The Effect Of Vegetation Restoration To Soil Fertility Quality On WeiBei Loess Plateau

There was rich land resource and fragile ecological environment on the Loess gully andhilly areas. In order to utilize and protect land resource reasonably, prevent soil and waterfrom lessening and soil degradation, China held the construction engineering for "ThreeNorth"protection forest system, soil and water conservation on large scale, carried outreturning cropland to grassland or woodland. Weibei Loess Plateau demonstrating area onYongshou county Maliantian District was constructed on emphasis. The degree of cover ofplantation was increased obviously, the loss of soil and water was controlled effectively, andthe ecology was improved steeply. Many remarkable achievements have been acquired inWeibei experimental and demonstrating area. Meanwhile, plantation restoration can promotethe development and formation of soil, advance the soil quality apparently. The study try toanalyze the effect and role of plantation restoration to soil fertility quality in the degenerationecological system through observing outside and analyzing inside, evaluated the function ofmany kinds of soil fertility quality, in order to supply scientific evidence and technology ofconstruction for ecological environment in West China.1　 Vegetationrestorationcan improve the physicalproperty of soil.(1) The density and porosity of the different forest age on Loess Plateau have large distant.With the forest age increased, the density decreased, and the porosity increased gradually;they haven't obvious differences between the mixed-forests and its pure plantations; so didshrub-forest land and arbor-forest land; the natural meadowhad the most significant effect onthe density and the porosity of soil.(2) The sequence of clay content about the soil mechanical composition in differentvegetation showed as: the mature arbor-forest > the natural meadow > the sapling forest>wasteland.2　 There were remarkable different on soil chemical properties in different vegetation.(1) The restoration of vegetationcan improve the organic matter and nitrogen content of soilgreatly: the mature arbor-forest> the natural meadow > the nitrogen-fixation forest > the nonitrogen-fixation forest (the nixed-forest) > the sapling forest > farmland > wasteland. Thecontent of organic matter and nitrogen were highest in upper-layer, it decreased sharply in20-40 centimeter, and stable under 40 centimeters; the increase content of soil potassium wasii 渭北黄土高原植被恢复过程土壤肥力质量研究little compared with the organic matter and nitrogen; soil phosphor hasn't the apparentdiscipline.(2) The exchange, acidity and alkalescency: Cation exchange capacity was higher inupper-layers. CEC of the mature arbor-forest and the natural meadow's soil were biggest,shrubs, the sapling forest and the fixed-forest, it was lowest in the wasteland. There wasn'tcalcareousness reaction in soil profile of the mature arbor-forest; the content of CaCO3 wasvery little. The values of pH were similar among the mode of different usage.(3) Soil mineral elements: the content of SiO2,Al2O3,CaO and Fe2O3 were the maincomponents in soil mineral elements of different usage. There was little change about thecontent of SiO2; Al2O3,Fe2O3 and MnO's contents have no obvious difference, but they werehigher in the mature arbor-forest than the sapling forest. All soil profiles that studied in thisdissertation had stable SiO2/Al2O3 ratio, Si2O3/Fe2O3 ratio and Si2O3/(Al2O3+Fe2O3) ratiorelatively, and those ratios decreased with soil depth, while they increased little in the bottomof soil profiles. All those phenomena showed that soil mineral elements were eluviated andilluviated in some extent during soil formed.3　 Established the system of soil fertility evaluationpreliminary. According to the properties of this region, confirmed the indexes and subject functionof soil fertility quality, standardized the data menstruated, used main composition analyzed tocompute the values...