Turnover de raízes finas em uma floresta de terra firme na Amazônia Central

Abstract

The fine roots are considered the most dynamic part of the root system, as have a short lifespan and rapid mortality and decay, being responsible for most of the carbon and nutrient cycle of the soil below. Despite the importance of fine roots, few studies have been conducted in this plant compartment, mainly due to methodological difficulties. The main objective of this study was to evaluate the turnover of fine roots in terra firme forest in central Amazonia and the specific objectives were to verify the Turnover, Surface Area (ASR) and growth rate (TCR) and Disappearance (TDR) of fine roots in different topographic classes and correlate these data with the Volumetric Water Content (CVA) in soil and precipitation. The study was conducted at the Experimental Station of Tropical Forestry of the National Institute of Amazonian Research - INPA, in a permanent plot belonging to the Laboratory of Forest Management - LMF the same institute. To meet the research objectives acrylic boxes were installed at the study site and scanned with a flatbed scanner, from September 2011 to April 2013. ASR of fine roots was evaluated different (p = 0.014) according topographic classes, the plants from valley showed invest much more in surface area. The ASR of fine roots had a greater correlation with CVA in the soil than with precipitation. The TCR and TDR also show different behavior in relation to topography and different responses to the variables, where the TDR from valley be presented more strongly influenced by rainfall (r = 0.74, p = 0.001) and soil moisture (r = 0.69 ; p ˂ 0,001). The turnover of fine roots to terra firme forests in central Amazonia is 1.65 yr-1, based on this value, 305.5 g C m-2 years-1 of root biomass was available to soil via turnover. Considering the two topographies, the results indicate considering one year of observation, the root system of the plateau is renewed more often than valley, turnover was 1.81 yr-1 and 1.60 yr-1 for the plateau and lowlands, respectively.