Temporal stability vs. community matrix measures of stability and the role of weak interactions

Relationships between different measures of stability are not well understood in part because empiricists and theoreticians tend to measure different aspects and most studies only explore a single form of stability. Using time‐series data from experimental plankton communities, we compared temporal stability typically measured by empiricists (coefficient of variation in biomass) to stability measures typically measured by theoreticians derived from the community matrix (asymptotic resilience, initial resilience and intrinsic stochastic invariability) using first‐order multivariate autoregressive models (MAR). Community matrices were also used to derive estimates of interaction strengths between plankton groups. We found no relationship between temporal stability and stability measures derived from the community matrix. Weaker interaction strengths were generally associated with higher stability for community matrix measures of stability, but were not consistently associated with higher temporal stability. Temporal stability and stability measures derived from the community matrix stability appear to represent different aspects of stability reflecting the multi‐dimensionality of stability.     

南京市城乡梯度上景观变化的空间与数量稳定性

为揭示城市化过程中景观稳定性及其区位分异,本文在多时相Landsat TM遥感影像的支持下,应用Kappa指数方法对1988—2008年间南京市城乡梯度上景观要素(除丘陵山地及大规模水体外)的空间位置变化与数量变化进行了研究。结果表明:耕地的数量稳定性较高,但空间位置稳定性较低;而聚落用地空间位置稳定性较高,但数量稳定性却较低;水体的空间位置和数量稳定性都比较高;林地和其他用地的数量以及空间位置稳定性都比较低。在城乡梯度上,随着城市化程度增加,景观的空间位置稳定性呈上升趋势,而数量稳定性则表现出下降趋势。对于已完成城市化的中心城区,景观的数量稳定性迅速上升,其景观要素的组成和空间分布特征均趋于稳定。聚落用地和耕地的空间位置和数量稳定性在不同城乡梯度带间变化较大,而水体和林地的空间与数量稳定性受城市化过程影响较小。     

金融稳定性与生态稳定性

亚洲金融危机以后,世界各国评估和诊断金融体系稳健程度的实务性研究取得了很大进展,但金融稳定性问题的理论研究仍相对滞后.本文讨论了用生态稳定性思想方法研究金融稳定性问题.文章先比较了金融稳定性的概念和生态学中有关稳定性的概念的异同,把生态稳定性概念移植、引申到金融系统中,建立了金融群落数学模型,给出了金融群落金融稳定的定义,论证了金融种群确定模型和随机模型的稳定性,介绍了金融群落随机模型的稳定性,最后分析了金融群落等级结构的稳定性.     

再论生物多样性与生态系统的稳定性

本文在简述生物多样性与生态系统稳定性研究动态的基础上,从生物多样性和稳定性的概念出发,指出忽视多样性和稳定性的生物组织层次可能是造成观点纷争的根源之一。特定生物组织层次的稳定性可能更多地与该层次的多样性特征相关,探讨多样性和稳定性的关系应从不同的生物组织层次上进行,抗动是生态系统多样性与稳定性关系悖论中的重要因子,如果根据扰动的性质,把生态系统（或其他组织层次）区分为受非正常外力干扰和受环境因子时间异质性波动干扰2类系统,稳定性的4个内涵可以理解为：对于受非正常外力干扰的系统而言,抵抗力和恢复力是稳定性适宜的测度指标;对于受环境因子时间异质性波动干扰和系统而言。利用持久性和变异性衡量系统的稳定性则更具实际意义。结合对群落和种群层次多样性与稳定性相关机制的初步讨论,本文认为;在特定的前提下,多样性可以导致稳定性。     

生态系统稳定性及其与生物多样性的关系

在全球变化背景下, 生态系统能否长期有效地维持功能并提供服务, 有赖于其稳定性。生态系统稳定性及其与生物多样性的关系, 是生态学研究的核心问题, 生物多样性能否促进生态系统稳定性曾引起很多争论。该文在前期国内外综述和研究的基础上, 重点从以下三个方面对近期进展做了总结。第一, 介绍了近期理论研究在生态系统稳定性的内涵及不同稳定性指标间的内在关联方面取得的新认识。第二, 梳理了最近基于生物多样性实验开展的多项整合分析研究和理论探索, 以及在多维度框架下开展的多样性-稳定性关系研究。第三, 详细介绍了最近发展起来的多尺度稳定性理论框架, 对稳定性的尺度依赖、多样性-稳定性的多尺度关系等新议题做了探讨。最后, 提出了本领域有待进一步研究的关键问题和方向建议。     

Nitrogen enrichment weakens ecosystem stability through decreased species asynchrony and population stability in a temperate grassland

Biodiversity generally promotes ecosystem stability. To assess whether the diversity–stability relationship observed under ambient nitrogen (N) conditions still holds under N enriched conditions, we designed a 6‐year field experiment to test whether the magnitude and frequency of N enrichment affects ecosystem stability and its relationship with species diversity in a temperate grassland. Results of this experiment showed that the frequency of N addition had no effect on either the temporal stability of ecosystem and population or the relationship between diversity and stability. Nitrogen addition decreased ecosystem stability significantly through decreases in species asynchrony and population stability. Species richness was positively associated with ecosystem stability, but no significant relationship between diversity and the residuals of ecosystem stability was detected after controlling for the effects of the magnitude of N addition, suggesting collinearity between the effects of N addition and species richness on ecosystem stability, with the former prevailing over the latter. Both population stability and the residuals of population stability after controlling for the effects of the magnitude of N addition were positively associated with ecosystem stability, indicating that the stabilizing effects of component populations were still present after N enrichment. Our study supports the theory predicting that the effects of environmental factors on ecosystem functioning are stronger than those of biodiversity. Understanding such mechanisms is important and urgent to protect biodiversity in mediating ecosystem functioning and services in the face of global changes.     

Contrasting effects of diversity on the temporal stability of plant populations

Recent theoretical and empirical work suggests that diversity enhances the temporal stability of a community. However, the effect of diversity on the stability of the individual populations within the community remains unclear. Some models predict a decrease of population stability with diversity, whereas others suggest that diversity has a stabilizing effect on populations. Empirical evidence for either relationship between population stability and diversity is weak. The few studies that directly assessed the stability of populations reported contradicting results. We used a six-year data-set from a plant diversity experiment to examine the relationships between diversity and temporal stability of plant biomass. Our results show that stability increased with diversity at the community-level, while the stability of populations, averaged over all species, decreased with diversity. However, when examining species separately we found positive, negative and neutral relationships between population stability and diversity. Our findings suggest that diversity may contribute to the stability of ecosystem services at the community level, but the effect of diversity on the stability of the individual populations within the community are generally negative. However, different species within the community may show strikingly different relationships between diversity and stability.     

On the dimensionality of ecological stability

Ecological stability is touted as a complex and multifaceted concept, including components such as variability, resistance, resilience, persistence and robustness. Even though a complete appreciation of the effects of perturbations on ecosystems requires the simultaneous measurement of these multiple components of stability, most ecological research has focused on one or a few of those components analysed in isolation. Here, we present a new view of ecological stability that recognises explicitly the non‐independence of components of stability. This provides an approach for simplifying the concept of stability. We illustrate the concept and approach using results from a field experiment, and show that the effective dimensionality of ecological stability is considerably lower than if the various components of stability were unrelated. However, strong perturbations can modify, and even decouple, relationships among individual components of stability. Thus, perturbations not only increase the dimensionality of stability but they can also alter the relationships among components of stability in different ways. Studies that focus on single forms of stability in isolation therefore risk underestimating significantly the potential of perturbations to destabilise ecosystems. In contrast, application of the multidimensional stability framework that we propose gives a far richer understanding of how communities respond to perturbations.     

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.     

刈割强度对大针茅草原地上生物量时间稳定性的影响

在草地刈割过程中, 群落地上生物量的时间稳定性与物种多样性及物种异步性关系密切。本文基于2014-2018年的野外刈割实验, 研究了围封(对照, 无刈割)、轻度(留茬8 cm)、中度(留茬5 cm)和重度(留茬2 cm)等不同刈割强度对内蒙古大针茅(Stipa grandis)典型草原地上生物量时间稳定性的影响。结果表明: (1)与围封相比, 刈割对群落时间稳定性无显著影响, 但对种群平均时间稳定性影响显著, 重度刈割处理的种群平均时间稳定性显著降低; 且种群平均时间稳定性与群落时间稳定性无显著相关关系, 表明这二者独立波动。(2)与围封相比, 重度刈割处理的物种丰富度显著降低, 但它与群落时间稳定性无显著相关关系, 表明物种丰富度不是群落地上生物量时间稳定性的主导因素; 此外, 重度刈割处理的群落抵抗力显著降低, 但也与群落时间稳定性无显著相关关系。(3)异步性与群落稳定性存在极显著正相关关系, 但刈割对异步性无显著影响, 故未造成群落稳定性显著变化。因此, 异步性可能是影响群落时间稳定性的主导效应之一, 在草地管理与利用过程中, 可从物种异步性角度来对草地稳定性进行评价。     

Stability and the evolvability of function in a model protein

Functional proteins must fold with some minimal stability to a structure that can perform a biochemical task. Here we use a simple model to investigate the relationship between the stability requirement and the capacity of a protein to evolve the function of binding to a ligand. Although our model contains no built-in tradeoff between stability and function, proteins evolved function more efficiently when the stability requirement was relaxed. Proteins with both high stability and high function evolved more efficiently when the stability requirement was gradually increased than when there was constant selection for high stability. These results show that in our model, the evolution of function is enhanced by allowing proteins to explore sequences corresponding to marginally stable structures, and that it is easier to improve stability while maintaining high function than to improve function while maintaining high stability. Our model also demonstrates that even in the absence of a fundamental biophysical tradeoff between stability and function, the speed with which function can evolve is limited by the stability requirement imposed on the protein.     

Global stability, local stability and permanence in model food webs

The dynamical theory of food webs has been based typically on local stability analysis. The relevance of local stability to food web properties has been questioned because local stability holds only in the immediate vicinity of the equilibrium and provides no information about the size of the basin of attraction. Local stability does not guarantee persistence of food webs in stochastic environments. Moreover, local stability excludes more complex dynamics such as periodic and chaotic behaviors, which may allow persistence. Global stability and permanence could be better criteria of community persistence. Our simulation analysis suggests that these three stability measures are qualitatively consistent in that all three predict decreasing stability with increasing complexity. Some new predictions on how stability depends on food web configurations are generated here: a consumer-victim link has a smaller effect on the probabilities of stability, as measured by all three stability criteria, than a pair of recipient-controlled and donor-controlled links; a recipient-controlled link has a larger effect on the probabilities of local stability and permanence than a donor-controlled link, while they have the same effect on the probability of global stability; food webs with equal proportions of donor-controlled and recipient-controlled links are less stable than those with different proportions.     

Stability of biocatalysts

Despite their many favorable qualities, the marginal stability of biocatalysts in many types of reaction media often has prevented or delayed their implementation for industrial-scale synthesis of fine chemicals and pharmaceuticals. Consequently, there is great interest in understanding effects of solution conditions on protein stability, as well as in developing strategies to improve protein stability in desired reaction media. Recent methods include novel chemical modifications of protein, lyophilization in the presence of additives, and physical immobilization on novel supports. Rational and combinatorial protein engineering techniques have been used to yield unmodified proteins with exceptionally improved stability. Both have been aided by the development of computational tools and structure-guided heuristics aimed at reducing library sizes that must be generated and screened to identify improved mutants. The number of parameters used to indicate protein stability can complicate discussions and investigations, and care should be taken to identify whether thermodynamic or kinetic stability limits the observed stability of proteins. Although the useful lifetime of a biocatalyst is dictated by its kinetic stability, only 6% of protein stability studies use kinetic stability measures. Clearly, more effort is needed to study how solution conditions impact protein kinetic stability.     

Population stability is higher in more diverse annual plant communities

Abstract Theoretical work suggests a paradoxical effect of diversity on the temporal stability of ecological systems: increasing diversity should result in decreased stability of populations while community stability is enhanced. While empirical work indicates that community stability tends to increase with diversity, investigations of the effect of diversity on populations have resulted in few clear patterns. Here, we examine relationships between community diversity and population stability in unmanipulated annual plant communities. We show that, counter to theory, the temporal stability of annual plant populations increases with diversity. In addition, and again counter to theoretical assumptions, mean population size tends to increase with diversity, a pattern most likely due to variation in local productivity. The fact that community diversity, population size and the temporal stability of populations covaried positively suggests that abiotic factors such as productivity may govern population stability to such an extent as to override potential effects of diversity.     

Mechanisms underpinning community stability along a latitudinal gradient: Insights from a niche-based approach

At large scales, the mechanisms underpinning stability in natural communities may vary in importance due to changes in species composition, mean abundance, and species richness. Here we link species characteristics (niche positions) and community characteristics (richness and abundance) to evaluate the importance of stability mechanisms in 156 butterfly communities monitored across three European countries and spanning five bioclimatic regions. We construct niche-based hierarchical structural Bayesian models to explain first differences in abundance, population stability, and species richness between the countries, and then explore how these factors impact community stability both directly and indirectly (via synchrony and population stability). Species richness was partially explained by the position of a site relative to the niches of the species pool, and species near the centre of their niche had higher average population stability. The differences in mean abundance, population stability, and species richness then influenced how much variation in community stability they explained across the countries. We found, using variance partitioning, that community stability in Finnish communities was most influenced by community abundance, whereas this aspect was unimportant in Spain with species synchrony explaining most variation; the UK was somewhat intermediate with both factors explaining variation. Across all countries, the diversity–stability relationship was indirect with species richness reducing synchrony which increased community stability, with no direct effects of species richness. Our results suggest that in natural communities, biogeographical variation observed in key drivers of stability, such as population abundance and species richness, leads to community stability being limited by different factors and that this can partially be explained due to the niche characteristics of the European butterfly assemblage.     

湖滨湿地生态系统稳定性评价

根据生态系统稳定性的产生原因,将稳定性划分为系统整体稳定性和系统结构稳定性。从系统的稳定性出发,以生态系统的整体稳定性和结构稳定性两个方面为对象,对湖滨湿地生态恢复所产生的生态效益进行了研究。针对系统整体稳定性,给出了生物多样性指数、自然保护区比重和自然灾害等级3个评价指标,并介绍了相应的指标量化方法。与此同时结合能值理论,准确地分析了湖滨湿地生态系统的结构稳定性,为评价湖滨湿地生态恢复的生态效益评价提供了客观的标尺。     

The stability–diversity relationship in stream macroinvertebrates: influences of sampling effects and habitat complexity

1. Theory predicts that the stability of a community should increase with diversity. However, despite increasing interest in the topic, most studies have focused on aggregate community properties (e.g. biomass, productivity) in small‐scale experiments, while studies using observational field data on realistic scales to examine the relationship between diversity and compositional stability are surprisingly rare. 2. We examined the diversity–stability relationship of stream invertebrate communities based on a 4‐year data set from boreal headwater streams, using among‐year similarity in community composition (Bray–Curtis coefficient) as our measure of compositional stability. We related stability to species richness and key environmental factors that may affect the diversity–stability relationship (stream size, habitat complexity, productivity and flow variability) using simple and partial regressions. 3. In simple regressions, compositional stability was positively related to species richness, stream size, productivity and habitat complexity, but only species richness and habitat complexity were significantly related to stability in partial regressions. There was, however, a strong relationship between species richness and abundance. When abundance was controlled for through re‐sampling, stability was unrelated to species richness, indicating that sampling effects were the predominant mechanism producing the positive stability–diversity relationship. By contrast, the relationship between stability and habitat complexity (macrophyte cover) became even stronger when the influence of community abundance was controlled for. Habitat complexity is thus a key factor enhancing community stability in headwater streams.     

Daytime warming lowers community temporal stability by reducing the abundance of dominant,stable species

Daytime warming and nighttime warming have the potential to influence plant community structure and ecosystem functions. However, their impacts on ecological stability remain largely unexplored. We conducted an eight‐year field experiment to compare the effects of daytime and nighttime warming on the temporal stability of a temperate steppe in northern China. Our results showed that the cover and stability of dominant species, stability of subordinate species, and compensatory dynamics among species strongly influenced community‐level stability. However, daytime, but not nighttime, warming significantly reduced community temporal stability mainly through the reduction in the abundance of dominant, stable species. These findings demonstrate the differential effects of daytime and nighttime warming on community stability and emphasize the importance of understanding the changes of dominant species for accurately predicting community dynamics under climate warming.     

Temporal stability of aquatic food webs: partitioning the effects of species diversity, species composition and enrichment

Theory predicts that species diversity can enhance stability of community‐level biomass while simultaneously decreasing population‐level stability. Enrichment can theoretically destabilize communities but effects may become weaker with increasing diversity because of the inclusion of consumer‐resistant prey. Few experiments using direct manipulations of species diversity have tested these predictions. We used laboratory‐based aquatic food webs to examine the effects of species composition, diversity and enrichment on temporal variability of population‐ and community‐level biomass. We found weak effects of enrichment on population‐ and community‐level stability. However, diversity enhanced community‐level stability while species composition had no influence. In contrast, composition effects outweighed diversity effects when stability was measured at the population level. We found no negative effects of diversity on population‐level stability, in opposition to theory. Our results indicate that diversity can enhance stability in multitrophic systems, but effects vary with the scale of biological organization at which stability is measured.