Study On The Mechanism Of The Influence Of Cedru Deodara On Plant Diversity Under The Tree

Cedru deodara has now been planted widely as urban landscaping trees. Through field investigation, It founded that there were few plants under C. deodara tree, which seriously affected the urban landscape effect. Therefore, It has very impotant significance to explore the reason of lower plant diversity under C. deodara. In this study, through culture dish and pot experiment to study the effect of leaves and branches extract on physiological indexes of germination and growth of F. elata and soil biological activity.Using ELISA to study the concent of GA and ABA of seed germination and plant growth of F. elata treated by water extract of leaves.The main results showed that:1? The plant diversity under the C. deodara and reference samples were investigated. The results showed that, in the whole growing season, compared with the reference samples, all importance value, including cover degree, diversity index under C.deodara are lower. In October, the plant coverage is only 13.92% under C.deodara, but the plant coverage of reference samples is 33.84%.Shannon- Wiener index under C. deodara was lower 57.35%,40.27%,59.18% than reference samples in three reasons.2? The allelopathy of aqueous extract of the branches and leaves, litter, rhizosphere soil,root and volatiles of branches and leaves were studied.The results shows that different aqueous extract and volatiles of branches and leaves had obviouly inhibited R. sativusand L. sativa seed germination. And allelopathy of branches and leaves is strongest, germination rate of R. sativus seed was decreased by 94.49% at 0.1 g/m L,rhizosphere soil is the weakest.3? Using chromogenic method to identify the phenolic substancesof aqueous extract. The results showed that aqueous extract of the branches and leaves, litters and root contained phenolic substances. Through GC- MS to analysis the components of volatile of branches and leaves.The results showed that terpenes of l volatile were accounted for 52.81%. the major components were were ?-pinene(17.16%),b- using olefin(13.06%), ?-pinene(11.53%) and D- limonene(9.66%).4?The effect of leaves and branches extract on physiological indexes of germination and growth of F. elata were studied through culture dish and pot experiment. Before germination 48 h, the activity of SOD, CAT and concent of WSS, Pro were increased,so the concent of MDA maintained at low level. After germination 48 h, the activity of SOD, POD and concent of WSS were obviously decreased, so the concent of MDA was obviously increased. During the whole process of growth of F. elata, the activity of SOD, POD, CAT and concent of WSS, Pro were obviously increased.,but the concent of MDA maintained at high level. The results showed the physiological metabolism of germination and growth of F. elata was inhibited by leave extracts.5?The effect of aqueous extracts on soil biological activity was studied. The results showed that the aqueous extracts in different concentration had obviouly reduced the number of bacteria, fungi, actinomycetes and the total of microorganisms. The number was at least at 0.1g/m L.Microbial biomass C, N were obviouly decreased by 31.46% and 38.24% at 0.1g/m L,but soil respiration was obviously increased. The activities of protease, urease,polyphenol oxidase were decreased with the increasing aqueous extract concentration.However, the activity of phosphatase was obviously increased.The correlation analysis showed that there was a positive correlation between the number of soil bacteria, microorganisms, activity of soil protease, polyphenol oxidase and plant height and root length of F. elata. The results showed that the water extract of leaves and branches can obviouly reduce the number of soil microorganism, change microbial community structure, reduce the microbial biomass C, N and soil enzyme activity.This will reduce the soil available nutrient.6?Using ELISA to study the concent of GA and ABA of seed germination and plant growth of F. elata treated by water extract of leaves. The result showed that concent of GA in germination seed and plant were obviouly decreased with the increasing aqueous extract concentration.But the concent of ABA in germination seed and plant were obviouly increased with the increasing aqueous extract concentration. The result showed the production of GA in germination seed and plant was inhibited by aqueous extract of leaves,but the production of ABA was promoted.This will accelerate the senescence of F. elata plants.