Study On Soil Physical And Chemical Properties During Vegetation Restoration Period In The Hydro-fluctuation Zone Of The Three Gorges Reservoir Area

The Three Gorges Project is the world's largest hydroelectric power station and the largest engineering project in China.The water level regulation and control of the Three Gorges Dam formed a hydro-fluctuation zone with a vertical drop of 30 m and a total area of about 344.24 km2.In order to solve the environmental problems in the hydro-fluctuating zone of the Three Gorges reservoir area,and give full play to its ecological service function,such as runoff intercepton,water purification and riverbank protection,make it become the green barrier of the water quality and ecological environment of the Three Gorges reservoir area,relevant departments carried out artificial vegetation restoration and reconstruction in some hydro-fluctuation zone.In this paper,170~178 m water level elevation area with good effect of artificial vegetation restoration in 4 different hydro-fluctuation zone of the Three Gorges reservoir area was selected as research object,combining with the basic characteristics of each hydro-fluctuation zone and the water level regulation and control of the Three Gorges Dam,soil physical and chemical properties present situation and its interannual variation of each hydro-fluctuation zone was studied,and made preliminary discussion about soil environment present situation and its interannual variation trend after artificial vegetation restoration in different hydro-fluctuation zone of the Three Gorges reservoir area,to provide scientific basis for vegetation restoration and reconstruction in the hydro-fluctuating zone of the Three Gorges reservoir area.The results show:(1)In this study,afer artificial vegetation restoration of 170~178 m water level elevation area in different hydro-fluctuation zone of the Three Gorges reservoir area,the soil physical and chemical properties of 0~10 cm,10~20 cm,20~30 cm soil layers did not show obvious regular variation trend,and the significance of difference between soil layers was different.(2)In this study,afer artificial vegetation restoration of 170~178 m water level elevation area in different hydro-fluctuation zone of the Three Gorges reservoir area,the average soil bulk density ranged from 1.36 ~1.55 g/cm3,the average soil max moisture capacity ranged from 176.85~306.63 g/kg,the average soil capillary water capacity ranged from 84.14~218.43 g/kg,the average field capacity ranged from 39.06~148.99 g/kg,the average soil total porosity ranged from 26.88~40.42%,the average soil capillary porosity ranged from 12.84~28.50%,the average soil non-capillary porosity ranged from 8.22~14.04%,the average soil drainage capacity ranged from 7.44~10.56 mm.In short,the soil physical properties in a normal,the soil structure is relatively tight.The average soil pH value of each hydro-fluctuation zone ranged from 5.29~7.11.In addition to soil of hydro-fluctuation zone in Wanzhou was acidic,soil pH value of the rest hydro-fluctuation zone tended to neutral.The average soil total nitrogen content(TN)of each hydro-fluctuation zone ranged from 0.27~1.14 g/kg,the average soil total phosphorus content(TP)ranged from 0.33~0.80 g/kg,the average soil total potassium(TK)ranged from 1.56~4.59 g/kg,the average soil available nitrogen content(AN)ranged from 9.34~90.30 mg/kg,the average soil available phosphorus content(AP)ranged from 15.96~78.10 mg/kg,the average soil available potassium content(AK)ranged from 31.87~142.52 mg/kg,the average soil organic matter content(OM)ranged from 1.56~4.30 g/kg,and the average soil carbon and nitrogen ratio(C/N)ranged from 1.43~5.56.In short,soil organic matter and nutrient content were low,soil available nitrogen content was low,soil available phosphorus content was high,soil available potassium content was moderate.The results showed that the artificial vegetation restoration could keep the soil structure in the hydro-fluctuating zone of the Three Gorges reservoir area to a relatively normal state,but the effect of improving soil structure and soil fertility was limited in a short time.(3)In this study,the physical and chemical properties of each water level elevation in different hydro-fluctuating zones of the Three Gorges reservoir area did not show a significant gradient change with the water level elevation.Mainly affected by the hydrological situation,the average interannual variation of soil physical properties of each water level elevation: 175 m(54.66%)> 170 m(31.03%)>178 m(21.20%),the average interannual variation of soil chemical properties of each water level elevation: 178 m(103.97%)>170 m(90.66%)>175 m(74.30%).(4)In this study,afer artificial vegetation restoration of 170~178 m water level elevation area in different hydro-fluctuation zone of the Three Gorges reservoir area,the trend of soil physical properties interannual variation was different.The average interannual variation of soil physical properties of each hydro-fluctuation zone: Zhongxian(40.81 %)>Kaixian(40.11 %)>Wanzhou(29.65 %)>Jiangbei(21.72 %).During the years,the pH value of acidic soil increased,the pH value of alkaline soil decreased,the soil fertility increased.The average interannual variation of soil chemical properties of each hydro-fluctuation zone: Jiangbei(118.36 %)>Kaixian(67.69 %)>Wanzhou(54.71 %)>Zhongxian(54.33 %).