Effects of soil microenvironmental changes on photosynthesis in the wild notopterygium forbesii rhizosphere in the Qinghai-Tibet Plateau
In order to further study the response characteristics of wild notopterygium forbesii to the soil environment,and clarify the difference of soil environments in different growth years,the soil enzyme activity and organic carbon content of the rhizosphere soil were monitored for wild notopterygium forbesii for three treatments with different continuous growth years(2,3 and 5 years).With the increase of growth years,the influence on soil porosity was mainly in the depth of 0-40 cm,the average soil porosity of 5-year old plots was decreased to 88.56％of the control,and the influence on the soil porosity at 50-100 cm soil layer was small.The soil moisture content in the 0-50 cm soil layer changed significantly,that in the root circumference was increased year by year in the first 3 years,reaching 105.59％of the control,and the soil moisture content in the soil below 60 cm soil layer had the same change law and the difference was not significant.Soil organic carbon content was decreased gradually,from the control to the five-year-old plots,the total soil organic carbon(TOC)content was reduced to 41.75％of the original,and dissolved organic carbon(DOC)content was decreased to 51.78％,particulate organic carbon(POC)content was decreased to 18.30％,active organic carbon(LFOC)content was decreased to 24.42％,easily oxidized organic carbon(ROC)content was decreased to 21.76％,and microbial biomass carbon(MBC)content was decreased to 47.31％of the original.There was no significant difference in DOC content between 3-year and 5-year old soils,and no significant difference in LFOC and ROC contents between 2-year and 3-year old soils.The activities of urease,polyphenol oxidase and catalase in soil were first decreased and then increased,and the activities of dehydrogenase and sucrase in soil had no obvious change trend,and the activity of phosphoric acid in soil was increased significantly.With the age of plants,the Leaf apparent quantum efficiency(AQP)was significantly was decreased,and the light compensation point(LCP),light saturation point(LSP)and dark respiration rate(Rd)were all significantly increased.The primary light energy conversion efficiency(Fv/Fm),photochemical quenching coefficient(qP)and photosynthetic electron transfer efficiency(φ PSII)of leaves were all decreased to varying degrees,and the non-photochemical quenching(NPQ)coefficient was increased significantly.These results suggest that soil physical and chemical activity and some soil enzyme and organic carbon content were decreased with the increase of growth years,the influence of soil microenvironment on root biological activity was increased,and the change of root living environment affected the absorption of soil water and nutrients by plants,and the plant leaf assimilation efficiency was reduced,further affected the quality and quality formation of live medicinal materials of notopterygium root.
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