Monitoring And Analysis On Spatio-temporal Dynamic Changes Of Vegetation Coverage In The Middle Reaches Of Tarim River

The Tarim River Basin is the largest inland river basin in the world.It is the reserve base of high-quality cotton,grain,characteristic fruit,oil and natural gas in China.Since the 20 th century,due to economic development,population growth,unreasonable use of water resources and other reasons,the lower reaches of the Tarim River has been cut off,and the vegetation on both sides of the Tarim River has declined.The ecological environment is facing a great threat.In recent ears,in order to restore the ecological environment,a number of measures have been implemented.In order to study the effect of management measures and the dynamic change state of hydrology and ecology,this paper,based on MODIS remote sensing images and field surveys,studied the vegetation growth status,spatial distribution of plant populations and interspecific correlation under natural state.Furthermore,the vegetation restoration status under ecological restoration measures was analyzed in depth,and the benefits of different ecological restoration measures were evaluated.The main research conclusions are as follows:(1)The interannual variation of vegetation coverage in the natural conditions fluctuated slightly,but it was stable on the whole,which was closely related to the location of the study area,the growth state of vegetation and the population structure.The vegetation coverage of monitoring area Z2 and Z3 fluctuated at 24.73% and 16.42%.The vegetation coverage of monitoring area Z1 ranged from 26.07% to 30.53%,with a slightly larger fluctuation range and a slow upward trend.The vegetation coverage of Z1 increased by 4.46% in 8 years.The growth rate of vegetation coverage of Z1 was positive and fluctuated from 0.29% to 17.09%overall,with a slightly larger fluctuation range.The vegetation coverage growth rate of Z2 fluctuated from-4.07% to 6.05%,and that of Z3 fluctuated from-2.91% to 7.18%.The coverage growth rate o Z2 and Z3 fluctuated slightly,with negative value and positive value.(2)The spatial distribution pattern of Populus euphratica and Tamarix ramosissima under natural conditions showed a strong aggregation distribution in the samples.The main reason of aggregation and distribution may be related to its biological characteristics,that is,the growth environment and its own growth and reproduction characteristics.Interspecific association is an important index for the study of inter-species relationships.The trend of population association of Populus euphratica and Tamarix ramosissima was consistent.(3)Under different ecological restoration measures,vegetation coverage in the middle reaches of Tarim River fluctuated from 2012 to 2020,but showed a slow increasing trend.Among them,the vegetation coverage in the 2019 flood diversion irrigation area has the most obvious increasing trend.The growth rate of vegetation coverage in the eco-sluice area,the conversion of farmland to forest area and the fenced area was divided into two growth periods from 2012 to 2020,and the average growth rate was 2.69% from 2013 to 2016.The growth rate is larger after 2017.(4)The dynamic change of vegetation coverage during the year under the ecological restoration measures was consistent with the plant growth season.High vegetation coverage was mainly concentrated in June to September,while low vegetation coverage was found in March-May and October-November.The vegetation coverage changed with the change of month,which was consistent with the vegetation growing season.(5)The growth rate of vegetation coverage was as follows: The Fenced Area > The Eco-sluice Area > 2018 Flood Diversion Irrigation Area > 2019 Flood Diversion Irrigation Area > The Conversion of Farmland to Forest Area.This result is not only related to the characteristics of various ecological restoration measures,but also related to the geographical location,original vegetation quantity,vegetation types,soil conditions,human activities and other factors of the study area.The vegetation coverage in the study area increased at different ranges after implementing different ecological restoration measures.In order to save and improve the ecological environment of the Tarim river basin,a number of ecological measures,such as ecological water transport and returning farmland to forest,have been implemented,and the ecological environment is gradually getting better and better.It is suggested that the restoration plan should be adjusted continuously,more effective restoration measures should be optimized,and the monitoring and management of water resources should be strengthened to achieve high efficiency and energy conservation and restore the ecological environment,so as to provide good basic conditions for the economic and social development of the Tarim River Basin.