Application of the deuterium tracing method for the estimation of tree sap flow and stand transpiration of a beech forest (Fagus silvatica L.) in a mountainous Mediterranean region

摘要

The deuterium tracing method for sap flow measurement has been applied to beech trees growing on the southern slope of the Mont Lozere (Southern France). The beech stand is part of a 54 ha watershed. The mean age of the trees is 38 (standard error: 12 years). Up to 70 years ago, the forest was regularly coppiced and as a consequence, most of the present trees have multiple stems. Owing to the harsh of climate, the mean values of height and breast height diameter are only 8 m and 10 cm, respectively. The injection of tracer was carried out in July 1996 on three stems whose range of breast height diameters is representative of much of the stand. The sapflow was correlated to the stem diameter and ranged between 2.7 and 15.6 l/d. By using the stem diameter as scaling parameter, the stand transpiration over the measurement period was estimated to be 5.45 mm/d. This high value is explained by the wet antecedent conditions due to the intensive rains in the previous month. It is consistent with the field measurements of soil moisture variations and with independent evaporation estimations obtained from empirical and physical formulations. The Penman-Monteith evaporation model was used to back-calculate the canopy resistance given the measured flow rate and meteorological data. A complete analysis of uncertainty showed that the total relative error of the stand transpiration estimated from deuterium tracing does not exceed 15%. (C) 2003 Elsevier B.V. All rights reserved. [References: 40]