| Tibet is one of the five traditional pastoral areas in China,and its natural grassland area accounts for about 21% of the country's natural grassland area.Due to global warming,frequent natural disasters,grassland overgrazing and intensified human activities in recent years,natural grassland degradation,desertification,and salinization are serious problems.In addition to reducing livestock pressure and improving pasture management,artificial pasture is also an effective solution to promote the coordinated development of ecological economy.However,due to the limitation of the climate and soil conditions in the alpine areas,suitable areas for artificial pasture cultivation are limited,the economic cost is high,and the ecological impact is large.Taking the artificial pasture in five counties of Nagqu prefecture of Tibet as the study area,understand the status of artificial pasture through field investigation of typical projects,deploying quadrat to compare the differences in soil physical and chemical properties and vegetation community characteristics of artificial pasture with different management methods,natural pasture,and fencing natural pasture.Combined with the GF-1 remote sensing image data,the above-ground biomass of typical artificial pasture was retrieved,the effects of artificial pasture plantation on soil physical and chemical properties and vegetation community in alpine region of northern Tibet were explored.The risk of artificial pasture cultivation was evaluated.The main conclusion lies in:(1)Effects of artificial pasture on soil physical and chemical properties: there are significant differences in soil temperature,soil texture,total phosphorus and total potassium between artificial pasture with different management methods,natural grasslands,and fencing natural grassland.The differences in soil moisture content,soil bulk density,soil PH and soil organic matter had no significant difference(?=0.05).Artificial pasture can significantly improve soil texture,reduce soil temperature and increase soil moisture content.(2)Effects of artificial pasture on vegetation communities,there are significant differences in vegetation height between artificial pasture,natural grassland,and fenced grassland.The height of artificial pasture community is significantly higher than that of natural grassland,and the difference in community coverage is not significant(? = 0.05).Artificial pasture has significantly reduced plant biodiversity in landscape scale.(3)Using GF-1 remote sensing data and field-measured above-ground biomass data,through regression analysis,it was found that the quadratic polynomial curve equation fits well.The inversion results show that the above-ground biomass of artificial pasture is greater than that of natural grassland and it was found that the above-ground biomass of the artificial pasture run by corporation was larger than that of the artificial pasture run by local community.(4)Ecological risks of artificial pasture planting: The management method of the artificial pasture run by corporation has lower risk than that of the artificial pasture run by local community.Due to improper management of artificial pasture run by local community,grassland degradation and abandonment are more likely to occur.There are risks of arid and barren soil in abandoned artificial pasture.The community species is similar to that of natural grassland,but the poisonous weeds invade seriously.Grassland coverage,height and biomass are lower than natural grassland,grassland is in extreme degradation.In conclusion,the yield rate of artificial pasture planting input is low and the soil environmental impact and ecological risks are large in the alpine ecological fragile areas.In the future,it is still necessary to improve the management of artificial pasture and the level of science and technology,optimize the layout and development scale of artificial pasture planting,and promote grass-animal balance and grassland animal husbandry development. |
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