Dinâmica de raízes finas em florestas de terra firme na Amazônia Central

Abstract

This study evaluates fine root dynamics (stock, productivity and turnover) along the soil profile and in different diameter classes over the year, across seasons and in response to P addition in two sites in central Amazon rainforest. Roots <2mm were analyzed with minirhizotrons until 90 cm of depth. Minirhizotrons were calibrated with soil cores and compared with ingrowth cores. Linear mixed models were used to control for the hierarchical experimental design and Kruskal– Wallis tests were performed when the data did not fit the assumptions of linear mixed models. To compare methods, t tests were used. Fine root dynamics varied significantly between diameter classes and depth intervals. Most of the entire stock (76.13%) and productivity (82.25%) was observed in thinner roots (0 to 0.5mm). In addition, approximately half of fine root stock (46.12%) and productivity (40.61%) were concentrated in layers below 30cm. However, fine root turnover did not vary between diameter classes and depth intervals. Considering seasons, fine root productivity was higher in the wet season in the most superficial layer and root stock was higher in the dry season at the deepest layer. There was no significant divergence in stock estimates when minirhizotron was compared with soil core, nor was there any difference in root productivity when comparing ingrowth core and minirhizotron. Regarding the fertilization experiment, fine root dynamics did not respond to P addition. In summary, the presence of a high proportion of root dynamics below 30 cm presents that deep roots cannot be forgotten to measure. Phosphorus may not be a limiting nutrient to roots in Central Amazonia