Study On Soil Physical And Chemical Properties And Soil Enzyme Dynamics Of Four De-farming And Reafforestation Patterns

The engineering of de-farming and reafforestation was a complex one whose inplementrelated to state stabilization and development. The long-term research of the effect ofde-farming and reafforestation on soil fertility was an important assurance that theengineering could go on wheels. In order to evaluate the effect of de-farming andreaffbrestation on the soil fertility, establish scientific and effective vegetation restoration approachand provide the theory basis for sustainable management, the soil nutrients and enzyme activityof four de-farming and reafforestation patterns in Hongya were studied in this thesis. Theresults were mainly as follows:1 The forest and grass ecosystems both had ecological and economic benefits. Underthe influence of serious human disturbance, Hemarthria compressa's death and stoppingfertilization, the annual changes of soil physical and chemical properties fluctuated heavily. Thesoil physical properties were not improved. Soil total nutrients increased firstly and decreased then.Available nutrients changed heavily. The contents of NH4~+-N, available-P and available-Kincreased after stopping fertilization in 2004. Because of different land utilization and management,the soil organic matter accumulated indistinctively and all patterns changed differently. The pHvalue of all patterns approximately decreased.2 Soil nutrients and enzyme activity had an obvious dynamics. The seasonal ormonthly changes of soil nutrients and enzyme activity of every patterns were different.(1) Soil total nutrients of all patterns changed little compared to cultivated land. Thesoil organic matter contents of Betula luminfera were highest in autumn and lowest inspring, while the other patterns were highest in autumn and lower in winter and summer.The pH value of all patterns were lowest in winter and highest in summer. The soilhydrolysable-N contents of all patterns changed about same. The soil hydrolysable-Ncontents of Pleioblastus amarus were lowest in July, and other patterns were lowest inAugust. The variations of soil available-P contents of all patterns were different. The soilavailable-P contents of Bambusa pervariabilis×Dendrocala mopsis were short and lowestfrom Dec to next Mar. The soil available-P contents of Sinocalamus affinis were abundantin availabte-P and highest in Jul. The soil available-P contents of Betula luminfera andPleioblastus amarus were lowest in Oct and highest in Jun. The soil available-K contentsof Bambusa pervariabilis×Dendrocala mopsis were lack and lower from Oct to next Jan,but the other patterns were high in this time and got down from May to Sep. (2) The soil urease activity of Bambusa pervariabilis×Dendrocala mopsis and Betulaluminfera was lowest in winter and highest in summer, while Sinocalamus affinis andPleioblastus amarus were lowest in winter and highest in spring. The soil invertase activityof Sinocalamus affinis and Betula luminfera was highest in autumn and lowest in winter,while Bambusa pervariabilis×Dendrocala mopsis and Pleioblastus amarus were highest inautumn and lower in spring and summer. The soil catalase activity of Sinocalamus affiniswere highest in summer and lowest in spring, but the other patterns changed in sinasoidand highest in winter and lowest in spring. The soil acid phophatase activity ofPleioblastus amarus were lowest in spring and highest in summer, but Bambusapervariabilis×Dendrocala mopsis was opposite. Besides, the soil acid phophatase activityof Sinocalamus affinis and Betula luminfera was both highest in winter. The soil neutralphophatase activity of all patterns were highest in summer.3 In the text, the vertical distributions of total-K of four patterns were different. Soiltotal-K contents in subsoil of Bambusa pervariabilis×Dendrocala mopsis, Sinocalamusaffinis and Pleioblastus amarus were higher than in topsoil, while Betula luminfera wasopposite. All soil nutrients and enzyme activity in topsoil were higher than in subsoil.Obvious surface assemble effect were showed in four patterns.4 Evaluating indexes of the effects of different de-farming and reafforestation patterns onsoil fertility were based on applying factor analysis showed that the indexes of total-N,hydrolysable-N, organic matter, acid phophatase and physical properties were very important; theindexes of total-P, total-K, available-P, pH and enzyme activity were also important inevaluating soil fertility; but the index of available-K had a less effect on soil fertility evaluation..According to the IFI of four patterns and farmland, the sequence is as follows: The topsoilof Sinocalamus affinis＞the topsoil of Pleioblastus amarus＞the topsoil of Betulaluminfera＞the topsoil of farmland＞the topsoil of Bambusa pervariabilis×Dendrocalamopsis＞the subsoil of Sinocalamus affinis＞the subsoil of Pleioblastus amarus＞thesubsoil of Betula luminfera＞the subsoil of Bambusa pervariabilis×Dendrocala mopsis＞the subsoil of farmland.5 According to soil fertility integrated evaluation index and the dynamics of soilavailable nutrients, the management measures of four patterns were studied out. As far asecological and economic benefits, the patterns of Sinocalamus affinis and Pleioblastusamarus should be generalized. As long as complementing with scientific management, these patterns would have a sustainable development. The patterns of Betula luminfera andBambusa pervariabilis×Dendrocala mopsis whose values of IFI were lower could improvesoil fertility and realize ecological and economic benefits through scientific management.