Stability Of Plant Communities Research Articles

Influence of palm trees on the richness and distribution of plant species on the murundus at a Caatinga/Cerrado ecotone

Abstract Understand the role of the drivers in vegetation pattern is essential in ecology since diversity plays a major role in the stability and maintenance of plant communities. The murundus are small and scattered earthmounds with a differentiated flora of its surrounding. In our study site (Campo Maior, Piauí, Northeastern Brazil), we classified them in three categories: presence of carnaúba (PC), presence of tucum (PT), and with the absence of palm trees (AP). Here, our goals were (1) to explore alpha diversity using the richness estimator and abundance distribution rank, expecting that palm trees could influence the richness of plant species on murundus; (2) analyzing the species richness-area relationship in the murundus, following the assumptions that the largest one holds more species; (3) find the changes in the species composition (beta diversity) between the three categories of murundus, assuming which the presence of palm trees influence the species composition; and (4) investigate if the distance between murundus is a decisive factor in the species composition, where the closest murundus are the most similar in species composition. Ours results showed that palms trees do not influence the richness of the murundus, the largest murundus are the richest ones, and the turnover predominantly determines beta diversity in the different murundus categories. Furthermore, the distance between the murundus did not determine its floristic similarity. Overall, we demonstrated which the species of palm trees are not the main drive of the plant assemblage in the murundus, however its size comprises a major factor in the richness, with great species substitution, which explains the high plant diversity.

三峡水库涪陵-奉节段消落带优势草本植物生态位与种间联结性研究

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡水库涪陵-奉节段消落带优势草本植物生态位与种间联结性研究 DOI: 10.5846/stxb202011162953 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学青年基金面上项目（31270451）；三峡库区水环境演变与污染防治重点实验室开放基金项目（WETKL2012MS-07）；国家自然科学青年基金（41902024）；重庆市科委面上项目（cstc2019jcyj-msxmX0656） Niche and interspecific association of dominant herbaceous plants in the water-level-fluctuating zone of Fuling-Fengjie section of the Three Gorges Reservoir Author: Affiliation: Fund Project: 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:参照相邻格子法对三峡水库中段（重庆市涪陵-奉节段消落带）地上植被进行调查，并运用生态位宽度、生态位重叠度、χ2检验等手段对优势草本植物生态位与种间联结性进行分析，能在一定程度上揭示三峡水库消落带优势草本植物的生态学特性、进而推测植被群落的演替趋势，以期为三峡水库消落带植被生态修复提供理论基础或参考建议。结果表明：（1）本次调查发现共有优势植物57种、隶属22科44属，其中狗牙根的生态位宽度最大、占绝对竞争优势。（2）在105个种对中，生态位相似比（Cih）≥0.50的种对有4个，生态位重叠值（Lih）≥0.50的种对有7个，种间相似性较小、竞争关系较弱。（3）χ2检验结果显示，优势植物种间正负联结比为1.33，正联结优势不明显；而Pearson与Spearman秩相关检验结果显示，种间正负联结比分别为0.54、0.75，负联结占优势。三种检验方式均表明，优势植物种间联结性较弱、稳定性相对较差、独立性相对较强。（4）种间联结系数（AC）≥0.60的种对数为7种，共同出现百分率（PC）≥0.7的种对数仅为1种。种间总体正联结性不强，物种趋于独立分布。（5）种间Pearson、Spearman秩相关检验与相应的Cih和Lih之间均呈显著正相关，表明种间正（负）关联越强、Cih和Lih越大（小）。（6）本文研究结果在一定程度上反映了三峡水库消落带植被退化生态系统现状，为最大程度提高消落带植物群落结构稳定性和物种多样性，针对小流域植被恢复与重建有如下参考建议：在整体上，可以采用以狗牙根（Cynodon dactylon（Linn.） Pers）、苍耳（Xanthium sibiricum）、鬼针草（Bidens pilosa L.）等为先锋植物，以狗尾草（Setaria viridis）、稗（Echinochloa crusgalli）、牛鞭草（Hemarthria altissima）等为伴生种的群落配置模式进行宏观布局；在局部上，可以采用稗（Echinochloa crusgalli）+苘麻（Abutilon theophrasti Medicus）、狗尾草（Setaria viridis）+黄花草木樨（Melilotus officinalis L.）、马唐（Digitaria sanguinalis）+水蓼（Polygonum hydropiper L.）等种对配置模式进行实地配置。 Abstract:This article refers to the adjacent grid method to investigate the aboveground vegetation in the middle section of the Three Gorges Reservoir (Fuling-Fengjie section of Chongqing City). We use niche width, niche overlap, χ2 test and other methods to compare the niche of dominant herbaceous plants, which could reveal the ecological characteristics of dominant herbaceous plants in the Three Gorges Reservoir water level fluctuating zone to a certain extent. Then, we infer the succession trend of plant community, so as to provide theoretical basis or reference suggestions for the ecological restoration of vegetation in the Three Gorges Reservoir water level fluctuating zone. The results showed that:(1) There were 57 plant species belonging to 22 families and 44 genera. The niche breadth of bermudagrass was the largest and occupied the absolute competitive advantage. (2) Among the 105 dominant plant species pairs studied, there were 4 species pairs with niche similarity ratio (Cih) ≥ 0.50 and 7 species pairs with niche overlap value (Lih) ≥ 0.50, indicating that the similarity between species was small and the competition was weak. (3) χ2 test results showed that the positive and negative association ratio of dominant plants was 1.33, indicating that the positive association advantage was not obvious. Pearson and Spearman rank correlation test showed that the positive and negative association ratio was 0.54 and 0.75, respectively, indicating that negative association was dominant. All the three tests showed that the interspecific association of dominant plants was weak, the stability was relatively poor and the independence was relatively strong. (4) The number of species with interspecific association coefficient (AC) ≥ 0.60 was 7 and the number of species with cooccurrence percentage (PC) ≥ 0.7 was only 1, indicating that the positive association between species was not strong and species tended to be independent. (5) Pearson and Spearman rank correlation tests showed a significantly positive correlation with Cih and Lih between species, indicating that the stronger the positive (negative) correlation, the greater the Cih and Lih. (6) In order to maximize the structural stability and species diversity of plant community in the Three Gorges Reservoir water-level-fluctuating zone, the following suggestions were put forward for vegetation restoration and reconstruction in small watershed:on the whole, a community configuration mode with Bermudagrass, Cocklebur, Bidens, etc. as the dominant plants, and Setaria, Barnyardgrass, and Virginia etc. as the companion species could be used for macro layout. In the local, the configuration mode of Echinochloa crusgalli+Abutilon bicolor, Setaria setifolia+Melilotus lutea, Digitaria tangutorum+Polygonum hydropiper etc. could be used for field configuration. 参考文献 相似文献 引证文献

Synanthropization and species diversityof floodplain ecosystems of the Ob-Irtysh basin, Russia

Currently, the phytocenoses of the Irtysh floodplain are experiencing intense anthropogenic pressures due to the intensive development of the oil and gas industry, as well as the urbanization of the territory. This paper focuses on the structure and species composition of the 27 studied areas in the floodplain ecosystems of the Ob-Irtysh basin. As a result of the research, we found 111 species of vascular plants from 33 families in plant communities. The areas belong to meadows and forest vegetation are represented by (1) birch forests (33%), (2) pine forests (10%), (3) fir forests (8%), (4) aspen forests (4%) and (5) associations of meadows (45%). Furthermore, we conducted a comparative analysis of the studied phytocenoses according to the Drude scale. To determine the anthropogenic transformation of the flora and individual plant communities, we determined the synanthropization index (the ratio of synanthropic species to the total number of species). In the synanthropic flora fraction, we distinguished 45 species belonging to 12 families, with the most multispecies being Apiaceae, Scrophulariaceae, Compositeae, Ranunculaceae, Poaceae, Fabaceae, Plantaginaceae. The synanthropization index of the studied phytocenoses ranges from 6.6% to 81.2%. The largest number of synanthropic species occurs in meadow associations, the content of synanthropes is greater than 50%, the structure is becoming more superficial, and the productivity and stability of plant communities are changing. The study of the horizontal structure of grass stands of meadow phytocenoses makes it possible to find the variability of different years, the change of dominant species and the stability of the species composition. Currently, researchers are paying considerable attention to the analysis of the structure of the herbage, since its study is of great theoretical and practical importance in clarifying phytocenotic relations.

Relationship between Tree Richness and Temporary Stability of Plant Communities: A Case Study of a Forest in Northeast China

The relationship between diversity and stability is a classic issue in ecology, but no general consensus has been achieved. To address this relationship, a field survey of a forest in Northeast China was conducted. The temporary stability was defined from the perspective of community characteristics. The results showed that communities with the highest temporary stability value were characterized by a single dominant species. A significant linear relationship with a low R2 value was observed between temporary stability and tree richness. When dominant and non-dominant tree species were studied, no significant linear relationship was obtained between temporary stability and non-dominant tree richness. However, the relationship between temporary stability and dominant tree richness was significant with a high R2 value, and the temporary stability decreased with increasing dominant tree richness. This study demonstrates that dominant tree richness is closely related to temporary stability, and temporary stability can serve as a stability indicator. The results provide a new perspective for understanding stability and additional information for revealing the relationship between diversity and stability in forest ecosystems.

Southern Baffin Island mean annual precipitation isotopes modulated by summer and autumn moisture source changes during the past 5800 years

ABSTRACTPaleo water isotope records can elucidate how the Arctic water cycle responded to past climate changes. We analyze the hydrogen isotope composition (δ2H) of plant‐derived n‐alkanoic acids (waxes) from Lake Qaupat, Baffin Island, Nunavut, Canada, to assess moisture sources and seasonality during the past 5.8 ka. We compare this record to a sedimentary ancient DNA (sedaDNA)‐inferred vascular plant record from the same lake, aiming to overcome the uncertainty of plant community impacts on leaf waxes. As the sedaDNA record reveals a stable plant community after the colonization of Betula sp. at 6.1 ka, we interpret plant wax δ2H values to reflect climate, specifically mean annual precipitation δ2H. However, the distributions of n‐alkanoic acid homologs suggest that aquatic mosses, which are not represented in the sedaDNA record, may become more abundant towards the present. Therefore, we cannot exclude the possibility that changes in the plant community cause changes in the plant wax δ2H record, particularly long‐chain waxes, which become less abundant through this record. We find that Lake Qaupat mid‐chain plant wax δ2H is enriched coincident with high Labrador Sea summer surface temperature, which suggests that local moisture sources in summer and early autumn have the greatest impact on precipitation isotopes in this region.

Plant litter influences the temporal stability of plant community biomass in an alpine meadow by altering the stability and asynchrony of plant functional groups

Abstract The stability of a plant community is defined as its ability to resist and be resilient to changes. Plant community stability can be driven by a range of external perturbations as well as by plant community traits. Plant litter traits (species or mass) are widely recognized drivers for plant community composition and diversity changes in grasslands. Yet, the effects of litter traits on the temporal stability of plant communities in natural grasslands are largely unknown. In this study, a field experiment was conducted at an alpine meadow on the Qinghai Tibetan Plateau to quantify the effects of litter from Elymus nutans, Kobresia setchwanensis and Ligularia virgaurea on the temporal stability of plant community biomass at five different mass levels (0, 100, 200, 400 and 600 g/m2). The experiment was conducted over the period from the pre‐growth to peak‐growth stage between 2017 and 2019, during which temporal stability of plant community biomass was assessed in relation to plant community characteristics. The effects of litter on temporal stability of plant community biomass were mainly driven by the litter mass rather than the litter species. A hump‐shaped relationship between litter mass and temporal stability of plant community biomass was found, with the highest stability under intermediate litter mass treatment (200 g/m2). A structural equation model identified that this response was driven by the indirect effects of litter mass on the temporal stability of the biomass of the dominant (forbs) and subdominant (grasses) functional groups in the community and the asynchrony of plant functional groups. The results of this study demonstrate that plant litter traits are important drivers for maintaining plant community stability in natural grasslands, highlighting the importance of grassland management decisions (e.g. grazing intensity) relating to the quantity and quality of litter accumulation. A free Plain Language Summary can be found within the Supporting Information of this article.

Reducing plant community variability and improving resilience for sustainable restoration of temperate grassland

Grassland ecosystem is important for the realization of the global sustainable development goals (e.g. Goal 15) since it provides irreplaceable services for human beings, supporting human health and sustainable development. Most studies have focused on improving grassland restoration techniques, but less attention has been paid to grassland ecosystem stability in succession. Plant community stability of temperate grassland in arid and semi-arid regions is analyzed through 38 sampling sites in Inner Mongolia, China. The degradation succession sequence of grassland is established by principal component analysis, and the species diversity and functional diversity along degradation gradient analyzed by multivariate statistical analysis. The results show that (1) functional diversity has higher explanatory power for community stability than species diversity due to the functional dispersion of plant traits; (2) climate factors rather than grazing or soil control plant community diversity and stability at regional scale; (3) the resistance of plant community does not change in degradation succession, but the trade-off effect of stability components in different plant communities differ, such as the order of trade-off effects (e.g. community resilience (ET)＞community resistance (RT)＞structural variability (St)＞functional variability (Fu) in the community dominated by Stipa grandis, RT＞ET＞St＞Fu in Leymus chinensis community, St＞ET＞Fu＞RT in Stipa capillata community, RT＞St＞Fu＞ET in Artemisia frigida community, St＞Fu＞ET＞RT in Cleistogenes squarrosa community, and Fu＞St＞RT＞ET in Artemisia halodendron community); (4) grassland ecosystem with higher diversity shows greater resilience and lower variability than those with single species, which supports the established diversity hypothesis. Furthermore, sustainable grassland restoration should reduce community variability and improve resilience. These findings highlight the response of diversity to stability in temperate grassland and provide scientific support for grassland ecosystem protection and restoration.

Dormant-Season Moderate Grazing Prefire Maintains Diversity and Reduces Exotic Annual Grass Response Postfire in Imperiled Artemisia Steppe

Grazing and fire are both independently important drivers of plant community dynamics; however, their interactive effects may be even more influential. Little is known about prefire grazing effects on postfire plant community dynamics. We investigated the effects of dormant-season, moderate prefire grazing by cattle on postfire plant community response in the imperiled Artemisia (sagebrush) steppe. Treatments were moderately grazed or not grazed by cattle for 5 yr before fire. The first yr post fire, shrub density was 4 × greater in grazed areas, demonstrating fire-induced mortality was reduced with grazing. This further suggested that grazing reduced fire severity and postfire large bunchgrass biomass was greater in grazed compared with ungrazed areas. Biomass and abundance of the exotic annual grass, Bromus tectorum L., were substantially greater and plant diversity was lower in ungrazed compared with grazed areas post fire. Five years post fire, perennial herbaceous vegetation still dominated prefire-grazed areas, but ungrazed areas were dominated by B. tectorum, suggesting that a novel ecosystem state had developed. Substantial increases in B. tectorum are concerning because it prevents recruitment of native perennial plants and increases fire frequency, which would further decrease diversity and reinforce an exotic annual-dominated state. Lower diversity in ungrazed areas post fire is concerning because diversity can be important for plant community stability. The importance of livestock as ecological engineers through their influence on fire has largely been overlooked but is clearly substantial and needs to be integrated into conservation and management plans.

Population dynamics of Agriophyllum squarrosum along an ecosystem restoration chronosequence in the Tengger Desert, China: Indication implications for desertification combating

Agriophyllum squarrosum, an annual native herb pioneer species, is associated with shifting sand dunes along the southern edge of the Tengger Desert, China. Its population dynamics shift with the restoration of sandy desert ecosystems after shrub planting. A chronosequence of four sites was evaluated on the southern edge of the Tengger Desert: an untreated shifting sand dune, and three formerly shifting sand dunes planted with shrubs 5, 15, and 25 years previously. Five years after planting, density of A. squarrosum was unchanged but the relative cover was only 6.0% of that found on the shifting dune. After 15 years, density and cover were less than 1% of the shifting dune. After 25 years, A. squarrosum had completely disappeared. During the 25 years of plant community development, the factors associated with the A. squarrosum decline included a decrease in the seed bank, improvement in the topsoil, biological crust formation, and photoinhibition of seed germination. A. squarrosum declines as more stable plant community recover and this population decline tracks the improvements in site quality and can be regarded as an indicator of desertification reversion

Non-utilization Is Not the Best Way to Manage Lowland Meadows in Hulun Buir.

Carex meyeriana lowland meadow is an important component of natural grasslands in Hulun Buir. However, in Hulun Buir, fewer studies have been conducted on C. meyeriana lowland meadows than on other grassland types. To determine the most appropriate utilization mode for C. meyeriana lowland meadows, an experiment was conducted in Zhalantun city, Hulun Buir. Unused, moderately grazed, heavily grazed and mowed meadow sites were selected as the research objects. The analysis of experimental data from 4 consecutive years showed that relative to the other utilization modes, mowing and moderate grazing significantly increased C. meyeriana biomass. Compared with non-utilization, the other three utilization modes resulted in a higher plant diversity, and the moderately grazed meadow had the highest plant community stability. Moreover, principal component analysis (PCA) showed that among the meadow sites, the mowed meadow had the most stable plant community and soil physicochemical properties. Structural equation modeling (SEM) showed that grazing pressure was less than 0.25 hm2/sheep unit and that plant biomass in C. meyeriana lowland meadow increases with increasing grazing intensity, temperature and precipitation.

The Role of Canopy Cover Dynamics over a Decade of Changes in the Understory of an Atlantic Beech-Oak Forest

The understory of temperate forests harbour most of the plant species diversity present in these ecosystems. The maintenance of this diversity is strongly dependent on canopy gap formation, a disturbance naturally happening in non-managed forests, which promotes spatiotemporal heterogeneity in understory conditions. This, in turn, favours regeneration dynamics, functioning and structural complexity by allowing changes in light, moisture and nutrient availability. Our aim is to study how gap dynamics influence the stability of understory plant communities over a decade, particularly in their structure and function. The study was carried out in 102 permanent plots (sampled in 2006 and revisited in 2016) distributed throughout a 132 ha basin located in a non-managed temperate beech-oak forest (Bertiz Natural Park, Spain). We related changes in the taxonomical and functional composition and diversity of the understory vegetation to changes in canopy coverage. We found that gap dynamics influenced the species composition and richness of the understory through changes in light availability and leaf litter cover. Species with different strategies related to shade tolerance and dispersion established in the understory following the temporal evolution of gaps. However, changes in understory species composition in response to canopy dynamics occur at a slow speed in old-growth temperate forests, needing more than a decade to really be significant. The presence of gaps persisting more than ten years is essential for maintaining the heterogeneity and stability of understory vegetation in old-growth temperate forests.

Asynchrony Drives Plant and Animal Community Stability in Mediterranean Coastal Dunes

Substantial evidence now suggests that a positive diversity–stability relationship exists. Yet few studies examine the facets of biodiversity that contribute to this relationship, and empirical research is predominantly conducted on grassland communities under controlled conditions. We investigate the roles of species richness, environmental condition (vegetation cover), asynchrony, and weighted population stability in driving community stability across multiple taxa. We used data from a Long-term Ecological Research project to investigate temporal stability of annual plants, beetles, reptiles, and rodents in Nizzanim Coastal Sand Dune Nature Reserve in Israel. All four taxa had a strong positive relationship between asynchrony and community stability. Only rodents showed a positive richness–stability relationship. Perennial plant cover had a significant relationship with community stability for three taxa, but the direction of the correlation varied. Asynchrony had a stronger relationship with perennial plant cover than it did with richness for both plants and beetles. We suggest that community stability is driven by asynchrony for flora as well as fauna. Stability appears to be determined by species’ interactions and their responses to the environment, and not always by diversity. This has important consequences for understanding the effects of environmental degradation on ecosystem stability and productivity, which have destabilizing consequences beyond biodiversity loss.

Climate warming-induced drought constrains vegetation productivity by weakening the temporal stability of the plant community in an arid grassland ecosystem

An investigation of the influences of climatic warming on ecosystem function and stability is crucial to project the impact of global climate change on terrestrial ecosystems. However, few studies have applied multiple warming treatments in arid ecosystems, which play a critical role in the global carbon cycle and are among the ecosystems most sensitive to future climatic change. To explore the effects of climatic warming on plant community function and stability, moderate warming and acute warming treatments were conducted in desert grassland, Inner Mongolia, China, using free-air temperature increase facilities. Aboveground net primary production (ANPP) of plant community significantly decreased with climatic warming, particularly in warmer years with drier conditions. The decrease in ANPP was mainly caused by decreased soil moisture induced by climatic warming. Climatic warming reduced the temporal stability of the plant community by weakening plant species asynchrony and shifting key functional groups, such as perennial vs annual grass and C3 vs C4 species. Our findings indicate that climatic warming could hamper plant community productivity via decreased soil moisture and constrain plant community functioning by weakening community stability. This result highlights that shifts in plant community composition and consequent functional changes can play a key role in predicting the responses of arid ecosystems to climatic change.

Variations and factors characterizing ecological niches of species in a stable grassland plant community

To explore the primary factors affecting the ecological niches in a plant community, four dominant shrub species (Sophora viciifolia, Periploca sepium, Buddleja alternifolia, Clematis fruticosa) and six dominant grass species (Bothriochloa ischaemum, Artemisia sacrorum, Stipa bungeana, Cleistogenes squarrosa, Stipa grandis, Lespedeza bicolor) were selected from a stable grassland community in the Loess Plateau (China). The relative importance value and niche breadth were used as comprehensive quantitative indices to characterize the status, role, and degree of dominance of plant species in the community. We found that relative importance value and niche breadth were higher overall in shrub species than in most grass species, except B. ischaemum. Meanwhile, the relative importance value was significantly correlated with plant phosphorus concentration, plant carbon:nitrogen ratio, rhizosphere soil organic carbon, rhizosphere soil total nitrogen, rhizosphere soil total phosphorus, rhizosphere bacterial α-diversity. A stepwise regression analysis indicated that, among the plant and rhizosphere characteristics of these species, only their rhizosphere bacterial α-diversity and plant root carbon concentration primarily influence ecological niche patterns of these plant species in the community. In summary, our study reveals that shrub species occupy more advantageous ecological niches than grass species in a stable community due to the active rhizosphere interactions, providing a new opportunity to disentangle the mechanisms underlying the plant community assembly in grassland.

Mycorrhizal suppression and phosphorus addition influence the stability of plant community composition and function in a temperate steppe

Nutrient enrichment can reduce ecosystem stability, typically measured as temporal stability of a single function, e.g. plant productivity. Moreover, nutrient enrichment can alter plant–soil interactions (e.g. mycorrhizal symbiosis) that determine plant community composition and productivity. Thus, it is likely that nutrient enrichment and interactions between plants and their soil communities co‐determine the stability in plant community composition and productivity. Yet our understanding as to how nutrient enrichment affects multiple facets of ecosystem stability, such as functional and compositional stability, and the role of above–belowground interactions are still lacking.We tested how mycorrhizal suppression and phosphorus (P) addition influenced multiple facets of ecosystem stability in a three‐year field study in a temperate steppe. Here we focused on the functional and compositional stability of plant community; functional stability is the temporal community variance in primary productivity; compositional stability is represented by compositional resistance, turnover, species extinction and invasion. Community variance was partitioned into population variance defined as community productivity weighted average of the species temporal variance in performance, and species synchrony defined as the degree of temporal positive covariation among species.Compared to treatments with mycorrhizal suppression, the intact AM fungal communities reduced community variance in primary productivity by reducing species synchrony at high levels of P addition. Species synchrony and population variance were linearly associated with community variance with the intact AM fungal communities, while these relationships were decoupled or weakened by mycorrhizal suppression. The intact AM fungal communities promoted the compositional resistance of plant communities by reducing compositional turnover, but this effect was suppressed by P addition. P addition increased the number of species extinctions and thus promoted compositional turnover.Our study shows P addition and AM fungal communities can jointly and independently modify the various components of ecosystem stability in terms of plant community productivity and composition.

Plant community and the influence of plant taxonomic diversity on community stability and invasibility: A case study based on Solidago canadensis L.

Invasive alien plants (IAPs) can negatively affect plant taxonomic diversity, community stability, and invasibility in the invaded habitats. This study aimed to assess the degree of influence of the IAP Solidago canadensis L. under various levels of invasion (i.e., light, moderate, and heavy invasion based on its relative abundance in the invaded communities) on plant taxonomic diversity, community stability, and invasibility. In addition, we determined the contribution of plant taxonomic diversity to community stability and invasibility under various levels of S. canadensis invasion. The degree of influence of S. canadensis on plant taxonomic diversity and community stability increases as the level of S. canadensis invasion increases. Community invasibility increases as the level of S. canadensis invasion increases. The competitive advantage of S. canadensis is negatively associated with all indexes of plant taxonomic diversity and community stability but positively connected with community invasibility. Community stability is positively related to Shannon's diversity and Simpson's dominance indexes but negatively associated with community invasibility. Inversely, communities were more likely to be invaded when they had less plant taxonomic diversity. Thus, plant communities with lower values of plant taxonomic diversity and community stability are more vulnerable to S. canadensis invasion. Plant diversity causes a greater pressure on community stability than the other indexes of plant taxonomic diversity under various levels of S. canadensis invasion. However, the contribution intensity of the number of plant species to community invasibility is higher than the other indexes of plant taxonomic diversity under various levels of S. canadensis invasion.

荒漠草原植物群落结构及其稳定性对增水和增氮的响应

通过在荒漠草原开展增水和增氮野外控制试验，研究增水和增氮对荒漠草原植物群落结构、物种多样性及群落稳定性的影响。结果表明：（1）增水和增氮处理显著影响了荒漠草原植物群落结构和地上生物量，而对植物群落稳定性影响不显著（P>0.05）。增水处理显著增加了豆科和禾本科植物地上生物量（101.3%和57.9%）（P<0.05）；增水+增氮处理显著增加了植物群落盖度（43.2%）和地上生物量（112.4%）及不同功能群（禾本科和杂类草）植物盖度（75.5%和47.3%）和地上生物量（139.3%和85.7%）（P<0.05）。与增氮处理相比，增水+增氮处理显著增加了植物群落和不同功能群（禾本科和杂类草）植物高度、盖度和地上生物量（P<0.05）。（2）增水、增氮和增水+增氮处理均显著降低了植物群落Pielou指数（11.7%、8.7%和10.2%）（P<0.05）。（3）增水和增水+增氮处理提高了荒漠草原植物群落稳定性，而增氮处理降低了荒漠草原植物群落稳定性。增水处理荒漠草原植物群落稳定性效应大于增水+增氮处理。研究表明，荒漠草原植物群落结构受到氮沉降和降水增加的共同影响。增加降水对荒漠草原植物群落稳定性的积极效应可能会抵消部分氮沉降的消极影响，荒漠草原植物群落地上生物量及群落稳定性可能有所增加。;Desert grassland is predicted to be responsive to global climate change, such as increased atmospheric nitrogen deposition and precipitation. The structure, function and stability of plant community in desert grassland are often directly and indirectly affected by increased nitrogen deposition and precipitation. However, the response mechanism of plant community structure and stability in desert grassland to increase nitrogen deposition and precipitation are still not clear. We conducted the field experiments with water and nitrogen addition in desert grassland of Ningxia, China. We assessed the effects of increased atmospheric nitrogen deposition and precipitation on the plant community structure, species diversity and the plant community stability. The field experiment was conducted with four treatments, including control (CK), water addition (W), nitrogen addition (N), and water addition+nitrogen addition (W+N). We found that: (1) the plant community structure and aboveground biomass were effected significantly by water and nitrogen addition in desert grassland, but the plant community stability were not changed significantly(P>0.05). The plant aboveground biomass of Leguminosae and Gramineae were increased significantly by water addition (101.3% and 57.9%)(P<0.05). The coverage and aboveground biomass of plant community were significantly increased by 43.2% and 112.4% under water and nitrogen addition together, respectively. Water and nitrogen addition together also significantly increased the coverage (75.5% and 47.3%) and aboveground biomass (139.3% and 85.7%) of Leguminosae and Gramineae(P<0.05). Compared with nitrogen addition, water and nitrogen addition together significantly increased the height, coverage, aboveground biomass of plant community and different functional groups (Leguminosae and Gramineae)(P<0.05). (2) The Pielou index of plant community was decreased significantly by water addition, nitrogen addition, water and nitrogen addition together (11.7%, 8.7% and 10.2%)(P<0.05). (3) Plant community stability was improved by water addition, water and nitrogen addition together in desert grassland, while reduced by nitrogen addition. The effect of plant community stability by water addition was better than that of water and nitrogen addition together. The results indicated that the plant community structure would be affected by nitrogen deposition and precipitation increment in desert grassland. The positive effects of the increased precipitation on plant community stability in desert grassland may potentially offset negative effects of nitrogen deposition. Increased precipitation might lead to the increase of plant community aboveground biomass and plant community stability in desert grassland.

太岳山油松林火烧迹地恢复初期植物群落结构特征

为研究山西太岳山油松（Pinus tabuliformis）林过火后恢复初期林下草本植物群落结构，以2019年3月太岳山油松林火烧迹地为研究对象，采用群落相似性指数、多样性指数、稳定性系数、TWINSPAN数量分类和DCA排序等方法对群落组成、多样性、类型及稳定性等进行了研究。结果表明：（1）火烧迹地恢复初期以低矮灌木和多年生草本植物为主，其中又以地面芽植物占比最大。优势植物主要为大披针薹草（Carex lanceolata）和多花胡枝子（Lespedeza floribunda）；（2）火烧迹地恢复初期各样地植物群落相似性系数和多样性指数相对较小，均匀度指数较大，但各样地恢复效果不尽相同，样地6和样地7的植物群落各项指标相对大于其他样地；（3）TWINSPAN数量分类将火烧迹地植物群落划分成：I.大披针薹草+南牡蒿（Artemisia eriopoda）+地榆（Sanguisorba officinalis）群丛、II.多花胡枝子+大披针薹草+二色棘豆（Oxytropis bicolor）群丛、III.多花胡枝子+大披针薹草+米口袋（Gueldenstaedtia verna）群丛、IV.多花胡枝子+大披针薹草+荠苨（Adenophora trachelioides）群丛、V.大披针薹草+白莲蒿（Artemisia stechmanniana）+狗娃花（Aster hispidus）群丛、VI.白莲蒿群丛、VII.大披针薹草+狗娃花+野艾蒿（Artemisia lavandulifolia）群丛；（4）DCA排序结果表明，火烧迹地恢复初期植物群落结构单一，沿样地和坡位变化较小，仅区分出样地7和其他样地两大类植物群落。（5）火烧迹地恢复初期植物群落处于不稳定的状态，但各样地间群落稳定性存在一定差别，其中样地1最大，样地5最小。总之，研究区植物群落处于演替初期，各样地间植物群落稳定性较差，多样性和整体相似性较小，但优势种群相似性较高，植物群落结构仍处于动态变化之中。研究揭示了太岳山火烧迹地恢复初期植物群落结构特征，积累了该区域火烧迹地植物群落生态学数据，同时可为该区域生态恢复提供科学依据。;To study the community structure of understory herbaceous plants in the early recovery stage after the fire, the burned Pinus tabuliformis forests areas of Taiyue Mountain in March 2019 were selected to investigate the plant community structure at the early ecological restoration stage. The community similarity index, diversity index, stability index, TWINSPAN, and DCA were employed for analyzing the structure, diversity, and stability of plant communities. Our results show that in the early restoration stage, the shrub, and perennial grass were dominants in the communities, among which the hemicryptophytes accounted for the largest proportion. The dominant species were Carex lanceolata and Lespedeza floribunda. Furthermore, the similarity coefficient and diversity index of plant community in seven sample plots were generally small, while the evenness index was comparably higher. However, the plant community feature among seven plots existed heterogeneity, and all indicators of plant communities in plot 6 and 7 were relatively higher than those in other sample plots. Moreover, seven plant community patterns were identified by the TWINSPAN method, including I. Carex lanceolata + Artemisia eriopoda + Sanguisorba officinalis community, II. Lespedeza floribunda+Carex lanceolata+Oxytropis bicolor community, III. Lespedeza floribunda+Carex lanceolata+Gueldenstaedtia verna community, IV. Lespedeza floribunda + Carex lanceolata+Adenophora trachelioides community, V. Carex lanceolata + Artemisia stechmanniana+Aster hispidus community, VI. Artemisia stechmanniana community, and VII. Carex lanceolata+Aster hispidus+Artemisia lavandulifolia community. The result of DCA ordination suggested that theplant community structures at the early ecological restoration stage of burned areas were simple; only a minor change occurred with plots and slope position. Among them, only plot 7 and the other two groups of plant communities were significantly different. The results further depicted that in the early recovery stage, the plant community was in an unstable state; the stability indexes in different sample plots were much different, with the highest value in plot 1 and lowest in plot 5. In conclusion, the plant community in the burned Pinus tabuliformis forests areas, whose structure is under dynamic changing, was still at an early stage of succession accompanied by poor stability and low diversity and similarity, but the dominant population has a high similarity, and the plant community structure is still in dynamic change. Our finding shighlights the characteristics of the plant community structure in the burned area of Taiyue Mountain at the early stage of restoration, accumulates ecological data of the plant community in the burned area, and can provide a scientific basis for ecological restoration in this area.

植物-土壤反馈与草地群落演替:菌根真菌和土壤病原菌的调控作用

由植物引起的根际土壤生物或非生物环境的改变能够反馈影响群落中不同植物的生长，直接改变共存植物的相对竞争关系，推动群落结构的动态变化。作为土壤生物群落的重要组成部分，土壤微生物在植物-土壤反馈关系中起到重要的调控作用，对解释植物群落的演替进程和方向有着重要的意义。在草地植物群落演替的早期阶段和外来物种入侵的过程中，宿主植物对丛枝菌根真菌（AMF）的依赖性较低，受本地病原菌的影响较小，一般不存在负反馈。在演替后期，植物对AMF更具依赖性，而积累的病原菌则产生较强的负反馈效应，从而促进群落物种共存和植物多样性，提高草地生产力和稳定性。研究微生物-植物反馈机制不仅有助于完善草地退化与恢复理论，还对退化草地恢复治理的实践有着指导意义。未来关于根际微生物-植物反馈在草地群落演替中的作用应该加强以下几方面的研究：（1）在实验方法上，开展专性微生物-植物反馈研究；（2）在测定指标上，进一步量化不同微生物在反馈关系中的功能差异；（3）在研究对象上，加强土壤微生物在植物群落水平的反馈研究；（4）在应用上，明晰植物-土壤反馈在退化草地恢复过程中的作用，指导草地管理实践。;Biotic and abiotic changes of soil properties (e.g. physical, chemical and biotic) caused by a plant affect the growth of other plant species within the same communities, reshape the competitive relationship between different species, and restructure the dynamic changes of species composition. The feedback between plant and soil has become an important concept for explaining the diversity, stability, dynamics and succession of plant communities. Its process and mechanism are also key scientific issues to understand the responses of terrestrial ecosystems to global changes. However, biotic factors, in particular soil microbes mediated plant-soil feedback are still poorly understood. These changes in key microbial groups, such as arbuscular mycorrhizal fungi (AMF) and soil pathogens may increase or decrease the plant growth, resulting in positive or negative plant-soil feedbacks. In the early successional stage or during exotic plant invasion, host plants preferentially utilizing abundant soil nutrients have low dependence on the AMF and are less affected by native pathogens. Generally, there is no negative feedback. In the late successional stage, as the nutrients are being depleted, AMF help host plants with better access to soil nutrients and increased resistance to stress and pathogens, which could generate positive feedback and potentially accelerate succession. However, the accumulated pathogens can generate negative feedback and contribute to plant species coexistence and diversity, and thus improved productivity and stability of grassland. The study of microbial feedbacks on plant community dynamic is not only helpful to improve the theory of grassland degradation and restoration, but also instructive to the practice of restoration and management of degraded grassland. In the future, the key issues of plant-microbe feedback in grassland community succession were suggested as follows. (1)In experimental methods, it is necessary to test the net effect of obligate microbes dynamics on the plant succession using a fully reciprocal inoculation experiment which involves host-mediated differentiation of microbial communities and differential effects of the microbes on the plant fitness. (2)Regarding measurement indexes, further work quantizing the trade-off between the nutrient uptake and the carbon allocated to the microbes by host plant is needed. Comparing the ratios of nutrient benefit versus carbon cost between plants reciprocally inoculated with own and foreign microbial communities would enable us to evaluate functional variation between different microbes. (3)For research objects, the impacts of microbes on plant community structure require more empirical attention. In terms of application, the role of plant-microbe feedback on the restoration of degraded grassland is clarified to guide grassland management.

深圳近海公园植物群落结构特征及其与景观格局的相关性

城市公园植物群落为城市生态系统提供重要的生态服务。对深圳最具代表性的6个近海城市公园进行实地调查，同时结合高分辨率的遥感图像，分析其植物群落结构特征及其与公园内部景观格局的相关关系。结果表明：（1）共调查到近海公园植物108科310属471种，其中乡土植物82科169属231种。草本植物中乡土植物比例较高，而木本中乡土植物占比较低。（2）TS-4和H-1分别是近海公园最常见的乔灌群落类型和草本群落类型，其样地量分别占总量的39%和26%。常见群落的指示种多数具有热带性质并占据主体地位。（3）公园中灌木植物种数低于乔木和草本植物，但群落稳定性较高。（4）半自然型和人工型近海公园各类植物的相似性，以灌木层植物最低。（5）公园整体景观格局中，斑块密度与林地面积比、林地最大斑块面积比呈显著负相关（P<0.05）。（6）各层植物多样性也受到景观格局显著影响：草本层植物多样性与草地、林地的斑块形状复杂程度分别呈显著负相关（P<0.05）；灌木层植物多样性与林地、水体的景观破碎度呈显著负相关（P<0.05）；乔木层植物多样性与草地最大斑块指数呈显著负相关（P<0.05）。公园景观破碎度的增大可能会导致植被景观面积减少。建议在公园植物造景初期就要重视对灌木的运用，尤其是一些生态本底比较脆弱的公园，以提高植物群落的稳定性和低维护性。同时应尽可能保留大面积的核心植被生态斑块，更好地发挥其生态功能。研究结果可为城市公园的规划设计、植物群落的优化配置与城市生物多样性保护提供依据。;Plant communities in urban parks provide essential ecological services for the urban ecosystem. Based on the field survey of six most representative coastal urban parks in Shenzhen, and combined with high-resolution remote sensing images, the characteristics of plant community structure and its correlation with the internal landscape pattern of the parks were analyzed. The features of plant community structure and its relationship with the internal landscape patterns of the parks were analyzed. The results showed that: (1) A total of 471 plant species belong to 108 families and 310 genera were investigated, among which 231 species were native plants from 169 genera and 82 families. The proportion of native plants is higher in herbaceous plants, while the proportion of native plants is lower in woody plants. (2) TS-4 and H-1 were respectively the most common arbor-shrub community type and herbaceous community type, with their sample plots accounted for 39% and 26% of the total plots, respectively. Most indicator species of frequent communities were tropical and dominant species. (3) The species richness of shrub plants in the parks was lower than arbor and herbaceous plants, but the community stability was higher. (4) The lowest similarity of plants appeared in shrubs between semi-natural and artificial offshore parks. (5) In the overall landscape pattern of the parks, patch density was negatively correlated with the ratio of forest area and the area ratio of the maximum patch for forest land (P<0.05). (6) The plant diversity of each plant layer was also significantly affected by landscape patterns. The plant diversity in the herb layer presented a significantly negative correlation with the patch shape complexity of grassland and woodland, respectively (P<0.05). That in the shrub layer had a significantly negative correlation with landscape fragmentation degree of woodland and water, respectively (P<0.05). In the tree layer, a significantly negative correlation appeared between the plant diversity and the maximum patch index (P<0.05). The increase in the landscape fragmentation of parks may lead to the reduction of vegetation landscape area. It is suggested that the use of shrubs should be emphasized in the early stage of plant landscaping in parks, especially in some parks with relatively fragile ecological background, so as to improve the stability and low maintenance of plant communities. At the same time, a large area of core vegetation ecological patches should be preserved as much as possible to give better play to its ecological function. The research results provide a reference for the planning and designing of urban parks, the optimal allocation of plant communities, and the conservation of urban biodiversity.