Impact of agricultural practices on carabid communities and the associated ecosystem services in Wallonia

Details

Supervisors

Hance, Thierry ; Jamar, Daniel ; Gyselynck, William

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

Intensive agriculture has raised yields dramatically, but this way of farming is today questioned, notably because of its major environmental impacts. Among the new ways of farming, we can cite biological agriculture, conservation agriculture and biological agriculture of conservation. The first one notably prohibits the use of synthetic pesticides, the second one imposes reduced tillage, permanent vegetative cover and crop rotation, and the third one combines the two previous ones. Those more sustainable forms of agriculture are highly dependant on some ecosystem services like pest predation. Carabids are very studied Coleoptera that can provide those ecosystem services. For this work, we have collaborated with the CRA-W to determine the effect biological agriculture, conservation agriculture and biological agriculture of conservation had on carabid communities in 12 Walloon fields. We have identified a part of the carabids sampled during a preceding campaign that occurred in 2020 and realised a new sampling campaign from early March to late June 2021. The dry mass of a part of the captured individuals was also determined, and the effect of tillage on dry mass of individuals >6mm was evaluated as well. During the 2020 campaign, carabids were trapped with pitfall traps, while two trap designs, pitfall traps and emergence traps, were used and compared during the 2021 campaign. Communities were characterized by their specific abundances, total biomass, as well as the diet and phenology of the species constituting it. We have realised multivariate analyses (PCA, FCA, CCA, fuzzy coding FCA) to determine the effect on carabid communities of some agricultural practices (modality, tillage and crop) and parameters relative to the site (site, region) for the samplings of both years. In addition to these parameters, the analyses on the 2021 samplings also included the sampling date and the type of trap used. We have demonstrated that individual dry mass of Nebria salina was more important when tillage was more superficial. Multivariate analyses showed that the site itself was generally the most important source of variation. Furthermore, they indicated that generalist predators were proportionally more abundant in conservation agriculture plots, while granivorous and omnivorous were present in higher proportion in plots under biological agriculture. This difference might be due to several factors such as a more important use of herbicides in conservation agriculture that would deprive some granivorous and omnivorous of food or suitable habitats, the greater sensitivity to tillage of some large generalist predators like Pterostichus melanarius or even interspecific interactions. We can therefore assume a better predation of animal pests in conservation agriculture and a better weed control in organic agriculture, but this conclusion remains to be verified. Biological agriculture of conservation, as for it, has more evenly distributed proportions of generalist predators and of granivorous and omnivorous. Emergence traps captured less carabids than the pitfalls did, but a higher proportion of species with lower individual biomass. They thus do not seem subject to activity biases reproached to pitfalls. The work will end by some propositions to improve the experimental design.