| One of the main tasks for ecosystem control of Chinese fir plantation is management of understory vegetation.The good and bad management of the undergrowth vegetation of Chinese fir plantation not only affects the stability of the ecosystem of Cunninghamia lanceolata plantation,but also affects the growth of Cunninghamia lanceolata plantation and the maintenance of the long-term productivity of forest land.So far,China's southern Cunninghamia lanceolata plantation cultivation is still mainly medium diameter timber.With the improvement of people's living standard,the Cunninghamia lanceolata large-diameter timber market is in short supply.How to cultivate Cunninghamia lanceolata large-diameter timber scientifically and realize the sustainable management of Cunninghamia lanceolata forest land has become a technical problem that Cunninghamia lanceolata scientists urgently need to solve.This paper by the mouth of state-owned forest farm of fujian province 35 years large-diameter timber stand of Cunninghamia lanceolata is divided into the research object,through field investigation and laboratory analysis,analysis of undergrowth retention,undergrowth to remove + forests interplanting Phoebe bournei,undergrowth(control)three fir large-diameter timber undergrowth management mode,the structure of the material for the growth of Cunninghamia lanceolata of large-diameter timber plantation and soil physical properties,soil enzyme activity and soil microbial diversity,and to analyze the relationship between different indicators,the results of the study not only can correct evaluation of Cunninghamia lanceolata plantations undergrowth management influence on Cunninghamia lanceolata plantation ecosystem structure,It can also provide theoretical reference for the cultivation of large-diameter timber of Cunninghamia lanceolata plantation and the sustainable management of Cunninghamia lanceolata plantation.The main research results are as follows:(1)By analyzing the contrast different undergrowth management mode of Cunninghamia lanceolata average increment of large-diametertimber plantation forest,Cunninghamia lanceolata diameter class distribution,the diameter of Cunninghamia lanceolata,discrete and Cunninghamia lanceolata planted structure,the results show that the fir large-diameter timber undergrowth keep a reasonable management pattern space,the quantity of material fir large-diameter timber is higher,undergrowth reserve management is advantageous to the forest growth;The management model of subforest vegetation removal had certain inhibitory effect on the growth of Cunninghamia lanceolata,which enhanced the stand competition of Cunninghamia lanceolata large-diameter timber plantation and resulted in a lower yield rate of Cunninghamia lanceolata large-diameter timber.The management mode of interplanting Phoebe bournei under the forest is beneficial to the spatial stability of the stand and the recovery of the growth of Cunninghamia lanceolata.(2)By studying the soil physical properties of Cunninghamia lanceolata large-diameter artificial forest under different forest vegetation management modes,the results showed that: forest vegetation removal management increased soil bulk density,reduced soil porosity and mass water content,and had a relatively adverse effect on soil physical properties;Interplanting Phoebe bournei management under forest reduced soil bulk density,increased soil porosity and effectively improved soil physical properties.(3)By studying the soil chemical properties of Cunninghamia lanceolata large-diameter plantation under different forest vegetation management modes,the results showed that: the removal of forest vegetation reduced the content of soil organic matter and total nitrogen;The contents of total potassium and available potassium in soil were significantly reduced(p <0.05).The removal of subforest vegetation and interplanting of Phoebe bournei significantly increased the content of total nitrogen,hydrolyzed nitrogen and available phosphorus in soil(p<0.05),and to some extent,the content of organic matter and total phosphorus in soil.(4)By studying the soil enzyme activities of Cunninghamia lanceolata large-diameter plantation under different forest vegetationmanagement modes,the results showed that the activities of soil catalase and polyphenol oxidase in the management mode of forest vegetation reservation were significantly higher than those in the management mode of forest vegetation removal(p <0.05).The removal of subforest vegetation significantly increased soil urease activity(p <0.05).The management mode of subforest vegetation removal and interplanting with Phoebe bournei significantly promoted the activities of sucrase,acid phosphatase and polyphenol oxidase in the surface soil,and the soil enzyme activities were generally higher in this management mode.(5)Through high-throughput sequencing of fir large-diameter timber plantation community structure of soil bacteria,bacterial diversity characteristics show that different undergrowth management mode,all tags were identified 38 kinds of soil bacteria and 78 classes,the main advantage of a soil bacteria for door: Actinobacteria,Acidobacteria and Chloroflexi,different undergrowth management mode have significant difference between species.The removal of understory vegetation resulted in the decrease of bacterial species(OTUs)and affected the diversity and richness of soil bacteria.Interplanting Phoebe bournei under forest increased the diversity of soil bacterial species,and the management of underforest vegetation had a certain impact on the composition of soil bacterial community.(6)The correlation analysis of soil bacterial diversity index with soil physical and chemical properties and soil enzyme activity showed that the contents of total nitrogen,total phosphorus,total potassium,hydrolyzed nitrogen and available potassium in soil were positively correlated with soil diversity index,but not with soil physical properties.Soil sucrase and polyphenol oxidase showed significant positive correlation with soil diversity index,and soil catalase showed extremely significant positive correlation with soil diversity index.The correlation analysis between soil bacterial community structure and soil physical and chemical properties showed that: soil total nitrogen content,total phosphorus content,hydrolyzed nitrogen content,available phosphorus content,total porosity,capillary porosity and mass water content were significantly correlated with soil bacterial community composition.Further analysis by CCAcanonical correspondence analysis showed that the important environmental factors causing heterogeneity of bacterial community structure were soil total nitrogen content,total phosphorus content,hydrolyzed nitrogen content,available phosphorus content and mass water content.The results showed that the community structure heterogeneity of soil bacteria driven by soil environmental factors was changed by understory vegetation management.(7)Through high-throughput sequencing fir large-diameter timber plantation soil fungi community structure,diversity shows that different undergrowth management mode,all tags were identified 10 soil fungi categories and 23 classes,the main advantage of a fir large-diameter timber plantation soil fungi for door: Ascomycota,Basidiomycota and Mortierellomycota,undergrowth management mode have significant differences in different species.The removal of understory vegetation inhibited the species richness and diversity of soil fungi to some extent.The understory vegetation management model had some effect on soil fungal community composition,but the overall community structure remained stable.(8)The correlation analysis of soil fungal diversity index with soil physical and chemical properties and soil enzyme activity showed that:soil total nitrogen content,total phosphorus content,hydrolyzed nitrogen content and available potassium content were positively correlated with soil diversity index,but not with soil physical properties.Soil sucrase and polyphenol oxidase showed significant positive correlation with soil diversity index,and soil catalase showed extremely significant positive correlation with soil diversity index.The correlation analysis between dominant phylum of soil fungi community and soil physical and chemical properties showed that soil bulk density,non-capillary porosity,mass water content and available phosphorus content were significantly correlated with soil fungal community composition.Further analysis by CCA canonical correspondence analysis showed that abiotic environmental factors together explained 78.1% heterogeneity of soil fungal biomass,and the main environmental factors causing changes in fungal community structure were soil bulk density,mass water content,non-capillary porosity and available phosphorus content.To sum up,understory vegetation management drives community structure heterogeneity of soil fungi by changing soil abiotic environmental factors.Based on the above research results,it was found that the undergrowth vegetation management model had different effects on the stand and timber species structure,soil physical and chemical properties,enzyme activities,soil microbial species diversity and community structure of Cunninghamia lanceolata large-diameter plantation.The retention of understory vegetation contributes to the stability of stand structure and the increase of timber yield.The removal of understory vegetation reduced the productivity,stand structure and soil structure stability of Cunninghamia lanceolata large-diameter plantation,inhibited the nutrient content and enzyme activity of some soil,and reduced the richness of microbial species,which was not conducive to the sustainable development of Cunninghamia lanceolata large-diameter plantation ecosystem science.Interplanting Phoebe bournei under the forest can optimize the stand structure and increase the growth of large-diameter timber of Cunninghamia lanceolata,which is beneficial to the recovery and improvement of soil physical properties and soil fertility,increase soil enzyme activity and microbial diversity,and play a certain positive role in the restoration of Cunninghamia lanceolata large-diameter timber plantation ecosystem.The two management modes of understory vegetation conservation and interplanting Phoebe bournei are suitable for the development of Cunninghamia lanceolata large-diameter plantation.The results of this experiment provide a theoretical basis for the selection of understory vegetation management mode in the management and cultivation process of Cunninghamia lanceolata large-diameter plantation to some extent. |
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