Effects Of Different Improved Measures On Vegetation And Soil In The Stipa Breviflora Desert Steppe

In China,degradation of steppe has become an increasingly serious ecological,economic and social problem.How to effectively governance and restore degraded steppe will be a long-term issue.In this experiment,a degraded Stipa breviflora desert steppe in Ordos Plateau of Inner Mongolia is the research object,where on the basis of analyzing the causes of degradation,different improvement measures has been implemented.Dynamic changes have been observed,including the productivity of population and functional groups,characteristics of the community,physical and chemical properties as well as biological characteristics of soil.The response of each observed index undergone variance analysis.Effects of different restoration and improvement measures have been comprehensively evaluated by principal component analysis,the purpose is to judge the recovery mechanism and determine optimized measures which improved the degraded steppe.The testing period was from 2012 to2014,research methods used combined both indoor and field experiments.Indoor experiments included screening the legumes forage for complementary sowing,field experiments included improved treatments as well as collection and analysis of vegetation and soil samples.In this type of degraded steppe,three block areas with similar conditions,have been chosen as experimental plots.Three improvement measures have been randomly assigned in each area,including:enclosure?FY?,enclosure plus reseeding?BB?,enclosure plus fertilizer?SF?,the whole area of experimental plots was protected with a fence.Free grazing area was taken as control?CK?.The main results of the study are the following:1.Comprehensive evaluation of drought-resistant ability of four species of legumes at germination and seedling stage,determined following drought resistantce ability from high to low is Melilotus alba>Medicago sativa>Astragalus sadsurgens>Caragana stenophylla2.Enclosure can contribute to the restoration of Stipa breviflora degraded steppe.Compared with the grazing area:in the first year test,urease activity increased 15.40%in the top-soil;in the second year test,nitrate nitrogen,number of fungal flora,catalase activity and underground biomass in the top-soil increased 22.64%?21.78%?16.56%and 20.66%respectively;in the third year test,top-soil population of fungi and alkaline phosphatase activity increased 70.69%and 15.74%,above-ground biomass of Stipa breviflora,semi-shrubs and Shrubs functional group and community increased 52.78%,20.27%and 16.89%respectively.3.On the foundation of enclosure,different methods of reseeding can contribute to restoration of Stipa breviflora degraded steppe,especially in the third year test,the improvement measures of reseeding are better than others,multiple species sowing?Agropyron mongolicum+Melilotus albus+Medicago sativa+Astragalus adsurgens?can significantly improve the degraded steppe.Compared with the grazing area:nitrate nitrogen and urease activity of top-soil increased 42.62%and 43.60%,nitrate nitrogen and urease activity of subsurface soil increased 15.38%and 98.46%,population of bacteria of each layer of soil increased 62.86%,212.85%and 90.55%respectively,above-ground biomass of Stipa breviflora and community increased 78.52%and 27.07%,the margalef value increased,the RFV value increased 16.62%.4.On the foundation of enclosure,the amount of fertilizer of 16g/m²?Urea?+9g/m²?P₂O₅?can significantly improve Stipa breviflora degraded steppe,and the effect can be maintained up to 2 years.When compared with the grazing area:in the first year test,nitrate nitrogen of topsoil and subsurface increased 38.65%and 16.97%,urease activity of topsoil and subsurface soil increased 22.4%and 36.25%,above-ground biomass of Stipa breviflora and perennial grasses increased 26.68%and 26.67%,the RFV value increased 16.58%;in the second year test,the nitrate nitrogen,fast phosphorus content,urease activity,catalase activity of top-soil increased 28.04%,21.21%,25.41%and29.67%respectively.Population of fungi of topsoil and subsurface soil increased 34.82%and 32.92%.