Study On Dynamic Characteristics Of Meadow Steppe Grassland Vegetation Under Enclosure

Fencing is one of the effective recovery and reconstruction measures for grassland.In this study,the meadow steppe was used as investigation object.Using the field investigations,we studied the plant species,density,vegetation coverage,the height,and aboveground biomass.The varieties of plant community characteristics,species diversity and spatial characteristics of grassland were explored under different enclosure time.The results were showed as follow:(1)After the grassland enclosed,the vegetation coverage,density,the height and aboveground biomass in the fence plot under the enclosure period were significantly higher then the corresponding indexes outside the mowing plot.With the enclosed time increased,the vegetation coverage,density and aboveground biomass showed the fluctuation of down then up and down,while the height showed the variety pattern of up then down.The value of indexes were the highest in the sixth year,the height achieving 76.44 cm,and density reaching 489.67plant/m~2,the vegetation coverage amounting to 73.55%,and aboveground biomass achieving 276.15g/m~2.(2)After the grassland enclosed,the species richness index and Shannon-Wiener diversity index in enclosured plot had significantly increased than the mowing plot.But Pielou index in enclosure had significantly reduced than the mowing plot.The species richness index and Shannon-Wiener diversity showed the fluctuation of down than up with the increased in the fenced time.The species richness was high in the fifth year and the sixth year,what the value achieved respectively 23.33 and 22.67.Diversity index was the heightest in the sixth year,with the value up to 2.90.The similarity index of enclosure and no enclosure were high,species composition didn't change significantly.Adjacent years,community heterogeneity coefficient and Cody index to cover the largest in the fifth year and the sixth year,community differentiation degree was strong,and species turnover significantly.(3)Integrated above,the community index of the meadow steppe has the maximum value in the sixth year,it is showed that enclosure six years,the meadow steppe has been fully restored.(4)The coefficient of variation of the plant vegetation coverage,density and the height were greater than 10%,the dispersion degree of the values of samples was relatively strong and the date accorded with normal distribution under interannual enclosed grasslands.The plant community coverage had moderate spatial autocorrelation in the third year and the eighth year,but the remaining four years of enclosure,the plant community coverage had a strong spatautocorrelation.The plant community density and aboveground biomass had strong spatial autocorrelation at six years of enclosure.(5)Kriging interpolation maps suggested that the vegetation cover,density and biomass showed that the spatial distribution pattern of different patches,and the spatial heterogeneity of vegetation characteristics firstly increased and then decreased with the increased in the fenced time.