| Cunninghamia lanceolata is the main economic timber species in southern China.It has the characteristics of fast growth,good material quality,wide use and good commercial value.In order to meet the wood demand,China has built a large area of pure Chinese fir forest.However,pure forest afforestation mode of Chinese fir often causes many ecological problems such as soil degradation,pests and diseases.Increasing the diversity of tree species in pure forests can help to realize multiple land use and effectively promote nutrient cycling and soil fertility.Therefore,the afforestation mode of under-forest interplanting has formed one of the Main Afforestation Modes of Chinese fir.Phoebe bournei has the characteristics of shade and humidity resistance,and it can still survive and grow under low level light conditions and improve soil environment.So Phoebe bournei is suitable for being an under-forest interplanting tree species.Therefore,this study chooses under-forest interplanting of Chinese fir to compare with pure Chinese fir forest.In this paper,the physical and chemical properties,enzymatic activities and microbial community characteristics of soils of pure Chinese fir forest and Interplanted Phoebe under Chinese fir forest in Nanping city of Fujian Province were studied by combining field investigation and indoor analysis.The influence mechanism of Interplanted Phoebe under Chinese fir forest on soil fertility was revealed,which provided scientific basis for maintaining and improving soil fertility of Chinese fir plantation and sustainable management of Chinese fir plantation.The main research results are as follows:(1)Interplanting Phoebe under Chinese fir forest can improve physical properties of soil.Compared with pure Chinese fir forest,soil bulk density of 0～20cm,20～40cm and 40～60cm soil layers decreased by 4.8%,0.3% and 1.4% respectively.Total porosity of 0～20cm,20～40cm and 40～60cm soil layers increased by 2.8%,1.2% and9.1% respectively.Non-capillary porosity in 0～20cm,20～40cm and 40～60cm soil layers increased by 5.4%,24% and 79.2%.The maximum water holding capacity of0～20cm,20～40cm and 40～60cm soil layers increased by 15.3%,1.3% and 10.6%respectively.The capillary water content in 0～20cm soil layer increased by 14.3%.(2)Interplanting Phoebe under the Chinese fir forest improved some soil nutrient conditions and had a significant impact on the nutrients in the 0～20cm soil layer.Compared with pure Chinese fir forests,the total nitrogen content in the 0～20cm,20～40cm,and 40～60cm soil layers increased by 6.9%,9.2%,and 8.7%,respectively;The ammonia nitrogen content in the 0～20cm and 20～40cm soil layers increased by29% and 40.7%,respectively,with significant differences in each layer;The nitrate nitrogen content in the 0～20cm soil layer increased by 10.7%;The total phosphorus content in the 0～20cm,20～40cm,and 40～60cm soil layers increased,and there was a significant difference in the total phosphorus content between the 20～40cm and40～60cm soil layers;The content of total potassium in the 0～20cm soil layer has increased by 7.5%;The changes in soil acidity,alkalinity,and available phosphorus content in each layer were not significant.(3)Interplanting Phoebe under Chinese fir forest increased soil organic carbon content.Compared with pure Chinese fir forest,the content of soil organic carbon in0～20cm,20～40cm and 40～60cm soil layers increased by 1.1%,10.1% and 30.1%respectively,indicating that interplanting treatment can promote the storage of soil organic carbon content to a certain extent and has a greater impact on 40～60cm soil layer.(4)Interplanting Phoebe under Chinese fir forest improved soil enzyme activity.Compared with pure Chinese fir forest,acid phosphatase activity in soil layers of0～20cm,20～40cm and 40～60cm increased by 4.1%,0.7% and 0.6% respectively.The activities of sucrase in 0～20cm,20～40cm and 40～60cm soil layers increased by25.5%,9.3% and 3.2% respectively.The increase of urease activity in 0～20cm soil layer was 8.4%.The activities of catalase in 0～20cm,20～40cm and 40～60cm soil layers increased by 1.9%,0.5% and 0.5% respectively.The correlation analysis showed that all four enzymes had significant or very significant positive correlation with total nitrogen,ammonia nitrogen,nitrate nitrogen,available potassium and available phosphorus.(5)After interplanting Phoebe under the Chinese fir forest,compared with the pure forest,interplanting increased the Shannon and Simpson diversity indices of bacterial communities in each soil layer;Through the ACE value and Chao1 value,it can be seen that the bacterial community in the 0～20cm and 40～60cm soil layers has increased the total number of OTUs after interplanting;The relative abundance of Acidobacteria in each soil layer increased,and the relative abundance of Chloroflexi in 0～20cm and 20～40cm soil layers increased;Through principal component analysis(PCo A),it was found that interplanting mainly affected the distribution of soil samples in the 0～20cm and 20～40cm soil layers,becoming more concentrated,making the bacterial community structure in each layer more stable;Through redundancy analysis(RDA),it can be seen that available potassium and total nitrogen have the highest impact on soil bacterial communities,while total phosphorus and potassium have the lowest impact on soil bacterial communities.(6)After interplanting Phoebe under Chinese fir forest,the diversity index of fungus communities Shannon and Simpson in soil layers of 0～20cm and 20～40cm were increased compared with pure forest,but had little influence on the diversity of fungus communities in soil layers of 40～60cm.It can be seen from ACE value and Chao1 value that fungus community with total OTU in soil layer of 0～20cm and20～40cm increased after interplanting.Relative abundances of Ascomycota,Rozellomycota and Mucoromycotawere were increased in each layer of soil,and interplanting had no significant effect on other flora.Principal Component Analysis(PCo A)showed that the fungus community structure changed due to interplanting,and the main changes were concentrated in 0～20cm and 20～40cm of soil.Redundancy analysis(RDA)showed that available potassium and total nitrogen had the highest impact on soil fungus community,while total phosphorus and total potassium had the lowest impact on soil fungus community,which was consistent with the results of bacterial redundancy analysis. |
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