Ecological Effect Of Bermuda Grass Cynodon Dactylon On The Water-Soil-Atmosphere System In Riparian Zone Of Pengxi River

To plant riparian plants in reservoir can effectively protect soil,purify water,beautify environment of reservoir and keep normal operation of reservoir.Up to now,there has been no relevant study,which based on water-soil-atomsphere system,about the effect of planting riparian plants on the bank of Three Gorges Reservoir.In this paper,The study area is Pengxi River,which is the first tributary of Yangtze River.The overlying water,soil physicochemical properties and soil gas content in Riparian area of Cynodon dactylon were analyzed.Meanwhile,bare area without any plants was used as a control.In addition,the effect of Cynodon dactylon on the water-soil-atomsphere system of Pengxi River was discussed.Major conclusions of this research are as follows:(1)Compared with the nutrient content of overlying water in naked area,It is found that Cynodon dactylon had partly depurative effect on the overlying water.The average of water quality index about the overlying water in the area covered with Cynodon dactylon was lower.They reduce:4.44 mg SO42-/L、0.01 mg NH3-N/L0.02mg NO2-/1.0.02 mg TN/1.0.07 mg TP/L,respectively.The water quality integrated pollution index method was used to calculate that the overlying water in overburden area and non-overburden area of Cynodon dactylon which both reached the standard,but the former is better than the latter.(2)There was spatial variability of physical and chemical properties of soil on overburden area.The content of available phosphorus and organic carbon are the highest among the elevation 165～175 m;pH and content of ammonia nitrogen are the highest among the elevation 155～165 m;while the temperature of soil surface and the content of moisture and available potassium are the highest among the elevation 147～155 m.(3)Compared with bare area without Cynodon dactylon,Soil surface temperature of the area covered with Cynodon dactylon is lower,while the content of moisture and organic carbon in the area covered with Cynodon dactylon are higher.In addition,in terms of soil pH the content of ammonium nitrogen,available phosphorus and available potassium,the former is greater than the latter.It shows that planting Cynodon dactylon on bank can reduce surface temperature,consolidate soil,keep soil moisture and draw effective nutrient from soil effectively.Meanwhile,The pH of soil is also influenced by it,which can contribute to soil improvement.(4)There was spatial-temporal variations about the content of soil carbon dioxide(CO2)and methane(CH4)in the area covered with Cynodon dactylon.As the water level drop,the content of soil dioxide(CO2)increase at first and then decrease.While the content of soil dioxide(CO2)has rising tend from January to May.The content of CH4 in soil shows single peak curve in the spatial-temporal sequence,with the maximum value in space and time was 35.12 mg · kg-1 in the height range 155～165 m and 49.15 mg · kg-1 in February respectively.At the same time,concentrations of soil CO2 and CH4 in area,which is covered with Cynodon dactylon,is higher than bare area.It shows that planting Cynodon dactylon can increase the content of CO2 in soil and the activity of microorganisms which can produce CH4.(5)According to related analysis that the concentration of CO2 and temperature have better correlation in soil,and the same to the concentration of CH4 and moisture.In the area covered with Cynodon dactylon,the concentration of CO2 and CH4 is influenced greatly.This plant can influence moisture and temperature in soil,which bring about the concentration of CO2 and CH4 difference.