Seed dormancy in tree species of the Tropical Brazilian Atlantic Forest and its relationships with seed traits and environmental conditions

Abstract

So far data in the literature indicate that (1) the relative proportion of tropical species with dormant versus non-dormant seeds tends to increase with a decrease in temperature and precipitation, (2) in rain forests, more species with non-dormant seeds have been found, (3) in rain forests, physiological dormancy is normally the most common type of seed dormancy, (4) the reasons why rain forests have species with dormant seeds are not well known, and studies have been done to determine if there is a relationship between the presence of dormancy in seeds with seed characteristics and environmental conditions of rain forests, and (5) it has been suggested that seed dormancy type could be connected to seed dispersion. The purpose of this work was to test, by compiling data from the literature for 162 woody species from the Atlantic Rain Forest of Brazil, the proportion of species with non-dormant and dormant seeds, and to determine if dormancy and the classes of dormancy of these species are associated with plant successional status, light environment, seed mass, and seed dispersal. The results found were (1) approximately 60 % of species had non-dormant seeds, and 40 % of species had dormant seeds, (2) physical and physiological dormancies were present in similar proportions, and combinational dormancy was the least common class of dormancy, (3) it was found that the chance that a species has physical or physiological dormancy doubles if it is a species found in a sunny environment, (4) a relationship between seed dormancy and non-dormancy, and the successional group of the species, was not found, (5) physical dormancy was highest in the non-climax group, and physiological dormancy occurred in similar proportions in non-climax and climax groups; however, a relationship was not found between class of succession and class of dormancy, (6) the proportion of the dispersal classes shows predominance for zoochory, followed by anemochory and autochory, (7) a multiple logistic regression analysis suggests that if the seeds are spread by autochory, then the chance that the seeds have physical dormancy is about eight times greater, and (8) seed mass was not associated with the presence or absence of dormancy; however, the species with physiological dormancy had seeds with smaller masses than those with physically dormant seeds. In short, for the Atlantic Rain Forest, based in compiled data from literature, it was found that seed dormancy type was related with sunny environments, dispersion, and seed size.