How may agricultural matrix intensification affect understory birds in an Atlantic Forest landscape? A qualitative model on stochasticity and immigration

摘要

Understanding how different approaches of matrix management affect organisms that inhabit natural patches is crucial for biological conservation. Considering that great part of the tropical area is composed of agricultural land and that most of the land use is either intensified or on the verge to be, a relevant question is: how may agricultural intensification of the landscape matrix affect the population dynamics of understory birds? This paper describes a qualitative model based on the Qualitative Process Theory and implemented in Garp3 to provide answers to this question. We built a model using four species of endemic passerine birds in order to evaluate the case in an Atlantic Forest area, a biodiversity hotspot. The model describes a landscape composed of an extinction-resistant source patch and one target forest patch where stochastic events occur. If permeability of the matrix exceeds a given species-specific threshold, propagules coming from the source reach the target patch. Agriculture intensification affects the matrix spatial structure and reduces permeability to forest birds, thus reduces rescue effect. Additionally, we assume that some species may use the matrix as a supplementary habitat for feeding and that matrix management may affect the resource base for those species. Simulation results suggest that, if agriculture intensification continues to threat the Atlantic Forest biome, populations of sensitive species (Xiphorhynchus fuscus and Sclerurus scansor) that exist in the small forest patches (which is true for most forest remnants) will be highly susceptible to local extinctions and without further re-colonization.