Landscape forest loss changes sunfleck dynamics in forest fragments of southern Bahia, Brazil

Abstract

Landscape-scale habitat loss can change the floristic composition of forest fragments, affecting the survival of specific groups of plants, as shade-tolerant and emergent trees. This increasing in tree mortality creates forest canopy gaps of different sizes that ultimately determine the solar radiation available in the forest understorey. We conducted a study aiming to assess how the loss of forest cover at landscape level (i.e. deforestation) affects the sunfleck dynamics, a proxy of light regime in forest understorey. We expected that fragments located in landscapes with less forest cover have a high number of larger canopy gaps and, consequently, long-lasting sunflecks. In each forest fragment, a 100 per 50 m plot was established, and in each plot, we took 10 hemispherical photographs. The images were analysed using the Gap Light Analyzer software. The sunflecks were divided into six temporal classes. We evidenced that landscape-scale deforestation increased the frequency of all sunfleck intervals >8 min, particularly the long-lasting (> 32 min) sunflecks. We propose that the increasing frequency of long-lasting sunflecks reduces suitability of microhabitat to some shade-tolerant species in local fragments, a potential proximal mechanism contributing to compositional shifts of tree assemblages observed in forest fragments within deforested landscapes.

Tropical forest loss impoverishes arboreal mammal assemblages by increasing tree canopy openness

“…Our results suggest that species richness decreases with forest loss through the increase of tree canopy openness. Other studies have also found that forest loss increases the size of canopy gaps and light incidence within forest patches, which can in turn decrease microhabitat suitability for shade‐tolerant and animal‐dispersed trees (Mascarenhas‐Lima & Mariano‐Neto, 2014 ; Reis et al, 2021 ). Deforestation can also increase the susceptibility of tree stands to wind damage (Zeng et al, 2009 ) and tree mortality caused by desiccation (Briant et al, 2010 ), which can increase tree mortality and gap formation within the remaining forest patches.…”

“…Both deforestation and fragmentation decrease the size of forest patches in anthropogenic landscapes (Fahrig, 2003 ), and there is evidence that edge effects can alter vegetation structure, particularly in smaller forest patches (Arroyo‐Rodríguez & Mandujano, 2006 ; Laurance et al, 2006 ; Santos et al, 2008 ; Tabarelli et al, 2012 ). For instance, reduced forest cover in a landscape can increase the size of canopy gaps and light incidence in forest patches, which in turn decreases microhabitat suitability for shade‐tolerant trees (Reis et al, 2021 ). Additionally, short‐lived pioneer trees and lianas can proliferate along patch edges (Arroyo‐Rodríguez & Toledo‐Aceves, 2009 ; Laurance et al, 2006 ), while the mortality of old‐growth tree species can increase in small patches (Laurance et al, 2000 ).…”