德国北部挪威云杉林可持续经营中期计划的实例分析

A Case Study in Planning for Sustainable Forest Medium-Term Management of Norway Spruce from Northern Germany

可持续森林经营理论为中期林业计划和收获调整提供了丰富的模型选择,其不同的方法可应用于各种特定的场合和不同经营类型。本文简要回顾了传统的森林计划方法,一种称为“多林分发展”的概念可以用于任意的经营系统,这个概念把森林看作由一系列林分组成,在每一个林分中可以预先制定多种经营措施的选项,每种选项都可以通过木材或其它产品以及消耗的资源计算出一个目标值。这种简单的概念可以应用到大量的不同森林经营场合,它为森林经营者制定切实可行的森林措施和评价森林经营计划提供方法。在本研究中,以德国北部一片包括21个小班的挪威云杉林班的一个中期计划为例,说明“多林分发展”这一经营系统在实际生产中的应用。每个小班具有不同的初始状态,每个小班预设了若干经营选项,根据小班的初始状态、生长模型为各种选项计算各时期的木材产出。在林班的水平上,经营目标方程包括两个组成部分:净现值和均衡木材收获值。用模拟退火的方法来优化总体目标方程值。优化的总体解决方案在为每个小班选定合适的经营选项的同时,在全林的水平上获得最优的经济和均衡产出组合。

The theory of sustainable forest management provides a rich assortment of models for medium-term planning and harvest control. The different methods are applicable in specific circumstances and different types of management. A useful theoretical framework that can be used in any arbitrary system of management is the concept of multiple forest developments. The concept of multiple forest developments realizes that a forest consists of a discrete number of stands and that different treatment options can be defined for each stand. Each option has a value that can be calculated, delivers timber and other products and consumes resources at specified time periods. This simple concept can be applied in a great number of different forest management situations. It provides a methodical framework for producing practical management plans for foresters and for evaluating scenarios of forest development. In the present study, an example of Norway spruce compartment in Northern Germany including 21 stands is used to illustrate the approach. Each stand was prepared with options and their periodic timber outputs were implemented by their initial status and growth and thinning models. On the compartment level, the objective function includes two components： Net Present Worth and Even Flow of the timber harvest. The solution is obtained using the method of Simulated Annealing. The global optimized solution provided proper option for each stands as well as the best combination of two components for the entire compartment.