tailieunhanh - Báo cáo lâm nghiệp: "Variation of hydraulic conductance of under natural conditions some adult conifers"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Variation of hydraulic conductance of under natural conditions some adult conifers. | 357s Ann. Sci. For. 1989 46 suppl. 357S-360S Forest Tree Physiology E. Dreyer etal. eds. Elsevier INRA Variation of hydraulic conductance of some adult conifers under natural conditions A. Granier N. Breda . Claustres and F. Colin INRA Laboratoire de Bioclimatologie et Ecophysiologie Forestieres Centre de Nancy Champe-noux BP 35 54280 Seichamps France Introduction Along the soil-tree-atmosphere system liquid flow of water can be modelled satisfactorily under many conditions by the Ohm s analog in the liquid phase the flow depends upon water potential gradients and hydraulic conductance from the soil to the mesophyll which thus has an important significance for the description of water relations in trees. We present here some evaluations of hydraulic conductance of trees growing under natural conditions. Data were collected from different experiments involving xylem water potential and sap flow measurements and we will analyze 1 be-tween-tree variability of liquid path conductance and 2 the influence of soil drying on this parameter. Materials and Methods Study sites The experiments were carried out in the stands described in Table I. In the A. bornmulleriana stand 4 trees were subjected to an imposed drought by withholding incident rainfall with a plastic roof covering the soil. Sap flow measurements A thermal device Granier 1985 1987 allowed continuous measurement of sap flux density which was Integrated along a radial axis into the sapwood of the trunk. Total sap flow was evalu- Table I. Description of the stands used in this study Species Localization Age yr Density stems ha Mean ht m Sapwood area m2 ha Picea abies Nancy 21 4500 Pinus pinaster Landes-de-Gascogne 37 385 Abies bornmulleriana Nancy 23 2500 358s ated through estimation of the sapwood area of the tree at flowmeter level. Measurements were made at 10 s intervals and data presented here are hourly averages. Xylem water potential This parameter was measured with a .