TAILIEUCHUNG - Báo cáo khoa học: " Water flux in boreal forest during two hydrologically contrasting years; species specific regulation of canopy conductance and transpiration"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: " Water flux in boreal forest during two hydrologically contrasting years; species specific regulation of canopy conductance and transpiration. | Ann. Sci. For. 1998 55 47-61 Inra El Sevier Paris 47 Original article Water flux in boreal forest during two hydrologically contrasting years species specific regulation of canopy conductance and transpiration Emil Ciencialaa Jiri Kucerab Michael G. Ryanc Anders Lindrothd a Department of Soil Sciences Swedish University of Agricultural Sciences Box 7014 750 07 Uppsala Sweden b Laboratory of Environmental Measuring Systems Turisticka 5 621 00 Brno Czech Republic c Rocky Mountain Experiment Station USDA Forest Service Fort Collins co USA d Department for Production Ecology Swedish University of Agricultural Sciences Box 7042 750 07 Uppsala Sweden Received 15 January 1997 accepted 21 October 1997 Abstract - We estimated the reduction of transpiration from drought for tree species in a mixed boreal 60-year-old stand in central Sweden. Actual transpiration was estimated from direct measurements of sap flow rate in Pinus sylvestris and Picea abies trees during two consecutive years with contrasting precipitation. Drought-induced reduction of transpiration transpiration deficit was quantified as the difference between the measured sap flow and the transpiration calculated for non-limiting soil water conditions. The drought-free transpiration was estimated on an hourly basis from Penman-Monteith equation with the parameterized canopy conductance gc functions for individual species. The values of gc for fitting a two-parameter function of radiation and vapour pressure deficit were obtained for a 3-d period by inverting the Penman-Monteith equation. Canopy conductance of pine was similar relative to spruce on ground area basis. This made gc of pine larger relative to spruce per leaf area unit since pine tree foliage mass was about one third that of spruce. Transpiration deficit was small in the growth season of 1995. It reached about 10 for spruce during the summer months. In 1994 however the transpiration deficit was large for both species and extended throughout most of .

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