秦岭北坡及陕北黄土高原区山杨林初步研究

PRELIMINARY STUDIES ON THE POPULUS DAVIDIANA FORESTS IN QINLING MOUNTAINS AND LOESS PLATEAU OF NORTHERN SHAANXI PROVINCE

山杨林是秦岭和黄土区系顶极森林群落破坏后的次生林代表,秦岭上限受温度的限制,一般不超出针阔叶混交林的上限。山杨林在黄上区的北限,主要受水条件的制约,与落叶阔叶林的北限基本吻合。由于秦岭和黄土区山杨林水热条件配合的差异,群落区系组成、层片结构以及生态类型等方面,均表现明显不同。山杨林在这里皆被落叶栎林演替。

The Populus davidaina forests are representatire of secondary forest after climax forest communities destroyed in the Qinling Mountains and the Loess Plateau,its local temperature limited the upper border, so it can not be above mixed deciduous broadleaf and evergreen need- leleaf(transitional Zone).Restrained by water conditiony,it shared the northern border with the deciduous broadleaf forest.Owing to the different water and heat conditions,obvious differntiation of the plant communities showed in the composition of species,stratification and synusia as well as the ecological types of the plant.The Populus dav- idiana forest has succeeded by the deciduous broadleaf forest in the Qinling Mountains and the Loess plateau.