Life Zone Ecology of The Bhutan Himalaya II.

不丹喜马拉雅的生活区生态学2。第二阶段的研究重点是不丹喜马拉雅山脉的亚热带地区。对桑科什河沿岸干谷的气候分析表明，造成干谷发生的主要因素是强烈的南风（谷风），其风速在当地时间14、15时达到最大值。高温、水汽压梯度大、强风使蒸发蒸腾量大。研究了不丹几条主要河流中游的地貌和构造运动。王底峰令宗古河流沉积层理面显示了王底峰令下游相对上游的抬升，暗示了南高喜马拉雅带的抬升。本文对亚热带1000 ~ 2500 m植被结构及其人为改造进行了研究。天然林中有Altingia excelsa、Exbucklandia populnea、Sloanea sterculiaceus、Toonaciliata、Acrocarpus fraxinifolius等热带植物，但由于人类不断的迁移和覆被等干扰，使天然林变成了种类较少的月桂类森林。沿着地形-土壤梯度的干旱-干旱梯度和家畜放牧进一步强化了这种格局。对农田杂草和草场进行了广泛的研究。在不丹中部，在阿苏山和库居山上发现了一个类似Pleioblastus牧场的矮竹草原，以矮竹为主，Yushania。这是一种常绿的竹子，牛和雅库一年四季都在吃。草原也被改造成荒地，以蒿属、塞内西奥属、鲁梅属和Arundinaria为主。

Life Zone Ecology of The Bhutan Himalaya II.The second phase study is focused on the subtropical part of the Bhutan Himalaya. Climatic analysis of the dry valley along the Sankosh river clarified the main factor which cause the occurrence of dry valley is the strong southerly (valley) wind which reach maximum velocity at 14 or 15 local time when the temperature reaches maximum. The high temperature, the large gradient of water vapour pressure and the strong wind make the evapo transpiration large. Landform and tectonic movement of Bhutan was studied in middle reaches of several main rivers. Bedding planes of older fluvial deposits at the Wangdiphodrang Dzong indicates the relative uplift of the lower reaches from WangdiyPhodrang against the upper ones and suggests the uplift of the southern High Himalaya belt.Vegetation structure and its human modification were studied in the subtropical zone ranging from 1000 to 2500 m. In natural forests, there are many tropical elements such as Altingia excelsa, Exbucklandia populnea, Sloanea sterculiaceus, Toonaciliata, Acrocarpus fraxinifolius, etc. , however, the repeated human disturbances such as shifting cultivation and coppicing had modified the forests into less diversified lauro-fagaceous forests. The pattern is further intensified by xeric-mesic gradients along the topo-edaphological gradients, and grazing by domestic animals. Farmland weeds and pastures were studied extensively. A dwarf bamboo grasslands like Pleioblastus pastures on Mt. Aso and Mt. Kuju was found in central Bhutan which is dominated by dwarfbamboo, Yushania. It is an evergreen bamboo grazed by cow and Yaku throughout the year. Grasslands are also modified into waste lands dominated by Artemisia, Senecio, Rumex and Arundinaria.