Effect Of Enclosing On Degenerative Typical Steppe Of Zhengxiangbaiqi County In Inner Mongolia

Using the approach of spatial sequence replacing temporal sequence, we studied thespecies composition, species diversity of communities, quantitative features, vegetationspecies composition, biomass changing trend, soil bulk, soil porosity, intermittent infiltration,water retention capability, soil machinery composition, soil moisture content, soil organicmatter, the contain of total and available N, P, K and the trends along with the change of theenclosure year, through field investigations and laboratory analysis. The experiment wasconducted in degradation of typical steppe of Zhengxiangbaiqi County in Inner Mongolia inAugust2012. And a comprehensive evaluation obtained by Analytic Hierarchy Process (AHP)to find the best enclosure time for human use on both the ecological and economic. Theresults show that：(1) The number of annual or biennial plants’ showed sustained declining while theperennial vegetation types showed sustained increasing within12years after exclusion;forage plants showed better properties in enclosed4~8years, while perennial herb andsubshrub occupied an absolute advantage in the community after12years’ enclosure.Vegetation average height, coverage and density significantly (p <0.01) increased thancontrol plots; total biomass was significantly (p <0.01) increased after enclosure; biomass ofoptimal medium of forage plants showed periodic growth, and showed zero growth after10years’ enclosure. Degradation of typical steppe should make appropriate use in enclosed8~10years.(2) The plant species importance value showed distribution-concentration trend, and thesuccession sequence of dominant species as following: Convolvulus ammannii-Stipabreriflora-Cleistogenes squarrosa-Stipa breriflora-Stipa krylirii. The vegetationcommunity evenness indexes showed downward trend with one peak; the richness indexesshowed growth trend with two peaks; the diversity index appeared obvious stagecharacteristics. The similarity indexes of different sample plots were low, and the similarityindex between plots enclosed8years and control plots was the minimum while the similarityindex between plots enclosed10and12years was the maximum.(3) The soil physical properties obviously lagged behind in the speed of vegetationrestoration on the ground, and the change of10~20cm soil layer began ahead that of0~10cm soil layer. Soil bulk density in both different sample plots and different depths of soil layershowed different degrees of decreasing trend with increasing years of enclosed, while the totalporosity of performed in the opposite way. The soil water infiltration capacity graduallyincreased; soil silt and clay content increased; soil sand content reduced sand content withincreasing years of enclosed. Soil moisture content of all the soil layer grew significantly. therange ability of soil moisture content increased first and then decreased in the same soil layerand different sample plots with increasing years of enclosure, while that of each sample plotsdecreased with the increasing of soil depth.(4) The soil organic matter, total nitrogen and total phosphorus content of different soillayer in each sample plot than that of control plots grew significantly, and it was the mostsignificant in0~20cm soil layer; the soil organic matter, total nitrogen content of20~30cmsoil layer showed no obvious trend while total phosphorus content showed a trend of decrease.The total potassium content of different soil layer in each sample plot increased slightly withno significant changing trend. The available nitrogen and phosphorus content showed growthtrend with increasing years of enclosure, while the available potassium content of0to10cmsoil layer showed a trend of increased first then decreased; that of10~30cm soil layer showeda slow growth trend. The soil pH value of the same soil layer in different plots decreased withincreasing years of enclosure while that in each sample plot increased with increasing soildepth, which was just the opposite in the control plot.(5) According to the AHP scores of different sample plots, the quality order of enclosuregrassland sample plots was: E(0)<E(2)<E(4)<E(6)<E(12)<E(8)<E(10). The results ofthe study showed that degeneration area of typical steppe like that should send to appropriateuse after8~10years enclosed.