Eficiência no uso dos nutrientes por espécies pioneiras crescidas em pastagens degradadas na Amazônia central (Nutrient use efficiency of pioneer species grown on abandoned pastures in central Amazonia)

Large areas of Amazonian forest have been converted to pastures over the last two decades. Low soil fertility and mismanagement results in a rapid decline in net primary productivity leading the pastures to be abandoned, and woody vegetation adapted to low nutrient conditions colonize the areas. The objective of this study was to examine nutrient use efficiency, following liming (calcium) and phosphorus addition by three of the most frequent colonizing species. The experiment conducted on a six year-old secondary forest, consisted of four treatments: control; phosphorus addition (P); phosphorus and lime addition (P+Cal); and phosphorus, lime and gypsum addition (P+Cal+G). Leaf gas exchange, soil and leaf nutrient concentration were determined eight months after the treatment application. There was a significant response by species to the addition of phosphorus and lime (P+Cal and P+Cal+G). The species, Bellucia grossularioides accumulated more N, P and Zn in the leaves, while Laetia procera accumulated more Ca and Mn. The species Vismia japurensis had higher nutrient use efficiency, as a function of the higher photosynthetic rates. Vismia japurensis presented lower P concentrations than Bellucia grossularioides, suggesting that is well adapted to environments low in nutrients, as this species often occurs in degraded areas in Amazonia.