Effects Of Cadmium Pollution On Earthworm Behavior And Microbial Community Structure On Decomposition Of Poplar Litter

As we all lknow,soil heavy metal pollution has become an important environmental pollurtion incident that restricts economic growth in China and the world and harms food security and human health.A lot of research has been carried out at home and abroad in order to understand its harmful mechanism.However,most of these studies focus on the toxicity test or bioaccumulation effect of soil heavy metal pollution.There are few studies on the decomposition of litter,and the mechanism is still unclear.To this end,this study describes the effects of heavy metals(0,15,30,45 mg/kg)on litter decomposition from the perspectives of soil macrofauna behavior and soil microbes,in order to correctly understand the ecology of soil heavy metal pollution.The consequences provide evidence.The results show:(1)Acute toxicity test showed that Cd2+ had a lethal effect on coclkroaches,the semi-lethal concentration of cockroach(24h-LCso)was 207.71 mg/L,and the sublethal concentration(24h-LC1o)was 107.58 mg/L,48h-LC5o.It was 181.32 mg/L,and 48h-LCioOwas 64.97 mg/L.Cd2+ has a strong toxic effect on sputum,and the toxicity is deepened with the prolongation of exposure time.(2)The behavior of cock:roaches and physiological tests showed that Cd2+ had a significant effect on the sputum movement pattern.From the earthworm cave structure,the maximum depth and total length of earthworm caves decreased significantly with the increase of Cd2+ concentration.They dropped by 65.27%and 49.36%respectively.Moreover,the response of sputum physiology to Cd2+ pollution was also significant.NADH increased with the increase of Cd2+ concentration after 14 days of exposure,while SOD showed a tendency of low concentration to promote high concentration inhibition.These unfavorable responses eventually led to strontium biomass(fresh Heavy)keep falling under this condition.(3)The litter decomposition test,which explored the effects of heavy metal concentration and radon density(lower 10 and 20/barrel)on soil physical and chemical properties,soil microbial community structure and litter decomposition.The results showed that at the end of the expernment,the weight of litter in the low-thickness and high-density treatments was 41.75%and 50.88%,respectively.In the treatment of heavy metals,litter decomposition was observed with the increase of treatment concentration.The speed decreased continuously.Compared with the control,the litter weight loss decreased by 36.59%and 49.38%in the low-density and high-density treatments,respectively.Moreover,the content of lignin in litter increased with the increase of Cd2+ concentration.Under the action of low density and high density,the highest concentration treatment was 34.27%and 51.65%higher than that of the control group.In addition,the density of strontium also has a significant effect on the decomposition process of falling objects.As the density of strontium increases,the decomposition rate of falling objects increases,and the lignin content gradually decreases.In the presence of earthworms,the concentration of fungi in the soil increased by 47.42%compared with blank treatment,and decreased significantly by 31.70%under cadmium pollution.The change of fungal diversity index was consistent with the change of litter decomposition rate.(4)Changes in the behavior of the cockroaches and changes in the rate of decomposition of the litter further led to changes in the physical and chemical properties of the soil.For soil bulk density and soil porosity,the soil bulk density was the largest in the control,while in the treatment with heavy metal concentrations,the soil bulk density was relatively low.On the contrary,soil porosity is lower in the treatment with heavy metal concentration than in the control and reaches a significant level at the highest concentration.For soil chemistry,since the leaves and mites are mainly distributed in the surface layer,the physical and chemical properties of the soil are also changed by the surface layer.Basically,with the increase of the concentration of heavy metals,the total nitrogen,alkali nitrogen,total phosphorus,The content of available phosphorus and organic matter is decreasing,while the content of ammonia nitrogen is opposite,which increases with the increase of heavy metal concentration.Based on the above results,we found that soil heavy metal pollution has a significant impact on the decomposition process of poplars.As the concentration of heavy metals increases,the decomposition rate of the falling objects gradually decreases.Through the acute toxicity test and behavioral test,we found that the change of the decomposition process may be related to the physiological and behavioral changes of the earthworms.That is,as the concentration of heavy metals increases,the toxic effects of the earthworms occur,and the ability to adapt to hypoxia decreases.The exercise capacity decreases per unit time,and the speed at which the leaves of the poplars are fed is reduced.Moreover,inhibition of sputum behavior further leads to changes in soil porosity and soil bulk density.That is,as the concentration of heavy metals increases,soil porosity decreases due to inhibition of strontium behavior,pH decreases,and aeration conditions decrease.These changes inhibit the community diversity of fungi,which often plays a very important role in the decomposition of litter.It often plays a very important role in the decomposition of falling objects.It can be seen that the ecological benefits of heavy metal pollution in the decomposition of litter are very complicated,including the role of soil animals and the role of soil microorganisms.Therefore,in the past research,soil animals were studied se:parately or soil microorganisms were studied separately.The method to explain the study of the decomposition process of the falling object is not rigorous.