Preliminary results on dissolved organic carbon fluxes in a primary forest at the headwaters of the Xingu basin, Mato Grosso, Brazil
Neu, Centro de Energia Nuclear na Agricultura - CENA/USP, email@example.com
Krusche, Centro de Energia Nuclear na Agricultura - CENA/USP, firstname.lastname@example.org
Montebello, Centro de Energia Nuclear na Agricultura - CENA/USP, email@example.com
The main objective of this study is the assessment of dissolved organic carbon (DOC) fluxes within a tropical primary forest in the headwaters of the Xingu river basin, Mato Grosso, Brasil. The study site is located near the cities of Querencia and Canarana, in the Darro river basin. The vegetation of this transition zone between Cerrados and tropical moist forests shows lower species diversity and smaller trees than the latter. From February to April 2007 (rainy season) bi-weekly samples were taken from collectors of rain, throughfall, stemflow, overland flow, preserved in the field with HgCl2, and latter filtered in the laboratory and analyzed with a Shimadzu TOC-VCPH to determine the concentrations of DOC. Preliminary results show that inputs of DOC are positively correlated with rainfall and with great variation between rain events. Rain inputs vary from 0.06 kg/ha in low rainfall events (5 mm) to 3 kg/ha, which is 6 to 37% of the dissolved carbon that reaches the soils in this basin. After crossing the canopy, rain becomes significantly enriched in DOC, and throughfall inputs vary from 0.09 kg/ha to 43.28 kg/ha respectively, which is 23 to 88%, of the DOC that reaches the soils in this basin. Significantly lower fluxes are observed in stemflow, which contributes with a minimum of 0.005kg/ha and a maximum 0.09kg/ha respectively. A small fraction of these inputs from rain and throughfall is exported as overland flow, respectively, 0.02 kg/ha to 0.07 kg/ha (1 to 3% DOC). When the remaining data from soil and stream water becomes available, we will be able to tell if this basin is retaining these inputs or exporting them to ground or surface water.