Vialatte, A. | bioRxiv Science

bioRxiv2026

Carabid beetle communities along a gradient of agroecological systems: disentangling the roles of pesticides and soil tillage

The potential of alternative agricultural systems, such as organic or conservation agriculture, for biodiversity restoration has been widely investigated. However, variability of practices within each of these two categories of agricultural system has rarely been accounted for. Furthermore, these systems have most often been studied separately, isolating either organic or conservation agriculture (itself often reduced to a soil tillage reduction), and rarely analyzing these systems side by side. This study attempts to disentangle these multiple interrelationships by sampling carabid beetles in a network of 48 commercial Belgian farms including organic agriculture (OA), conservation agriculture (CA), farms combining the two approaches (OCA) and farms applying conventional practices (CVA). In each farm, we sampled carabids using pitfall and emergence traps in one winter cereal field and collected a detailed description of crop management practices. We found that community composition was primarily structured by seasonality early in the season (March, April) followed by convergence (May, June) driven by the aggregation of the most dominant species. Based on agroecosystem classification, organic certification (i.e., the absence of synthetic pesticide use) exerted a twofold stronger effect than application of conservation agriculture principles (i.e., reduced or no soil tillage) on carabid beetle community composition. Notably, OCA supported carabid assemblages that were structurally distinct from those of CA and CVA. Furthermore, carabid communities associated with OA differed significantly in composition from those of CVA. Observed and estimated species richness were also significantly higher in OCA than in CA and CVA, while OA differed from CVA only for observed richness. Beyond differences among agricultural systems, community responses were associated with specific management practices, which explained nearly a quarter of the compositional variation with significant influence of the duration since organic conversion and the frequency of synthetic pesticide application. Carabid abundances were negatively affected by synthetic pesticides and moldboard ploughing, whereas richness was more strongly related to the time since conversion to OA, cover crops, and organic amendments. Overall, these results position synthetic inputs and time since conversion as the main filters over carabid communities. Our study highlights the importance of jointly considering system level analyses and detailed management practices to better understand the complex relationships between agricultural practices and carabid communities.

ecology↗

bioRxiv2022

Converting cropping systems into seasonal habitat functionality reveals the hump-shaped responses of carabid beetles to agricultural management

O_LIUnderstanding effects on the huge diversity of cropping systems on local biodiversity is challenging but necessary to implement agroecological systems. Through a functional approach, the translation of cropping systems into resource and disturbance gradients is promising to decipher the relationship between cropping systems and biodiversity but has never been implemented for arthropods. C_LIO_LITo investigate contributions of resource and disturbance gradients arising from cropping systems vs environmental context (regional effect, meteorological conditions and landscape characteristics) on beneficial arthropod communities, we used a dataset collected in 60 crop fields from three French areas over a five-years period. It includes all farmers interventions, crop sequences, meteorological data, landscape composition and carabid samplings. C_LIO_LIWe found that the environmental context contributed to about 75% of explained carabid variations on average, while resource and disturbance gradients contributed to about 25% of explained carabid variations. The resource and disturbance gradients were particularly important in winter and spring preceding the spring-summer period to determine carabid variations. C_LIO_LIMoreover, we identified thresholds above which resource and disturbance gradients start being beneficial or detrimental for carabids. For example, a Treatment Frequency Index above 2.07 in spring decreased the total activity density of carabids during the spring-summer period. C_LIO_LISynthesis and application. While implementing for the first time a functional approach to understand the effects of different facets of cropping systems on arthropods, our study also allows us to identify periods and thresholds above which specific practices affect carabids. The identification of such thresholds can guide the provision of recommendations for policy, stakeholders and farmers about how to reduce cropping systems impact on arthropods. C_LI

ecology↗