Limitation Of Vegetation Restoration In Dry Sunny-Slope Of Great Xing’an Mountains

Under logging and fires, there is serious vegetation degradation in Great Xing’an Mountains. Especially the restoration of arid sunny slope was hardly. Our study was based on the different vegetation types in arid sunny-slope, and the objective of this paper was to understand limitation of vegetation restoration in Great Xing’an Mountains. The variability of soil moisture and nutrients on slope, and the soil seed bank of arid sunny-slope, and the spatial heterogeneity of soil-vegetation on arid sunny-slope, above all were researched. The results were as follow:There were significant differences among the different vegetation of the soil moisture (SM) and soil nutrient (total carbon(TC),total phosphorus(TP),available nitrogen(AN),available phosphorus(AP),available potassium(AK),carbon nitrogen ratio(C/N)which were in order of ridge Oak forest> shrub-Grassland> Grassland. The total potassium(TK)was in order of shrub-Grassland> Grassland> ridge Oak forest. Because of the gradient was higher in sunny slope than it in ridge. So the maximum value of the SM and soil nutrient(TC,TP,AP,AK and C/N)of different slope position of grassland and shrub-grassland were in the ridge. However, the SM and soil nutrient (TC,TP,TK and AP) of down slope in grassland were higher than middle slope and up slope, and the soil nutrients(TC, total nitrogen(TN),TP,AN,AP,AK and C/N)in up slope of shrub-grassland were higher than down slope and middle slope. Our study indicated that the lack of SM and phosphorus was an important restriction of vegetation restoration in grassland and shrub-grassland. The Topography and human disturbance played important roles in changing the characteristic of SM and soil nutrients in the different parts of the terrain.The density ranges of soil seed bank were275seed/m2-977seed/m2on arid sunny-slope. The dominant families were Compositae and Rosaceae. The vegetation survey dominant families were Asteraceae, Leguminosae and Rosaceae. Soil seed bank and aboveground vegetation were similarity as follows:sunny-slope grassland<sunny-slope shrub-grassland<sunny-slope oak forest<shady slope secondary forest. The similarity of soil seed bank on different site types was that the similarity of sunny-slope grassland and sunny-slope Oak forest is highest, but the similarity of sunny-slope and shady slope secondary forest was very low. Correlation analysis show that the soil seed bank density and soil property had no significant correlation. Both the study result of soil seed bank and the survey of aboveground vegetation illustrated the sunny-slope grassland and sunny-slope shrub-grassland has potential for further regeneration.Geostatistical analysis showed that the fitted model of all variable contain spherical, exponential and Gaussian. The range of soil volume moisture was (97.4m-315.4m) higher than soil weight moisture (36.1m-180.2m). But the nugget/sill (N/S) of soil weight moisture were more higher. The range of soil nutrient was from328.9m to410.9m. The nugget/sill (N/S) of Soil total carbon (TC), available phosphorus (AP) and carbon to nitrogen ratio (C/N) was greater than25%, while the nugget/sill (N/S) of soil total nitrogen (TN), available nitrogen (AN) and aboveground biomass (AB) was less than25%. Spatial autocorrelation of soil moisture and soil nutrient was strong in arid sunny-slope and the range of autocorrelation was high. Spatial autocorrelation of aboveground biomass (AB) was strong too and the range of autocorrelation was small. Correlation analysis shows that available nitrogen (AN) was the limitation of patch vegetation evolved homogeneous vegetation.