tailieunhanh - Báo cáo lâm nghiệp: " Sampling strategies in forest soils"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế, đề tài: Sampling strategies in forest soils. | 493 Ann Sci For 1997 54 493-499 Elsevier Inra Note Sampling strategies in forest soils J Fons1 T Sauras2 J Romanyà2 VR Vallejo2 1 Forest Sciences Deportment University of British Columbia 270-2357 Main Mall Vancouver BC Canada V6T IZ4 2 Departament de Biologia Vegetal Facultat de Biologia Universitat de Barcelona Avda Diagonal 645 08028 Barcelona Spain Received 31 August 1995 accepted 2 September 1996 Summary - Many studies have revealed the high variability of soil properties especially on the forest floor. Sampling techniques have been developed to reduce this variability so as to obtain more precise mean values. Little attention has been paid to the frequency distributions of variables even though they could provide information on factors that control variability. This paper addresses the selection of the sampling strategy considering the type of study. For the characterization of ecosystems stratified sampling or systematic sampling is proposed depending on previous knowledge of the study area. To study processes two cases were considered processes that occur within the ecosystem such as organic matter decomposition and processes that concern the whole ecosystem such as fire. In the first case subjective sampling was useful since it reduced the extrinsic variability of the processes. In the second case both stratified and systematic sampling were very effective. Frequency distribution analysis was proposed as a tool to detect some factors that control litter accumulation. forest floor frequency distribution subjective sampling stratified sampling systematic sampling variability Resume - Strategies d echantillonnage dans les sols forestiers. Beaucoup d etudes ont révélé la grande variabilité des propriétés du sol. cn particulier cellos relatives aux horizons organiques. Plu-sieurs techniques d echantillonnage ont etc dcveloppees pour rcduire la vaiiabilité et obtenir des valeurs moyennes avec precision. Bien que Tétude des distributions de frequences puisse .