Balanço e espiral de carbono sob a perspectiva teórica de ecossistemas para ecologia de riachos

Abstract

Studying the flux of energy and matter using the ecosystem paradigm is one of the main subjects in stream ecology. A variety of concepts and approaches were developed with this perspective, with considerable improvements for ecological theory. The carbon budget (C budget) is one of the main approaches used. The Spiraling concept, in turn, gives essential ideas of longitudinal connectivity of elements in transformation through the system. Despite being forged long time ago and look promising still these days, the organic carbon spiraling (SOC) approach is barely used by stream ecologists. Beyond the essential conceptualization for the understanding of ecosystem structure and function, SOC uses some of the operational variables used in C budget. Yet, studies using both approaches at the same time are rare. The present thesis had as tis objective to elucidate the processes of ecosystem carbon fluxes through the river continuum using both approaches, analyze its connection in terms of metrics, and describe the main predictors of generated results. Therefore, campaigns were performed between Jun/13 and Apr/16 in five points of Córrego da Andorinha stream, Ilha Grande, RJ, a short tropical stream of the Atlantic coast with high longitudinal connectivity. Temporal variation in the allochthonous input was observed, with higher input rates in the "rainy season", related to extreme events. Input rates through the continuum varied according to riparian zone structure of the stretch. Total organic carbon (OC) export was higher in higher discharge (Q) stretches, and higher discharge months, but not in "rainy season" months. The relation between input and export (I/O) of coarse OC regulates processes of accumulation or subtraction, which seem to change prevalence according hydrological factors ruled in large space-time scale. SOC calculations returned a Gaussian mode curve for the headwater-mouth gradient, with higher spiraling length in the middle-course, and lower in the headwaters and stream mouth. Hydrological factors regulated OC transported (TOC) concentrations of dissolved and fine carbon, which were the main loads of C in SOC calculation. TOC concentration through the continuum reversed during a flood, which exported in 8h the expected amount for a month in basal conditions. In the perspective of climate change impact on ecosystem function, C flux processes seems to be altered mainly in function of changes in "rain" and "dry" patterns. Perspectives of integration and improvement were discussed relating the operational variables in terms of ecosystem thinking