Effects of Grain for Green Project on slope phosphorus in Loess Plateau

ObjectiveThis study aimed to explore the distribution and migration of soil phosphorus in different slope lands after vegetation restoration,and provide guidelines to evaluate the sustainability effects and environment effects of Grain for Green Project.MethodLong slopes of three different vegetation restoration slopes,including caragana shrub land,alfalfa grass land and fallow land with similar restoration ages as well as soil and topography conditions were selec-ted in Wangdonggou Basin,Loess Plateau.Farm land with millet was selected as control.Diffenrence in plant phospho-rus,soil phosphorus and soil-plant system phosphorus pool(plant phosphorus pool)among various slopes and the spatial distribution characteristics in different slope positions and soil layers were analyzed by sampling.ResultAboveground biomass,plant phosphorus content and plant phosphorus pools for different slopes after vegetation restoration showed the following rank: shrub land>grass land>farm land>fallow land,and the amounts increased from slope crest to base of slope.For soil available phosphorus,it distributed evenly along the slope direction and in profile for shrub land,but soil available phosphorus contents in base of slope were higher than other parts in other slopes.Except for the soil layer in base of slope for grass land and 0-20 cm layer for farm land,soil available phosphorus contents increased as soil layer dee-pened.Plant phosphorus pools above 0-100 cm soil layer showed increasing trend from slope crest to base.Soil total phos-phorus distribution was not greatly influenced by vegetation restoration,but mainly affected by soil parent materials.ConclusionPlant phosphorus,soil phosphorus as well as soil-plant system phosphorus pools on slopes and the distribu-tion are affected by vegetation restoration measures and different soil and water conservation effects.Shrub land and farm land can conserve soil phosphorus on the slopes at certain extents,and reduce the negative effects of running phosphorus on downstream.On shrub land and farm land,erosion loss of phosphorus is obvious.