Species richness and asynchrony maintain the stability of primary productivity against seasonal climatic variability

Plant phenology response to nitrogen addition decreases community biomass stability in an alpine meadow

Phenology is a sensitive indicator of plant responses to environmental changes, and its shifts could impact community structure and function. However, the effects of phenological shifts on community stability are poorly understood. We conducted a 4-yr N enrichment and precipitation change experiment to assess their effects on community stability through phenological responses. To do so, we measured phenological duration and overlap (based on leaf-out and flowering phenology of 55 species) in an alpine meadow on the Tibetan Plateau. N enrichment extended the vegetative stage of grasses, sedges, and community by 4.62, 4.72, and 11.74 d, respectively, but shortened that of forbs by 6.14 d and increased the overlap of flowering among individuals within the community. Meanwhile, N enrichment decreased species richness, asynchrony, and stability of sedges. Furthermore, N enrichment decreased community stability by decreasing asynchrony but was not associated with richness. Interestingly, N enrichment also decreased sedges stability by extending their vegetative stage and increasing the overlap of flowering, consequently reducing community stability. Our findings imply that N enrichment reduces phenological compensation and thus threatens grassland stability, which highlights the importance of phenological niches in understanding the maintenance of grassland stability under ongoing climate change.

Asynchrony in terrestrial insect abundance corresponds with species traits

Asynchrony in population abundance can buffer the effects of environmental change leading to greater community and ecosystem stability. Both environmental (abiotic) drivers and species functional (biotic) traits can influence population dynamics leading to asynchrony. However, empirical evidence linking dissimilarity in species traits to abundance asynchrony is limited, especially for understudied taxa such as insects. To fill this knowledge gap, we explored the relationship between pairwise species trait dissimilarity and asynchrony in interannual abundance change between pairs of species for 422 moth, butterfly, and bumblebee species in Great Britain. We also explored patterns differentiating traits that we assumed to capture 'sensitivity to environmental variables' (such as body mass), and traits that may reflect 'diversity in exposure' to environmental conditions and lead to niche partitioning (for example, habitat uses, and intra-annual emergence periods). As expected, species trait dissimilarity calculated overall and for many individual traits representing response and exposure was positively correlated with asynchrony in all three insect groups. We found that 'exposure' traits, especially those relating to the phenology of species, had the strongest relationship with abundance asynchrony from all tested traits. Positive relationships were not simply due to shared evolutionary history leading to similar life-history strategies: detected effects remained significant for most traits after accounting for phylogenetic relationships within models. Our results provide empirical support that dissimilarity in traits linked to species exposure and sensitivity to the environment could be important for temporal dissimilarity in insect abundance. Hence, we suggest that general trait diversity, but especially diversity in 'exposure' traits, could play a significant role in the resilience of insect communities to short-term environmental perturbations through driving asynchrony between species abundances.

Effects of intra-annual precipitation patterns on grassland productivity moderated by the dominant species phenology

Phenology and productivity are important functional indicators of grassland ecosystems. However, our understanding of how intra-annual precipitation patterns affect plant phenology and productivity in grasslands is still limited. Here, we conducted a two-year precipitation manipulation experiment to explore the responses of plant phenology and productivity to intra-annual precipitation patterns at the community and dominant species levels in a temperate grassland. We found that increased early growing season precipitation enhanced the above-ground biomass of the dominant rhizome grass, Leymus chinensis, by advancing its flowering date, while increased late growing season precipitation increased the above-ground biomass of the dominant bunchgrass, Stipa grandis, by delaying senescence. The complementary effects in phenology and biomass of the dominant species, L. chinensis and S. grandis, maintained stable dynamics of the community above-ground biomass under intra-annual precipitation pattern variations. Our results highlight the critical role that intra-annual precipitation and soil moisture patterns play in the phenology of temperate grasslands. By understanding the response of phenology to intra-annual precipitation patterns, we can more accurately predict the productivity of temperate grasslands under future climate change.