Efeito da interação entre vegetação, hidrologia e solo no efluxo de CO2 no Pantanal Mato-grossense

Abstract

The increase in carbon dioxide (CO2) emission rates intensifies studies related to the importance of tropical forests in the carbon cycle. Flooded seasonal forests have peculiar characteristics for soil respiration and, consequently in the carbon cycle. The Pantanal, the largest floodplain in the world, there is great scientific interest in the accumulation of carbon, so that current research attempts to discover the true function (source or drainage) of this ecosystem. In this sense, the objective of the study is to understand the CO2 efflux in Pantanal Mato-grossense. The effects of the interaction between vegetation (Vochysia divergens Pohl - CAM, Ipomoea carnea spp. Fistulosa - ALG, Combretum lanceolatum Pohl - POM), hydrology (pre-flooding, post-flooding and drought) and soil (physical and chemical) on the CO2 efflux in the soil. The average annual value of CO2 efflux was 5.25 μmol m-2 s - in CAM, 4.28 μmol m-2 s - in

ALG and 5.0 μmol m-2 s - in POM, only the ALG vegetation differed statistically. The results found showed interaction of the variables clay, soil concentration, soil temperature, pH, nitrogen, phosphorus and total organic carbon (COT), in the CO2 efflux in the soil. There was an interaction in the selected values for CO2 efflux with vegetation and hydrological period. As the clay, pH, nitrogen and COT variables increased in the post-flooding, contributing to the increase in CO2 efflux in the soil. The lowest values reached in the drought occurred in three vegetations, due to low soil moisture and high soil temperature. The changes observed in the CO2 efflux values in the different hydrological periods were due to the partial filling of the pores with water, for biogeochemical processes, precipitation and temperature. The different responses of vegetation, in relation to hydrological periods, contributed to the interaction in the values found for efflux such as: difference in altitude (time of flooding), phenology, pH and differences in nutrients. Therefore, the biotic and abiotic factors contributed to alter the CO2 efflux in the soil, closely related to the deposited sediments and to the flood (anaerobic) and dry (aerobic) phases.