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Dynamics of Size-structured Populations and Community Organization

规模结构人口动态和社区组织

基本信息

批准号：
05454010
负责人：
KOHYAMA Takashi
金额：
$ 3.58万
依托单位：
Hokkaido University (1994)Kyoto University (1993)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

A geographically extended model of the dynamics of tree size structure of forests is proposed to simulate the change of forest zonation along latitude in response to global environmental change. To predict the response of forests to global change, it is necessary to construct functional models of forest tree populations. The size-structure-based model requires far less memory and steps of calculation compared with individual-based models, and it is easy to incorporate the dimension of geographic locations into the model to describe large-scale dynamics of forest-type distributions. The effect of increasing size growth rate, expected from increasing atmospheric carbon dioxide, was diminished at the stand-level basal area density, because of regulation by one-sided competition. Model simulations of a century-long global warming at around 3^oC predicted that (1) biomass changed in resident forests rather simultaneously in response to warming, and that (2) there was a considerable time lag in movement at the boundaries of different forest types, particularly under the existence of resident forest types that would be finally replaced. It required several thousand years after a century-long warming spell for forest types to attain new steady-state distributions after shifting. As a consequence, global warming created a zigzag pattern of biomass distribution along a latitudinal gradient, i.e., an increase in the cooler-side boundary of forest types and a decrease in the warmer-side boundary.Analyzes of the same model in terms of community organization suggested that the packing of species along a vertical forest profile is enhanced by increasing potential growth rate and by decreasing mortality. Such explanation that higher turn-over rate of forest regeneration promotes higher species diversity was rejected from the present results.

提出了森林树木尺寸结构动态的地理扩展模型，以模拟森林分区随全球环境变化而沿纬度的变化。为了预测森林对全球变化的响应，有必要构建森林树种群的功能模型。与基于个体的模型相比，基于规模结构的模型需要的内存和计算步骤要少得多，并且很容易将地理位置的维度纳入模型中来描述森林类型分布的大规模动态。由于单方面竞争的调节，大气二氧化碳增加所带来的体块生长速度增加的影响在林分水平断面积密度上减弱了。对长达一个世纪的全球变暖（3℃左右）的模型模拟预测，（1）常住森林中的生物量随着变暖而变化，并且（2）不同森林类型边界的运动存在相当大的时间滞后，特别是在存在最终将被取代的常住森林类型的情况下。经过一个世纪的变暖期后，森林类型需要数千年的时间才能在转变后达到新的稳态分布。因此，全球变暖造成了生物量沿纬度梯度的锯齿形分布，即森林类型较冷侧边界的增加和较热侧边界的减少。对同一模型在群落组织方面的分析表明，通过提高潜在生长率和降低死亡率，可以增强沿垂直森林剖面的物种堆积。目前的结果否定了森林更新周转率越高，物种多样性越高的解释。