DYNAMICS OF SEED IN REMAINING OF SUBTROPICAL SEASONAL FOREST

ABSTRACT

The aim of this study was to evaluate the dynamics of the seed rain in two Floristic groups formed in a remnant of Subtropical Seasonal Forest. The clusters were characterized by successional stage of the forest, namely group I (Secondary Forest in Intermediate Stage-FSEM), with a predominance of early secondary species, and group II (Secondary Forest in Advanced Stage-FSEA), with a predominance of late secondary species. Seed rain was evaluated in 70 collectors of 1 m², randomly distributed in the two groups, whereas in group I were installed 15 collectors and in group II, due to its greater area, 55 collectors. The deposited material was collected monthly from October 2008 to October 2010. The dynamics of seed rain was assessed by the density of seeds of each species of dispersal and seasonal production. We used the nonparametric Test of Wilcoxon Sum of Orders (W) to determine statistical differences in the mean density of seeds in each year of assessment for each patch of forest. Seed rain in the remaining studied during three years of study, was represented by 114 species and higher seed production occurred in 2008 (1632-seeds.m^-2 in group I and 1270-seeds.m^-2 in group II), mainly due to the occurrence of high production Chusquea ramosissima Lindm., Dasyphyllum spinescens (Less.) Cabrera, Vernonanthura discolor (Spreng.) H.Rob. Only in the second year (2009) observed statistical differences in mean density between the two groups (FSEM=565.6 seeds.m^-2 and FSEA=274 seeds.m^-2; Z=1.96 and tabulated; W FSEM x FSEA =2.248). Zoochorous species predominated in the study area, and periods of increased seed production were the winter and spring. The seed rain proved important mechanism for natural regeneration of remnant forest and is affected by climate conditions and successional stage of the forest.

Keywords:
forest succession; dispersion syndrome; seasonality of production.