Anthropogenic Disturbances and the Natural Vegetation Regeneration: A Case Study of a Forest Fragment Located in a Cuesta Relief Area, State of São Paulo, Brazil

Abstract

The present study has been conducted in one of the five natural vegetation fragments at the Experimental Farm Edgardia, in Botucatu, São Paulo State, Brazil. In the past the forest fragment suffered disturbances due to the selective exploitation of tree species and the use of part of the surface as pasture. The objectives of this research were to evaluate the structure and the dynamics of natural vegetation. Three phytosociological surveys (2006, 2010 and 2014) were carried out in a sampled area of one hectare. The most abundant species were mapped in 2014, in a sampling unit with two hectares. Individuals of 37 families and 110 species have been recorded. The oscillation of the basal area observed through the forest inventories was due to the instability caused by disturbances. Only two out of the seven most abundant species mapped showed exponential diameter distribution. The unimodal distributions shown by the other five species have suggested that the vegetation has been occupying the most open spaces through regeneration in cycles. There was direct association between the spatial distribution and the dispersion syndrome for five out of the seven most abundant species. Three species have zoochoric dispersion, showing that wild animals populations have accomplished their function in the dispersion of seeds/fruit. The spatial distributions of four out of the seven most abundant species have provided evidence of how the regeneration of natural vegetation is being processed in this area.

Root parasitism by Scybalium fungiforme Schott & Endl. is not random among host species in seasonal tropical forest

“…With a large number of S. fungiforme individuals sampled and a considerable effort in identifying host plants, we present robust data that indicates a preferential hostthe tree species C. floribundus -and four liana species that can be considered complementary hosts, since, together, these lianas corresponded to only 32 % of parasitized individuals. Supposing no preference at species level, we would expect a much higher host plant diversity among the hosts, considering that in these forests more than 60 tree species have been recorded (Fonseca & Rodrigues 2000;Jorge & Pereira 2015), along with a probably similar number of liana species, which are normally abundant in seasonal tropical forest fragments (Udulutsch et al 2004). Our observations complement the study conducted by Cardoso (2014), which suggested that S. fungiforme does not present a specific host.…”

“…The vegetation of these fragments is classified as seasonal tropical forest, a forest type in which 50-70 % of canopy species shed their leaves during the dry season. Previous studies on these forest fragments have recorded high tree species richness, with 61 species being reported by Fonseca & Rodrigues (2000) and 75 species by Jorge & Pereira (2015). The climate in this region is Cfa (Köppen classification, Alvares et al 2013), characterized by a rainy and warm season from September to April and a dry and cool season from May to August (rainfall below 50 mm), average annual rainfall being about of 1302 mm (Sentelhas et al 2003).…”

“…These differences are likely related to the successional stages of the fragments. In Fragment 1, with a more recent disturbance history, and where pioneer trees are more abundant (Cassola 2008;Jorge & Pereira 2015), the parasite frequency in the tree species C. floribundus was markedly higher than in liana species, though these lianas are also abundant in Fragment 1. Pioneer species tend to dominate communities in early successional stages, and they are replaced by other tree species in a few years, once canopy closure leads to the decline of shade-intolerant species (Brokaw & Scheiner 1989;Tabarelli & Mantovani 1999).…”

“…Fragment 1, with 110 ha (22°49'19.95"S 48°23'31.70"W, at elevation of 505 m), has suffered disturbances in the past, especially selective exploitation of economically important tree species, with the last harvest occurring between 1975 and 1980 (Jorge & Pereira 2015). Fragment 2 comprises 303 ha (22°48'45.38"S 48°24'54.03"W, at elevation of 556 m), presenting a better conservation status than Fragment 1.…”

“…After identifying the main hosts of S. fungiforme, we used previous floristic surveys of the studied fragments (Cassola 2008;Jorge & Pereira 2015) to evaluate the relative abundance of hosts among families observed in each population of the parasite species.…”