Báo cáo lâm nghiệp: Hourly and daily variations of xylem sapflow in sweet chestnut coppices using a thermal measurement method

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Hourly and daily variations of xylem sapflow in sweet chestnut coppices using a thermal measurement method...
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Báo cáo lâm nghiệp: "Hourly and daily variations of xylem sapflow in sweet chestnut coppices using a thermal measurement method"Hourly and daily variations of xylem sapflowin sweet chestnut coppicesusing a thermal measurement methodV. B. Saugier BobayLaboratoire d’Ecologie v6g6tale, bit. 362, Universite Paris-XI, 91405 France Orsay,Introduction time scales (Bobay and Granier, 1987): F = 42.84 x SA x !231; where F sapflow = (cm3!h-!); SA = sapwood area at heated probe level (cm K flow index (without dimen- ); 2A new method for measuring xylem sap- == sions). K !7’M - !T’f’u!T’!: where dTM = =flow (Granier, 1985) has been tested to temperature difference without any sapflowcalculate forest transpiration. Two cop- (°C); dT(u) temperature difference with sap- =pices of sweet chestnut (Castanea sativa flow u (°C).Mill.) in the south of Ile-de-France were Psychrometer and net-radiometer were in-studied. One of them was thinned to a stalled on a tower in the thinned coppice. Potential evapotranspiration Ep was calculateddensity of 3500 stems/ha, the other (6000 with using Priestley-Taylor’s equation (1972), astems/ha) was used as a control. hourly time step: This paper presents preliminary results Cp=1.26x(zt/(zl+!)x(f?n/A)of hourly and daily variations of xylem where Rn net radiation (W-m- A change ); 2 = =sapflow in the thinned coppice. of saturation vapor pressure per °C (kPa- ); 1 C- O psychrometer constant (kPa- A ); 1 C- o y = = latent heat of vaporization of water (J ). 1 g- ’ Use of this equation is not usually recom-Materials and Methods mended for forests but was found useful in chestnut coppices that have large leaves and a relatively large boundary layer resistance.A xylem sapflow measurement sensor com-prises two cylindrical probes inserted into theconducting ...