Abstract. This paper aims at proposing efficient vegetation sampling strategies. It describes how the estimation of species richness and diversity of moist evergreen forest is affected by (1) sampling design (simple random sampling, random cluster sampling, systematic cluster sampling, stratified cluster sampling); (2) choice of species richness estimators (number of observed species vs. non‐parametric estimators) and (3) choice of diversity index (Simpson vs. Shannon). Two sites are studied: a 28‐ha area situated in the Western Ghats of India and a 25‐ha area located at Pasoh in Peninsular Malaysia. The results show that: (1) whatever the sampling strategy, estimates of species richness depend on sample size in these very diverse forest ecosystems which contain many rare species; (2) Simpson's diversity index reaches a stable value at low sample sizes while Shannon's index is affected more by the addition of rare species with increasing sample size; (3) cluster sampling strategies provide a good compromise between cost and statistical efficiency; (4) 300 ‐ 400 sample trees grouped in small clusters (10–50 individuals) are enough to obtain unbiased and precise estimates of Simpson's index; (5) the local topography of the Western Ghats has a major influence on forest composition, the steep slopes being richer and more diverse than the ridges and gentle slopes; (6) stratified cluster sampling is thus an interesting alternative to systematic cluster sampling.
— This paper is part of a study proposing a new method for assessing the quality of wood resources from regional inventory data. One component of this method is a wood quality simulation solfware that requires detailed input describing tree branchiness and morphology. The specific purpose of this paper is to construct models that predict the main characteristics of the crown for Norway spruce. One hundred and seventeen spruce trees sampled in northeastern France have been described in detail. The position of the different parts of the crown, the size, the insertion angle, the number and the position of the whorl branches have been predicted as functions of usual whole-tree measurements (ie diameter at breast height, total height, total age) and of the position of the growth unit along the stem (ie distance to the top, and number of growth units counted downward or upward) for branchiness prediction. The most efficient predictors of crown descriptors have been established and preliminary models are proposed. branchiness / Picea abies Karst / modelling / wood quality / crown ratio / wood resources Résumé— Branchaison de l'épicéa commun dans le Nord-Est de la France : prédiction des principales caractéristiques du houppier à partir des mesures dendrométriques usuelles. Cette étude s'insère dans le cadre d'un projet qui vise à proposer une nouvelle méthode d'évaluation de la qualité de la ressource à partir des données issues d'un inventaire forestier régional. Ce projet s'appuie notamment sur un logiciel de simulation de la qualité des sciages qui nécessite une description détaillée de la morphologie et de la branchaison de chaque arbre. Cet article concerne spécifiquement l'épicéa commun et vise à proposer des modèles de prédiction des principales caractéristiques du houppier à partir des données dendrométriques usuelles. Cent dix sept épicéas échantillonnés dans le Nord-Est de la France sont décrits en détail. La position des différentes zones du houppier, le diamètre, l'angle d'insertion, le nombre et la position des branches verticillaires sont prédits à partir des variables dendrométriques usuelles (diamètre à 1,30 m, âge et hauteur totale) et de la position de l'unité de croissance considérée le long de la tige (distance à l'apex, âge ou numéro de l'unité de croissance) pour la prédiction de la branchaison. Les variables dendrométriques les plus efficaces (pour la prédiction) sont mises en évidence et des modèles préliminaires sont proposés.
A new approach for modelling plant growth using the software AMAPpara is presented. This software takes into consideration knowledge about plant architecture which has been accumulated at the Plant Modelling Unit of CIRAD for several years, and introduces physiological concepts in order to simulate the dynamic functioning of trees. The plant is considered as a serial connection of vegetative organs which conduct water from the roots to the leaves. Another simple description of the plant as a network of parallel pipes is also presented which allows an analytical formulation of growth to be written. This recurring formula is used for very simple architectures and is useful to understand the role of each organ in water transport and assimilate production. Growth simulations are presented which show the influence of modifications in architecture on plant development.
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