Nitrogen Nutrition in Dry Tropical Forest at Different Times of Regeneration

The management of forest species requires the quantification of various nutrients flows in the ecosystem. Specifically for N this aspect is even more important because many species in dry forests, as Brazilian Caatinga, are legumes and in symbiotic association with diazotrophic bacteria, fix N2 from the atmosphere. This study aimed to evaluate the N nutrition of forest species in Caatinga fragments with different regeneration times in the semi-arid region of Brazil. The study areas had different historical uses: the first one (53 ha) had no exploitation in the last 44 years; the second (32 ha) was in regeneration for 25 years; and the third (25 ha) had been in regeneration for five years. Four common tree species were evaluated in the three evaluated areas. Leaves were collected from each species to determine N contents. The legume species in the preserved area presented higher N content, decreasing with the regeneration time. The results showed a greater ecological balance in the most preserved sites, favoring the biological N fixation. N acquisition by legumes was not influenced by the disturbance of the site, suggesting the recommendation of these species as restorers of degraded areas.