Dynamics On Microbes And Enzymatic Activities In Soil Of Different Plantations With Different Stand Ages In The Dry Valley Of Minjiang River

Vegetation restoration is a social ecosystem engineering of forestry sustainabledevelopment, which is regarded the ecological benefit as principle, looking after theeconomic and social benefit, in order to prevent from the soil erosion. Because of dryvalley of the Minjiang River is the area of atrocious weather and degradation soil, it isnecessary to improve the soil fertilization. In 1989, Pinus radiata was planted in thedry valley of the Minjiang River. In recent years, the people studied Pinus radiatawidely overseas. But so far, we did not still see a report on the effect of different plantyear of Pinus radiata plantations on soil microbes and enzyme activities in China.Performing the research of this aspect has very important theoretical and practicalmeaning to carry into Pinus radiata plantations to forest engineering and improveenvironment. Seasonal dynamics on soil microbial counts and soil enzyme activitieswere studied to understand the changes in soil fertility beneath the Pinus radiataD.Don plantations of the dry valley of the Minjiang River.(1) Regardless of the forest sites and sampling time, microbial counts in soilsshowed the ranked order of bateria＞actinomycetes＞azotobacter＞fungi.(2) Significant seasonal fluctuation was found in soil microbial counts with themaximum in autumn.(3) Soil enzyme activities were very distinct in different soil layers. Theactivities of soil enzyme were higher in the 0～20 cm soil layer than that in the 20～40 cm soil layer.(4) Soil enzyme activities were not very distinct in different seasons. In a word,soil enzyme activities were higher in autumn.(5) There are definite corelations among soil enzymes and soil nutrients.Among them bateria shows positive relationships with actinomycetes, azotobacter,catalasea and invertase. Actinomycetes shows a positive relationships withazotobacter and invertase.(6)By the principal component analyse on soil microbed, soil enzyme activitiesand soil organic matter, different plant years in Pinus radiata plantations had different soil fertility: Xiaomiao mountain of Mao county＞Xiaogou of Mao county＞Yulongof Wenchuan＞Ganbao power plant of Li county＞Zhaojiaotuo of Wenchuan＞Taoguan of Wenchuan＞Puxi of Li county＞Muka of Li county＞Shajin of Li county＞MA mountain of Li county. On the whole, soil fertility beneath the Pinus radiataplantation increased with the forest stand age. Pinus radiata plantations were helpfulto improve the soil fertilization. So it is importance to plant Pinus radiata in the dryvalley of the Minjiang River.