内蒙古中部地区退耕还林还草后植被与土壤性状的变化

Ecological Effects of Mandatory Conversion of Marginal Farmland to Forestland and Grassland in Central Inner Mongolia

北方农牧交错带中部的内蒙古乌盟一带退耕还林还草有10余年的历史。通过野外调查和实验室分析,探讨了不同退耕还林还草模式和年限下植物群落和土壤性质的变化,结果表明:(1)人为控制了苜蓿、沙打旺的种植周期的退耕还草工程使得退耕还草后植物群落完全不同于自然群落的演替过程,退耕年限达到6年后严重退化指示植物才大量消失;(2)退耕还林与退耕还草均起到了阻沙作用。但退耕还草在降低土壤砂含量方面效果相对明显;(3)退耕还林还草所带来的植物物种多样性变化与土壤性状变化存在正相关关系,说明土壤性状的改良与物种多样性的增加可能存在相互促进作用。可为制定合理的退耕还林还草政策提供科学依据。

Implementation of the policy ＂mandatory conversion of marginal farmland to forestland and grassland in central Inner Mongolia＂ in Ulan Qab League of Inner Mongolia, which is situated in the key area of the agriculture-pasture transitional zone in northern China, has lasted for over 10 years. Based on field investigation and laboratory works, changes of soil and vegetation characteristics under different restoration mode and different duration of restoration were discussed. It is demonstrated that （1） Due to human controlled planting of medick and erect milkvetch, the succession of plant community is quite different from its natural processes. After 6 years of restoration, indicators of serious degradation has declined remarkably; （2） Both conversions to forestland and grassland have contributed to preventing the release of sands from land surface, but this effect is more evident when converted to forestlands; （3） Changes of plant species diversity are positively correlated with changes of soil characteristics, implying that the improvement of soil feature might enhance the coexistence of plant species and high plant species diversity might improve soil conditions. The above results might contribute to a rational policy-making of ＂mandatory conversion of marginal farmland to forestland and grassland＂.