Biodiversity Effects on Biomass Production and Invasion Resistance in Annual versus Perennial Plant Communities

In a field experiment we constructed two different communities using both annual and perennial plant species, in which species diversity is experimentally manipulated. We want to test the relationships between species diversity and biomass production and invasibility and the possible mechanisms driving this relationships, especially, whether the identical mechanisms drive both diversity-production and diversity-invasibility relationships. Our results indicated that a positive diversity-production relationship and negative diversity-invasibility and production-invasibility relationships emerged in two different communities. However, the mechanisms underlying are different in two communities. In the annual communities, the observed positive diversity-production and negative diversity-invasibility relationships are linked by the sampling effect. In the perennial communities, however, the mechanism responsible for these observed relationships are the complementarity effect. Our results also found that, in addition to species diversity, species composition also play an important role in governing the observed relationship. The results of our study suggest that because species in different communities may differ in their life history, biological and physiological traits, mechanisms responsible for the observed relationship between diversity and biomass production and invasibiltiy are likely different.     

Plant diversity controls arthropod biomass and temporal stability

Understanding the linkages among species diversity, biomass production and stability underlies effective predictions for conservation, agriculture and fisheries. Although these relationships have been well studied for plants and, to a lesser extent, consumers, relationships among plant and consumer diversity, productivity, and temporal stability remain relatively unexplored. We used structural equation models to examine these relationships in a long‐term experiment manipulating plant diversity and enumerating the arthropod community response. We found remarkably similar strength and direction of interrelationships among diversity, productivity and temporal stability of consumers and plants. Further, our results suggest that the frequently observed relationships between plant and consumer diversity occur primarily via changes in plant production leading to changed consumer production rather than via plant diversity directly controlling consumer diversity. Our results demonstrate that extinction or invasion of plant species can resonate via biomass and energy flux to control diversity, production and stability of both plant and consumer communities.     

Functional group richness: implications of biodiversity for light use and lipid yield in microalgae

Currently, very few studies address the relationship between diversity and biomass/lipid production in primary producer communities for biofuel production. Basic studies on the growth of microalgal communities, however, provide evidence of a positive relationship between diversity and biomass production. Recent studies have also shown that positive diversity–productivity relationships are related to an increase in the efficiency of light use by diverse microalgal communities. Here, we hypothesize that there is a relationship between diversity, light use, and microalgal lipid production in phytoplankton communities. Microalgae from all major freshwater algal groups were cultivated in treatments that differed in species richness and functional group richness. Polycultures with high functional group richness showed more efficient light use and higher algal lipid content with increasing species richness. There was a clear correlation between light use and lipid production in functionally diverse communities. Hence, a powerful and cost‐effective way to improve biofuel production might be accomplished by incorporating diversity related, resource‐use‐dynamics into algal biomass production.     

Biomass-dependent susceptibility to drought in experimental grassland communities

Earlier studies indicated that plant diversity influences community resistance in biomass when ecosystems are exposed to perturbations. This relationship remains controversial, however. Here we constructed grassland communities to test the relationships between species diversity and productivity under control and experimental drought conditions. Species richness was not correlated with biomass either under constant conditions or under drought conditions. However, communities with lower biomass production were more resistant to drought stress than those that were more productive. Our results also showed that ecosystem resistance to drought is a decreasing but nonlinear function of biomass. In contrast, species diversity had little and an equivocal effect on ecosystem resistance. From the results reported here, and the results of several previous studies, we suggest that high biomass systems exhibited a greater biomass reduction in response to drought than low biomass systems did, regardless of the relationship between plant diversity and community biomass production.     

Insects affect relationships between plant species richness and ecosystem processes

This study examined whether insects can alter relationships between plant species diversity and ecosystem function in grassland communities, by (i) altering biomass across a plant diversity gradient, (ii) altering relative abundances of plant species, or (iii) altering ecosystem function directly. We measured herbivore damage on seminatural grassland plots planted with 1, 2, 4, 8, or 12 plant species, and compared plant biomass in a subset of these plots with replicates in which insect levels were reduced. Plant biomass and herbivore damage increased with species richness. Reducing insect populations resulted in greater evenness of relative plant species abundances and revealed a strong positive relationship between plant species richness and above-ground biomass. Reducing insects also changed the relationship between plant species richness and decomposition. Plant species mixtures and their relative abundances partially explained plant biomass results, but not decomposition results. These results suggest that insects can alter relationships between plant diversity and ecosystem processes through all three mechanisms.     

阿尔泰山两河源牧区草地群落生物量及物种多样性

群落生物量和物种多样性是表征草地生态系统数量特征的重要指标。该研究以新疆阿尔泰山南麓两河源放牧区草地为研究对象,利用样方法对两河源不同放牧区的草地植被进行调查,分析研究区生物量和物种多样性变化,探讨二者与环境因子之间的关联性,为草地群落物种保护以及草地可持续利用提供理论依据。结果表明：(1) 两河源不同牧区间群落盖度、高度、植株密度、地上生物量和单位盖度生物量存在差异。(2) 两河源牧区草地群落地上生物量与群落盖度、植株密度呈显著正相关关系(P<0.05),且地上生物量主要受草地群落盖度的影响;不同牧区的物种多样性指数有一定差异,但物种分布相对均匀。(3)两河源牧区草地群落生物量及物种多样性主要受气温和降水的影响。     

三江源地区不同建植期人工草地植被特征及其与土壤特征的关系

研究了三江源地区不同建植期人工草地群落生物量、物种组成、多样性指数和土壤理化特征,并用多元逐步回归分析法探讨了土壤理化特征对群落生物量、多样性变化的响应.结果表明:研究区不同建植期人工草地植物群落的种类组成、植物功能群组成和群落数量特征存在显著差异;土壤含水量随着物种多样性指数的增加而增加,土壤容重随着物种多样性的增加而减小;土壤微生物生物量碳与土壤含水量、土壤有机质呈极显著正相关,与土壤容重呈极显著负相关;土壤有机碳含量明显呈"V"字型变化,且与土壤含水量的变化趋势相一致,随土壤容重的增加而减少;群落生物量与土壤养分和土壤含水量之间呈显著正相关,群落地上、地下生物量的增加有利于提高土壤养分含量.     

Recovery in Diversity of Fish and Invertebrate Communities Following Remediation of a Polluted Stream: Investigating Causal Relationships

Spatial and temporal responses of biota to anthropogenic disturbance were measured over a 15 year period in a contaminated stream undergoing remediation and recovery. Along the spatial gradient of the stream, levels of contaminants decreased downstream along with improved responses of instream biota at several levels of biological organization. Recovery of the biota in this stream over the 15 year study period is demonstrated by the temporal relationships between levels of decreasing contaminants and the concomitant responses of the periphyton, macroinvertebrate, and fish communities and changes in the various bioindicators of individual fish health. Decreases in contaminants over a temporal scale were followed closely by an improvement in physiological and organismal-level indicators, increases in the diversity of macroinvertebrate and fish communities, and rapid increases in the chlorophyll a biomass and photosynthesis rate of the periphyton community. These results emphasize that field studies designed to assess and evaluate the effectiveness of restoration activities on stream recovery should incorporate a variety of response endpoints ranging from sensitive and short-term responses to long-term but ecological relevant indicators of change. The close spatial and temporal relationships observed between changes in physicochemical factors and positive responses in various components of the stream biota over the 15-year study period suggest a strong cause and effect relationship between remediation activities and stream recovery. Understanding causal relationships and the mechanistic processes between environmental stressors, stress responses of biota, and the recovery process is important in the effective management and restoration of aquatic ecosystems. An erratum to this article is available at .     

取样尺度对亚高寒草甸物种多样性与生产力关系的影响

植物物种多样性与生产力之间的关系是群落生态学的一个热点问题, 目前仍存在着很多争议。为探究自然群落中二者之间的关系, 对青藏高原亚高寒草甸3个样地的自然植物群落分别进行了不同取样面积的抽样调查。结果显示, 取样样地和取样尺度均对物种丰富度有显著影响, 取样样地而非取样尺度对群落地上生物量有显著性影响。在某一时刻对某一样地进行取样, 其单位面积生产力并不因取样面积的增加而提高, 而是保持恒定的, 尽管物种数随取样面积的增加而有明显增多。物种多样性与生产力之间的回归关系因样地与取样尺度不同而不同, 有U型、单峰型、正线性相关和无相关性, 其中无相关性出现的最多。据此推测, 亚高寒草甸群落物种多样性与生产力之间不存在某种确定性关系, 或者说, 亚高寒草甸物种多样性和生产力之间不存在必然的因果联系。     

Positive effects of plant diversity on soil microbial biomass and activity are associated with more root biomass production

This study aims to explore relationships between plant diversity and soil microbial function and the factors that mediate the relationships. Artificial plant communities (1, 2, 4 and 8 species) were established filled with natural and mine tailing soils, respectively. After 12 months, the plant species richness positively affected the soil microbial functional diversity in both soil environments but negatively affected microbial biomass and soil basal respiration in the natural soil. The root biomass positively correlated with the microbial biomass, cultural bacterial activity and soil basal respiration in both soil environments. Moreover, the D_i (deviations between observed performances and expected performances from the monoculture performance of each species of mixture) of microbial biomass, cultural bacterial activity and soil basal respiration positively correlated with the D_i of root biomass in both soil environments. Consistent with stress-gradient hypothesis, the D_mix (over-function index) of aboveground biomass positively correlated plant species richness in the mine tailing soil. Results suggest that the root biomass production is an important mechanism that affects the effects of plant diversity on soil microbial functions. Different responses of soil microbial function to increasing plant diversity may be due to root biomass production mediated by other factors.     

Effect of a temperature gradient on Sphagnum fallax and its associated living microbial communities: a study under controlled conditions

Microbial communities living in Sphagnum are known to constitute early indicators of ecosystem disturbances, but little is known about their response (including their trophic relationships) to climate change. A microcosm experiment was designed to test the effects of a temperature gradient (15, 20, and 25°C) on microbial communities including different trophic groups (primary producers, decomposers, and unicellular predators) in Sphagnum segments (0-3 cm and 3-6 cm of the capitulum). Relationships between microbial communities and abiotic factors (pH, conductivity, temperature, and polyphenols) were also studied. The density and the biomass of testate amoebae in Sphagnum upper segments increased and their community structure changed in heated treatments. The biomass of testate amoebae was linked to the biomass of bacteria and to the total biomass of other groups added and, thus, suggests that indirect effects on the food web structure occurred. Redundancy analysis revealed that microbial assemblages differed strongly in Sphagnum upper segments along a temperature gradient in relation to abiotic factors. The sensitivity of these assemblages made them interesting indicators of climate change. Phenolic compounds represented an important explicative factor in microbial assemblages and outlined the potential direct and (or) indirect effects of phenolics on microbial communities.     

Above-ground biomass and species richness in a Mediterranean salt marsh

Abstract. Species composition, above-ground biomass and diversity of herbaceous communities were recorded in 50 sites on the upper salt marsh of the Guadalquivir delta (SW Spain). Through Canonical Correspondence Analysis relationships were shown between plant-species characteristics abundance and environmental variables. Seven community types were distinguished and related to hydro logical regime and physical and chemical soil parameters. The higher species richness was associated with moderate values of above-ground biomass (Biomass at maximum diversity, BMD = 302 g/m²). Salinity was negatively correlated with species richness. There was no significant correlation with total above-ground biomass. Water regime and soil nutrient (Ca, Mg) content were significant predictors of the community above-ground biomass.     

Biodiversity maintenance mechanisms differ between native and novel exotic-dominated communities

In many systems, native communities are being replaced by novel exotic-dominated ones. We experimentally compared species diversity decline between nine-species grassland communities under field conditions to test whether diversity maintenance mechanisms differed between communities containing all exotic or all native species using a pool of 40 species. Aboveground biomass was greater in exotic than native plots, and this difference was larger in mixtures than in monocultures. Species diversity declined more in exotic than native communities and declines were explained by different mechanisms. In exotic communities, overyielding species had high biomass in monoculture and diversity declined linearly as this selection effect increased. In native communities, however, overyielding species had low biomass in monoculture and there was no relationship between the selection effect and diversity decline. This suggests that, for this system, yielding behaviour is fundamentally different between presumably co-evolved natives and coevolutionarily naive exotic species, and that native-exotic status is important to consider.     

A cross‐system meta‐analysis reveals coupled predation effects on prey biomass and diversity

Predator diversity and abundance are under strong human pressure in all types of ecosystems. Whereas predator potentially control standing biomass and species interactions in food webs, their effects on prey biomass and especially prey biodiversity have not yet been systematically quantified. Here, we test the effects of predation in a cross‐system meta‐analysis of prey diversity and biomass responses to local manipulation of predator presence. We found 291 predator removal experiments from 87 studies assessing both diversity and biomass responses. Across ecosystem types, predator presence significantly decreased both biomass and diversity of prey across ecosystems. Predation effects were highly similar between ecosystem types, whereas previous studies had shown that herbivory or decomposition effects differed fundamentally between terrestrial and aquatic systems based on different stoichiometry of plant material. Such stoichiometric differences between systems are unlikely for carnivorous predators, where effect sizes on species richness strongly correlated to effect sizes on biomass. However, the negative predation effect on prey biomass was ameliorated significantly with increasing prey richness and increasing species richness of the manipulated predator assemblage. Moreover, with increasing richness of the predator assemblage present, the overall negative effects of predation on prey richness switched to positive effects. Our meta‐analysis revealed strong general relationships between predator diversity, prey diversity and the interaction strength between trophic levels in terms of biomass. This study indicates that anthropogenic changes in predator abundance and diversity will potentially have strong effects on trophic interactions across ecosystems. Synthesis The past centuries we have experienced a dramatic loss of top–predator abundance and diversity in most types of ecosystems. To understand the direct consequences of predator loss on a global scale, we quantitatively summarized experiments testing predation effects on prey communities in a cross‐system meta‐analysis. Across ecosystem types, predator presence significantly decreased both biomass and diversity of prey, and predation effects were highly similar. However, with increasing predator richness, the overall negative effects of predation on prey richness switched to positive ones. Anthropogenic changes in predator communities will potentially have strong effects on prey diversity, biomass, and trophic interactions across ecosystems.     

西南干旱河谷植物群落组分生物量的纬度格局及其影响因素

研究植物群落不同组分生物量的纬度格局及其与生物、非生物因子的定量关系有助于揭示植物对环境的适应性, 能够解释生态系统结构和功能的空间差异性及其成因。该研究在西南干旱河谷跨越9个纬度(23.23°-32.26° N), 布置101个群落 样方(4 m × 6 m)。采用收割法测定群落及组分生物量, 分析生物量在纬度梯度上的变化规律及其影响因子。结果显示, 干旱河谷群落平均生物量为(17.05 ± 1.09) t·hm^-2, 其中, 灌木平均生物量为(11.51 ± 1.03) t·hm^-2, 占60.2%; 草本平均生物量为(2.11 ± 0.21) t·hm^-2, 占15.6%; 凋落物平均生物量为(3.41 ± 0.34) t·hm^-2, 占24.1%。群落生物量和灌木生物量随纬度升高而显著增加, 草本生物量随纬度升高无明显变化, 凋落物生物量随纬度的升高而显著降低。随着纬度增加, 灌木生物量的比例明显增大, 草本生物量的比例无明显变化, 凋落物生物量的比例明显降低。灌木优势度及丰富度的变化是驱动干旱河谷植被生物量在纬度梯度上变化的主要内在因子, 而外在因子中, 气候因子对群落及组分生物量的影响显著高于土壤因子｡     

古尔班通古特沙漠南缘地表甲虫物种多样性及其与环境的关系

为了解荒漠地表甲虫的多样性特点及其与环境的关系,明确其环境指示作用,评估沙漠工程对荒漠地表甲虫多样性的影响,作者于2010年5-7月采用陷阱法调查了占尔班通古特沙漠南缘从沙漠腹地到沙漠绿洲交错区不同生境的地表甲虫物种多样性,其中包括沙漠腹地公路防护体系的干扰生境.结果如下:(1)共捕获地表甲虫54,527头,隶属于14...     

Reconsidering diversity–productivity relationships: directness of productivity estimates matters

Despite extensive research efforts, the controversy over diversity–productivity (D–P) patterns in natural communities still looms large. Recent meta‐analyses suggest that unimodal D–P relationships tend to pre‐dominate in plant studies, while positively linear relationships are more common in animal studies. These patterns, however, are based on studies in which productivity is estimated either directly, based on the biomass or energy of the studied organisms, or indirectly, according to the productivity of lower trophic levels, and various surrogates. Our analysis shows that the distribution of D–P patterns is sensitive to the directness of productivity estimates in animal studies but not in plant studies. Analysis of D–P patterns should be based on direct productivity estimates of the studied organisms, especially in comparative meta‐analyses of communities from multiple trophic levels, where productivity is often affected nonlinearly by indirect factors or when complex feedback interactions are expected between productivity and diversity.     

Ecosystem Functions across Trophic Levels Are Linked to Functional and Phylogenetic Diversity

In experimental systems, it has been shown that biodiversity indices based on traits or phylogeny can outperform species richness as predictors of plant ecosystem function. However, it is unclear whether this pattern extends to the function of food webs in natural ecosystems. Here we tested whether zooplankton functional and phylogenetic diversity explains the functioning of 23 natural pond communities. We used two measures of ecosystem function: (1) zooplankton community biomass and (2) phytoplankton abundance (Chl a). We tested for diversity-ecosystem function relationships within and across trophic levels. We found a strong correlation between zooplankton diversity and ecosystem function, whereas local environmental conditions were less important. Further, the positive diversity-ecosystem function relationships were more pronounced for measures of functional and phylogenetic diversity than for species richness. Zooplankton and phytoplankton biomass were best predicted by different indices, suggesting that the two functions are dependent upon different aspects of diversity. Zooplankton community biomass was best predicted by zooplankton trait-based functional richness, while phytoplankton abundance was best predicted by zooplankton phylogenetic diversity. Our results suggest that the positive relationship between diversity and ecosystem function can extend across trophic levels in natural environments, and that greater insight into variation in ecosystem function can be gained by combining functional and phylogenetic diversity measures.     

Bacterial diversity promotes community stability and functional resilience after perturbation

The relationships between bacterial community diversity and stability were investigated by perturbing soils, with naturally differing levels of diversity, to equivalent toxicity using copper sulfate and benzene. Benzene amendment led to large decreases in total bacterial numbers and biomass in both soils. Benzene amendment of an organo-mineral/improved pasture soil altered total soil bacterial community structure but, unlike amendment of the mineral/arable soil, maintained genetic diversity, based on polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis targeting DNA and RNA, until week 9 of the perturbation experiment. Assuming equivalent toxicity, the genetic diversity of the naturally more diverse soil was more resistant to benzene perturbation than the less diverse soil. The broad scale function (mineralization of 14C-labelled wheat shoot) of both benzene- and copper-treated soil communities was unaffected. However, narrow niche function (mineralization of 14C-labelled 2,4-dichlorophenol) was impaired for both benzene-polluted soils. The organo-mineral soil recovered this function by the end of the experiment but the mineral soil did not, suggesting greater resilience in the more diverse soil. Despite a large reduction in bacterial numbers and biomass in the copper-treated soils, only small differences in bacterial community diversity were observed by week 9 in the copper-polluted soils. The overall community structure was little altered and functionality, measured by mineralization rates, remained unchanged. This suggested a non-selective pressure and a degree of genetic and functional resistance to copper perturbation, despite a significant reduction in bacterial numbers and biomass. However, initial shifts in physiological profiles of both copper-polluted soils were observed but rapidly returned to those of the controls. This apparent functional recovery, accompanied by an increase in culturability, possibly reflects adaptation by the surviving communities to perturbation. The findings indicate that, although soil communities may be robust, relationships between diversity and stability need to be considered in developing a predictive understanding of response to environmental perturbations.     

The relationship of diversity and biomass in phytoplankton communities weakens when accounting for species proportions

The relationship between productivity (or biomass) and species diversity in ecological communities remains a hotly debated topic. While much is already known about vascular plants, little is known in other types of organisms. We used a broad and standardized database of phytoplankton samples from the Czech Republic, containing 413 samples of various types of stagnant waters to evaluate this relationship. Biomass was characterized by the total biovolume/ml, the total number of individuals/ml and cells/ml all giving similar results. All these indicators spanned over five orders of magnitude while the number of species ranged between 1 and 57. Diversity was characterized by indices of Hill’s unified notation series progressively accounting for species proportion effects. The number of species showed an asymmetric unimodal relationship with biomass. The relationship weakened when considering diversity indices including species proportions. At very low productivity values (characterized by low biomass), diversity was probably restricted by the ability of algae and cyanobacteria to survive a lack of nutrients, in high productivities, by the competition for light. Medium productivities, where maximum diversity was found, exhibited large variability of diversity values (including very low ones), suggesting that low diversity of phytoplankton samples can be caused by multitude of factors.