Study On The Hormesis Effect And Mechanism Of Cd On Alkaline Phosphatase Under Different Land Use

Hormetic effect is a phenomenon which is the stimulatory effect of organism to low-dose contamination,and the suppression response of organism to high-dose contamination.Hormesis is considered to be an important measure of soil elasticity under stress conditions.With the acceleration of global change and human activity,soil heavy metal pollution is becoming more and more serious.At present,the research on heavy metal,especially Cd-related Hormesis effect is increasing day by day.Soil enzyme is one of the most ideal test endpoints for the study of Hormesis effect under heavy metals.Although important progress has been made in the study of the Hormesis effect of Cd and different soil enzymes,the research on the influence of land use changes on the two is not sufficient.We choose the Yili river valley as its clean soil environmental background.We collect the soil of grassland,wild forest,wheat and plantation totally 4 kinds of different land use.We study the response characteristics of soil alkaline phosphatase?ALP?,analytic Cd-ALP Hormesis effects features by adding different doses of Cd?CdCl₂·2.5 H₂O?.Choose typical Hormesis effects of dose,with the aid of Miseq second generation high-throughput sequencing technologies to research the change of soil microbial community structure and diversity.We explore the Cd-ALP Hormesis effects of microbial response mechanism,so as to land use change on soil elastic impact assessment under heavy metal stress.The main findings and conclusions were as following:?1?There are obvious Hormesis effect dose relationship between soil ALP and Cd under different land use types in Yili Valley.The maximal stimulus amplitude(y_max)of the Hormesis effect was 10.7-15.1%,and the corresponding dose interval?Q_i?was 10-25 and the soil elasticity?R?was 151-267.In comparison,the y_max of wheat and plantation soil is 5.1-11.3%,Q_i is 1-3,and R is 6-38.This indicates that the natural cover of Yili Valley is changed to human land,and ALP is more sensitive to the response of Cd stress,and soil response to Cd stress is less elastic.?2?The artificial use of natural cover in the ili river valley increased the soil pH,and TN and TC significantly decreased?P<0.05?,and the soil mass index decreased.The dominant communities in the four types of land use were Acidobacteria,Actinobacteria,Proteobacteria and the community relative abundance was over 72%.The relative abundance of Acidobacteria and Gp7 community was significantly increased and the relative abundance of G^-was significantly decreased?P<0.05?.The Hormesis effect parameter Q_i of soil ALP,R and soil TN,Firmicutes andVerrucomicrobia were significantly positively correlated.This indicates that soil TN and related microorganisms in different land use in Yili Valley may be closely related to the potential of soil to deal with Cd stress.?3?The microbial communities were Firmicutes,Actinobacteria,Proteobacteria and Acidobacteria communities,and their relative abundance accounted for more than 87 percent of the total.This shows that Cd addition did not significantly change the composition of soil microbial communities under different land use.?4?MiSeq high-throughput sequencing results showed that the soil microbial community with Hormesis response under the cover of grassland was mainly Actinobacteria,Acidobacteria and Verrucomicrobia,and the community abundance was over 40%.In comparison,the microbial communities that responded to wheat and plantations were Firmicutes,Verrucomicrobia and Acidobacteria communities,each of which accounted for 20%and 30%of the total population.?5?The G^-/G⁺change of soil microbial communities under four land uses in Yili River Valley was 4.5-5.9?G^-and G⁺ranged from 59.4-63.8%?.At different doses of Cd stress,the soil microbial community G^-/G⁺decreased to 0.7-1.0 under natural cover,such as grassland and wild fruit forest.After the artificial land use change?wheat,plantation?,the soil microbial community G^-/G⁺decreased to 2.0-3.3.It can be seen that the G⁺induced by Cd₂⁺stress increased significantly,and the increase of G⁺under natural cover was significantly higher than that of man-made land use.This shows that the increase of G⁺may be an important coping strategy for soil microbes under the stress of Cd₂⁺.