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Forest modelling: the gamma shape mixture model and simulation of tree diameter distributions / Rafał Podlaski in Annals of Forest Science, vol 74 n° 2 (June 2017)  

Public [article]  inAnnals of Forest Science > vol 74 n° 2 (June 2017) Titre : Forest modelling: the gamma shape mixture model and simulation of tree diameter distributions Type de document : Article/Communication Auteurs : Rafał Podlaski, Auteur Année de publication : 2017 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Végétation [Termes IGN] arbre (flore) [Termes IGN] densité de la végétation [Termes IGN] diamètre à hauteur de poitrine [Termes IGN] diamètre des arbres [Termes IGN] dynamique de la végétation [Termes IGN] estimation par noyau [Termes IGN] modèle de simulation [Termes IGN] modélisation de la forêt [Termes IGN] surveillance de la végétation Résumé : (auteur) Key message: New types of distribution functions are needed to model the dynamics of stands where important age classes are represented by few trees. In this study, the gamma shape mixture model and two simulation methods were used for generating tree diameter data. • Context: To analyse forest dynamics, it is necessary to know distribution of the characteristics (mainly tree diameters) of trees forming particular developmental phases. In many forest inventories, the measurement of large diameter at breast height (DBH) samples is practically impossible. In this case, DBH distributions can be generated using theoretical models. • Aims: The aim of this study was to assess the precision of the approximation of empirical DBH data using the gamma shape mixture (GSM) model and kernel density estimation. The strengths and weaknesses of the two simulation methods were presented and discussed. • Methods: The GSM model was adopted to approximate empirical DBH data collected in 20 near-natural stands. Two simulation methods were used: (a) the procedure based on a multimodal distribution and gamma random numbers (MDGR procedure) and (b) MCMC techniques with Metropolis–Hastings sampling (MH method). • Results: The GSM model precisely fitted the investigated DBH distributions. The MDGR procedure was slightly more precise than the MH method, especially in the case of the samples of 250 DBHs. The level of homogeneity within the drawn DBH sets was similar for all samples. • Conclusion: The GSM model is very flexible. The DBH random variates, generated with the use of analysed procedures, represented all tree generations being significant from a biological point of view. Numéro de notice : A2017-109 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1007/s13595-017-0629-y Date de publication en ligne : 03/04/2017 En ligne : https://doi.org/10.1007/s13595-017-0629-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84500 [article]

A critical analysis of methods for rapid and nondestructive determination of wood density in standing trees / Shan Gao in Annals of Forest Science, vol 74 n° 2 (June 2017)  

Public [article]  inAnnals of Forest Science > vol 74 n° 2 (June 2017) Titre : A critical analysis of methods for rapid and nondestructive determination of wood density in standing trees Type de document : Article/Communication Auteurs : Shan Gao, Auteur ; Xiping Wang, Auteur ; Michael C. Wiemann, Auteur ; et al., Auteur Année de publication : 2017 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Végétation [Termes IGN] analyse de sensibilité [Termes IGN] densité du bois [Termes IGN] forage [Termes IGN] instrument de mesure [Termes IGN] résistance des matériaux Résumé : (auteur) Key message: Field methods for rapid determination of wood density in trees have evolved from increment borer, torsiometer, Pilodyn, and nail withdrawal into sophisticated electronic tools of resistance drilling measurement. A partial resistance drilling approach coupled with knowledge of internal tree density distribution may offer an alternative solution for wood density surveys in the future. Context: Finding ways to nondestructively assess wood density in trees has been a quest by foresters and wood scientists around the world. In the past several decades, traditional increment borer methods have gradually evolved into sophisticated electronic tools of resistance drilling measurements. Aims: We provide a comprehensive review of research development in the use of several field nondestructive methods for rapid determination of wood density in trees and discuss pros and cons of each method for field applications. Results: The use of the increment borer has been a standard method for assessing wood density in trees, and it has been further developed into a system approach allowing the use of outer wood cores and knowledge of internal density distribution for predicting wood density of major tree components. Studies on the use of torsiometer, Pilodyn, and nail withdrawal tools have had very limited success and do not warrant replacement of the increment borer. Resistance drilling, on the other hand, has emerged as a potential tool for more efficient and economical collection of wood density information in trees. Conclusion: The resistance drilling method has considerable advantages over other methods in terms of less damage to trees, faster operation, and higher measurement sensitivity. Internal friction is a key factor that currently hinders further application. Numéro de notice : A2017-110 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1007/s13595-017-0623-4 Date de publication en ligne : 22/03/2017 En ligne : https://doi.org/10.1007/s13595-017-0623-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84501 [article]

Recent growth changes in Western European forests are driven by climate warming and structured across tree species climatic habitats / Marie Charru in Annals of Forest Science, vol 74 n° 2 (June 2017)  

Public [article]  inAnnals of Forest Science > vol 74 n° 2 (June 2017) Titre : Recent growth changes in Western European forests are driven by climate warming and structured across tree species climatic habitats Type de document : Article/Communication Auteurs : Marie Charru, Auteur ; Ingrid Seynave, Auteur ; Jean-Christophe Hervé (1961-2017) , Auteur ; Romain Bertrand, Auteur ; Jean-Daniel Bontemps , Auteur Année de publication : 2017 Projets : 1-Pas de projet / Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] arbre (flore) [Termes IGN] changement climatique [Termes IGN] croissance des arbres [Termes IGN] Europe (géographie politique) [Termes IGN] forêt [Termes IGN] habitat forestier [Termes IGN] inventaire forestier national (données France) [Termes IGN] précipitation [Termes IGN] température au sol [Vedettes matières IGN] Végétation et changement climatique Résumé : (auteur) Key message : Recent growth changes (1980–2007) in Western European forests strongly vary across tree species, and range from +42% in mountain contexts to −17% in Mediterranean contexts. These changes reveal recent climate warming footprint and are structured by species' temperature (−) and precipitation (+) growing conditions. Context : Unprecedented climate warming impacts forests extensively, questioning the respective roles of climatic habitats and tree species in forest growth responses. National forest inventories ensure a repeated and spatially systematic monitoring of forests and form a unique contributing data source. Aims : A primary aim of this paper was to estimate recent growth changes in eight major European tree species, in natural contexts ranging from mountain to Mediterranean. A second aim was to explore their association with species’ climatic habitat and contemporary climate change. Methods : Using >315,000 tree increments measured in >25,000 NFI plots, temporal changes in stand basal area increment (BAI) were modelled. Indicators of climate normals and of recent climatic change were correlated to species BAI changes. Results : BAI changes spanned from −17 to +42% over 1980–2007 across species. BAI strongly increased for mountain species, showed moderate/no increase for generalist and temperate lowland species and declined for Mediterranean species. BAI changes were greater in colder/wetter contexts than in warmer/drier ones where declines were observed. This suggested a role for climate warming, further found more intense in colder contexts and strongly correlated with species BAI changes. Conclusion : The predominant role of climate warming and species climatic habitat in recent growth changes is highlighted in Western Europe. Concern is raised for Mediterranean species, showing growth decreases in a warmer climate with stable precipitation. Numéro de notice : A2017-279 Affiliation des auteurs : LIF+Ext (2012-2019) Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s13595-017-0626-1 Date de publication en ligne : 14/04/2017 En ligne : https://doi.org/10.1007/s13595-017-0626-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85312 [article]