1,721,118 research outputs found
Measurement and Modelling - Basis of Forest Design
No full textThis contribution to the meeting on 27.7.2012, in memory of the 10th anniversary of the passing away of Prof. Dr. Dr. hc Friedrich Franz describes the current theory of sustainable forest use and its scientific foundations. Forest Ecosystem Design (known in German as "Forsteinrichtung") has been designated using various labels, such as "Forest Planning" and "Instument of Strategic Management". "Forsteinrichtung" is one of the oldest disciplines of forest science. Its major research contribution during the past two centuries has been to develop methods for ensuring sustainable forest use. In a contemporary context, "Forsteinrichtung" may be appropriately designated as "Forest Ecosystem Design". This contribution presents a theory of Forest Ecosystem Design known as the Multiple Path Concept which is based on six principles of sustainable forest use. Forest Ecosystem Design requires models which describe different kinds of disturbances and incorporate the current knowledge about ecosystem response to human use. Growth models describe tree survival, tree growth and recruitment while harvest event models estimate the immediate effects of a harvest event in terms of the structural changes, based on silvicultural terminology. Observational studies provide the essential empirical basis for developing such models. Whereas forest resource information, gathered in Forest Inventory Systems at local, national and global levels, is required for planning and policy decisions, Forest Research Plot Networks provide essential data for studying ecosystem structure and dynamics. New permanent observational studies with mapped trees in uneven-aged multi-species forests offer new possibilities for analysis and modeling, due to their increased area. This contribution presents examples from Asia, Eastern Europe and North America
Evaluating risk in forest planning models
No full textThe purpose of forest scenario modelling is to evaluate multiple management options and to answer what if questions relating to a particular development path of a given forest. Forest scenario planning can reduce uncertainty in management outcomes by anticipating the future in a systematic way, thus reducing the likelihood of unexpected events. It can also improve the chance that future developments will agree with specified objectives. Numerous techniques have been proposed for generating and evaluating scenarios of forest development. Some of the techniques are limited to applications in simple forest production systems while others are suitable for any type of forest management, including individual tree selection systems. Risk is defined as the expected loss due to a particular hazard for a given area and reference period. An expected loss may be calculated as the product of the damage and its probability. Risk analysis, risk evaluation and risk management are formal procedures for quantifying evaluating and managing risk within a given hazard domain. Applications of risk analysis in forest scenario planning are rare and greater emphasis needs to be placed on hazard prediction. The aim of this contribution is to discuss some aspects of risk analysis, including examples of specific modelling tools. In a forest planning model risk can be considered in the form of specific constraints limiting the total risk in a given time period. Expected hazards can be used to exclude certain risky alternatives and finally, risk can be calculated and used to reduce the value of an objective function coefficient
Measurement and Modelling - Basis of Forest Design
No full textThis contribution to the meeting on 27.7.2012, in memory of the 10th anniversary of the passing away of Prof. Dr. Dr. hc Friedrich Franz describes the current theory of sustainable forest use and its scientific foundations. Forest Ecosystem Design (known in German as "Forsteinrichtung") has been designated using various labels, such as "Forest Planning" and "Instument of Strategic Management". "Forsteinrichtung" is one of the oldest disciplines of forest science. Its major research contribution during the past two centuries has been to develop methods for ensuring sustainable forest use. In a contemporary context, "Forsteinrichtung" may be appropriately designated as "Forest Ecosystem Design". This contribution presents a theory of Forest Ecosystem Design known as the Multiple Path Concept which is based on six principles of sustainable forest use. Forest Ecosystem Design requires models which describe different kinds of disturbances and incorporate the current knowledge about ecosystem response to human use. Growth models describe tree survival, tree growth and recruitment while harvest event models estimate the immediate effects of a harvest event in terms of the structural changes, based on silvicultural terminology. Observational studies provide the essential empirical basis for developing such models. Whereas forest resource information, gathered in Forest Inventory Systems at local, national and global levels, is required for planning and policy decisions, Forest Research Plot Networks provide essential data for studying ecosystem structure and dynamics. New permanent observational studies with mapped trees in uneven-aged multi-species forests offer new possibilities for analysis and modeling, due to their increased area. This contribution presents examples from Asia, Eastern Europe and North America
Applications of the bimodal Weibull function for describing diameter distributions in beech forests.
No full textEmpirical and theoretical diameter distributions are important for describing forests and providing starting conditions in growth simulations. Unimodal statistical distributions like the WEIBULL-function are often used in even aged conifer stands. In a managed beech forest, the vertical structure depends on the type of thinning that is applied. In a high thinning, which is generally practiced in Germany, only the bigger trees are removed while the smaller ones may survive for a long time, resulting in a typical structure with two subpopulations. This paper presents a method for describing bimodal diameter distributions in such beech stands using a mixed form of the WEIBULL function. The function parameters can be derived using estimates of the maximum and minimum stand diameters, the total stand height as well as the basal area for both layers. The join parameter g can be estimated using the relativ proportion of stems per hectare in the lower stand stratum, which depends on the thinning type
Applications of the bimodal Weibull function for describing diameter distributions in beech forests.
No full textEmpirical and theoretical diameter distributions are important for describing forests and providing starting conditions in growth simulations. Unimodal statistical distributions like the WEIBULL-function are often used in even aged conifer stands. In a managed beech forest, the vertical structure depends on the type of thinning that is applied. In a high thinning, which is generally practiced in Germany, only the bigger trees are removed while the smaller ones may survive for a long time, resulting in a typical structure with two subpopulations. This paper presents a method for describing bimodal diameter distributions in such beech stands using a mixed form of the WEIBULL function. The function parameters can be derived using estimates of the maximum and minimum stand diameters, the total stand height as well as the basal area for both layers. The join parameter g can be estimated using the relativ proportion of stems per hectare in the lower stand stratum, which depends on the thinning type
Analyzing selective harvest events in three large forest observational studies in North Eastern China
No full textThis study presents an analysis of selective harvest events in three 10-ha field plots with mapped trees, representing different forest successional stages in the temperate multi-species forests of North-Eastern China. Non-spatial methods of analyzing the harvest events include species and size selection preference and an assessment of harvest intensities for four species groups (identified using bivariate mixed dbh/ height distributions). Spatial aggregation increased very slightly after the harvest event, but in most cases, the change was hardly noticeable. In addition, tree selection preferences involving nearest neighbor structure units are presented, using the attributes "species mingling" and "dominance". The removals occurred within a broad array of neighborhood constellations, involving suppressed as well as dominant individuals. Previous approaches involving harvest event analysis in multi-species forests were limited to assessing size and species selection preferences. This study uses more advanced methods and presents more detailed interpretations, due to the large and detailed observational datasets and improved analytical tools that have become available recently. Models of tree growth and survival, which represent the overwhelming result of traditional observational studies, only describe a part of forest dynamics. Equally important are the modifications caused by regular human disturbance. There is thus increasing motivation for analyzing selective harvesting activities as presented in this contribution. (c) 2013 Elsevier B.V. All rights reserved
Partitioning temperate plant community structure at different scales
No full textThree stem-mapped field plots, each representing a specific forest developmental stage, were established in a temperate forest in Northeastern China: a young secondary conifer and broadleaved mixed forest (YSF), an old secondary conifer and broadleaved mixed forest (OSF), and an old-growth Korean pine and broad-leaf forest (OGF). The focus of this study is to test an environmental control hypothesis. The spatial variations of community structure (species diversity, forest density and size differentiation) were partitioned into pure environment, pure space, and spatially-structured environmental processes in the three research plots. The principal coordinates of neighbor matrices (PCNMs) method was included in the procedure of variation decomposition with respect to spatial and environmental components. The significant PCNM variables could be directly interpreted in terms of spatial scales. The results indicate that the explanatory power of the soil data was much greater in the secondary forests (YSF and/or OSF) than in the old-growth forest regarding species diversity, forest density and size differentiation. Nearly half (48.35% and 44.86%) of the variation of species richness was explained by soil properties in the young secondary forest and the old secondary forest, respectively. However, only 4.87% of that variation was explained by soil properties in the old-growth forest. Over 14% of the variation of the tree size differentiation was explained by soil properties in two secondary forests, and only 4.23% in the old-growth forest. In this study, the spatial variation of species richness and size differentiation was related to environmental variables at multiple scales. Soil variables had a significant effect on species richness and size differentiation at broader scales in the secondary forests, but mainly at medium and fine scales in the old-growth forest. The results challenge the commonly held assumption that tree distributions simply reflect patterns of seed dispersal at local scales. Crown Copyright (C) 2010 Published by Elsevier Masson SAS. All rights reserved
A model for the diameter-height distribution in an uneven-aged beech forest and a method to assess the fit of such models
No full textThis paper illustrates the application of a mixture model to describe the bivariate diameter-height distribution of trees growing in a pul e, uneven-aged beech forest. A mixture of two bivariate normal distributions is considered but the methodology is applicable to mixtures of other distributions. The model was fitted to diameter-height observations for 1242 beech trees in the protected forest Dreyberg (Solling, Germany). A considerable advantage of the model, apart from the fact that it happens to fit this large data set unusually well, is that the individual parameters all have familiar interpretations. The bivariate Johnson S-BB distribution was also fitted to the data for the purpose of comparing the fits. A second issue discussed in this paper is concerned with the general question of assessing the fit of models for bivariate data. We show how a device called "pseudo-residual" enables one to investigate the fit of a bivariate model in new ways and in considerable detail. Attractive features of pseudo-residuals include the fact that they are not difficult to interpret; they can be: computed using generally available statistical software and, most important of all, they enable one to examine the fit of a model by means of simple graphs
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