Study On Structure And Species Diversity Of Secondary Vegetation On High Altitude Dark Coniferous Forest Cutting Land

Most of the virgin dark coniferous forest cutting lands were not be restored when cutten and destroyed.Natural restoration became one of the way on forest rehabilitation.There were many factors which effect the community structure and species diversity in restoration course.Four spots were choose in northwestern Sichuan,including Jinchuan,Lixian,Maerkang and Rangtang.The effect of topography factors(including altitude,slop,gradient) and forest stand characteristics factors(including age,arbor,shrub stratum coverage,herb stratum coverage) on community structure and vascular plant diversity of secondary vegetation was studied, and analysed the importance of these factors.These could provide theoretic foundation for secondary vegetation species diversity protaction and restoration.The main result were below.1) Secondary vegetation structure of northwest Sichuan was complex.The number of species became large along the time of restoration,so did height an coverage.It could effect the habitat and vegetation development.The vegetation development of arbor can effect shrub and grass development.Most of light-loving species were disappeared when shrub and grass stage becoming arbor stage.Spruce and Fir appeared on the cutting land by forty years restoration.2) The topography factors that affected arbor stratum were altitude and aspect.Age was the maximal effect factor.Arbor diversity effect also was obvious. The factors that affected shrub structure were complicated,the effect of topography factors was distinct.The effect of density of shrub on shrub stratum was obvious.The topography factors that effected herb stratum were altitude and aspect,the effect of shrub stratum on herb stratum was indistinct,the maximal effect factor was Arbor stratum.3) The vegetation structure and species diversity were studied on secondary vegetation at different restoration stage(18a,35a,40a,50a).The results showed that the height of arbore stratum increased,the height of shrub stratum and herb stratum changed indistinctively.The height of shrub stratum was maximum at the 35 years restoration stage.The height of shrub stratum became low distinctly at the 50 years restoration stage.The species diversity changed distinctly along restoration time.At the beginning of restoration,it showed high species diversity.Becaus of the arbor stratum development,the species diversity became low at the 50 years restoration stage.