EFFECTS OF FOREST DYNAMICS ON THE LIFE HISTORY AND POPULATION DYNAMICS OF UNDERSTORY PLANTS

1. 林下环境在林冠乔木个体更新过程中发生变化。林下环境的时间变化直接影响林下草本植物的生活史和种群动态。为了解动态森林更新过程中草本植物的生活史策略，研究了森林更新对林下植物种群生活史和种群动态的影响。选取6个光照条件不同的样地，对两种森林更新类型的总状蕨（Pteridophyllum racemosum）进行了人口统计学研究；在日本中部长野县北矢竹的信象山，缝隙再生和波浪再生。对样地内所有总状翼叶植物进行标记，并在每年生长季结束时测定单个莲座的越冬芽。从无性繁殖中新招募的个体也被标记和…更多的测量。基于种群统计数据，构建了特定阶段的瞬态矩阵模型，分析了种群增长率和生活史变化对种群动态的影响。林隙更新林的种群增长率高于波浪更新林。在林隙更新林中，在封闭林冠下的遮荫条件下种群增长率较低，而在波浪更新林中，在冠层树木直立死亡的高光点种群增长率较低。大矩阵模型的敏感性分析表明，在林隙更新中，幼枝和开花植物的存活以及幼苗的补充对种群的维持起着最重要的作用。采用生命表响应试验（LTRE）对两种林分种群对应的大矩阵进行了研究。不同森林种群长期生长率的差异主要是由于光照条件的差异以及光照环境与更新方式的相互作用。这些因素通过幼虫的存活率和从幼虫到开花植物的过渡概率影响种群动态。少

1. The environments of forest understory vary during regeneration processes of individual canopy trees. Temporal changes in understory environments directly affect the life-history and population dynamics of understory herbaceous plants. To understand the life-history strategy of herbaceous plants under the dynamic forest regeneration processes, we investigated the effects of forest regeneration on the life-history and population dynamics of an understory plant population.2. Six plots with various light conditions were chosen for demography of an understory plants, Pteridophyllum racemosum, in two types of forest regeneration; gap-regeneration and wave-regeneration, on Mt Shimagare, Kita-Yatsugatake, Nagano Prefecture in central Japan. All Pteridophyllum racemosum plants in the plots were marked and the overwintering bud of individual rosettes were determined at the end of growing season each year. Newly recruited individuals originating from vegetative propagation were also marked and … More measured.3. Based on the demographic data, we constructed stage-specific transient matrix models and analyzed the effects of changes in population growth rates and life history on the population dynamics of the species. Populations in a gap-regenerating forest showed higher population growth rate than those in a wave-regenerating forest. In the gap-regenerating forest, the population growth rate was low in shaded condition under a closed canopy, while in the wave-regenerating forest the population growth rate was low at the high-light site of standing dead of canopy trees. Sensitivity analyses of mega-matrix models revealed that survivorship of juveniles and flowering plants and recruitment of seedlings most contributed to the maintenance of populations in the gap-regenerating forestry. Life-table response experiment (LTRE) were applied to the mega-matrices corresponding to the populations in the two types forests. Differences in the long-term population growth rates in respective forests were mainly caused by the differences in the light conditions and in the interaction effects of light environments and regeneration patterns. These factors influenced the population dynamics through the survivorship of juveniles and transition probabilities from juveniles to flowering plants. Less