Grelle, Achim
- Department of Ecology, Swedish University of Agricultural Sciences
Abstract
Estimation of areal evapotranspiration is crucial for the parameterization of the soil-vegetation-atmosphere interface in climate models and for the assessment of land-use changes on water resources. Present knowledge on how areal forest evapotranspiration depends on forest species composition and age is insufficient. In this study, transpiration of 50- and 100-year-old coniferous stands was estimated on the basis of sap-flow measurements on 24 trees, 12 in each stand. The measured samples represented the size distribution of Pinus sylvestris and Picea abies trees. Daily canopy transpiration (E-Q) was scaled from individual tree flow rates using the quotients of stem circumferences of the sample trees to those of the stands. E-Q was used in a rearranged Penman equation to deduce a potential canopy conductance, valid for non-limiting soil-water conditions, from a period when soil-water storage was not limiting transpiration. This enabled quantification of the seasonal transpiration deficit, which in both stands reached at least one fifth of the total potential transpiration over the growth season. The estimated fluxes of E-Q were low with a maximum daily value of about 2.8 mm in the 50-year-old stand. For dry-weather days, E-Q was well correlated to daily sums of stand evapotranspiration estimated from eddy-correlation measurements. Responses to drought were species specific. Transpiration in pines from the 50-year-old stand was less affected by drought relative to spruce or older pine trees, which was also reflected by stem increment during the season. (C) 1997 Elsevier Science B.V.
Keywords
transpiration deficit; drought; pine; spruce; Pinus sylvestris; Picea abies
Published in
Agricultural and Forest Meteorology
1997, volume: 86, number: 45720, pages: 157-167
SLU Authors
UKÄ Subject classification
Fish and Aquacultural Science
Environmental Sciences and Nature Conservation
Bioenergy
Publication identifier
- DOI: https://doi.org/10.1016/S0168-1923(97)00026-9
Permanent link to this page (URI)
https://res.slu.se/id/publ/23889