| Hainan Tropical Rainforest National Park(HTRNP),one of the first national parks established officially in China,is an important ecological insurance for Hainan Island,South China.Different from other national parks in China,HTRNP have expressway,national roads and provincial roads in different scale.Especially,the expressway G9811goes through the whole HTRNP,which may cause habitat isolation,and have a negative effect on ecological system integrity and authenticity.The patterns of the expressway and other scaled roads on landscape patterns and ecosystem integrity of HTRNP,the landscape change trend of different scaled roads were analyzed and obtained by using buffer zone analysis method,based on the road distribution and land use data in 2000,2010,and 2019.At the same time,the heavy metal content of river water and riparian soil on both sides of the expressway were sampled and studied.The main results as follow:(1)The length of roads in national parks increased by 2,134.6 km,and road density increased by 0.500 km/km~2in the national park from 2000 to 2019.The length of rural and below roads increased by 2,030 km from 2000 to 2010;The expressway added by13.6 km and Provincial Road 310 was upgraded to National Road 361 in 2019.(2)According to the change trend of the patch density index(PD),landscape shape index(LSI)and aggregation index(AI),the maximum influence range of expressway,national roads and provincial roads is 500 m,300 m and 250 m respectively.(3)The area of cultivated land,woodland,grassland and open forest land decreased within the area,which affected by roads;the area of woodland and grassland near expressway and provincial road,and the area of cultivated land near national road showed the greatest descent;the area of water,shrub land,construction land and other woodland(contain the orchard)increased,and the area of other woodland(contain the orchard)around expressway,national road,and provincial road showed the greatest rise from 2000 to 2019.(4)The dissolved oxygen(DO),chemical oxygen demand(CODcr),total nitrogen(TN)and total phosphorus(TP)values of the quality of Changhua River water on both sides of the G9811 are Class III standards and above according to the“Environmental Quality Standard for Surface Water”.Heavy metal content is low,belong to classⅠstandard,so the water quality of the basin is currently excellent,but Cd content is higher in artificial wetland that used to collect road runoff heavy metal.(5)The contents of heavy metals in soil from both sides of the expressway are as follow:The content of Cd,Cr,Ni,Pb,Cu and Zn in plot 1 gradually decreased wholly,except for Cd showed a peak at 100 m downstream,the rest of the heavy metal content reached a peak at 10 m;Cr and Pb in plot 2 gradually decreased totally,reaching a peak at 10 m;Cu and Ni first descended and then rose,reaching a peak at 100 m.The heavy metal content of plot 3 was inconsistent on both sides of the road,among which Cr,Pb,Cu and Zn fell first and then rose in the upstream,and rose first and then fell in the downstream,reaching the peak at 10 m and 50 m respectively.It is acknowledged that Cd played a key role in pollution of the soil heavy metals caused by the G9811 based on the results of the ratio of the mean value of heavy metals to the soil background value of Hainan Island,the coefficient of variation and the geo-accumulation index,which needs to be paid more attention.(6)Roads in HTRNP have a slight effect on the landscape of this area.However,there is a more obvious accumulation effect of the road within study area,based on the dynamic changes of road landscape pattern and the accumulation of heavy metals in water and soil around the road.It is acknowledged that more strategies are needed on the runoff of confluence and purification from large-scale roads such as expressway,ecological corridors of the road,and long-term environmental monitoring. |
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