Responses Of Soil Microbes And Enzyme Of Compound Community To Elevated Atmospheric CO₂ Concentration And Temperature

Soil microorganisms is an important component of the ecosystem of the soil in its participation in the complexity of the decomposition of organic matter and re-synthesis;it's also involved in the cycle of C,N,S,P and so on.Soil enzymes is the protein with biological activity in soil;it promotes the biochemical processes of soil together with the micro-organisms and plays an important role in the nutrients transformation of trees In view of the sensitivity of soil microorganisms and soil enzyme to environmental change,their reaction when CO₂ concentration and temperature elevated will impact the structure and function of forest ecosystem in large measure.Therefore,in order to fully evaluate the impact of atmospheric CO₂ concentration enrichment and elevated temperature on the whole ecosystem,it is necessary to carry through under-depth study and discussion to soil microorganisms under CO₂ concentration enrichment and elevated temperature.Effects of elevated atmospheric CO₂ concentration(350±25μmol·mol^-1), increased temperature(2.0±0.5℃) and both of the two on the number of rhizospheric microbe and rhizospheric enzyme activity were studied by the independent and enclosed-top chamber' system under high-frigid conditions in the paper.The results are as the following,1) Treatment ECT,EC and ET can increase the plant chlorophyll content of the complex community.Chlorophyll content of the herbs' leaves with different treatments has significant differences.Enrichment atmospheric CO₂ concentration and elevated temperature effectively promote the content of chlorophyll a,chlorophyll b and total chlorophyll,especially the promotion of the chlorophyll b synthesis.Leaf Chla/b value descended with the enrichment atmospheric CO₂ concentration and elevated temperature.2) Plant growth and production increase with the enrichment atmospheric CO₂ concentration and elevated temperature.Enrichment atmospheric CO₂ concentration and elevated temperature can promote the plant height,stem diameter and increase in the number of leaves and can reduce the number of yellow leaves. 3) In comparison with the control,treatment EC,ET,and ECT can increase the number of rhizosphere micro-organisms,but the response of different types of micro-organisms on the EC,ET and ECT are different.Statistical analysis showed that the response of treatment EC and ET on the number of rhizosphere bacteria are significant(P＜0.05),and the response of ECT on the rhizosphere bacteria was not significant.The effect of Enrichment atmospheric CO₂ concentration and elevated temperature to rhizosphere actinomycetes and fungi are not remarkable.4) The response of different types of rhizosphere soil enzymes to EC,ET and ECT are different.Comparing to CK(20.98±0.1722EU),treatment EC improved rhizosphere catalase activity(29.06±0.2024EU) significantly(P＜0.05);However, treatment ET decreased rhizosphere catalase activity in comparison with the control. which shows that ET reduced rhizosphere catalase activity.Treatment ECT improved rhizosphere catalase activity(21.83±0.2587EU),but the difference was not significant(P＞0.05).EC increased the polyphenol oxidase activity by 19%,and the differences between the two was significant(P＜0.01).Treatment ET improved the polyphenol oxidase activity significantly(P＜0.01);it is 1.66 times of CK (1.4802±0.1115EU).Rhizosphere polyphenol oxidase acticity with ECT treatment (1.8102±0.1025EU) didn't have significant difference with CK(P＜0.05),therefore it can be considered that ECT doesn't have an impact on the rhizosphere polyphenol oxidase activity.Rhizosphere dehydrogenase activity with EC treatment had significant difference with CK(P＜0.01).Comparing with CK(5.57±0.115EU),ET and ECT treatments didn't have impacts to rhizosphere dehydrogenase activity.5)The effects of treatment EC,ET and ECT to different hydrolase were different. In comparion with the control(1.67),the activity of rhizospheric urease were increased significantly of EC(P＜0.05).However,the effect of ECT and ET on rhizospheric urease activity was not significant(P＞0.05).The rhizospheric invertase activity of treatment ECT(49.47) and EC(43.84) were significantly increased in comparison with the control(P＜0.05),but the ET cheatment(30.56) was lower than CK(35.54).6) In comparion with the control(except non-rhizospheric dehydrogenase), treatment EC,ET and ECT had no effect on the number of non-rhizospheric microbe and non-rhizospheric enzyme activity.Rhizospheric effect of the total number of microbe for all treatments was significant;but rhizospheric effect of dehydrogenase of ECT and ET was not significant.Rhizospheric effect of invertase of ET was not significant.The rest treatments of soil enzymes were significant.