Stability Of Community Biomass Research Articles

Short‐term grazing reduced community stability by decreasing community‐wide asynchrony and dominant species stability

AbstractThe effects of grazing on natural grasslands' plant composition, diversity, and productivity depend on the intensity of grazing. Besides grazing intensity, animal composition is also important. However, whether and how sheep grazing intensity affects the temporal biomass stability of plant communities is unclear. Here, we conducted a 5‐year grazing experiment to evaluate the effects of four grazing intensities on community biomass stability and the underlying mechanisms. Our results showed that the higher grazing intensity significantly decreased community biomass stability, community‐wide asynchrony, functional groups asynchrony, dominant species stability, and species dominance, but did not affect species richness. The results of structural equation modeling revealed that grazing decreased community biomass stability by decreasing dominant species stability and community‐wide asynchrony, which was attributable to the reduction in plant functional group asynchrony. Our results highlight the importance of functional group composition and dynamics in predicting the changes in community function in sheep grazing grassland ecosystems. Under continuous seasonal grazing conditions, the sustainable function and human services of grasslands in the agropastoral ecotone might decrease in the future.

Species asynchrony maintains community stability under different warming conditions

Abstract Asymmetric seasonal warming, characterized by more pronounced temperature increases in winter than in summer, has become a critical feature of global warming, especially in cold and high-altitude regions. Previous studies have primarily focused on year-round warming, while comparatively less attention was paid to winter warming. However, a significant knowledge gap exists regarding the impacts of winter warming on ecosystem functions. To address this, we conducted an 8-year manipulated warming experiment in an alpine grassland on the Tibetan Plateau, employing three treatments: no warming, year-round warming and winter warming. We found that neither year-round warming nor winter warming significantly alters species richness at the community level. Notably, community biomass stability was maintained via species asynchrony. However, warming exerted significant effects on the plant abundance groups (dominant, common and rare species). Specifically, winter warming enhanced the stability of dominant species by increasing species asynchrony of dominant species, as the compensatory dynamics occurred between the grass and forbs. In contrast, year-round warming reduced the stability of common species, correlated with an increase in species richness and a decline in asynchrony among common species. Thus, our study underscores the capacity of alpine grassland to maintain community biomass stability via asynchrony dynamics of species under different warming conditions, although the stability of different abundance groups would be changed. Importantly, our results provide valuable insights for understanding the alpine grassland ecosystem on the Tibetan Plateau.

Context‐dependent impact of changes in precipitation on the stability of grassland biomass

Abstract Community stability plays a crucial role in ensuring the consistent provision of ecosystem services despite environmental changes, including alterations in precipitation patterns. Over the past decades, significant progress has been made in understanding the responses of the stability of grassland plant communities and underlying mechanisms, defined as the ratio of the temporal mean biomass to the standard deviation. However, a crucial knowledge gap remains regarding whether the impacts of precipitation on the stability of grassland biomass are contingent upon specific contextual factors. Here, we examined the stability of above‐ and below‐ground biomass in adjacent grass‐ and shrub‐dominated communities through a 7‐year manipulation experiment involving seven precipitation levels: 20%, 40% and 60% decrease, as well as 20%, 40% and 60% increase in natural rainfall, in addition to ambient precipitation. We found that the stability of community biomass was influenced by three contextual factors including the magnitude and directionality of precipitation, above‐ and below‐ground biomass and the type of vegetation. In particular, higher and more intense precipitation resulted in higher stability of above‐ground biomass in both grass‐ and shrub‐dominated communities. Conversely, higher precipitation intensity led to decreased below‐ground biomass stability in grass‐dominated communities but increased below‐ground biomass stability in shrub‐dominated communities. Species stability and species asynchrony consistently played a positive role in explaining the stability of above‐ground biomass in both grass‐ and shrub‐dominated communities. However, species asynchrony negatively influenced below‐ground biomass stability in grass‐dominated communities without a comparable effect in shrub‐dominated communities. The preeminent contribution to the total community biomass was identified in the stability of below‐ground biomass, evident in both grass‐dominated and shrub‐dominated communities. Synthesis. This study highlights that while the specific effects of changes in precipitation may vary depending on the context, the fundamental processes governing biomass stability are consistent. These findings elucidate the desert steppe ecosystems' adaptive response to precipitation variations and emphasize their pivotal role in maintaining ecosystem functions under climatic perturbations. Read the free Plain Language Summary for this article on the Journal blog.

Fungal pathogens increase community temporal stability through species asynchrony regardless of nutrient fertilization.

Natural enemies and their interaction with host nutrient availability influence plant population dynamics, community structure, and ecosystem functions. However, the nature in which these factors influence patterns of community stability, as well as the direct and indirect processes underlying that stability, remain unclear. Here, we investigated the separate and interactive roles of fungal/oomycete pathogens and nutrient fertilization on the temporal stability of community biomass and the potential mechanisms using a factorial experiment in an alpine meadow. We found that fungal pathogen exclusion reduced community temporal stability mainly through decreasing species asynchrony, while fertilization tended to reduce community temporal stability through decreasing species stability. However, there was no interaction between pathogen exclusion and nutrient fertilization. These effects were largely due to the direct effects of the treatments on plant biomass, and not due to indirect effects mediated through plant diversity. Our findings highlight the need for a multi-trophic perspective in field studies examining ecosystem stability.

Species Diversity and Stability of Dominant Species Dominate the Stability of Community Biomass in an Alpine Meadow Under Variable Precipitation

Species Diversity and Stability of Dominant Species Dominate the Stability of Community Biomass in an Alpine Meadow Under Variable Precipitation

Tree diversity depending on environmental gradients promotes biomass stability via species asynchrony in China’s forest ecosystems

There is mounting evidence that biodiversity promotes ecological stability in changing environments. However, understanding diversity–stability relationships and their underlying mechanisms across large-scale tree diversity and natural environmental gradients are still controversial and largely lacking. We used thirty-nine 0.12 ha long-term permanent forest plots spanning China’s various forest types to test the effects of multiple abiotic (climate, soil, age and topography) and biotic factors (taxonomic and structural diversity, functional diversity and community-mean traits, and species asynchrony) on biomass stability and its components (mean biomass and biomass variability) over time. We used multiple analytical methods to identify the best explanatory variables and complicated causal relationships for community biomass stability. Our results showed that species richness increased biomass stability by promoting species asynchrony. Structural and functional diversity had a weaker effect on biomass stability. Forest age and structural diversity increased mean biomass and biomass variability significantly and simultaneously. Communities dominated by tree species with high wood density had high biomass stability. Soil nitrogen enhanced biomass stability directly and indirectly through its effects on mean biomass. Soil nitrogen to phosphorus ratio increased biomass stability via increasing species asynchrony. Precipitation indirectly increased biomass stability by affecting tree diversity. Moreover, the direct and indirect effects of soil nutrients on biomass stability were greater than that of climate variables. Our results suggest that species asynchrony is the main mechanism proposed to explain the stabilizing effect of diversity on community biomass, supporting two mechanisms, namely, the biodiversity insurance hypothesis and complementary dynamics. Soil and climate factors also play an important role in shaping diversity–stability relationships. Our results provide a new insight into how tree diversity affects ecosystem stability across diverse community types and large-scale environmental gradients.

Stability response of alpine meadow communities to temperature and precipitation changes on the Northern Tibetan Plateau.

Biomass temporal stability plays a key role in maintaining sustainable ecosystem functions and services of grasslands, and climate change has exerted a profound impact on plant biomass. However, it remains unclear how the community biomass stability in alpine meadows responds to changes in some climate factors (e.g., temperature and precipitation). Long‐term field aboveground biomass monitoring was conducted in four alpine meadows (Haiyan [HY], Henan [HN], Gande [GD], and Qumalai [QML]) on the Qinghai‐Tibet Plateau. We found that climate factors and ecological factors together affected the community biomass stability and only the stability of HY had a significant decrease over the study period. The community biomass stability at each site was positively correlated with both the stability of the dominant functional group and functional groups asynchrony. The effect of dominant functional groups on community stability decreased with the increase of the effect of functional groups asynchrony on community stability and there may be a ‘trade‐off’ relationship between the effects of these two factors on community stability. Climatic factors directly or indirectly affect community biomass stability by influencing the stability of the dominant functional group or functional groups asynchrony. Air temperature and precipitation indirectly affected the community stability of HY and HN, but air temperature in the growing season and nongrowing season had direct negative and direct positive effects on the community stability of GD and QML, respectively. The underlying mechanisms varied between community composition and local climate conditions. Our findings highlighted the role of dominant functional group and functional groups asynchrony in maintaining community biomass stability in alpine meadows and we highlighted the importance of the environmental context when exploring the stability influence mechanism. Studies of community stability in alpine meadows along with different precipitation and temperature gradients are needed to improve our comprehensive understanding of the mechanisms controlling alpine meadow stability.

Common Species Stability and Species Asynchrony Rather than Richness Determine Ecosystem Stability Under Nitrogen Enrichment

Global nitrogen (N) deposition generally reduces ecosystem stability. However, less is known about the responses of ecosystem stability and its driving mechanisms under different N addition gradients. We conducted a four-year N addition experiment in an alpine meadow, using six levels of N addition rates (0, 2, 4, 8, 16, 32 g N m−2 year−1) to examine the effects of N addition on plant community biomass stability and the underlying mechanisms. We found that the stability of ecosystem aboveground net primary productivity (ANPP) decreased linearly with increasing N addition rates, even though it had no effect on plant species richness at low N addition rates and significantly reduced species richness at high N addition rates. The most remarkable finding is that the main mechanism underlying ecosystem stability shifted with N addition rates. The decrease of common species stability contributed most to the reduction of plant community biomass stability under low N addition rates (N0–N4), whereas the decrease of species asynchrony contributed most to the reducing plant community biomass stability under high N addition rates (N8–N32). Our results indicate that species diversity was not a significant predictor of plant community biomass stability in this alpine meadow, which challenges the traditional knowledge. This study highlights the shifts of main mechanism regulating plant community biomass stability under different N addition rates, and suggests that continuous nitrogen deposition in the future may reduce ecosystem stability and potentially impeding the sustainable provision of ecosystem functions and services.

Species dominance rather than species asynchrony determines the temporal stability of productivity in four subtropical forests along 30 years of restoration

Understanding biodiversity and its relationship with ecosystem functioning along forest succession is extremely important to assessing dynamics of community stability and ecosystem integrity. Previous studies have revealed that increases in species richness, phylogenetic diversity (PD), species asynchrony and dominance can stabilize the temporal stability of community biomass in grasslands. However, how these determinants influence the stabilizing effect of biodiversity on forest productivity remains poorly understood. We analyzed the relationships between woody plant diversity and productivity stability along 30 years of restoration (1985–2015) in four types of subtropical forest: a mixed Eucalyptus plantation (EE), an Acacia mangium monoculture (AM), a mixed native species plantation (NS), and a mixed coniferous plantation (MC). Our results showed that community stability in three mixed species plantations (EE, NS, and MC) rather than the AM monoculture augmented remarkably as restoration proceeded. Both species richness and phylogenetic diversity significantly stabilized community productivity in the mixed species plantations instead of the monoculture during the 30-year restoration period. Species asynchrony was not a significant factor contributing to the forest productivity stability. Instead, community stability was mainly driven by that of the dominant tree species, and to a lesser extent, by the species richness. We demonstrated the more important role of species dominance in maintaining the temporal stability of forest productivity, which differs from that (species asynchrony) for grassland communities.

Arbuscular mycorrhizal fungi alleviate the negative effect of nitrogen deposition on ecosystem functions in meadow grassland

AbstractNitrogen (N) deposition can reduce plant species richness and cause grassland degradation, thus affecting grassland ecosystem stability. Arbuscular mycorrhizal (AM) fungi play an important role in ecosystem stability. However, the influences of AM fungi on grassland ecosystem stability under N deposition remain unclear. We need more information on the impacts of N accumulation on the interactions between AM fungi and the plant community. To test the contribution of AM fungi to grassland stability under N deposition, a 5‐year field experiment was conducted in a temperate meadow with two manipulated factors, namely, N addition and AM fungi suppression. The plant species richness and diversity, biomass stability, litter decomposition, and greenhouse gas emissions were quantified. Under N addition, AM fungi did not affect the plant species diversity and richness but altered the coverages of different functional groups and increased the aboveground productivity and biomass stability. Litter decomposition increased under N addition and increased more in the treatment where AM fungi were not suppressed. The emissions of N2O and CH4 in the AM fungi suppression treatment were much higher than those in the nonsuppression treatment under N addition. Our results suggest that AM fungi can alter the plant community structure, increase plant productivity and community biomass stability, accelerate litter decomposition, and reduce the soil total N concentration and emissions of N2O and CH4 under N addition. Our results highlight that the conservation of AM fungi should be considered to alleviate grassland degradation and maintain grassland ecosystem multifunctionality in the future considering global change.

Plant functional groups asynchrony keep the community biomass stability along with the climate change- a 20-year experimental observation of alpine meadow in eastern Qinghai-Tibet Plateau

Climate changes can affect the temporal stability of plant community biomass on the Qinghai-Tibet Plateau, but most studies were based on short-term field climate manipulation experiments. However, the response of biomass stability of natural alpine meadow remains largely unexplored. We conducted a 20-year experimental study monitoring aboveground biomass of plant functional groups (grass, forb and sedge) and community in eastern QTP, with linear regressions and a path analysis of: annual temperature, annual night minimum temperature, annual daytime maximum temperature, annual precipitation, annual daytime precipitation, annual night precipitation, biomass stability of grass, biomass stability of forb, plant functional groups asynchrony to assess the influence climate change and biological factors on the temporal stability of plant community biomass. We found that it was plant functional groups asynchrony rather than climate change that determined the temporal stability of plant community biomass. Our findings suggest that future climate change has a considerable uncertainty in the temporal stability of the plant community biomass in the alpine meadow and we should combine with both field climate manipulation experiments and long-term observational experiments to assess the influence of climate change on the temporal stability of plant community.

Modelling fishery induced impacts on the food web of the continental shelf off central south Chile using a size based network approach

The continental shelf off central-south Chile sustains highly productive fisheries . The sustainability of these resources is nevertheless in jeopardy since many of them are either overexploited or collapsed. Using an allometrically (size-based) parameterized model of the shelf’s food web, we analyze the likely ecosystem effects of fishing in this system by measuring the response of several ecological indicators to changes in fishing pressure. Indicators performed as follows: (i) insensitive (community biomass stability, clustering coefficient), (ii) varying directly (number of species going extinct) or inversely (NBSS coefficient of determination), and (iii) abrupt inverse change, but then insensitive beyond a threshold (FiB index, Mean Trophic Level of the Catch, NBSS slope, and total community biomass). The latter four indicators seem less informative for management once a fishery has developed. Simulations showed that fishing any single species affected several species through food web-mediated mechanisms, then making difficult to predict the effects of fishing on the abundance of target and non-target species. Therefore, conservation measures should not rely exclusively on reducing fishing mortality for a given target species, but also take into account the status of interacting species. Normal 0 21 false false false ES-CL JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; border:none; mso-border-alt:none black 0cm; padding:0cm; mso-padding-alt:0cm 0cm 0cm 0cm; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ansi-language:ES-MX; mso-fareast-language:ZH-CN;}

BiodiversityVersusStability: the Biological Effect of Plant Functional Traits on Ecosystem Functioning in Grasslands Dominated byLeymus chinensis

Although diversity-ecosystem theory predicts that ecosystem functioning is strongly determined by species number, species traits play an important role in regulating ecosystem-level dynamics. We analyze responses of species attributes to diversity level and resource availability, and explore their consequences for ecosystem functioning and ultimately assess the contributions of five traits (vegetative plant height, clonal growth, root depth, cespitose habit and seed mass) to ecosystem functioning defined by spatial stability of community biomass. We found that functional traits disproportionately affected spatial stability. Relationships between species functional traits and spatial stability of community biomass indicated that diversity of vegetative plant height facilitated stability of a nitrogen fertilized undisturbed natural community (NAT), and that of a phosphorus fertilized forb, legume and bunchgrass community (FLB). The clonal growth form was also identified as a stabilizing trigger for a unfertilized undisturbed natural community (NAT), whereas diversity in root depth, cespitose habit and seed mass were related to destabilization of a nitrogen fertilized rhizomatous grass community (RRR). Studies quantifying interactions among plant traits, community structure and ecological functioning will contribute much more to understanding of the effects of the ecological behavior of specific traits on the ecosystem functioning.

Environmental changes drive the temporal stability of semi‐arid natural grasslands through altering species asynchrony

Summary Stability is an important property of ecological systems, many of which are experiencing increasing levels of anthropogenic environmental changes. However, how these environmental changes influence ecosystem stability remains poorly understood. We conducted an 8‐year field experiment in a semi‐arid natural grassland to explore the effects of two common environmental changes, precipitation and nitrogen enrichment, on the temporal stability of plant above‐ground biomass. A split‐plot design, with precipitation as the main plot factor and nitrogen as the subplot factor, was used. Temporal stability was related to potential explanatory abiotic and biotic variables using regressions and structural equation modelling. Increase in growing season precipitation enhanced plant species richness and promoted temporal stability of plant above‐ground biomass. Nitrogen fertilization, however, reduced both plant species richness and temporal stability of plant above‐ground biomass. Contrary to expectations, species richness was not an important driver of stability. Instead, community temporal stability was mainly driven by water and nitrogen availability that modulated the degree of species asynchrony and, to a lesser extent, by the stability of dominant plant species. Synthesis. Our results highlight the importance of limiting resources for regulating community biomass stability and suggest that the projected increase in growing season precipitation may potentially offset negative effects of increased atmospheric nitrogen deposition on species diversity and community stability in semi‐arid grasslands.

Phylogenetic diversity stabilizes community biomass

Aims The relationship between biodiversity and ecological stability is a long-standing issue in ecology. Current diversity–stability studies, which have largely focused on species diversity, often report an increase in the stability of aggregate community properties with increasing species diversity. Few studies have examined the linkage between phylogenetic diversity, another important dimension of biodiversity, and stability. By taking species evolutionary history into account, phylogenetic diversity may better capture the diver sity of traits and niches of species in a community than species diversity and better relate to temporal stability. In this study, we investigated whether phylogenetic diversity could affect temporal stability of community biomass independent of species diversity. Methods We performed an experiment in laboratory microcosms with a pool of 12 bacterivorous ciliated protist species. To eliminate the possibility of species diversity effects confounding with phylogenetic diversity effects, we assembled communities that had the same number of species but varied in the level of phylogenetic diversity. Weekly disturbance, in the form of short-term temperature shock, was imposed on each microcosm and species abundances were monitored over time. We examined the relationship between temporal stability of community biomass and phylogenetic diversity and evaluated the role of several stabilizing mechanisms for explaining the influence of phylogenetic diversity on temporal stability. Important Findings Our results showed that increasing phylogenetic diversity promoted temporal stability of community biomass. Both total community biomass and summed variances showed a U-shaped relationship with phylogenetic diversity, driven by the presence of large, competitively superior species that attained large biomass and high temporal variation in their biomass in both low and high phylogenetic diversity communities. Communities without these species showed patterns consistent with the reduced strength of competition and increasingly asynchronous species responses to environmental changes under higher phylogenetic diversity, two mechanisms that can drive positive diversity–stability relationships. These results support the utility of species phylogenetic knowledge for predicting ecosystem functions and their stability.

Shared ancestry influences community stability by altering competitive interactions: evidence from a laboratory microcosm experiment using freshwater green algae.

The impact of biodiversity on the stability of ecological communities has been debated among biologists for more than a century. Recently summarized empirical evidence suggests that biodiversity tends to enhance the temporal stability of community-level properties such as biomass; however, the underlying mechanisms driving this relationship remain poorly understood. Here, we report the results of a microcosm study in which we used simplified systems of freshwater microalgae to explore how the phylogenetic relatedness of species influences the temporal stability of community biomass by altering the nature of their competitive interactions. We show that combinations of two species that are more evolutionarily divergent tend to have lower temporal stability of biomass. In part, this is due to negative 'selection effects' in which bicultures composed of distantly related species are more likely to contain strong competitors that achieve low biomass. In addition, bicultures of distantly related species had on average weaker competitive interactions, which reduced compensatory dynamics and decreased the stability of community biomass. Our results demonstrate that evolutionary history plays a key role in controlling the mechanisms, which give rise to diversity-stability relationships. As such, patterns of shared ancestry may help us predict the ecosystem-level consequences of biodiversity loss.

Biodiversity simultaneously enhances the production and stability of community biomass, but the effects are independent

To predict the ecological consequences of biodiversity loss, researchers have spent much time and effort quantifying how biological variation affects the magnitude and stability of ecological processes that underlie the functioning of ecosystems. Here we add to this work by looking at how biodiversity jointly impacts two aspects of ecosystem functioning at once: (1) the production of biomass at any single point in time (biomass/area or biomass/ volume), and (2) the stability of biomass production through time (the CV of changes in total community biomass through time). While it is often assumed that biodiversity simultaneously enhances both of these aspects of ecosystem functioning, the joint distribution of data describing how species richness regulates productivity and stability has yet to be quantified. Furthermore, analyses have yet to examine how diversity effects on production covary with diversity effects on stability. To overcome these two gaps, we reanalyzed the data from 34 experiments that have manipulated the richness of terrestrial plants or aquatic algae and measured how this aspect of biodiversity affects community biomass at multiple time points. Our reanalysis confirms that biodiversity does indeed simultaneously enhance both the production and stability of biomass in experimental systems, and this is broadly true for terrestrial and aquatic primary producers. However, the strength of diversity effects on biomass production is independent of diversity effects on temporal stability. The independence of effect sizes leads to two important conclusions. First, while it may be generally true that biodiversity enhances both productivity and stability, it is also true that the highest levels of productivity in a diverse community are not associated with the highest levels of stability. Thus, on average, diversity does not maximize the various aspects of ecosystem functioning we might wish to achieve in conservation and management. Second, knowing how biodiversity affects productivity gives no information about how diversity affects stability (or vice versa). Therefore, to predict the ecological changes that occur in ecosystems after extinction, we will need to develop separate mechanistic models for each independent aspect of ecosystem functioning.

Annual variation of community biomass is lower in more diverse stream fish communities

Anthropogenic influences have disproportionally affected freshwater ecosystems, and a loss of biodiversity is forecasted to greatly reduce ecosystem function and services. Loss of species may destabilize communities by limiting the stabilizing forces of compensatory dynamics and/or statistical averaging, both of which are effects that can buffer variation in aggregate community properties. Currently, support for positive diversity‐stability relationships stems from experiments with simple communities at small spatial and temporal scales, and application to natural communities is limited. Using a long‐term dataset of 35 stream fish communities matched with hydrologic data, we show that community stability (annual variation of standing biomass of fishes) was less variable in more species‐rich communities and was not associated with stream hydrology. Only the statistical averaging model of community stability was consistent with observed patterns of lower biomass variation in more species‐rich communities. Our findings suggest anthropogenically induced extirpation of vertebrate consumers may lower community biomass stability in complex ecosystems.

Predation Alters Relationships between Biodiversity and Temporal Stability

Abstract: Ecologists disagree on how diversity affects stability. At the heart of the controversy is the relationship between diversity and population stability, with conflicting findings from both theoretical and empirical studies. To help reconcile these results, we propose that this relationship may depend on trophic complexity, such that positive relations tend to emerge in multitrophic but not single-trophic communities. This hypothesis is based on the premise that stabilizing weak trophic interactions restrain population oscillations associated with strong trophic interactions in diverse multitrophic communities. We tested this hypothesis using simple freshwater bacterivorous protist communities differing in diversity with and without a predatory protist species. Coupling weak and strong trophic interactions reduced population temporal variability of the strong-interacting species, supporting the stabilizing role of weak interactions. In keeping with our hypothesis, predation altered the overall effect of diversity on population temporal stability and, in particular, caused a reversal of the diversity-stability relationship (negative without predators and positive with predators) for the strong-interacting species. A similar role of predation was also observed when examining the relationship between diversity and temporal stability of community biomass. Together, these findings demonstrated strong interactive effects of trophic interactions and diversity on temporal stability of population and community properties.

Species Diversity and Biomass Stability

With the current accelerating rate of biodiversity extinction, there is great interest in how species diversity influences ecosystem properties. In this article, we investigate the relationship between species diversity and the stability of community biomass in the face of stochastic perturbations of species' abundances. The model explicitly includes species' interactions. We show that the pattern of species' interactions affects whether the relationship between diversity and biomass stability is positive or negative. In particular, assumptions about community structure influence the relationship between species diversity and community biomass, which in turn influences the diversity-stability relationship. We also discuss the relationship between diversity and another type of stability, the proportional change in community biomass with the extinction or introduction of a species. Regardless of community type, diversity buffers the change in biomass when a species is added or removed.