tailieunhanh - Báo cáo khoa học: "Temporal and spatial variation in transpiration of Norway spruce stands within a forested catchment of the Fichtelgebirge, Germany"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Temporal and spatial variation in transpiration of Norway spruce stands within a forested catchment of the Fichtelgebirge, Germany. | Ann. Sci. For. 1998 55 103-123 Inra Elsevier Paris 103 Original article Temporal and spatial variation in transpiration of Norway spruce stands within a forested catchment of the Fichtelgebirge Germany Martina Alsheimer Barbara Kostner Eva Falge John D. Tenhunen Department of Plant Ecology II Bayreuth Institute for Terrestrial Ecosystem Research University of Bayreuth 95440 Bayreuth Germany Received 15 January 1997 accepted 27 June 1997 Abstract - Tree transpiration was observed with sapflow methods in six Norway spruce Picea abies stands located in the Lehstenbach catchment Fichtelgebirge Germany differing in age 40 years up to 140 years structure exposition and soil characteristics. The seasonal pattern in tree canopy transpiration with the highest transpiration rates in July was very similar among the stands. However young dense stands had higher transpiration compared to older less dense stands. Because of forest management practices stand density decreases with increasing stand age and provides the best predictor of canopy water use. Measured xylem sapflux density did not differ significantly among stands . vary in correlation with stand density. Thus differences in canopy transpiration were related to differences in cumulative sapwood area which decreases with age and at lower tree density. While both total sapwood area and individual tree sapwood area decrease in older less dense stands leaf area index of the stands remains high. Thus transpiration or physiological activity of the average individual needle must decrease. Simulations with a three-dimensional stand model suggest that stand structural changes influence light climate and reduce the activity of the average needle in the stands. Nevertheless age and nutrition must be considered with respect to additional direct effects on canopy transpiration. Inra Elsevier Paris. transpiration canopy conductance sapwood area stand age stand density Picea abies Resume - Variations spatiotemporelles de la .