摘要:

This study gives an account of dry weight equations in biomass fractions of seven hardwoods from 90 plots in a hemiboreal forest zone in southeast Norway. The following species were investigated: goat willow (Salix capreaL.), grey alder(Alnus incana(L.) Moench.), black alder(Alnus glutinosa(L.) Gaertn.), silver birch(Betula pendulaRoth), rowan(Sorbus aucupariaL.), aspen(Populus tremulaL.), and european ash(Fraxinus excelsiorL.). Sample trees were collected in stands—pure in species—from abandoned land, forest sites, and brook valleys below maximum shoreline height since the last glaciation (marine limit). The highest predictive equations appeared to be natural logarithms with base e. The equations have been generated from three models depending on their ability to explain the whole variation in the regression. In most cases over 80% of the variation in the dependent variables can be explained by the independent variables in the linear model. For various biomass fractions, the coefficient of determination(R2)decreases in this order of rank: dry weight of stemwood including bark, branchwood including bark, and foliage. Analyses of regression coefficients showed highly significant differences between most of the hardwoods with regard to tree components. However, no difference was found between goat willow and grey alder for branchwood including bark. For these species, there was no statistical difference in the intercept at the 5% significant level. Percentage bias increased from stemwood including bark (1.47%) to foliage (32.71%). Types of equations and selection of parameters in the regressions are discussed.

ISSN:0282-7581    

DOI:10.1080/02827589509382900

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The biomass ofPinus sylvestris, Pinus contortaandPinus cembraseedlings that were raised in three different growing media, as well as of naturally regeneratedP. sylvestrissaplings, was estimated using functions based on variables measured non‐destructively. These included stem diameter, seedling height, number of needles and branches, length of the longest needle, and projected seedling or sapling crown area. Projected area of a two‐dimensional video image of the seedling or sapling was measured using computer‐based image analysis. The variables were tested in all possible combinations to achieve the best biomass estimate. Projected area alone explained more than 97% of the variation in seedling or sapling mass. Addition of stem diameter increased the degree of explanation to more than 98%, whereas the other variables did not contribute further. Separate functions for species and growing media resulted in more precise estimates than if general functions were used.

ISSN:0282-7581    

DOI:10.1080/02827589509382901

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Regression functions are presented for estimating the thinning response of the annual‐ring‐width increment in single trees of Scots pine(Pinus sylvestrisL.) and Norway spruce(Picea abies(L.) Karst.). The thinning response of a tree is defined as the ratio between the actual annual‐ring width and the corresponding assumed annual‐ring width unaffected by thinning. Optional growth models are presented which isolate the thinning response. The models allow for a quantitative determination of the role of thinning within the complex growth process. Given knowledge of the time, intensity, and method of the thinnings, the models allow estimation of the total response to thinning. This response is influenced by all previous thinnings—active as well as natural, induced by crowding—in the stand in question.

ISSN:0282-7581    

DOI:10.1080/02827589509382902

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In solving a wood procurement problem using linear programming, one obtains a static solution that is found simultaneously, for instance, by the Simplex technique. Therefore, general linear programming is useful when dealing with large‐scale and strategical problems. By using the formulations of dynamic linear programming presented in this study, local decision makers are provided with the advantages of an approximation tool for tactical planning situations. The models were used (1) to implement a local approach to tactical planning; and (2) to consider local and time‐variable aspects of wood procurement. In particular, as an example, a local seasonal cost effect is investigated; the results obtained are compared with results obtained by conventional higher level models. Both model structures (conventional and local) covered the same wood procurement system and the same planning horizon, but the procedure developed was more flexible and suitable for multi‐stage planning at the local level. The procedure was not as efficient computationally as the conventional procedure, but future developments in the computer industry can be expected to provide more computational capacity for processing and increasing number of variables. Using the following local procedure developed, the same tactical problem could be solved with higher precision because the system is closer to reality; the magnitude of the dynamic inconsistency was diminished.

ISSN:0282-7581    

DOI:10.1080/02827589509382903

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The practical utility of chlorophyll fluorescence to forestry applications is reviewed. Major subjects include a review of past applications, sampling protocols, important fluorescence features, and instrumentation. Applications including the study of various stress effects, seasonal effects, and comparative sun/shade leaf physiology are provided. Chlorophyll fluorescence has been used mainly in applied research, rather than directly in operational forestry, but work has begun in this area. Sampling protocols include the selection and treatment of samples before assessment, and control of environmental conditions during assessment. Instrumentation is evaluated based on accuracy, versatility, ease of operation, and cost. Chlorophyll fluorescence ranks high among stress detection tests in forestry applications, because it is rapid, reliable, non‐destructive, quantitative, diagnostic, and the physiological basis of the assessment is understood.

ISSN:0282-7581    

DOI:10.1080/02827589509382904

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0282-7581    

DOI:10.1080/02827589509382905

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor