Reduced temporal turnover in carabid communities enhances biomass stability in agricultural landscapes

While the temporal stability of plant communities has been well investigated, almost nothing is known about the inter-annual stability of arthropod communities, especially those inhabiting highly disturbed habitats such as croplands. We investigated the effects of landscape, management and community drivers on the temporal carabid biomass stability and its mean in agricultural landscapes. The dataset was composed of carabids collected in 57 arable agroecosystems from three areas in France excluding pastures and managed under organic, conservation or conventional farming. Data also included local- and landscape-level management descriptors. Through a piecewise structural equation modelling approach, we tested the effects of landscape- and field-level management intensity and variability, richness and compositional carabid community metrics such as mean α-richness, standard deviation α-richness, β-diversity and asynchrony on carabid biomass stability and mean value. The temporal stability of the carabid biomass increased as temporal β-diversity of the carabid community decreased and asynchrony among species increased. Furthermore, β-diversity decreased and asynchrony increased with the community's mean α-richness. At the landscape level, diversifying crop phenology and reducing the proportion of cropland appear to be the most efficient way to support carabid biomass stability. The effect of α-richness on carabid biomass stability tends to be modulated by species composition. However, this study underscores the need to investigate the relative effects of temporal β-diversity and asynchrony on the stabilisation of ecosystem functioning in real ecosystems, as the reasons for their lack of covariance and similar effects remain unclear.