退耕还林还草对黄土高原坡地磷素的影响

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

  • 摘要: 目的探讨不同植被恢复退耕坡面土壤磷素的分布及其迁移特征,为退耕还林还草工程的可持续性及其环境效应评价提供参考.方法选取黄土高原中部王东沟小流域退耕年限、土壤和地形条件较一致的柠条灌木地、苜蓿草地和荒地等3种典型植被恢复的长坡面为研究对象,以谷子农地为对照,通过采样测定分析不同植被恢复坡面的植物磷、土壤磷和土壤—植物系统磷库(植物磷库)的差异及其在不同坡位、土层间的空间分布特征.结果不同植被恢复样地的地上生物量、植物磷含量和植物磷库均表现为灌木地>草地>农地>荒地,且从坡顶向坡底方向逐渐增加.对于土壤速效磷,灌木坡地在坡面和垂直方向分布较均匀,其他样地则总体表现为坡底速效磷含量较高;不同土层间相比,除草地坡底部位及农地0~20 cm土层外,其余土层土壤速效磷含量整体上随深度增加而增加.0~100 cm土层以上的植物磷库均表现出从坡顶向坡底逐渐增加.土壤全磷分布受退耕植被的影响不明显,主要受土壤母质的影响.结论退耕坡面植物磷、土壤磷和土壤—植物系统磷库及其分布受恢复植被措施及其不同水土保持效益的影响;灌木地和草地对退耕坡地磷素具有一定保持作用,能够减少流失的磷素对下游水体的影响,而荒地和农地表现出明显的磷素侵蚀流失趋势.

     

    Abstract: 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.

     

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