Seasonality and Grazing Exclusions Shape Bird Community Dynamics in West African Drylands

Résumé fourni par la source

Dryland ecosystems are highly vulnerable to climate change and anthropogenic disturbances, leading to land degradation and biodiversity loss. Grazing management, including livestock exclusion, is widely used to restore vegetation, yet its effects on the spatiotemporal dynamics of species communities remain poorly understood. Here we studied variations in bird species composition (i.e., beta diversity)-a key indicator group of habitat restoration-between grazing exclusions and control sites over time in the seasonally dynamic Sahel region in Burkina Faso, West Africa. Bird communities were surveyed with passive acoustic monitoring in 25 small-scale grazing exclusions and 50 control sites across two contrasting seasons. Seasonal effects were assessed by comparing the composition of bird species vocalization and vegetation parameters between dry and wet seasons. We conducted beta diversity analyses to measure the variation in species composition within and between grazing exclusions and control sites, and determined which vegetation parameters, derived from field inventories and remote sensing, best explained bird species spatial and seasonal turnover. The composition of bird species was more influenced by seasonal changes in the vegetation structure and productivity than by grazing exclusions. Moreover, bird communities within the grazing exclusions were more homogeneous than those in the control sites. Yet, grazing exclusions served as important refuges for birds during the dry season, presumably because they maintained a higher vegetation cover than the control sites throughout the year. Furthermore, high tree diversity and structurally complex vegetation promoted bird species turnover on a landscape-scale. Due to its strong influence on bird communities, seasonality should be integrated into biodiversity monitoring and restoration planning of arid ecosystems. Although grazing exclusions were not the primary driver of community composition, they enhanced habitat heterogeneity, supporting regional bird biodiversity and providing refuges that mitigate the effects of overgrazing in this region of the Sahel.

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