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Although effects of atmospheric nitrogen (N) deposition on forest plants have been widely investigated, N interception and absorption effects by forest canopy should not be neglected. Moreover, how N deposition change the molecular biological process of understory dominant plants, which was easily influenced by canopy interception so as to further change physiological performance, remains poorly understood. To assess the effects of N deposition on forest plants, we investigated the effects of understory (UAN) and canopy N addition (CAN) on the transcriptome and physiological properties of Ardisia quinquegona, a dominant subtropical understory plant species in an evergreen broad-leaved forest in China. We identified a total of 7394 differentially expressed genes (DEGs). Three of these genes were found to be co-upregulated in CAN as compared to control (CK) after 3 and 6 h of N addition treatment, while 133 and 3 genes were respectively found to be co-upregulated and co-downregulated in UAN as compared to CK. In addition, highly expressed genes including GP1 (a gene involved in cell wall biosynthesis) and STP9 (sugar transport protein 9) were detected in CAN, which led to elevated photosynthetic capacity and accumulation of protein and amino acid as well as decrease in glucose, sucrose, and starch contents. On the other hand, genes associated with transport, carbon and N metabolism, redox response, protein phosphorylation, cell integrity, and epigenetic regulation mechanism were affected by UAN, resulting in enhanced photosynthetic capacity and carbohydrates and accumulation of protein and amino acid. In conclusion, our results showed that the CAN compared to UAN treatment had less effects on gene regulation and carbon and N metabolism. Canopy interception of N should be considered through CAN treatment to simulate N deposition in nature. [ABSTRACT FROM AUTHOR]

Mycorrhizal types are a predictive framework for nutrient cycling within and across ecosystems, and their types represent different nutrient-acquisition strategies for plants. Carbon (C), nitrogen (N) and phosphorus (P) stoichiometric ratios are essential for understanding biogeochemical processes. The purpose of this study was to reflect the balance in the process of plant resource acquisition by exploring the C, N and P stoichiometric ratios (C/N, N/P, and C/P) in shrub organs in different mycorrhizal types. In this study, the C, N, and P stoichiometric ratios in leaves, stems and roots were analyzed in the types of arbuscular mycorrhizal (AM), ectomycorrhizal (ECM) and AM + ECM of shrubs in Northern China. The results showed that C/N in the stems and roots of AM plants (95.75 and 81.42) was significantly lower than in AM + ECM plants (109.89 and 102.37) and ECM plants (107.67 and 96.93), while both N/P and C/P in the leaves, stems and roots of AM shrubs (38.67, 36.17, 40.69; 1028.14, 2989.13, and 2659.18) were significantly higher than in ECM shrubs (30.52, 22.31, 20.47; 796.51, 2208.28, and 1714.95). Moreover, different elements among the same plant organs were closely correlated, and the same pattern was found among the same element ratios among different plant organs. This suggests that mycorrhizal type can influence C, N and P ratios among different organs. [ABSTRACT FROM AUTHOR]

Of all forest biomes, boreal forests are experiencing the most significant warming. Drought caused by warming has a dramatic impact on species in boreal forests. However, little is known about whether the growth of trees and shrubs in boreal forests responds consistently to warming and drought. We obtained the tree-ring width data of 308 trees (Larix gmelinii and Pinus sylvestris var. mongolica) and 133 shrubs (Pinus pumila) from 26 sites in northeastern China. According to the climate data from 1950 to 2014, we determined three extreme drought years (1954, 1967, and 2008). The response difference of radial growth of trees and shrubs in boreal forests to drought was compared using resilience index, moving correlation and response analysis. The results showed that high temperature (mean and maximum temperature) in previous and current growing seasons promoted the growth of P. pumila , but inhibited the growth of trees. On the contrary, wetter conditions (higher PDSI) promoted tree growth but were not conducive to P. pumila growth in high latitudes. Moving correlation analysis showed similar results. In addition, water deficit was more likely to inhibit P. pumila growth in low latitudes. The drought resistance of P. pumila was stronger than that of L. gmelinii and P. sylvestris var. mongolica. Therefore, the growth loss and recovery time of P. pumila during drought was less than those of trees. We concluded that L. gmelinii and P. sylvestris var. mongolica are more prone to growth decline than P. pumila after the drought caused by climate warming. In the future climate warming, shrub growth may benefit more than trees. Our findings are of great significance in predicting the future changes in ecosystem composition and species distribution dynamics in extreme climate susceptible areas. [ABSTRACT FROM AUTHOR]

Recent temperature rise caused by human activities has led to profound changes in the forest ecosystem. Shrubs play an important role in the boreal forest. However, it is not clear how shrub growth responds to climate change, especially whether there is a difference in the response of shrub at different altitudes to climate change. Here, we developed three ring-width chronologies of Pinus pumila along an altitudinal gradient in the Aokelidui Mountains, northeast China, then analyzed the relationship between the growth of P. pumila and climate at different altitudes. The results showed that the radial growth of P. pumila at low altitude had more prominent climate signals than those at medium and high altitude and was more sensitive to climate change. The chronological similarity was the highest in low and middle altitudes (72.5%, p < 0.01). Summer temperature had a significant negative effect on the growth of shrubs, and summer precipitation was conducive to the formation of wider rings at medium altitude. The warmer winter of the previous year favored P. pumila growth at low and medium altitudes but just the opposite at high altitudes. After rapid warming, the negative correlation between temperature and P. pumila growth in the growing season changed to a positive correlation at high altitude. On the contrary, the relationship between precipitation and P. pumila growth in the growing season changed from a positive to a negative correlation. We also found that the sensitivity of the growth of P. pumila to the Standardized Precipitation Evapotranspiration Index (SPEI) has gradually increased at medium-altitude since the 1980s. Therefore, in recent decades, the effect of moisture on the radial growth of shrub has become more and more important at medium altitudes. At the same time, the temperature rise was beneficial to the growth of P. pumila at low altitude. Our results suggest that the treeline advancement in this area is unlikely to occur in the near future since the shrub at high altitudes is not sensitive to climate warming. [ABSTRACT FROM AUTHOR]

Asymmetric responses of aboveground net primary productivity (ANPP) to precipitation were identified as a signal to predict ecosystem state shifts at temperate grassland zones in Inner Mongolia, China. However, mechanism studies were still lacking. This study hypothesized that the enhanced growth and newly emerged herbaceous after increased precipitation resulted in the highest asymmetry at the transition zone between desert and typical steppe. We monitored the responses of the normalized difference vegetation index (NDVI) of different species to precipitation events using un-manned aerial vehicle technology to test this hypothesis. NDVI and species richness were measured twice at fixed points in July and August with a time interval of 15 days. Results showed that: (1) From July to August, NDVI in the transition zone increased significantly after precipitation (P < 0.05), but NDVI in both the desert and typical steppe showed a non-significant change (P > 0.05). (2) In the transition zone, NDVI increases from the shrub and herbaceous contributed to 37 and 63% increases of the site NDVI, respectively. (3) There was a significant difference in species richness between July and August in the transition zone (P < 0.05), mainly caused by the herbaceous (Chenopodiaceae, Composite, Convolvulaceae, Gramineae, Leguminosae, and Liliaceae), which either emerged from soil or tillers growth from surviving plants. This study demonstrated that herbaceous dominant the changes of NDVI in the transition zone, which provides a scientific basis for the mechanism studies of ANPP asymmetric response to precipitation and warrants long-term measurements. [ABSTRACT FROM AUTHOR]

Background: Embankment dams were built south of the Laizhou bay in China for controlling storm surge disasters, but they are not enough to replace coastal forests in protecting the land. This study was designed to evaluate the effects of embankment dams on natural forests dominated by Tamarix austromongolica and test whether the dam-shrub system is a preferable updated defense., Methods: Coastal forests on two typical flats, one before and one behind embankment dams, were investigated using quadrats and lines. Land bareness, vegetation composition and species co-occurrence were assessed; structures of T. austromongolica populations were evaluated; and spatial patterns of the populations were analyzed using Ripley's K and K 1,2 functions., Results: In the area before embankment dams, 84.8% of T. austromongolica were juveniles (basal diameter ≤ 3 cm), and 15.2% were adults (basal diameter > 3 cm); behind the dams, 52.9% were juveniles, and 47.1 were adults. In the area before the dams, the land bareness was 13.7%, four species occurred, and they all were ready to co-occur with T. austromongolica ; behind the dams, the land bareness was 0%, and 16 species occurred whereas they somewhat resisted co-occurrence with T. austromongolica . In the area before the dams, the T. austromongolica population was aggregated in heterogeneous patches, and the juveniles tended to co-occur with the adults; behind the dams, they were over-dispersed as nearly uniform distributions, while the juveniles could recruit and were primarily independent of the adults. These results indicate that the T. austromongolica species did not suffer from the unnatural dams, but benefited somehow in population expansion and development. Overall, the T. austromongolica species can adapt to artificial embankment dams to create a synthetic defense against storm surges., Competing Interests: The authors declare there are no competing interests., (©2024 Yang et al.)

Variations of fine root production and turnover of the dominant shrubs associated with soil carbon (C) and nutrients are of key importance for evaluating desert ecosystem sustainability. Here we examined fine root production and turnover rate of Reaumuria songarica in Alxa steppe desert of northwestern China through sequential coring, ingrowth cores, and mesh‐bag methods, and then assessed soil C and nitrogen (N) stock and its correlation with fine root and leaf litter input. Results showed that fine root production and turnover rate were closely related to soil water content. Fine root production density and turnover rate of R. songarica were 386.8 g m−2 and 2.4 yr−1, respectively. Annually, fine root and leaf litter of R. songarica input 126.3 g C m−2 and 4.7 g N m−2 to soil. Soil organic C and N under shrub canopies increased substantially, which promoted the heterogeneity of soil properties and is considered as an important mechanism underlying the restoration of degraded sandy lands. [ABSTRACT FROM AUTHOR]

Caragana shrublands are the main type of vegetation in some cold desert ecosystems in Xinjiang in northwest China, and information on seed dormancy and germination of Caragana species is needed to help restore disturbed areas. Freshly matured seeds of Caragana aurantiaca, C. dasyphylla C. polourensis, C. roborovskyi, C. soongorica, C. spinosa and C. tekesiensis, collected from three natural ecosystems were tested for germination in light at 15/5, 20/10, 25/15 and 30/15 °C after dry storage at room temperature for 1 week and 9 months. Depending on the species, 1–84% of the seeds had physical dormancy (i.e., water-impermeable seeds). At 15/5, 20/10, 25/15 and 30/15 °C, fresh seeds of C. aurantiaca, C. spinosa and C. dasyphylla germinated from 74% to 100%, those of C. soongorica 15% to 52% and those of C. roborovskyi and C. polourensis 13–73%. After 9 months of storage, germination percentages increased significantly over wide range of temperatures for seeds of C. soongorica, C. tekesinsis C. roborovskyi and C. polourensis but decreased significantly for C. spinosa and C. dasyphylla. Most fresh seeds of the floodplain species and desert species are water-permeable and can germinate over a wide range of temperatures; consequently, they could be planted in the field at any time during the growing season. Dry storage of seeds of C. roborovski and C. tekesiensis increased the percentage of water-permeable seeds. Seeds of these species germinate best at high temperatures and should be planted in summer. If C. polourensis is used for restoration, the seeds need to be scarified before planting. [ABSTRACT FROM AUTHOR]

Background: Water stress seriously affects the survival of plants in natural ecosystems. Plant resistance to water stress relies on adaptive strategies, which are mainly based on plant anatomy with following relevant functions: (1) increase in water uptake and storage; (2) reduction of water loss; and (3) mechanical reinforcement of tissues. We measured 15 leaf-stem anatomical traits of five dominant shrub species from 12 community plots in the eastern Qaidam Basin to explore adaptive strategies based on plant leaf-stem anatomy at species and community levels. and their relationship with environmental stresses were tested., Results: Results showed that the combination of leaf-stem anatomical traits formed three types of adaptive strategies with the drought tolerance of leaf and stem taken as two coordinate axes. Three types of water stress were caused by environmental factors in the eastern Qaidam Basin, and the established adaptive strategy triangle could be well explained by these environmental stresses. The interpretation of the strategic triangle was as follows: (1) exploitative plant strategy, in which leaf and stem adopt the hydraulic efficiency strategy and safety strategy, respectively. This strategy is mostly applied to plants in sandy desert (i.e., Nitraria tangutorum, and Artemisia sphaerocephala) which is mainly influenced by drought stress; (2) stable plant strategy, in which both leaf/assimilation branches and stem adopt hydraulic safety strategy. This strategy is mostly applied to plants in salty desert (i.e., Kalidium foliatum and Haloxylon ammodendron) which aridity has little effect on them; and (3) opportunistic plant strategy, in which leaf and stem adopt hydraulic safety strategy and water transport efficiency strategy. This strategy is mostly applied to plants in multiple habitats (i.e., Sympegma regelii) which is mainly affected by coldness stress., Conclusion: The proposed adaptive strategy system could provide a basis for elucidating the ecological adaptation mechanism of desert woody plants and the scientific management of natural vegetation in the Qinghai-Tibet Plateau., (© 2024. The Author(s).)

Understanding the relative importance of the factors driving the patterns of biodiversity is a key research topic in community ecology and biogeography. However, the main drivers of plant species diversity in montane forests are still not clear. In addition, most existing studies make no distinction between direct and indirect effects of environmental factors and spatial constraints on plant biodiversity. Using data from 107 montane forest plots in Sichuan Giant Panda habitat, China, we quantified the direct and indirect effects of abiotic environmental factors, spatial constraints, and plant functional traits on plant community diversity. Our results showed significant correlations between abiotic environmental factors and trees (r =.10, p value =.001), shrubs (r =.19, p value =.001), or overall plant diversity (r =.18, p value =.001) in montane forests. Spatial constraints also showed significant correlations with trees and shrubs. However, no significant correlations were found between functional traits and plant community diversity. Moreover, the diversity (richness and abundance) of shrubs, trees, and plant communities was directly affected by precipitation, latitude, and altitude. Mean annual temperature (MAT) had no direct effect on the richness of tree and plant communities. Further, MAT and precipitation indirectly affected plant communities via the tree canopy. The results revealed a stronger direct effect on montane plant diversity than indirect effect, suggesting that single‐species models may be adequate for forecasting the impacts of climate factors in these communities. The shifting of tree canopy coverage might be a potential indicator for trends of plant diversity under climate change. [ABSTRACT FROM AUTHOR]

Aims Carbon (C), nitrogen (N) and phosphorus (P) stoichiometry strongly affect functions and nutrient cycling within ecosystems. However, the related researches in shrubs were very limited. In this study, we aimed to investigate leaf stoichiometry and its driving factors in shrubs, and whether stoichiometry significantly differs among closely related species. Methods We analyzed leaf C, N and P concentrations and their ratios in 32 species of Ericaceae from 161 sites across southern China. We examined the relationships of leaf stoichiometry with environmental variables using linear regressions, and quantified the interactive and independent effects of climate, soil and species on foliar stoichiometry using general linear models (GLM). Important Findings The foliar C, N and P contents of Ericaceae were 484.66, 14.44 and 1.06 mg g−1, respectively. Leaf C, N and P concentrations and their ratios in Ericaceae were significantly related with latitude and altitude, except the N:P insignificantly correlated with latitude. Climate (mean annual temperature and precipitation) and soil properties (soil C, N and P and bulk density) were significantly influenced element stoichiometry. The GLM analysis showed that soil exerted a greater direct effect on leaf stoichiometry than climate did, and climate affected leaf traits mainly via indirect ways. Further, soil properties had stronger influences on leaf P than on leaf C and N. Among all independent factors examined, we found species accounted for the largest proportion of the variation in foliar stoichiometry. These results suggest that species can largely influence foliar stoichiometry, even at a lower taxonomic level. [ABSTRACT FROM AUTHOR]

• Compared with POD5 and AOT40, the POD1 function can better reflect the GPP loss of grassland in northern China. • Adding ozone module can improve the simulation accuracy of GPP. • Average annual ozone concentrations are lower in subtropical regions. • Vegetations in southern China will suffer from more severe ozone pollution due to higher stomatal conductance. In the context of global warming, with the increasing tropospheric ozone concentration and the obvious trend of aridity, terrestrial ecosystems are experiencing multiple pressures. However, there are still many uncertainties in modeling the effects of ozone on ecosystem productivity. In this study, an ozone uptake module was coupled to the BEPS (Boreal Ecosystem Productivity Simulator) model, and the new version, the BEPS-O 3 model, was used to simulate the impacts of ozone on the gross primary productivity (GPP) of woodland and grassland ecosystems in China. Observational data from four sites were used to verify and improve the models, namely, DXG (grassland), HBG (shrub), DHS (evergreen broad-leaved) and CBS (coniferous forest). The regional results show that the total GPP of forest, grassland and shrub in China was 3.62 Pg C, 0.75 Pg C 0.33 Pg C in 2016, respectively. The GPP loss of forests, grasslands and shrubs caused by ozone was 2.8% and 1.1% and 1.5% of the GPP in woodland and grassland ecosystems, respectively (excluding farmland). Subtropical regions experienced the worst GPP losses, although ozone concentrations were not high. However, higher stomatal conductance leads to higher ozone absorption. By comparing the parameters of previous studies, we conclude that the ozone uptake function was better than the ozone exposure function in modeling. Furthermore, the selection of the ozone uptake function will have a significant impact on the final simulation results, especially for grassland. [ABSTRACT FROM AUTHOR]

The global atmospheric nitrogen (N) deposition has intensified in recent years, resulting in a complex impact on forest ecosystems. This study investigated the effects of canopy (CAN) and understory additions of N (UAN) on leaf carbon (C) and N assimilations, as well as growth parameters of representative woody plant species in an evergreen broad-leaved forest, i.e. Castanea henryi, Schefflera heptaphylla, Blastus cochinchinensis, and Lasianthus chinensis. The results showed that leaf N assimilation key enzyme nitrate reductase (NR) activities of B. cochinchinensis and S. heptaphylla were significantly decreased by UAN, and were significantly decreased by CAN for C. henryi. CAN significantly decreased the nitrite reductase activity of C. henryi, while significantly increased that of L. chinensis. However, the A max values of each woody species were not significantly different among control (CK), CAN, and UAN. Community surveys demonstrated that CAN and UAN inhibited the growth (diameter at breast height, height, or crown width) of the representative large tree, C. henryi, while promoting the growths of understory woody species (B. cochinchinensis and L. chinensis). Overall, N addition was found to change the physiological processes of N and C metabolisms of the dominant woody species in an evergreen broad-leaved forest. The community of subtropical evergreen broad-leaved forests may further decline and its C fixation capacity may be detrimentally changed under N deposition in the future., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Species turnover patterns can be inconsistent due to differences in the dispersal ability of different growth forms. Here, species of trees, shrubs, herbs, and bryophytes in the Xiaoqinling National Nature Reserve in China were analyzed to determine patterns of species turnover along an elevation and spatial gradient. Variance partitioning was used to assess the relative contribution of topographic heterogeneity and dispersal limitation to species turnover. Our results suggest that the effect of dispersal limitation is more important than topographic heterogeneity on species turnover in temperate mountane ecosystems in the study area. Dispersal limitation has a greater effect on trees species turnover than on shrubs, herbs or bryophytes species turnover. [ABSTRACT FROM AUTHOR]

Changes in minimum winter temperature (MWT) and their potential effects on plant growth and development have been gaining increased scientific attention. To better understand these changes across long temporal scales, the present study used dendroclimatological techniques to assess variations in MWT in Southwestern China. Using data from Rhododendron species distributed in areas above the tree-line, a regional composite chronology was generated for a 341-year period. Based on the significant negative correlation between MWT values and ring-width, the most reliable parts of this chronological data were then used to reconstruct MWT values for the past 211 years. This reconstructed MWT series showed decadal to multi-decadal fluctuations. Three distinct cold periods prevailed during 1823-1858, 1882-1891 and 1922-1965, while four warm intervals occurred in 1800-1822, 1858-1881, 1892-1921 and 1966-2011. Our reconstructed MWT reveals a warming trend over the most recent eight decades, which is in agreement with instrumental observations. However, the MWT values and rate of warming over the past seven decades did not exceed those found in the reconstructed temperature data for the past 211 years. Spatial correlations reveal that the MWT in Southwest China is strongly associated with regional temperatures in the Eastern and Central Himalaya, Northern China, and the Indian Peninsula. Larger scale climate oscillations of the Western Pacific and Northern Indian Ocean as well as the North Atlantic Oscillation probably influenced the region's temperature in the past. [ABSTRACT FROM AUTHOR]

Incorporating native shrubs into restoration projects can improve biodiversity conservation and enhance the sustainability of ecosystem functions. Shrubs grow under different forest canopy structures, having varied microclimatic conditions according to forest type and composition. Currently, there is a lack of information on propagation from seed and planting material availability for the utilization of shrubs in forest restoration. In the present study, we evaluated the effects of temperature and light on germination of ten shrub species (Ardisia japonica, Callicarpa cathayana, Callicarpa giraldii var. subcanescens, Deutzia schneideriana, Fraxinus sieboldiana, Hydrangea chinensis, Maesa japonica, Rhododendron simsii, Spiraea japonica var. fortunei and Weigela japonica var. sinica) occurring in subtropical forests in China. No seeds of any species germinated in the coolest thermal regime (5/10 °C), while optimal temperature requirements varied from 10/20 °C to 25/35 °C. Seeds of small-seeded species had higher germination percentages in the light treatments, while larger seeds were not photoblastic. There was no relationship between germination in the light and the seed shape index. Our results may assist in identification of seed traits and suitable shrub species for restoration in specific forest types, thus aiding native forest recovery of structure and composition. Successful recovery leads to enhanced biodiversity, reestablishment of microhabitats and ecological interactions in the forest understorey., (© 2023 German Society for Plant Sciences, Royal Botanical Society of the Netherlands.)

• The effects of different scaling up methods for estimates of stand T were explored. • Daily stand T differed according to the method used for the estimation. • Cross-sectional area appeared to be the most suitable basis for scaling up. Transpiration (T) is a key hydrological process, delivering water essential for plant metabolism and thus affecting productivity. A major challenge in estimating stand T is how to accurately scale sap flow data from individual trees to the stand. In shrub ecosystems, various scaling up methods have been used to extrapolate tree-level sap flow measurements to stand-level T, these include leaf area, cross-sectional area and number of branches. However, the performances of different scaling up methods have not been fully explored for shrubs. In this study, we measured sap flow of a xerophytic shrub (Salix psammophila) and scaled up using measures of leaf area, cross-sectional area and numbers of branches in order to estimate stand T during the rainy seasons in 2019 and 2020 on the northern Loess Plateau, China. In addition, we measured precipitation, throughfall, stemflow, soil evaporation, surface runoff and 0–200 cm soil water content to calculate actual stand T on the basis of soil water balance method. The results revealed that daily stand T differed according to the scaling up methods used for the estimation. Daily estimated stand T based on measures of leaf area (0.1–13.1 mm d−1) was consistently higher than those based on cross-sectional area (0.2–8.6 mm d−1) and number of branches (0.4–8.9 mm d−1) (p < 0.05). During the two rainy seasons, the actual daily mean stand T (2.5 ± 1.6 mm d−1) was significantly lower than the estimation by the three scaling up methods (p < 0.05). The method based on cross-sectional area appeared to be most suitable for scaling up because it had the lowest root mean square error and bias values (0.939 mm d−1 and 0.633 mm d−1, respectively). This study highlights the wide variations of stand T upon which scaling up method was chosen, and these differences need to be considered when converting tree-level sap flow to stand-level T in shrub and other ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Artificial restoration by shrub plantation in semi-arid sandy land can increase carbon sequestration. However, little information is available on the carbon flux input to soil resulted from fine roots turnover and leaf fallen during restoration. The present study relying on the ingrowth core and sequential core methods investigated the fine-root dynamics and fine-root production of three shrub stands (dominated by Artemisia halodendron, Caragana microphylla and Salix gordejevii respectively) which have different life-forms and root architectures. The soil carbon and nitrogen stock was also estimated in the restoration, and the relative contribution of carbon input related to fine root mortality and leaf fallen was assessed. The mean standing live and dead fine-root biomass in A. halodendron stand at the primary restoration were significantly less than in C. microphylla stand at moderate restoration and S. gordejevii stand in lowland. Consistent with leaf production, fine root production showed a positive correlation with soil water content and followed the order of A. halodendron < C. microphylla < S. gordejevii. In contrast, the fine-root turnover rate was quicker in primary restoration phase (2.12 year−1) than in moderate restoration phase (1.55 year−1) and lowland (1.28 year−1). The annual carbon and nitrogen inputs via fine root mortality and leaf fallen increased from 74.78 g C m−2 year−1 and 1.25 g N m−2 year−1 in A. halodendron stand to 189.66 g C m−2 year−1 and 1.67 g N m−2 year−1 in S. gordejevii stand. Although the share of the fine roots of A. halodendron seized a relatively smaller proportion in the net primary production compared with those in C. microphylla and S. gordejevii, the relative contribution of carbon input related to fine roots mortality in primary restoration phase was higher than in the other two shrub stands. The present study proved that the carbon input to soil by fine-root mortality considerably contributed to the restoration of soil carbon and nitrogen stock in semi-arid degraded lands. [Copyright &y& Elsevier]

Conversion of cropland into perennial vegetation land can increase soil organic carbon (SOC) accumulation, which might be an important mitigation measure to sequester carbon dioxide from the atmosphere. The 'Grain for Green' project, one of the most ambitious ecological programmes launched in modern China, aims at transforming the low-yield slope cropland into grassland and woodland. The Loess Plateau in China is the most important target of this project due to its serious soil erosion. The objectives of this study are to answer three questions: (1) what is the rate of the SOC accumulation for this 'Grain for Green' project in Loess Plateau? (2) Is there a difference in SOC sequestration among different restoration types, including grassland, shrub and forest? (3) Is the effect of restoration types on SOC accumulation different among northern, middle and southern regions of the Loess Plateau? Based on analysis of the data collected from the literature conducted in the Loess Plateau, we found that SOC increased at a rate of 0.712 TgC/year in the top 20 cm soil layer for 60 years under this project across the entire Loess Plateau. This was a relatively reliable estimation based on current data, although there were some uncertainties. Compared to grassland, forest had a significantly greater effect on SOC accumulation in middle and southern Loess Plateau but had a weaker effect in the northern Loess Plateau. There were no differences found in SOC sequestration between shrub and grassland across the entire Loess Plateau. Grassland had a stronger effect on SOC sequestration in the northern Loess Plateau than in the middle and southern regions. In contrast, forest could increase more SOC in the middle and southern Loess Plateau than in the northern Loess Plateau, whereas shrub had a similar effect on SOC sequestration across the Loess Plateau. Our results suggest that the 'Grain for Green' project can significantly increase the SOC storage in Loess Plateau, and it is recommended to expand grassland and shrub areas in the northern Loess Plateau and forest in the middle and southern Loess Plateau to enhance the SOC sequestration in this area. [ABSTRACT FROM AUTHOR]

Tropical forests vegetation and community research have tended to focus on the tree component, and limited attention has been paid to understory vegetation. Species diversity and composition of the understory of tropical seasonal rain forest were inventoried in a 625m² area (for sapling layer) and a 100m² area (for herb/seedling layer) in three 1ha plots. We found 3068 individuals belonging to 309 species, 192 genera and 89 families. The most important family as determined by the Family Importance value (FIV) was Rubiaceae in both sapling and herb/seedling layers. In terms of Importance value Index (IVI), the shrub Mycetia gracilis (Rubiaceae) was the most important species in the sapling layer and the pteridophyte Selaginella delicatula (Selaginellaceae) was the most ecological significant species in the herb/seedling layer. Much more vascular plant species were registered in the understory than in the tree layer totaled among the three plots. The species diversity did not differ significantly among the tree layer, sapling layer and herb/seedling layer. Given that we still know little about the understory plant community for growth forms other than trees, the results from the present study indicate that more attention should be paid to the understory vegetation during the decision-making process for biodiversity conservation in the tropical forests. Rev. Biol. Trop. 59 (1): 455-463. Epub 2011 March 01. [ABSTRACT FROM AUTHOR]

Abstract: A rainwater harvesting system on slopes using contour furrows with plastic-covered transverse ridges designed to be used in small rainfall dominated areas of the semiarid loess region of China has been tested from 2001 to 2004. The system consisted of constructing contour furrows on the loess slope at a distance of 5m with plastic-covered transverse ridges built in the furrows between shrubs of Caragana korshinskii. There were three treatments in the study: (1) plastic-covered ridge with gravel-mulched furrows (T1), (2) plastic-covered ridge with bare furrows (T2), and (3) control (no ridge and no contour furrow) (T3). The experimental results indicated that runoff from the natural loess slope was small and variable, and only produced from a few rainfall events with high intensity. Runoff efficiency averaged 13.8, 4.5, 1.4, and 0.4% in 2001, 2002, 2003, and 2004, respectively. However, the plastic-covered ridges accumulated runoff from most rainfall events, particularly from the light rains less than 5mm. So the natural loess slope between the furrows and the plastic-covered ridges in the furrows can complement each other, i.e., the plastic-covered ridges induce runoff from small rainfall to the planted area, and the natural loess slope between the furrows concentrate runoff from heavy rainfall, thus improving rain use efficiency. The total runoff collected from both the natural loess slope and the plastic-covered ridges to the planted area in the furrows was 231, 143, 88, and 59mm in 2001, 2002, 2003, and 2004, respectively. Soil moisture storage in the 200-cm deep soil layer was obviously higher for T1 and T2 than for T3, and C. korshinskii showed a significant improvement in growth for the T1 and T2 treatments. Therefore the combination of contour furrows and plastic-covered ridges as rainwater harvesting system may have a great potential development in the small rainfall dominated arid regions of China. [Copyright &y& Elsevier]

Halostachys caspica (Chenopodiaceae) is a halophytic shrub commonly found in saline areas of the western deserts in China that produces small-sized seeds (0.07 mg). Effects of temperature, light, NaCl, and polyethylene glycol-6000 on seed germination were investigated by incubating seeds in Petri dishes in controlled environments. Seed germination was promoted by both light and temperature alternation. Seed dormancy was not detected. Temperature dependence of seed germination indicated that H. caspica seeds are able to germinate at any time between spring and autumn in their habitats in China. Seed germination was almost completely withheld when seeds were moistened with 500 mmol kg-1 NaCl, but seeds remained viable after moistening with 3000 mmol kg-1 NaCl for 41 d. Opportunities for seed germination were expected to be very limited in the field because for photoblastic H. caspica seeds to germinate, the seeds need to be almost exposed to the soil surface, where they are likely to suffer severe water deficiency and high salinity. It was suggested that germination of H. caspica seeds in the field is facilitated by a supply of a large amount of water from melting snow in early spring. [ABSTRACT FROM AUTHOR]

Based on long-term ecological research, microorganisms are sensitive to environmental changes in the process of ecosystem succession. However, few works have focused on the response of different groups of soil microorganisms to subalpine secondary succession and the driving forces behind the stepwise community development. To explore the changes in the microbial community structure and the driving mechanisms, we selected three replicated secondary succession gradients consisting of grass, shrub, different secondary forests (picea, pine and birch) and primary forest in a subalpine area in southwestern China. A high-throughput sequencing method was used to compare differences in the soil fungal and bacterial community structures. In combination with aboveground plant diversity and soil properties, the different mechanisms controlling the soil microbial community were revealed by the Mantel test. A two-way correlation network was also used to explore the connections among stages. The results show that the change in bacterial and fungal community structure was obvious, and these changes of bacteria were significantly correlated with soil acid phosphatase, LAP, soil moisture and aboveground vegetation communities during succession development in subalpine forests. Moreover, the fungal community was related to soil organic carbon, nitrogen, vegetation diversity, abundance and community structure. We also found that different dominant fungi play crucial roles in the succession sequence, and the relationship between soil microbes and vegetation is gradually simplified and stabilized. Our work suggests that both the relatively stable bacterial communities and the significantly changing fungal communities are notably associated with abiotic and biotic factors in secondary succession. As the ecosystem evolves, the dominant fungi obviously respond to succession and can successively establish close relationships with plants. Consequently, our results have important implications for understanding the driving mechanisms that control the soil microbial community during subalpine forest secondary succession. [ABSTRACT FROM AUTHOR]

Shrub biomass estimation is valuable in assessing ecological health, soil, and water conservation capacity, and carbon storage in arid areas, where trees are scattered, and shrubs are usually dominant. Most shrub biomass estimation models are derived from trees designed for trees, yet shrubs and trees show significant differences in morphology. However, current biomass estimation methods specifically for shrubs are still lacking. This study aimed to test various predictors' performance in estimating shrub biomass, particularly providing an improved cone frustum volume model as a new predictor. Seven different variables, including three univariates and four composite variables, were selected as predictors in allometric models. Six dominant shrub species of different sizes and morphology in the semi-arid Hunshandake Sandy Land in Inner Mongolia were selected as samples to test the seven predictors' performances in above-ground biomass estimation. Results showed that the single measurements performed poorly and were not suitable for shrub biomass estimation. The allometric models, including crown-related volumes as predictors, performed much better and were considered ideal for common shrub biomass estimation. The improved cone frustum volume model had more flexible geometric for shrubs of different shapes and sizes, with high fitting accuracy and stability among all the volume predictors. Therefore, we recommend the volume of an inverted cone frustum with a crown diameter and ground diameter as the long and short diameters as an excellent predictor of shrub biomass estimation, especially when studies involve various shrub species, and a general model would be needed. [ABSTRACT FROM AUTHOR]

Brown root rot (BRR), caused by Phellinus noxius (Corner) G. Cunningham, occurs on over 200 species of plants, especially woody trees and shrubs. Ceylon myrtle ( Phyllanthus myrtifolius [Wight] Müll.Arg.), a common hedge plant, was recently observed to be infected with BRR. Disease diagnosis was performed by completing Koch's postulates, and Ceylon myrtle was confirmed to be a new host of P. noxius . Typical symptoms of BRR were observed, including reduction in leaf size, dieback of branches, and suspended growth of young leaves. A disease severity index was used to quantify BRR in this study. Compared with Malabar chestnut, Ceylon myrtle was relatively resistant to BRR. Surprisingly, phylogenetic analysis of the ITS and 28S sequences revealed that isolates identified as P. noxius from Taiwan and many other countries were clustered in the same clade but separate from the clade comprising isolates from China, which were designated Pyrrhoderma noxium based on P . noxius . Therefore, to temporarily distinguish these pathogens, the former clade was designated GPN (global P. noxius ), whereas the latter clade was designated CPN (China Py. noxium ). In biocontrol assays, Streptomyces padanus and Bacillus sp. were selected for BRR control of Ceylon myrtle. Disease severity was reduced from 0.51 to 0.37 by S. padanus and to 0.14 by Bacillus sp. in greenhouse trials. In addition, the two biocontrol agents, especially S. padanus , exhibited good growth-promoting effects on cuttings of Ceylon myrtle. With these double advantages, S. padanus and Bacillus sp. have great potential to control BRR in practical applications.