Studies on the dynamic structure of persistent and productive pasture ecosystems

(1)草地持续性的生物学因素分析：为了阐明草地持续性的生物学因素，研究了主要温带牧草在生长性能和抗逆性之间的权衡策略。此外，还对适应策略中种内遗传变异的程度与草原管理的关系进行了研究和讨论。为了了解牧场植被不稳定的原因，我们对一些牧场进行了操纵。选择性放牧是草地植被不稳定的主要原因。(2)草地物种生态：研究了部分草地植物繁殖的生态学特征。揭示了白三叶无性系繁殖的一些特性，以及红三叶的风授粉与延花一致的条件。对半天然草地蕨类植物的叶片动态进行了研究。出叶模式与累积气温和光合作用活动的季节变化有关。(3)植被动态和分布格局的模拟：建立了以分蘖为基本单元的巴伊亚草地冠层动态模型。该模型使我们能够研究草地管理和气象对分蘖密度、牧草质量、草地高度和叶面积指数动态的影响。采用一种新的方法对赤木县半自然草地植物群落的小尺度空间异质性进行了测量。用模型表达了空间异质性与物种多样性之间的关系。

(1) Analyses of biological factors of persistency : In order to clarify biological factors responsible for persistency of grasslands, adaptive strategy of major temperate grass species was investigated in relation to tradeoff between growth performance and stress tolerance. The extent of intraspecific genetic variation in adaptive strategy was also examined and discussed in relation to grassland managements. To know the reason for instability of pasture vegetation we conducted some manipulations on some pastures. Selective grazing was the main reason for instability of pasture vegetalion.(2) Ecology of grassland species : Ecological aspects of reproduction were studied for some pasture plants. Some properties of clonal reproduction in Trifolium repens and the condition for consistence of wind pollination and extended flowering in Anthoxanthum odoratum were shown. The leaf dynamics of bracken in semi-natural grassland was investigated. The pattern of leaf emergence was associated with cumulative air temperatures and seasonal change of photosynthetic activity.(3) Modeling of the vegetation dynamics and distribution pattern : A model of canopy dynamics of a bahia grass sward was constructed, dealing with a tiller as a basic unit. This model enables us to examine the effects of sward management and meteorology on the dynamics of tiller density, herbage mass, sward height and leaf area index. In semi-natural grasslands in Tochigi Prefecture, small-scale spatial heterogeneity in plant species community was measured based on a new method. The relationship between the spatial heterogeneity and the species diversity was expressed by a model.