A Synthesis is Emerging between Biodiversity-Ecosystem Function and Ecological Resilience Research: Reply to Mori

Partitioning resilience of a marine foundation species into resistance and recovery trajectories

The resilience of an ecological unit encompasses resistance during adverse conditions and the capacity to recover. We adopted a 'resistance-recovery' framework to experimentally partition the resilience of a foundation species (the seagrass Cymodocea nodosa). The shoot abundances of nine seagrass meadows were followed before, during and after simulated light reduction conditions. We determined the significance of ecological, environmental and genetic drivers on seagrass resistance (% of shoots retained during the light deprivation treatments) and recovery (duration from the end of the perturbed state back to initial conditions). To identify whether seagrass recovery was linearly related to prior resistance, we then established the connection between trajectories of resistance and recovery. Finally, we assessed whether recovery patterns were affected by biological drivers (production of sexual products-seeds-and asexual propagation) at the meadow-scale. Resistance to shading significantly increased with the genetic diversity of the meadow and seagrass recovery was conditioned by initial resistance during shading. A threshold in resistance (here, at a ca. 70% of shoot abundances retained during the light deprivation treatments) denoted a critical point that considerably delays seagrass recovery if overpassed. Seed densities, but not rhizome elongation rates, were higher in meadows that exhibited large resistance and quick recovery, which correlated positively with meadow genetic diversity. Our results highlight the critical role of resistance to a disturbance for persistence of a marine foundation species. Estimation of critical trade-offs between seagrass resistance and recovery is a promising field of research to better manage impacts on seagrass meadows.

Resilience of aquatic systems: Review and management implications

Our understanding of how ecosystems function has changed from an equilibria-based view to one that recognizes the dynamic, fluctuating, nonlinear nature of aquatic systems. This current understanding requires that we manage systems for resilience. In this review, we examine how resilience has been defined, measured and applied in aquatic systems, and more broadly, in the socioecological systems in which they are embedded. Our review reveals the importance of managing stressors adversely impacting aquatic system resilience, as well as understanding the environmental and climatic cycles and changes impacting aquatic resources. Aquatic resilience may be enhanced by maintaining and enhancing habitat connectivity as well as functional redundancy and physical and biological diversity. Resilience in aquatic socioecological system may be enhanced by understanding and fostering linkages between the social and ecological subsystems, promoting equity among stakeholders, and understanding how the system is impacted by factors within and outside the area of immediate interest. Management for resilience requires implementation of adaptive and preferably collaborative management. Implementation of adaptive management for resilience will require an effective monitoring framework to detect key changes in the coupled socioecological system. Research is needed to (1) develop sensitive indicators and monitoring designs, (2) disentangle complex multi-scalar interactions and feedbacks, and (3) generalize lessons learned across aquatic ecosystems and apply them in new contexts.

Median to Strong Rainfall Intensity Favors Carbon Sink in a Temperate Grassland Ecosystem in China

Over the past 50 years, rainfall events have made significant alterations to environments due to global warming. The grasslands in arid and semi-arid regions are extremely sensitive to variations in rainfall patterns, which are considered to significantly affect ecosystem functions. In this study, an experiment with varying rainfall sizes and frequencies (0 mm, 2 mm, 5 mm, 10 mm, 20 mm, and 40 mm) was conducted during growing seasons in typical grasslands, to study the effect of changes in rainfall regime on net ecosystem exchange (NEE). Our results indicated that NEE exhibited nonlinear responses to rainfall treatments, and reached its peak under 20 mm in middle growing season. Further, the component fluxes of both NEE (i.e., gross primary productivity (GPP)) and ecosystem respiration (ER) illustrated nonlinear responses to treatment gradient, with peak values at 20 mm and 5 mm, respectively. Based on five-year eddy flux measurements, further analyses demonstrated that GPP and ER increased with increasing soil moisture, and net ecosystem carbon uptake (-1*NEE) was significantly stimulated due to a more enhanced GPP than ER, when soil moisture was above 8%. Additionally, we found that the response of root biomass was different from that of carbon fluxes to changes in rainfall patterns. Overall, these findings highlight the importance of both changes in rainfall regimes in controlling ecosystem C exchange and investigation of the potential threshold for ecosystem function shifts, which are crucial to further understand C cycles in grasslands.

Linking Traits across Ecological Scales Determines Functional Resilience

Under globally accelerating rates of ecosystem degradation, maintaining ecosystem function is a priority to avoid loss of valuable ecosystem services. Two factors are important: changes to the disturbance regime (stresses imposed) and resilience of biodiversity and ecosystem functions (the ecosystem's capacity to respond to change). Various attributes at different scales of ecological organisation confer resilience (from individual species to communities at landscape scales), but it is critical to understand how these attributes interact to inform how ecosystem function changes with disturbances that vary in intensity, spatial extent, and frequency. Individual species attributes influence their resistance, while attributes at the landscape-scale influence recovery of communities and function. Understanding resilience to disturbances requires defining the characteristics of a resilient community at multiple scales.

Typical steppe ecosystems maintain high stability by decreasing the connections among recovery, resistance, and variability under high grazing pressure

Grasslands in Inner Mongolia have been confronted with unprecedented degradation in recent years. Research on ecosystem stability is important to inform evaluation of the health of degraded grassland ecosystems. We examined synthetic stability, which was defined by the relationships between multiple components of stability, known as multidimensional stability, in grasslands at four stages of degradation (undegraded, slightly degraded, moderately degraded, and intensely degraded) in the Xilin River Basin, Inner Mongolia, China. We analyzed the connections between multidimensional stability and its relationship with four stability components, including community resistance and recovery measured on the basis of plant functional traits, and community functional (aboveground net primary productivity) and structural (Jaccard dissimilarity) variability, calculated on the basis of ten plots from different spatial distributions in a study site. Our results showed that (i) 9 of 17 traits displayed a significant trend along the grazing intensity gradient, indicating a clear turnover of species within communities in response to the grazing intensity gradient; (ii) moderately degraded (C) grasslands showed higher recovery, resistance, and synthetic stability than undegraded (A) and slightly degraded (B) grassland communities overall (recovery: p = 0.026, p = 0.032, for pairs of samples from A and C, and B and C, respectively; resistance: p = 0.024, for a pair of samples from A and C), which conformed with the intermediate disturbance hypothesis and positive diversity-stability relationship; and (iii) the multidimensionality of stability varied between different stages of degradation and were strongly dependent upon the correlations between stability components. Our study is expected to enrich the theory of stability maintenance in grassland ecosystems and provide guidance for grassland restoration and biodiversity conservation.

Changes in the location of biodiversity-ecosystem function hot spots across the seafloor landscape with increasing sediment nutrient loading

Declining biodiversity and loss of ecosystem function threatens the ability of habitats to contribute ecosystem services. However, the form of the relationship between biodiversity and ecosystem function (BEF) and how relationships change with environmental change is poorly understood. This limits our ability to predict the consequences of biodiversity loss on ecosystem function, particularly in real-world marine ecosystems that are species rich, and where multiple ecosystem functions are represented by multiple indicators. We investigated spatial variation in BEF relationships across a 300 000 m² intertidal sandflat by nesting experimental manipulations of sediment pore water nitrogen concentration into sites with contrasting macrobenthic community composition. Our results highlight the significance of many different elements of biodiversity associated with environmental characteristics, community structure, functional diversity, ecological traits or particular species (ecosystem engineers) to important functions of coastal marine sediments (benthic oxygen consumption, ammonium pore water concentrations and flux across the sediment-water interface). Using the BEF relationships developed from our experiment, we demonstrate patchiness across a landscape in functional performance and the potential for changes in the location of functional hot and cold spots with increasing nutrient loading that have important implications for mapping and predicating change in functionality and the concomitant delivery of ecosystem services.