中文摘要：

我国半干旱地区生态环境脆弱,环境保护的形势严峻,加强半干旱地区环境保护和生态建设势在必行。文章在内蒙古武川县选取当地常见的4种不同植被生态体系：灌木地、乔木地、苜蓿地、人工混播牧草地。采用样方法采样,进行化学分析,测定不同生态体系植被生长季初（5月）和生长季末（9月）的土壤中铅、镉、铬3种重金属的含量,分析不同生态体系对土壤中重金属含量的影响。分析表明,4种不同的生态体系之间土壤含铅量、含镉量变率差异显著,而含铬量变率不显著,铅、镉变化方向一致,均为5月明显高于9月,变化程度排序非常相似,变化最大的是灌木地和人工混播牧草地,然后是苜蓿地,最后是乔木地。所以在当地常见的植被生态体系中选择种植灌木和草对吸收土壤中的重金属比较有利。

英文摘要：

The ecological environment of semi-arid regions in China is fragile,and the situation of protecting environment is grim.So it is urgent to strengthen environment protection and ecological construction in semi-arid region.Four different vegetation ecosystems were selected in semi-arid region with Wuchuan County in Inner Mongolia as a case study： the bushes,the trees,the alfalfa land,and artificially mixed sowing grassland.The soil was sampled and carried to laboratory for analysis of the content of lead,cadmium and chromium in the soil in May and September（the start of the growing season and the end of the growing season）.It was showed that among the four different ecosystems,the lead and cadmium contents in the soil were significantly different in variability,while the chromium is not significant.And the changing rate trend of the content of lead and cadmium is consistent： the contents of the both elements in May are higher than in September obviously.The degree of the order of the content change is also very close.The biggest of the change scope is from the bushes and artificially mixed sowing grassland,followed by the alfalfa land,and finally the trees.Therefore,it is more favorable to plant shrubs and grass for absorbing heavy metals in the soil in the common local vegetation eco-system.