| The Alpine grassland in Zoige is an important animal husbandry base in southwest China,and also an important ecological security barrier.The restoration and control of desertification grassland in Zoige is of great significance to the restoration of grassland production and ecological functions,the achievement of carbon sequestration and the reduction of greenhouse effect.Therefore,this paper selected three common ecological restoration patterns of desertification grassland in Zoige: enclosure plus grass(EG),enclosure intercropping shrub-grass(ESG)and enclosure plus sand-barrier and shrub-grass(ESSG),to analyze the effects of different restoration years and restoration patterns on vegetation community and soil properties of desertification grassland to quantitatively evaluate the carbon sequestration effect and the change of soil quality with restoration years under different ecological restoration measures,and to explore the effects of restoration patterns on the ecological restoration of desertification grassland system it is expected to provide technical reference for the restoration and reconstruction of sandy grassland ecosystem in Zoige.The main conclusions were as follows:(1)With the increase of ecological restoration years,the vegetation community restoration effect of sandy grassland was obvious.At 7-9a and ?15a,the height of herbage increased by 49.7% and 94.3% than ?5a,the height of shrub increased by 70.8% and 117.7% than ?5a,and the vegetation coverage increased by 10.8% and 27.0% than ?5a,the density is 1.50 and 3.25 times higher than ?5a.The aboveground biomass is 6.81 times of ?5a in 7-9a and 6.05 times of 7-9a in ?15a.The community characteristic index did not change with the increase of restoration years in EG and ESG,but decreased with the increase of restoration years in ESSG.The effect of vegetation restoration is different under different patterns.The coverage and density of ESSG were 25.3% and 31.1% lower than that of EG,but the aboveground biomass of ESSG was higher than that of EG for 20.8 times.In ESSG pattern,Simpson index,Shannon index and Pielou index were the smallest and significantly lower than EG pattern.(2)The soil properties of Zoige desertified grassland improved with the increase of restoration years.Compared to unrestoration desertified grassland,the soil bulk density in ?5a,7-9a and ?15a decreased by 12.8%,22.5% and 30.7%,and the sand content decreased by 3.9%,7.8% and 9.6%,the contents of soil organic matter and nutrients increased by 1.05,1.88 and 3.40 times,and the number of microorganisms,microbial biomass and enzyme activity increased by 1.82,2.90 and 4.82 times respectively.(3)There were significant differences in soil chemical and biological properties between different models.In general,soil nutrient content,microbial quantity and enzyme activity were the highest under ESSG.In the soil profile,the chemical and biological properties of EG and ESG were the best at 0-10 cm,while Essg was the best at 10-40 cm.(4)Ecological restoration can effectively increase carbon sequestration of desertified grassland.Compared with non-restored land,the carbon sequestration of restored land in ?15a increased 4.29-7.66 times,among which the carbon sequestration of soil increased 3.70-4.16 times,and the carbon sequestration of vegetation increased 0.61-37.89 times.The results showed that the carbon sequestration of ESG and ESSG was 0.53 and 0.64 times higher than that of EG respectively.The soil quality indexes of three restoration models were as follows: ?15a was significantly higher than 7-9a,7-9a was significantly higher than ?5a.In the 0-10 cm and 10-20 cm soil layers,there was no significant difference in soil quality index among the three restoration models,and in the 20-40 cm,ESSG model was significantly higher than EG and ESG.(5)The ecological restoration effect indiex of EG,ESG and ESSG were 0.294,0.343 and 0.423,respectively,and the differences between the models were not significant. |
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