Transpiration of Pinus rotundata on a wooded peat bog in central Europe

Transpiration of a central European endemic tree species, Pinus rotundata Link, growing on a wooded peat bog in the Třeboň Basin, Czech Republic, was studied in 1999–2000. Transpiration was measured by sap flow techniques (heat field deformation method) on individual trees and scaled up to stand level. The radial patterns of sap flow density showed narrow peaks in the outer part of the xylem, sapwood accounted for 47–60% of the xylem radius and 72–84% of the xylem basal area. Adult trees tolerated well both short-term flooding during the growing season and drawdown of the water table to a depth of 60 cm below ground level. The maximum and mean daily transpiration rates were 3.0 and 1.8 mm per day, and were thus similar to published data for Scots pine. The seasonal total transpiration (25 April–20 October 2000, 180 days) amounted to 322 mm, or 62% of the potential evapotranspiration over this period. This canopy transpiration was compensated by 319 mm of precipitation. The difference between the accumulated precipitation and the accumulated transpiration (derived from seasonal sap flow measurements) closely mimicked the seasonal course of the water table.