Study On Structure And Species Diversity Of Spruce Plantation In Northwestern Sichuan

It is a commonly used forest management practice that artificial restoration after coniferous forests been cutten and destroyed, also for plant diversity in subalpine ecosystem, there were many factors which effect the community structure and species diversity in restoration course . Five spots were choose in northwestern Sichuan, including Jinchuan, Lixian, Maerkang, Rangtang and Jiuzhaigou.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 spruce plantation was studied,and analysed the importance of these factors .These could provide theoretic foundation for spruce plantation managerment,structure optimization, perfecting artificial restoration and species diversity protaction and restoration .The main result were below.1) Spruce plantation structure of northwest Sichuan was simple .But because the spruce density and coverage was very high, the growth degree of shrub stratum and herb stratum were low under spruce plantation in a majority of places,even some places had no shrub,herb and moss.The primary arbor species were spruce,only a few of orther light-loving arbor species appeared in the spruce plantation.The high density and coverage of spruce plantation reduced the resistance ability of plantation to fire, insect, disease and orther disaster obviously. Advised fostering in some dense spruce plantation. 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 affected herb stratum were altitude and aspect, the effect of shrub stratum on herb stratum was indistinct, the maximal effect factor was Arbor stratum .Under the spruce plantation,the effect of arbor stratum on shrub and herb stratum was negative presently. The appearance of spruce regeneration seedlings was relative with aspect. Spruce renewal seedlings always appeared in gaps or under sparse canopy. The more light,the more renewal seedlings.3) The variance of vascular plant diversity of spruce piantation was distinct, the dominating effect factor were forest factors:age, Canopy density and shrub stratum coverage. The relationship between vascular plant diversity and the topography factors was indistinct. The correlation of the diversity of shrub stratum or herb stratum was negative distinctly. The variety of species composing under the spruce plantation was obvious too.The subrogation of dominant shrub and herb species was frequently, and it was relative with the variance of the forest circumstance. The diversity of herb stratum increased at first, then receded during the 30 years (12-40a). But the variance trend of herb diversity was complex, it was a undulate variance.4) The vegetation structure and species diversity were studied in spruce plantation at different time.(12a, 20a, 25a and 30a) . The results showed that: 1) the height of arbore stratum and shrub stratum increased, the height of herb stratum changed indistinctively .The distribution center of spruce height grade and diameter grade moved to the higher point gradually. Range of height grade and diameter was crescent; Coverage of arbor stratum increased at early stage of rehabilitation, then it decreased when the age of spruce plantation was 30a.The variation of shrub stratum coverage showed a similar trend, that of the herb stratum reduced continuously. Shrub stratum coverage had closely positive correlation with spruce stratum coverage; Other arbor species appeared in the spruce plantation. The dominant species of shrub stratum and herb stratum changed constantly The Importance value of some light-loving species decreased. That of dankness-loving species increased; Species diversity of the vegetation of spruce plantation depended on the shrub and herb species Shrub species diversity almost increased along the rehabilitation time, whereas herb species diversity was downtrend approximately The variation of evenness index showed the similar trend to species diversity index. But the trend of simps(?)n index was oppositive to speciesdiversity index.