物种多样性与生态系统功能时间变异性的关系研究进展

近年来物种多样性的急剧丧失使得物种多样性与生态系统功能的时间变异性的关系及其机制问题的研究成为了生态学研究的一个热点。综述了物种多样性与群落集合性质变异性以及种群性质变异性的关系及其机制的最新研究成果：1、理论上探讨造成物种多样性与群落集合性质变异性负相关关系的机制包括：抽样效应、资源利用分化假说、统计平均效应、保险假说、种群变异性的均匀度效应等;但实验研究对理论预期的支持并不是普遍的;2．多样性与种群变异性之间的关系主要依赖于均值-方差尺度系数Z;理论上大部分自然群落是种群变异性应该随着多样性的增加而增加;但有研究表明：在变动环境中多样性对单个组分物种的种群水平有稳定性作用;而经验研究并不能得出多样性对种群变异性效应的清晰模式。讨论了目前的理论和实验研究中存在的和今后研究中需要认真思考的问题。     

Herbivorous animals can mitigate unfavourable ratios of energy and material supplies by enhancing nutrient recycling

Recent evidence shows that high supply ratios of light and nutrients limit planktonic herbivore growth by lowering the nutritional quality of algae. Over longer time scales, however, grazers may ameliorate this effect by their impact on nutrient cycling. We examine this possibility using two species of the herbivorous zooplankter Daphnia and its algal prey under different light intensities and low phosphorus supply in laboratory microcosms. At high light, Daphnia biomass was limited for a substantial period because of low P content of algal cells. However, a gradual increase in Daphnia density eventually improved food quality through grazing and nutrient cycling and via a novel process involving positive density dependence. Competitive exclusion of one of the two Daphnia species occurred under low light but not under high light when algae were nutritionally unsuitable. Such stoichiometrically mediated interactions among herbivorous animals may represent important mechanisms that affect community structure and material flows in ecosystems.     

Effects of nutrient recycling by zooplankton and fish on phytoplankton communities

In laboratory experiments we tested the hypothesis that nutrients supplied by fish and zooplankton affect the structure and dynamics of phytoplankton communities. As expected from their body size differences, fish released nutrients at lower mass-specific rates than Daphnia. On average, these consumers released nutrients at similar N:P ratios, although the ratios released by Daphnia were more variable than those released by fish. Nutrient supply by both fish and Daphnia reduced species richness and diversity of phytoplankton communities and increased algal biomass and dominance. However, nutrient recycling by fish supported a more diverse phytoplankton community than nutrient recycling by Daphnia. We conclude that nutrient recycling by zooplankton and fish have different effects on phytoplankton community structure due to differences in the quality of nutrients released. Received: 21 December 1998 / Accepted: 31 May 1999     

A theory of the spatial and temporal dynamics of plant communities

An individual-based model of plant competition for light that uses a definition of plant functional types based on adaptations for the simultaneous use of water and light can reproduce the fundamental spatial and temporal patterns of plant communities. This model shows that succession and zonation result from the same basic processes. Succession is interpreted as a temporal shift in species dominance, primarily in response to autogenic changes in light availability. Zonation is interpreted as a spatial shift in species dominance, primarily in response to the effect of allogenic changes in water availability on the dynamics of competition for light. Patterns of succession at different points along a moisture gradient can be used to examine changes in the ecological roles of various functional types, as well as to address questions of shifts in patterns of resource use through time.Our model is based on the cost-benefit concept that plant adaptations for the simultaneous use of two or more resources are limited by physiological and life history constraints. Three general sets of adaptive constraints produce inverse correlations in the ability of plants to efficiently use (1) light at both high and low availability, (2) water at both high and low availability, and (3) both water and light at low availabilities.The results of this type of individual-based model can be aggregated to examine phenomena at several levels of system organization (i.e., subdisciplines of ecology), including (1) plant growth responses over a range of environmental conditions, (2) population dynamics and size structure, (3) experimental and field observations on the distribution of species across environmental gradients, (4) studies of successional pattern, (5) plant physiognomy and community structure across environmental gradients, and (6) nutrient cycling.     

Effects of different components of diversity on productivity in artificial plant communities

In an experiment on artificial plant communities, the effects of three components of plant diversity—plant species diversity, plant functional group diversity and plant functional diversity—on community productivity and soil water content were compared. We found that simple regression analysis showed a positive diversity effect on ecosystem processes (productivity and soil water content). However, when three components of diversity were included in the multiple regression analyses, the results showed that functional group diversity and functional diversity had more important effects on productivity and resource use efficiency. These results suggested that, compared with species number, functional differences among species and the range of functional traits carried by plants are the basis of biodiversity effects on ecosystem functioning. These diversity effects of increasing functional group diversity or functional diversity were likely because species differing greatly in size, life form, phenology and capacity to capture and use resources efficiently in diverse communities realize complementary resource use in temporal, spatial, and biological ways.     

Higher species diversity explained by stronger spatial aggregation across six neotropical Drosophila communities

Spatial aggregation of competitors over resource patches is generally accepted as an important mechanism maintaining coexistence of species in insect communities exploiting fragmented resources. However, its quantitative effects on local diversity, i.e. the relationship between the degree of aggregation in a community and community diversity, remain unexplored. In this paper, we tested whether stronger spatial aggregation does lead to the predicted higher local diversity. We compared six species-rich Drosophila communities exploiting decaying fruits in central Panama, monitored over one full year (> 25 generations). We found a clear positive relationship between the overall degree of aggregation and community diversity. In addition, aggregation over fruit trees was found to contribute greatly to the overall degree of aggregation and was largely responsible for the observed relationship between aggregation and diversity across communities. In addition, both diversity and aggregation strength were lower in communities in disturbed habitats, which was explained by altered spatial distribution of fruiting trees. This study shows that the aggregation model cannot only explain coexistence, but also differences in local diversity.     

Stoichiometric response of nitrogen-fixing and non-fixing dicots to manipulations of CO2, nitrogen, and diversity

Human activities have resulted in increased nitrogen deposition and atmospheric CO₂ concentrations in the biosphere, potentially causing significant changes in many ecological processes. In addition to these ongoing perturbations of the abiotic environment, human-induced losses of biodiversity are also of major concern and may interact in important ways with biogeochemical perturbations to affect ecosystem structure and function. We have evaluated the effects of these perturbations on plant biomass stoichiometric composition (C:N:P ratios) within the framework of the BioCON experimental setup (biodiversity, CO₂, N) conducted at the Cedar Creek Natural History Area, Minnesota. Here we present data for five plant species: Solidago rigida, Achillea millefolium, Amorpha canescens, Lespedeza capitata, and Lupinus perennis. We found significantly higher C:N and C:P ratios under elevated CO₂ treatments, but species responded idiosyncratically to the treatment. Nitrogen addition decreased C:N ratios, but this response was greater in the ambient CO₂ treatments than under elevated CO₂. Higher plant species diversity generally lowered both C:N and C:P ratios. Importantly, increased diversity also led to a more modest increase in the C:N ratio with elevated CO₂ levels. In addition, legumes exhibited lower C:N and higher C:P and N:P ratios than non-legumes, highlighting the effect of physiological characteristics defining plant functional types. These data suggest that atmospheric CO₂ levels, N availability, and plant species diversity interact to affect both aboveground and belowground processes by altering plant elemental composition.     

Expansion of Rosa rugosa and Hippophaë rhamnoides in coastal grey dunes: Effects at different spatial scales

The study analysed the effects of shrub expansion on vegetation composition and plant species diversity in coastal grey dunes on the North Sea island Spiekeroog, comparing Rosa rugosa and Hippophaë rhamnoides. Species composition was recorded in plots of two spatial scales, 1 and 16 m², considering the full range of shrub cover from less than 10 to almost 100%. Although R. rugosa and H. rhamnoides established and spread in the same grey dune environment, the vegetation of the two shrubland types was much different. While the H. rhamnoides plots were relatively species-rich, characterised by remnant grey dune vegetation with many small, often annual, light-demanding species except in the densest shrubs, the R. rugosa plots were clearly species-poorer due to the loss of many typical grey dune species, including only few shade-tolerant taxa. The total number of species, the number of herbaceous species and of species typical for grasslands decreased with increasing cover of H. rhamnoides and R. rugosa at both spatial scales. For the number of shrubs and shrubland species, hardly any significant effects of shrub cover were observed in R. rugosa, while there were positive effects in H. rhamnoides. Both the Shannon index and evenness decreased with increasing cover of the two shrub species at both spatial scales. Here, the decline in species diversity was more improved in R. rugosa than in H. rhamnoides.     

Herbivory by crabs and the control of algal epibionts on Caribbean host corals

Summary A short-term experiment was conducted to examine the relationships among the branching coral Porites porites, algal epibionts, and a facultative crab associate Mithrax sculptus in Belize, Central America. Initial field observations suggested that coral colonies supporting resident crabs generally had lower algal cover than colonies without crabs. The hypothesis was tested that Mithrax significantly depresses host coral algal cover and thereby indirectly affects host survivorship and growth. Crab accessibility to an array of coral colonies, similarly covered with algal epibionts, was manipulated in three treatments. Results strongly support the hypothesis, with significant differences in algal cover (primarily Dictyota spp.) noted among treatments after only one month. Caged heads with crabs included and uncaged natural controls allowing crabs free access averaged less than 10% cover, whereas mean algal cover exceeded 75% where crabs were excluded. The uncaged treatment, in which crabs were allowed free access to Porites heads was not significantly different from the crab inclusion treatment. Collectively, these results demonstrate that under natural conditions, crabs can have pronounced effects on host corals by reducing fouling algal epibionts. Furthermore, these facultative coral associates may have more important, albeit localized effects on Caribbean corals than has been suggested previously.     

Effects of algal diversity on the production of biomass in homogeneous and heterogeneous nutrient environments: a microcosm experiment

Background

One of the most common questions addressed by ecologists over the past decade has been-how does species richness impact the production of community biomass? Recent summaries of experiments have shown that species richness tends to enhance the production of biomass across a wide range of trophic groups and ecosystems; however, the biomass of diverse polycultures only rarely exceeds that of the single most productive species in a community (a phenomenon called ‘transgressive overyielding’). Some have hypothesized that the lack of transgressive overyielding is because experiments have generally been performed in overly-simplified, homogeneous environments where species have little opportunity to express the niche differences that lead to ‘complementary’ use of resources that can enhance biomass production. We tested this hypothesis in a laboratory experiment where we manipulated the richness of freshwater algae in homogeneous and heterogeneous nutrient environments.

Methodology/Principal Findings

Experimental units were comprised of patches containing either homogeneous nutrient ratios (16∶1 nitrogen to phosphorus (N∶P) in all patches) or heterogeneous nutrient ratios (ranging from 4∶1 to 64∶1 N∶P across patches). After allowing 6–10 generations of algal growth, we found that algal species richness had similar impacts on biomass production in both homo- and heterogeneous environments. Although four of the five algal species showed a strong response to nutrient heterogeneity, a single species dominated algal communities in both types of environments. As a result, a ‘selection effect’–where diversity maximizes the chance that a competitively superior species will be included in, and dominate the biomass of a community–was the primary mechanism by which richness influenced biomass in both homo- and heterogeneous environments.

Conclusions/Significance

Our study suggests that spatial heterogeneity, by itself, is not sufficient to generate strong effects of biodiversity on productivity. Rather, heterogeneity must be coupled with variation in the relative fitness of species across patches in order for spatial niche differentiation to generate complementary resource use.     

Algal species diversity and dominance along gradients of stress and disturbance in marine environments

Data on algal species diversity from six areas along the Swedish coast, differing in salinity, length of growth period and grazing pressure were used to test two main predictions arising from the hump-backed model of species diversity (Grime 1973; Connell & Slatyer 1977; Tilman 1982; Fuentes & Jaksic 1988).Total number of species per m², total biomass per m² and primary production values for each species were calculated for 175 samples. Wave exposure was used as a measure of disturbance. The results are discussed in relation to stress (salinity and light) and disturbance factors (wave effects, ice scouring and grazing).A hump-backed model of species diversity, in relation to biomass per m² was found for all investigated areas. A similar response was also observed along local exposure gradients, with higher biomass and lower species numbers found at the sheltered sites compared to the more exposed ones. The most diverse communities were found at sites with intermediate wave exposure and in communities composed of species with intermediate primary production.It is suggested that the frequency of physical disturbance and severeness of stress strongly affects algal diversity and competition by determining the time interval over which successional replacement of species can occur. This lends support to the non-equilibrium view of community structure giving rise to humpbacked species diversity curves.     

农村混合污水灌溉对土壤养分含量、酶活性及微生物多样性的影响

通过土柱模拟试验,研究了农村混合污水灌溉(WG)对农田土壤pH、养分含量、酶活性及微生物多样性等土壤肥力指标的影响.结果表明:与清水灌溉(CK)相比,经过WG处理,土壤全钾、全磷、速效钾和碱解氮含量增加(4.54%~46.84%),而土壤pH、有机质、全氮和速效磷含量降低(2.02%~32.61%),且土壤pH极显著降低(P<0.01),土壤速效钾含量显著增加(P<0.05);土壤过氧化氢酶和土壤酸性磷酸酶活性低于CK处理(P<0.01),而土壤脲酶和土壤转化酶活性显著高于CK处理(P<0.05);土壤中细菌和真菌的Shannon指数、Ace指数、Chao指数、Coverage指数等均有所提高,但降低了Simpson指数,改变了细菌和真菌在属水平上各优势物种的相对丰度.内梅罗综合指数法评价结果表明,农村混合污水灌溉提高了供试土壤的综合肥力水平.本研究为示范区农村混合污水灌溉模式的田间试验提供了重要依据.     

Stoichiometry of nutrient recycling by vertebrates in a tropical stream: linking species identity and ecosystem processes

Ecological stoichiometry offers a framework for predicting how animal species vary in recycling nutrients, thus providing a mechanism for how animal species identity mediates ecosystem processes. Here we show that variation in the rates and ratios at which 28 vertebrate species (fish, amphibians) recycled nitrogen (N) and phosphorus (P) in a tropical stream supports stoichiometry theory. Mass-specific P excretion rate varied 10-fold among taxa and was negatively related to animal body P content. In addition, the N : P ratio excreted was negatively related to body N : P. Body mass (negatively related to excretion rates) explained additional variance in these excretion parameters. Body P content and P excretion varied much more among taxonomic families than among species within families, suggesting that familial composition may strongly influence ecosystem-wide nutrient cycling. Interspecific variation in nutrient recycling, mediated by phylogenetic constraints on stoichiometry and allometry, illustrates a strong linkage between species identity and ecosystem function.     

Conservation on diversity and distribution patterns of endemic birds in China

The diversity and distribution patterns of endemic species of birds inChina have been studied on the basis of the distribution database of specimencollections and published references. One hundred and two endemic species ofbirds in China, belonging to 53 genera, 16 families and 8 orders are recognized.They account for 8.1% of the total species of China. The distribution patternswere studied and three centers of endemism were found, includingHengduanshan Mountains, mountain areas of western Qinling, north Sichuan Province andSouth Gansu Province, as well as Taiwan Island, which are suggested as conservationpriorities based on endemism. Twenty-four endemics are rare and endangered, listedin the China Red Data Book of Endangered Animals. Among them, 15 species are in rankI and 9 species are in rank II. The study results are to be beneficial tofurther study on both the processing mechanism of the distribution patterns andon the priority of the diversity and endemism conservation.     

Exploration of spatial and temporal patterns of fish diversity and composition in a tropical estuarine system of Mexico

There are many studies of fish assemblages intemperate systems, but little informationexists about tropical estuarine systems,particularly in the Western Atlantic Regionincluding Mexico. We investigated the fishcommunity structure in the Pueblo Viejo lagoon,Veracruz. Biological samples were collectedmonthly for one year at six sites: three withdense stands of Ruppia maritima and threesites without submerged vegetation. For eachsample, temperature, salinity, dissolvedoxygen, turbidity and depth were analyzed. Theunbiased Simpson diversity index, CanonicalCorrespondence Analysis (CCA) and DiscriminantAnalysis (DA) were used to analyze the fishcommunity. Environmental abiotic variablestended to show significant temporal, but notspatial differences. Fish diversity showedonly a weak significant correlation with watertemperature, and relatively strong diversitypeaks, from June to August and April, wererelated to production peaks in the system. Thetwo first axes of CCA accounted for 65% of thespecies-environment biplot variance, whichsuggested that monthly changes of salinity,turbidity and precipitation, and presence orabsence of submerged vegetation, were the mostimportant environmental variables indetermining the observed variability in fishcommunity composition. Further, fish diversitywas significantly different between habitatswith and those without the presence ofsubmerged vegetation (P < 0.02). A DA showedsignificant differences (P < 0.03) in fishcommunity composition between both kinds ofhabitats, with Lagodon rhomboides,Mugil curema and Menidia beryllina(substantially more abundant in habitat withsubmerged vegetation) as the most importantspecies in the discrimination of spatial fishcomposition. Considering both habitatscombined, fewer differences were observed infish diversity and community compositionbetween rainy and dry seasons. Fish communitycomposition showed greater similarity betweenseasons than between habitats, despite the factthat environmental abiotic variables showed aninverse pattern, suggesting that site factors,such as the presence of submerged vegetation,play a more important role in the maintenanceof fish community patterns than those relatedto temporal influence.     

Effects of substratum stability on diversity of stream invertebrates during baseflow at two spatial scales

1. The effects of substratum stability on the diversity of stream invertebrates were assessed at two spatial scales in a Japanese stream during baseflow, from May to June 1998. Deposition and erosion were examined separately as distinct elements of substratum stability by a newly developed method using small steel pins. Stream invertebrates were sampled after 28 days of measurement of substratum stability. We also measured physical environmental variables, current velocity and depth, and food resource parameters including periphyton and particulate organic matter (POM) standing crops.
2. At the scale of the habitat patch, the effects of substratum stability on invertebrates were overwhelmed by those of POM standing crop. Moreover, higher taxon richness at high abundance may simply result from a higher likelihood of more taxa being included in samples. Therefore, this small scale revealed no role for substratum stability in explaining spatial pattern of community diversity.
3. At the reach scale ( n =10), taxon richness and evenness peaked at an intermediate level of deposition, whereas invertebrate abundance did not show any significant relationship. This result, and the pattern of relative abundance of common taxa, implies that the diversity of stream invertebrates was determined by subtle substratum movements and by the habitat preference of each taxon.
4. The difference in the determinant of community parameters between the habitat patch and the reach affirm the importance of a cross-scale analysis to choose an appropriate spatial scale for investigating the community structure of stream invertebrates. Prominent effects of substratum stability, particularly the deposition of substratum particles, during baseflow suggest that subtle and constant movement of small substratum particles can contribute to determine the diversity of stream invertebrates.     

The interaction between nutrient availability and disturbance frequency on the diversity of benthic marine communities on the north-east coast of England

1. Several theoretical models predict under what conditions maximum species diversity can be maintained, and they are often used to develop effective ecosystem management plans. 2. Two models that are currently used to predict patterns of species diversity were empirically tested in marine subtidal benthic communities of different successional stages. 3. The two models were: the interactive effects of nutrient availability and disturbance frequency proposed by Kondoh (2001; Proceedings of the Royal Society London B, 268, 269-271), and the intermediate disturbance hypothesis (IDH) proposed by Connell (1978; Science, 199, 1302-1310). 4. Interactive effects were found to be transient and only occurred in the older communities, while the unimodal pattern suggested by the IDH was not supported in either successional stage. 5. It is concluded that these models are very general and thus lack sufficient explanatory power. Both models require a number of specific prerequisites for maximum diversity to be found, and though applicable in many different ecosystems they need to be refined as tools in order that they can be effectively used in habitat management plans.     

The effect of fertilization on the below-ground diversity and community composition of ectomycorrhizal fungi associated with western hemlock (Tsuga heterophylla)

Fertilization typically reduces ectomycorrhizal diversity shortly after its application but less is known about its longer-term influence on fungal species. Long-term effects are important in forests where fertilizer is rarely applied. We compared fungal species composition in western hemlock control plots with plots last fertilized 7 years ago with nitrogen (N) or nitrogen plus phosphorus (N + P). The N + P fertilization had a significant lingering effect, increasing the tree size and foliar P content of the western hemlocks. From ectomycorrhizal roots of 24-year-old trees from northern Vancouver Island, Canada, we identified fungi from 12 samples per treatment, by amplifying, cloning, and sequencing fungal ribosomal DNA fragments, placing sequences with 97% or more identity in the same operational taxonomic unit (OTU). Diversity was high across treatments; we detected 77 fungal OTUs, 52 from ectomycorrhizal genera, among 922 clone sequences. The five most frequent OTUs were similar in abundance across treatments. Only 19 OTUs matched any of the 197 previously reported ectomycorrhizal species of western hemlock. Species composition but not diversity in nitrogen plus phosphorus plots differed significantly from control or nitrogen plots. Two Cortinarius OTUs were indicator species for nitrogen plus phosphorus plots and presence of Cortinarius cinnamomeus was correlated with control or nitrogen plots. After 7 years, fertilization history had made no detectable difference in ectomycorrhizal fungal diversity, but long-lasting changes in environment resulting from fertilization had a lingering effect on fungal ectomycorrhizal species composition. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effects of population density on forest structure and species richness and diversity of trees in Kampong Thom Province, Cambodia

This study examined differences in stand structure, tree species richness, and tree species diversity in relation to population density in Kampong Thom Province, Cambodia. Tree data were obtained from a 1997 forest inventory involving 60 clusters (540 plots) systematically distributed over 30% of the provincial forest area. Spatially referenced population data were obtained from the 1998 national population census. The average number of trees per cluster was 356/ha, the average basal area, 23 m²/ha, the average stand volume, 217 m³/ha, and the average aboveground biomass, 273 Mg/ha for all trees of DBH 10 cm and larger. The average species richness per cluster was 37 species, while average species diversity was measured as 0.916 using Simpson’s index and 2.98 by Shannon’s index. Significant negative correlations were generally found between population density surrounding clusters and tree density, basal area, stand volume, aboveground biomass, and species richness and diversity for three examined diameter classes (DBH of 10–30, ≥30, and ≥10 cm). As the distance from clusters for calculating population density increased, the correlation levels increased up to 5 or 7 km, depending on the variables and diameter class, and then stayed relatively constant for stand structure variables and decreased for species richness and diversity. The results indicate that evidence of disturbance was more pronounced at higher population density up to around 5 to 7 km. We suggest that introduction of greater controls on human disturbance should be a high priority for resource management and conservation in Kampong Thom Province and, presumably, Cambodia as a whole.