Is biotic integrity of urban forests remants related with their size and shape?

Abstract

The Brazilian Atlantic Forest (BAF) is one of the biodiversity hotspots, but in the last decades, it has been fragmented due to agricultural and urban-industrial expansion, which has a strong impact on forest fragments. The goal of this study was to analyze the Biotic Integrity Index (BII) in fragments of BAF in two medium-sized cities in Southeastern Brazil and to analyze the relation between BII and landscape metrics (size and shape). The method (BII) has eleven indicators (litter, grass, dead trees, exotic species, vines, gaps, epiphytes, orchids, palms, later species in canopy and understory). The survey was carried out in nine forest fragments in Ribeirão Preto (SP) and 23 in Sorocaba (SP), with a size variation between 0.33 and 185 ha, all of them in urban influence. The relation between BII and landscape metrics were analyzed by the Pearson regression. BII value was registered from 28.7 to 40.0 to Ribeirão Preto and from 22.34 to 35.34 to Sorocaba. Pearson regression was strong between IBB and the size for both cities (p= 0.742 to Ribeirão Preto, and p= 0.679 to Sorocaba). Pearson regression between IBB and shape was medium to Ribeirão Preto (p= 0.47) and weak to Sorocaba (0.1838). The results showed that there is a strong relation between BII and size, and less correlation between BII and shape. However, only size is not able to explain all variation in integrity, suggesting that other factors such as disturbance history and conservation management should have greater influence than the fragment size.