Effects of heavymetal accumulationin apple orchard surfacesoils on the transformation processes of organic matter

研究了连续施用金属农药对苹果果园表层土壤中重金属（Cu、Pb、As）积累的影响，分析了重金属对苹果园植物残体分解和微生物生物量大小及活性的影响。获得的结果如下：1.苹果果园土壤中重金属的积累对新鲜植物残体的分解没有抑制作用，但对腐殖化植物残体的分解有明显的抑制作用; 2.苹果果园土壤中重金属的积累降低了微生物生物量在土壤有机质中的比例，进而增加了真菌生物量在总微生物生物量中的比例; 3.作为微生物活性指标的脱氢酶活性和土壤呼吸作用在重金属的存在下降低，4.苹果果园土壤中重金属累积的毒性大小为Cu>>Pb> 5.苹果果园表层土壤中水溶态和交换态Cu对苹果园植物残体的分解和微生物活性有不利影响，而微生物量则受到微溶态重金属的累积。

The effects of heavy metals (Cu, Pb, As) accumulated in apple orchard surface soils associated with the continuous application of metal-based pesticides on the decomposition of plant residue and the size and activity of the microbial biomass were assessed. The results obtained were as follows :1.The heavy metals accumulatedin apple orchard soils did not inhibit the decomposition of fresh plant residues, while inhibited considerably the decomposition of humified plant residues.2.The heavy metals accumulated in apple orchard soils reduced the proportion of the microbial biomass in the soil organic matter and, further, increased the proportion of fungal biomass in the total microbial biomass.3.The dehydrogenase activity and soil respiration measured as indications of microbial activity were reduced in the presence of heavy metals, when expressed on a soil organic matter basis.4.The toxicity of the heavy metals accumulated in apple orchard soils was in the order of Cu>>Pb>As with respect to the plant residue decomposition, microbial biomass, and microbial activity.5.The plant residue decomposition and microbial activity were adversely affected by the water-soluble and exchangeable Cu whose amount depended on the soil pH,whereas the microbial biomass by the slightly soluble heavy metals accumulated in apple orchard surface soils.