Soil organic carbon (SOC) is an important carbon (C) pool in terrestrial ecosystems. Pant diversity can enhance SOC content in forests, grasslands, and agricultural ecosystems, and its potential effects on the composition and stability of SOC have aroused increasing interest. However, there is no systematic review of their underlying mechanisms. The present study therefore summarizes advances in research on the effects of plant diversity on the content, composition and stability of SOC and the underlying mechanism with the aim of providing a scientific basis for maximizing soil carbon and nitrogen (N) sequestration and mitigating global climate change through the promotion of plant diversity. Increasing plant diversity can increase the inputs of plant litter biomass into soils, enhance the quality of mixed litter (e.g., lower C:N), and promote the turnover and accumulation of SOC. It can also increase plant-derived C via root and litter inputs to soils, or increase microbe-derived C via enhanced microbial turnover. These processes can also increase soil particulate organic carbon (POC) and mineral associated organic carbon (MAOC) contents. In addition, increasing plant diversity can increase the stability of soil organic carbon by enhancing aggregate protection, changing mineral ion concentrations, and changing microbial community structure. Future studies are needed to investigate (1) how soil organic carbon content may be increased through integrated plant diversity and management options; (2) how the effects of plant diversity on soil organic carbon content and composition can be explored through long-term plant diversity field experiments in different ecosystems; (3) how the effects of plant diversity on soil organic carbon composition and stability can be examined using new experimental methods(e.g., isotope labeling); and (4) how the mechanisms underlying plant diversity effects on soil carbon content, composition and stability can be studied at different soil depths.

Aims Biodiversity plays an important role in regulating ecosystem functioning. Fire is an important disturbance factor in forest ecosystems, and both above- and below-ground biodiversity in forests can be significantly altered by fire. However, our understanding of how biodiversity affects relevant ecosystem functions such as forest biomass accumulation and nutrient availability (i.e., ecosystem multifunctionality, EMF) following prescribed burning is still poorly understood. Methods In this study, we selected Pinus koraiensis plantations in Hongqi Forestry Farm, Hegang City, Heilongjiang Province, where prescribed burning was conducted in 2018, and used structural equation modeling to assess the relationships between understory plant diversity (species diversity, functional diversity, traitefficiency, and traitquantity) and soil microbial diversity (fungi and bacteria) and EMF following prescribed burning when the forest environment stabilized four years after the prescribed burning. Important findings We found that the prescribed burning increased understory plant diversity and EMF. In aboveground plant diversity, both traitquantity (i.e., total leaf nitrogen per unit area) and functional diversity (i.e., FDis based on leaf dry matter content) were significantly positively correlated with EMF, while the effect of belowground microbial diversity on EMF was not significant. The prescribed burning explained the highest variation in EMF (33.7%), followed by traitquantity (27.5%) and functional diversity (13.9%). The results suggest that in P. koraiensis plantations, enhancing nutrient accumulation and trait diversity in the understory vegetation within the community is an effective strategy to improve EMF after prescribed burning. Meanwhile, in forest management in the context of global change, prescribed burning is not only an effective way to reduce forest fire risks, but will also play a positive role in maintaining the biodiversity of understory vegetation and EMF.

Aims Species diversity is a crucial component of biodiversity, directly affect ecosystem function and stability during forest succession. Therefore, it is of significant importance to investigate the changes in species diversity and their influencing factors during forest succession for accurately predicting forest ecological processes and biodiversity patterns.

Methods The study focused on three successional stages in the northern Da Hinggan Mountains: Betula platyphylla forest in the early stage, Betula platyphylla - Larix gmelinii mixed forest in the middle stage and Larix gmeliniiforest in the late stage. The study employed a space-for-time substitution to analyze the changes in species diversity during forest succession and explore the relationship between species diversity and environmental factors in cold temperate zone of China.

Important findings The results demonstrated that: (1) Species richness and diversity significantly increased during forest succession. The Margalef richness index and Shannon-Wiener index were 2.42 and 2.69 in the early stage of succession, and 5.90 and 3.43 in the late stage of succession. However, Pielou evenness index showed no significant difference. (2) As succession proceeded, the dissimilarity between plant communities gradually increased, indicated by the increased Jaccard, Sorenson and Bray-Curtis indices. (3) Soil pH, soil organic matter content, total nitrogen content, and total phosphorus content significantly influence species diversity during succession. Specifically, total nitrogen content and total phosphorus content were the primary factors affecting species diversity in the early and middle stages of succession, while soil pH and soil organic matter content were the dominate factors influencing species diversity in the late stage. (4) The influence of stand spatial structure on species diversity also increased over succession, where angular scale and size ratio emerge as the main spatial structure factors. These results underscore the dominant role of soil factors in shaping species diversity during forest succession in the northern Da Hinggan Mountains, while the influence of stand spatial structure on species diversity in the process of forest succession should not be overlooked.

Aims In order to understand the development and evolution of xerophyte flora, it is important to explore the effects of the Quaternary climatic fluctuations and geological events on the distribution, genetic differentiation and evolution of Haloxylon ammodendron and H. persicum in the Gurbantünggüt Desert.

Methods Two chloroplast DNA spacers (trnS-trnG and trnV) were sequenced for 225 individuals from 19 naturally distributed H. ammodendron populations and 106 individuals from 12 H. persicum populations in Xinjiang. Haplotype Network analysis (Network), Principal Co-ordinates Analysis (PCoA), Analysis of Molecular Variance (AMOVA), Bayesian inference trees (BEAST), and Geographically weighted regression (GWR) were integrated to reveal the genetic diversity and environmental interpretation of different geographic populations within and between species, to estimate the time of interspecific lineage divergence and to analyze the demographical history.

Important findings (1) A total of 21 chloroplast haplotypes were identified, and H. ammodendron and H. persicum were clustered into independent clades. (2) Nearly 80% of the genetic variation occurred between species and among different geographical populations of H. ammodendron. The interspecies differentiation occurred from the late Pliocene to the early Pleistocene, which may have been affected by increasing aridity, mountain uplift on the Qingzang Plateau and desert expansion. (3) The results of the geographically weighted regression model showed distinct effects of the environmental factors on spatial heterogeneity of genetic diversity for H. ammodendron and H. persicum. On the whole, the climatic and soil factors had dominated the spatial pattern of genetic diversity for H. ammodendron and H. persicum. In the southern margin of the Gurbantünggüt Desert, climatic factors had positive effects on genetic diversity of H. ammodendron and H. persicum. In the southwestern margin of the desert, climatic factors had a positive effect on H. persicum, while soil factors had a negative effect on H. ammodendron. In the southeastern part of the desert, soil factors had a positive effect on H. ammodendron and a negative effect on H. persicum. In the Altay Region, climatic factors positively influenced both H. ammodendron and H. persicum.

Aims Biodiversity is important for maintaining multiple ecosystem functions and enhancing community resilience to disturbance. Selection effect and niche complementarity effect are two widely discussed mechanisms for maintaining ecosystem function, but the understanding of how these two mechanisms maintain forest ecosystem multifunctionality (EMF) under climate change is still limited. It is essential to deepen our understanding of these mechanisms, particularly in assessing whether there are differences in their effectiveness across different climatic zones.

Methods Based on plots distributed in natural forests of middle temperate and cold temperate zones in northeastern China, we used functional trait diversity (FD_{q= 0}), single and multidimensional trait functional dispersion indices (FDis) to represent the niche complementarity effect, and community weighted mean trait values (CWM) to represent the selection effect. We also explored the driving force of EMF to climate change by using multivariate linear models and partial least squares path modeling (PLS-PM; structural equation model).

Important findings (1) In middle temperate forests, two attributes of biodiversity (tree species diversity (SR) and FD_{q= 0}) had significant positive effects on EMF, and FD_{q= 0} had stronger effects than SR. In cold temperate forests, no significant relationship between biodiversity and EMF (BEMF) was found. (2) In middle temperate forest communities, the effects of SR on EMF were mediated by trait differences and community weighted mean maximum tree height (CWM_Hmax) value. Both selection effect and niche complementarity effect simultaneously maintained EMF in middle temperate forests, with selection effect slightly higher than complementarity effect. CWM_Hmax was the main biotic factor influencing cold temperate forest EMF, and selection effect was the main driving force on EMF in these forests. SR and trait differences did not have a significant promoting effect on EMF. (3) Due to the “insurance effect” of biodiversity, middle temperate forests had a stronger resistance to climate change. Climate factors had no significant impact on SR, trait differences, CWM_Hmax and EMF. However, cold temperate forests were sensitive to climate change, and climatic factors were important abiotic factors affecting EMF. Higher annual mean air temperature and precipitation significantly altered community trait composition (e.g., CWM_Hmax), diluting the contribution of species with high competitiveness and fitness traits (e.g., maximum tree height (H_max) trait) to ecosystem functions, and reducing the strength of the selection effect. This study highlights the importance of biodiversity for maintaining forest EMF, and demonstrates that both selection effect and complementarity effect are driving forces for temperate forest EMF in northeastern China.

For many plants, nectar is hidden in the depth of nectar spurs. The diverse morphology and length of nectar spurs can attract pollinators with various proboscis lengths and promote the differentiation of pollination niche, which plays an important role in the formation of species diversity. Therefore, nectar spur is considered as a key innovation trait in promoting speciation and an ideal trait for studying floral evolution and plant-pollinator coevolution in angiosperm. This review systematically summarizes the worldwide plant taxonomic databases and published articles, classifies the nectar spur plants, and reviews the diversity and evolutionary mechanisms of nectar spur plants. We investigated 3 427 nectar spur species belonging to 13 orders, 23 families and 271 genera of angiosperm. Among them, Orchidaceae has the largest number of species, with 1 536 species, following by Papaveraceae with 487 species, Ranunculaceae with 351 species, Balsaminaceae with 284 species and Violaceae with 197 species, accounting for 83.3% of all the species. According to the sources of the development of nectar spurs, the nectar spurs can be divided into six types: petal spur, corolla spur, sepal spur, calyx spur, tepal spur and hypanthium spur. The petal spurs are the predominant type, detected in 212 genera. The average length of nectar spurs in Balsaminaceae is the longest (23.8 mm) among the 2 546 species whose nectar spurs have been measured. The shortest nectar spurs are reported in Lycelandaceae, which are only 1.6 mm on average. Most nectar spurs have different degrees of curvature, likely helping to improve the pollination efficiency. The number of nectar spur(s) in a flower ranges from 1 to 6, and most species have only one nectar spur in a flower. Multiple nectar spurs may increase the visiting time of pollinators. Some plants in Orchidaceae and Violaceae have appendages inside the nectar spurs, which may have the function of nectar secretion. The pollinators of plants with nectar spur mainly comprise insects from Hymenoptera, Lepidoptera, and some long-proboscis species from Diptera and birds. Nectar robbers are mainly bees and birds. There is a general association of geographic mosaic theory of coevolution between the length of nectar spur and the length of pollinator proboscis. Evolutionary ecologists have proposed the hypothesis of “Darwin’s Mechanistic Model” and “The Pollinator Shift Model” to explain this phenomenon. In future studies of the mechanisms of nectar spur evolution, we should not only focus on the morphological characteristics of spur length and proboscis length and the pollination ecology, but also explore the driving forces of nectar spurs evolution from cell division/elongation, functional genes, abiotic factors, with the help of novel technological approaches including developmental anatomy and genomics.

Aims The region around the South China Sea is a relatively independent semi closed geographical unit, which can be divided into eight areas, including the coast of South China, Hainan Island, Taiwan Island, Indo-China Peninsula, Malay Peninsula, Kalimantan Island, Palawan Island, and Luzon Island. The region around the South China Sea is one of the regions with the most concentrated distribution of mangrove plants in the world. This study aims to explore the geographical distribution pattern and the underlying mechanisms of mangrove species in the eight regions around the South China Sea.

Methods Species richness and distribution of mangrove in the region around the South China Sea and other regions worldwide were obtained through extensive literature survey and mapped with ArcGIS. Species distribution map with 1° × 1° grid of four typical mangrove taxa, i.e. Rhizophoraceae, Malvaceae, Sonneratia, Avicennia, were drawn by DIVA-GIS 7.5.0. The migration history and route and its main influencing factors were explored through literature survey in ISI Web of Science.

Important findings (1) There are 39 species of true mangroves and 14 species of semi-mangroves distributed in this region, mostly distributed in Malay Peninsula, Kalimantan Island, Hainan Island, Indo-China Peninsula, Luzon Island. (2) All mangrove species are widespread in the region, which may be caused by the fact that South China Sea has completely different ocean current and monsoon directions in summer and winter, promoting the long-distance dispersals of mangrove plants. (3) There is a certain internal circulation in the northern and southern parts of the South China Sea, and resulting in the appearance of relatively isolated genetic lineages on both sides of the line connecting Cam Ranh Bay and the northern tip of Palawan Island, especially for the true mangroves such as Excoecaria agallocha, Lumnitzera racemose and Aegiceras corniculatum. (4) The sea level decreased by about 120 m during the Pleistocene, which profoundly affected the distribution pattern and migration route of mangroves in the region. In the future, phylogeographical studies using updated molecular technology, especially genomic data, is suggested to explore the dispersal history of mangrove plants and their future evolutionary trend under global climate change.

Aims Biodiversity loss threatens ecosystem functions. Investigating the effect of biodiversity on the ecological stoichiometry of plant nutrients, therefore, can help reveal the mechanisms of the effect of biodiversity on ecosystem functions.

Methods Using a tree species diversity experiment in subtropical China, Cunninghamia lanceolatafrom plots with different tree species richness (1, 4, 8, 16, 32) were selected as focal tree species. The effects of neighborhood species richness (NSR), functional trait dissimilarities between neighborhood tree species and the focal tree, neighborhood competition index (NCI) on foliar nitrogen (N), phosphorus (P) content and N:P of C. lanceolata were investigated.

Important findings (1) The results showed that the dissimilarity in specific root length (SRL_diss) between neighborhood trees and focal trees significantly increased the foliar P content of C. lanceolata, while the dissimilarity in root tissue density (RTD_diss) significantly decreased the foliar N content of C. lanceolata. (2) Neighborhood competition significantly decreased the foliar N content and N:P of C. lanceolata. (3) The interaction effects of NCI and SRL_diss, as well as the interaction between NSR and SRL_diss significantly reduced the foliar P content of C. lanceolata. The result indicates that the positive effect of SRL_diss on the foliar P content of C. lanceolata decreased with increasing NSR, and the positive effect of SRL_diss on the foliar P content of C. lanceolata decreased with increasing NCI. (4) The interaction between NSR and phylogenetic dissimilarity (NP_diss) significantly increased foliar N:P of C. lanceolata, demonstrating that the negative effect of NP_diss on the foliar N:P content of C. lanceolata decreased with increasing NSR. Our results indicated that the foliar P content of C. lanceolata was significantly enhanced by mixing with tree species with different trait dissimilarities, while foliar N content of C. lanceolata was decreased by neighborhood competition. Tree species richness can help mitigate the adverse effects of interspecific competition on C. lanceolata through niche complementation when mixing with species that have greater trait dissimilarity.

Arbuscular mycorrhiza (AM) is one of the oldest symbionts between plants and soil microorganisms, and about 80% terrestrial plant species can associate with AM fungi on earth. Because of the stable climate and poor soil phosphorus content in tropical and subtropical forests, this mutualistic symbiosis is much more common there. Previous studies have extensively investigated the diversity of AM fungi in tropical and subtropical forests, and have shown that AM fungi can promote plant recruitment and growth. However, this positive effect of AM fungi on plants (i.e., the positive plant-soil feedback) can weaken the contribution of the negative plant-soil feedback (caused by soil-borne pathogens) to maintaining tree species diversity, which appears to contradict with the surprisingly high tree diversity and high proportion of rare tree species in tropical and subtropical forests. Recently, a mounting number of empirical studies have found that the diversity of AM fungi varies significantly in different habitats and AM colonization depends on the identity of host species, thereby affecting the fitness of plants and further shaping the plant community structure. Through synthesizing the current research about the diversity of AM fungi in promoting plant coexistence and maintaining community diversity, we expect to put forward a promising study direction for testing the “rare species advantage” hypothesis, therefore improving the conservation of rare plant species.

Aims The relationship between biodiversity and ecosystem function is one of the hotspots in ecological research. In the past, the research on the relationship between biodiversity and ecosystem function only focused on the experimental or observational investigation of single ecosystem function (SEF), ignoring the most essential value that ecosystem can provide multiple functions and services at the same time. Identifying the relationship between plant functional diversity and ecosystem multifunctionality (EMF) can provide a clear understanding of changes in ecosystem function.

Methods In this study, Bayanbulak alpine meadow was taken as the study area, and five altitude sites were set at an interval of 200 m from 2 194 to 3 062 m above sea level. Soil total nitrogen content, nitrate nitrogen content, ammonium nitrogen content, total phosphorus content, available phosphorus content, total potassium content, available potassium content, soil density, aboveground and underground biomass of plant community were selected to characterize EMF, which were closely related to nutrient cycling, soil organic carbon accumulation and plant growth.

Important findings (1) The species composition of the plant community varied greatly along the altitude gradient, and the species richness at the altitude of 2 600 m was significantly higher than that at the other altitudes. Functional evenness index (FEve), functional richness index (FRic) and functional dispersion index (FDis) all showed a “single peak” trend with the rise of altitude, and the highest values were found at 2 600, 2 800 and 2 800 m, respectively. Rao’ quadratic entropy (Rao’Q) showed a monotonically decreasing trend. (2) FRic and FDis at each altitude were positively correlated with soil EMF, which accounted for 47% and 43% of the variation in EMF, respectively. FEve was significantly correlated with nutrient cycling index and soil organic carbon storage index at the altitude of 2 600 m. Rao’Q at 3 000 m was significantly correlated with soil nutrient cycling index, organic carbon storage and EMF. The relationship between plant functional diversity and EMF along the altitude gradient was analyzed by constructing a structural equation model, which showed that altitude could exert impacts on EMF through changing functional diversity, with the greatest effect of functional richness on EMF. In conclusion, with the alteration of altitude, the functional diversity may result in changes, thereby affect the SEF and EMF, and the functional diversity is important to maintain the EMF.

Aims Plant diversity is the basis for plant communities to maintain ecosystem stability. Despite the scarcity of vegetation, desert steppes play an irreplaceable ecological service function in terms of wind-break and sand- fixation, etc. However, how plant diversity in desert steppes responds to long-term extreme precipitation changes still remains poorly understood.

Methods Based on a long-term field experiment involving five precipitation treatments (50% reduction, 30% reduction, natural, 30% increase, and 50% increase) conducted in a desert steppe in Ningxia since 2014, the changing characteristics of plant biomass, species diversity and their relationships with soil properties were studied from May to October in 2020.

Important findings During the growing season, plant community biomass, Patrick richness index and Shannon-Wiener diversity index tended to increase first and then decrease, whereas no obvious regularities in Pielou evenness index and Simpson dominance index. Compared with the natural precipitation, the decreased precipitation had less effect on plant biomass and diversity, especially the 30% reduction in precipitation. In most cases, the increased precipitation stimulated the growth of Sophora alopecuroides, Stipa brevifloraand Pennisetum centrasiaticum,and thus increasing plant biomass. However, it did not significantly change plant diversity when precipitation increased, especially the 30% increase of precipitation. Plant biomass was significantly affected by soil urease activity, temperature, water content, pH, phosphatase activity and sucrase activity, while plant diversity was significantly affected by soil water content, electrical conductivity, and urease activity. In general, the results indicated that plants have high adaptability to moderate or even extreme drought in the research area under seven consecutive years of changing precipitation; moderately increasing precipitation increased soil water availability, enhanced exchangeable ion mobility, and stimulated enzyme activity, thereby promoting plant growth. However, the continuous increase of precipitation leaded to the increase of plant biomass and plant water consumption, resulting in the lack of soil water in the late growth season and then the early completion of the life cycle of some plants.

Aims Understanding the effect of tourism disturbances on soil microbial diversity and community structure is necessary for the restoration and management of environmental resources in tourist areas. Therefore, we conducted a field survey in Beijing Songshan National Nature Reserve, to reveal the effect of different tourism disturbance intensity on soil microorganisms in a Pinus tabuliformis forest.

Methods Three intensity groups, high disturbance (HD), low disturbance (LD) and no disturbance (ND), were conducted in the P. tabuliformis forest. We investigated microhabitat conditions and measured soil physicochemical properties. Next generation sequencing technique was used to determine the diversity and community structure of soil microorganisms. Then, we evaluated the impact of tourism disturbance intensity on soil microorganisms.

Important findings 1) HD significantly reduced soil fungal alpha diversity, and LD significantly reduced soil fungal phylogenetic diversity. Soil fungal diversity showed a decreasing trend, and soil bacterial diversity showed an increasing trend with increasing disturbance intensity. 2) For soil fungal community structure, the dominant phylum of three intensity groups were Basidiomycota and Ascomycota. HD disturbance significantly affected the relative abundance of Ascomycota, but had no effect on Basidiomycota, LD had no effect on both of them. LEfSe analysis showed that indicators of ND were Pseudogymnoascus and three species (Oidiodendron griseum, Acrodontium hydnicola, Metacordyceps chlamydosporia); indicator of HD was Clavariaceae; there was no indicator in LD. 3) For bacterial community structure, the dominant phylum of three intensity groups were Proteobacteria, Actinobacteria and Acidobacteria, but HD and LD had no effect on them. LEfSe showed that indicators of ND accounted for 82.05% of total indicators, and the most indicative ones were Gaiellales and Solirubrobacterales; indicators of HD accounted for 17.95% of total indicators, they mainly manifested as pathogenic indicator bacteria and bacterial groups related to human activities, the most indicative ones were Flavobacteriia and one genus of Verrucomicrobia; there was no indicator in LD. 4) Partial Least Squares Path Modeling (PLS-PM) found disturbance intensity significantly impacted microhabitat and alpha diversity of soil fungi. Redundancy analysis showed that soil and microhabitat condition explained 71.35% and 74.47% of variations in community structure of fungi and bacteria under different intensity group, respectively. Tree diameter at breast height, herb cover and litter cover were the main factors that altered fungal and bacterial community structure. In conclusion, tourism disturbance significantly reduced alpha diversity and impacted community structure of soil microbiota in the P. tabuliformis forest, and the degree of influence associated with disturbance intensity and the kind of microorganisms. Moreover, the impact was also controlled by microhabitat and soil physical and chemical properties. Therefore, future attentions should be paid to the restoration of microhabitats and soil conditions in tourism areas.

Understanding the response patterns and potential mechanisms of structure and function in grassland ecosystems to nitrogen (N) enrichment is essential to evaluate ecological impacts of external N input. The muti-level N manipulative experiment offers the possibility to explore the nonlinear response patterns and associated mechanisms of structure and function in grassland ecosystems to additional N input. In this review, we summarized the impacts of additional N inputs on community diversity, carbon (C) and N cycling in grassland ecosystems around the world. Numerous studies illustrated that N enrichment induced the decline of plant species diversity, plant functional diversity and soil bacteria richness in grassland ecosystems, yet the change of fungal diversity was not significant. Above- and below-ground plant productivity showed different responses to N input: aboveground plant productivity exhibited initial increasing and subsequent saturation trends, but root productivity and root:shoot ratio showed downward patterns, and root turnover rate appeared a single-peak pattern of first increasing and then decreasing with the continuous increase of N addition rate. Meanwhile, different C decomposition processes responded variously to N enrichment. Specifically, litter decomposition rates exhibited multiple response of “exponential decrease, liner increase or insignificant change with N addition level”. However, the relationship of soil respiration and CH₄ consumption with N addition was dominated by a single peak trend of increasing at low to medium N levels but declining at high N levels. Likewise, different soil C fractions showed multiple response patterns to N input. N addition generally stimulated soil C storage and particulate organic C accumulation, while the mineral-associated organic C exhibited divergent responses of “increase, unaltered, and decrease” along the N addition gradient. In addition, plant N uptake exhibited initial increasing and subsequent situation trends along N addition gradients, while different soil N transformation processes showed differentiated responses along N addition gradients and the relationship between N₂O emission and N addition rate varied among various grassland ecosystems. An exponential increase of N₂O fluxes with N addition rate was observed in temperate grasslands, while the patterns of first increase and then saturation or linear increase of the N-induced changes in N₂O emissions had been discovered in alpine grasslands. Future studies should focus on the nonlinear responses of rhizosphere processes and phosphorus (P) cycle to external N input, and also explore potential mechanisms from the aspect of multi-dimensional biodiversity changes.

Aims Plant diversity monitoring is the basis of biodiversity assessment and developing conservation policy. Traditional forest plant diversity monitoring is mainly based on field surveys, which is difficult to quickly obtain the spatial distribution and dynamic change of forest plant diversity. The development of remote sensing technology provides an important tool for assessing forest plant diversity at the regional scale. In this study, we explored two methods of forest plant diversity estimation based on Sentinel-2A satellite images and field data in three selected national nature reserves (Liangshui, Fenglin, and Hunchun).

Methods We used two methods to estimate forest plant diversity: (1) Direct estimation based on spectral diversity at the pixel and cluster scales, respectively; (2) Indirect estimation based on random forest regression. The spectral diversity was calculated based on the coefficient of variation and convex hull area at the pixel scale, respectively. K-means clustering method was used for cluster analysis to calculate the spectral diversity between clusters. For the indirect estimation, we used 10-fold cross validation to select characteristic variables for later diversity calculation.

Important findings Our results showed that: (1) At the pixel scale, the estimation accuracy of Shannon-Wiener diversity index based on convex hull area (R²= 0.74) was better than that of coefficient of variation (R²= 0.60); (2) The pixel-based estimation accuracy of Shannon-Wiener diversity index outperformed clustering basis (R²= 0.59); (3) Based on six feature variables, the Shannon-Wiener diversity index was best estimated using the random forest regression algorithm (R²= 0.79); (4) Both the Simpson diversity index and species richness could not be accurately estimated by the above methods. Our findings indicate the capability of Sentinel-2A satellite images to estimate the Shannon-Wiener diversity index, providing reference and basis for forest plant diversity estimation at a large scale.

Aims Livestock grazing is one of the most important factors affecting grassland plant diversity. However, the information on the effects of different livestock types and their grazing behaviors on grassland plant diversity and community composition are less available. A better understanding of the changes in plant diversity and community composition in response to the grazing of various livestock types is essential to the management and preservation of grassland biodiversity.

Methods We conducted a grazing experiment in a typical steppe of Nei Mongol to examine the effects of different livestock species (cattle, goat, sheep) and their behaviors (forage selection and grazing aggregation) on plant diversity (i.e., α, β and γ diversity) and community composition.

Important findings Our results showed that: (1) cattle, goat, and sheep grazing all increased plant α, β, and γ diversity at moderate grazing intensity, and the increase was the largest and significant under cattle grazing. (2) Three livestock species all changed community structure; sheep grazing reduced the relative abundance of dominant short grass Cleistogenes squarrosa, which is in contrary to the changes in community structure induced by cattle and goat grazing. (3) Cattle and goat grazing significantly reduced the aboveground biomass of dominant species, including tall grasses Leymus chinensis and Stipa grandis and short grass C. squarrosa, while sheep grazing only decreased that of short grass C. squarrosa. Cattle grazing also had a lower spatial aggregation than that of goat and sheep. (4) Plant diversity decreased with the increase of the aboveground biomass of either tall or short dominant species, indicating that livestock grazing promoted plant species diversity by reducing plant aboveground biomass of dominant species. (5) Plant diversity decreased with the increase in spatial aggregation of livestock grazing, indicating a lower aggregation benefiting plant diversity maintenance. Overall, our study suggests that grazing animal types should be considered along with grazing intensity in the development of grazing management regime for better conservation and sustainable use of the grassland resources.

Aims To further understand how community functional diversity drives biomass change following nitrogen (N) addition, a nitrogen addition experiment was conducted in an alpine grassland.

Methods Species composition of community and six functional traits of common species were measured in a short-term N addition experiment in Bayanbulak alpine grassland of Tianshan Mountains. We compared the response patterns of species diversity, functional diversity, and community level traits, and quantified the relative contribution of those factors to community biomass variation.

Important findings Both aboveground and belowground biomass increased following short-term N addition, with higher proportional enhancement of aboveground biomass. N addition reduced functional diversity, but did not affect species diversity. At the community level, height and leaf carbon content increased following N addition, whereas specific leaf area, seed mass, and leaf phosphorus content decreased. The variations of species diversity contributed less to the variations of community biomass change, whereas functional diversity and community level traits explained most of the variation of community biomass. Our results support the mass ratio hypothesis. In conclusion, community level functional traits and functional diversity were sensitive to short-term N addition, and played a key role in driving community biomass.

Aims A particular set of species that have the potential to inhabit a local community but are locally absent is called dark diversity. Our aim was to investigate the impacts of plant characteristics and environmental factors on the dark diversity in a broadleaved Korean pine (Pinus koraiensis) forest.

Methods The study was conducted based on survey data of a 9-hm² broadleaved Korean pine forest in the Liangshui National Nature Reserve of Heilongjiang Province. We estimated the dark diversity probability of main species by using the Beals index. The correlations between the shade tolerance index, importance value and dark diversity probability were evaluated, and the effects of life form and shade tolerance on dark diversity probability were analyzed at the individual level. The correlations between community completeness and environmental factors, and community completeness and species diversity were investigated at the plot level.

Important findings The results showed that: (1) Average dark diversity probability for these species in this plot was 77.79%. For arbors, Juglans mandshurica had the highest dark diversity probability of 97.21%; however, for shrubs, the dark diversity probability of Viburnum opulus subsp. calvescens and Rhamnus davuricawere the highest, at 98.01%. (2) The dark diversity probability was negatively correlated with the importance value. However, the shade tolerance index was positively correlated with the importance value. (3) There was no significant difference in the dark diversity probability between arbors and shrubs, but the dark diversity probability of shade-intolerant species was significantly higher than that of shade-tolerant species. (4) Slope and convexity were both significantly positively correlated with community completeness. Soil organic matter, soil available potassium, soil bulk density, mass moisture content, soil pH, soil available nitrogen, and soil total nitrogen were not significantly related to community completeness; however, soil available phosphorus, soil total phosphorus and volumetric moisture content were all significantly negatively correlated with community completeness. The correlations between the species diversity indices and community completeness were significantly positive. In short, the dark diversity probability of shade-intolerant species and rare species in the broadleaved Korean pine forest was relatively high. Slope, convexity, soil available phosphorus, soil total phosphorus and volumetric moisture content were the main environmental factors that significantly influenced community completeness. The higher the community completeness was, the higher the species diversity of the community.

Aims In order to explore the important ecological function of moss in forest ecosystems in the southeast Xizang and provide a theoretical basis for the influence of forest disturbance on forest surface vegetation, the diversity and biomass characteristics of ground moss per unit area in different habitats in the Sygera Mountain of southeast Xizang.

Methods We collected the surface moss in the Sygera Mountain of the southeast Xizang as the investigation object, and selected 7 sample plots with similar forest stand, slope direction, slope and terrain composition, with each plot size of 100 m × 100 m. We took canopy gap of each sample plot as the center, and three different habitats (canopy gap, forest edge and understory) were selected in four directions to set 50 cm × 50 cm quadrats, with 12 quadrats for each sample plot and 168 quadrats in total. Moss survey and collection were carried out in each quadrat.

Important findings (1) 24 families, 63 genera and 110 species of moss were found in the study area, in which there were 8 dominant families, which were Pottiaceae, Dicranaceae, Polytrichaceae, Mniaceae, Bryaceae, Grimmiaceae, Brachytheciaceae and Hypnaceae. There were obvious distribution rules of different moss families, such as Dicranaceae and Bryaceae were widely distributed at all elevations, and Polytrichaceae, Bryaceae and Mniaceae were distributed at altitudes from 3 700 to 4 300 m. Most of Pottiaceae were distributed over 4 300 m. (2) The habitat of canopy gap was more complex than those of forest edge and understory and it interfered with moss composition and community structure, in which the moss community had the most species and the most complex structure. However, the moss community in understory had the least species and the simplest structure. The biomass of ground moss was the highest in the gap, followed by the edge and the lowest in the understory. (3) The biomass of ground moss was not only affected by species composition, coverage, body shape and community structure, but also resulted from the interaction of many factors rather than any one single factor.

Aims The mountainous region on the east side of the Qingzang Plateau is a biodiversity hotspot and a refuge for many plants during the ice age. The unique topography allows geographic isolation to play an important role in shaping population genetic patterns. The white birch (Betula platyphylla) population located on the eastern side of the Qingzang Plateau shows a fragmented distribution, which is isolated by valleys, mountains, and rivers, and the genetic pattern is still unclear.

Methods We used 11 pairs of nuclear microsatellite molecular markers to analyze the genetic diversity and structure of 13 birch populations located in the eastern mountainous area of the Qingzang Plateau.

Important findings A total of 114 alleles were detected in 412 individuals, and we found a high level of overall genetic diversity (expected heterozygosity (H_E) = 0.579; observed heterozygosity (H_O) = 0.555), a medium level of genetic differentiation (genetic differentiation coefficient (F_st) = 0.127), and a large pairwise genetic distance between groups (F_st = 0.017-0.319). The genetic distance was significantly positively correlated with geographic distance. The cluster analysis divides all individuals into two groups, bounded by the Yalong River Canyon. The population on the west side has lower genetic diversity and greater genetic differentiation than the population on the east side. This study shows that the geographic isolation caused by the unique topography on the eastern side of the Qingzang Plateau has profoundly affected the genetic diversity and genetic structure of white birch. The marginal populations located in the Yunnan area have already faced the risk of reduced genetic diversity and should be given priority protection.

Interactions between plants and coexisting microorganisms have significant impacts on plant growth, development, and health. Human domestication has resulted in significant differences between modern crops and their wild ancestors in physiological and genetic characteristics and growth environment, which will inevitably affect the interaction between crops and their microbiomes. Understanding the impact of domestication on the diversity and community structure of microbiome and the mechanisms involved is an important theoretical basis for application of microbiome during crop improvement and breeding. In this review, we summarize the research progress of the effects of domestication on the community composition and diversity of root and shoot microbiome (bacteria and fungi) in crops. We also analyze the involved action pathways in shaping crop microbiomes by domestication, considering the domestication effect on crop morphology, root configuration, exudates and other physiological characteristics, and the change in growth environment. The research directions that need to be focused on in this field were proposed.

Aims The objectives were to reveal the response patterns of plant species diversity and above-ground biomass to nutrients addition and to clarify their relationships in alpine grasslands of Tianshan Mountains.
Methods The nitrogen (N), phosphorus (P) and potassium (K) addition experiments were conducted in Tianshan alpine grasslands. The single factor effects and the interaction effects on plant species diversity and above-ground biomass were studied from 2019 to 2020.
Important findings 1) Nutrient addition reduced plant species diversity of local community. Especially, the addition of N + P, N + K and N + P + K showed significant effects, suggesting that the decrease of soil niche dimension caused by multiple-nutrient addition was an important reason for local species loss. 2) Nutrient addition significantly increased above-ground biomass of local plant communities, with the highest above-ground biomass being found under N + P + K treatment, indicating that N was the first limiting resource, P and K became the limiting resources after N limiting was alleviated. 3) There was a negative linear regression between species diversity and above-ground biomass following two years of nutrient addition, which indicated that the dominant species but not species diversity determined above-ground biomass at our study site.

Aims The purpose of this study was to understand the effects of the second generation wild boar grazing on species diversity and soil physicochemical properties of coniferous-broad-leaved mixed forest in the Jiajin Mountain, and to provide reference for the maintenance of ecological stability and scientific grazing of the mixed coniferous and broad-leaved forest in this area.

Methods On the basis of comprehensive investigation, according to the number, area, behavior characteristics and activity range of wild boar, four grazing disturbance intensity (from strong to weak was followed by I, II, III, IV) were divided, and no disturbance state was set as control (CK) to explore species diversity and soil physicochemical properties under different grazing disturbance intensity.

Important findings (1) 172 species of vascular plants, belonging to 55 families and 117 genera, were recorded, with the families, genera and species of trees, shrubs and herbs reaching the highest under slight disturbance intensity (IV). (2) The responses of tree, shrub and herb diversity index to the disturbance gradient were basically the same, but the richness index (S), Shannon diversity index (H') and Simpson dominance index (D) reached the maximum under the IV level disturbance intensity, which were higher than those in CK. The diversity level tended to decline with the increase of disturbance intensity (IV-I). In addition, for Pielou evenness index (E), there was no significant difference among different disturbance intensity levels. (3) Compared with CK, soil water content, maximum water content and total nitrogen content decreased under wild boar grazing. The greater the grazing pressure, the greater the proportion of decline. The content of soil total porosity, total phosphorus, available phosphorus and organic matter content increased in the IV level of interference, and decreased significantly under the I-III level interference; the soil density increased with the increase of disturbance intensity. (4) Redundancy analysis showed that soil organic matter content, available phosphorus content, soil density, soil water content, soil porosity, total phosphorus content, total nitrogen content and diversity index were significantly correlated. The light disturbance intensity is beneficial to the richness of community species diversity, the improvement of soil fertility and soil structure, which is a positive factor for the maintenance of ecological stability of the mixed coniferous and broad-leaved forest in the Jiajin Mountain. The study provides a reference for the forest ecological environment protection and sustainable development in this area under the background of increasingly expanding grazing and animal husbandry and increasingly frequent disturbance of human activities.

Aims Grazing exclusion is an important intervention for restoring degraded grasslands. Understanding the changes of grassland productivity and plant diversity during the long-term grazing exclusion succession, as well as the relationship between diversity and productivity, are helpful for grassland restoration management and utilization.

Methods This study was conducted in a typical grassland system with a long-term grazing exclusion gradient, located at Yunwu Mountain National Nature Reserve in Ningxia Huizu Autonomous Region. The grassland communities under continuous grazing, 9 years of grazing exclusion, 26 years of grazing exclusion, and 34 years of grazing exclusion were chosen as the study objects. We tracked changes in aboveground net primary productivity (ANPP), species diversity and functional diversity, and quantified the relationships between diversity and productivity.

Important findings The results showed that grazing exclusion significantly increased ANPP, litter biomass, functional richness, and functional dispersion of typical grassland, but did not alter species richness, Shannon- Wiener index and functional evenness. In contrast, Simpson dominance index and Pielou evenness index significantly decreased after long-term grazing exclusion (34 years). In addition, grazing exclusion showed diverse effects on community-weighted means of different functional traits. The results of random forest model and variance partition analysis indicated that community-weighted mean functional traits accounted for 70.70% of ANPP variation, and plant height was identified as the most important trait. Functional diversity explained 36.86% of ANPP variation, mainly contributed by functional richness. In contrast, species diversity only explained 14.72% of ANPP variation. Therefore, the contribution of mean trait values and functional diversity to ANPP was much higher than that of species diversity in grassland after grazing exclusion. We suggest that community mean trait values and functional diversity should be incorporated into the studies of plant community dynamics during restoration succession, which will contribute to a comprehensive understanding of the relationship between plant diversity and ecosystem function, and provide basis for better realization of ecological restoration goals.

Aims We address the issue of adapting patch pattern for improved plant biodiversity conservation in sandy grasslands by assessing the role of edge type in the influences of patch pattern on plant diversity and functional traits. We test the hypotheses that plant richness, alpha and beta diversity would vary according to patch pattern but that these effects would vary according to edge type, through adaptation of plant functional traits. Methods Jointing satellite imagery interpretation, 705 plots from two-year surveys and spatial analysis, patch edges in center Hunshandak Sandland were categorized into four types. Duncan’s differences were tested across four edge types. Pearson’s correlation and redundancy analysis (RDA) were used to discern the patch contributions. Important findings Plant richness and diversity indices are closely related with patch patterns, these relations vary significantly across edge types, demonstrating different functional traits. For inward edge, edge metrics attributes to richness reduction and C₄ plant proportion, mean perimeter-area ratio (MPAR) positively related to nitrogen-fixed species proportion. For outward edge, mean patch fractal dimension (MPFD) negatively related to richness, MPAR positively related to the proportion of nitrogen-fixing species, edge metrics positively related to C₄ proportion. For inward nucleating edge, MPAR, total edge (TE) and landscape area (TLA) positively related to perennial plants, TE and TLA positively linked to insect-pollination plants. For outward nucleating edge, angle and pattern metrics positively related to Shannon-Wiener and Simpson index, negatively related to Pielou index, richness and animal-seed dispersing plants. Patch pattern distressing plant diversity through edge effects can be moderately interpreted by plant practical qualities and edge metrics. It must be well thought-out in landscape management, vegetation restoration and biodiversity conservation.

Aims Patterns of species richness are influenced by both ecological factors and processes. The formation mechanisms of macrophyte richness pattern have been mainly concentrated in a few aspects, such as geometric constraints, water-energy status, or random processes.
Methods In this study, using collected macrophyte species-level data in the Qaidam Basin, we examined macrophyte richness patterns along latitudinal and longitudinal gradients, and tested the mid-domain effect (MDE), area effect (AE), water-energy hypothesis, spatial autocorrelation, and habitat heterogeneity hypothesis for the geographical patterns.
Important findings Our study showed that the macrophyte richness in the Qaidam Basin showed a hump- shaped pattern along latitudinal and longitudinal gradients. Regression analyses indicated that MDE and AE, rather than water-energy hypothesis, spatial autocorrelation, or habitat heterogeneity hypothesis significantly influenced macrophyte richness in the Qaidam Basin. Variation partitioning showed that the explanatory power of MDE for longitudinal and latitudinal richness patterns of macrophyte was 68.41% and 66.91%, respectively. This result implies that macrophyte richness in the Qaidam Basin is mainly affected by geometric and dispersal restrictions. This study further confirms that geometric constraints and random processes may be important natural factors affecting the pattern of macrophyte richness in the arid area of Northwest China.

Over the recent decade, biodiversity and ecosystem multifunctionality (BEMF) has aroused as an emerging reserach hotspot in the filed of biodiversity and ecosystem functioning. Ecosystem multifunctionality is defined as the capacity of an ecosystem to provide multiple ecosystem functions simulateneously, it has received broad consideration by community and ecosystem ecologists. In this study, we first conducted a literature review of the research history in biodiversity and ecosystem multifunctionality. Next, we summarized the major trends in biodiversity and ecosystem multifunctionality research including the impacts of biodiversity dimensions, global change drivers and spatial-temporal scales on ecosystem multifunctionality. We reviewed the new research methods and research directions emerged in the field. We also defined a new concept, i.e., ecosystem multiserviceability (EMS) based on the distinction between ecosystem functions and ecosystem services. Finally, we briefly summarized the limitations in current research of biodiversity and ecosystem multifunctionality/multiserviceability (BEMF/BEMS) and presented the outlook for future study.

The stability of ecosystems determines whether they can sustainably provide key functions and services in the background of global changes. Ecosystem stability, particularly its relation with biodiversity, is one of the central issues in ecology. Whether biodiversity enhances or impairs ecosystem stability has historically aroused much debate. Based on early reviews and studies on different aspects of stability, here we summarized recent advances from three aspects. Firstly, several recent theoretical studies offered novel insights in understanding the multi- dimensionality of stability and the intrinsic link between different stability measures, and we provided an overview on these new insights. Secondly, we reviewed recent empirical and theoretical studies on biodiversity- stability relationships, including those in the context of multidimensional stability. Thirdly, we introduced the recently developed multi-scale stability framework, which provides new opportunity to understand the scaling of stability and extend diversity-stability relations to a multi-scale context. We ended with a discussion on future research questions and directions.

Aims How soil microbial diversity assembly, maintain and change is a key topic of ecology. A large number of studies show that soil microbial biodiversity is controlled not only by soil environment but also by plant species. However, due to strong covariation between the two factors in the field, it remains a challenge to isolate and clarify the role of plant diversity in regulating soil microbial biodiversity. Hence, here, we aim to clarify how plant diversity affects soil microbial diversity in environment-consistent artificial communities.
Methods In this study, we examined differences in species diversity of soil bacteria and fungi among plots subjected single- and mixed-sowing of three grass species with fertilization treatments after 13 years’ experiment on the eastern Qingzang (Tibetan) Plateau. We also analyzed the relationships between soil microbial diversity and edaphic factors as well as plant community attributes.
Important findings (1) The species richness and diversity of soil bacteria, not including soil fungi, significantly and consistently decreased in mixed-sowing plots relative to single-sowing plots, with higher relative abundances in proteobacteria and actinobacteria but lower in acidobacteria, bacteroidetes and planctomycetes in the mixed- sowing plots. (2) Soil pH and total nitrogen content significantly decreased while soil total phosphorus content increased in mixed-sowing plots relative to single-sowing plots. Fertilization significantly increased soil available phosphorus while decreased soil pH and soil humidity. However, variations in these edaphic factors contributed little in variation of soil microbial diversity. (3) Fertilization significantly increased plant aboveground biomass while decreasing richness of present plant species, which was also negatively associated with soil bacterial diversity. In short, this long-term field experiment clearly showed that mixed-sowing of common grass species did not promote diversity of soil microbes. This study provides new insight into management of grasses mixed-sowing artificial grasslands.

Aims β diversity reflects species turnover rate across environmental gradients, and this study attempts to use β diversity to reveal relevant ecological processes underlying the changes in plant community composition along a disturbance gradient induced by small burrowing herbivores.
Methods This study conducted a field survey at Gangcha County in the Qingzang Plateau to determine the effect of disturbance intensities of plateau pika (Ochotona curzoniae) on the β diversity of an alpine meadow measured by Whittaker’s index. Then a variance decomposition was used to measure the contribution of individual species to overall β diversity (SCBD) and single interference sites to overall β diversity (LCBD) according presence- absence community matrix.
Important findings The turnover rate of species in the plant community first increased and then decreased with the increase of the disturbance intensities induced by plateau pika. Species with intermediate site occupancy had a greater contribution to β diversity, in which Agropyron cristatum, Artemisia hedinii and Anemone rivular var. flore-minore were the single-species plants that contributed the most to the β diversity of the study regions. The disturbance plot T₀ with the absence of plateau pika had the greatest contribution to the β diversity of whole study region. LCBD of individual site was negetively related to species richness of that individual site, and had no significant correlation with the disturbed intensity of plateau pika. These results indicate that alpine meadows distributed in high LCBD and Agropyron cristatum, Artemisia hedinii and Anemone rivularis var. flore-minore with high SCBD should be protected to conserve plant diversity when the plateau pikas are present.

Aims Our objective was to explore mechanisms underlying the effects of transgressive overyielding and plant diversity effects associated with legume-grass mixtures in Zhaosu Basin, Yili Prefecture, Xinjiang Uygur Autonomous Region, China.
Methods Replicate plots (n = 3) were sown in 2013 as legume and grass monocultures (8 in total, including Vicia sativa, Avena sativa, Onobrychis viciaefolia, Bromus inermis, Trifolium pratense, Phleum pratense, Medicage sativa, Dactylis glomerata), a two-species mixture (AM2, annual legume and grass; PM2, perennial legume and grass), a four-species mixture (PM4, 2 perennial legumes and 2 grasses), a six-species mixture (PM6, 3 perennial legumes and 3 grasses), and three mixed-ratio combinations (legume : grass = 6:4, 5:5 and 4:6). Total plot productivity was measured as forage yield (dry matter) each summer between 2013 to 2015, which were used to calculate transgressive overyielding effect (OV), transgressive overyielding effect 1 (OV₁), and transgressive overyielding effect 2 (OV₂). Plant diversity effects were determined by calculating the complementary effect (CE), selection effect (SEF), and net biodiversity effects (∆Y).
Important findings The OV amplitudes of AM2 in 2013, 2014 and 3 years average were less than those of PM2 and PM6. The OV amplitude of AM2 in 2015 was greater than those of PM2, PM4 and PM6. The difference between the productivity of the mixed community and the yield of the most productive product species in the community components and the average yield of each species showed similar laws. CE of AM2 in 2013, 2014, and 3 years average was greater than PM2, PM4 and PM6 in the respective years. While SEF were much smaller than CE in AM2, changes in CE were relatively stable in PM2, PM4 and PM6. Fitted curves of species richness, species evenness, and forage yield (community productivity) predominantly showed a single maximum in PM4, yet productivity was highest in the 5:5 ratio plot. CE, SEF,and ∆ Y in perennial legume-grass mixtures decreased over time, which also led to declines in OV amplitude, OV₁ and OV₂, and their stability. Thus, in the initial study year, CE and SEF jointly dominated OV, OV₁ and OV₂ in perennial legume-grass mixtures. Over the next two growing years, SEF became the main factor that influenced OV, OV₁ and OV₂ in perennial legume-grass mixtures. OV, OV₁ and OV₂ of annual legume-grass mixtures were all influenced by CE from 2013 to 2015.

Aims Human disturbance is one of the main obstacles to the forward succession of karst grassland, exploring the response of grassland to disturbance in terms of soil microorganism can provide the basis for the restoration and rational utilization of karst land. Our objective was to study the effects of different human disturbances on soil microorganisms and the underlying mechanisms in a karst grassland ecosystem of northwestern Guangxi, China.
Methods Three patterns of disturbances (burning, mowing, and mowing plus root removal) and one control treatment (enclosure) were conducted at the long-term monitoring plots in the Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences. We analyzed the changes of soil microbial diversity and community structure by high-throughput sequencing, and determined their relationships with environmental factors (slope position, soil physicochemical properties).
Important findings 1) For α diversity, at both middle and lower slope positions, the burning treatment significantly reduced the fungal Chao1 index, while the mowing treatment significantly reduced the bacterial Shannon index and Pedigree diversity index. However, the mowing plus root removal treatment significantly reduced the fungal Chao1 index and the bacterial Shannon index, respectively, at middle and lower slope positions. 2) For microbial community structure, burning, mowing and mowing plus root removal treatments significantly reduced the relative abundance of Acidobacteria at both middle and lower slope positions, while the fire treatment significantly reduced the relative abundance of Ascomycota from 74.49% to 34.72% at the lower slope position. 3) Redundancy analysis showed that soil microbial biomass carbon explained 29.8% and 26.8% of the changes of bacterial and fungal α diversity, respectively, and 31.7% of the changes of bacterial community structure. Root biomass explained 13.9% and 10.3% of the changes of bacterial α diversity and fungal community structure, respectively. In conclusion, the three studied human disturbances have significantly negative influence on soil microbial α diversity as well as having a significant change in and changed community structure, and the degree of influence varied among the pattern of disturbances and the type of microorganisms. Moreover, the effects were also regulated by slope position. Long-term human disturbances mainly affected the diversity and structure of soil microbial communities by changing soil microbial biomass carbon and root biomass. The decreases of α diversity and Ascomycota will not be conducive to the maintenance of soil ecosystem stability, and the decrease of Acidobacteria will not facilitate to soil organic matter degradation and iron cycling. Therefore, the long-term human disturbances such as burning and mowing will induce the functional degradation of grassland ecosystem.

Aims In subtropical forests, topographic heterogeneity drives ecosystem structure and species composition by regulating the available nutrients, water and light needed for tree growth. A gap in current research is the role of topographic heterogeneity in plant species diversity and distribution in monsoon evergreen broad-leaved forests. Our study aims to fill this gap, providing scientific grounds for the conservation of biodiversity through an exploration of floral structure and ecosystem development in monsoon evergreen broad-leaved forests.
Methods Within a 30 hm² dynamics plot, we established 750 20 m × 20 m sample plots, using fuzzy C-mean clustering to classify different topographic types based on elevations, convexities, slopes, and aspects of each sample plots. We compared community composition and community species diversity between different topographic types, using Torus-translation tests to examine the relationship between floral species and topography.
Important findings We identified five distinct topography types: ridge (8.00 hm²), steep slope (6.04 hm²), less-steep slope (7.68 hm²), high plateau (2.76 hm²), and valley (5.52 hm²). We counted a total of 153 418 woody plant individuals with a diameter at breast height (DBH) ≥ 1 cm, belonging to 271 species, 179 genera and 79 families. Among the topographic types, we noted differences in species richness, plant density, proportion of different diameters, species diversity and the abundance of dominant species. When comparing species-area relationships between the five topographic types, we noticed that the ridge had the lowest number of species, while the valley had the highest. The cumulative species-individual relationships within the topographic types revealed that the ridge possesses the lowest cumulative rate. Of the 123 examined species, 67.5% were significantly related to at least one type of topography. Among species significantly related to topography, those species with significant negative correlation were more abundant in the ridge and steep slope topographic types. The opposite was true in steep slope, high plateau and valley. Based on our data, we determined that topographic heterogeneity contributed 7.8% to the maintenance of species diversity in our study area.

Aims Monitoring forest species diversity continuously and efficiently is important to maintain ecosystem services and achieve sustainability and conservation goals. In this paper, we explored the relationship between leaf biochemical and spectral properties and their inner linkage with species diversity, then estimated the forest species diversity based on a clustering algorithm using airborne imaging spectroscopy and Light Detection and Ranging (LiDAR) data in the Gutianshan National Nature Reserve of China.
Methods Firstly, we isolated individual tree crowns (ITCs) with the watershed algorithm from the LiDAR data. Then we calculated the optimal vegetation indices (VIs) representing the key biochemical properties from the hyperspectral data and selected optimal structural parameters from commonly used LiDAR-derived structural parameters based on correlation and stepwise regression analysis with the field samples. Finally, a self-adaptive Fuzzy C-Means (FCM) clustering algorithm was applied to map the species diversity (i.e. Richness, Shannon-Wiener index and Simpson index) in the study area for each 20 m × 20 m moving window.
Important findings The results indicated that biochemical components (chlorophyll a & b, total carotenoids, equivalent water thickness, specific leaf area, cellulose, lignin, nitrogen, phosphorus and carbon) could be well quantified by leaf spectrum using partial least squares regression (R² = 0.60-0.79, p < 0.01), and represented by hyperspectral VIs, namely, Transformed Chlorophyll Ratio Index/Optimization of Soil-adjusted Vegetation Index (TCARI/OSAVI), Carotenoid Reflectance Index (CRI), Water Band Index (WBI), Ratio Vegetation Index (RVI), Photochemical Reflectance Index (PRI) and Canopy Chlorophyll Concentration Index (CCCI). The individual tree isolation showed high accuracy (R ² = 0.77, RMSE = 16.48). The correlation and stepwise regression analysis showed tree height and skewness were the optimal structural parameters among seven commonly used forest structural parameters (R ² = 0.32, p < 0.01). The species diversity indices calculated from the self-adaptive FCM clustering algorithm based on the six VIs and two optimal structural parameters correlated well with the field measurements (species richness, R ² = 0.56, RMSE = 1.81; Shannon-Wiener index, R ² = 0.83, RMSE = 0.22; Simpson index, R ² = 0.85, RMSE = 0.09). With the clustering method combined with crown-by-crown variations in hyperspectral biochemical VIs and LiDAR-derived structural parameters, we created continuous maps of forest species diversity in the examined subtropical forest without the need to identify specific tree species. Our case study in Gutianshan showed the potential of airborne hyperspectral and LiDAR data in mapping species diversity of the subtropical evergreen broad-leaved forest. It could also provide a pathway for monitoring the state and changes of forest biodiversity at regional scales.

Aims Nitrogen (N) deposition has made great impacts on the structure and function of terrestrial ecosystems in recent decades, and N is known as the main limiting element of plant growth and primary productivity in the northern grassland of China. Species diversity and functional diversity have been widely recognized as key indicators of the mechanisms of biodiversity maintenance for ecosystem functions. However, the effect of long-term N addition on the relationship between species diversity and functional diversity, and the corresponding impacts on primary productivity have rarely been studied; particularly the underpinning mechanisms remain unclear. Our objective is to examine the effects and pathways of long-term N addition on species diversity, functional diversity and primary productivity in a typical steppe.
Methods A manipulative N addition experiment located in a typical steppe of the Nei Mongol grassland has been conducted for 18 years. The experimental design included seven levels of N addition rate (i.e., control, 0, 1.75, 5.25, 10.50, 17.50, 28.00 g·m^-2·a^-1) with nine replicates for each treatment. The plant functional traits of dominant species, species richness and composition, and aboveground net primary productivity (ANPP) were determined. In addition, species diversity, functional attribute diversity and community-weighted mean traits were calculated.
Important findings 1) N addition significantly reduced species richness and Shannon-Wiener index, but had little effect on functional diversity, including functional attribute diversity and community-weighted mean traits. 2) Structural equation model analyses showed that functional diversity was mainly affected by species richness, whereas the decrease in species diversity didn’t lead to the decrease in functional diversity. The community- weighted mean traits did not change under N addition, which was mainly due to the shift in functional group composition, that is, the proportion of perennial rhizome grass in plant community increased greatly under N addition. 3) The effect of N addition on ANPP was through direct pathways of species richness and shift in functional group composition, and further via an indirect pathway of community-weighted mean traits. Particularly, the community-weighted mean traits were the most important factors and explained 48% of total variation in ANPP, implying that the primary productivity is mainly determined by the biomass and functional traits of dominant species in the plant community. Our results well supported the mass-ratio hypothesis.

Aims Understanding the spatial patterns and maintenance mechanisms of biodiversity is one of the central issues in ecology and biogeography. Specifically, altitudinal patterns of biodiversity have been widely explored to represent to mimic the latitudinal patterns. However, previous studies on altitudinal patterns of plant diversity have focused mainly on the taxonomic diversity, with less attention paid to the comprehensive information of taxonomic, phylogenetic evolution and functional traits. In this study, we explored maintenance mechanisms of diversity of forest communities in Mount Guandi, by comparing the altitudinal patterns of taxonomic, phylogenetic and functional diversity, based on the systematic investigation of forest communities.
Methods 52 forest plots, each with an area of 30 m × 20 m and divided into six subplots (10 m × 10 m), were investigated along the altitudinal gradient (1 409-2 150 m) in Mount Guandi, Shanxi. Name, diameter at breast height (DBH) and height were identified and measured for each tree stem with DBH ≥3 cm at each plot; name, average height, coverage and basal diameter for each shrub species were identified and measured in two of the six subplots; name, abundance, coverage and average height for each herbaceous species were identified and measured for one quadrat of 1 m × 1 m in each subplot. The indices of taxonomic, phylogenetic and functional α and β diversity were then calculated.
Important findings Species richness (S), phylogenetic diversity (PD) and functional richness (FRic) increased along the altitudinal gradient, especially in altitudes above 1 800 m. Total β diversity (β_total) and replacement β diversity (β_repl) increased, while the richness difference (β_rich) decreased, along the altitudinal gradient. The patterns of taxonomic, phylogenetic and functional diversity were significantly different between woody and herbaceous plants. S and Shannon-Wiener diversity (H′) of herbaceous plants increased more obvious along the altitude than those of woody plants. Topographic factors regulated the pattern of the herbaceous plant richness, while historical process regulated the woody plant richness. Along the altitude, β_total increased more obvious for the woody plants than for the herbaceous plants. β_repl and β_rich of woody plant showed a unimodal pattern and U-shaped pattern, while those of herbaceous plants increased or decreased, respectively. Taxonomic, phylogenetic and functional β diversity of both woody and herbaceous plants among communities increased with the environmental and geographical distances. Environmental distance had a relatively stronger effects than geographical distance on β diversity of woody plants, while environmental distance and geographical distance jointly influenced β diversity of the herbaceous plants.

Aims Larch forests are important for timber harvesting and water-soil conservation in North China. To explore the distribution, community structure and species diversity of larch forests is important for the vegetation conservation and sustainable utilization in North China.
Methods We collected species composition and local environment for 215 forest plots dominated by three common larch species, namely, Larix principis-rupprechtii, L. kaempferi and L. chinensis, in North China during 2000-2017. Among these types, L. kaempferi forests are planted, while L. chinensis forests are almost natural, and most of L. principis-rupprechtii forests are natural. Based these data, we used the canonical correspondence analysis (CCA) to explore the relationship between species composition and environment. We also explored the pattern of community structure and species diversity of these three forests in relation to environmental factors.
Important findings Mean annual air temperature (MAT) was the most important factor for the distribution of these larch forests. The proportion of natural forest decreased, while that of planted forest increased, with MAT. Diameter at breast height (DBH) and height distribution of three larch forests were right-skewed, indicating that all of these larch forests are at relatively stable successional stage. Species richness differ remarkably among different larch forests, which was highest in the L. chinensis forests (39.3 ± 17.9), followed by the L. kaempferi forests (37.4 ± 22.4), and lowest in the L. principis-rupprechtii forests (planted forests 27.2 ± 17.7, natural forests 27.5 ± 13.8). Species richness, the maximum DBH and the maximum height decreased with latitudes and longitudes. Species richness, the maximum DBH and the maximum height increased with annual precipitation. However, species richness showed no significant trend, and the maximum height increased, while the maximum DBH decreased, with MAT. The patterns of species richness along geographical and climatic gradients were consistent between the planted, the natural and the overall (including both planted and natural) larch forests. However, the patterns of community structure differed remarkably among planted, natural and overall larch forests. The maximum height of planted forests increased, while that of natural forests decreased, with latitude and longitude. The maximum DBH and height of natural forests decreased, while those of planted forests increased, with MAT and annual precipitation, respectively.

Aims To explore the factors controlling the spatial distribution, as well as the species diversity, of the Vitex negundo var. heterophylla shrublands in North China.
Methods We investigated the species composition and environments for 370 shrubland plots of Vitex negundo var. heterophylla shrublands in North China. We calculated biodiversity indices (Shannon-Wiener index, Simpson index and Pielou’s evenness index) and then applied multivariate regression trees (MRT), analysis of variance (ANOVA), Pearson correlation analysis to disentangle distribution of the Vitex negundo var. heterophylla community and patterns of species diversity along both horizontal and elevational gradients.
Important findings The results showed that Vitex negundo var. heterophylla shrublands distributed in a large area stretching for more than 10° of both latitude and longitude, together with an elevational range of more than 1 000 m (117 m to 1 248 m). The Shannon-Wiener index, Simpson index and Pielou’s evenness index were higher in the herbaceous layer than those in the shrub layers. The species diversity of shrub layer increased with latitude but decreased with elevation. In contrast, that of the herbaceous layer decreased with latitude but increased with elevation. The Shannon-Wiener indexes of both layers were significantly correlated with environmental factors. The results of Pearson correlation analysis indicated that the Shannon-Wiener indexes of shrub layer had a significantly negative relationship with its temperature and slope position, and a significantly positive relationship with its precipitation. However, that of herb layer showed opposite trends.

Aims Armeniaca mandshurica is an important species which serves the need of ornamental, wood and other economical uses. This species has been in wild or semi-wild state for a long time and few studies about this species have been conducted. This paper aimed to provide an important reference for the collection, evaluation and protection of germplasm resources of A. mandshurica.
Methods The status of the germplasm resources in the main distribution area of A. mandshurica was investigated. In total, 47 typical sample trees from Liaoning, Jilin and Heilongjiang Provinces were selected. For each tree, 22 quantitative traits and 7 qualitative traits were measured. The diversity of quantitative traits was represented by indicators such as coefficient of variation, and the diversity of qualitative traits was represented by indicators such as frequency distribution. Trend surface analysis was used to explore the geographical variation in the quantitative traits. A total of 115 pairs of SSR primers were used for PCR amplification for 47 A. mandshurica germplasms, and the genetic diversity of A. mandshurica germplasms was analyzed using genetic similarity coefficient. Germplasms were classified by cluster analysis based on phenotypic traits and SSR markers separately.
Important findings High phenotypic diversity was found among different germplasms in A. mandshurica. The coefficients of variation (CV) of the 19 quantitative traits ranged from 9.40% to 55.98%. Among the 19 traits, twig length had the highest CV and kernel width had the lowest CV. The Shannon-Wiener index of 7 qualitative traits ranged from 0.58 to 1.22. Due to the significant correlation between geographical locations and main climatic factors within the study area, the quantitative traits of A. mandshurica germplasms were closely related to their geographical locations. Among them, twig length increased from east to west, twig thickness and seed mass increased from north to south, and fruit handle length increased from northeast to southwest. Twig length and fruit handle length were positively correlated with altitude, twig thickness was negatively correlated with altitude, and seed mass was not correlated with altitude. Clustering analysis based on 26 phenotypic traits showed that the 47 A. mandshurica germplasms could be divided into 4 categories, which mainly reflected the difference of the germplasm characteristics in A. mandshurica and to some extent also reflected the difference of germplasm productions. Clustering analysis based on genetic similarity coefficients showed that the 47 A. mandshurica germplasms were also divided into 4 categories, which reflected the difference of germplasm productions. Chi-square test showed that the correlation between the two clustering results was not significant, and that the external environment was the key factor affecting phenotypic variations in A. mandshurica.

Aims Solidago canadensis, an invasive herbaceous species, has a strong capacity of potassium enrichment, that may relate to its influence on soil microbial community. Rhizosphere potassium-soluble bacteria can convert mineral potassium into soluble forms being able to be used by plants. It is not known how invasion of S. canadensis may affect diversity and potassium-solubilizing activity of the potassium-solubilizing bacteria. Methods We compared S. canadensis and its coexisting native plant Imperata cylindrica in the reclaimed Hangzhou Bay wetland, Zhejiang Province. We compared the potassium contents of soil and the plant tissues of S. canadensis and Imperata cylindrica which coexists with the invasive species, the effect of potassium supply level on biomass accumulation of plants, and the quantity, diversity and potassium-soluble activity of the rhizosphere potassium-solubilizing bacteria. Important findings The potassium contents in stem and leaf of S. canadensis were significantly higher (1.59 and 7.33 times respectively) than that of I. cylindrica, the contents of available potassium in the 0-10 cm soil layer where the two species grew were significantly different, but not in the 10-20 cm soil layer. Potassium application experiments showed significant biomass increase in both S. canadensis and I. cylindrica, and tissue potassium concentrations as well. Potassium-dissolving medium culture results showed that the number of potassium-‌solubilizing bacteria of S. canadensis rhizosphere was 2.51 times higher than that of I. cylindrica. The strains with potassium-dissolving rings were identified, and the amount of released potassium was determined. Among the 15 strains of potassium-solubilizing bacteria isolated from the rhizosphere soil of S. canadensis, nine efficiently dissolved potassium, and the content of K ⁺ in the treatment solution was 85.11%-192.54% higher than that in the control. Strain H2-20 had the strongest ability with the dissolved K ⁺ of 10.657 mg·L ^-1. The potassium- solubilizing effect of rhizosphere potassium-solubilizing bacteria of S. canadensis was significantly higher than that of I. cylindrica. According to 16S rDNA identification, the 15 strains of bacteria associated with S. canadensis were of 11 genera, and 6 of them had been reported to have the potassium-solubilizing ability. Our results suggest that potassium-solubilizing bacteria in the rhizosphere of S. canadensis is abundant, and may play an important role in potassium enrichment.

Marginal populations are those at the geographical edge of a species’ distribution. Appropriate evaluation of genetic diversity in marginal populations is of crucial significance for understanding the impacts of climate changes on species expansion or contraction in the post Quaternary glaciations, conservation of genetic resources and exploitation, and peripatric speciation. Here, we discuss the evolutionary mechanisms for maintaining genetic diversity in marginal populations, analyze the role of plant mating system in shaping a plant species’ range and the genetic diversity in marginal populations, assess the difference or similarity in genetic diversity between central and marginal populations and the underlying ecological and evolutionary processes, and discuss the species genetic diversity correlation (SGDC) and the theory underlying such correlations. We proposed that future research includes the use of genome-wide sequences or transcriptome data to study the adaptive differential between leading- and rear-edge populations or between central and marginal populations and the molecular mechanisms of the interactions between the genetic diversity in marginal populations and the species diversity in the resident community of a focal species. This may help to understand the adaptability of marginal populations to local habitats and the ecological and evolutionary processes for SGDC at species’ edges.