鄂尔多斯高原植物群落季节生长格局模拟

A simulation model of the seasonal growth pattern of plant communities in the Ordos Plateau

影响大尺度空间生态模型模拟结果与资源管理整合的因素主要有两种:一是一些模型生态学意义不明确,二是一些模型所需要的生态输入信息过于复杂。建立一个基于基本的生态学公理且输入较为简单的生态学模型,便于更加有效地服务于资源环境管理。该模型用于模拟发生严重荒漠化的鄂尔多斯高原植物群落的季节及年生长、叶片投影盖度、蒸发系数。模型首先基于降雨、蒸散、渗漏及土壤水分特性与蒸发系数(k)的关系,采用迭代的计算方法,模拟植物群落蒸散与土壤可利用水分达到平衡状态时的k值,进而采用得到广泛验证的经验公式计算植物群落的其它参数。野外N PP观察数据对模型的验证表明:模拟结果与观察值相符较好。模拟结果表明:蒸发系数小于0 .35×10 - 2 ,显示鄂尔多斯高原气候较为干燥;叶片投影盖度低于5 0 % ;除东部的准格尔旗外,植物群落净第一性生产力均低于1t/(hm2·a) ,近90 %的N PP累积集中于5至8月份。根据该文的模拟结果,在进行植被恢复时,恢复植被密度必须低于5 0 % ,放牧密度以0 .8～2 .0个/hm2

Two main factors hinder the effective incorporation of ecological information from computer models into resource management at large spatial scales: (1) some models are not based on ecologically sound principles; (2) most models based on sound principles are too sophisticated or detailed. This paper presents a generic model based on well established ecological principles with an appropriate level of detail to better server sustainable resource management decision making. The model was developed to simulate seasonal and annual growth, foliage projective cover (FPC), and evaporative coefficient in the Ordos plateau, where serious desertification happened recently. The value of k is based on the relations between precipitation, evapotranspiration, drainage and soil moisture and derived by iterative method when plant community, soil moisture and precipitation reached the equilibrium point. Other parameters of plant community were calculated by well validated empirical equations. Observed NPP data in the study area were used to validate the model, and the model results were in high agreement with observed data. The model was used to simulate evaporative coefficient, FPC, and annual production in the study area. The simulation results indicate that the k parameter is lower than 0.35×10^(-2) and implies a typical dry climate in study area. Estimated foliage projective cover of plant community is lower than 50%, and the annual production is very low——less than 1 t/(hm^2\5a) in most of sites. About 90% of annual NPP was produced during May to August (four months). Based on the results by this model, the coverage of restored vegetation should be less than 50% when vegetation rehabilitation engineering was conducted, and livestock density should be lie between 0.8～2.0 sheep unit/hm^2 in the Ordos plateau.