Influência do entorno sobre a chuva de sementes e deposição de serrapilheira em fragmentos de floresta atlântica

Abstract

The different use of the land in the surroundings of the forest fragments, can impel changes in the landscapes due to the abiotic and biotic changes. Depending on the type of use, for example, sugarcane monoculture and urban centers, the predominant landscape matrix in which the fragments are inserted may induce deleterious changes in environmental conditions and propel selective filters such as temperature increase of the environment and soil and air pollution on the flora, being able to generate changes in species richness, seed density, floristic composition, functional attributes of the seed rain and the litter mass. Mainly because, such filters can act for or against some species according to their functional characteristics. The main objective of this thesis was to evaluate if the type of environment of the rural and urban fragments of Atlantic rainforest will influence the behavior of the seed rain and the litter deposition. Rural and urban fragments in the Metropolitan Region of Recife had their surroundings mapped for the quantification of rural and urban areas and definition of the collection area: fragment with rural surroundings and with urban surroundings. In these areas, it was evaluated whether species richness, seed density, floristic composition and functional attributes of habit, dispersion syndrome and successional category of seed rain differ between fragments (rural and urban), seasons (dry and rainy ) and years (2015 and 2016). We also analyze if litter deposition and its fractions differ between fragments and seasons, and if they present a negative correlation with precipitation totals occurring in each year. To sample the seed rain and the litter supply, 36 collectors of 0.25 m2 were distributed in each fragment, distributed in three transects of 300 m, interspersed at 100 m distance. In each transect, 12 equidistant collectors were installed at twenty-five meters. Monthly from February 2015 to January 2017 were collected the seed rain and litter. The seeds were classified as dispersion syndrome and the species were calsified for habit and successional category. The litter was sorted in the fractions leaf, twig, seed and miscellaneous. With the development of the study, it was possible to respond to the specific objectives as follows: For Chapter I, it was observed from the accumulation curves of species that the richness of the seed rain was higher in the urban fragment in the two years and in the rainy season, while that in the dry season the richness was similar among the fragments. The seed density, evaluated by the GLM analysis, was higher in the rural fragment than in the urban rainy season, did not differ in urban between years and between seasons, and in rural areas, it was higher in the rainy season of only one year. The NMDS recorded differences in the floristic composition of the seed rain between the fragments over time (years and seasons). The Log Linear Model showed that the variation in the functional attributes of habit, dispersion syndrome and successional category were explained by the variables fragments, seasons and years. For chapter II, it was verified by the GLM analysis that the total litter mass and fractions (leaf, twig and seed) were significantly higher in the rural and dry season, except for the seed fraction in the urban area, which did not present seasonal variation. The Simple Linear Regression test showed that leaf deposition in the rural and urban fragments increased with the reduction of water availability, and an increase in seed deposition was also observed with the reduction in precipitation in the urban fragment. This scenario indicates that: the surrounding landscape may have provided changes in the local abiotic characteristics within the fragments that limited the presence of some species, promoted the entry of propagules within them and induced a greater contribution of litter in the rural fragment. Thus, the results show that disturbance measures (sugar cane monoculture and urban centers) can be effectively used to evaluate the impacts of land use in studies of seed rainfall and litter deposition, especially when has the purpose of comparing urban and rural fragments with different environments inserted in the same landscape.