Effects Of Management Measures On Soil Nutrients And Microbial Communities In Rhizosphere Of 10-Year-Old Chinese Fir Plantation

Cunninghamia lanceolata is a famous fast-growing timber species in China.Under the influence of highly intensive management and some unreasonable forest management and cultivation measures,increasing the productivity of Chinese fir forest land and achieving sustainable forestry development have attracted wide attention of the society.This study was carried out at the National Field Scientific Observation and Research Station of Chinese fir forest ecosystem in Huitong County,Hunan Province.Ten-year-old Chinese fir plantation was selected as the research object.The thinning,tending and compound fertilizer treatment experiments were carried out under the condition of declining soil fertility and high stand density.The concentration gradients A1,A2,A3(250 g/plant,500 g/plant,750 g/plant)of different compound fertilizer and the remaining thinning were studied.The effects of BL on nutrient content and microbial diversity in rhizosphere soil of Chinese fir plantation are summarized as follows:(1)The C,N and P indices of rhizosphere soil showed significant differences among different treatments.In this study,the retention of thinning residues could significantly increase the carbon,nitrogen and phosphorus content of surface rhizosphere soil.In fertilization treatment,the growth rate of organic carbon content in A1 treatment(250g/plant)was higher than that in other treatments(13.77%),while that in A2 treatment(500g/plant)was higher than that in other treatments(19.8%and 29.27%respectively).(2)The content of ammonium nitrogen and nitrate nitrogen increased after BL treatment for half a year,while the content of available phosphorus decreased.In fertilization treatment,the growth rate of A2 treatment(500g/plant)was higher than that of other treatments.Among them,ammonium nitrogen content increased 26.29%,nitrate nitrogen content increased 17.88%,and available phosphorus content increased 26.48%.(3)The growth rate of microbial biomass in rhizosphere soil of Cunninghamia lanceolata forest was higher than that before treatment.The growth rate of microbial phosphorus content was the highest,and the difference of microbial carbon content was not significant.In the fertilization treatment,the growth rate of microbial carbon content was not significant,but there were significant differences among the other treatments.The growth rate of microbial carbon,nitrogen and phosphorus content in A2 treatment was the most significant.Microbial carbon content increased by 0.37%,microbial nitrogen content increased by 47.25%,and microbial phosphorus content increased by 28.09%.(4)The activity of soil enzymes in rhizosphere of Chinese fir plantation control group decreased compared with half a year ago.The largest increase of soil enzymes in BL treatment was urease,the increase was 39.53%,and the difference of acid phosphatase activity was the least significant.In all treatments,the activity of rhizosphere soil enzymes of Chinese fir plantations was increased,and the increase of rhizosphere soil enzymes was the most significant in A2 treatment(500g/plant).The increase of urease and invertase activities was more significant,88.41%and 48.73%respectively.(5)According to ITS sequencing results,the number of fungal OTUs in BL treatment was higher than that in half a year ago.In A2 treatment(500 g/plant),the growth rate of fungal OTUs was the highest.The diversity and richness of fungal community were higher in BL treatment and fertilization treatment than in control.When A2 treatment(fertilization amount was 500 g/plant),the richness of fungal community increased most.(6)The dominant fungi in all plots were unclassified fungi k Fungi,Agaricomycetes and Archaeorhizomycetes.Compared with six months later,Tremellomycetes and Wallemiomycetes of Tremella class and Arthrobasidia class were the new dominant fungi in each sample treatment,which showed that fertilization treatment and BL treatment could effectively improve the structure of fungi community.Diversity.Among available nutrients,available phosphorus has the greatest impact on fungal community structure,catalase has the greatest impact on fungal community diversity in enzyme activity,and microbial P has the greatest impact on fungal community structure in microbial carbon,nitrogen and phosphorus.(7)The 16Sr RNA sequencing results showed that the number of bacterial OTUs in BL treatment was higher than that in half a year ago.In fertilization treatment,the growth rate of bacterial OTUs in A2 treatment(500 g/plant)was the highest.In general,the diversity and richness of bacterial community were higher in BL treatment and fertilization treatment than in the control.When A2 treatment(fertilization amount was 500 g/plant),the richness of bacterial community increased most.(8)The dominant bacteria in all plots were Acidobacteria,Alphaprotebacteria,Actinobacteria.The dominant bacteria in all plots were OPB35 soil group.At the same time,the proportion of acidophilic bacteria and alpha-proteobacteria in BL plots increased,and the proportion of actinomycetes in BL plots increased most significantly,while the proportion of actinomycetes in BL plots decreased.Low,the proportion of A2 treatment decreased most significantly.Among available nutrients,ammonium nitrogen has the greatest influence on bacterial community structure,catalase has the greatest influence on bacterial community structure in enzyme activity,and microbial N has the greatest influence on bacterial community structure in microbial carbon,nitrogen and phosphorus.