Temporal variation of nutrients in stemflow in exploited primary forest in northeastern Pará State, Brazil

The study focused in the nutrient contribution from the stemflow (CE) to the hydrochemical cycling in an exploited primary forest in Benevides, Pará State, Brazil. The nutrient concentration in the stemflow contribution was assessed from December 1993 to April 1995, by using collar type collectors, built of silicon foam, connected to plastic recipients by plastic tubes. The stemflow contribution was monitored in twelve trees, where monthly samples were collected and analyzed for K⁺, Na⁺, Ca²⁺ and Mg²⁺ by atomic absorption spectrophotometry, N-NH₄ ⁺, N-NO₃ ^- and P-PO₄ ^3- by colorimetry, in continuous flow spectophotometer, total-N by micro Kjeldahl, and pH by potentiometry. The quantity of nutrients brought by stemflow was greater at the beginning of the rainy season, exhibiting strong seasonal variation for K⁺, Na⁺, Ca²⁺, Mg²⁺, N-total, and SO₄ ^2-. The behavior of PO₄ ^3- was the opposite. The amount of nutrients in stemflow decreased in the following order: K⁺ > Na⁺ > Ca²⁺ > t-N > SO₄ ^2- > Mg²⁺ > PO₄ ^3-. The distribution and intensity of rainfall did not very influence pH in stemflow.

Amazonian; Primary Forest; Stemflow; Nutrients