SAP FLOW AND VESSEL PARAMETERS OF MOROTOTO ( SCHEFFLERA MOROTOTONI ) IN CENTRAL AMAZONIA

Abstract

Heat balance components were measured at a bare land, and the xylem sap flow of a pioneer species (Schefflera morototoni) and the vessel parameters were measured at a neighboring secondary forest in a forest reserve near Manaus, AM from August to September, 2012. The downward shortwave radiation (SWd) reached 1,000 W·m^-2 in the daytime on sunny days, which increased temperatures above 40℃ , and decreased relative humidity below 30%. As a result, the saturation deficit exceeded 60 hPa. The SWd on rainy days, on the other hand, was about 200 W·m^-2, and the maximum temperature did not reach 30 ℃ , which made the saturation deficit remain close to zero. The sap flow of a tree with a height of 19 m reached 17 l·h^-1 before noon on sunny days, but it was up to 3 l·h^-1 on rainy days. While a 12 m tree had a sap flow of 24.3 l·day^-1, that of a 19 m tree was 94.7 l·day^-1, showing that the sap flow was dependent on tree size. Vessel diameter (d) in the stem cross-section increased with tree growth, such as from 75 μm at the pith to 125 μm near the cambium. The Σd⁴ , a part of hydraulic conductivity, had the same phase as the sap flow and tree height, which suggested that an individual tree copes with efficiently absorbing a large amount of water to the canopy layer by increasing the vessel diameter.