A General Theory for Species Coexistence in Various Forests : the Diffusion Model for Plant Communities

我调查了以下顶极森林的生长动态、竞争和补充过程：北海道大雪山的亚寒带森林（高山冷杉、条斑云杉）、东京三宅岛的暖温带森林（尖锥）、信州北岳岳山的亚高山森林（威氏冷杉、玛丽氏冷杉）和北海道芦别的早期演替的岳桦森林。我根据扩散模型分析了增长数据（Hara 1984），发现在顶极林中，冠层乔木之间的种内和种间竞争都比幼树之间的竞争弱得多，且竞争方式通常是对称的;（ii）幼树补充过程取决于林分结构属性的种特异性组合，（3）在演替早期岳桦林中，林冠树木之间的竞争是强烈的、不对称的，（4）这些结果与林冠光合作用模型相吻合，即阔叶树表现出强烈的、不对称的竞争，而针叶树表现出弱的、对称的竞争;（5）理论模型表明，干扰对植物群落空间格局动态的影响在对称竞争条件下比在非对称竞争条件下大;（vi）得出的结论是，增长和空间格局动态是由确定性因素决定的（竞争）在演替早期森林，而这些是由随机因素（干扰）顶极森林。

I investigated growth dynamics, competition and recruitment processes in the following climax forests : sub-boreal forest on Mt.Taisetsu, Hokkaido (Abies sachalinensis, Picea yezoensis), warm-temperate forest in Miyakejima island, Tokyo (Castanopsis cuspidata), sub-alpine forest on Mt.Kitayatsugatake in Shinshu (Abies veitchii, A.mariesii) ; and in an early-successional Betula ermanii forest in Ashibetsu, Hokkaido. I analyzed the growth data based on the diffusion model (Hara 1984), and found that (i) in the climax forests, both intra-and interspecific competition between canopy trees was much weaker than that between saplings and the mode of competition was usually symmetric ; (ii) sapling recruitment process was determined by the species-specific combination of stand structural attributes such as fallen-log abundance, Sasa density in the forest floor ; (iii) in the early-successional Betula ermanii forest, competition between canopy trees was intense and asymmetric ; (iv) these results obtained in the field were confirmed by the canopy photosynthesis model, i.e.broad-leaved trees tend to show intense and asymmetric competition while coniferous trees weak and symmetric competition ; (v) it was shown by a theoretical model that the effect of disturbances on spatial pattern dynamics of plant communities is larger under symmetric competition than under asymmetric competition ; (vi) it was concluded that growth and spatial pattern dynamics are governed by deterministic factors (competition) in early-successional forests while these are governed by stochastic factors (disturbances) in climax forests.