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Báo cáo khoa học: "Analyse de la variabilité spatio-temporelle et modélisation statistique des variations"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Analyse de la variabilité spatio-temporelle et modélisation statistique des variations. | Ann. Sci. For. 1988 45 4 323-340 Analyse de la variability spatio-temporelle et modélisation statistique des variations de stock d eau du sol en íorêt J. CHADOEUF G. AUSSENAC A. GRANIER INRA Station de Biométrie Centre de Recherches d Avignon Domaine Saint-Paul F 84140 Montfavet INRA Station de Sylviculture et de Production Centre de Recherches de Nancy Champenoux F 54280 Seichamps Summary Analysis of temporal and spatial variability and statistical modelling of soil water reserve in forest stands Soil water reserve distribution measured with a neutron moisture meter in forest stands presents a great variability both in space and in time. An important problem in forest stand water consumption studies at present based upon water balance methods is the sampling for soil water content measurement. An answer to this question is to study the variability of soil water reserve. The authors propose a statistical analysis model allowing the separation of total variation into a time variation and a space variation. The model for interaction separation is based on Principal Component Analysis. Water stock measured at a point X at a time t is decomposed in a general mean to which is added the product of a term linked to time with a term linked to space and a random term. This expresses the fact that once the variables are centred measurements taken at each point of the stand fluctuate proportionally to one another. Random errors are assumed to be independant and to follow a single model. The model paramaters and their variance-covariances are estimated assuming that the random contribution to variance is small compared to global variance which has actually proved to be right in the present study. In a first stage the model parameters are estimated with their statistical characteristics. A strong heterogeneity generally appears between mensurations points both for the average reserve at each point and for the multiplicative terme linked to space. In a second stage these .