Study On The Impact Of Oil Exploitation On Vegetation Degradation And Assessment Methods In The Yellow River Delta

In the process of oil exploitation,the leakage of crude oil pollutants and the mechanical rolling of engineering vehicles have a great impact on the surrounding environment.Crude oil pollution causes the changes in soil basic properties and microbial community structure,affecting the growth of vegetation in the region.Long-term oil exploitation will cause the ecological function degradation of the surrounding environment,and pose a serious threat to local ecological security.Therefore,exploring the impact of oilfield development on the surrounding soil,microorganisms and vegetation is of great significance to maintain the ecological security of the Yellow River Delta and promote the sustainable development of regional economy,society and environment.The Yellow River Delta Nature Reserv,with fragile ecological environment,developed oil mining industry and prominent contradiction between human and land,was taken as the research area in the present study.The influence of oil exploitation on surrounding soil,microbial community and vegetation was analyzed.Based on the field sampling data and the remote sensing data,the influence of oil exploitation on vegetation in the researched region was explored from the micro and macro perspectives,respectively.A comprehensive evaluation method for estimating the influence of oil exploitation on vegetation degradation was established.On this basis,the research scale was expanded to the Yellow River Delta region,and the landscape change characteristics of the Yellow River Delta from 2007 to 2020 were explored.Emplorying the Geographically Weighted Regressions（GWR）model,the relationship between the distance from the oil well and the fragmentation of the overall landscape and vegetation landscape was discussed,and the impact of oil development on landscape fragmentation was revealed.The conclusions were reached as follows:（1）Around the oil wells in the Yellow River Delta Nature Reserve,after crude oil entered the soil,the soil moisture content and the total nitrogen concentration were reduced,the total petroleum hydrocarbon concentration in the surface soil had not significantly relationships with the p H,electric conductivity,moisture content,total nitrogen and total phosphorus concentration of the sampled soil.（2）There were significant differences in functional groups of bacterial communities between surface（0～20 m）and subsurface（20～40 cm）soils.The C₁₅～C₂₈and C₂₉～C₃₈ components in total petroleum hydrocarbons had significant negative impacts on the bacterial biodiversity index（Shannon,Simpson and Chao1 indices）,but could result in the proliferation of some hydrocarbon-degrading bacteria.In addition,the input of a large number of organic carbon sources led to a large consumption of available nitrogen in soil,and bacteria related to nitrogen transformation had high abundance.These bacteria may help to improve the availability of nitrogen in contaminated soil.（3）Crude oil pollutants had direct and indirect inhibitory effects on plant growth,and the tolerance of different plants to TPH was different among species.Aboveground biomass of vegetation increased significantly with the increase of distance from the oil wells.The influence range of single well on the surrounding vegetation was about 40m.（4）During the past 13 years from 2007 to 2020,oil exploitation was the main driving factor leading to the fragmentation of the overall landscape and vegetation landscape in the Yellow River Delta,and its impact was mainly concentrated in the range of 2 km around the oil well.During this period,the landscape fragmentation level in the Yellow River Delta continued to increase,but due to the intervention of urbanization,the development of industries and agriculture and other factors,the impact of oil exploitation on the landscape fragmentation in the Yellow River Delta was weakened.