Estoque de necromassa em floresta não manejada e manejada no estado do Amazonas

Abstract

Necromass is the dead organic matter in forest ecosystems. Failure to quantify this component of the vegetation may lead to an underestimate of available carbon in tropical forests. Therefore the objective of this research was to evaluate the necromass stock in an undisturbed and a logged forest in the state of Amazonas, Brazil. The field work was conducted in Rio Preto da Eva (undisturbed forest) and Itacoatiara (logged forest). It was made the measurement of fallen trees volume, diameter and residual height of standing dead trees and classification in decomposition classes of logs with a minimum diameter of 10 cm. The volume, weight and carbon of the necromass were estimated and a comparison was made between the undisturbed and the logged forests, besides influence of the intensity forest exploration on the stock. Continuous forest inventory data were used to compare the carbon estimates from the mortality rate with those verified in the field work. Four volumetric models were adjusted with the volume datas from fallen trees. At undisturbed forest there was 67,0 ± 29,7 dead trees per hectare; the average volume was 44,41 ± 16,19 m3 ha-1, weight equal to 40,80 ± 11,17 Mg3 ha-1 and 20,67 ± 8,20 m3 ha-1 of carbon. At logged forest there was an average of 102,2 ± 8,2 trees per hectare, 72,46 ± 10,93 m3 ha-1, 66,19 ± 9,56 Mg3 ha-1 and 32,09 ± 4,64 Mg3 ha-1 from total volume, weight and carbon, respectively. There was a significant difference for all variables averages in the comparison between two forests, and the logged forest presented a stock up to 63.2% higher than the undisturbed forest. Concerning the influence of intensity forest exploration, was observed difference just for the number of dead trees between the greater intensity and the undisturbed forest. There was no difference between the carbon estimates from the mortality in continuous inventories and those obtained with the field work collected. The adjust of volumetric models obtained only one model with average accuracy for the undisturbed forest, the others models presented high error rates. The results show that the forest management activities provided a higher stock of necromass, but the intensity of exploitation did not have a great influence. The estimates generated by continuous forest inventory were sufficients to know the available carbon in the forest. The Schumacher–Hall was the better volumetric model for total necromass in both areas.