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Research article2017Peer reviewedOpen access

Ecophysiological variation of transpiration of pine forests: synthesis of new and published results

Tor-Ngern, Pantana; Oren, Ram; Oishi, Andrew C.; Uebelherr, Joshua M.; Palmroth, Sari; Tarvainen, Lasse; Ottosson Löfvenius, Mikaell; Linder, Sune; Domec, Jean-Christophe; Näsholm, Torgny

Abstract

Canopy transpiration (E-C) is a large fraction of evapotranspiration, integrating physical and biological processes within the energy, water, and carbon cycles of forests. Quantifying E-C is of both scientific and practical importance, providing information relevant to questions ranging from energy partitioning to ecosystem services, such as primary productivity and water yield. We estimated E-C of four pine stands differing in age and growing on sandy soils. The stands consisted of two wide-ranging conifer species: Pinus taeda and Pinus sylvestris, in temperate and boreal zones, respectively. Combining results from these and published studies on all soil types, we derived an approach to estimate daily E-C of pine forests, representing a wide range of conditions from 35 degrees S to 64 degrees N latitude. During the growing season and under moist soils, maximum daily E-C (E-Cm) at day-length normalized vapor pressure deficit of 1 kPa (ECm-ref) increased by 0.55 +/- 0.02 (mean +/- SE) mm/d for each unit increase of leaf area index (L) up to L = similar to 5, showing no sign of saturation within this range of quickly rising mutual shading. The initial rise of E-Cm with atmospheric demand was linearly related to ECm-ref. Both relations were unaffected by soil type. Consistent with theoretical prediction, daily E-C was sensitive to decreasing soil moisture at an earlier point of relative extractable water in loamy than sandy soils. Our finding facilitates the estimation of daily E-C of wide-ranging pine forests using remotely sensed L and meteorological data. We advocate an assembly of worldwide sap flux database for further evaluation of this approach.

Keywords

canopy transpiration; leaf area index; Pinus sylvestris; Pinus taeda; relative extractable water; soil texture; vapor pressure deficit

Published in

Ecological Applications
2017, Volume: 27, number: 1, pages: 118-133 Publisher: WILEY-BLACKWELL