The Tending And Thinning Impact Microorganism Community And Physicochemical Properties In Soil Of Cunninghamia Lanceolata Plantation

Cunninghamia lanceolata is the most widely cultivated tree in southern China.It has many problems,such as high density,single tree species and continuous planting,which lead to difficulties in cultivating large-diameter wood,decline of soil fertility,poor ecological benefits,frequent occurrence of fires,diseases and insect pests,and urgent need to improve quality and efficiency.Tending thinning is an effective measure to cultivate and improve the quality of large diameter timber in Chinese fir plantation,which can be used to replace broad-leaved local precious species with gap after thinning to improve the stand structure and form mixed coniferous and broad-leaved mixed forest of different ages,so as to improve the ecological,economic and social benefits of the forest.Relying on the project of "Accurate Improvement of Forest Quality" subsidized by the central government,this study took 9-year-old Chinese fir artificial pure forest of state-owned forest farm in Ta City of Yueyang City as the research object,and set up 4 treatments(CK:unthinning,T1:thinning intensity 20%,T2:thinning intensity 30%,T3:thinning intensity 40%),regular observation cunninghamia lanceolata forest soil microbial,physical and chemical properties,soil enzyme activity,trees grow,undergrowth indicators such as plant community characteristics,through the comparative analysis of the differences between the groups,to explore the theory of plant-soil-the influence of the relationship between microbial interactions,find both can improve the forest ecological benefits and conducive to cultivating-big diameter wood tending thinning.intensity.It provides theoretical basis and technical support for improving quality and efficiency of Chinese fir plantation.The main results are as follows:(1)Tending and thinning increased the abundance and abundance of bacteria in soil of Cunningham lanceolata,and promoted T3>T2>T1>CK,rhizosphere soil>non-rhizosphere soil.After tending thinning,at the phylum level,tending thinning increased the abundance and abundance of Actinobacteria and Proteobacteria,which promoted T3>T2>T1>CK,but decreased the abundance and abundance of Chlorobacteria and Acidobacteria,to the extent of T3>T2>T1>CK.(2)Tending thinning can reduce soil bulk density,increase soil capillary porosity and non-capillary porosity,enhance soil water storage capacity,and thus improve soil physical properties.Its improvement effect is T3>T2>T1>CK,and the improvement effect on the top soil layer(0-20cm)is greater than that on the core soil layer(20-40cm).Compared with CK,the annual change of soil bulk density in 0-20cm soil layer of T1,T2 and T3 decreased by 0.015 g·cm-3,0.027 g·cm-3and 0.028 g·cm-3,respectively,and the capillary porosity increased by 0.26%,0.91%and 0.92%,respectively.Soil non-capillary porosity increased by 0.08%,0.58%and 0.59%,respectively,and soil water storage capacity increased by 3.50%,11.16%and 12.01%,respectively.(3)Tending thinning can increase soil pH value,increase effect T3>T2>T1>CK,tending thinning can promote soil TN,TP,TK content increase,promote effect T3>T2>T1>CK,tending thinning can improve soil enzyme activity.Urease,sucrase,catalase,acid phosphatase enhancement T3>T2>T1>CK,cellulase enhancement T2>T3>T1>CK,top layer>core layer.Compared with CK,pH value in 0-20cm soil layer of T1,T2 and T3 increased by 0.11,0.24 and 0.27,respectively,and TN content increased by 0.024 g·kg-1,0.075 g·kg-1 and 0.088 g·kg-1,respectively.TP content increased by 0.003 g.kg-1,0.004 g.kg-1,0.007 g.kg-1,and TK content increased by 0.05g·kg-1,0.20g·kg-1,0.22g·kg-1,respectively.Urease activity increased by 0.61 mg/g/h,1.13 mg/g/h,1.88 mg/g/h,and sucrase activity increased by 0.98 mg/g/h,1.81 mg/g/h,1.89 mg/g/h,respectively.Catalase increased by 5.54 mg/g/d,9.71 mg/g/d,12.52mg/g/d,acid phosphatase activity increased by 3.86 mol/g/d,6.55 mol/g/d,7.19mol/g/d,respectively.The cellulase activity was increased by 0.67 mg/g/h,1.09 mg/g/h and 1.01mg/g/h,respectively.(4)Thinning promoted the increase of height,DBH and per tree volume of Chinese fir.T3>T2>T1>CK,DBH>per tree volume>tree height.After thinning,the annual increase of per unit area volume first decreased and then increased,and after 3 years,T3>T2>T1>CK.The promoting effect of thinning on the growth of Chinese fir decreased with time,After 6 years of thinning,there were no significant differences in the annual growth of height,DBH,volume per plant and volume per unit area among different treatments.Therefore,the interval period of thinning should be 5-6 years.(5)Tending and thinning promoted the growth of understory vegetation in Chinese fir forest.After 6 years of thinning,the understory shrub species T1,T2 and T3 increased by 3,7 and 10 species,respectively,compared with CK.The Shannon-Wiener diversity index,Simpson ecological dominance index and Pielou evenness index of undergrowth vegetation after thining were T3>T2>T1>CK.(6)The correlation between soil microorganisms,soil physical and chemical properties and vegetation was as follows:the total OTU of soil microorganisms was negatively correlated with bulk density and pH value(P<0.05),and positively correlated with capillary porosity,non-capillary porosity,water storage capacity,TN,TP,TK and enzyme activity(P>0.05).The total number of soil microbial OTU was significantly positively correlated with tree height,DBH,volume per plant and annual increase of stock(P<0.05),and was extremely significantly positively correlated with Simpson index,Pielou index and Shannon-Wiener index of undergrowth(P<0.01).Soil bulk density was significantly negatively correlated with the annual growth of tree height(P<0.05),and extremely significantly negatively correlated with DBH,volume per plant,annual growth of stock volume,Simpson index,Pielou index and Shannon-Wiener index of understory vegetation(P<0.01).Soil porosity and water storage capacity were significantly positively correlated with tree height,DBH,volume per tree and annual growth of stock(P<0.05),and extremely significantly positively correlated with Simpson index,Pielou index and Shannon-Wiener index of undergrowth(P<0.01).The activities of TN,TP,TK,urease,sucrase,catalase,acid phosphatase and cellulase were positively correlated with tree height,DBH,volume per plant,annual increase of stock volume,Simpson index,Pielou index and Shannon-Wiener index of undergrowth vegetation(P>0.05).Tests show that nine years of Chinese fir plantation intensity thinning measures should be taken,which would hold the number about 1508 plants/hm2,can promote the growth of trees,undergrowth,increase soil microbial populations,improve soil physical and chemical properties,the structure and function of the whole Chinese fir plantation ecosystem more robust,is conducive to sustainable management.