Biomass above-ground and nutrients in caatinga arboreal species, Rio Grande do Norte

The objective of this work was to quantify the aboveground biomass, the NPK nutrient contents and estimate the carbon stock of native species from the Caatinga, in the municipality of Upanema (RN). To select the species evaluated, a forest inventory was carried out in the area, using sampling units of 400 m(2), in which all individuals with CAP >= 6 cm were measured and, based on the information found, the species were selected. For biomass quantification, the destructive method was used, where 15 individuals of each species were slaughtered and sectioned. The stem, branches and leaves components were individually quantified and weighed. Samples were collected to carry out chemical analyzes in the laboratory. The mean values of total biomass and carbon per individual tree were estimated at 26.6 and 13.3 (kg arv-1) in Mimosa tenuiflora; 22.4 and 11.2 (kg arv-1) in Cenostigma pyramidale and 25.8 and 12.9 (kg arv-1) in Cordia glazioviana. Biomass allocation followed the order stem > branches > leaves. Nutrient contents followed the sequence N>K>P for all classes, except C. pyramidale. Each hectare of the evaluated area fixed 7.42 Mg-1 of atmospheric carbon and 0.107; 0.011; 0.014 (Mg-1) of NPK, respectively. The area presented characteristic of a wooded Steppe Savannah.