Spatial scale, plant identity and management effects on the diversity-productivity relationship in a semi-natural grassland

Although species richness has been hypothesized to be highest at 'intermediate' levels of disturbance, empirical studies have demonstrated that the disturbance-diversity relationship can be either negative or positive depending on productivity On the other hand, hypothesized productivity diversity relationships can be positive, negative or unimodal, as confirmed by empirical studies. However, it has remained unclear under what conditions each pattern is realized, and there is little agreement about the mechanisms that generate these diverse patterns. In this study, I present a model that synthesizes these separately developed hypotheses and shows that the interactive effects of disturbance and productivity on the competitive outcome of multispecies dynamics can result in these diverse relationships of species richness to disturbance and productivity The predicted productivity diversity relationship is unimodal but the productivity level that maximizes species richness increases with increasing disturbance. Similarly, the predicted disturbance diversity relationship is unimodal but the peak moves to higher disturbance levels with increasing productivity Further, these patterns are well explained by the opposite effects of productivity and disturbance on competitive outcome that are suggested by the change in community composition along these two environmental gradients: higher productivity favours superior competitors while higher disturbance levels favour inferior competitors.

Predicting the trajectory of ongoing diversity loss requires knowledge of historical development of community assemblages. Long-term data from palaeoecological investigations combined with key biodiversity measures in ecology such as taxonomic richness, functional diversity (FD), phylogenetic diversity (PD) and environmental factors expressed as Ellenberg indicator values (EIVs) could provide that knowledge. We explored the modern pollen–plant (moss polster pollen vs surrounding vegetation) diversity relationships for herbaceous and woody taxa in calcareous fens from two different regions in Estonia, NE Europe. Associations of taxonomic richness, vegetation composition, FD (including functional alpha diversity and trait composition), PD and EIVs in modern pollen vs plant data were studied with correlation analysis, Procrustes analysis and linear regression models. To test their potential use in palaeoreconstructions, diversity measures were applied on pollen data from Kanna spring fen reflecting fen vegetation development over the last nine millennia and diversity changes through time were studied using generalized additive models. Results showed significant pollen–plant richness correlations for herbaceous taxa at vegetation estimate scales up to 6 m radius and Procrustes analysis showed significant compositional associations at all plant estimate scales (up to 100 m). Woody taxa had no significant pollen–plant richness correlations but composition relationships were significant at plant estimate scales of 6–100 m. Traits that were best reflected by pollen data (both in terms of trait composition and functional alpha diversity) among woody and herbaceous taxa were seed number, clonality, SLA and LDMC. PD of herbaceous species was reflected by pollen data. Among the EIVs, Ellenberg L and T were significantly reflected by pollen data for both woody and herbaceous communities. Palaeoreconstruction from Kanna fen indicates that trends of woody taxa are mostly related to long-term changes in climate while diversity variables of herbaceous taxa closely follow autogenic processes within the fen. We suggest that pollen-based diversity estimates should be calculated separately for woody and herbaceous taxa as they clearly represent different spatial scales. Present study suggests that linking sedimentary pollen data with FD, PD and EIVs provides possibilities to examine long-term trends in community assembly and ecosystem processes that would be undetectable from traditional pollen diagrams.

Small-scale plant species richness and evenness in semi-natural grasslands respond differently to habitat fragmentation

Biodiversity and ecosystem functioning (BEF) relationships are important research issues in the context of biodiversity loss. However, most studies only explored BEF relationships using species richness as a proxy for biodiversity without considering the effects of species evenness and importance of functional diversity on ecosystem functioning. In the present study, we explored multiple relationships among in-stream environmental variables, species diversity (species richness and species evenness), functional diversity (functional richness, functional evenness and Rao’s quadratic entropy index) and biomass of benthic diatom communities from a Chinese mountainous river network. We tested two hypotheses: (1) species richness and evenness affect community biomass independently, and (2) species diversity directly affects community biomass and also indirectly affects community biomass by influencing functional diversity. We found that benthic diatom diversity and biomass were influenced by wetted width, conductivity, and pH. Species richness and evenness had positive and negative effects on community biomass, respectively; while, the effect of richness (with a pathway coefficient of 0.39) was stronger than that of evenness (−0.28). However, we have not found an interaction pathway between species richness and species evenness in structural equation models, indicating that the two effects on community biomass were independent of each other. Both functional richness and Rao’s quadratic entropy index had positive effects on community biomass, although effects of other variables blurred the relationship between functional richness and community biomass in structural equation modeling. Besides direct effects, species diversity also indirectly affected community biomass through influencing Rao’s quadratic entropy index, with direct effects (0.27) were more than twice stronger than indirect effects (0.12). Our findings imply that the selection effect played a dominant role in the relationship between diatom diversity and biomass, indicated by the negative species evenness and biomass relationship; meanwhile, the complementarity effect was also important. The inclusion of more diversity indices to explore the biodiversity-biomass relationship would help to provide a deeper and more comprehensive understanding of this relationship and its driving mechanisms. We suggest carrying out more studies on BEF relationships in streams and rivers to support protection practices for sustaining biodiversity and their ecosystem functions in natural lotic ecosystems.

Semi-natural grasslands under extensive grazing host a high diversity of plants whose diverse flower traits are crucial for insect pollinators, which are facing a worrying decline. We investigated how grazing regimes in dry calcareous grasslands influence the diversity and composition of flower traits important for pollinators. We measured the taxonomic diversity (TD) of the plant community, as well as the functional diversity (FD) and the community-weighted means (CWM) of seven morphological, phenological, and reflectance flower traits for insect-pollinated species across 116 plots in 22 farms and nearby abandoned areas spanning six regions in Italy and Switzerland. We compared managed and abandoned areas to assess differences in FD and CWM, and fitted two piecewise structural equation models to infer direct and indirect effects of grazing regimes on TD, FD and CWM. Extensive grazing did not alter flower traits’ FD compared to abandonment, but favoured flowers’ characteristics beneficial to pollinators, e.g., increased CWMs of flower size, flowering period length, and UV reflectance. Across different grazing regimes, local grazing pressure emerged as a key driver of TD and, in turn, of the FD and CWM of several flower traits. Plant communities with a more even distribution of dominant and rare species were positively associated with the FD of flower symmetry, flowering initiation and UV reflectance, as well as the representation of zygomorphic and non-yellow flowers. Maintaining extensive grazing is essential to preserve flower characteristics that are important for pollinators. Managing grazing intensity patterns at local spatial scales is crucial to increase the diversity of flower traits, which, in turn, may support a broad range of insect pollinators. • Extensive grazing enhances flower traits crucial for insect pollinators. • Local grazing pressure influences taxonomic and functional diversity. • An even grazing pressure enhances flower traits beneficial for pollinators.

The role of habitat disturbance on biodiversity is central as it promotes changes in ecological systems. That said, still little is known about the functional consequences of such changes. Functional diversity can be used to revealing more mechanistically the disturbance effects on communities by considering the richness and the distribution of traits among the species. Here we analyzed the response of functional and species diversity of ground beetles to flood disturbance to better understand the functioning of alluvial invertebrate communities. Ground beetles were sampled in periodically flooded grasslands along the Elbe River in Germany. We used generalized linear mixed effects models to unveil the relationships between flood disturbance, species and functional diversity, respectively. We measured different components of functional diversity (functional richness, evenness, dispersion, and divergence) and analyzed species diversity by means of rarefied species richness, abundances, evenness and Simpson's diversity. We found contrasting relationships in that most species diversity measures peaked at highest disturbance levels, while most functional diversity measures decreased with increasing disturbance intensities. Inversed relationships between species and functional diversity are rarely observed, as most studies report on positive correlations. We explain increasing species diversity with a higher amount of resources available in highly disturbed sites. Decreasing functional diversity is best explained through the convergence of species traits by flood disturbance and uneven resource exploitation in highly disturbed plots (low functional evenness), suggesting strong impacts from functionally different generalist species in floodchannels. We show that the amount of resources available, and how these resources are exploited, play major roles in the functioning of floodplain ground beetle communities.

Taxonomic diversity considers all species being equally different from each other and thus disregards species' different ecological functions. Exploring taxonomic and functional aspects of biodiversity simultaneously can better understand the processes of community assembly. We analysed taxonomic and functional alpha and beta diversities of breeding bird assemblages on land-bridge islands in the Thousand Island Lake, China. Given the high dispersal ability of most birds at this spatial scale (several kilometres), we predicted (i) selective extinction driving alpha and beta diversities after the creation of land-bridge islands of varying area and (ii) low taxonomic and functional beta diversities that were not correlated to spatial distance. Breeding birds were surveyed on 37 islands annually from 2007 to 2014. We decomposed beta diversity of breeding birds into spatial turnover and nestedness-resultant components, and related taxonomic and functional diversities to island area and isolation using power regression models (for alpha diversity) and multiple regression models on distance matrices (for beta diversity). We then ran simulations to assess the strength of the correlations between taxonomic and functional diversities. Results revealed that both taxonomic and functional alpha diversities increased with island area. The taxonomic nestedness-resultant and turnover components increased and decreased with difference in area, respectively, but functional counterparts did not. Isolation played a minor role in explaining alpha- and beta-diversity patterns. By partitioning beta diversity, we found low levels of overall taxonomic and functional beta diversities. The functional nestedness-resultant component dominated overall functional beta diversity, whereas taxonomic turnover was the dominant component for taxonomic beta diversity. The simulation showed that functional alpha and beta diversities were significantly correlated with taxonomic diversities, and the observed values of correlations were significantly different from null expectations of random extinction. Our assessment of island bird assemblages validated the predictions of no distance effects and low beta diversity due to pervasive dispersal events among islands and also suggested that selective extinction drives taxonomic and functional alpha and beta diversities. The contrasting turnover and nestedness-resultant components of taxonomic and functional beta diversities demonstrate the importance of considering the multifaceted nature of biodiversity when examining community assembly.

Do species and functional trait diversity respond similarly to deterministic and random processes? Theory predicts that the contributions of random and deterministic processes to species diversity depend on patch size. Smaller patches are more strongly influenced by random sampling effects, by having fewer individuals, as well as ecological drift, which propagates the effects of small samples through stochastic birth and death processes. These random processes decrease species richness and increase compositional differences among small patches. Larger patches are predicted to be more deterministically assembled, with greater species richness and greater predictability of composition for a particular environment. The consequences of patch size for the diversity of functional traits, however, are poorly understood. Species diversity may be a poor proxy for functional diversity due to trait redundancies among species, making it unclear how random and deterministic processes alter functional diversity within patches of differing size, and how these differences scale up to determine among‐patch functional diversity. We report a novel experimental study of species and functional diversity across spatial scales. We manipulated patch area in an experimental plant metacommunity and used a nested sampling design to distinguish the effects of deterministic processes, ecological drift and sampling effects on species and functional trait diversity. Our study revealed a pervasive influence of ecological drift and sampling effects on diversity, with distinct influences on functional traits and species composition within and among patches. Overall, drift and sampling effects caused a two‐ to threefold decrease in the importance of deterministic processes in small fragments. Species and functional diversity showed similar patterns with patch size; larger patches had greater within‐patch (alpha) diversity and lower among‐patch (beta) diversity, consistent with theory. However, our nested sampling design revealed that sampling effects (i.e. the size of the sample area) largely determined alpha species diversity and beta functional diversity, while ecological drift had a stronger influence on alpha functional diversity and beta species diversity. Synthesis. The compositions of species and functional diversity in a community are influenced by distinct processes, resulting in divergent spatial scaling of species and their traits within patches and across landscapes.

Understanding disturbance effects on species diversity and functional diversity is fundamental to conservation planning but remains elusive. We quantified species richness, diversity, and evenness and functional richness, diversity, and evenness of riparian and upland plants along 24 small streams subjected to a range of anthropogenic disturbances in the boreal forest of northwestern Ontario, Canada. We included a total of 36 functional traits related to productivity, competitive ability, reproduction, disturbance tolerance, life history, and tolerance to habitat instability. Using nested ANOVA, we examined the response of diversity indices to disturbance and whether it followed the intermediate disturbance hypothesis (IDH) and varied with habitat stability. We found that, like species richness and diversity, functional richness and diversity reached peaks at moderate disturbance intensity; functional diversity followed the predictions of the IDH. Second, disturbance-habitat-stability coupling has very little effect on overall species and functional diversity, but the effect on particular life forms and functions may be significant. Since species richness and diversity patterns are context and system dependent, our findings should be most applicable to similar temperate riparian systems.

BackgroundThe ‘classical’ concept of species diversity was extended in the last decades into other dimensions focusing on the functional and phylogenetic diversity of communities. These measures are often argued to allow a deeper understanding of the mechanisms shaping community assembly along environmental gradients. Because of practical impediments, thus far only very few studies evaluated the performance of these diversity measures on large empirical data sets. Here, data on species-rich riparian moth communities under different flood regimes and from three different rivers has been used to compare the power of various diversity measures to uncover ecological contrasts.ResultsContrary to the expectation, classical metrics of species diversity (Hill numbers N1, N2 and Ninf) and evenness (Buzas-Gibson’s E and Pielous’s J) turned out to be the most powerful measures in unravelling the two gradients investigated in this study (e.g. flood regime and region). Several measures of functional and phylogenetic diversity tended to depict either only one or none of these contrasts. Rao’s Q behaved similarly as species diversity and evenness. NTI and NRI showed a similar pattern among each other but, were different to all the other measures. Functional Divergence also behaved idiosyncratically across the 28 moth communities. The community weighted means of nearly all individual functional traits showed significant ecological patterns, supporting the relevance of the selected traits in shaping assemblage compositions.ConclusionsSpecies diversity and evenness measures turned out to be the most powerful metrics and clearly reflected both investigated environmental contrasts. This poses the question when it is useful to compile the additional data necessary for the calculation of additional diversity measures, since assembling trait bases and community phylogenies often requires a high work load. Apart from these methodological issues, most of the diversity measures related to communities of terrestrial insects like moths increased in forests that still are subject to flooding dynamics. This emphasizes the high conservation value of riparian forests and the importance of keeping and restoring river dynamics as a means of fostering also terrestrial biodiversity in floodplain areas.

Plant biodiversity is often partitioned into taxonomic diversity (species composition and abundance), phylogenetic diversity (breadth of evolutionary lineages) and functional diversity (resource‐use strategies or physical traits). Evaluating the effects and interplay of these dimensions can provide insights into how assembly processes drive compositional changes in plant communities. However, teasing apart the effects of different biodiversity dimensions is challenging in observational studies or retrospective analyses. To evaluate how plant phylogenetic and trait history shape community establishment and turnover in restoration of a species‐rich North American tallgrass prairie, we conducted an experiment with 127 species planted in assemblages representing three levels of phylogenetic diversity (PD) and two of functional trait diversity (FD), holding starting species richness (SR) fixed. We tested whether PD and FD of planted assemblages predicted species diversity, compositional turnover and selection on functional traits. Rank order of initial functional and phylogenetic diversity levels was maintained throughout the experiment, but neither diversity measure correlated positively with species richness by the end of the experiment. Phylogenetic and taxonomic beta diversity increased among all treatments. This increase in compositional beta diversity was associated with directional selection on phylogenetically dispersed functional traits. A set of functional traits associated with competitiveness in tallgrass prairies predicted species' cover for all survey years: stem dry matter content, leaf dry matter content, vegetative height and rhizomatous growth. Although all plots collectively converged on a similar suite of functional traits, functional beta diversity increased among high‐FD plots. Synthesis. Neither higher functional nor phylogenetic diversity maintained higher species richness (SR) over time in our study. Although SR was not maintained, higher levels of PD and FD were. Both types of diversity shaped the rate at which plots changed in composition over time, with high diversity treatment plots increasing in beta diversity. Selection for traits convergent across the tree of life drove phylogenetic and compositional divergence among plots. While optimization of site‐specific functional traits may be most important for maintaining higher SR, our work implies that planting higher initial PD and FD may make grassland restorations more adaptable to site conditions that may be difficult to predict.

Pesticides and land cover heterogeneity affect functional group and taxonomic diversity of arthropods in rice agroecosystems

PDF HTML阅读 XML下载 导出引用 引用提醒 江西柘林水库鱼类群落结构及功能多样性分析 DOI: 10.5846/stxb202106031466 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2019YFD0900603）；财政部和农业农村部：国家现代农业产业技术体系资助（CARS-46）；中国水产科学研究院基本科研业务费院级湖库增殖渔业创新团队项目（2020TD57） Community structure and functional diversity of fishes in Zhelin Reservoir, Jiangxi Province Author: Affiliation: Fund Project: National Key Research and Development Program of China (No.No.2019YFD0900603); Supported by China Agriculture Research System of MOF and MARA（CARS-46）; Central Public-interest Scientific Institution Basal Research Fund，CAFS (NO.2020TD57) 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:为了解江西柘林水库鱼类群落结构和多样性的时空变化特征，研究鱼类物种多样性和功能多样性的关系，于2020年9月至2021年4月在该水库调查分析了鱼类物种组成、优势度及群落物种多样性和功能多样性。结果表明，共采集鱼类53种，分属于5目12科36属。其中，鲤形目（38种）种类最多，占调查物种数的71.69%，柘林水库上、中、下游库区分别采集到鱼类36、40和32种，各库区均以鲤形目鱼类为主，分别占采集物种数的72.97%、85.00%和75.00%。优势物种主要是䱗（Hemiculter leucisculus）、鳙（Aristichthys nobilis）和黄尾鲴（Xenocypris davidi），重要种主要是草鱼（Ctenopharyngodon idella）、鲢（Hypophthalmichthys molitrix）、鳊（Parabramis pekinensis）、鲫（Carassius auratus）、蒙古红鲌（Erythroculter mongolicus）等。鱼类群落结构季节性差异大于空间格局差异，主要表现为秋季和冬季之间；生物多样性指数Margalef和功能丰富度指数在上游修河水域相对较高，鱼类物种多样性和功能多样性空间格局差异性大于时间尺度下的差异性。物种多样性与功能多样性的回归分析结果显示，功能丰富度与物种多样性指数之间存在显著的正相关关系；功能冗余度与各物种多样性之间呈现负相关关系，说明物种数的增加导致了库区鱼类功能丰富度的增加和功能冗余度的降低，而功能均匀度未发生明显的变化，主要原因为调查区域内拥有不同功能性状的鱼类群体之间在个体数比例上呈现不均匀分布的模式，这一结果预示着拥有较多物种的群落生态位重叠度相对较低，生态系统受干扰后的恢复能力较差。总体而言，保护鱼类生物多样性和维护生态系统的稳定性应该通过调控鱼类种群结构达到提高鱼类群落冗余度以及资源和生境可用性的目的。 Abstract:To understand the spatial and temporal variation of fish assemblage structure and biodiversity, as well the relationships between fish taxonomical diversity and functional diversity, species compositions, the dominant species, taxonomical and functional diversity of fish communities which were captured from Zhelin Reservoir from September 2020 to April 2021 were investigated and analyzed. The results showed that a total of 53 fish species belonging to 5 orders, 12 families, and 36 genera were sampled with dominant Cyprinidae accounting for 71.69% of the total species. Among the reservoir spatial scales, 36, 40 and 32 fish species which accounting for 72.97%, 85.00% and 75.00% of the total sampled species were captured from upper-, middle- and low-reach, respectively. Hemiculter leucisculus, Aristichthys Nobilis and Xenocypris davidi were dominant species, while Ctenopharyngodon idella, Hypophthalmichthys molitrix, Parabramis pekinensis, Carassius auratus and Erythroculter mongolicus were main species in Zhelin Reservoir. The analysis of PERMANOVA (Permutational Multivariate Analysis of Variance) using the fish assemblage matrixes showed that the seasonal variation of species compositions was more significant than the spatial scale, and the variations were mainly performed between two seasons of antum and summer. Meanwhile, biodiversity indexes and functional diversity indexes of fish assembalges performed relative higher variations among spatial scales than temporal scales. Margalef index were relatively higher in the Xiuhe River than those in other water sites, while the indexes of Shannon, Simpson and Peilou indexes showed no variation among the reaches. Functional richness possessed relative higher level in upper reach than midlle and lower reaches, while functional evenness and functional disperse performed non changes among spatial scales. Functional redundancy had no variation among spatial and temporal scales. Regression analyses showed significant positive relationships between the biodiversity index of functional richenss and functional disperse with each taxonomical diversity index, while there were negative relationships between functional redundancy and taxonomical diversity indexes, which implying the increase of species richness led to the increase of the functional richness and decrease of functional redundancy. However, functional evenness did not change obviously which can mainly be explained by the disproportionate individuals of different fish functional groups. The results implied that interference resulted in a lower niche overlap of fish community with high species richness and lower ecosystem recovery ability. In general, the species diversity level of Zhelin Reservoir is lower and the anti-interference ability of this ecosystem is relatively weaker. To protect fish biodiversity and maintain the stability of the ecosystem, it is necessary to improve the fish community redundancy and the availability of resources and habitats by regulating the fish population structure. 参考文献 相似文献 引证文献

Most island-ecology studies focus on the properties of entire island communities, thus neglecting species-environment relationships operating at the habitat-level. Habitat-specific variation in the strength and sign of these relationships will conceal patterns observed on the island scale and may preclude a mechanistic interpretation of patterns and processes. Habitat-specific species-environment relationships may also depend on the descriptor of ecological communities. This paper presents a comprehensive plot-based analysis of local vegetation composition and species diversity (species richness and species evenness) of (i) rocky shore, (ii) semi-natural grassland and (iii) coniferous forest habitats in three Baltic archipelagos in Sweden. To identify differences and consistencies between habitats and descriptors, we assessed the relative contributions of the variable-sets “region”, “topography”, “soil morphology”, “soil fertility”, “soil water”, “light availability”, “distance” and “island configuration” on local vegetation composition, species richness and species evenness. We quantified the impact of “management history” on the descriptors of local grassland communities by a newly introduced grazing history index (GHI). Unlike species diversity, changes in vegetation composition were related to most of the variable-sets. The relative contributions of the variable-sets were mostly habitat-specific and strongly contingent on the descriptor involved. Within each habitat, richness and evenness were only partly affected by the same variable-sets, and if so, their relative contribution varied between diversity proxies. Across all habitats, soil variable-sets showed highly consistent effects on vegetation composition and species diversity and contributed most to the variance explained. GHI was a powerful predictor, explaining high proportions of variation in all three descriptors of grassland species communities. The proportion of unexplained variance was habitat-specific, possibly reflecting a community maturity gradient. Our results reveal that species richness alone is an incomplete representation of local species diversity. Finally, we stress the need of including habitat-based approaches when analyzing complex species-environment relationships on islands.

Precipitation changes have significant impacts on biodiversity and ecosystem productivity. However, the effects of precipitation changes on species diversity have been the focus of most previous studies. Little is known about the contributions of different dimensions of biodiversity (species, functional, and phylogenetic diversity) in linking long-term precipitation changes to ecosystem functions. In this study, a randomized design was conducted in the desert steppes of Ningxia, which included three treatments: natural rainfall, precipitation reduced by 50%, and precipitation increased by 50%. After 4 years of treatment, the effects of precipitation changes on aboveground productivity and its underlying mechanisms were explored. The results showed that (1) reduced precipitation significantly decreased phylogenetic diversity and species diversity, but had no significant effect on functional diversity; (2) reduced precipitation significantly decreased aboveground productivity, while increased precipitation significantly enhanced aboveground productivity; and (3) changes in precipitation primarily regulated aboveground productivity by altering soil nitrogen availability and the size of dominant plant species. This study provides important theoretical and practical guidance for the protection and management of desert steppe vegetation under future climate change.