Maintenance Of Species Diversity Research Articles

Effect of grazing and climatic factors on biodiversity-ecosystem functioning relationships in grassland ecosystems -a case study of typical steppe in Inner Mongolia, China.

Biodiversity underpins grassland ecological functions and productive capacities. By studying the mechanisms for the maintenance of species diversity in animal communities, we can provide important theoretical guidance for the optimization of grazing management and biodiversity protection. The typical grassland of Xilingol in Inner Mongolia, China, was used as the experimental area, and a grazing intensity experiment was set up. This consisted of four gradient levels that were grazed by sheep, which were available for continuous monitoring, namely control standard sheep unit·day·hectare-1·year-1 (CK, 0 SSU·d·hm-2y-1), light grazing (LG, 170 SSU·d·hm-2·y-1), moderate grazing (MG, 340 SSU·d·hm-2·y-1), and high grazing (HG, 510 SSU·d·hm-2·y-1). Nine consecutive years of multi-indicator monitoring of vegetation was carried out from 2014-2022, using monitoring data coupled with time series and inter-annual climatic (relative moisture index, RMI) fluctuations. This was done to analyze the impacts of disturbances, such as grazing use and climatic fluctuations, on the diversity of species and above-ground productivity of the community, thereby exploring the relationship between diversity and productivity, and provide possible explanations for the emergence of a range of ecological responses. The statistical analysis methods used were One-way Analysis of Variance (ANOVA), general linear regression and mixed-effects models. The main conclusions of this study are as follows: (1) The grassland in the experimental area under CK had the highest diversity and productivity and the ecosystem was better able to buffer the negative impacts of climatic drought. Furthermore, the effect of climate on productivity and diversity weakened as the intensity of grazing increased. (2) LG to MG had a constant diversity. (3) Grazing utilization changed the relationship between community species diversity and aboveground productivity by releasing spatial community resources, altering the structure of plant communities, weakening competitive exclusion, and strengthening complementary effects. However, under all of the conditions there is a brief stage in the time series when diversity is stimulated to increase, and the higher the grazing intensity, the earlier this occurs.

Spatial exclusion leads to "tug-of-war" ecological dynamics between competing species within microchannels.

Competition is ubiquitous in microbial communities, shaping both their spatial and temporal structure and composition. Classical minimal models of competition, such as the Moran model, have been employed in ecology and evolutionary biology to understand the role of fixation and invasion in the maintenance of population diversity. Informed by recent experimental studies of cellular competition in confined spaces, we extend the Moran model to incorporate mechanical interactions between cells that divide within the limited space of a one-dimensional open microchannel. The model characterizes the skewed collective growth of the cells dividing within the channel, causing cells to be expelled at the channel ends. The results of this spatial exclusion model differ significantly from those of its classical well-mixed counterpart. The mean time to fixation of a species is greatly accelerated, scaling logarithmically, rather than algebraically, with the system size, and fixation/extinction probability sharply depends on the species' initial fractional abundance. By contrast, successful takeovers by invasive species, whether through mutation or immigration, are substantially less likely than in the Moran model. We also find that the spatial exclusion tends to attenuate the effects of fitness differences on the fixation times and probabilities. We find that these effects arise from the combination of the quasi-neutral "tug-of-war" diffusion dynamics of the inter-species boundary around an unstable equipoise point and the quasi-deterministic avalanche dynamics away from the fixed point. These results, which can be tested in microfluidic monolayer devices, have implications for the maintenance of species diversity in dense bacterial and cellular ecosystems where spatial exclusion is central to the competition, such as in organized biofilms or intestinal crypts.

Species–area relationships of plants and microbes are driven by different mechanisms in patchy grassland fragments

Abstract The island species–area relationship (SAR) describes how the number of species on an island varies with its area and provides important information about the maintenance of species diversity and how species might be lost as habitats are lost and fragmented. While the island SAR has been widely studied among macroorganisms, patterns for soil microbes have been less forthcoming, as have analyses of potential underlying mechanisms. We examined the SAR patterns of plants, soil fungi and bacteria among remnant grassland fragments isolated by degraded habitat matrix in a steppe grassland. As expected, we found that the total species richness of plants, fungi and bacteria in the entire fragment decreased with decreasing fragment area. However, the mechanisms differed among taxa. For plants, the lower diversity was most likely because of decreases in habitat quality and habitat heterogeneity on smaller fragments. For fungi, we found similar results, but also an important interaction with plant diversity, suggesting they were coupled via their functional associations. For bacteria, the lower diversity on smaller fragments primarily resulted from a sampling effect from the larger species pool, which outweighed the effect of higher habitat heterogeneity on smaller fragments. Synthesis: Our study highlights that fragmentation‐induced loss of diversity can have many different underlying mechanisms and that understanding these mechanisms can provide useful insights to project future biodiversity loss and conservation.

Niche differentiation of arthropods and plants along small-scale gradients in temporary wetlands (kettle holes)

Small temporary wetlands, like kettle holes, provide many valuable ecosystem functions and serve as refuge habitats in otherwise monotonous agricultural landscapes. However, the mechanisms that maintain biodiversity in these habitats are still poorly understood. In this study, we investigate how three taxa (vascular plants, ground beetles and spiders) respond to small-scale flooding and disturbance gradients in kettle holes as well as kettle hole area. For this purpose, we determined total, hygrophilic and red list species richness for all taxa and activity density for arthropods along transects extending from the edge towards the center of kettle holes. Furthermore, we calculated the community-weighted mean body size for arthropods and seed mass for plants as surrogates for the ability to respond to disturbance. Our analyses revealed that in particular plants and ground beetles showed strong responses along the small-scale spatial gradient. Total plant species richness decreased towards the center, while hygrophilic plant species increased. In contrast, both total and hygrophilic species richness of ground beetles increased towards the center. Spiders showed similar responses as ground beetles, but less pronounced. We found no evidence that disturbance at the edge of kettle holes leads to smaller body sizes or seed masses. However, arthropods in adjacent arable fields (one meter from the kettle hole edge) were particularly small. Kettle hole area had only weak effects on plants, but not on arthropods. Our study indicates that differences in the depth at the drier edge and the moist, regularly flooded center have a large and taxon-dependent influence on the species composition. Therefore, small-scale heterogeneity seems to be an important predictor for the maintenance of species diversity.

Bird clades with less complex appendicular skeletons tend to have higher species richness

Species richness is strikingly uneven across taxonomic groups at all hierarchical levels, but the reasons for this heterogeneity are poorly understood. It is well established that morphological diversity (disparity) is decoupled from taxonomic diversity, both between clades and across geological time. Morphological complexity has been much less studied, but there is theory linking complexity with differential diversity across groups. Here we devise an index of complexity from the differentiation of the fore and hind limb pairs for a sample of 983 species of extant birds. We test the null hypothesis that this index of morphological complexity is uncorrelated with clade diversity, revealing a significant and negative correlation between the species richness of clades and the mean morphological complexity of those clades. Further, we find that more complex clades tend to occupy a smaller number of dietary and habitat niches, and that this proxy for greater ecological specialisation correlates with lower species richness. Greater morphological complexity in the appendicular skeleton therefore appears to hinder the generation and maintenance of species diversity. This may result from entrenchment into morphologies and ecologies that are less capable of yielding further diversity.

Effects of the Dominate Plant Families on Elevation Gradient Pattern of Community Structure in a Subtropical Forest

Dominant groups and rare groups often coexist in forests. Dominate plant families generally have more species diversity and occupy most of the biomass. However, their effects on community construction and species diversity maintenance remain to be studied. This study aims to investigate this question by using the two dominant plant families in a Chinese subtropical forest (Lauraceae and Fagaceae). In this study, 22 forest dynamic plots were established in the forest distribution area of Daming Mountain Nature Reserve at an elevation of 300–1400 m. We explored the elevational change in the community structure and its relationship with Lauraceae and Fagaceae using generalized additive models (GAM) and a regression analysis. Then we used a correlation analysis to describe the relationship between environmental factors and the community structure. Our results showed the species diversity index showed a hump-shape trend along the elevation, and the total basal area showed no significant change along the elevation. The richness of Lauraceae and Fagaceae showed a positive correlation with the species diversity, but only the richness of Fagaceae showed a positive correlated with the total basal area. Species diversity was positively correlated with soil total nitrogen and soil organic matter. Species diversity and the total basal area were negatively correlated with the soil pH. In summary, Lauraceae and Fagaceae are correlated for community structure, and this correlation is not affected by elevation. Fagaceae has played a more important role than Lauranceae. This study highlights the impact of dominant plant families on the forest community assembly along the elevational transect.

Effects of deterministic assembly of communities caused by global warming on coexistence patterns and ecosystem functions

Seasonal rhythms in biological and ecological dynamics are fundamental in regulating the structuring of microbial communities. Evaluating the seasonal rhythms of microorganisms in response to climate change could provide information on their variability and stability over longer timescales (>20-year). However, information on temporal variability in microorganism responses to medium- and long-term global warming is limited. In this study, we aimed to elucidate the temporal dynamics of microbial communities in response to global warming; to this end, we integrated data on the maintenance of species diversity, community composition, temporal turnover rates (v), and community assembly process in two typical ecosystems (meadows and shrub habitat) on the Qinghai-Tibet Plateau. Our results showed that 21 years of global warming would increase the importance of the deterministic process for microorganisms in both ecosystems across all seasons (R2 of grassland (GL) control: 0.524, R2 of GL warming: 0.467; R2 of shrubland (SL) control: 0.556, R2 of SL warming: 0.543), reducing species diversity and altering community composition. Due to environmental filtration pressure from 21 years of warming, the low turnover rate (v of warming: −3.13/-2.00, v of control: −2.44/−1.48) of soil microorganisms reduces the resistance and resilience of ecological communities, which could lead to higher community similarity and more clustered taxonomic assemblages occurring across years. Changes to temperature might increase selection pressure on specialist taxa, which directly causes dominant species (v of warming: −1.63, v of control: −2.49) primarily comprising these taxa to be more strongly impacted by changing temperature than conditionally (v of warming: −1.47, v of control: −1.75) or always rare taxa (v of warming: −0.57, v of control: −1.33). Evaluation of the seasonal rhythms of microorganisms in response to global warming revealed that the variability and stability of different microbial communities in different habitats had dissimilar biological and ecological performances when challenged with an external disturbance. The balance of competition and cooperation, because of environmental selection, also influenced ecosystem function in complex terrestrial ecosystems. Overall, our study enriches the limited information on the temporal variability in microorganism responses to 21 years of global warming, and provides a scientific basis for evaluating the impact of climate warming on the temporal stability of soil ecosystems.

Analogous assembly mechanisms and functional guilds govern prokaryotic communities in mangrove ecosystems of China and South America.

As an important coastal "blue carbon sink," mangrove ecosystems contain microbial communities with an as-yet-unknown high species diversity. Exploring the assemblage and structure of sediment microbial communities therein can aid in a better understanding of their ecosystem functioning, such as carbon sequestration and other biogeochemical cycles in mangrove wetlands. However, compared to other biomes, the study of mangrove sediment microbiomes is limited, especially in diverse mangrove ecosystems at a large spatial scale, which may harbor microbial communities with distinct compositions and functioning. Here, we analyzed 380 sediment samples from 13 and 8 representative mangrove ecosystems, respectively, in China and South America and compared their microbial features. Although the microbial community compositions exhibited strong distinctions, the community assemblage in the two locations followed analogous patterns: the assemblages of the entire community, abundant taxa, rare taxa, and generalists were predominantly driven by stochastic processes with significant distance-decay patterns, while the assembly of specialists was more likely related to the behaviors of other organisms in or surrounding the mangrove ecosystems. In addition, co-occurrence and topological network analysis of mangrove sediment microbiomes underlined the dominance of sulfate-reducing prokaryotes in both the regions. Moreover, we found that more than 70% of the keystone and hub taxa were sulfate-reducing prokaryotes, implying their important roles in maintaining the linkage and stability of the mangrove sediment microbial communities. This study fills a gap in the large-scale analysis of microbiome features covering distantly located and diverse mangrove ecosystems. Here, we propose a suggestion to the Mangrove Microbiome Initiative that 16S rRNA sequencing protocols should be standardized with a unified primer to facilitate the global-scale analysis of mangrove microbiomes and further comparisons with the reference data sets from other biomes.IMPORTANCEMangrove wetlands are important ecosystems possessing valuable ecological functions for carbon storage, species diversity maintenance, and coastline stabilization. These functions are greatly driven or supported by microorganisms that make essential contributions to biogeochemical cycles in mangrove ecosystems. The mechanisms governing the microbial community assembly, structure, and functions are vital to microbial ecology but remain unclear. Moreover, studying these mechanisms of mangrove microbiomes at a large spatial scale can provide a more comprehensive insight into their universal features and can help untangle microbial interaction patterns and microbiome functions. In this study, we compared the mangrove microbiomes in a large spatial range and found that the assembly patterns and key functional guilds of the Chinese and South American mangrove microbiomes were analogous. The entire communities exhibited significant distance-decay patterns and were strongly governed by stochastic processes, while the assemblage of specialists may be merely associated with the behaviors of the organisms in mangrove ecosystems. Furthermore, our results highlight the dominance of sulfate-reducing prokaryotes in mangrove microbiomes and their key roles in maintaining the stability of community structure and functions.

Sympatric primate seed dispersers and predators jointly contribute to plant diversity in a subtropical forest.

Mutualistic and antagonistic plant-animal interactions differentially contribute to the maintenance of species diversity in ecological communities. Although both seed dispersal and predation by fruit-eating animals are recognized as important drivers of plant population dynamics, the mechanisms underlying how seed dispersers and predators jointly affect plant diversity remain largely unexplored. Based on mediating roles of seed size and species abundance, we investigated the effects of seed dispersal and predation by two sympatric primates (Nomascus concolor and Trachypithecus crepusculus) on local plant recruitment in a subtropical forest of China. Over a 26month period, we confirmed that these primates were functionally distinct: gibbons were legitimate seed dispersers who dispersed seeds of 44 plant species, while langurs were primarily seed predators who destroyed seeds of 48 plant species. Gibbons dispersed medium-seeded species more effectively than small- and large-seeded species, and dispersed more seeds of rare species than common and dominant species. Langurs showed a similar predation rate across different sizes of seeds, but destroyed a large number of seeds from common species. Due to gut passage effects, gibbons significantly shortened the duration of seed germination for 58% of the dispersed species; however, for 54% of species, seed germination rates were reduced significantly. Our study underlined the contrasting contributions of two primate species to local plant recruitment processes. By dispersing rare species and destroying the seeds of common species, both primates might jointly maintain plant species diversity. To maintain healthy ecosystems, the conservation of mammals that play critical functional roles needs to receive further attention.

Fragmentation Analysis of Capisaan Surface Karst Landscape through Changes in Land Use and Land Cover using FRAGSTATS

Changes in land cover mainly brought by humans could alter how landscapes function, which has an impact on the variety and health of the local biota. This study examined the fragmentation shifts of the Capisaan Cave System surface landscape by looking at changes in land use and land cover using Landsat images, ArcGIS and Google Earth imageries to generate classified land covers for the years 2001, 2005, 2010, 2016 and 2019. Fragmentation was analyzed through FRAGSTATS with forest; shrubland and orchard (SO); and agriculture and clearing (AC) as class types. Results showed that the most significant change in the landscape was in the year 2010 with AC significantly increasing its area and aggregation causing other class types to exhibit more fragmentation. Forest and SO covers displayed huge losses indicated by decreased class area and average size of patches accompanied by a more subdivided landscape shown by their increased number of patches. Although forest and SO slightly recovered in the class area in 2016, values were far from recovering to 2001 values. FRAGSTATS data suggest lowering biodiversity values and paying importance to reserve size in the maintenance of species diversity. The edge effect as a result of class and landscape fragmentation in forest vegetation might have been reduced at the landscape level as indicated by the reduced fractal dimension, as well as sustaining patch cohesion and increased clumpiness. However, abatement of edge effect could be easily limited and reversed if the reduction of the total area of forest available in the landscape continues.

The trait‐mediated trade‐off between growth and survival depends on tree sizes and environmental conditions

Abstract Interspecific relationships between growth and survival are critical determinants of tree species diversity maintenance in forests. The trade‐offs between growth and survival in co‐occurring tree species are believed to arise along a continuum of life‐history strategies. For example, co‐occurring species range from those that grow slowly and survive well in resource‐poor environments to those that grow quickly but have low survival rates in resource‐rich environments. However, uncertainties remain regarding how growth–survival trade‐offs are related to species traits, tree sizes or environmental conditions. We examined how the relationships between species traits and growth–survival relationships shift in response to changes in stem sizes and across census periods with different climate conditions (frequency of strong winds, drought intensity) across 45 co‐occurring tree species based on 23 years of growth and survival records in a warm temperate rainforest on Yakushima Island, Japan. We developed hierarchical Bayesian models of relative growth and survival rates, including leaf traits, wood density and 95‐percentile maximum stem diameter as explanatory variables. We tested the relationships between estimated trait‐mediated growth–survival relationships and the indices of climate events during five census periods. Each trait's effects on growth–survival relationships differed across the five census periods in response to climate conditions. Interspecific growth–survival relationships affected by a single trait axis for leaves or wood tended to be negative. In contrast, those affected by the maximum stem diameter tended to be positive. Such trends increased with more frequent strong winds or more intense droughts. The single‐trait effects on growth–survival relationships were stronger for smaller sizes than for larger sizes. For all traits combined, we found a significant growth–survival trade‐off only for small‐sized stems in three of five census periods. Synthesis. Our results indicate that the effect of species traits on the growth–survival relationships depended on tree sizes, the census periods or both in response to the frequency or intensity of climate events. We argue the importance of incorporating spatial and temporal variations in environmental conditions into long‐term data from tree census to predict forest dynamics.

Notes on an interspecific interaction between distant taxa: Observation of active cohabitation and communal nesting resources between Gehyra mutilata (Wiegmann, 1834) and two vespid wasp species

AbstractTropical ecosystems are biodiverse and ecologically complex, supporting nearly half of the global herpetofauna. Ecological interactions play a role in the maintenance of species diversity with a range of ecological interactions occurring within and among species in tropical ecosystems. Incidental observations of ecological interactions provide an important contribution to the understanding of the ecology and natural history of species. Here, we report an interspecific interaction between distant taxa, the Four‐Clawed Gecko (Gehyra mutilata) utilizing an active communal nesting site and shared nesting resources with two vespid wasp species (Eumeninae and Polistinae), where previous observations documented species utilizing abandoned nesting resources. This is the first known record of three species actively cohabitating in a shared nesting resource. This observation, with one or all species positively benefiting from the ecological interaction, likely indicates a mutualistic or commensal ecological interaction. Incidental observations such as the present study are likely to reveal that interspecific ecological interactions including communal nesting are more widespread than previously thought and the co‐utilization of existing nesting resources presents an advantage for taxa. Observations such as these provide the basis for understanding the complex network of ecological interactions occurring in tropical rainforests.

Initial herbivory and exposure to herbivory-induced volatiles enhance arthropod species richness by diversifying community assemblages

Plant ecological traits affect the species identity of plant-colonizing arthropods, which in turn induces species-specific trait changes in plants, forming feedback between plants and arthropods. Such feedback can amplify initial differences in species composition, leading to large variations (i.e., high β diversity). We hypothesized that the differences in plant initial conditions have sustained effects on arthropod community composition and species richness. To test this hypothesis, we monitored arthropod community assembly on a willow tree species, Salix eriocarpa, which was experimentally manipulated into three initial treatments: undamaged (in chamber 1); damaged by the specialist leaf beetle, Plagiodera versicolora (chamber 2); and “exposed” plants that were undamaged but were exposed to volatiles from damaged plants (in chamber 2). The arrival and population dynamics of the leaf beetle were affected by the plant’s initial condition (chamber 1 vs. 2), which could result from the microscale environmental heterogeneity between chambers (chamber effect) and/or from the herbivory-related impacts (direct herbivory and exposure to induced volatiles in chamber 2). The community composition on damaged and exposed plants became significantly different on day 32. In addition, the divergence in composition between plant individuals was significantly smaller in undamaged plants (chamber 1) than in damaged and exposed plants (chamber 2) on day 60. The compositional variations (β diversity) between chambers, between treatments, and between days, comprised a large proportion (two third) of the total species richness (γ diversity) in the whole community of arthropods. These results suggest that plant initial condition is a key driver of community assembly and the maintenance of species diversity.

长白山暗针叶林群落物种多样性维持机制

PDF HTML阅读 XML下载 导出引用 引用提醒 长白山暗针叶林群落物种多样性维持机制 DOI: 10.5846/stxb202202210407 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（32001312） Species diversity maintenance mechanism of dark coniferous forests community in Changbai Mountain Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:植物群落物种多样性维持机制一直是生态学研究的热点话题，其中生态位理论和中性理论是被普遍接受的两种理论观点，但是目前关于生态位理论和中性理论在群落物种多样性维持中的相对重要性还没有统一定论。基于长白山暗针叶林群落数据，采用单物种-面积关系模型探究特定树种对邻域物种丰富度的影响，并借助同质性和异质性泊松零模型检验其显著性。（1）群落水平上，在3-15 m空间尺度上，促进种占据优势地位，在>15 m空间尺度上，中性种逐渐取代促进种起主导作用，抑制种比例较低，并且随着空间尺度变化幅度不大。（2）物种水平上，采用同质性泊松零模型检验树种对邻域物种丰富度的影响，臭冷杉、花楷槭、青楷槭在0-20 m空间尺度上对邻域物种丰富度增加起促进作用，黄花落叶松、鱼鳞云杉在0-20 m空间尺度上抑制了邻域物种丰富度增加。花楸树、黑桦和硕桦在全部研究尺度上表现为中性种，髭脉槭、大青杨、红松等在不同研究尺度上表现为不同的作用效果。剔除了生境过滤作用的异质性泊松零模型检验结果与同质性泊松零模型结果差异不显著，表明研究样地内生境过滤作用对多样性格局形成影响不大，各树种间的相互作用对群落物种组成影响较大，进一步证明了生态位理论能够解释长白山暗针叶林物种多样性维持。 Abstract:The maintenance mechanism of plant community species diversity has always been a hot topic in ecological research. Niche theory and neutral theory are two widely accepted theoretical viewpoints, but the relative importance of niche theory and neutral theory in the maintenance of community species diversity has not been unified. Based on the data of dark coniferous forest community in Changbai Mountain, this study used the individual species-area relationship model (ISAR) to explore the impacts of specific tree species on neighborhood species richness, and used homogeneity and heterogeneity Poisson zero model to test its significance. The results showed that:(1) at the community level, in the 3-15 m spatial scale, the promoting species occupied the dominant position. At scale >15 m, the neutral species gradually replaced the accumulators, the proportion of repellers species was low, and the change range with the spatial scale was small. (2) At the species level, the homogeneity Poisson zero model was used to test the influence of tree species on the neighborhood species richness. At the spatial scale of 0-20 m, Abies nephrolepis, Acer ukurunduense and Acer tegmentosum promoted the increase of species richness in the neighborhood, while Larix olgensis and Picea jezoensis inhibited the increase of neighborhood species richness. Sorbus pohuashanensis, Betula dahurica and Betula costata were neutral species at the scale of 0-20 m. Acer barbinerve, Populus cathayana, and Pinus koraiensis showed different effects on different scales. There was no significant difference between the results of heterogeneity Poisson null model excluding habitat filtering and homogeneous Poisson null model, indicating that habitat filtering had little effect on the formation of diversity pattern in the study plot. It was mainly due to the interaction between tree species contributed to the species composition structure of the community, which further proved that niche theory could explain the maintenance of species diversity in dark coniferous forest of Changbai Mountain. 参考文献 相似文献 引证文献

Some of the Mechanisms for Coexistence of Tree Species Diversity in Tropical Forests: A Review of Effects of Tree Density Dependence

Tree communities contribute to maintenance of species diversity in tropical forests. Coexistence of many tree species is not without competition. Therefore, coexistence of tree species and size diversities occur sequentially or simultaneously in tropical natural forests. Understanding coexistence and competition mechanisms of tree species requires knowledge of interactions within and between species. However, many conservation efforts and strategies failed due to inability to identify and maintain functional coexistence mechanisms among tree species in the forest. Also, most trees died because of pressure on their habitats and not because of limiting growth resources. Hence, species identity, minimum distance and size of the neighbouring trees which are responsible for coexistence of competing trees in most tropical forests have not been explicitly reviewed. Therefore, this review evaluated some of the density dependent mechanisms for coexistence of tree species alpha diversity in tropical forests. Many interactive mechanisms are responsible for coexistence tree species in tropical forests. Inter- and intra-specific competitions are the most significant and both facilitate positive and negative density dependence. Therefore, switching from negative to positive density dependence may occur in some situations. Positive and negative density effects regulate species abundance and coexistence through conspecific and heterospecific structures. Aggregates of conspecific and heterospecific neighbours constitute forest spatial structure. Negative density interactions are mutually exclusive and basically ranged from effect of species identity of neighbours, distance to neighbours and tree size of the neighbours to reference trees in the community structures. Some mechanisms shorten distances for heterospecific than conspecific interactions. Conspecific structures improved survival and growth of rare tree species. Interactive mechanisms in tree community and population structures facilitate species diversity and size inequality, respectively.

Progress and Prospects of the Natural Restoration of Damaged Vegetation after the Earthquake

Vegetation plays an important role in soil and water conservation, water conservation and carbon sequestration of an ecosystem. The restoration of damaged vegetation is of great significance to the maintenance of species diversity and the restoration of the regional ecological environment. It is also one of the most effective measures to improve the fragile ecosystem. This paper summarizes the research results from decades of damaged vegetation recovery in the process of vegetation recovery, the main driving factor and the restoration mode.

Drivers of species-specific contributions to the total live aboveground plant biomass in Central European semi-natural hay grasslands

Semi-natural grasslands are known to provide numerous ecosystem services, of which one of the most important is production of biomass. However, the contribution of individual plant species to the total biomass is much less well understood. This study addressed questions concerning community structure and responses of species-specific biomass (s-AGB) to gradients in soil acidity and fertility, topographical and climatic features, and disturbance regimes in mown and abandoned grasslands in the Sudetes Mountains (Central Europe). It identified pH as the most significant environmental gradient affecting turnover in s-AGB, and mowing cessation, temperature, and precipitation also had significant effects. Further, it showed high inequality in biomass among co-occurring plant species. It also showed that biomass inequality (measured by the Gini coefficient) among interacting species decreases with increasing functional diversity (Rao’s index). This study highlights that common plant species (in terms of frequency) play a major role in contributing to the total aboveground biomass (t-AGB). However, less frequent species are also significant contributors to the t-AGB. Thus, the combined contribution of infrequent species to the t-AGB should not be neglected. Our findings support the mass ratio hypothesis stating that ecosystem functions such as biomass production depend on dominant species. On the other hand, high niche differentiation ensures the coexistence of less competitive species with the dominants by the variety and complementarity of functional traits. Infrequent and non-dominant species were the core of the diversity seen in the studied grasslands. The maintenance of species diversity in grasslands should be prioritized in nature conservation policies to ensure the sustainability of ecosystem services.

Effects of Land Use Changes on the Plant Community Characteristics in the Wetlands of the Semi-Arid Regions

Human disturbance is the main driving factor of wetland vegetation degradation, and plant community changes can directly characterize the process of wetland degradation. The wetlands in semi-arid region of Songnen Plain perform the important ecological functions, especially the habitat of waterbirds. Recently, the succession of wetland plant community has been accelerated by land use changes. In this study, we investigated the variations of plant community in wetlands undergoing land use changes (natural, mowing, light grazing + mowing, moderate grazing and heavy grazing wetlands) in the western Songnen Plain. The results showed that the plant communities were significantly affected by land use changes. The typical wetland plant Calamagrostis angustifolia was the dominant species in natural wetlands, and its dominance was gradually decreased in mowing or grazing wetlands in where Carex spp. or Artemisia selengensis acting as the dominant species. The height, density, and biomass in natural wetlands were significantly higher than those in other wetlands, whereas the species diversity and richness in natural wetlands were significantly lower. The similarity index of plant community in wetlands undergoing land use changes to natural wetlands ranged from 17.7–45.1%, being the highest in mowed wetlands and the lowest in heavily grazed wetlands. The linear regression further indicated that the plant diversity index was negatively correlated with the aboveground biomass of grasses and positively correlated with the aboveground biomass of forbs. Therefore, the land use changes in wetlands drove the replacement of dominant species of wetland vegetation and changed plant community characteristics and the species diversity, and the maintenance of species diversity is linked with the variability in plant functional strategies. The results of community variations and their relationships with functional changes can be used for assessing the effects of degradation and ecological function in response of land use changes in wetlands.

Mechanisms of Seed-To-Seed Interactions between Dominant Species in the Yangtze River Estuary under Saline Condition

Plant community assembly is the central issue in community ecology. As plant traits differ in different life history stages, the form, intensity and mechanism of interspecific interactions may change with the ontogenetic process of plants. However, our understanding of interspecific interaction mechanisms during germination is still limited. Here, we conducted a laboratory germination experiment using five dominant species in Chongming Dongtan (Spartina alterniflora, Scirpus mariqueter, Phragmites australis, Suaeda glauca and Tripolium vulgare) to assess their germination performance in control (monoculture), allelopathy and mixture treatments. The results indicated that seeds could affect germination performance of neighbors through both allelopathy and salinity modification. Salinity of the solution in Petri dishes after seed germination decreased significantly in most species combinations in competition treatment, and was negatively correlated with the number of total germinated seeds. Seed leachate of invasive Spartina alterniflora significantly accelerated the germination of two native halophytes Suaeda glauca and Tripolium vulgare, but not Scirpus mariqueter and Phragmites australis. The salt absorption by Spartina alterniflora seeds had inconsistent effects compared with that of its seed leachate. On the other hand, seed leachate of native Scirpus mariqueter and Phragmites australis significantly slowed down the germination of invasive Spartina alterniflora. The effect of salinity modification of Scirpus mariqueter on Spartina alterniflora was positive, whereas that of other species was neutral. Considering seed-to-seed interactions is an important perspective to understand the underlying mechanisms of community dynamics, species diversity maintenance and invasion of alien species, and can improve the effectiveness in the management of invaded coastal wetlands.

Soil fungal communities show more specificity than bacteria for plant species composition in a temperate forest in China

BackgroundSoil microbiome is an important part of the forest ecosystem and participates in forest ecological restoration and reconstruction. Niche differentiation with respect to resources is a prominent hypothesis to account for the maintenance of species diversity in forest ecosystems. Resource-based niche differentiation has driven ecological specialization. Plants influence soil microbial diversity and distribution by affecting the soil environment. However, with the change in plant population type, whether the distribution of soil microbes is random or follows an ecologically specialized manner remains to be further studied. We characterized the soil microbiome (bacteria and fungi) in different plant populations to assess the effects of phytophysiognomy on the distribution patterns of soil microbial communities in a temperate forest in China.ResultsOur results showed that the distribution of most soil microbes in different types of plant populations is not random but specialized in these temperate forests. The distribution patterns of bacteria and fungi were related to the composition of plant communities. Fungal species (32%) showed higher specialization than bacterial species (15%) for different types of plant populations. Light was the main driving factor of the fungal community, and soil physicochemical factors were the main driving factor of the bacterial community.ConclusionThese findings suggest that ecological specialization is important in maintaining local diversity in soil microbial communities in this forest. Fungi are more specialized than bacteria in the face of changes in plant population types. Changes in plant community composition could have important effects on soil microbial communities by potentially influencing the stability and stress resistance of forest ecosystems.