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Article Dans Une Revue Annales de l'Ecole Nationale des Eaux et Forêts et de la Station de Recherches et Expériences Forestières Année : 1957

Recherches sur l'application aux taillis-sous-futaie des Méthodes Mathématiques-Statistiques d'Inventaire

Jean Pardé
  • Fonction : Auteur

Résumé

SUMMARY. After an analysis of foreign works on the application to forestmanagement of forest survey by statistical methods of sampling, theauthor describes the stands which he studied himself. The dcmanialforest of Izeure, a rich composite forest about to be converted, liesin the valley of the Saône, 25 km south-east of Dijon.The characteristic species of the reserve is oak (Quercus robar andQ. pedunculata) forming 77 % of the total volume together withsome beech (12 %) ans various species (II %).The average volume per hectare is 177 cubic meter (stem andbranch wood).The survey of 170,47 ha of the forest was done on the one handstem by stem, along traditional methods, ans compartment by compartment,on the other hand by mathematical-statistical methods ofsampling.Systematically laid circular plots of io ares in area were usedat the density of one every for 50 ares of forest.The main following results were obtained:I° Survey of forest stands by sampling and use of mathematical-statistical methods can be applied in France in the frameworkof managements, and in particular to the case of cannice with standardsforests such as are found in the plain of the Saône.2 ° Systematic samplings in forest surveys give results that are atleast as good as random probings and the computation of the standarderror of the mean usualy reserved to the latter type of surveyscan eotially be applied to them.3° Circular sampling plots are very convenient. In this study Toares nlnts revealed therselve dequate.4° The methods described can he readily i_iti'ized by the ordinarypersonnel of the Forest Service. The conduct of inventory operations— preparatory office work, actual field application, calculations.— has been established.5° For the management of a forest. it appears sufficient to obtain,at the 5 % level of siaoificance, an error on the mean smaller than± 10 % for total volumes.6° Sampling 1/10th of the area inventoried — on e 10 ares plotper hectare of stand — costs twice less than complete sat -online: inthe case studied here. It is adequate for area larger than 75 hectares. 7° Sampling I/zoth of the area inventoried — one Io ares plotper two hectares of stand — is at least one third cheaper than completesampling. It is applicable to areas larger than 170 hectares.8° This type of inventory also gives accurate enough results —standard error of the man of ± 15 % for exemple,— for secondarydata used un the estimation of the possibility (separation of stemsbetween mature and immature in particular).9° A méthode is shown for finding by a preliminary test surveythe number of sampling points to be laid over a given forest inorder to obtain a given level of precision.1° After a division of the forest into elementary units, the authorstudied the eventual use of variance analysis permitting a reductionof the true error on the survey. This method may certainly oe usefulin dealing with a heterogeneous forest; but in this particularcase, it appeared that the variations between stands, although noticeable,did not motivate an analysis of the variance.The . ubdivision of a forest into blocks, if it is to be justified,should essentially be based on the study of the ecological sites.(Traduction L. ROUSSEAU.)
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hal-03483750 , version 1 (16-12-2021)

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Jean Pardé. Recherches sur l'application aux taillis-sous-futaie des Méthodes Mathématiques-Statistiques d'Inventaire. Annales de l'Ecole Nationale des Eaux et Forêts et de la Station de Recherches et Expériences Forestières, 1957, 15 (2), pp.455-557. ⟨hal-03483750⟩
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