Dinâmica temporal do efluxo de CO2 e produção de glomalina em área de caatinga sob neossolo litólico

Abstract

The study of the Caatinga ecosystem dynamics, which includes the nutrient cycling process, through litter input and decomposition, the microbial activity measured through CO2 efflux, and the production of glomalin, an indicator of soil physical quality, makes It is necessary to know the specificities of this biome and thus propose conservation measures and appropriate management of the soils of these areas. This work aimed to determine in-situ CO2 efflux and easily extractable glomalin production in soil and its relationship with aggregation, to evaluate litter production and decomposition and nutrient cycling under tree and shrub vegetation in an area. of caatinga preserved in the dry and rainy periods. The work was developed at Professor Ignácio Salcedo Experimental Station, of the National Institute of Semiarid (INSA), located in Campina Grande - PB. A transect inserted in both environments was demarcated, the samples were taken in the tree and shrub environments and compared later, observing the interference of environmental factors such as precipitation, humidity and soil temperature under the studied variables. Collectors were installed to accompany the monthly contribution of litter. To evaluate the decomposition rate and nutrient cycling, litter bags were used, where the remaining mass was determined, and the N, P, K and C contents of litter released over 1 year were quantified. Monthly CO2 emission was evaluated by the closed-chamber static method and glomalin was determined by the Bradford assay and correlated with aggregate stability. The litter input was higher in the shrub area, and also the decomposition rate of the plant material was faster for shrub species compared to the tree species. The annual nutrient intake followed the sequence of N> K> P, and the highest nutrient inputs were in the dry season for both environments. The highest CO2 emissions were found in the shrubby environment. The easily extractable glomalin presented a seasonal pattern, where its highest values were obtained in the dry season, regardless of the vegetation type of the area. The highest content of Total Organic Carbon was found in the tree vegetation environment and the aggregate stability index was higher in the shrub environment. The highest correlation values were between IEA and COT. It was observed the strong influence of climatic factors such as precipitation, humidity and soil temperature under the analyzed variables.