Evaluation And Study On Soil Enzyme Activity And Soil Fertility In Different Developing Stages Of Chinese Fir Plantations

The changes of soil enzyme activities were discussed through the analyze of soil cellulase activity, P-glucosidase activity, sucrase activity, amylase activity, polyphenol oxidase activity, main physical and chemical properties and the soil microbial number in different developing stages of Chinese fir plantations in Dagang Mountain of Jiangxi province. Correlation analysis and path analysis were used to study the correlation between the main physical and chemical properties, the soil microbial number and the soil enzyme activities. Principal component analysis was further used to do comprehensive evaluation of soil fertility status in young forest, medium forest, near-mature forest, mature forest and over-mature forest of Chinese fir plantations.The results showed that the characteristics of various soil enzyme activities are different during the whole development process of fir plantations. Cellulase activity showed a gradually increasing trend from young forest to over-mature forest of Chinese fir plantations. (β-glucosidase activity first decreased from young forest to medium forest and then rose from near-mature forest to mature forest and decreased again in over-mature forest. Both invertase and polyphenol oxidase activities were showed an increase trend at first and then decreased. Amylase activity was increased from the young forest to medium forest but decreased in near-mature forest and then returned to the level of medium forest in mature and over-mature forest.The main physical and chemical properties and the soil microbial number of fir plantations showed an obviously deterioration in the medium forest, but recovered obviously in the near-mature forest with the environmental improvement of forest soil.The quantities of various microorganisms and the main physical and chemical soil properties affect the change characters of soil enzyme activities by direct or indirect effects in different degrees. The number of fungi, the alkalined-nitrogen content and the field moisture capacity determined the change characters of soil cellulase activity in a certain extent. The number of fungi, the content of the organic matters and the saturated water content all showed a strong determination to the change characters ofβ-glucosidase activity. The number of fungi, the total soil porosity, the total nitrogen content and the quick-acting content influence the invertase activity significantly. The number of fungi, the content of organic matters and the total porosity of the soil are all played a very important role in the change of soil amylase activity. The number of fungi, the field capacity and the alkalined-nitrogen content determine a large portion of variations in soil polyphenol oxidase activity. Soil factors such as the quantities of soil organic matters, alkali nitrogen, total nitrogen, actinomycetes, fungi and the activities of cellulase, P-glucosidase and invertase play an important role in the comprehensive assessment of soil fertility. The soil fertility levels in different developing stages were in the order of over-mature forest> mature forest> near-mature forest> young forest> medium forest.