Soil Moisture, Nutrient And Carbon Density In Rehabiliation Fields On The Loess Plateau

Based on Grain for Green at hilly-gully region of the Loess Plateau, soil physical and chemical properties and ecological effects of the different artificial vegetation restoration patterns which located at Shenmu-Liudaogou Watershed and Ansai-Wuliwan Watershed were studied. This study investigates the influence of vegetation restoration on soil properties and carbon density. The results are helpful for improvement of soil management and for selection of suitable tree species to grow in the Grain for Green Project. The main results are summarized as follows:(1)In the fields with of Shenmu-Liudaogou, the soil moisture under these shrubs increased with the increases in soil depth. Soil organic carbon, nitrogen and phosphorus concentrations in 0～20cm soil layers increased in comparison with that in the farmLand. But concentrations of potassium in the soil remained constant. Topsoil organic carbon and total nitrogen contents are higher than the deeper soil layers. Under shrub vegetations, plant biomass increased with the order abandoned<Medicago sativa <Caragana korshinskii. The above and below ground biomass were also differences, the former biomass were greater than the latter.(2)In the fields of Ansai-Wuliwan, soil moisture under different shrubs increased following the order Robinia pseudoacacia<farmLand<Medicago sativa<abandoned<Caragana korshinskii<Hippophae rhamnoides. Soil moisture at 0～100 cm soil layer in the Robinia pseudoacacia field decreased with increases in rehabilitation time of the plantation in comparison with that in the farmLand. Therefore, Robinia pseudoacacia consumed too much soil water, but shrubs and herbaceous vegetation recovery is more conducive to increase soil water holding capacity. The soil bulk density remained unchanged under different vegetations and rehabilitation time, but it increased with increases in soil depth.Soil organic carbon, carbon density and nitrogen concentrations in 0～40cm soil layers increased in comparison with that in the farmLand. But concentrations of phosphorus and potassium in the soil remained constant. soil nutrients and carbon density has greatly improved. Current data indicate that plantations of Robinia pseudoacacia more markedly improved soil nutrients compared to shrubs and herbaceous plants. Under different vegetations soil nutrient concentrations increased with increases in rehabilitation time.Under shrub vegetations, plant biomass increased with the order abandoned<Medicago sativa<Hippophae rhamnoides<Caragana korshinskii. The above- and below-ground biomass of Robinia pseudoacacia increased with increases in rehabilitation time, as well as the former biomass were greater than the latter. The plantations of Robinia pseudoacacia biomass increased following the order stem>root>leaf. Stem biomass and carbon density amount in Robinia pseudoacacia accounted for the largest proportion of the total biomass and carbon of the plant, respectively. However, the carbon density of vegetation in locust organs less affected by rehabilitation time.