Population ecology of Psychotria suterella Mull. Arg. (Rubiaceae) in fragmented Atlantic rainforest landscape / Ecologia de populações de Psychotria suterella Mull. Arg. (Rubiaceae) em uma paisagem fragmentada de Mata Atlantica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

There is wide variation in the sensibility levei of plant populations to the decrease of their natural habitats. There are also few studies in priority conservation areas. The objective of this study is to test if the discontinuity and quality of the Atlantic Rainforest affect the structure, alometric relations, dynamics, and seed germinability of the populations of a common understory specie, Psychotria suterella (Rubiaceae). Nine populations of the species were sampled in three areas of continuous forests, three connected fragments, and three isolated fragments, in a landscape of fragmented Atlantic Rainforest in São Paulo State, southeastern Brazil. The density of individuais was smaller and the mortality rate of the isolated fragments was higher. All the populations presented a clustered spatial pattern except for a population of one isolated fragment which presented random distribution. The smaller populations presented higher growth, higher mortality rate, and higher recruitment rate. The ditTerences found in the recruitment rates between the populations have no apparently relation with the seeds germination. The germination percentage was not different among the populations. Mortality increased because the intraspecific density also increased. The negative growth increased with the increase of the damage percentage in the individuais. lndividuals of different size class appeared to be affected in the opposite way to the analyzed factors. The proportion of small individuais was higher according to a decrease on the size of the fragment, on increase of the canopy openness, and antropic disturbance. lt worked opposite with larger individuais. Smaller individuais presented a higher mortality rate and higher growth when compared to bigger individuais. ln small scale the density and light conditions affect the alometric relations of individuaIs. ln large scaIe populations with Iow density of individuaIs and higher light conditions may vary a lot in their way of growth. Ali the popuIations presented populational decline. The populations growth rate (À.) varied among areas and in time. For the majority of populations À. was less than 1. The stasis class contributed to the À. values. The contributions of transitions for the change of size class (growth and regression) presented little contribution to À.. The populational growth rate (À.) did not differ among the continuous forest populations and the fTagments. The contribution to /).À. in stasis varied considerably among the sampled years. In the fTagments there was higher probability of individuaIs to get to a class of larger size. In the continuous forest there was higher probability of individuaIs to decrease in size. The combination of different factors may alter the abundance and structure of the Psychotria sllterella populations. In extreme situations these alterations may be negative. The wide variation in time of the dynamics rate may show demographic stocasticity. The slow populational decline of the populations in the landscape may indicate the possibility of extinction of some populations in the long termo

ASSUNTO(S)

ecologia vegetal biologia - população vegetation ecology mata atlantica mata atlantica (brazil) population biology psychotria

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