Poster: Ecophysiology

Abs # 9: Estimating water uptake in a red pine stand

Presenter:	Firooznia, Fardad , firooznia@denison.edu
Authors	Firooznia, Fardad  (A)
Affiliations:	(A): Denison University

The objective of this research is to measure water uptake in red pine (Pinus resinosa Ait.) at the stand level. Sap flow in tree trunks can be estimated using temperature dissipation probes (TDP). Thirty-mm-long probes were inserted at the four cardinal azimuths (N, S, E, and W) in each tree. Temperature differentials were measured every 10 seconds and means were recorded every 30 minutes using a Campbell 10X datalogger. Sapwood width was measured using 4 stem cores per tree. During the summers of 2002 and 2003, Sap flux density was measured in three trees for the whole study period, while several other sets of probes were moved among different trees every few days (24 trees in 2002, 12 trees in 2003). We used the sap flux density averaged among the four azimuth locations as an estimate of the actual sap flux density of each tree, and used these averages to calculate daily sap flow. Each summer there was good correlation between daily sap flow of the three constant trees and those of the others: R2 values range from 80-99.4%. Therefore, we scaled the daily sap flow to the level of the stand given knowledge of tree diameter distribution within the stand. Based on sap flow scaled to stand level, we estimate average daily water uptake during the study period for 2002 to be 4.2 mm/day and that for 2003 to be 2.2 mm/day. These estimates are compared with daily changes in soil water content measured during the same time period.