Edge influence on the microclimate and vegetation of fragments of a north Amazonian forest

Abstract

There are multiple pressures on Amazon forests due to, anthropic activities such as extensive cattle ranching, logging, and legal and illegal crops. These pressures generate highly fragmented landscapes that leads to an increase in forest edges. Thus, forest vegetation exposed to the surrounding open environment generates a series of direct effects that extend into the interior of the forest. Changes in the microclimate are among the most notable effects, and these can impact the composition and structure of the vegetation and affect the alteration of multiple ecological processes and ecosystem services. To better understand these consequences, we evaluated the distance of the edge influence on the microclimate, the composition of the vegetation, and the forest structure in the northern Amazon. We considered two types of edges according to adjacent cover: grasslands dedicated to extensive cattle ranching and rubber plantations (Hevea brasiliensis (Willd. ex A.Juss.) Müll.Arg.). We recorded significant differences in the composition and abundance of plants of all size categories. We found less richness and dominance of generalist species, that are characteristic of disturbed environments, in the forest sector adjacent to pastures. These edges had also lower humidity and higher temperatures than rubber plantations ones. The distance from the edge to the interior also affected the structure of the vegetation, with a higher density of individuals in the interior of the forest and significant differences in the diameter and height of individuals. We argue that the rubber plantations could be used as a forest management strategy of drought adaptation since it forms a less abrupt border and has a buffer function, keeping higher humidity values and lower temperatures than forest edges adjacent to pastures.