Urbanisation effects on the functional diversity of avianagricultural communities

摘要

Urbanisation is affecting ecological communities worldwide. Despite the disproportionate impact onfarmland over other habitats, the effect on farmland bird communities has been poorly studied.Considering the still-alarming conservation status of farmland birds, investigations into the effects ofpressures such as urbanisation on those communities could be of great interest for their conservation.We studied the urbanisation effects on functional diversity using existing indices designed for thepurpose of standardisation. This study uses a functional character measuring species habitat speciali-sation for indices calculation. A bird survey was conducted on 92 plots of 1 × 1 km chosen after strat-ification on the proportion of urban area and farmland habitat (either 0, 25, 50, 75%), with the focus onfarmland habitat. Two aspects of urbanisation were studied: the intensity and the age of the urbanisa-tion. Functional richness was found to decrease with urbanisation, while functional evenness anddivergence increased in a nonlinear way. No significant difference was observed in functional richnessand evenness with urbanisation age, however extreme ages of urbanisation (young and old) showedhigher niche differentiation concerning specialisation. This implies less important resource competitionfor species and a more vulnerable state for the ecosystem. Using functional diversity indices based onspecialisation allows a better insight in the consequences of urbanisation on diversity/ecosystem-community functioning, which is of crucial importance in the face of global changes.