蚯蚓介导下镉胁迫对土壤理化性质和玉米生长的影响

Effects of cadmium stress on soil physical and chemical properties and maize growth mediated by earthworms

为了探讨重金属如何驱动土壤动物的行为(垂直分布)进而影响土壤理化性质与作物生长,以赤子爱胜蚓为研究动物,利用室内模拟实验系统研究了镉胁迫下蚯蚓的生理响应、趋避行为及其对玉米生长的影响.结果表明,土壤镉污染影响了蚯蚓生理特征,总体上造成蚯蚓体内超氧化物歧化酶(SOD)活性下降而脂质过氧化产物(MDA)含量增加,这种不利效应导致蚯蚓作出了趋避响应,表现出向土壤深层分布的趋势.例如,处理第50 d,10 mg·kg^-1和30 mg·kg^-1镉处理组表层(0—10 cm)蚯蚓数量分别下降19.73%和22.17%,且其垂直分布与蚯蚓体内SOD活性显著负相关、与MDA含量显著正相关.蚯蚓垂直分布还改变了土壤有机质、碱解氮与速效磷含量,处理第50 d,30 mg·kg^-1镉处理组土壤中有机质、碱解氮、速效磷含量较对照组分别增加29.24%、15.50%、17.37%,且与蚯蚓分布数量极显著正相关.此外,玉米生物量和株高与土壤碱解氮、有机质、速效磷含量之间显著正相关.因此,土壤镉胁迫改变了蚯蚓的垂直分布,其行为变化改善了深层土壤营养状况(植物根系主要分布区),促进了玉米苗的生长,本研究成果可为镉污染对土壤生态系统的生态风险性评价提供新的实验依据和数据支撑.

In order to explore the effects of heavy metals on behavior(vertical distribution)of soil animals and the subsequent indirect impacts on soil physical and chemical properties and plant growth,the present study used Eisenia foetida and maize as experimental animals and plant,respectively,to solve this problem.The results showed that cadmium affected physiological characteristics of earthworm individuals,such as generally reduced SOD activity but increased MDA content,which subsequently affected the distribution of earthworm,i.e.,led to the number reducing of earthworm distributed in surface layer.The number of earthworms in surface layer decreased by 19.73%and 22.17%when the soil exposured to 10 mg·kg^-1 and 30 mg·kg^-1of cadmium on 50 th day.Meanwhile,the proportion of of earthworm in vertical profiler was significantly and negatively correlated with SOD activity,but positively with MDA content.The changes in vertical distribution of earthworms further altered soil physical and chemical properties,such as led to increases in the contents of soil organic matter,alkali-hydrolyzed nitrogen and available phosphorus.By the end of the experiment,the contents of soil organic matter,alkali-hydrolyzed nitrogen and available phosphorus increased by 29.24%,15.50%and 17.37%respectively under high level of cadmium pollution(30 mg·kg^-1)compared with the control group.The contents of soil organic matter,alkali-hydrolyzed nitrogen and available phosphorus were positively correlated with the distribution of earthworms.Finally,the changes in soil nutrient content affected the growth of maize.The correlation analysis showed that maize biomass and height were positively correlated with the content of soil alkali-hydrolyzed nitrogen,organic matter and available phosphorus,respectively.The results showed that by affecting earthworm behavior,cadmiumcan further affected soil nutrient status and plant growth,which provided new evidence for the ecological consequences of cadmium pollution.