| Qinling Mountain has a gradual transition at the vegetation level, and has a clear vertical gradient. Studying on plants in Qinling has a great significance to differentiation of plantation characteristics to China's north and south. At the same time, the forest of the area is an important water resource conservation forest, as well as a significant role in soil and water conservation, climate regulation, water purification, flood mitigation, recreation and entertainment and people's living. Natural vegetations are being changed distinctly due to climate changing and man-made interference. Whereas plantations of the areas are extending constantly and plantations affect powerfully upon ecosystem. Because of the single species components of the vegetations, which differed greatly from natural forests, many problems appeared such as the cycle of material is slow, soil deteriorating, lower productivity, even ecosystem declining. So, it is necessary to study the differences between natural forests and plantations.Larix principis-rupprechtii included in Pinaceae, Larix is deciduous tree, which have adaptability to strong sunshine, and can bear with cold. It adaptable to the soil easily, living in deep and good drainage of acidic or neutral soil. It is speciality in China, living in Hebei, Shanxi, and have been introducted and cultivated to other provinces such as Liaoning, Inner Mongolia, Shandong, Shaanxi, Gansu, Ningxia, Beijing, and Xinjiang. Because of quick growth, good material, universality uses, and more resistant to adverse climate and soil, the effectiveness of wind the tree can be used for the distribution of the Yellow River Basin area, as well as mountains and alpine areas of the upper reaches of Liaohe River Forest regeneration and afforestation of barren hills and trees. Shaanxi Province has introducted Larix principis-rupprechtii to test and reforestation in Huanglong, Qinling Mountains. As in the Qinling Mountains since 1958, and up to 1986, the planting area has reached 0.3×10~4 hm~2. Larix principis-rupprechtii plantation forest in the Qinling grows well at first, but has declined markedly in recent years.Based on the data collected from 3 sample sites sites, the community structure and species diversity of the Larix principis-rupprechtii plantation in Qinling Mountains was studied and the data was analysed by the methods of one-way ANOVA and multiple comparisons. The results showed as follows:Firstly, there are 89 kinds of plants have been recorded which belong to 42 families and 39 genera in the three sample sites of the Larix principis-rupprechtii plantations in Qinling Mountain. The kinds numbers of plants for this three layer is herb layer > shrub layer > tree layer. The vertical structure of every sample site is clear and could be divided into tree layer, shrub layer and herb layer. The composition of tree layer is nearly single and pure, and Pinus tabulaeformis in the plantation are general be planted when tending of wood; the plant Rosa rubus has the biggest important value of shrub layer, and Carex lanceolata of herb layer. That means the plantation community is built up by Larix principis-rupprechtii as constructive species, while Rosa rubus and Carex lanceolata as dominant species. There are differences and significant differences among these sample sites on DBH, coverage, coverage of every layer. The Larix principis-rupprechtii number of every diameter class has the trend of normal distribution. And most of this plantation is middle aged forest and distributed in different ages; but the same age must not be the same DBH.Secondly, according to the analysis on species diversity of Larix principis-rupprechtii plantation forest, we could know that because of the different levels of habitat conditions and man-made interference, some differences exits in species diversity of these sample sites. For ANOVA and multiple comparisons onα-diversity, the results show that Richness index, Diversity index, Simpson index and Evenness index of different layers showed that herb layer > shrub layer. And Simpson index and Diversity index have significant difference while Richness index and Evenness index have no significant difference among shrub layers. While there are significant differences on Richness index, and no significant difference on other three indexes. For there are more dominant species and there bigger coverage lead to less dominance, sample site 3 has significant difference to sample sites 2 as sample sites 3 to sample sites l,and no significant difference between sample sites 1 and sample sites 2 on richness index of shrub layer. Theβ-diversity analysis showed that the three sample sites have differences among community composition in this area.Thirdly, Larix principis-rupprechtii plantation has been compared with Pinus tabulaeformis plantation forest, and the result showed that: The tree layer composition of Larix principis-rupprechtii plantation forest is nearly single and pure, while it of Pinus tabulaeformis plantation forest includes kinds of trees which with different height, and could be divied into three sub-layers. The average height, coverage and DBH of tree layer, average height and the coverage of shrub layer, and the coverage of herb layer of Larix principis-rupprechtii plantation, all have extremely significant difference to Pinus tabulaeformis plantation. It is different between two plantations: there are 89 kinds of plants which belong to 42 families and 39 genera and Larix principis-rupprechtii as constructive species, Rosa rubus and Carex lanceolata as dominant species. in the Larix principis-rupprechtii plantation. while Pinus tabulaeformis plantation have plants of 73 families, 104 genera and 125 kinds, and Symplocos paniculata and Mattenccia strathiopteri as dominant species. There is no significant difference between tree layers, but significant difference between shrub layers, and between herb layers.ANOVA and multiple comparisons on a-diversity of Larix principis-rupprechtii plantation, the results show that Richness index, Diversity index, Simpon index and Evenness index of different layers showed that herb layer > shrub layer. The Diversity index, Richness index, Evenness index and Simpson index of Pinus tabulaeformis plantation appear that shrub layer > herb layer > tree layer, as same as the trend of Larix principis-rupprechtii plantation.The evenness index of Tree layer, shrub layer and herb layer are Pinus tabulaeformis plantation > Larix principis-rupprechtii plantation; shrub layer dominance index, diversity index are Pinus tabulaeformis plantation > Larix principis-rupprechtii plantation, but the herb layer just opposite; shrub layer richness index in Larix principis-rupprechtii plantation > Pinus tabulaeformis plantation, well opposite with herb layer. |
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