tailieunhanh - Báo cáo khoa học: "Evapotranspiration measurements in a Mediterranean forest stand by means of ecophysiological and microclimatic techniques"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Evapotranspiration measurements in a Mediterranean forest stand by means of ecophysiological and microclimatic techniques. | 325s Ann. Sci. For. 1989 46 suppL 325s-329s Forest Tree Physiology E. Dreyer etal. eds. Elsevier INRA Evapotranspiration measurements in a Mediterranean forest stand by means of ecophysiological and microclimatic techniques R. Valentini . Scarascia-Mugnozza and M. Sabatti Istituto Biologico Selvicolturale Università della Tuscia Via De Lellis 4 01100 Viterbo Italy Introduction Materials and Methods In the Mediterranean region dry summers are quite common and water availability is one of the most important factors determining forest growth and development. Furthermore the lack of water for public use experienced in central and southern Italy during the summer period makes the analysis of the water cycle in forest and its impact on watershed management important. The techniques available today for determining water consumption by forest stands range from large scale hydrological balances to transpiration measurements of an individual leaf. Among these the heat pulse velocity technique hpv for measuring sap fluxes seems to be simple and reliable Marshall 1958 Swanson 1962 Granier 1985 but different approaches have to be compared in order to determine its degree of accuracy. In this paper we compare the energy balance Bowen ratio and the hpv technique for determining water consumption of an oak stand. The forest stand is located in central Italy consists mainly of oaks Quercus cerris L. and is managed as coppice with standard trees originated by gamic reproduction. The stand averages 2400 sprouts and 97 standards of 2 age classes per ha corresponding to the double and single harvesting cycle respectively The leaf area index LAI of the whole stand is Scarascia-Mugnozza etal. 1989 . Energy balance measurements were carried out by means of an exchange mechanism carrying 2 ventilated ceramic wick psychrometers Gay 1971 . Net radiation was measured with a net radiometer Middleton Inc. . All the micro-meteorological data were collected every 10 min by a data logger .