Study On Characteristic Of Nutrition Envolvement In The Process Of Eco-rehabilitation In The Zhifanggou Watershed On Loess Hilly Region

The nutrition recycling and balancing characteristics of different vegetation of arbor, shrub,herbage and different land types of plain field, sloping field and terrace were deeply studied thatusing Zhifanggou watershed as model in plot scale and watershed scale. The nutrition evolvementcharacteristics were analyzed in quantitative in the process of eco-rehabilitation such as vegetationrestoration and land use types adjustment. The main results were as follows:1. The influence of arbor, shrub, herbage vegetation on soil erosion were different. The runoff amount of herbage vegetation was 1248m3/km2 per year, while shrub and arbor vegetation were 843 m3/km2 and 2079 m3/km2, respectively. The sediment amount of herbage vegetation was 4.6 t/km2 per year, while shrub and arbor vegetation were 1.0 t/km2 and 2.6 t/km2, respectively. The sediment amount of different vegetation and its herbage vegetation cover degree showed opposite trend.2. The influence of arbor, shrub, herbage vegetation on nutrition discharge were different. The N discharge amount of arbor vegetation though runoff was 5.68kg/km2.a, while shrub and herbage vegetation were 3.32 kg/km2.a and 2.49 kg/km2.a, respectively. The P2O5 discharge amount of arbor vegetation though runoff was 0.29 kg/km2.a, while shrub and herbage vegetation were 0.22 kg/km2.a and 0.17 kg/km2.a, respectively. The N discharge amount of arbor vegetation though sediment was 2.69 kg/km2.a, while shrub and herbage vegetation were 1.18 kg/km2 and 7.51 kg/km2.a, respectively. The P2O5 discharge amount of arbor vegetation though sediment was1.51 kg/km2.a, while shrub and herbage vegetation were 0.54 kg/km2.a and 2.78 kg/km2.a, respectively.2. The nutrition recycling velocity of arbor, shrub, herbage vegetation which beyond the surface were different. The N recycling velocity of arbor vegetation was 0.789, while shrub and herbage vegetation were 0.742 and 1.000, respectively. The P2O5 recycling velocity of arbor vegetation was 0.881, while shrub and herbage vegetation were 0.758 and 1.000, respectively. The nutrition surplus amount of arbor, shrub, herbage vegetation of each year were different. The N surplus amount of arbor vegetation was 333.0 kg/km2.a,while shrub and herbage vegetation were 508.5 kg/km2.a and 597.0 kg/km2.a, respectively. The P2O5 surplus amount of arbor vegetation was 333.0 kg/km2.a, while shrub and herbage vegetation was 423.0 kg/km2.a and 531.0 kg/km2.a, respectively.4. The nutrition recycling and balancing characteristics of plain field, sloping field and terrace were different. The treatment of MNP, N1P1, MNP of plain field, sloping field and terrace nutrition surplus amount were as follows. The N surplus amount of plain field was 1.022t/km2.a, P2O5 was 5.657 t/km2.a, the N deficit amount of sloping field was 12.04 t/km2.a, P2O5 was 21.19 t/km2.a, while the N surplus amount of terrace was 10.493 t/km2.a, P2O5 was 10.731 t/km2.a.5. Because of eco-rehabilitation and comprehensive harness were implemented in Zhifanggou watershed. The area of arbor, shrub, herbage vegetation increased ceaselessly, so the nutrition surplus amount increased ceaselessly also. The area of sloping field decreased year after year, while the area of terrace increased year after year. So the nutrition surplus amount in terrace increased year after year, while the nutrition deficit amount in sloping field decreased year after year. With the eco-rehabilitation and comprehensive harness are implementing in Zhifanggou watershed more and more, the harness degree are increasing ceaselessly. The nutrition discharge amount though soil erosion are decreasing ceaselessly. The nutrition discharge amount is decreasing ceaselessly also though comprehensive harness. The healthy system of nutrition recycling and balancing of Zhifanggou watershed is forming and developing.