| Inefficient shelter forest is a kind of degraded forest ecosystem. Due to the environmental destruction and the interference of human activity, the area of low efficiency has incresed, and the quality and function were also reduced. It has a serious impact on cultivation of forest resources and the development of forestry economy. So, we need to carrying out the transformation of Cypress funebris forest to build an efficient, stable, adverse-resistant plantation ecosystem and improve the service functions, such as ecological protection, biodiversity conservation, convervation of water and soil, ecological buffer, climate regulation. Besides, it can also provide technology support for capacity building of disaster resistance. At present, the study about economic-forest transformation is not widely enough, and introducing the walnut according to local conditions and combining the forest and herbage composite pattern have certain research value to the transformation of the Cypress funebris forest. It has great guiding significance on choosing a more stable and excellent transformation pattern by adopting the reasonable cultivation and technical measures, researching the soil fertility status of the forest and herbage composite pattern, and assessing the soil fertility. Cypress funebris forest in Jingyang district of Deyang city as the research object, and the spatiotemporal distribution patterns of soil microorganisms, enzyme activity and nutrient in four transformation patterns (walnut+no grass, walnut+chicory, walnut+alfalfa, walnut+orchardgrass) were studied by field investigations and laboratory analysis. The relationship amongst soil microorganisms, enzyme activity and nutrient, and the changes of soil quality were researched to provide theoretical basis for the economic transformation model of low efficiency forest. Here are the results:(1) The number of three kinds of soil microorganisms was very different among the five cropping patterns, and the ranked order was bacteria>actinomycetes>fungi. Of all the soil microorganism, the number of bacteria accounted for77%-86%, actinomycetes accounted for 14%-22%, and fungi accounted for 0.16%-0.28%. Among four transformation patterns, the total number of microorganism maximum in walnut+chicory, and pure Cypress was minimum. Besides, there were different seasonal dynamics for three kinds of microorganisms, and the lowest number of three kinds of soil microorganisms all appeared in winter. After 2 years of transformation, the number of three kinds of soil microorganisms was significantly higher than transformed 1 year(p< 0.05), except pure Cypress.(2) Four kinds of soil enzyme activities showed different performances in five cropping patterns. The enzyme activity of catalase and sucrase were the highest in walnut+chicory, but urease and alkaline phosphatase were the highest in walnut+orchardgrass, and walnut+alfalfa. The soil enzyme activity of four transformation patterns were significantly higher than that of pure cypress(p<0.01). There were different seasonal dynamics for four soil enzymes, but the lowest activity of four kinds of soil enzymes was winter. Compared with the enzyme activity after 1 years of transformation, there were significant changes in soil catalase and urease after 2 years of transformation in four patterns, while the same as the alkaline phosphatase, the difference of soil sucrase activity was not significant (p>0.05). At the same time, soil enzyme activity in the pure Cypress which had been transformed for 2 years was not significantly different from 1 year (p<0.05)(3) The soil nutrient content and pH had certain differences among five cropping patterns. Every transformation patterns could significantly improve the content of soil P and K, but pH, the content of soil organic matter, and nitrogen were significantly lower than that of pure Cypress. Among them, the content of soil total P was the highest in walnut +orchardgrass, and the maximum of soil available P, total K and available K appeared in walnut+chicory. Seasonal dynamics of soil nutrient content and pH in five cropping patterns were inconsistent. The content of soil nutrient was different in five cropping patterns due to the time of transformation. After 2 years transformation, the content of total N, total K, available K, and pH of each cropping patterns showed significant differences compared with the first year(p<0.05), and the annual dynamics of organic matter was not obvious. After 2 years transformation, The content of total P in walnut+chicory and walnut+orchardgrass had significant difference between the first and second year, the same as the hydrolysable N in all transformation patterns except walnut+orchardgrass, and available P in all transformation patterns except walnut+chicory(p<0.05).(4) The content of three kinds of soil microorganisms, four kinds of soil enzyme activities, soil nutrient, and pH all had obvious vertical distribution, which showed that all these factors were significant higher in the upper layer (0-15 cm) than the lower layer(15-30 cm).(5) Significant or extremely significant positive correlation was observed among the three major microorganisms. Soil sucrase activity was extremely significantly correlated with soil urease activity, and was significantly positively related to the soil alkaline phosphatase activity. Catalase and alkaline phosphatase had a significant positive correlation. The content of organic matter, total N and hydrolysable N had achieved significant or extremely significant, so had the content of total P, available P, total K and available K. Positive correlation between total N and pH was extremely significant, so were the number of fungi, and bacteria, the catalase, and alkaline P. The number of actinomycetes was extremely significantly correlated with catalase activity, and significantly correlated with the rest of the soil enzemy activities. There major microorganisms all had significant or extremely significant positive correlation with available P, total K, available K. Catalase activity was extremely significantly correlated with available P, total K and available K, and significantly correlated with total P. There were significant positive correlations between sucrase and available P, total K, so were the urease and total P, available P, total K.(6) Each transformation patterns generally improved the number of soil microorganisms, enzyme activities and the content of nutrient. The analyses of principal component and comprehensive evaluation of soil fertility were carried out based on five cropping patterns, and it came to a conclusion that:walnut+chicory>walnut+alfalfa>walnut +orchardgrass>walnut+no grass>pure cvpress. It is clear that soil fertility was sienificantlv improved after cypress inefficient forest transformation in Jingyang district of Deyang city, with the most effective pattern being "walnut+chicory", so we can use the "walnut+chicory" pattern as the basis of the low-efficiency forest transformation in hilly areas of the middle Sichuan to promote sustainable economic development. |
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