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Based on investigation of vegetation and soil factors of natural valley forest closed area and non-closed area of Fuhai County, making use of plant a-diversity measure method and comparative analysis, calculating species richness and species diversity of understory vegetation, this study analyzed the recovery effect of forest vegetation after enclosure. Using principal component analysis and other methods, this study analyzed the soil nutrients of closure and enclosure forest by quantitative, evaluated the soil fertility of different community types through establish comprehensive evaluation model, explained the change characteristics of forest soil fertilitys, revealed the ecological effects of fencing. The major results were as follows:(1)Short-term enclosure (5a) (inclued Bailiu Lin, silver Yang Lin, bitter Yang Lin) which caused a significant effect on forest structure for valley forest in Fuhai county, long-term deforestation and overgrazing of the natural forest by human beings, which lead to sharp decline in the number of path-order (2-10cm) trees. Over time, it is so unfavorable for the natural forest update, while the enclosure of 5a was too short, it is difficult to ensure canopy forest from young tree.(2) Short-term closure played a significant role to the natural forest species diversity of herbaceous vegetation. Through the implementation of fencing, the number of herb species in closed area is 10 species more than enclosed areas, the number of herb species increased by 77.5%, herb layer coverage increased by 36.4%, increased by 124.8% relatively. Patrick index、Simpson index、Shannon-Wiener index of herb layer in closed area were higher than those enclosed area.(3) Closed area which promoted the physical and chemical properties of the soil. Soil moisture of the closed area was significantly higher than non-closed area on the same natural conditions. Aggregate structure of the soil in closed area was more than enclosed area, and arranged single grain of the soil was looser, porosity was larger, ventilation performance was better, soil bulk density was lower. Meanwhile, it was very effective of the closed area to improve the nutritional status of the soil organic matter, to increase the content of the alkaline solution N and available P significantly, and help to improve the salinization level of soil.(4) Using the principal component analysis method to analysis 9 soil physical and chemical indicators of the valley forest in Fuhai County, the results showed that the total contribution rate of the first two principal components was up to 82.61%. The first principal component was positively correlated with the soil moisture content and organic matter, negatively correlated with soil bulk density and total salt. The second principal component was positively correlated with the alkaline solution N, available P, available K, conductivity and pH values. Alkali solution N, available K, total salt caused greatest impact of soil fertility of 3 major forest types in Fuhai valley forest, and available P, the conductivity was relatively small. Soil fertility was positively correlated with Soil moisture, organic matter, alkali N, available K, available P, conductivity, pH, while soil fertility was negatively correlated with the bulk density, total salt. Calculate the soil fertility comprehensive index value of different forest types in different ways, the results show that:SQI (P. folia)> SQI (Populus alba)> SQI (Salix alba), SQI (closed area)> SQI (non-closed area), soil fertility closed for 5 years was higher than that of forest not closed area.
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