Stability Of Plant Communities Research Articles

露天煤矿排土场边坡植被组成特征及其群落稳定性评价

研究植被恢复过程中植物群落组成、结构及稳定性的变化，可进一步了解到植物群落的演替过程及规律。采用空间代时间的方法对内蒙古锡林郭勒盟北电胜利露天煤矿4个排土场边坡人工恢复植被进行群落调查，在此基础上采用多样性指数与优化后的M.Godron稳定性指数对植物物种组成、物种多样性及其群落稳定性进行分析，探究不同恢复年限排土场边坡植被在恢复过程中群落特征及稳定性变化特征。结果表明：（1）排土场边坡植物物种组成共有16科44属56种，植物群落组成较简单，其中禾本科种类最多，生长型以草本植物为主。（2）随着恢复年限的增加，植物生活型由一、二年生转变为多年生，坡面优势种由人工种植植物转变为本土植物。（3）整体看，随着恢复年限增加，物种多样性呈下降趋势，群落稳定性整体呈上升趋势。（4）由于不同坡向土壤微环境差异，北坡恢复效果及稳定性好于南坡。本研究在一定程度上可为露天煤矿排土场边坡人工修复过程中植物物种及合理配置模式的选择提供科学依据。;Open-pit coal mine could destroy the original natural ecosystem, forming a considerable number of abandoned mining lands, causing a series of ecological problems as well. Revegetation is the core of ecological reconstruction, which has impacts on community characteristics and biological diversity of the vegetation, and does well to the soil physical and chemical properties at the same time. At present, studies on revegetation in mining areas, mainly focusing on the improvement of revegetation technology, the effect of vegetation and soil restoration, and vegetation allocation model, etc. There are less researches on the changes of plant community structure and stability in time series. As an important characteristic of ecosystem structure and function, community stability has an impact on the laws and characteristics of the stability of vegetation. M.Godron index is a classical method for community stability evaluation, but it can only reflect the stability of the plant community without considering the changes of community structure. Therefore, the comprehensive analysis of the stability and composition characteristics of the plant community can further understand the ecological characteristics and restoration process of the plant community in the mining area, which is significant to the ecological restoration of the mining area. In this study, the communities of artificial revegetation of 4 waste dump slopes in Beidian Shengli open-pit coal mine in Xilinguole League of the Inner Mongolia, were phytocoenologically investigated using the method of space-substitute-time. The community characteristics and stability in the process of revegetation of waste dump slope with different restoration years were explored. The species composition, species diversity, and community stability of vegetation were analyzed using diversity index and the optimized M.Godron index. The results showed that:(1) a total of 56 naturally occurring plant species, belonging to 44 genera and 16 families, were observed in the slope of waste dump which mainly composed by Gramineae plants and the major growth type was herbaceous plants. (2) With the increase of restoration years, the life form of plants changed from biennial plants to perennial plants, and the dominant species on slope changed from artificial plants to native plants. (3) On the whole, the species diversity decreased and the community stability increased with the increase of restoration years. (4) Due to the difference of soil micro-environment in different slope directions, the restoration effect and stability of north slope was better than the south. To some extent, these findings can provide a scientific basis for the selection of plant species and rational allocation mode in the process of artificial remediation of open-pit coal mine dump.

Designing Diverse Agricultural Pastures for Improving Ruminant Production Systems

Pasture-based production systems represent a significant sustainable supplier of animal source foods worldwide. For such systems, mounting evidence highlights the importance of plant diversity on the proper functioning of soils, plants and animals. A diversity of forages and biochemical-primary and secondary compounds- at appropriate doses and sequences of ingestion, may lead to benefits to the animal and their environment that are greater than grazing monocultures and the isolated effects of single chemicals. Here we review the importance of plant and phytochemical diversity on animal nutrition, welfare, health, and environmental impact while exploring some novel ideas about pasture design and management based on the biochemical complexity of traditional and non-traditional forage sources. Such effort will require an integration and synthesis on the morphology, ecophysiology and biochemistry of traditional and non-traditional forage species, as well as on the foraging behavior of livestock grazing diverse pasturelands. Thus, the challenge ahead entails selecting the “right” species combination, spatial aggregation, distribution and management of the forage resource such that productivity and stability of plant communities and ecological services provided by grazing are enhanced. We conclude that there is strong experimental support for replacing simple traditional agricultural pastures of reduced phytochemical diversity with multiple arrays of complementary forage species that enable ruminants to select a diet in benefit of their nutrition, health and welfare, whilst reducing the negative environmental impacts caused by livestock production systems.

Co-occurrence history increases ecosystem stability and resilience in experimental plant communities.

Understanding factors that maintain ecosystem stability is critical in the face of environmental change. Experiments simulating species loss from grassland have shown that losing biodiversity decreases ecosystem stability. However, as the originally sown experimental communities with reduced biodiversity develop, plant evolutionary processes or the assembly of interacting soil organisms may allow ecosystems to increase stability over time. We explored such effects in a long-term grassland biodiversity experiment with plant communities with either a history of co-occurrence (selected communities) or no such history (naïve communities) over a 4-yr period in which a major flood disturbance occurred. Comparing communities of identical species composition, we found that selected communities had temporally more stable biomass than naïve communities, especially at low species richness. Furthermore, selected communities showed greater biomass recovery after flooding, resulting in more stable post-flood productivity. In contrast to a previous study, the positive diversity-stability relationship was maintained after the flooding. Our results were consistent across three soil treatments simulating the presence or absence of co-selected microbial communities. We suggest that prolonged exposure of plant populations to a particular community context and abiotic site conditions can increase ecosystem temporal stability and resilience due to short-term evolution. A history of co-occurrence can in part compensate for species loss, as can high plant diversity in part compensate for the missing opportunity of such adaptive adjustments.

Mycorrhizal fungi maintain plant community stability by mitigating the negative effects of nitrogen deposition on subordinate species in Central Asia

AbstractQuestionsPlant community stability is threatened by increasing numbers of simultaneously changing factors such as increased precipitation and nitrogen (N) deposition. Despite the pivotal roles of arbuscular mycorrhizal fungi (AMF) for plant community dynamics, only few studies have paid attention to their roles in maintaining plant community stability under global change. We therefore assessed the interactive effects of a realistic N deposition and AMF on plant community temporal stability under future increased precipitation scenarios.LocationGurbantunggut desert, China.MethodsWe conducted a four‐year field experiment simulating a realistic N deposition and with/without AMF treatments in one typical ephemeral plant community, dynamically monitoring the changes in plant community biomass and composition.ResultsWe found that suppression of AMF significantly reduced Shannon–Wiener diversity and evenness while the realistic N deposition only marginally reduced the Shannon–Wiener diversity. Suppression of AMF and increased N deposition highly increased the species turnover. Particularly, the stability of subordinate plant species significantly correlated to the community‐level stability. AMF were able to buffer the negative effects of increased N deposition on plant community diversity, to maintain community‐level stability.ConclusionsOur study supports the subordinate insurance hypothesis, highlighting the considerable roles of subordinate plant species in maintaining community stability. Furthermore, our results indicate the joint roles of AMF and N deposition in regulating plant community stability, and point to the importance of taking AMF and the realistic N deposition into account for understanding the responses of community stability to multiple global change scenarios.

Synchrony matters more than species richness in plant community stability at a global scale

The stability of ecological communities is critical for the stable provisioning of ecosystem services, such as food and forage production, carbon sequestration, and soil fertility. Greater biodiversity is expected to enhance stability across years by decreasing synchrony among species, but the drivers of stability in nature remain poorly resolved. Our analysis of time series from 79 datasets across the world showed that stability was associated more strongly with the degree of synchrony among dominant species than with species richness. The relatively weak influence of species richness is consistent with theory predicting that the effect of richness on stability weakens when synchrony is higher than expected under random fluctuations, which was the case in most communities. Land management, nutrient addition, and climate change treatments had relatively weak and varying effects on stability, modifying how species richness, synchrony, and stability interact. Our results demonstrate the prevalence of biotic drivers on ecosystem stability, with the potential for environmental drivers to alter the intricate relationship among richness, synchrony, and stability.

Plant wax evidence for precipitation and vegetation change from a coastal sinkhole lake in the Bahamas spanning the last 3000 years

Plant wax hydrogen isotopic composition is commonly used to reconstruct the hydrogen isotopic composition of precipitation used by terrestrial vegetation. However, mangroves growing in coastal environments take up a mixture of freshwater and seawater. Biosynthetic fractionation (between source water and plant wax) differs between plant types and as a function of salinity, potentially complicating interpretations of past precipitation in coastal environments. In order to reconstruct Holocene hydrologic and ecologic changes archived within sediments from Blackwood Sinkhole on Abaco Island in The Bahamas, we adopt a multi-proxy approach using plant wax hydrogen isotopic composition (δ2H) to reconstruct paleohydrology, together with plant wax carbon isotopic composition (δ13Cwax), sterol biomarkers and pollen abundances to identify vegetation change. When pollen indicates a stable terrestrial plant community (2950–850 cal yrs BP), variations of δ2H values measured on the plant wax C28n-alkanoic acid are interpreted in terms of precipitation isotope (δ2Hprecip) changes, with 2H-depletion from 2950 to ∼2100 cal yrs BP and ∼1700 to 1000 cal yrs BP. However, interpretation is complicated at 850 cal yrs BP, when δ2H values decrease (−50‰) concurrent with increased Laguncularia racemosa (white mangrove) and Conocarpus erectus (buttonwood mangrove), and the mangrove-derived biomarker, taraxerol. We develop a pollen-based correction for mangrove inputs, yielding reconstructed precipitation isotope estimates (δ2Hprecip-corr). Low δ2Hprecip-corr values are synchronous with increased abundance of pine pollen, both of which may indicate wetter conditions from 850 cal yrs BP to present. This study provides additional evidence that mangroves can complicate hydrologic reconstructions from n-alkyl terrestrial plant wax biomarkers, and that such complication can be removed by pollen-based correction. After correcting for mangrove inputs, we obtain estimates of δ2Hprecip-corr from −33 to +25‰ throughout the last 2950 years, with uncertainties on the order of 10–20‰.

Impacts of snow on seed germination are independent of seed traits and plant ecological characteristics in a temperate desert of Central Asia

Seed germination profoundly impacts plant community composition within the plant life cycle. Snow is an important source of water for seed germination in the temperate deserts of Central Asia. Understanding how seed germination responds to variations in snow cover in relation to seed traits and plant ecological characteristics can help predict plant community sustainability and stability in Central Asia under a scenario climate change. This study investigated the seed germination of 35 plant species common to the Gurbantunggut Desert in Central Asia under the three snow treatments: (1) snow addition; (2) ambient snow; and (3) snow removal. Two-way analysis of variance (ANOVA) tests were performed to assess interactions among the impacts of snow treatments, seed traits and plant ecological characteristics on seed germination. Phylogenetic generalized least-squares (PGLS) model was used to test the relationships between seed traits and seed germination. The results demonstrated that snow variations had no significant impacts on seed germination overall. Seed germination under the snow addition treatment was similar with that under the ambient snow treatment, irrespective of seed traits and plant ecological characteristics. Snow removal only had negative impacts on seed germination for certain groups of seed traits and plant ecological characteristics. Seed mass positively affected seed germination, showing a linear increase of arcsin square root-transformed seed germination with log-transformed seed mass. Seed shape also profoundly impacted seed germination, with a higher germination percentage for elongated and flat seeds. Seed germination differed under different plant life forms, with semi-shrub species showing a significantly higher germination percentage. Most importantly, although snow treatments, seed traits and plant ecological characteristics had no interactive effects on seed germination overall, some negative impacts from the snow removal treatment were detected when seeds were categorized on the basis of seed mass and shape. This result suggests that variations of snow cover may change plant community composition in this temperate desert due to their impacts on seed germination.

Niche differentiation is the underlying mechanism maintaining the relationship between community diversity and stability under grazing pressure

The relationship between diversity and stability and its maintenance mechanisms are important topics in current ecological research. In this study of Leymus chinensis grasslands in the Xilin River Basin, Inner Mongolia, we analyzed the relationship between diversity (species diversity, functional diversity, and functional group diversity) and stability (multidimensional stability defined by relationships between resistance, resilience, functional variability, and structural variability) under the joint interactions of complex environmental factors (climatic, topographical, soil, and grazing factors) from the perspective of the community assembly (community-weighted trait means, trait divergence, and trait convergence), and the maintenance mechanisms of diversity and stability of the grassland ecosystem. We found that (i) functional diversity had the highest explanatory power for community stability, and the main path relationships among grazing factors, plant functional traits, functional diversity, and community stability revealed that niche differentiation was mainly caused by grazing and the response of species diversity to environmental conditions were the key mechanisms for maintaining the relationship between diversity and stability. (ii) The differentiation of species diversity was mainly a consequence of environmental filtering which is due to soil factors, whereas the differentiation of functional group diversity was mainly caused by differences in community-weighted trait means which were determined by climatic factors. The differentiation of functional diversity mainly depended on the divergence of plant functional traits which mainly correlated with an increase in grazing intensity. The diversity of functional groups mainly depended on climatic conditions, and the magnitude of functional diversity mainly depended on grazing intensity. Our study is expected to enrich understanding of stability maintenance mechanisms in grassland ecosystems and provide guidance for grassland restoration and biodiversity conservation.

Determinants of ecosystem stability in a diverse temperate forest

Understanding how diversity affects ecosystem stability is crucial for predicting the consequences of continued habitat and biodiversity loss on ecosystem functions and services. Long‐term productivity stability in plant communities is often associated with greater species, phylogenetic or functional diversity, more complex size and age structures, or higher asynchrony in species fluctuations (compensatory dynamics), all potentially increasing community resistance to perturbations. However, the relative importance of these stabilizing pathways is still poorly understood, especially in old‐growth species‐rich forests. Here we explore how compensatory dynamics and multiple facets of diversity underpin temporal stability of wood biomass production over forty years in a Japanese temperate forest, based on more than 45 500 stem increments from 15 species. Whereas the effect of species richness and phylogenetic diversity was small, the old‐growth structural attributes markedly increased community stability via increased asynchrony in the performance of co‐occurring species. Greater standing tree volume, stem density and interspecific variation in growth rates enhanced productivity stability both directly and indirectly via increased asynchrony. This corroborates the predictions of increased compensatory dynamics with increased asymmetric competition for light in a more productive environment. Asymmetric competition in old‐growth patches, between dominant oaks and sub‐canopy shade‐tolerant firs and maples, is a major driver of productivity stability over time via compensatory dynamics. Overall productivity remains relatively constant in old‐growth patches, as abundant firs and maples in the lower canopy layers compensate for biomass losses in canopy oaks caused by aging, wind and snow disturbances. Younger forest patches, composed of fast‐growing, shade‐intolerant species, had a lower stability of productivity, with reduced stem basal area and tree density due to higher understory bamboo coverage preventing tree regeneration and growth. We provide new insights into mechanisms underlying the stability of ecosystem functioning in diverse forest ecosystems, and emphasize the importance of preserving and supporting old‐growth forests and their structural complexity.

Resource enrichment combined with biomass removal maintains plant diversity and community stability in a long-term grazed grassland

Abstract Aims Long-term heavy grazing reduces plant diversity and ecosystem function by intensifying nitrogen (N) and water limitation. In contrast, the absence of biomass removal can cause species loss by elevating light competition and weakening community stability, which is exacerbated by N and water enrichment. Hence, how to maintain species diversity and community stability is still a huge challenge for sustainable management of worldwide grasslands. Methods We conducted a 4-year manipulated experiment in six long-term grazing blocks to explore combination of resource additions and biomass removal (increased water, N and light availability) on species richness and community stability in semiarid grasslands of Inner Mongolia, China. Important Findings In all blocks treated with the combination of resource additions and biomass removal, primary productivity increased and species richness and community stability were maintained over 4 years of experiment. At both species and plant functional group (PFG) levels, the aboveground biomass of treated plants remained temporally stable in treatments with the combination of N and/or water addition and biomass removal. The maintenance of species richness was primarily caused by the biomass removal, which could increase the amount of light exposure for grasses under resource enrichment. Both species asynchrony and stability of PFGs contributed to the high temporal stability observed in these communities. Our results indicate that management practices of combined resource enrichment with biomass removal, such as grazing or mowing, could not only enhance primary productivity but also maintain plant species diversity, species asynchrony and community stability. Furthermore, as overgrazing-induced degradation and resource enrichment-induced biodiversity loss continue to be major problems worldwide, our findings have important implications for adaptive management in semiarid grasslands and beyond.

Weather fluctuations drive short‐term dynamics and long‐term stability in plant communities: A 25‐year study in a Central European dry grassland

AbstractQuestionInfrequent events of extreme drought or extreme temperatures may considerably affect the structure and functioning of vegetation. Here we investigate how fluctuations in precipitation and temperature shape year‐to‐year dynamics and plant species composition in a dry grassland community, and how this variation affects plants with different life histories.LocationDry grassland (Festucion valesiacae) in the Pavlov Hills, SE Czech Republic.MethodsLong‐term trends in vegetation change in the grassland studied were assessed by the ordination of plot records from vegetation surveys performed between 1930 and 2019. In addition, year‐to‐year changes in vegetation were studied in seven permanent plots of 16 m2 surveyed annually from 1993 to 2018. Variation in species composition and abundances was related to temperature and precipitation in the preceeding two springs, summers, autumns and winters using ordinations and mixed‐effect linear models.ResultsThere were no remarkable directional changes in the grassland community over the period 1930–2019. However, during the last 25 years, the community exhibited pronounced year‐to‐year fluctuations, which depended on weather conditions in the previous two years. Species with different life histories (e.g. perennials vs. annuals) and different ecology (e.g. ruderal vs. dry‐grassland species) responded differently to specific weather patterns. Perennials were sustained by wet summers, annuals benefitted from wet springs and autumns and moderately warm and wet winters, and covers of ruderals of mixed life histories increased after dry summers.ConclusionsPlant species composition in a Central European dry grassland shows remarkable year‐to‐year dynamics in response to weather patterns over the previous two years. These community changes are non‐directional and contribute to the stability of this grassland, which has not changed considerably over the past 90 years. However, increasing frequency of drought events because of ongoing climate change can result in a directional change with an expansion of ruderal species.

Factors shaping alternate successional trajectories in burned black spruce forests of Alaska

AbstractDisturbances can interrupt feedbacks that maintain stable plant community structure and create windows of opportunity for vegetation to shift to alternative states. Boreal forests are dominated by tree species that overlap considerably in environmental niche, but there are few tests of what conditions initiate and sustain different forest states. Here, we examine patterns of post‐fire growth and density of tree seedlings in early succession and use structural equation models to estimate relative effects of environmental and pre‐fire conditions, fire characteristics, and biotic interactions. We surveyed tree seedling recruits for 13 yr across a broad range of environmental and fire conditions (n = 89) in Alaskan black spruce stands that burned in 2004. Densities of established seedlings at 13 yr were strongly determined by initial recruitment that occurred within 2 yr after fire. High proportional combustion of the soil organic layer (fire severity) led to increased densities of deciduous seedlings but not of black spruce and had a positive influence on aboveground biomass of all species. Biotic interactions such as mammalian herbivory or woody competition, potential mechanisms for relay floristic succession, had no detectable effects on tree seedling densities or biomass. Repeated surveys instead suggested persistent shifts in successional trajectories of tree communities from spruce to deciduous dominance at sites where high fire severity created positive conditions for deciduous seedling recruitment and growth. Unless future species interactions alter the deciduous dominance of tree seedling composition, the vegetation transformations that we observed in response to high fire severity are likely to persist over the short fire cycle that increasingly characterizes the fire regime of Interior Alaska.

Additive negative effects of decadal warming and nitrogen addition on grassland community stability

Abstract Much recent research has explored how global warming and increased nitrogen (N) deposition, two important components of global environmental changes, influence the structure and functioning of natural ecosystems. However, how ecosystem dynamics respond to the combination of long‐term warming and N enrichment remains largely unexplored. We investigated the impact of warming and N addition on the temporal stability of plant communities in a decade‐long field experiment, conducted in a desert steppe in northern China, using a split‐plot design with warming as the main‐plot factor and N addition as the split‐plot factor. Long‐term warming and N addition had additive, negative effects on plant community stability. A warming‐induced decrease in species richness was not a significant driver of decreased community stability, which was instead driven by the decreased stability of dominant species under warming. On the other hand, a N‐induced decrease in community stability was ascribed to both decreased stability of dominant and common species and decreased asynchronous population dynamics under N addition. Synthesis. Our results suggest that ongoing anthropogenic environmental changes may have appreciable consequences for the stability of natural grassland functions and services while also highlighting the different mechanisms associated with the similar effects of climate warming and increased N deposition on grassland community stability.

Erigeron annuus (L.) Pers. and Solidago canadensis L. antagonistically affect community stability and community invasibility under the co-invasion condition.

The successful invasion of one invasive alien plant (IAP) can generate a favorable habitat in the invaded communities that beneficial to the successful invasion of the subsequent IAP. Advanced variations in the species number of IAP have the potential to alter the functional similarity and dissimilarity between IAP and co-existing native plant species (NPS), plant taxonomic diversity, plant functional diversity, community stability, and community invasibility. This study aims to evaluate the effects of the co-invasion of two notorious IAP, Erigeron annuus (L.) Pers. and Solidago canadensis L., on the functional similarity and dissimilarity between IAP and co-existing NPS, plant taxonomic diversity, plant functional diversity, community stability, and community invasibility in East China by using a comparative study. Results presented that: (I) IAP and co-existing NPS tend to converge functionally under E. annuus invasion and the functional similarity between IAP and co-existing NPS under E. annuus invasion supports the habitat filtering; (II) IAP and co-existing NPS tend to diverge functionally under S. canadensis invasion and the co-invasion condition and the functional dissimilarity between IAP and co-existing NPS under S. canadensis invasion and the co-invasion condition supports the niche differentiation; (III) plant taxonomic diversity was dramatically reduced under invasion condition, especially under S. canadensis invasion; (IV) Mason's α functional diversity was remarkably elevated under S. canadensis invasion and the co-invasion condition; (V) E. annuus and S. canadensis antagonistically affect community stability and community invasibility under the co-invasion condition compared with their independent invasion.

Evaluation of Vegetation after Four Years in a Caatinga Fragment in the State of Sergipe, Brazil

Abstract The comparison of vegetation at two different moments allows for recognizing the stability of plant communities. The structure and floristic composition of a Caatinga fragment in the municipality of Poco Verde, state of Sergipe, were evaluated after four years (2011-2015). Sampling was performed through 30 plots of 20 m × 20 m, considering individuals with circumference at breast height ≥ 6 cm. Despite the increase in density (0.79%) and basal area (4.82%), changes in floristic composition, in Shannon-Wiener diversity (from 3.33 nats.ind-1 to 3.30 nats.ind-1) and in Pielou equability (from 0.78 to 0.80) were small. None of the structural parameters evaluated (richness, density, basal area, importance value and Shannon-Wiener diversity) significantly differed between evaluation periods. The vegetation remained stable over time, tolerating current anthropization levels and enabling the use of its natural resources through planned management.

The role of alien species on plant-floral visitor network structure in invaded communities.

The interactions between pairs of native and alien plants via shared use of pollinators have been widely studied. Community level studies however, are necessary in order to fully understand the factors and mechanisms that facilitate successful plant invasion, but these are still scarce. Specifically, few community level studies have considered how differences in invasion level (alien flower abundance), and degree of floral trait similarity between native and invasive species, mediate effects on native plant-pollinator communities. Here, we evaluated the role of alien species on overall plant-floral visitor network structure, and on species-level network parameters, across nine invaded coastal communities distributed along 205 km in Yucatán, México that vary in alien species richness and flower abundance. We further assessed the potential the role of alien plant species on plant-floral visitor network structure and robustness via computational simulation of native and invasive plant extinction scenarios. We did not find significant differences between native and alien species in their functional floral phenotypes or in their visitation rate and pollinator community composition in these invaded sites. Variation in the proportion of alien plant species and flower abundance across sites did not influence plant-pollinator network structure. Species-level network parameters (i.e., normalized degree and nestedness contribution) did not differ between native and alien species. Furthermore, our simulation analyses revealed that alien species are functionally equivalent to native species and contribute equally to network structure and robustness. Overall, our results suggest that high levels of floral trait similarity and pollinator use overlap may help facilitate the integration of alien species into native plant-pollinator networks. As a result, alien species may also play a similar role than that of natives in the structure and stability of native plant and pollinator communities in the studied coastal sand dune ecosystem.

Effects of nitrogen and phosphorus inputs on soil nematode community in a degraded grassland.

Nematodes, occupying multiple trophic levels in the food web, play important roles in energy flow and nutrient cycling. Most of Chinese natural grasslands have been degraded due to long-term unreasonable utilization, such as over-grazing. External nutrient input is an important way to restore the ecological function of degraded grasslands. The main and intertative effects of nitrogen and phosphorus inputs on soil nematode abundance, trophic group composition and community structure were studied in the grasslands in Xilingol League of Inner Mongolia. Totally, 38 genera of nematodes were recorded. Tylencholaimus, Aphelenchoides, Thonus, and Scutylenchus were dominant genera in this degraded grassland. Nitrogen input decreased total abundances of soil nematodes, and that of omnivores-carnivorous nematodes and plant-feeding nematodes. Phosphorus input increased total abundances of soil nematodes, and that of fungal-feeding nematodes, omnivores-carnivorous nematodes, and plant-feeding nematodes. Nitrogen input inhibited the positive effects of phosphorus input on the abundances of total nematodes, omnivores-carnivorous nematodes and plant-feeding nematodes. Nutrient inputs had no effect on nematode diversity, which would be resulted from the stable plant community. Nitrogen input significantly increased nematode maturity index, decreased plant parasitic nematode maturity index (PPI), and greatly alleviated the negative effects of phosphorus input on PPI and Wasilewska index, indicating that nitrogen input could improve soil health condition and the stability of nematodes community. Our results would help improve our understanding of the effects of nutrient inputs on degraded grassland ecosystem from a soil biotic perspective.

Interspecific association of woody plant species and community stability in the <i>Eleutharrhena macrocarpa</i> habitat

Interspecific association of woody plant species and community stability in the <i>Eleutharrhena macrocarpa</i> habitat

Degree of invasion of Canada goldenrod (Solidago canadensis L.) plays an important role in the variation of plant taxonomic diversity and community stability in eastern China

AbstractUnderstanding the impacts of invaders on plant taxonomic diversity and community stability is significant for understanding the mechanisms underlying successful invasion. This study explored the impacts of the invasive plant Canada goldenrod (Solidago canadensis L.; goldenrod hereafter) with different degrees of invasion on plant taxonomic diversity and community stability by conducting a comparative study in eastern China. Degree of invasion was divided into the following categories, low (<35%, LDI), moderate (35–75%, MDI), and high (>75%, HDI), on the basis of the relative abundance of goldenrod in the invaded plant communities. Plant diversity, dominance, richness, and plant community stability noticeably decreased under HDI but plant diversity and dominance dramatically increased under LDI compared with the adjacent uninvaded plant communities. Plant diversity, dominance, richness, and community stability markedly declined as the degree of goldenrod invasion increased in the invaded plant communities. The greater plant diversity and dominance observed under LDI may be primarily driven by the passenger effects rather than a driving force of the presence of goldenrod. The greater competitive superiority of goldenrod over coexisting native plants under HDI might allow for invasion and enhance the risk of stochastic local extinction of several native species. A significantly positive diversity‐stability relationship was observed, which may explain the underlying mechanisms for the decreased plant community stability and drastic decline in plant diversity under HDI. Accordingly, the degree of invasion of goldenrod plays an important role in the variation of plant taxonomic diversity and community stability in eastern China.

Fine-scale substrate heterogeneity in green roof plant communities: The constraint of size.

Heterogeneity–diversity relationship (HDR) is commonly shown to be positive in accordance with classic niche processes. However, recent soil‐based studies have often found neutral and even negative HDRs. Some of the suggested reasons for this discrepancy include the lack of resemblance between manipulated substrate and natural settings, the treated areas not being large enough to contain species' root span, and finally limited‐sized plots may not sustain focal species’ populations over time. Vegetated green roofs are a growing phenomenon in many cities that could be an ideal testing ground for this problem. Recent studies have focused on the ability of these roofs to sustain stable and diverse plant communities and substrate heterogeneity that would increase niches on the roof has been proposed as a method to attain this goal. We constructed an experimental design using green roof experimental modules (4 m2) where we manipulated mineral and organic substrate component heterogeneity in different subplots (0.25 m2) within the experimental module while maintaining the total sum of mineral and organic components. A local annual plant community was seeded in the modules and monitored over three growing seasons. We found that plant diversity and biomass were not affected by experimentally created substrate heterogeneity. In addition, we found that different treatments, as well as specific subplot substrates, had an effect on plant community assemblages during the first year but not during the second and third years. Substrate heterogeneity levels were mostly unchanged over time. The inability to retain plant community composition over the years despite the maintenance of substrate differences supports the hypothesis that maintenance of diversity is constrained at these spatial scales by unfavorable dispersal and increased stochastic events as opposed to predictions of classic niche processes.