Study On Plant Species Diversity And Soil Nutrient Of Artificial Forest In Loess Plateau Of Western Shanxi Province

With the several kinds of typical man-made forest communities located in the Loess Plateau of Western Shanxi Province as the object of study, by means of such methods as field survey and laboratory experiment, and with the species composition of undergrowth vegetation and the diversity of undergrowth vegetation as the research index, this paper makes a contrastive analysis on the impact of different forest ages, different densities and different exposures on the diversity of the undergrowth vegetation in different types of man-made forests. In addition, with the organic matter, total nitrogen and available phosphorus in the undergrowth soil as the research index, the paper analyzes the impact of different forest ages and different types of artificial forests on soil nutrient status, in hope to supply a scientific basis and theoretical reference for the restoration and revegetation of the vegetation in the Loess Plateau of Western Shanxi Province for soil and water conservation, and for the sustainable sound development of the existing vegetation. The research result shows:An analysis on undergrowth species composition:there are45species of Pinus tabulaeformis tabulaeformis forest, respectively belonging to36categories and18families; there are52species of Robinia pseudoacacia tabulaeformis forest, respectively belonging to40categories and20families; there are57species of Platycladus orientalis tabulaeformis forest, respectively belonging to48categories and23families;there are36species of plants under the mingled forest of Chinese pine and robinia pseudoacacia as well as of platycladus orientalis and robinia pseudoacacia, respectively belonging to29categories and17families All the undergrowth vegetations in man-made forest communities are dominated by compositae plants, grasses, leguminous plants and rosaceous plants. The community similarity between different types of man-made forest communities is fairly high, and man-made forest communities are partly similar to natural grasslands, but less to natural secondary forests.An analysis on the influencing factors for the diversity of the species under different types of man-made forest communities:The diversity of the vegetation species under different forest ages of pinus tabulaeformis forests and robinia pseudoacacia forests increases first and then decreases along with forest age prolonging, while that under platycladus orientalis forest decreases all the way; the diversity of the vegetation species under different densities of pinus tabulaeformis forests decreases as density increases, while inside Robinia pseudoacacia forest, the diversity of the low-density and medium-density forest stand species are highest, and that of the high-density ones is lowest; for pinus tabulaeformis forest and robinia pseudoacacia forest at different slope exposures, the species diversity is greater on shady slope than on sunny slope, while for platycladus orientalis forest, it is greater on sunny slope than on shady slope.For a contrast between different types of man-made forest communities, the diversity of the total undergrowth vegetation is that pure forest> mixed broadleaf-conifer forest> natural secondary forest; the diversity of the species on shrub layer is that mixed broadleaf-conifer forest> natural secondary forest> pure forest; that on herbaceous layer is that mixed broadleaf-conifer forest> natural secondary forest, and the diversity of the species on the herbaceous layer in artificial pure forest is better than in natural grassland.The content of soil organic matter and total nitrogen in different forest ages of pinus tabulaeformis forests, Robinia pseudoacacia forests and platycladus orientalis forests is on the rise with forest age prolonging, while the content of available phosphorus is on a declining curve with forest age prolonging. Hereinto, there is a significant positive correlation between the contents of total nitrogen and soil organic matter in soil, while there is a significant negative correlation between the content of available phosphorus and forest age.For a contrast between different types of man-made forest communities, the content of soil organic matter and total nitrogen manifests that mixed broadleaf-conifer forest> robinia pseudoacacia forest> platycladus orientalis forest> pinus tabulaeformis forest, and the content of available phosphorus manifests that platycladus orientalis forest> mixed broadleaf-conifer forest> robinia pseudoacacia forest> pinus tabulaeformis forest. Compared with natural vegetations, the content of soil organic matter, total nitrogen and available phosphorus inside Robinia pseudoacacia forest and mixed broadleaf-conifer forest is higher than natural secondary forest and natural grassland, while all that inside pinus tabulaeformis forest is lower than natural vegetations. When compared to bare land, it can be found that the content of soil organic matter and total nitrogen in man-made forest communities is higher than bare land, and the content of organophosphorus is lower than bare land.