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Plot‐scale experiments indicate that functional diversity (FD) plays a pivotal role in sustaining ecosystem functions such as net primary productivity (NPP). However, the relationships between functional diversity and NPP across larger scale under varying climatic conditions are sparsely studied, despite its significance for understanding forest–atmosphere interactions and informing policy development. Hence, we examine the relationships of community‐weighted mean (CWM) and functional dispersion (FDis) of woody plant traits on NPP across China and if such relationships are modulated by climatic conditions at the national scale. Using comprehensive datasets of distribution, functional traits, and productivity for 9120 Chinese woody plant species, we evaluated the distribution pattern of community‐weighted mean and functional dispersion (including three orthogonal trait indicators: plant size, leaf morphology, and flower duration) and its relationships with NPP. Finally, we tested the effects of climatic conditions on community‐weighted mean/functional dispersion–NPP relationships. We first found overall functional diversity–NPP relationships, but also that the magnitude of these relationships was sensitive to climate, with plant size community‐weighted mean promoting NPP in warm regions and plant size functional dispersion promoting NPP in wet regions. Second, warm and wet conditions indirectly increased NPP by its positive effects on community‐weighted mean or functional dispersion, particularly through mean plant size and leaf morphology. Our study provides comprehensive evidence for the relationships between functional diversity and NPP under varying climates at a large scale. Importantly, our results indicate a broadening significance of multidimensional plant functional traits for woody vegetation NPP in response to rising temperatures and wetter climates. Restoration, reforestation actions and natural capital accounting need to carefully consider not only community‐weighted mean and functional dispersion but also their interactions with climate, to predict how functional diversity may promote ecosystem functioning under future climatic conditions. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) contamination is a growing concern, as exposure to the metal has been shown to inhibit plant growth and development. However, soil Cd pollution in China is typically mild, and thus its concentration often does not impede plant growth. On the other hand, it is unknown if increased plant growth impacts Cd uptake, movement, and accumulation. Here, we analyzed the relationship between Cd accumulation in 31 tomato cultivars and the impact on specific growth parameters in mild Cd contamination. The results showed that there are variations in the Cd distribution among the 31 tomato cultivars studied. There were higher Cd concentrations in shoots of the cultivar 'SV3557', whereas root Cd concentrations were the lowest. The roots of the cultivar 'HF11' recorded the lowest Cd content but had higher Cd content in the shoots. The Cd concentration in roots and shoots was not related to root length, plant height, and root weight. However, Cd accumulation in the shoots was markedly promoted by root length and plant height, and Cd accumulation in the roots was promoted by root weight. Subsequently, we imposed Cd on four selected tomato cultivars to ascertain their accumulation in the shoot tissues. The results revealed that, among the four tomato cultivars, Cd was highly accumulated in the leaves, followed by the stems, and the fruits (leaf > stem > fruit). When identifying significant loci associated with Cd accumulation in tomato plants, it is crucial to find a suitable indicator to assess the plant's ability to accumulate Cd. Thus, Cd concentration in shoots can be used as a reliable proxy for evaluating tomato plants' capacity for Cd accumulation. This study serves as a valuable reference in guiding the selection of such an index. [ABSTRACT FROM AUTHOR]

Cultivated land resources are seriously insufficient in China, where the per capita cultivated land area is only 1/3 of the world average. The improved saline-alkali soil can be expected to plant food crops, in order to alleviate the shortage of cultivated land resources. However, saline-alkaline soil has poor physical structure and a low plant survival rate. Fortunately, coal gangue has the potential to improve the physical structure and chemical properties of saline-alkali soil. It is a high demand to apply the coal gangue into the saline-alkali land for the better recycling of waste coal gangue resources with the improvement of saline-alkali land. In this study, a pot experiment was conducted to investigate the effect of coal gangue on the saline-alkali soil and potato cultivation. Coal gangues with different application rates (0, 15%, 30%, and 50%) were applied to the saline-alkali soil, marked as the treatment of CK, CL15, CL30 and CL50, respectively. Three potato varieties JZ-12, WT-5 and DF-10 were planted during the experiment. 12 replicates were set for each treatment, because the planting potatoes was not conducive to sampling and testing soil bulk density indicators. Among them, three varieties of potato were planted for nine repetitions (three repetitions for each variety), and the remaining three repetitions were used to determine the soil physicochemical properties with the applied coal gangue. A systematic analysis was made to clarify the effects of coal gangue on the soil physical and chemical properties of saline-alkali soil, potato plant growth, photosynthetic characteristics, malondialdehyde content, antioxidant enzyme activity, potato yield and quality. The results showed as follows: 1) The addition of coal gangue affected the soil's physicochemical properties, and then improved the poor and hardened quality of the salinealkali soil. The soil pH value, salt concentration, and bulk density decreased gradually, whereas, the soil structure tended to be stable. At the same time, there was a significant increase in the content of organic matter, total nitrogen, total phosphorus, total potassium, hydrolytic nitrogen, and available potassium in the soil (P<0.05), with increases of 15.2%-447.2%, 11.7%-27.6%, 0.5%-29.5%, 43.3%-225.8%, 16.6%-216.1%, and 3.6%-34.9%, respectively. 2) There were some differences in the effects of different amounts of coal gangue on the growth, photosynthesis, and stress resistance of potato plants. The growth physiological and stress resistance indicators of plants at different stages showed a trend of first increasing and then decreasing, as the amount of coal gangue increased. CL30 treatment shared the best performance to promote potato growth, while CL50 showed a certain inhibitory. The above-ground biomass of the three potato varieties under different treatments after harvest was ranked as CL30, CL50, and CL15. 3) In the CK group, all potato plants died during the seedling stage, while planting potatoes with different treatments of coal gangue completed the growth cycle and produced potatoes. The weight of tuber per plant was the highest under CL30 treatment, ranging from 252.37-424.10 g. The highest content of starch, protein, and vitamin C in tubers also ranged from 90.0-110.3, 13.3-14.1, and 99.0-164.0 mg/kg, respectively. However, there was still a quality gap, compared with the commercial potatoes, where the starch, protein, and vitamin C content were 21.2%-35.7%, 45.8%-48.8%, and 7.9%-44.4% lower than commercial potatoes, respectively. In summary, the coal gangue can be used for the saline-alkali soil improvement. 30% coal gangue can be expected to effectively improve the saline-alkali soil environment suitable for planting potatoes. Therefore, the finding can provide application prospects in the field of saline-alkali soil improvement and food security. [ABSTRACT FROM AUTHOR]

Phytoliths are silica bodies formed in living plant tissues, and they can be reliable indicators of their parent plants when they demonstrate characteristic phytolith morphology. As shown by the growing case studies around the globe, phytolith morphology is of significant value for identifying and even quantifying domesticated plants. However, researchers also alert that phytoliths morphology can change, for example, in alkaline solutions or heat, causing the loss of characteristic phytoliths and eventually leading to the over- or under-identification of certain phytoliths. Focusing on the degree to which heat can cause changes to the phytolith morphology of millet, the present study carried out a series of controlled heating experiments on six varieties of modern common millet (Panicum miliaceum) growing in different regions of Northern China. Husked grains were heated following the dry ashing method. Specimens prepared from the dry ashing method were examined under an optical microscope to quantify articulated husk phytoliths, which are characteristic millet phytoliths, and to estimate the surface area of millet grains. We estimated that 30.8% to 59.5% of the common millet phytoliths underwent morphological damage in the heating experiments. Considering our previous heating experiments on foxtail millet, we conclude that compared to foxtail millet phytoliths, common millet phytoliths experience morphological damage more quickly when exposed to heat. This observation may explain (at least partially) the contradictory results between macro- and micro-botanical results. It reminds us that common millet can be underrepresented in the micro-botanical evidence (phytoliths). We conclude the paper by discussing the potential archaeological implications of our heating experiments. [ABSTRACT FROM AUTHOR]

Drought stress poses a serious threat to Pinus massoniana seedling growth in southern China. Trichoderma species, as beneficial microorganisms, have been widely used in agriculture to enhance plant growth and drought tolerance, but the interaction mechanisms remain unclear. To investigate the effect of drought-resistant Trichoderma longibrachiatum inoculation on P. massoniana growth under drought stress, the plant physiological indicators and rhizosphere microbiome diversity were measured to identify Trichoderma-activated mechanisms. Trichoderma longibrachiatum inoculation significantly promoted P. massoniana growth under drought treatment, and enhanced nitrogen, phosphorus, and potassium absorption compared with those of non-inoculated seedlings. Trichoderma longibrachiatum treatment alleviated the damage to cell membranes and needle tissue structure, and significantly increased antioxidant enzyme activities, osmotic substance contents, and photosynthesis in P. massoniana in response to drought stress. Soil nutrient contents, activities of sucrase, phosphatase, and urease as well as the relative abundances of the dominant genera Burkholderia, Rhodanobacter, and Trichoderma were elevated in the rhizosphere soil of P. massoniana inoculated with T. longibrachiatum under drought stress. A network analysis showed that certain crucial dominant taxa driven by T. longibrachiatum inoculation, including Penicillium, Trichoderma, Simplicillium, Saitozyma, Burkholderia, Bradyrhizobium, Sinomonas, and Mycobacterium, had more correlations with other microorganisms in the soil. Trichoderma longibrachiatum enhanced P. massoniana seedling growth under drought stress by regulating physiological responses and soil microbial community. [ABSTRACT FROM AUTHOR]

Many virtual power plant demonstration projects are currently in operation in China, but research on the risk assessment of virtual power plants is insufficiently deep. Virtual power plants are complex systems operated by multiple participants and can provide a variety of products or services. Based on the operation practices of virtual power plants, in this study, we considered the characteristics of different components of virtual power plants and their impact on the operation process. We developed a risk assessment model for virtual power plants from many aspects involved in their operation processes. First, we analyzed the operation modes that can be selected during the operation of a virtual power plant, including the scenario in which electric vehicles participate and considering the comprehensive demand response. Second, we considered the risk faced by a virtual power plant from five dimensions: external policy, participation, coupling technology, bidding transaction, and credit management risk; we then designed an operation risk indicator system for virtual power plants with 29 indicators. Third, based on the entropy weight order relation method and cloud model for determining the index uncertainty in the process of risk assessment, we developed a cloud risk assessment model and specific algorithm flow based on the entropy weight order relation method are proposed. Finally, we compared the optimal economic operation strategies of a virtual power plant under different operating characteristics. The results showed that the comprehensive risk in the operation of gas virtual power plants can be effectively reduced when considering various uncertainties, electric vehicles, and comprehensive demand response risk. The results verify the effectiveness and scientificity of the improved cloud model risk assessment model proposed in this paper. [ABSTRACT FROM AUTHOR]

We conducted a study to examine the growth and physiological changes in 12 different ecotypes of Sesuvium portulacastrum collected from Hainan Island in China. These ecotypes were subjected to different concentrations (0, 200, 400, and 600 mmol/L) of sodium chloride (NaCl) salt stress for 14 days. We also analyzed the expression of metabolic genes related to stress response. Under low salt stress, indicators such as plant height in region K (0 mmol/L: 45% and highest at 200 mmol/L: 80%), internode length (0 mmol/L: 0.38, 200 mmol/L: 0.87, 400 mmol/L: 0.25, and 600 mmol/L: 1.35), as well as leaf area, relative water content, fresh weight, and dry weight exhibited an overall increasing trend with the increase in salt concentration. However, as the salt concentration increased, these indicators showed a decreasing trend. Proline and malondialdehyde contents increased with higher salt concentrations. When the NaCl concentration was 400 mmol/L, MDA content in the leaves was highest in the regions E (196.23%), F (94.28%), J (170.10%), and K (136.08%) as compared to the control group, respectively. Most materials demonstrated a significant decrease in chlorophyll a, chlorophyll b, and total chlorophyll content compared to the control group. Furthermore, the ratio of chlorophyll a to chlorophyll b (Rab) varied among different materials. Using principal component analysis, we identified three ecotypes (L from Xinglong Village, Danzhou City; B from Shuigoupo Village, Lingshui County; and J from Haidongfang Park, Dongfang City) that represented high, medium, and low salt tolerance levels, respectively, based on the above growth and physiological indexes. To further investigate the expression changes of related genes at the transcriptional level, we employed qRT-PCR. The results showed that the relative expression of SpP5CS1, SpLOX1, and SpLOX1 genes increased with higher salt concentrations, which corresponded to the accumulation of proline and malondialdehyde content, respectively. However, the relative expression of SpCHL1a and SpCHL1b did not exhibit a consistent pattern. This study contributes to our understanding of the salt tolerance mechanism in the true halophyte S. portulacastrum, providing a solid theoretical foundation for further research in this field. [ABSTRACT FROM AUTHOR]

Leaf traits are important indicators of plant life history and may vary according to plant functional type (PFT) and environmental conditions. In this study, we sampled woody plants from three PFTs (e.g., needle-leaved evergreens, NE; broad-leaved evergreens, BE; broad-leaved deciduous, BD) on the eastern Qinghai-Tibetan Plateau, and 110 species were collected across 50 sites. Here, the divergence and correlations of leaf traits in three PFTs and relationships between leaf traits and environment were studied. The results showed significant differences in leaf traits among three PFTs, with NE plants showed higher values than BE plants and BD plants for leaf thickness (LT), leaf dry matter content (LDMC), leaf dry mass per area (LMA), carbon: nitrogen ratio (C/N), and nitrogen content per unit area (Narea), except for nitrogen content per unit mass (Nmass). Although the correlations between leaf traits were similar across three PFTs, NE plants differed from BE plants and BD plants in the relationship between C/N and Narea. Compared with the mean annual precipitation (MAP), the mean annual temperature (MAT) was the main environmental factor that caused the difference in leaf traits among three PFTs. NE plants had a more conservative approach to survival compared to BE plants and BD plants. This study shed light on the regional-scale variation in leaf traits and the relationships among leaf traits, PFT, and environment. These findings have important implications for the development of regional-scale dynamic vegetation models and for understanding how plants respond and adapt to environmental change. [ABSTRACT FROM AUTHOR]

Summary: N-enriched biochar can increase the accumulation of carbon (C), nitrogen (N), phosphorus (P), and biomass in rice plants. On the other hand, the biomass and C, N, and P contents of plant organs are important indicators to reflect plant C, N, and P storages. We established control, 4 t ha−1, and 8 t ha−1 N-enriched biochar treatment plots in a subtropical paddy field in China to investigate the effect of these treatments on C, N, and P storages, ecological stoichiometry in various rice plant organs, and their relationships with edaphic factors. The application of N-enriched biochar increased the biomass and storages of C, N, and P in rice roots, stems, leaves, and grains, mainly at 4 t ha−1. The application of N-enriched biochar decreased the C/N and C/P ratios of rice organs, but increased their N/P ratio. Changes in C/N were mainly due to the changes in storage, while N/P was positively correlated with N storage of stems, leaves, and grains and negatively correlated with P storage in roots. Pearson's correlation analysis revealed that pH was negatively correlated, and soil N content was positively correlated with P storage in various organs of rice. In addition, soil P content and chlorophyll were positively correlated with N storage. In conclusion, we found that the application of N-enriched biochar improved plant N and P storage and stoichiometrical relations among rice organs. [ABSTRACT FROM AUTHOR]

Light use efficiency (LUE) models have been widely used to estimate terrestrial gross primary production (GPP). However, the estimation of GPP still has large uncertainties owing to an insufficient understanding of the complex relationship between water availability and photosynthesis. The plant water stress index (PWSI), which is based on canopy temperature, is very sensitive to the plant stomatal opening and has been regarded as a good indicator for monitoring plant water status at the regional scale. In this study, we selected a cork oak plantation in northern China with an obvious seasonal drought as the research object. Using the ground-observed data, we evaluated the applicability of the LUE models with typical water stress scalars (MOD17, MODTEM, EC-LUE, ECM-LUE, SM-LUE, GLO-PEM, and Wang) in a GPP simulation of the cork oak plantation and explored whether the model's accuracy can be improved by applying PWSI to modify the above models. The results showed that among the seven LUE models, the water stress scalar had a greater impact on the model's performance than the temperature stress scalar. On sunny days, the daily GPP simulated by the seven LUE models was poorly matched with the measured GPP, and all models explained only 23–52% of the GPP variation in the cork oak plantation. The modified LUE models can significantly improve the prediction accuracy of the GPP and explain 49–65% of the variation in the daily GPP. On cloudy days, the performance of the modified LUE models did not improve, and the evaporative fraction was more suitable for defining the water stress scalar in the LUE models. The ECM-LUE and the modified GLO-PEM based on PWSI had optimal model structures for simulating the GPP of the cork oak plantation under cloudy and sunny days, respectively. This study provides a reference for the accurate prediction of GPP in terrestrial ecosystems in the future. [ABSTRACT FROM AUTHOR]

Identifying indicator taxa is a solution to the problem of a lack of diverse data. However, the variation between studies on richness correlations (RCs) among taxa from different climate regions makes the application value of indicator taxa questionable. Few studies have compared the RCs among climatic regions in a single study, leaving the variation in RCs and the underlying ecological drivers among climatic regions unknown. In this study, data were compiled on vascular plants, vertebrates (including mammals, birds, reptiles, and amphibians), and environmental factors across 219 nature reserves located in subtropical and temperate regions of China to examine RCs among taxonomic groups and underlying ecological mechanisms. Results showed that the climatic region could affect between-taxon correlations in species richness and that the effectiveness of vascular plants as suitable indicator taxa for vertebrates varied with the climatic region and target taxa. Energy (temperature and evapotranspiration) and habitat heterogeneity (area and elevation range) were ecological drivers of RCs among taxonomic groups in the subtropical and temperate regions. The differences in the effect of abiotic factors on RCs among taxonomic groups caused the difference in RCs between subtropical and temperate regions. Our findings provide new evidence for understanding the variation of RCs and the underlying mechanisms and highlight the positive role of climatic variables and habitat heterogeneity in determining RCs between vascular plants and vertebrates. [ABSTRACT FROM AUTHOR]

Photosynthetic characteristics are widely used as indicators of plant responses to global environmental changes such as precipitation change and nitrogen (N) deposition increase. How different plant species respond physiologically to the future precipitation change combined with increasing N availability is largely unclear. A field experiment was conducted to study responses in seasonal and interannual leaf carbon (C) exchange of two dominant plant species, Leymus chinensis and Stipa grandis , to additional water (either as spring snow or as summer water) and N application in a semi-arid temperate steppe of China. Our results showed that spring snow and summer water addition both increased the maximum photosynthetic rate (Amax) of two dominant species. Such effect was likely caused by raised light saturation point, the maximum apparent quantum yield, stomatal conductance, and transpiration rate. The N application combined with spring snow or summer water addition both enhanced Amax of S. grandis in both experimental years, whereas N application only increased Amax of L. chinensis combined with summer water addition. Their responses were attributed to a concurrent increase in leaf N concentration (Nleaf) and decrease in leaf phosphorus (P) concentration (Pleaf), indicating that Nleaf and Pleaf affect photosynthetic characteristics to regulate leaf C exchange. Our results suggest that differentiated responses among different species in photosynthetic characteristics may lead to changes in ecosystem structure and functioning under increasing precipitation and N deposition. [ABSTRACT FROM AUTHOR]

Leaf traits are important indicators of plants' adaptive strategy to environmental changes. It is an established fact that leaf traits are jointly regulated by climatic and edaphic factors besides genetic factors. However, the relative importance of these abiotic forces in determining the general patterns of herbaceous plant leaf traits across different climatic regions in China is far from clear. We collected 1,653 observations of 542 species of herbaceous plant leaf traits including leaf mass per area, leaf nitrogen, and leaf phosphorus from 316 sampling sites across four climatic regions. We found that the leaf mass per area in the arid region was apparently larger than the others, whereas the smallest mass-based leaf nitrogen and mass-based leaf phosphorus were found in the humid region. Increased growing season temperature and evapotranspiration consistently promoted a conservative growth strategy indicated by higher relative benefit of leaf mass per area, especially in the arid region. Solar radiation in growing season promoted an acquisitive growth strategy indicated by higher relative benefits of mass-based leaf nitrogen and phosphorus in the humid region, but opposite patterns were found in the arid region and semi-humid region. Of all the soil nutrients including soil organic matter, total nitrogen, total phosphorus, and available nitrogen, soil available nitrogen was the strongest predictor of relative benefits of leaf traits associated with a nutrient acquisitive strategy, except in the nutrient-rich semi-humid region. There was a relatively larger number of abiotic factors contributing to relative benefits of leaf traits in the arid and humid regions. We concluded that plant functionality could respond divergently to the same factor facing different habitat conditions. Moreover, the relative benefits of leaf traits tended to be more vulnerable to abiotic filtering in more stressful conditions. Our findings have important implications for understanding the context-dependency of plant functionality to environmental filtering and further improving the predictability of plant dynamics under global change. [ABSTRACT FROM AUTHOR]

Determining large‐scale patterns of plant elemental concentrations and stoichiometry along environmental gradients is critical for understanding plant adaptive strategies and predicting ecosystem biogeochemistry processes. However, it remains unclear as to how plant carbon (C), nitrogen (N) and phosphorus (P) concentrations and their stoichiometry in different organs (leaves, stems and roots) respond to large‐scale environmental gradients in drylands.We determined C, N and P concentrations and their ratios in leaves, stems and roots of plants growing in the dryland ecosystems of China. Using threshold indicator taxa analyses, we identified indicator species of plant C, N and P responses to aridity and soil properties.The arithmetic averaged concentrations of C, N and P in drylands were 414, 18.7 and 1.38 mg/g for leaves respectively; 445, 12.1 and 1.08 mg/g for stems respectively; and 418, 10.5 and 0.89 mg/g for roots respectively. The C:N, C:P and N:P ratios were 25.2, 386 and 16.3 for leaves respectively; 42.8, 592 and 14.8 for stems respectively; and 46.8, 658 and 15.6 for roots respectively. Aridity and soil pH generally exerted positive effects on plant N and negative effects on C and P concentrations and, thus, were related negatively to C:N ratios and positively to C:P and N:P ratios. The C, N and P concentrations in organs generally increased with increasing corresponding soil C, N and P concentrations. Shrubs were mainly positive indicators of plant C, N and P concentrations in response to aridity and soil pH, and negative indicators of soil nutrients. In contrast, herbaceous species were mainly positive indicators of soil nutrients and negative indicators of aridity and soil pH.These findings indicate that plants tend to accumulate N rather than C and P with increasing aridity and soil pH. The identification of indicator species for plant elements in response to aridity and soil traits informs our understanding of species‐specific biogeographic patterns of organ elements and potential adaptive strategies of plants in drylands. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Studies of the morphotypes, production and preservation of phytoliths in soils provide a theoretical basis for paleovegetation reconstruction. However, there is a lack of systematic studies of the phytoliths of woody plants in the warm temperate humid zones, which greatly limits the application of phytoliths in paleovegetation reconstruction in this environmental context. In this study we analyzed the phytoliths of 211 plant samples (81 leaf samples, 73 branch samples, 57 bark samples) and 30 topsoil samples from the warm temperate humid zones of China. The results demonstrate that while most of the leaf samples contained phytoliths, only a few of the branch and bark samples did so. In terms of phytolith concentration, the sample types were ordered as follows: bark samples > leaf samples > branch samples. In this study the phytoliths in woody plants were classified into10 categories and 22 sub-categories, and the results of detrended correspondence analysis (DCA) showed that elongate dentate and blocky morphotypes were closely associated with Picea ; elongate cavate and margin-cuneiform morphotypes were closely associated with Larix ; acute bulbosus and hair base morphotypes were associated with Morus , Broussonetia and Diospyros ; and elongate psilate, elongate attenuate, and sclereid morphotypes were associated with Quercus , but these types are not unique to Quercus. The topsoil woody phytolith assemblages contained four types of broad-leaved phytolith (tabular, tabular sinuate, sclereid, epidermal phytolith), and three types of coniferous phytolith (blocky, elongate dentate, elongate tabular). The ratio of the total of broad-leaved phytoliths to the sum of broad-leaved phytoliths and coniferous phytoliths is useful for discriminating broad-leaved forest from coniferous forest. Overall, the results confirm the usefulness of phytoliths as indicators of woody plants in the warm temperature humid region in China, and they demonstrate the potential of woody phytolith assemblages for paleovegetation reconstruction. [ABSTRACT FROM AUTHOR]

Xinjiang is the province with the largest saline-alkali land in China. The growth of halophytes will be stressed when their salt content reaches the threshold. In this study, the pot experiments were conducted and Suaeda salsa, a typical halophyte, was selected as the object to explore the relationship between growth characteristics and salt content under different soil salinity gradients. Salinity gradients were set according to the maximum soil salinity in the current years of Ebinur Lake Wetland National Nature Reserve (ELWNNR). They were classified using the following threshold values: ≤2 g/kg (Control Group), 10 g/kg, 20 g/kg, 30 g/kg, and 40 g/kg. The original spectrum, trilateral position and growth characteristics were used as indexes for analysis. With the increase of soil salt content, the red edge shift occurs first, followed by the blue edge shift. The position of yellow edge, green peak and blue edge were not sensitive with the change of soil salinity. This indicates that the red edge is the best indicator for evaluating plant growth. Compared with the Control Group, when the salt content is less than 10 g/kg, the growth status of plant seems not significantly affected. However, plant growth begins to be stressed when the salt content increases to 20 g/kg, which is a turning point for plant health. The increase of soil salt content can inhibit chlorophyll synthesis and plant growth. Plants begin to die when the salt content reaches the 40 g/kg. Therefore, 40 g/kg could be regarded as the critical point of salt content which inhibits plant growth. The study also shows that the relationship between plant-height change rate and soil salt content is the most significant, indicating that the plant-height change rate is significantly impacted by soil salt content. [ABSTRACT FROM AUTHOR]

Sand burial and precipitation drive plant community structure and functions in semiarid desertified areas, while net primary productivity (NPP) is one of the most important indicators of plant community function. However, how NPP responds to sand burial in combination with changed precipitation regimes is still unclear. We conducted a field experiment with simultaneous sand burial and enhanced precipitation treatments to test the responses of both aboveground net primary productivity (ANPP) and belowground net primary productivity (BNPP) in a semiarid desertified steppe in North China. The results showed that sand burial significantly affected the community ANPP but had no significant effects on the community BNPP. Sand burial increased the ANPP of rhizome grass and decreased the ANPP of perennial herbs, bunchgrass and annual herbs, with no significant effects on legume herbs, while enhanced precipitation did not significantly affect the community ANPP and BNPP or the ANPP of all five plant functional types (PFTs). Sand burial combined with enhanced precipitation mediated the vertical allocation of BNPP in the community. There are multiple significant relationships between the ANPP of different PFTs and the BNPP among the different soil layers. These findings will be conducive to understanding the consequences of grassland desertification under the background of climate change, with corresponding implications for grassland management and vegetation restoration in semiarid desertified areas. [ABSTRACT FROM AUTHOR]

In urban green spaces, it is important to maintain a suitable soil moisture content, an important indicator of plant growth. The management of urban green spaces faces great challenges in semi-humid areas of China, which are featured by interannual changes in rainfall and the alternation between droughts and floods. This paper aims to select suitable Organic Ground Cover (OGC) materials for urban green spaces in such areas, as the OGC can effectively absorb water and suppress the evaporation of soil moisture. For this purpose, 16 OGC materials were selected for our experiments, and 33 identical holes were dug on a field of silty loam. Next, 16 holes were separately covered by a 5 cm-thick layer of the 16 materials, 16 holes were separately covered by a 10 cm-thick layer of the 16 materials, and 1 hole was taken as the control sample (CK). On this basis, the authors explored how the 16 materials in two different thicknesses affect the soil moisture contents in four different soil depths. The results show that: When the OGC layer was 5 cm thick and 10 cm thick, CK had the lowest soil moisture content at any soil depth. In most cases, the soil moisture content under the same OGC material changed insignificantly with the material thicknesses, except FPB2 and CP. The layer of OGC materials should be 5 cm, if the only purpose is to increase the soil moisture content and enhance the landscape effect, and 10 cm if rainwater absorption is also taken into account. The above results provide a reference for selecting the OGC materials suitable for urban greening. [ABSTRACT FROM AUTHOR]

Patterns of species diversity in mountain herbaceous communities at different altitude gradients and their relationships with environmental factors was an enduring hot topic in ecological and geographical researches. This topic was explored in the context of the mountains of Guancen, Guamli, and Wulu that extend from north to south across the Lϋliang Mountain range in Shanxi Province in China. Each mountain was divided into three altitude gradients: high, middle and low. During the vegetation growing season in 2018, a n investigation was conducted on the growth characteristics indicators of plants and hydrothermal factors located at these altitude gradients and species diversity index values (α-, β-, and y-diversity) were calculated to explore the patterns of species diversity at different altitude gradients and their relationships with environmental factors. The results were as follows: (1) Unimodal patterns of variation for a-diversity (calculated using the Simpson, Shannon-Wiener and Pielou indexes) that corresponded to increasing altitudes, with the highest species diversity occurring at the mid-altitude gradient; The results calculated for β-diversity using different indexes revealed the highest value for the Cody index and the lowest value for the Bray-Curtis index at altitudes between 1 900 and 2 000 m, indicating that areas located between 1 900 and 2 000 m form a transition zone in which the herbaceous conun1mily undergoes a rapid process of species renewal and changes in its composition; The results for y-diversity indicated a pattern of unimodal variation in relation to altitude. (2) Changes in altitude gradient had highly significant impacts on changes in temperature and humidity (P < 0. 01); Various environmental factors notably altitude, humidity, and temperature had a combined effects on changes in the values of the a-diversity indexes, with altitude being the main influencing factor (P<0.05), and changes in temperature and humidity had no significant effects on species diversity (P>0.05). Therefore, species diversity within the herbaceous community in the Lϋliang Mountains predominantly showed a "mid-altitude bulge" pattern, with altitude being the main factor affecting changes in species diversity. The finding of this study can contribute to refining and expanding studies of herbaceous communities in this region and provide inputs for advancing the systematic conservation and management of herbaceous resources. [ABSTRACT FROM AUTHOR]

Yu Yam Ancestral Garden is one of the four famous gardens in Lingnan, China. This study was carried out with the methods of survey and analysis, fi eld measurement and selecting spatial samples methods, dividing Yu Yam Ancestral Garden into 11 plots, for undertaking initial quantitative research on the three-dimensional green biomass (TGB) and environmental ecological benefits (EEB) of the plants. The results showed thatthe arbor played a decisive role in TGB of the Yu Yam Ancestral Garden sample plot, in which the maximum contribution value was evergreen trees. And the Pearson correlation signifi cance analysis was carried out on 11 indicators of the plant morphology and the TGB of the treesshrubs, drawing a conclusion that the main infl uencing factor for TGB was the ratio of trees-shrubs, and the simulation equation was Y = 2􀀍357.67X3 + 176.707. EEB of the plants was positively correlated with TGB. A very good way of understanding of the correlation between the TGB of plants and their EEB was proposed, which could provide objective and quantitative theoretical reference data for the plant arrangement of arbor, shrubs and grasses in artifi cial garden green spaces. It is helpful to understand the importance of artifi cial garden green spaces ecological value. [ABSTRACT FROM AUTHOR]

The mosses have been widely used as bioindicators to investigate pollution and changes of heavy metals in different countries and regions. In this research, the field surveys were carried out for understanding the moss community and enrichment effects of the dominant species of mosses around the uranium mill tailings impoundment in South China, especially for the enriched contentions of 210Pb and 210Po in soil and Hypnum plumaeforme. The results showed that the maximum concentrations of U and 226Ra in the study sites were 93 mg kg−1 and 1130.8 Bq kg−1, respectively. The exhalation rate of 222Rn (ERRn), soil U, and 226Ra contents in SS1, SS2, and SS3 were higher than CKS. With the increase of the distance from the central well, the contents of nuclides (U and 226Ra) in soils and H. plumaeforme were both decreased. And, the bioconcentration factors of H. plumaeforme for 210Pb and 210Po ranged from 1.05 to 1.49, and 1.25 to 1.40, respectively, indicating an accumulation of 210Po and 210Pb from soil by H. plumaeforme. These results indicated that H. plumaeforme is hopeful to become an accumulator plant for remediation of radon pollution, and also can be used as a potential indicator plant for radon pollution monitoring. [ABSTRACT FROM AUTHOR]

Aims Morphological variation of leaves is a key indicator of plant response to climatic change. Leaf size and shape are associated with carbon, water and energy exchange of plants with their environment. However, whether and how leaf size and shape responded to climate change over the past decades remains poorly studied. Moreover, many studies have only explored inter- but not intraspecific variation in leaf size and shape across space and time. Methods We collected >6000 herbarium specimens spanning 98 years (1910–2008) in China for seven representative dicot species and measured their leaf length and width. We explored geographical patterns and temporal trends in leaf size (i.e. leaf length, leaf width and length × width product) and shape (i.e. length/width ratio), and investigated the effects of changes in precipitation and temperature over time and space on the variation in leaf size and shape. Important Findings After accounting for the effects of sampling time, leaf size decreased with latitude for all species combined, but the relationship varied among species. Leaf size and shape were positively correlated with temperature and precipitation across space. After accounting for the effects of sampling locations, leaf size of all species combined increased with time. Leaf size changes over time were mostly positively correlated with precipitation, whereas leaf shape changes were mostly correlated with temperature. Overall, our results indicate significant spatial and temporal intraspecific variation in leaf size and shape in response to climate. Our study also demonstrates that herbarium specimens collected over a considerable period of time provide a good resource to study the impacts of climate change on plant morphological traits. [ABSTRACT FROM AUTHOR]

Rehabilitation of areas impacted by subsidence following coal mining is a pressing need in eastern China, especially where availability of suitable soil material is limited. A field experiment was established to evaluate performance of varying layered combinations of soil and coal gangue materials as measured by maize (Zea mays L.) growth and yield. Two control treatments and eight experimental treatments were constructed. All treatments had a 30 cm surface layer of topsoil. CK1 consisted of native soil material. CK2 consisted of 50 cm gangue covered by topsoil and 40 cm subsoil. Group 1 treatments (T1–T3) had a 15 cm layer of subsoil immediately below the topsoil, underlain, respectively, by progressively thicker gangue layers (20, 30, and 40 cm) overlying another 15 cm subsoil layer, in turn underlain by gangue. Group 2 treatments (T4–T7) consisted of 40 cm subsoil. T4-T5 followed the same pattern as Group 1 except that the lower subsoil layer was 25 cm thick. T6-T7 differed from T4-T5 by having 25 cm upper and 15 cm lower subsoil layers between different thicknesses of gangue. Group3 (T8) consisted of three 10 cm layer of subsoil separating 2 gangue layers and gangue layer below. Key plant performance indicators, biomass and yield, were significantly better under CK1-2 than in the other treatments (T1–T8). Below the topsoil Eh, pH and total salt content were higher and water content was less in T1–T8 than in CK1-2, reflecting the influence of gangue in 30–70 cm zone in these treatments. The nutrient content (TN, AN, TP, OP, TK, AK, and OM) of topsoil in experimental treatments was lower than or similar to that of the control treatments. Results indicate that minimizing the adverse impacts of gangue requires a combined top-subsoil cover of at least 70 cm. [ABSTRACT FROM AUTHOR]

The vegetation water content (VWC) quantitative is useful for monitoring vegetation physiological growth. The relationship between VWC and vegetation water indices was analyzed. The optimal estimation model was established. The results show that: (1) Absorption bands primarily fell within 380 to 400 nm, 680 to 720 nm, 1420 to 1450 nm, 1900 to 1940 nm, and 2450 to 2500 nm; (2) comparing published vegetation water indices and developed vegetation indices, it showed that DVI(1712,1382), NDSI(2201,1870) and RSI(2259,1870) had a better correlation with VWC than the published vegetation water; and (3) NDSI(2201,1870) and RSI(2259,1870) performed well in estimating vegetation water content, DVI(1712,1382) had a rough estimate of its water content. Moreover, the linear combination of DVI(1712,1382), NDSI(2201,1870) and RSI(2259,1870) improved the estimation of VWC. The best vegetation indices for estimating VWC were found to be the linear combination of DVI(1712,1382), NDSI(2201,1870) and RSI(2259,1870) in arid area of northwestern China. [ABSTRACT FROM AUTHOR]

• Daily minimum air temperatures (T min) performs well in identifying spring frost events. • ROC curve and Youden Index were used to determine the critical temperature threshold. • The critical T min threshold triggering spring frost damage to tea plants in NYR was 3.7 °C. • Two application cases revealed the T min threshold of 3.7 °C was acknowledged. Spring frost damage (SFD) is the main meteorological disaster limiting the tea industry in the region of the north of the Yangtze River (NYR) in China. Research regarding an SFD indicator for tea plants is of great significance for prevention and control of spring frosts, as well as for timely monitoring and early warning. Based on daily minimum air temperatures (T min) and spring frost disaster records in NYR from 1961 to 2020, the Receiver Operating Characteristic curve (ROC) was used to evaluate the accuracy of frost identification, and the critical temperature threshold for SFD to tea plants was determined by jointly comparing Overall Accuracy and the Youden Index. The results showed that the area under the ROC curve was 0.977, indicating that T min performed well in identifying frost events. The critical temperature threshold for spring frost in NYR was determined as T min of 3.7 °C, and 93 % of frost occurrences were correctly identified. Based on the determined critical threshold of SFD, the number of spring frost days, first frost date (FFD), and last frost date (LFD) in NYR from 1961 to 2020 were analyzed. The results showed that the number of spring frost days in NYR decreased from north to south. FFD appeared earlier and LFD ended later in northern NYR than in southern NYR. These results provide theoretical and technical support for the monitoring and evaluation of spring frosts in NYR, and also for implementing SFD prevention and control measurements for tea plants by use of a critical temperature threshold. [ABSTRACT FROM AUTHOR]

There is a strong signal showing that the climate in Xinjiang, China has changed from warm-dry to warm-wet since the early 1980s, leading to an increase in vegetation cover. Based on a regression analysis and Hurst index method, this study investigated the spatial–temporal characteristics and interrelationships of the vegetation dynamics and climate variability in Xinjiang Province using the leaf area index (LAI) and a gridded meteorological dataset for the period 1982–2012. Further analysis focused on the discrimination between climatic change and human-induced effects on the vegetation dynamics, and several conclusions were drawn. (1) Vegetation dynamics differ in mountain and plains regions, with a significant increasing trend of vegetation cover in oases and decreasing trend of vegetation growth in the Tienshan and Altay Mountain. The Hurst exponent results indicated that the vegetation dynamic trend was consistent, with a sustainable area percentage of 51.18%, unsustainable area percentage of 4.04%, and stable and non-vegetated area ratio of 44.78%. (2) The warm-dry to warm-wet climatic pattern in Xinjiang Province since the 1980s mainly appeared in the western part of the Tienshan region and North Xinjiang. Temperatures increased in all seasons over the majority of Xinjiang, and precipitation showed a significant increasing trend in the mountainous regions in spring, summer and autumn, whereas the rate of precipitation change was higher in the plains region in winter compared with that in other seasons. (3) A correlation occurs between the climate variables (precipitation and temperature) and mean LAI, and this correlation varies at the seasonal and regional scales, with coniferous forest, meadow and grassland more correlated with precipitation in spring and summer and not correlated with temperature, which indicated that precipitation was the dominant factor affecting the growth of mountain vegetation. The mean LAI of vegetation in the plains exhibited significant correlation with precipitation in winter and temperature in spring and summer. (4) A residual analysis showed a human-induced change that was superimposed on the climate trend and exhibited two effects: vegetation regeneration in oases throughout Xinjiang and desertification in the meadow located in the mountainous area of the western Tienshan Mountains and Altay Mountains. (5) Grassland is the most sensitive vegetation type to short-term climatic fluctuations and is the land-use type that has been most severely degraded by human activity; thus, local governments should take full advantage of this climatic warm-wet shift and focus on protecting vegetation to improve this fragile arid environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ψ sat and ε max were significantly related to RGR DBH at the growth stage. • The structural equation models (SEM) showed that both Ψ tlp and Ψ sat were affected by ε max. • The functional/structural coordination between PV parameters adjusted the RGR DBH of trees. • There exists a tradeoff between drought tolerance and growth in the respect of energy allocation at the species level. Current theoretical models for tree relative growth rate (RGR) have considered physiological processes based on carbon economy and nutrient-productivity relations, but have not taken water relations into account. According to the ecological energetics and Lockhart equation theories, if more energy is needed to maintain water balance in plants, less energy should be invested towards growth, resulting in a trade-off between growth and drought tolerance. Leaf pressure–volume (PV) curve parameters are the best recognised classical indicators of plant drought tolerance, however, the relationships between tree growth and leaf PV parameters have rarely been investigated in forest communities. In the study, we selected two evergreen (Lithocarpus glaber , Cyclobalanopsis oxyodon) and two deciduous species (Quercus serrata , Platycarya strobilacea) that dominate northern subtropical forests on Mt. Shennongjia, central China. For each species, we selected individuals at different developmental stages (growth vs. mature stage), and measured the relative growth rate of diameter at breast height (RGR DBH) and leaf PV curve parameters, including leaf saturated osmotic potential (Ψ sat), maximum bulk elastic modulus (ε max), turgor loss osmotic potential (Ψ tlp) and leaf water capacity (C leaf). Correlation analysis and structural equation models (SEM) were applied to explore the relationships between RGR DBH and PV parameters. The results showed that: 1) at both stages, RGR DBH was positively correlated with Ψ sat , but not with Ψ tlp and C leaf ; 2) ε max was negatively related to RGR DBH at the growth stage; 3) the relationship between PV parameters and RGR DBH was determined mainly by inter-specific difference; 4) SEM showed that both Ψ tlp and Ψ sat were affected by ε max ; and 5) due to the interaction between the PV parameters, Ψ sat and ε max had a direct effect on RGR DBH only during the growth stage. Our results showed that the functional/structural coordination between PV parameters adjusted the RGR DBH of trees, and among different species, there exists a tradeoff between energy allocation for drought tolerance and growth. These findings can be applied to improve RGR models, and show how forests respond to warm-induced drought, which is a major threat to global forests in a future warmer climate. [ABSTRACT FROM AUTHOR]

Increasing nitrogen (N) diagnosis efficiency and accuracy is crucial for optimizing wheat N management. We aimed to establish a spatially and temporally explicit model for the diagnosis of winter wheat N status on small scale farms using multivariate information. To determine the most accurate approach, seven field experiments involving different cultivars and N treatments were conducted in east China over five years. A fixed-wing unmanned aerial vehicle (UAV) mounted multispectral camera was used to acquire canopy spectral data of winter wheat at the jointing and booting stages, while agronomic indicators of plant dry matter (PDM), plant N accumulation (PNA) and N nutrition index (NNI), as well as agrometeorological (AM) and field management (FM) data, were measured synchronously. Direct and indirect strategies of NNI estimation were applied for N diagnosis at the jointing and booting stages. Four machine learning (ML) algorithms were used to characterize the relationships between agronomic variables and UAV remote sensing, AM and FM data. The results demonstrated the random forest (RF) model that integrated UAV remote sensing, AM and FM data achieved the higher accuracy for predicting NNI (R 2 = 0.82–0.87, RMSE = 0.11–0.12 and RE = 12.94%−15.57%) amongst the four ML models based on the direct strategy at the jointing and booting stages. Similarly, the RF model performed most accurate estimation for PDM (R 2 = 0.69–0.78, RMSE = 0.43–0.61 t ha−1 and RE = 12.74%−24.49%) and PNA (R 2 = 0.83–0.84, RMSE = 13.00–17.53 kg ha−1 and RE = 17.03%−25.44%), then NNI (R 2 = 0.54–0.55, RMSE = 0.09–0.13 and RE = 8.34–12.65%) was further calculated using the indirect diagnosis strategy. Based on the optimal NNI diagnosis interval derived from the relationships between relative yield (RY) and plant NNI at the jointing (0.92–1.04) and booting (0.97–1.15) stages, the two diagnosis strategies obtained similar diagnostic accuracies in the three study farms and performed more accurately at the booting (areal agreement = 0.70–0.90, Kappa = 0.49–0.82) than jointing (areal agreement = 0.54–0.71, Kappa = 0.36–0.53) stages. The combination of fixed-wing UAV remote sensing with AM and FM information using the RF algorithm can significantly increase the accuracy and efficiency of in-season wheat N diagnosis at the farm scale. • Four machine learning algorithms were used to characterize the relationships between agronomic variables and multivariate data. • Direct and indirect strategies of NNI estimation were evaluated based on the optimal NNI diagnosis interval. • Mapping the wheat N status based on fixed-wing UAV imagery at the farm scale. [ABSTRACT FROM AUTHOR]

Quercus franchetii Skan, a crucial indicator plant of dry-hot valley with endemic to southwestern China. In this study, the complete chloroplast genome of Q. franchetii was assembled and characterized. The circular genome was 160,785 bp in length, containing a large single copy (LSC) region of 90,169 bp, a small single copy (SSC) region of 18,828 bp, and a pair of inverted repeat regions of 25,894 bp. Total 131 genes were annotated, comprising 86 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The phylogenetic analysis indicated that Q. franchetii was closely related to Q. glauca and Q. chungii. [ABSTRACT FROM AUTHOR]

Many studies have shown that pine needles are a good biomonitor for atmospheric concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). However, this biomonitor has not been tested in large areas, and the quantitative relationship between concentrations in pine needles and air has not been established. In the present study, we collected pine needles from 38 cities in China. The concentrations of 2,3,7,8-PCDD/Fs were measured by gas chromatography combined with high-resolution mass spectrometry. The total PCDD/F concentrations ranged from 5.4 to 330 pg/g dry weight of pine needles. The pine needles from cities located in central China and three major city agglomerations contained high concentrations of PCDD/Fs, while those from cities in the west and on the coast contained relatively low concentrations. Primary emission and diffusion processes were the main controls of the PCDD/F concentrations in pine needles. Homologue profiles of PCDD/Fs in pine needles were characterized by PCDFs/PCDDs >1 in the industrialized cities and <1 in unindustrialized cities. The congener patterns were dominated by 1,2,3,4,6,7,8-HpCDF and OCDD, indicating that combustion was the major source of the PCDD/Fs. By comparing the PCDD/F concentrations in the pine needles and those in air, we established a preliminary linear relationship between them. Finally, the concentrations in air of PCDD/Fs in the 38 cities of China could be predicted from this relationship. [ABSTRACT FROM AUTHOR]

Abstract: Regional vegetation cover plays an important role in modeling ecosystem change and conservation. In this study, MODIS-NDVI (Normalized Difference Vegetation Index) and EVI (Enhanced Vegetation Index) image of 32 days composite were made in August 2008. 39 samples of grassland, 40 samples of shrub and 55 samples of forest were established in Northern Hebei Province in August 2008. The MODIS image we used was taken in the same period as the time of filed sampling. The MODIS-NDVI and EVI values of field samples were extracted from MODIS image. The optimal regression equation was developed between the NDVI values and the vegetation cover of field samples in grassland, shrub and forest respectively. The similar process was conducted for EVI values. The simulation precision of the equation was tested by independent field data. Lastly, the predictive validity of natural vegetation cover by using NDVI and EVI values was compared and assessed. The results show that all selected optimal regression equation pass significance testing of 0.05. As for forest, shrub and grassland, the coefficient Correlation (R2) of selected optimal regression equations based on NDVI values is higher than that based on EVI(from 0.488 to 0.644), and Mean Absolute Error (MAE) based on NDVI values is lower (from 0.0617 to 0.0916) than that based on EVI values. There is a conclusion that MODIS-NDVI are more correlation with field data of vegetation cover and have obvious advantages for predicting natural vegetation coverage than MODIS-EVI in our study area. [ABSTRACT FROM AUTHOR]

• Opposite crab-plant relationships are found between similar saltmarsh ecosystems. • Facilitation on plants may depend on crab burrowing mediated by soil compactness. • Coastal restoration needs to consider context-dependent plant-animal interactions. • Plant performance cannot be solely used as indicators of plant-crab interactions. • Inference of plant-crab interactions needs to combine biotic and abiotic indicators. Increasing effort has been devoted to restoring coastal ecosystems to counteract their degradation globally. Restoration success of coastal ecosystems often relies on harnessing biotic interactions that shape the performance of foundation plant species. Crabs acting as essential ecosystem engineers and consumers are commonly present in coastal saltmarshes. Previous work has focused on the grazing effect of crabs on plants. In line with the idea of top-down control, plant performance (in terms of biomass or height) is often used as indicators of plant-animal interactions. However, crabs could also produce facilitative effects through non-consumptive behavior. It remains unclear if and to what extent the net effect of crabs on coastal plants is dependent on environmental context. Therefore, systematic assessments are needed to test if the reliability of plant performance as an indicator of plant-crab interactions is context-dependent. Here, we conducted field survey in two similar intertidal saltmarsh ecosystems along the Yellow Sea coast, eastern China, and examined the effects of crab burrowing, soil properties, and nutrient availability on plant (Suaeda salsa) performance using multiple regression and structural equation models. We found that crab burrow density was significantly correlated with plant height, which signals strong plant-crab interactions. Surprisingly, we observed opposite signs (positive vs. negative) of plant-crab relationships between the two study sites that have highly similar composition and structure of plant communities. A possible explanation is that soil compactness can mediate crab burrowing behavior, resulting in differential facilitative effects on the plants. Thus, the usefulness of plant height serving as an indicator of plant-crab interactions depends on environmental context to a substantial degree. More comprehensive indicators taking into account soil compactness may facilitate robust inference of plant-crab interactions. Our results highlight landscape-scale spatial heterogeneity and context-dependency of plant-animal interactions in coastal saltmarshes, and provide a useful implication to inferring nuanced biotic interactions using compressive biotic and abiotic indicators in coastal ecosystems. [ABSTRACT FROM AUTHOR]

• Effects of water nutrient stoichiometry on a free-floating fern were studied. • Water column phosphorus rather than water column nitrogen determined the plant growth. • Plant functional traits were identical under different stoichiometric conditions. • A decoupling between plant growth and functional traits existed. Eutrophication is a prominent component of global environmental change in aquatic ecosystems and usually triggers the aggressive growth of free-floating aquatic plants. An overload of nutrients, including nitrogen (N) and phosphorus (P), causes eutrophication. However, the effects of water nutrient stoichiometry on aquatic plants under eutrophic conditions have been understudied. The present study subjected Salvinia natans (L.) All., a free-floating fern, to shifted water nutrient stoichiometric regimes, and indicators for plant growth, including biomass accumulation and relative growth rate, and resource use functional traits, including specific leaf area, leaf area ratio, specific length of root-like leaves, specific area of root-like leaves, chlorophyll content and maximal fluorescence, were evaluated. We found that water nutrient stoichiometry affected plant growth traits rather than functional traits. In particular, P eutrophication profoundly facilitated the growth of S. natans. Therefore, P rather than N appeared to determine the growth of S. natans. However, the functional traits were unresponsive to the shift in the water nutrient stoichiometric regime. A decoupling between plant growth and functional traits in response to water nutrient stoichiometric change existed for S. natans generally. Since S. natans infests rice paddy agriculture in southern China, the regulation of P addition, for instance, curtailing the use of P-enriched pesticides and fertilizers in agriculture, may benefit the control of this nuisance species. [ABSTRACT FROM AUTHOR]

In China, excessive phosphorus (P) application in protected vegetable fields has led to high legacy P stores. Soil amendment with alum or dolomite is one of many best management practices (BMPs) used to reduce P losses in calcareous soils. However, both the kinetics and mechanisms of P sorption and soil available P in amended soils are understudied. Herein, both aspects were looked at under controlled conditions. Firstly, a sorption study which coupled P concentrations with poorly-crystalline Al hydroxides and dolomite was conducted. Results from this batch experiment showed that P sorption on poorly-crystalline Al hydroxides was homogenous and occurred mainly via displacement of inner-sphere hydroxyl (Al–OH) instead of the formation of AlPO 4. However, the amount of sorbed P reached maximum sorption of 73.1 mg g−1 and did not change with further increase in P concentration. It was observed that P adsorbed onto the dolomite surface at low P concentrations, whereas hydroxyl replacement and uneven cluster precipitation of Ca 3 (PO 4) 2 occurred at high P concentrations. A second 90 day incubation experiment investigated changes to soil available P and sorption-desorption across variable rates of amendments (0–50 g kg−1). Results showed that alum amendment at a rate of 50 g kg−1 decreased soil CaCl 2 –P and Olsen-P concentrations by 91.9% and 57.8%, respectively. However, Olsen-P increased when the dolomite rates were <20 g kg−1. Phosphorus sorption-desorption of the amended soil showed alum had higher P sorption efficiency than dolomite at low addition rates (<10 g kg−1). However, soil amended with high dolomite rates (>10 g kg−1) could sorb more P in comparison with alum when P concentrations were increased. The P status of the amended soil was closely connected to the P sorption mechanisms on mineral amendments, soil P concentrations and soil properties. Image 1 • P sorption on poorly-crystalline Al hydroxides was mainly through displacement of inner-sphere Al–OH groups. • Higher alum rates and P concentrations contributed to the inner-sphere P sorption. • Mg in dolomite inhibited the formation of hydroxylapatite (HAP) at higher P concentrations. • Dolomite addition decreased soil CaCl 2 –P, but increased Olsen-P. In the present study, it was found that phosphate was mainly sorbed as inner-sphere complexes rather than a formation of AlPO 4 on poorly-crystalline Al hydroxides at pH 6.5. When alum was added to soil, it was shown that higher rates of alum added and higher P concentrations facilitated easier formation of inner-sphere P sorption. In addition, it was found that Mg in dolomite inhibited the formation of hydroxylapatite (HAP) while it promoted the formation of amorphous calcium phosphate (ACP). In the soil treatments amended with dolomite, soil CaCl 2 –P (an indicator of P loss risk) decreased due to the surface P sorption while soil Olsen-P (an indicator of plant available P) increased. The latter is attributed to the dual effect of the competition between –OH and P and the inhibition of Mg to form stable HAP on dolomite. [ABSTRACT FROM AUTHOR]

The growth of a large number of poisonous plants is an indicator of grassland degradation. Releasing allelochemicals through root exudates is one of the strategies with which poisonous plants affect neighboring plants in nature. Arbuscular mycorrhizal fungi (AMF) can form a mutualistic symbiosis with most of the higher plants. However, the manner of interaction between root exudates of poisonous plants and AMF on neighboring herbage in grasslands remains poorly understood. Stellera chamaejasme L., a common poisonous plant with approved allelopathy, is widely distributed with the dominant grass of Leymus chinensis in the degradeds of Northern China. In this study, we investigated the addition of S. chamaejasme root exudates (SRE), the inoculation of AMF, and their interaction on the growth and tissue nitrogen contents of L. chinensis, the characteristics of rhizosphere AMF, and soil physicochemical properties. Results showed that SRE had significant effects on ramet number, aboveground biomass, and total nitrogen of L. chinensis in a concentration dependent manner. Additionally, SRE had a significant negative effect on the rate of mycorrhiza infection and spore density of the AMF. Meanwhile, the addition of SRE significantly affected soil pH, electrical conductivity, available nitrogen (AN), available phosphorus (AP), total nitrogen (TN), and total carbon (TC) contents; while neither inoculation of AMF itself nor the interaction of AMF with SRE significantly affected the growth of L. chinensis. The interaction between AMF and SRE dramatically changed the pH, AP, and TC of rhizosphere soil. Therefore, we suggested SRE of S. chamaejasme affected the growth of L. chinensis by altering soil pH and nutrient availability. AMF could change the effect of SRE on soil nutrients and have the potential to regulate the allelopathic effects of S. chamaejasme and the interspecific interaction between the two plant species. We have provided new evidence for the allelopathic mechanism of S. chamaejasme and the regulation effects of AMF on the interspecific relationship between poisonous plants and neighboring plants. Our findings reveal the complex interplay between the root exudates of poisonous plants and rhizosphere AMF in regulating population growth and dynamics of neighboring plants in degraded grassland ecosystems. [ABSTRACT FROM AUTHOR]

We established vegetation indicators of active layer thickness for the southern permafrost region in China, which can be used for monitoring permafrost degradation. • Plant community features are linked to near-surface permafrost presence in NE China. • Two Carex species and Betula fruticosa indicate near-surface permafrost explicitly. • Moss thickness and shrub cover correlate with active layer thickness of permafrost. • We established near-surface permafrost prediction models with above features. The most dramatic permafrost degradation is expected to occur at the southern edge of permafrost distribution, which is difficult to detect directly on a large scale. Ecological indicators can be used to provide an early signal of changes in terrestrial ecosystems for regional near-surface permafrost habitats and potentially to monitor near-surface permafrost degradation. In this study, plant composition and community structure indicate the near-surface permafrost distribution at the southern edge of the boreal forest and permafrost in northeastern China. The plant species composition and structure of aboveground vegetation were linked to the belowground near-surface permafrost distribution in order to find indicators of changes in vegetation features from permafrost melting. These indicators are essential for assessing changes in permafrost vegetation systems under climate change. Carex schmidtii and C. appendiculata in the herb layer and Betula fruticosa in the shrub layer were found to be specific near-surface permafrost plant indicator species, especially for the wetland permafrost. Shrub cover, moss mat thickness and tree canopy cover are also strongly correlated with near-surface permafrost distribution. The active layer thickness (ALT) showed negative correlations with moss thickness and shrub cover because these features may act as buffers for regional climate warming. We chose the cover of each indicator species, near-surface permafrost-specific community features and geographical information as independent variables to predict the possible distribution of near-surface permafrost in our study region using logistic regression. The results showed that the prediction model had good performance and accuracy. Our study sheds light on early caution of deepening of regional-scale permafrost active layer with vegetation indicators that can further be identified from satellite images. [ABSTRACT FROM AUTHOR]