Produção de serapilheira em floresta Atlântica secundária numa paisagem fragmentada (Ibiúna, SP): importância da borda e tamanho dos fragmentos

Abstract

-(Litter production in a fragmented Atlantic forest landscape (Ibiúna, SP): the importance of the edge and fragment size). Litter is an important compartment in tropical forests, responsible for most of nutrient cycling. Several environmental factors may affect litter production, and the ones mostly investigated are climate and vegetation structure. The influence of landscape structure on patterns of litter production is poorly studied. This study investigated edge and size effects on patterns of litter production in three Atlantic forest fragments (Ibiúna, SP: 23°35' S -23°50' S; 46°45' W -47°15' W), one large (ca. 175 ha) and two small (ca. 5 ha) with different degrees of isolation. The litter collected was fractioned following the predominant plant material, and grouped into two periods, of high and low production. We used analysis of variance and a posteriori tests to detect differences in litter production between edge and center of each fragment, and among the centers of the three fragments. Most biomass consisted of "leaves+flowers", followed by "twigs £ 0.5 cm" (62.9% and 24.7% of the total), a common pattern in tropical forests. It was possible to perceive an edge effect related to litter production in the three fragments, especially in the large one, and higher litter production in their centers. The observed patterns showed to be strongly related to the vegetation structure, as the size of trees and canopy density. A higher production of "fruits+seeds" in the large fragment or in the small and connected one indicate a relationship between forest connectivity and the activity of disperser animals.Key words -habitat fragmentation, landscape structure, litterfall, litter production, Plateau Atlantic forest RESUMO -(Produção de serapilheira em floresta Atlântica secundária numa paisagem fragmentada (Ibiúna, SP): importância da borda e tamanho dos fragmentos). A serapilheira constitui um importante compartimento florestal, principal responsável pela ciclagem dos nutrientes. Diversos fatores podem afetar a produção de serapilheira, sendo os climáticos e a estrutura da vegetação os mais comumente investigados. Também a estrutura da paisagem pode influir nos padrões de produção da serapilheira, abordagem ainda muito pouco explorada. Este estudo objetivou avaliar efeitos de borda e de tamanho na produção de serapilheira em três fragmentos de Floresta Atlântica de Planalto (Ibiúna, SP: 23°35' S -23°50' S; 46°45' W -47°15' W), um grande (aproximadamente 175 ha) e dois pequenos (aproximadamente 5 ha), com diferentes graus de isolamento. A serapilheira coletada foi separada em frações, conforme os órgãos vegetais predominantes, e em dois períodos, conforme maior ou menor produção. Foram utilizadas análises de variância e testes a posteriori para detectar diferenças na produção de serapilheira entre borda e interior de cada fragmento, e entre os interiores dos três fragmentos analisados. A maior biomassa foi de "folhas+flores", seguida de "caules £ 0,5 cm" (62,9% e 24,7% do total), padrão comum em floresta...

Produção de serrapilheira e decomposição foliar em fragmentos florestais de diferentes fases sucessionais no Planalto Atlântico do estado de São Paulo, Brasil

“…In this context, smaller fragments were less heterogeneous, which was likely due to edge effects, such as wind and temperature, in a relatively higher proportion of the fragment when compared with larger fragments, once edge effects can propagate hundred meters into the forest (Laurance 2000). The exception to this would be observed in forests at an advanced successional phase due to their greater biomass and a more closed canopy (Werneck et al 2001, Nascimento & Villela 2003, Vidal et al 2007). The greater biomass produced in ES-1 may be associated to a high biomass of pioneer species, given the fact that in this fragment 36.8% of the total basal area corresponded to pioneer species, when compared with the others fragments where this proportion were quite smaller (Table 1).…”

“…Litterfall may peak in dry periods in forests with higher water restriction (Dantas & Phillipson 1989, Sanchez & Alvarez-Sanchez 1995, Barlow et al 2007 or alternatively in wetter period in forests with lower water restriction as in the Atlantic Forest (Leitão-Filho et al 1993, Pinto & Marques 2003, Vidal et al 2007). The pattern of higher deposition of litter in the rainy season may be Biota Neotrop.,vol.…”

“…For example, proximity to preserved forest areas may speed up the successional process because the preserved forests may serve as a source of propagules for the fragment (Brown & Lugo 1990). In this context, the controversial pattern of litterfall in Atlantic forests (higher amounts of litter production in later successional phases (Vidal et al 2007, Scheer et al 2009), or alternatively higher litterfall in early succession phases (Leitão-Filho et al 1993) or even the absence of differences in litterfall between fragments of different successional phases (Barlow et al 2007, Dickow et al 2012, may be related to the divergent structures and historical disturbance of the forest fragments studied. Fragments ES-1 and ES-2 showed no differences in litter production, which was likely due to their similar structure (Jurinitz (2010)).…”

“…Thus, litter production is expected to increase with forest development (Vidal et al 2007). The amount of litter input, in turn, influences the composition of the decomposer community and associated with the drier microclimate conditions, typical of early successional forest fragments, can reduce the activity of decomposers (Bradford et al 2002), resulting in a less efficient nutrient cycling.…”

“…12,no. 3 on ecosystem processes are still poorly understood (Vasconcelos & Luizão 2004, Vidal et al 2007, Ostertag et al 2008. Thereby, this study aimed to evaluate how litterfall and nutrient cycling are affected by the structure of forest fragments at different successional phases under similar climatic conditions on the Atlantic Plateau of the state of Sao Paulo, Brazil.…”