Studies On The Effects And Mechanism Of Soil And Water Conservation Under Different Forest Restoration Types In Sloping Field Of Red Soil Region

The study was conducted at the Ecological Benefit Monitoring Station of the Yangtze River Protection Forest-the hilly red soil region of Southern Hunan Province, which locates in the small valley of Changchong Village, Langlong Country, Hengyang County of Hunan Province. And the laws of soil and water loss and nutrient losses under different forest restoration types were studied with the runoff plot method in 2002. The major results were as follows:(1) Compared with badlands under long term disturbance, four forest restoration types had significant effects in controlling soil and water loss. The effects of tea-oil camellia plantation and natural secondary forest on controlling soil and water loss were more significant than that of slash pine plantation and Chinese fir plantation. More than 80% of annual runoff and sediment loss occurred in May to August and October, which connects with seasonal distribution of rainfall.(2) The differences of organic carbon, nitrogen, phosphorus and potassium loss under different forest restoration types were very obvious. The order of organic carbon, nitrogen, phosphorus and potassium loss was as follows: CK >slash pine plantation>Chinese fir plantation>natural secondary forest>tea-oil camellia. Compared with badlands under long term disturbance, four forest restoration types had significant effects in decreasing organic carbon, nitrogen, phosphorus and potassium loss. The effects of tea-oil camellia plantation and natural secondary forest on decreasing organic carbon, nitrogen, phosphorus and potassium loss were more significant than that of slash pine plantation and Chinese fir plantation.(3) The quantity of nitrogen in the bed load was higher than that in the runoff, and the former accounts for 66.07 % ~ 88.94 % nitrogen loss. The dissolved nitrogen was dominant in runoff, which accounts for 59.02 % ~ 65.93 %. Also NH+4-N was dominant in the dissolved nitrogen of runoff, which accounts for 71.72 %. Organic carbon and total nitrogen in bed load had enrichment phenomenon. More than 65 % of annual soil organic carbon and nitrogen loss occurred in May to August and October.(4) The quantity of phosphorus in the bed load was higher than that in the runoff, andthe former accounts for 82.50 % ~94.00 % phosphorus loss. The quantity of potassium in the bed load was also higher than that in the runoff, and the former accounts for 60.25 % ~ 94.07 % potassium loss. Phosphorus and potassium in bed load had enrichment phenomenon. Compared with badlands under long term disturbance, four forest restoration types had significant effects in decreasing soil phosphorus and potassium loss. The effects of tea-oil camellia plantation and natural secondary forest on decreasing soil phosphorus and potassium loss were more significant than that of slash pine plantation and Chinese fir plantation. More than 80% of annual phosphorus and potassium loss occurred in May to August and October.(5) The main rainfall factors influencing runoff and bed load were rainfall, rain erosivity. The main rainfall factors influencing soil organic carbon, nitrogen, phosphorus and potassium loss were runoff, rainfall, rain erosivity and sediment.(6) The effect of herbage layer on controlling soil and water loss couldn't be neglected. In a sense the effect of herbage layer on controlling soil and water loss was more significant than that of tree layer and shrub layer.