tailieunhanh - Báo cáo khoa học: "Estimating tree canopy water use via xylem sapflow in an old Norway spruce forest and a comparison with simulation-based canopy transpiration"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Estimating tree canopy water use via xylem sapflow in an old Norway spruce forest and a comparison with simulation-based canopy transpiration. | Ann. Sei. For. 1998 55 125-139 Inra Elsevier Paris 125 Original article Estimating tree canopy water use via xylem sapflow in an old Norway spruce forest and a comparison with simulation-based canopy transpiration estimates Barbara Kostner Eva M. Falge Martina Alsheimer Ralf Geyer John D. Tenhunen Bayreuth Institute for Terrestrial Ecosystem Research BITỒK Department of Plant Ecology II University of Bayreuth 95440 Bayreuth Germany Received 15 January 1997 accepted 20 October 1997 Abstract - Tree xylem sapflow rates of 140-year-old Norway spruce Picea abies were scaled to the stand level and compared to canopy transpiration predicted by the stand gas exchange model STANDFLUX. Variation in sapflux densities between individual sensors was high coefficient of variance and included both variation within and between trees but it was not different between two applied sapflow methodologies radial flowmeter according to Granier variable heating tissue heat balance method according to Cermák and Kucera . During the morning a time-lag of typically 2 h elapsed between sapflow f and predicted canopy transpiration rate p . During this time total water use was as high as mm which was less than the estimated capacity of easily available water in the tree canopy mm on average 14 L per tree . Canopy conductance derived from stand sapflow rates gf and from STANDFLUX gp was in the same range 0 mm s but a stronger decline with increasing vapor pressure deficit of the air Correspondence and reprints Abbreviations CBH tree circumference at breast height CV coefficient of variation DBH tree diameter at breast height D vapor pressure deficit of the air Dmax daily maximum half-hour average vapor pressure deficit of the air Ddark average vapor pressure deficit during night dw dry weight E forest canopy transpiration rate Ef. forest canopy transpiration rate derived with time shift in xylem sapflow Ep forest canopy transpiration rate predicted from STANDFLUX Model gc canopy .

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