, with 23 of these being specialized on Robinia. From this group, seven species have successfully expanded their range beyond North America. Within North America, the richness of specialists is explained by a combination of road density, R. pseudoacacia density, distance from the R. pseudoacacia native range, and climate. Main Conclusion: Non‐native herbivore species have accumulated on invasive R. pseudoacacia in both North America and in other continents. The steady build‐up of invasions likely has diminished the enemy release that this invasive tree species has benefited from – a trend that will likely continue in the future. These findings support the hypothesis that invasive plants promote parallel though delayed invasions of specialist insect herbivores. [ABSTRACT FROM AUTHOR]

The broad leaf, deciduous black locust (Robinia pseudoacacia) and needle leaf, evergreen Chinese pine (Pinus tabulaeformis) are the major afforestation species on the Loess Plateau of China, accounting for 29.5% and 15.9% of the afforestation area, respectively. The decay of black locust and drying of the forest land soil in this region have caused serious concerns among scientific community and local management authorities. Understanding the hydrological characteristics of the afforestation plantation may provide clues for choosing proper species. However, previous studies demonstrated diverse or even contradictory understandings due to incomplete observations of the water balance. We used a model to reconstruct the water balance based on 5 years (2015–2019) of incomplete soil water and transpiration observations at the field for these two species. The R‐squares of linear regression analysis of simulated and observed soil water in black locust and Chinese pine plantations were 0.69 and 0.90, respectively; and transpiration was 0.62 and 0.69, respectively. Based on the reconstructed water balance components, we found that (1) black locust and Chinese pine had similar annual evapotranspiration in quantity. However, the Chinese pine transpired less and evaporated more water from the canopy than the black locust, with their ratios to the annual precipitation 50.7% and 69.7%, 26.3% and 17.2%, respectively; (2) the Chinese pine has higher evapotranspiration than the black locust in the non‐growing season, accounting for 19.5% and 9.2% of the annual evapotranspiration, respectively; and (3) the Chinese pine is more tolerable to soil water drought than black locust. The findings may suggest that the Chinese pine is a more favourable species for afforestation than the black locust from the point view of drought resistance in this region. [ABSTRACT FROM AUTHOR]

Restoration of natural secondary forests and afforestation of introduced tree species are major effective measures for revegetation. The semiarid Loess Plateau region, characterised by fragile ecosystems and severe soil erosion, is a key area for ecological restoration and protection in China. To illustrate water use characteristics and adaptation to drought in the main forests in this area, we monitored the xylem sap flow of two typical adjacent forest communities with similar climatic characters, a secondary natural forest dominated by oak (Quercus liaotungensis) and a pure plantation of black locust (Robinia pseudoacacia), during 2011–2019 using Granier‐type thermal dissipation probes. Solar radiation (RS), air temperature, relative humidity (RH), precipitation and soil water content (SWC) were measured simultaneously. Throughout the whole study period, the mean diameter at breast height (DBH) and total sapwood area increased by 4.5 cm and 1.10 m2 ha−1, respectively in the oak forest and by 1.0 cm and 0.22 m2 ha−1, respectively in the black locust plantation. The monthly stand transpiration was jointly determined by phenological and meteorological factors. At the annual timescale, transpiration of the oak stand was significantly correlated with potential reference evapotranspiration (ET0) and rainfall in the previous year, whereas a significant positive relationship was detected between stand transpiration and SWC in the black locust stand. The analyses of differences between dry and wet years showed that the oak forest exhibited significantly different parameters in the regression analysis of stand transpiration to vapour pressure deficit (VPD), whereas only one parameter was clearly distinct in the black locust plantation, suggesting that its transpiration status did not fully recover even in wet years. The management of black locust plantations with weakened growth conditions should be adjusted under prolonged drought conditions. In contrast, oak forest can maintain the water balance and stable growth by efficiently controlling stomatal behaviour. [ABSTRACT FROM AUTHOR]

Robinia pseudoacacia flowers have attracted much attention because of numerous bioactivities. In this study, its extract showed the potential scavenging ability for 2,2′‐azinobis‐(3‐ethylbenzthiazoline‐6‐sulphonate) and 1,1‐diphenyl‐2‐picrylhydrazyl free radicals. Under the guidance of antioxidant activity, the antioxidant extract was enriched by liquid‐liquid extraction. The partition coefficients of the two main components in antioxidant extracts differed greatly, so in this study, elution‐extrusion counter‐current chromatography with the solvent system of n‐hexane‐ethyl acetate‐methanol‐water (2.5:5:2.5:5, v/v) was used to enhance the separation efficiency, and the two main components were successfully obtained. Among them, kaempferol showed strong antioxidant activity, which can be responsible for the activity of the extract. In order to deeply understand the antioxidant mechanism of kaempferol, the thermodynamics, frontier molecular orbital, and kinetics of scavenging free radicals were investigated by density functional theory. The results showed that 4′‐OH in kaempferol was the most active group, which can scavenge free radicals by hydrogen atom transfer in non‐polar solvents and activate 3‐OH to generate double hydrogen atom transfer in the gas phase. But in polar solvents, it was more inclined to clear radicals through single electron transfer and proton transfer. The kinetic result showed that kaempferol needed 9.17 kcal/mol of activation energy to scavenge free radicals. [ABSTRACT FROM AUTHOR]

Planted vegetation is considered one of the most important soil‐forming factors in the reclamation of degraded post‐mining lands for forestry. The objective of this study was to compare the effect of N‐fixing tree species and non‐N‐fixing tree species on the organic phosphorus (Porg) forms in technosols developing from various substrates. Samples were taken from the uppermost layer (depth 0–5 cm) of technosols afforested with black locust (Robinia pseudoacacia), black alder (Alnus glutinosa), silver birch (Betula pendula), and scots pine (Pinus sylvestris). Samples of the tree foliage and the O‐horizons were taken as well. The studied technosols developed from Quaternary sands (sands), fly ashes after lignite combustion (ashes), and Miocene clays (clays). The soil samples were measured for the contents of labile (POlab) and moderately labile organic phosphorus (POmod), phosphorus contained in fulvic and humic acids (Pfulv and Phum, respectively), and residual organic phosphorus (POres). The foliage and O‐horizon samples were measured for the concentrations of C, N, and P. The N‐fixing tree species had higher P concentration in their foliage than non‐N‐fixing tree species. However, in the O‐horizon, the highest P concentration was determined under birch and not under N‐fixers. The effect of tree species on the organic P (Porg) concentrations in the mineral soil was limited with significantly lower Porg concentrations under pine. The soil under this species contained less Pfulv, Phum, and POres. However, the percentages of POlab, POmod, Pfulv, Phum, and POres in soil Porg were nearly the same under all tree species. The largest effect on the Porg concentration and the contents of particular Porg fractions was from the substrate type. Sands contained much less Porg than the clays and ashes, but their percentage of POlab in Porg was much higher than in the two other substrates. We conclude that N‐fixing trees do not affect the concentration of labile organic P, and the major factor controlling this Porg fraction is the soil substrate quality. [ABSTRACT FROM AUTHOR]

In water‐limited ecosystems, soil water regulates root water uptake (RWU) strategies. However, RWU responses to soil water changes under different species are not well‐understood. We assessed RWU responses of three revegetation species [shrub (Hippophae rhamnoides Linn.), coniferous forest [Platycladus orientalis (L.) Franco], and broad‐leaved forest (Robinia pseudoacacia L.) during the dry (May to June) and rainy (July to August) seasons in 2020 on the Loess Plateau using stable isotope methods. We sampled soil and xylem for each species at approximately weekly intervals and used the MixSIAR model to quantify RWU contribution with stable water isotopes. The results indicated that soil water in the shallow (0–40 cm) and middle (40–200 cm) soil layers fluctuated more strongly than the deep soil layer (200–300 cm) due to precipitation and evapotranspiration. Before precipitation in the dry season, most of the RWU for H. rhamnoides and R. pseudoacacia (97% and 98%) came from the middle layer under limited soil water. After precipitation in the dry season, the three species had similar RWU responses to soil water changes. After precipitation in the rainy season, the RWU change of H. rhamnoides and R. pseudoacacia with deep soil drying was more sensitive to soil water change than P. orientalis with sufficient deep water on August 3 and 11, while, the RWU of H. rhamnoides was more sensitive to soil water change than R. pseudoacacia on August 11 and 19. Thus, by switching its water‐use strategy, H. rhamnoides adapted better to the soil water environment than P. orientalis and R. pseudoacacia. This finding will help in selecting the optimal revegetation species for water use in a changing climate environment. [ABSTRACT FROM AUTHOR]

Symbiotic nitrogen fixation (SNF) is a key ecological process whose impact depends on the strategy of SNF regulation—the degree to which rates of SNF change in response to limitation by N versus other resources. SNF that is obligate or exhibits incomplete downregulation can result in excess N fixation, whereas a facultative SNF strategy does not. We hypothesized that tree‐based SNF strategies differed by latitude (tropical vs. temperate) and symbiotic type (actinorhizal vs. rhizobial). Specifically, we expected tropical rhizobial symbioses to display strongly facultative SNF as an explanation of their success in low‐latitude forests. In this study we used 15N isotope dilution field experiments in New York, Oregon, and Hawaii to determine SNF strategies in six N‐fixing tree symbioses. Nitrogen fertilization with +10 and +15 g N m−2 year−1 for 4–5 years alleviated N limitation in all taxa, paving the way to determine SNF strategies. Contrary to our hypothesis, all six of the symbioses we studied sustained SNF even at high N. Robinia pseudoacacia (temperate rhizobial) fixed 91% of its N (%Ndfa) in controls, compared to 64% and 59% in the +10 and +15 g N m−2 year−1 treatments. For Alnus rubra (temperate actinorhizal), %Ndfa was 95%, 70%, and 60%. For the tropical species, %Ndfa was 86%, 80%, and 82% for Gliricidia sepium (rhizobial); 79%, 69%, and 67% for Casuarina equisetifolia (actinorhizal); 91%, 42%, and 67% for Acacia koa (rhizobial); and 60%, 51%, and 19% for Morella faya (actinorhizal). Fertilization with phosphorus did not stimulate tree growth or SNF. These results suggest that the latitudinal abundance distribution of N‐fixing trees is not caused by a shift in SNF strategy. They also help explain the excess N in many forests where N fixers are common. [ABSTRACT FROM AUTHOR]

Transpiration (Tr) is the largest continental water flux. Tr is jointly affected by biophysical factors, including atmospheric demand, soil water supply, and plant physiological features, represented by potential evapotranspiration (PET), soil water content (SWC), and leaf area index (LAI) respectively. Disentangling the independent and interacting impacts of the biophysical factors on Tr provides a better understanding on the mechanism of ecohydrological controls on forest water use. In this study, taking the black locust plantation of the Loess Plateau as an example, independent contributions of the three factors and their interactions on Tr were quantified based on field observation, model development, and factorial analysis. First, sapflow density, meteorological variables, SWC, and LAI were observed during five growing seasons. Second, a coupled Tr model (R2 = 0.85, RMSE = 5.92) was established by the long‐term observed data of Tr, PET, SWC, and LAI. Finally, factorial experiment analysis showed that contributions of LAI, PET, and SWC and their interactions (PET×LAI, LAI × SWC, and PET×SWC) on Tr accounted for 50.82%, 9.77%, 9.30%, 13.88%, 13.75%, and 2.47%, respectively. The results indicated that LAI and PET×LAI had the largest independent and interacting impact on Tr of black locust. This study suggested that regulation of canopy leaf area through forest cultivation practices could reduce forest water use, which was beneficial for soil desiccation mitigation and meeting the soil water capacity for vegetation in this region. This study also provided a methodological reference for disentangling the impacts of biophysical factors on forest transpiration. [ABSTRACT FROM AUTHOR]

Solute transport behaviour can indicate the efficiency of eco‐hydrological responses. However, this behaviour has not been consider for use in assessing the health of wetland ecosystems. We assessed solute transport behaviour in degraded wetland soils using 72 undisturbed soil columns located in Robinia pseudoacacia (tree) and Tamarix chinensis (bush) communities. Soil column tracer experiments were conducted under the same initial and boundary conditions using Brilliant Blue FCF as a conservative tracer. Solute transport behaviour at a soil column scale was described by four measures: steady infiltration rate of effluents, concentration of effluents, dye staining patterns and cumulative effluents leaching. Numerical modelling by the dual‐permeability model in HYDRUS‐1D was used to simulate the proportion of cumulative effluents leaching from soil macropores. These data showed that steady infiltration rate of effluents at the tree site decreased with increasing soil depth (5.742, 0.716, 0.657, and 0.458 ml/min) but at the bush site first increased and then subsequently decreased with increasing soil depth (0.336, 0.548, 0.974 and 0.379 ml/min). The concentration of effluents at the tree site (0.583, 0.149, 0.147 and 0.067 g/L) and the bush site (0.281, 0.109, 0.161 and 0.053 g/L) decreased nonlinearly with increasing soil depth. Dye staining patterns were significantly different between different soil locations. The largest dark blue staining domains were from 0 to 10 cm soil depths at the tree site and 20–40 cm depths at the bush site. The proportion of cumulative effluents leaching from soil macropores ranged from 37.6% to 61.1% at the tree site and ranged from 0% to 99.9% at the bush site. Understanding the solute transport behaviour in the Yellow River Delta is the first step towards the restoration of degraded wetlands. [ABSTRACT FROM AUTHOR]

Vegetation and soil surveys were made within three mixed forests and four monoculture forests on opencast coal mine spoils in the Loess Plateau (China) to reveal the tree species effect on reclaimed mine soil (RMS) and carbon (C) sequestration. Results showed that tree biomass, annual litter biomass, and reserved litter biomass varied among forests, with Robinia pseudoacacia L.‐Pinus tabuliformis Carr. recording the highest tree biomass, leaf C, and leaf nitrogen (N) values. The greatest C and N contents in RMS were recorded in the R. pseudoacacia ‐ P. tabuliformis forest in both small macroaggregate (250–2000 μm) and large macroaggregate (>2000 μm) fractions. However, no significant differences among forests were observed in microaggregate (53–250 μm) and silt+clay (<53 μm) associate C and N. Significant positive correlations were observed among soil C and vegetation biomass and vegetation biomass associated C. It was in line with the C isotope analysis, which indicated that C flowed in the order: leaf→litter/root→soil macroaggregate→soil microaggregate/silt+clay. Moreover, negative correlations between soil C and soil δ15N in large and small macroaggregate fraction were recorded, indicating C sequestration in macroaggregate was potentially associated with soil N cycling. Overall, Tree species effect on soil C sequestration was derived from the amount and quality of the vegetation biomass and it was mediated by soil N cycling to some extent. R. pseudoacacia ‐ and P. tabuliformis mixed forest could be proposed as a favourable reclamation choice, due to these species prominent C sequestration ability. [ABSTRACT FROM AUTHOR]

Many studies have demonstrated the importance of rhizosphere microorganisms to soil nutrient cycling and plant stress resistance. However, we still lack a comprehensive understanding of the potential relationship between rhizosphere microbial diversity and soil multifunctionality during forest vegetation restoration. In this study, the diversity, assembly processes, and co‐occurrence patterns of rhizosphere microbial communities were explored along a 45‐year chronosequence of Robinia pseudoacacia plantations in China's Loess Plateau region. Soil multifunction index was calculated based on 11 measured available nutrient properties. The results showed that both α‐ and β‐diversities of rhizosphere microbial communities were significantly correlated with the soil multifunction index. Stochastic processes dominated rhizosphere microbial community assembly. Correlations between the abundances of sensitive operational taxonomic units for different forest ages (i.e. 15, 25, 35, and 45 years old) and soil multifunctional index varied in distinct network modules, being positive in module 1 and negative in module 2. There was a positive correlation between microbial network complexity (e.g. degree) and soil multifunctional index. The contribution of rhizosphere core microbiota to soil multifunctional index was higher than that of non‐core microbiota. To sum up, plantation vegetation restoration enhances the relationship between microbial diversity and soil multifunctionality, while affecting microbial co‐occurrence patterns in the rhizosphere. [ABSTRACT FROM AUTHOR]

One of the suggested mechanisms behind the success of non‐native plants in recipient ecosystems is competition avoidance with natives by means of different resource‐use strategies, such as deeper water uptake under dry conditions.We aimed at evaluating water source partitioning between native and non‐native tree species coexisting in central Spain floodplains; determining the dependency on drought stress of such water sources use; and assessing if the reliance on deeper water sources relates with physiological and growth performance.We assessed water uptake depth, leaf functional traits related to physiological performance and growth of native (Populus alba) and non‐native trees (Ailanthus altissima, Robinia pseudoacacia) coexisting in riparian forests under different drought conditions (drier, intermediate and wetter). We analysed δ2H and δ18O isotopes in xylem water and in soil water from top, mid and deep soil depths and determined the contribution of each water source to overall plant xylem water. Leaf traits related with resource use and secondary growth were assessed for each species.We found stronger differences between sites than between species, with all species taking more deep water in the driest site (~45% of the xylem water) than in the wettest (~15%). However, under drier conditions, species differences were significant for top‐soil water use, with R. pseudocacia withdrawing more superficial water (~22%) than A. altissima (~8%). These results indicate stronger water partitioning under drier conditions. Non‐native species showed a physiological strategy characterized by greater leaf N, water content, and enriched δ13C and δ15N values independently of the deep‐water uptake. However, a positive relationship between deep soil water use and such strategy was found for P. alba.We highlight that those native and non‐native species differences were more evident regarding physiological performance at leaf level than for deep‐water uptake or growth. Furthermore, our results suggest that differences in water sources used by coexisting species may increase under drier conditions. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Biotic resistance from post‐dispersal seed predators has been shown to influence invasion and spread of woody plants in grasslands and savannas. Yet, the role of rodent granivores as a barrier to woody plant invasion remains poorly studied. We examined the impact of rodent exclusion and canopy disturbance on two exotic tree seedling establishment (Gleditsia triacanthos and Robinia pseudoacacia) in an old‐field grassland of the Inland Pampa, Argentina. The experiment was conducted over 4 years with substantial climatic variation, which affected both rodent abundance and seedling performance. Our results showed that, for both tree species, rainfall was the main factor affecting both seedling emergence and survival, while the effect of rodent seed predation and disturbance depended on variability in natural rodent density. The response of G. triacanthos seedling emergence after the onset of favorable water conditions was more rapid than the recovery of rodent populations. This delay provided an opportunity to escape from potential seed predation, reducing its importance as a biotic filter to woody invasion. Robinia pseudoacacia seedlings emerged during the first growing period and died because of hydric stress, while remnant seeds did not remain viable in the seed bank after 2 years of sowing. From our results, we suggest that the dynamic of tree invasion depends highly on climatic variability, which has direct effects on seed germination and survival, as well as effects mediated by rodent abundance and herbaceous competition. [ABSTRACT FROM AUTHOR]

Planting Robinia pseudoacacia in water‐limited regions can promote soil and water conservation and ecological service functions. However, it can cause the formation of below ground dried soil layers (DSLs), causing land degradation and tree mortality. To ascertain the spatial–temporal dynamics and recovery processes of DSLs, we monitored the deep soil water content (SWC) to a depth of 500 cm at 27 sites on a typical R. pseudoacacia forest from 2017 to 2020 and calculated the evaluation indices of DSLs based on plant‐available SWC (PASWC) and stable field capacity (SFC). Compared with PASWC‐identified DSLs, the degree of SFC‐identified DSLs was more severe, although the spatial–temporal characteristics were similar. Severe soil desiccation was identified as 79% of the 500 cm profile dried out below 101 cm. The mean thickness of DSL and mean SWC within a DSL were 396 cm and 9.0%, respectively, and the quantitative index reached Grade III (severe) DSLs. All DSL indices demonstrated weak or moderate variability in space and strong variability in time. The heterogeneity of rainfall events and microtopographic positions explain the spatial–temporal variation of DSL indices well. A heavy rainfall event (>50 mm) triggered the disappearance of DSLs at some sites, indicating the possibility of DSLs recovery based on field observations under natural condition. Microtopography (such as the swales) provides advantageous conditions to the recovery of DSLs by redistributing rainfall flow at the local scale. These results provide insights into DSLs recovery, which is useful for land development and rehabilitation in planted forests. [ABSTRACT FROM AUTHOR]

Nitrogen‐fixing root nodules are formed by symbiotic association of legume hosts with rhizobia in nitrogen‐deprived soils. Successful symbiosis is regulated by signals from both legume hosts and their rhizobial partners. HmuS is a heme degrading factor widely distributed in bacteria, but little is known about the role of rhizobial hmuS in symbiosis with legumes. Here, we found that inactivation of hmuSpSym in the symbiotic plasmid of Mesorhizobium amorphae CCNWGS0123 disrupted rhizobial infection, primordium formation, and nitrogen fixation in symbiosis with Robinia pseudoacacia. Although there was no difference in bacteroids differentiation, infected plant cells were shrunken and bacteroids were disintegrated in nodules of plants infected by the ΔhmuSpSym mutant strain. The balance of defence reaction was also impaired in ΔhmuSpSym strain‐infected root nodules. hmuSpSym was strongly expressed in the nitrogen‐fixation zone of mature nodules. Furthermore, the HmuSpSym protein could bind to heme but not degrade it. Inactivation of hmuSpSym led to significantly decreased expression levels of oxygen‐sensing related genes in nodules. In summary, hmuSpSym of M. amorphae CCNWGS0123 plays an essential role in nodule development and maintenance of bacteroid survival within R. pseudoacacia cells, possibly through heme‐binding in symbiosis. Summary Statement: We characterize the hmuSpSym gene located in the symbiotic plasmid of Mesorhizobium amorphae CCNWGS0123 that participates in symbiosis with Robinia pseudoacacia. Inactivation of hmuSpSym underpins damaged symbiotic phenotypes and necrotic bacteroids, which potentially affects symbiosis via HmuSpSym as a heme‐binding factor. [ABSTRACT FROM AUTHOR]

Carbon uptake by the terrestrial biosphere depends on supplies of new nitrogen (N) from symbiotic N fixation, but we lack a framework for scaling fixation accurately and for predicting its response to global change.We scaled symbiotic N fixation from individual N fixers (i.e. plants that host N‐fixing bacteria), by quantifying three key parameters—the abundance of N fixers, whether they are fixing N and their N fixation rates. We apply this framework to black locust, a widespread N‐fixing tree in temperate forests of the eastern United States, and harness long‐term data from southern Appalachian forests to scale fixation from trees to the landscape and over succession.Symbiotic N fixation at the landscape scale peaked in the first decade following forest disturbance, and then declined. This pattern was due to the declining density and declining fixation rates of individual black locust trees over succession. Independent of forest succession, and coincident with chronic atmospheric N deposition, we have evidence suggesting that nodule biomass produced by black locust trees has declined by 83% over the last three decades. This difference in nodule biomass translates to a maximum fixation rate of 11 kg N ha−1 year−1 and a landscape average of 1.5 kg N ha−1 year−1 in contemporary forests.Synthesis. We find key controls on symbiotic N fixation by black locust over space and time, suggesting lower fixation rates in eastern deciduous forests than previous estimates. Our scaling framework can be applied to other N fixers to aid predictions of symbiotic N fixation and ecosystem response to global change. [ABSTRACT FROM AUTHOR]

The chemical traits of litter are among the most critical factors that affect its decomposition. During vegetation restoration of planted forests, increasing age of the planted species and succession of the understory species may lead to significant changes in litter traits. However, it is unclear how these changes occur and how they affect litter decomposition. Therefore, we studied the decomposition of litter from four Robinia pseudoacacia plantations in the Loess Plateau in China with stand ages of 10–43 years using an indoor simulation test. We measured changes in litter substrate quality and chemical diversity, structural properties of the litter microbial community, activity of litter enzymes, and mixed decomposition effects during vegetation restoration. Their relationships to changes in litter decomposition rate were analyzed using structural equation modeling. Improvements in substrate quality of forest litter induced by vegetation restoration drove changes in fungal community composition during late decomposition (day 358), which in turn increased the activity of lignin‐decomposing enzymes and ultimately accelerated litter decomposition. At the same time, decreases in the chemical diversity of forest litter induced by vegetation restoration reduced the diversity of litter fungi during middle and late decomposition (days 182 and 358). This caused significant negative mixed decomposition effects, thereby inhibiting litter decomposition. However, improvements in litter substrate quality dominated the changes in litter decomposition rate, and the decomposition rate of R. pseudoacacia plantation litter thus increased over the course of vegetation restoration. [ABSTRACT FROM AUTHOR]

Variations in soil chemical composition may lead to disturbances in plant growth and survival. Which strategies of biomass allocation fast-growing species acquire to overcome the disturbances in the rhizosphere remains an open research challenge. We conducted a series of greenhouse pot experiments to collect enough experimental evidence to elucidate the answer. A tiered analytical approach was applied to collected data to fingerprint both the intraspecies and interspecies differences. We investigated the biomass allocation patterns in Robinia pseudoacacia L., Populus x euramericana, Populus deltoides, Salix alba, Salix matsudana Koidz., and Salix viminalis L. (18 fast-growing genotypes in total) under cadmium-free and cadmium-perturbed soil conditions. Further, we explored the intraspecific and interspecific differences between tested plants and looked for different strategies employed under perturbed conditions. We show that fast-growing species tend to strengthen their roots toward the Cd triggered perturbances in the rhizosphere and allocate more biomass to that plant organ/part. Intraspecies analyses pointed to differences in resource use efficiency and acquisition strategy based on specific leaf area, pointing toward P. deltoides genotypes PE19/66 and PD3, and S. alba B44 as strong, fast-growing oriented genotypes. Others exhibited more or less a conservative resource use and acquisition strategy under perturbed conditions. Our study highlights the intraspecies and interspecies specificity of fast-growing species to Cd occurrence in the rhizosphere. Association of growth traits and Cd-related traits tested with structural equation model highlighted the shoots bioconcentration index as a proxy-trait which directly interplay with the functional traits performance and modify the biomass shift. [ABSTRACT FROM AUTHOR]

The present study explores the interaction of water supply and rhizobia inoculation on CO2 and H2O gas exchange characteristics, physiological and biochemical traits in seedlings of Robinia pseudoacacia L. originating from two provenances with contrasting climate and soil backgrounds: the Gansu Province (GS) in northwest China and the Dongbei region (DB) of northeast China. Rhizobia strains were isolated from the 50-years old Robinia forest sites grown in the coastal region of east China. Robinia seedlings with and without rhizobia inoculation were exposed to normal water supply, moderate drought, and rewatering treatments, respectively. After 2 weeks of drought treatment, photosynthetic and physiological traits (net photosynthetic rate, stomatal conductance, stable isotope signature of carbon, malondialdehyde and hydrogen peroxide content) of Robinia leaves were significantly altered, but after rewatering, a general recovery was observed. Rhizobia inoculation significantly increased the drought resistance of both Robinia provenances by promoting photosynthesis, increasing the foliar N content and reducing the accumulation of malondialdehyde and hydrogen peroxide. Among the two provenances, DB plants developed more nodules than GS plants, but GS plants were more drought-tolerant than DB plants, both inoculated or noninoculated, indicated by the foliar gas exchange parameters and biochemical traits studied. Our results also show that inoculation of rhizobia could significantly improve the drought resistance of Robinia in both provenances. The present study contributes to the scientific background for the selection of drought-resistant varieties of Robinia to ensure the success of future afforestation projects in degraded terrestrial ecosystems under global climate change. [ABSTRACT FROM AUTHOR]

Short rotation coppice plays an important role for biomass production. Mixing fast‐growing tree species in short rotation coppices may lead to overyielding if the species have complementarity traits. The goal of this study is to analyze biomass yield of eight different poplar hybrids and black locust in mixed short rotation coppice after a rotation of 5 years. Pure and mixed stands were established at two sites of contrasting fertility as a low‐input system. After collecting a sample of trees for the data set, we fitted allometric equations to estimate the overall biomass of the stands. All poplar genotypes showed lower performance in mixtures with black locust, whereas the latter profited from the mixture. In contrast to our expectations, poplars had no advantages from black locust's nitrogen enrichment of the soil. Instead, the dominance and competitiveness of black locust drove to poorer performance of all eight poplar genotypes across both sites. Mixing fast‐growing tree species in short rotation coppices may lead to overyielding if the species have complementarity traits. The goal of this study is to analyze biomass yield of eight different poplar hybrids and black locust in mixed short rotation coppice after a rotation of 5 years. While black locusts profited from mixed cropping, poplars had no advantaged performance. The dominance and competitiveness of black locust drove to poorer performance of all eight poplar genotypes. [ABSTRACT FROM AUTHOR]

Local adaptation and the evolution of phenotypic plasticity may facilitate biological invasions. Both processes can enhance germination and seedling recruitment, which are crucial life‐history traits for plants. The rate, timing and speed of germination have recently been documented as playing a major role during the invasion process. Black locust (Robinia pseudoacacia L.) is a North American tree, which has spread widely throughout Europe. A recent study demonstrated that a few populations are the source of European black locust. Thus, invasive populations can be compared to native ones in order to identify genetic‐based phenotypic differentiation and the role of phenotypic plasticity can thereby be assessed.A quantitative genetics experiment was performed to evaluate 13 juvenile traits of both native and invasive black locust populations (3000 seeds, 20 populations) subjected to three different thermal treatments (18 °C, 22 °C and 31 °C).The results revealed European populations to have a higher germination rate than the native American populations (88% versus 60%), and even when genetic distance between populations was considered. Moreover, this trait showed lower plasticity to temperature in the invasive range than in the native one. Conversely, other studied traits showed high plasticity to temperature, but they responded in a similar way to temperature increase: the warmer the temperature, the higher the growth rate or germination traits values.The demonstrated genetic differentiation between native and invasive populations testifies to a shift between ranges for the maximum germination percentage. This pattern could be due to human‐mediated introduction of black locust. [ABSTRACT FROM AUTHOR]

Soil moisture is essential for vegetation restoration in arid and semi‐arid regions. Ascertaining the vertical distribution and transportation of soil moisture under different vegetation types has a profound effect on the ecological construction. In this study, the soil moisture at a depth of 500 cm for four typical vegetation types, including Robinia pseudoacacia, Caragana korshinskii, Stipa bungeana, and corn, were investigated and compared in the Zhifanggou watershed of the Loess plateau. Additionally, hydrogen and oxygen stable isotopes were detected to identify the transport mechanism of soil moisture. The results showed vertical distribution and transportation of soil moisture were different under different vegetation types. Depth‐averaged soil moisture under S. bungeana and corn generally increased along the profile, while C. korshinskii and R. pseudoacacia showed weakly increasing and relatively stable after an obvious decreasing trend (0–40 cm). The soil moisture under R. pseudoacacia was lower than that under other vegetation types, especially in deep layer. However, the effect of R. pseudoacacia on soil moisture in the topsoil (< 30 cm) could be positive. For R. pseudoacacia (160–500 cm), C. korshinskii (0–500 cm), and S. bungeana (0–100 cm), the soil moisture declined with increased in vegetation age. Planting arbor species such as R. pseudoacacia intensified the decline of soil moisture on the Loess Plateau. The capacity of evaporation fractionation of soil moisture followed the sequence: corn > S. bungeana > R. pseudoacacia > C. korshinskii. The δ18O values in soil water fluctuated across the profile. The δ18O values changed sharply in upper layer and generally remained stable in deep layer. However, in middle layer, the vertical distribution characteristics of the δ18O values were different under different vegetation types. We estimated that piston flow was the main mode of precipitation infiltration, and the occurrence of preferential flow was related to vegetation types. These results were helpful to improve the understanding of the response of deep soil moisture to vegetation restoration and inform practices for sustainable water management. [ABSTRACT FROM AUTHOR]

Aim: Exploring the biotic homogenization and diversity resistance hypotheses by assessing the effect of non‐native black locust canopy on understorey species turnover. Location: Berlin, the Venetian metropolitan area, and Rome. Methods: We modelled the zeta (ζ) expression of diversity to compare the understorey species turnover between the non‐native black locust and native woodland canopies across multiple sites and through predictors of anthropogenic pressure (road and built‐up density) and interior conditions (tree basal area and mean height). Results: In Rome, black locust showed the lowest survivability and cover and did not produce any homogenization of the understorey. In Berlin and in the Venetian metropolitan area, black locust caused understorey homogenization, although with a lower intensity in Berlin. Under black locust canopies, distance between sites and road density was more consistently associated with species turnover, across urban areas and multiple sites. Under native canopies in Berlin, factors prominently associated with species turnover were road and built‐up density and mean tree height, while in the Venetian metropolitan area it was road density. Main conclusions: Evidence in support of the biotic homogenization in contrast to the diversity resistance hypothesis varied across urban areas. Species turnover was influenced by land use patterns more evidently under native tree canopies and where the non‐native tree had higher survivability. Similar analyses in other urban areas may confirm these relationships with other types of landscapes. [ABSTRACT FROM AUTHOR]

In this study, materials from stem, branches and bark of three native forest species from the Mediterranean region – Turkish pine (Pinus brutia Ten.), black pine (Pinus nigra L.), and black locust (Robinia pseudoacacia L.) – were harvested from marginal lands in north Greece, and were thoroughly characterized on the basis of their physical properties, combustion characteristics, chemical composition, and ash elemental analysis. The potential of these fast‐growing, drought‐tolerant species to function as sustainable feedstock for solid biofuel production has been proven to be high, with black pine showing the strongest potential. The materials, especially stems and branches, presented low moisture and ash content, and high calorific value attributed to high lignin content, in comparison with species grown on conventional lands. The ashes, being produced from processed materials, mainly consist of Ca, K, S, and P as major elements, while their toxic element contents are negligible, increasing the potential for the ash to be utilized in fertilization. © 2021 Society of Industrial Chemistry and John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Forests are a significant CO2 sink. However, CO2 sequestration in forests is radiatively offset by emissions of nitrous oxide (N2O), a potent greenhouse gas, from forest soils. Reforestation, an important strategy for mitigating climate change, has focused on maximizing CO2 sequestration in plant biomass without integrating N2O emissions from soils. Although nitrogen (N)‐fixing trees are often recommended for reforestation because of their rapid growth on N‐poor soil, they can stimulate significant N2O emissions from soils. Here, we first used a field experiment to show that a N‐fixing tree (Robinia pseudoacacia) initially mitigated climate change more than a non‐fixing tree (Betula nigra). We then used our field data to parameterize a theoretical model to investigate these effects over time. Under lower N supply, N‐fixers continued to mitigate climate change more than non‐fixers by overcoming N limitation of plant growth. However, under higher N supply, N‐fixers ultimately mitigated climate change less than non‐fixers by enriching soil N and stimulating N2O emissions from soils. These results have implications for reforestation, suggesting that N‐fixing trees are more effective at mitigating climate change at lower N supply, whereas non‐fixing trees are more effective at mitigating climate change at higher N supply. [ABSTRACT FROM AUTHOR]