| Forest age is an indispensable factor affecting the structure and function of forest ecosystem.During phylogeny,the relationship between plant body and environment can be regulated by changing the community structure,species composition and forest niche,so as to promote the stability and health of forest ecosystem.To better understand the relationship of change and synergy between plant and soil microorganisms in the plantation ecosystem of different age groups,in this study,12 fixed plots of Phoebe bournei plantations with different ages(5 years,10 years,20 years,45 years)were established.We took two samples in December 2019 and July 2020.The leaf structure characters(leaf length,leaf width,specific leaf area,leaf thickness,leaf water content of 9 kinds of characters)and nutrient content,the carbon content of leaf,leaf nitrogen content and leaf phosphorus content of 6 kinds of nutrients),litter nutrient content(litter carbon content,nitrogen content,litter phosphorus content of 6 kinds of nutrients),soil physical and chemical properties,including density,pH value,organic carbon,total nitrogen was measured.The results showed that the variation characteristics of leaf functional traits,litter nutrient characteristics,soil fertility and microbial structure and diversity at different forest ages.In order to clarify the internal stability characteristics of nutrient contents in leaves and litter,the internal stability model was used.The results of(Redundancy analysis)RDA analysis explored the key factor of microbial community,revealed the Phoebe bournei leaf traits,soil physical and chemical properties,and synergistic effect between soil microbial community.The elucidation of these results will contribute to lay a foundation for further study on the feedback between plant and soil under natural conditions,and provide some theoretical basis for scientific and rational management of the whole growth process of forest.The main conclusions are as follows:(1)With the increase of forest age,leaf structural traits had better adaptability to environmental factors.The variation of leaf structure characters was abundant,and the variation trend of plasticity index with stand age was similar to the coefficient of variation.The plasticity index of leaf length,leaf width,leaf area,leaf perimeter and main vein diameter all reached the maximum at 20 years,leaf thickness reached the maximum at 10 years,specific leaf area and primary vein density reached the maximum at 45 years.The plasticity index of leaf structural traits showed that leaf morphological traits were greater than vein functional traits.(2)The contents and distribution of nutrient elements in leaves,litter and soil of Phoebe bournei were different.The order of nutrient contents in leaves of Folia chinense was C>N>K>Ca>P>Mg,the order of nutrient contents in litter was C>N>Ca>K>Mg>P,and the order of nutrient contents in 0-15 cm soil layer was SOC>K>N>Mg>Ca>P.The distribution of the same element was different among different components.The contents of SOC,N,and P were all in leaf>litter>soil,the contents of K were in leaf>soil>litter,the contents of Ca were in litter>leaf>soil,and the contents of Mg were in soil>leaf>litter.The results showed that leaf N,litter N and soil N increased with the increase of stand age.The soil SOC of 0-15 cm and leaf N increased with stand age.Compared with 5-year old Phoebe bournei,the N content of 10-year old,20-year old and 45-year old leaves increased by 13.06%,32.20%and 38.70%,respectively,and the N content of litter increased by 4.97%,12.23%and 23.90%,respectively.The content of leaf P and soil P fluctuated,which was the highest in 20-year old Phoebe bournei,and P content in litter increased with stand age,but there was no significant difference among different stand ages.With the increase of stand age,the K content of leaves in 45-year-old Phoebe bournei was significantly lower than that in the other three stand ages.The K content of litter was 20 years>5 years>45 years>10 years,and there was no significant difference among different stand ages.The soil total K content decreased first and then increased with the increase of stand age,and the TK content in each soil layer of 5-year old Phoebe bournei soil was the highest.Leaf Ca,litter Ca and soil available Ca,leaf Mg content,litter Mg and soil available Mg showed a similar trend with the growth stage of Phoebe bournei,respectively.(3)Soil microbial diversity was different among different stand ages.With the increase of stand age,the Shannon-Winner diversity index and richness index of soil bacteria increased firstly and then decreased.Both of them reached the maximum value in 10-year-old Phoebe bournei,and the minimum value was in 45-year-old Phoebe bournei.The Shannon-Winner diversity index and richness index of soil fungi decreased first and then increased with the increase of forest age,and both reached the minimum value in the 10-year-old forest of Phoebe bournei,while the maximum value was in the 45-year-old forest of Phoebe bournei.Beta diversity of bacteria and fungi showed a strong aggregation effect in the same stand age stage,bacteria showed a strong separation effect in different stand ages,fungi had an aggregation effect in the young stage,and separated with the increase of stand age.Soil microorganisms of different stand ages have the same dominant population in phylum classification,but their relative abundance is different.Proteobacteria,Acidobacteriota,Chloroflexi and Actinobacteriota are the main phyla of bacteria.Ascomycota,Basidiomycota and Unclassified K-fungi were the three dominant fungi in the fungal community,which accounted for more than 90%of the fungal community.(4)The correlation between leaf structural traits and leaf nutrient content at different stand ages was stronger than that between soil nutrients,and the synergistic changes of soil nutrients K,Ca,Mg with leaf and litter contents were more intense than those of other nutrients.The internal stability of N,P,Ca in the leaves was P>Ca>N.The P content in the leaves had a higher homeostasis at different ages,while the N content in the leaves was weak.Nutrient K of dead leaves did not have internal stability.The internal stability of other nutrient elements in litter was Mg>Ca>C>N>P.The stability of medium elements in litters was better than that of a large number of elements.There was a significant correlation between leaf and soil nutrient characteristics and microbial abundance and diversity(Alpha and Beta diversity).The effect of leaf and soil nutrient characteristics on fungi diversity was greater than that on bacteria,and the effect of leaf litter and soil nutrients on microbial diversity was greater than that on leaves of Phoebe bournei.The effect of leaf-soil nutrients on the diversity of soil fungal community was greater than the abundance. |
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