“天气-风障-产量”系统中林带结构的马氏决策

A Preliminary Study on the Shelterbelt Structure in "Weather-windbreak-yield" System by Markov Decision Process

“天气-风障-产量”是一个复杂巨系统,若想通过该系统取得最佳效益,必须对林带结构做出优化决策。该文论述了马尔可夫决策过程(MDP)在该决策中的应用问题。利用在沈阳市康平县对农田防护林带考察中所取得的资料,依据概率论的基本原理,计算出不同结构林带对玉米气象产量影响这一生态控制系统中有关状态的转移概率;用MDP折扣模型计算出折扣率β=0.9条件下的最优策略并加以改进。结果表明:在当地天气、作物状况下所形成的复杂系统中,采用透风系数为0.35的疏透结构农田防护林带具有最优决策结果。

In ＂weather-windbreak-yield＂ system, the structure characteristics of the farmland shelterbelts are of importance for increasing the yields of crops. On the basis of the inter-disciplinary principle in relation to ecological dynamics, ecological-cybernetic principle, recta-synthetic methodology and Markov processes, mathematical modelling method, computational process and decision principle about the application of Markov decision process （MDP） are used to determine the structure of the farmland shelterbelts in relation to weather conditions. By means of the data obtained from Haizhou, Kangping County, the transition probabilities of the related states about the effects of the farmland shelterbelts are analyzed, which are of different structures on the meteorological yield departure of the maize crop on the basis of the fundamental principle of probability theory. The concepts of the two states （ i = 1 and i = 2 ）, related meteorological outputs and the action measures, ＂ventilating structure shelterbelt＂（ a = b） and ＂open-out-structure shelterbelt＂（ a = c ） are given. Then, the optimal policy and the improvement optimal policy from the computational results suggests based on the discount model of MDP with the discount rate of 0.9. The results show that the optimal policy is to choose the ecological-cybernetic action open-out-structure shelterbelt with ventilating coefficient of 0.35 in the given complex ecological-cybernetic system which is formed under the conditions of the local weather-climate and the agricultural- and forest-crop states.