Studies On The Changes In Soil Fertility Of E.urophylla×E.grandis Plantation

It was analyzed comprehensively that indexes of soil physical properties, soil chemical properties, soil microorganisms and soil enzyme activities in Fujian E.urophylla×E.grandis plantation of different ages,were measured by standard plot sampling and normal lab analysis. The Influences of Planting E.urophylla×E.grandis on the soil fertility are also discussion.The results obtained are showed as follows:1. The E.urophylla×E.grandis plantation would improve soil physical properties. The experiment results also indicated that it decreased soil bulk density,promoted maximum water capacity,field capacity and soil total porosity,non-capillary porosity,capillary porosity.And field capacity of 2,3,4,7,9-year-old E.urophylla×E.grandis plantation are significantly different with the mixed stands of Cunninghamia lanceolata and Michelia macclurei,while the others are significantly remarkable difference,gradually improved properities of tested soils.2. E.urophylla×E.grandis plantation have anegatively effect on soil chemical properties,With the growth of E.urophylla×E.grandis, there are evident decline on the level of N,P,K,soil-orgnic-matter,Microelements(Fe,Mn,Cu,Zn,B)and CEC .Cluster analysis showed soil chemical properties of individually depth(0-20cm,20-40cm,40-60cm)and rhizosphere soil vary at four-years-old E.urophylla×E.grandis plantation. Namely,soil chemical properties of<4-year-old E.urophylla×E.grandis plantation are slightly significant,but that of≥4-year-old E.urophylla×E.grandis change much negatively . So,older E.urophylla×E.grandis age have more intensively impact on soil chemical properties than younger E.urophylla×E.grandis age.3. E.urophylla×E.grandis plantation restrained soil microorganisms and soil enzyme activities which gradually declined with the growth of E.urophylla×E.grandis.4. Canonical correlation analysis on soil enzyme activities and trace element contents in E.urophylla×E.grandis plantation soil showed that among the test elements,B,Fe,Cu affected soil unease and peroxidase activity, and Zn and Mn affected enzyme activity.Both Zn and Mn increased soil proteinase activity. Zn decreased the activities of soil unease and peroxidase.B declined the activities of soil phosphatase and peroxidase.5. It was evaluated by two quantitative methods:the integrated soil quality index(QI) and soil deterioration index(DI).It also showed that 2-year-old E.urophylla×E.grandis plantation>3-year-old>3-year-old the mixed stands of Cunninghamia lanceolata and Michelia macclurei>4-year-old>7-year-old>9-year-old.So growth of E.urophylla×E.grandis declined soil quality.6. Land capability decline of plantation have become a key and general concern. It is necessary to take effects of technical measures,strengthen effects fertilizer and organic fertilizer application, otherwise, spread mixed forest model,appropriate rotation logging slash recurrence,scientific cropping system is also vital to keep the harmony between mankind and environment.