黄土高原半干旱区退耕还林对土壤微量元素的影响

为了探明黄土高原半干旱区退耕还林对土壤微量元素(Cu、Zn、Mn、Mo、Fe)含量的影响及其与影响因子间的关系,以甘肃省关川河流域退耕还林地和农地为研究对象,使用有效性评价、通径分析等方法研究土壤微量元素与土壤环境变量间的关系。结果表明:退耕后土壤微量元素含量随土层深度增加而减少,在表层土壤中呈一定的富集现象。退耕地Cu、Mn、Mo的有效性指数高于Zn、Fe,侧柏林地有效性综合指数高于云杉林地。偏相关分析显示,退耕还林区土壤微量元素有效态含量的主要影响因素为土壤有机质、全钾、全氮与土壤含水率;回归分析显示,土壤环境因子可解释38.1%~73.8%有关土壤微量元素含量的变异;通径分析表明,土壤全钾对土壤微量元素的直接作用最大,土壤全氮对微量元素的间接作用最大;决策分析表明,土壤全钾与土壤有机质是退耕还林区微量元素含量的决策变量,而土壤含水率是土壤微量元素的限制变量。

Effects of Grain for Green Project on Soil Microelements in Semi-arid Area of Loess Plateau

The available soil microelements are important components of enzyme, growth hormone and vitamins in plants. A better understanding of the variability of soil microelements after Grain for Green project will improve the emphasis of afforesting during the proceeding period. However, quantitative research on the effect of Grain for Green project on soil microelements is quite scarcity. The study was conducted to ascertain the effect of Grain for Green project on soil microelements (Cu, Zn, Mn, Mo and Fe) in Guanchuan river basin of Loess Plateau by applying partial correlation analysis and path analysis. The results showed that the contents of available soil microelements were promoted as a whole but diminished with the increase of soil depth after croplands were converted into forest lands. Available Fe in the soil was at a below level and could not meet the demands of plant growth. The available indices of soil microelements in forest lands were higher than those in croplands, the available amounts of Cu, Mn and Mo were higher than those of Zn and Fe. Moreover, Platycladus orientalis forest lands showed a higher comprehensive index than Picea asperata forest lands. Partial correlation analysis and path analysis showed that principal influence factors of variation in soil microelements were soil organic matter, soil total K, soil total N and soil moisture content. Both soil K and organic matter had a significant positive correlation with available Cu, Zn and Fe. Regression analysis showed that soil environmental factors can explain 38.1%~73.8% of variation in soil microelements. Decision-making analysis showed that soil K and soil organic matter were decision variables in soil microelements, while the soil moisture content was the limited variable in the experimental region. It was recommended that application of rainwater harvesting measurements can improve utilization efficiency of precipitation. The results provide valuable reference for implementing the Grain for Green project in semi-arid region.