Effects of different densities of Cunninghamia lanceolata-Phoebe bournei compound storied forests on soil physicochemical properties and microbial communities
To clarify the relationship of the dominant phyla and diversity of soil microbial communities with soil physicochemical properties after thinning and interplanting,four different thinning retention densities[375 plant·hm-2(D375),570 plant·hm-2(D570),630 plant·hm-2(D630),810 plant·hm-2(D810)]were studied.The effects of Cunninghamia lanceolata retention density on soil nutrients,soil aggregate size,and microbial community composition and diversity in 0-20 cm layer of C.lanceolata-Phoebe bournei compound storied forests were studied.The results showed that with the increase in the retention density of C.lanceolata,soil water content(SWC)first increased and then decreased;pH value,total nitrogen(TN),and total phosphorus(TP)contents had little change;total carbon(TC),soluble organic carbon(DOC),and available phosphorus(AP)content showed a decreasing trend.The content of TC,DOC,AP,available potassium(AK),nitrate nitrogen(NO3--N),and ammonium nitrogen(NH4+-N),carbon to nitrogen ratio(C/N),and nitrogen to phosphorus ratio(N/P)under D375 treatment were the highest.The content of soil mechanically stable aggregates showed D375>D810>D570>D630.The increase in the retention density of C.lanceolata improved the diversity of specific bacteria in the community.However,the excessive retention density of C.lanceolata reduced the number of specific bacterial operational taxonomic units(OTUs),and the number of soil-based fungi OTUs decreased with the increase in the retention density.The Simpson index and Shannon index of bacteria had little change on the whole,and there was no significant difference between different treatments.The Chao1 index of the D630 treatment was significantly higher than that of other treatments(P<0.05),while the Simpson index of fungi treated with D375 was significantly different from that of the D570 and D630 treatments(P<0.05).The results of the principal component analysis showed that the structure and diversity of soil bacterial and fungal communities were significantly affected by different thinning retention densities of C.lanceolata.Mantel's r analysis of superimposed heat maps indicated that C/N in soil was the most important environmental factor affecting bacterial diversity,and C/N,C/P,N/P,and NO3--N content were the most important factors affecting fungal community diversity.Reasonable retention density of C.lanceolata(375 plant·hm-2)can improve the growth environment of the understory vegetation of C.lanceolata-P.bournei compound storied forest,changing the soil structure and nutrient distribution,increasing the key microbial groups in soil,and promoting the turnover of soil nutrients,which is crucial for the maintenance of soil fertility and ecosystem health.
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