Study On Diversity Of Nematodes In Rhizosphere Soil Of Dangshan Pear

In this thesis,the rhizosphere soil nematode of Dangshan pear was selected as the entry point,and the rhizosphere soil of Dangshan pear with different ages and different degrees of weakening was selected as the experimental material,and the differences in rhizosphere soil nematode species,diversity and community structure of Dangshan pear were studied by morphology and high-throughput sequencing techniques to clarify the effects of continuous crop of Dangshan pear on rhizosphere soil nematode species,community structure and soil nematode ecological index.1.the rhizosphere soil nematode channel index(NCR)of Dangshan pear became smaller with the increase of tree age,indicating that the initial stage of pear planting was mainly by bacterial decomposition as the main way.With the increase of tree age the proportion of fungal decomposition gradually increased,and the proportion of fungus-feeding nematodes also gradually increased,which corresponds to the proportion of fungus-feeding nematode number in soil nematodes.2.Among the four samples,60-year-old trees(P60)had the largest structure index and were in quadrant C,while 30-year-old(P30)and 150-year-old(P150)trees were in quadrant D.This indicates that the structure of the soil food web gradually stabilized as the age of the trees increased,the length of the food web and the nutrient input from outside gradually increased,but it tended to weaken at a later stage.3.According to the diversity index Shannon and the diversity index Simpson,the diversity of different tree ages and necrotic rhizosphere soils were compared as follows:P60>P30>P150,P150d>P150 in the rhizosphere soil.The above results are consistent with the results of soil nematode zone analysis index in the morphological identification,indicating that the abundance,uniformity of distribution and species diversity of soil nematode community changed with the increase of tree age,thus affecting the stability of soil food web.The results of soil physicochemical property measurements showed that total nitrogen,p H value,exchangeable magnesium and effective sulfur tended to increase and then decrease with the increase of planting years,indicating that these four physicochemical properties might be affected by the changes of soil nematode community.4,According to Beta diversity analysis,it was concluded that the difference of community composition between P60 and P150 was not much compared with P60 and P30,and the two were relatively similar.P30 and P150 in the middle was the biggest distance between P60 and P150 and P60 and P30,and the difference of community composition between the two was bigger.P150 d and P150 healthy pear trees Community composition difference is larger.