摘要:

We describe a model that estimates the optimal total expected cost of a wildland fire, given uncertainty in both flame length and fire-line width produced. In the model, a sequence of possible fire-line perimeters is specified, each with a forecasted control time. For a given control time and fire line, the probability of containment of the fire is determined as a function of the fire-fighting resources available. Our procedure assigns the resources to the fire line so as to minimize the total expected cost. A key feature of the model is that the probabilities reflect the degree of uncertainty in (i) the width of fire line that can be built with a given resource allocation, and (ii) the flame length of the fire. The total expected cost associated with a given choice of fire line is the sum of: the loss or gain of value of the area already burned; the cost of the resources used in the attack; and the expected loss or gain of value beyond the fire line. The latter is the product of the probability that the chosen attack strategy fails to contain the fire and the value of the additional burned area that would result from such a failure. The model allows comparison of the costs of the different choices of fire line, and thus identification of the optimal strategy. A small case study is used to illustrate the procedure.

ISSN:0045-5067    

DOI:10.1139/x94-164

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Three indices of forest stand structural and compositional diversity were incorporated into a linear programming timber harvest scheduling model to examine the trade-offs between managing stands for timber production and biodiversity objectives. The indices, based on Shannon's diversity index, characterized stand species diversity, basal area diversity, and vertical crown diversity. While harvest-level objectives were often compatible with the maintenance of vegetative diversity, the maximization of present net value was accompanied by substantial reductions in all three measures of diversity.

ISSN:0045-5067    

DOI:10.1139/x94-165

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Estimates of ambrosia beetle damage on 10 log grades, commonly used in sawmills of coastal British Columbia, were determined by the sawmill team of an Ambrosia Beetle Task Force during 1990–1992. A total of 417 ambrosia beetle attacked logs were evaluated in eight cooperating sawmills. Test logs were processed into lumber products, graded, and valued. Estimates of dollar loss per cubic metre for various log diameter classes were made. The average losses for the 10 log grades with respect to grade of lumber, with and without pinholes, ranged from $3.27 to $77.40/m3of log. Changes in sawing patterns as a result of ambrosia beetle infestation were also assessed. The loss of deep clear potential on high-grade logs increased value losses by 57%. One third of large pulp logs were sawn for lumber. Ambrosia beetle infestation of sawn large pulp logs resulted in $19.20/m3degrade loss.

ISSN:0045-5067    

DOI:10.1139/x94-166

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A mathematical programming formulation of the area-based forest planning problem can result in a large number of adjacency constraints with much potential for redundancy. Two heuristic algorithms have been proposed for reducing redundant adjacency constraints generated by the conventional algorithm. In this paper another analytical algorithm is proposed, and its efficiency and that of the conventional algorithm and the two heuristics are evaluated and compared. Comparison is based on the number of constraints, and on the computational effort needed both to derive the adjacency constraints and to solve the associated planning problem. Evaluation for several adjacency maps shows that the conventional algorithm has the largest number of constraints, with a low degree of effort in derivation of adjacency constraints and a small computational task to find a final solution. The first heuristic algorithm has the smallest number of constraints but involves a high degree of effort and a large computational task. The second heuristic has a small number of constraints with a moderate degree of effort and a large computational task, and the proposed algorithm has a small number of constraints with a low degree of effort and a moderate to large computational task.

ISSN:0045-5067    

DOI:10.1139/x94-167

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A simple system for the estimation of stem volume is presented based on the compatible stem profile and volume equations. This system can directly predict the stem volume above breast height from measurements of stem diameter at breast height and at an another point along the upper stem, and does not require any sample data for determining a parameter of volume equation. In comparison with the prediction accuracy of existing volume equations from the literature, using data fromCryptomeriajaponicaD. Don,ChamaecyparisobtsusaEndl., andPseudotsugamenziesii(Mirb.) Franco, this system has the advantage of reducing prediction error.

ISSN:0045-5067    

DOI:10.1139/x94-168

出版商:NRC Research Press    

年代:1994

数据来源: NRC