Microbial Mechanism Of Soil Organic Carbon Storage In Plantation Driven By Organic Fertilizer

Forest ecosystems harbored a large amount of soil organic carbon,and changed in their soil carbon storage capacity would have a significant impact on the global carbon balance.Organic fertilizers could improve soil quality by building microbial-soil interactions,thus enhancing soil carbon storage.There were many studies on microbial-soil interactions,but few involve the microbial mechanisms of soil carbon storage in plantation forests driven by organic fertilizers,and further research was needed.In this experiment,three different fertilization methods,namely,biochar with tea husk,organic fertilizer with tea meal and organic fertilizer/biochar mixture,were used to fertilize the plantation with 2%and 5%of the soil weight of biochar and organic fertilizer,respectively,and no fertilizer was used as the control.Preliminary studies were conducted to investigate the changes in soil microbial community structure and carbon source metabolism function under different fertilization treatments,to explore the effects of different fertilization methods on soil microbial community and soil carbon storage,and to reveal the role of tea meal organic fertilizer application on soil carbon storage from the perspective of plant-soil-microbial interrelationship.The preliminary study contents and results are as follows:(1)Effects of different planting and fertilization methods on soil quality,enzyme activity,and plant growth.After applying biochar alone,soil pH increased from 4.96 to 6.00,and there was no significant change in soil carbon fraction and effective fraction content(fast-acting phosphorus,fast-acting potassium,ammonium nitrogen,and nitrate nitrogen),while soil enzyme activity decreased.The application of tea meal organic fertilizer alone and tea meal organic fertilizer with tea husk biochar significantly increased the contents of soil organic matter,soil organic carbon,soluble organic carbon,light fraction organic carbon,microbial quantity carbon,and soil effective fraction,and effectively increased soil enzyme activity.In the short term,the effect of a single application of tea meal organic fertilizer was overall better than the mixed application of tea meal organic fertilizer and tea husk biochar,meanwhile,a single application of tea meal organic fertilizer significantly promoted plant growth and improved the competitive effect among plants in the short term.(2)Effects of different planting methods and fertilizer application on soil carbon sequestration.The largest increase in soil organic carbon was observed under mixed planting of fir and cycad,with a storage capacity of 2.17 t/hm2 and a sequestration rate of 4.33 t/(hm2·a),followed by fir planted alone.On the basis of planting,tea meal organic fertilizer alone had a more significant increase in soil carbon storage and carbon sequestration rate than tea husk biochar alone and organic fertilizer with biochar.(2)Effects of different planting and fertilization methods on soil carbon storage.Soil organic carbon increased the most under mixed planting of cedar and cycad,with a storage capacity of 2.17 t/hm2 and a carbon sequestration rate of 4.33 t/(hm2·a),followed by cedar alone.Within the short-term experiment,the increase in soil carbon storage and carbon sequestration rate was more significant with the application of tea meal organic fertilizer alone than with the application of tea husk biochar alone and tea husk organic fertilizer with tea husk biochar on the basis of planting.(3)Effects of fertilizer application on soil bacterial diversity and community composition.The ACE index and Chao1 index of soil bacteria were the highest under the application of tea husk biochar alone,while the Shannon index and Simpson index of bacteria did not change significantly.The dominant bacterial phyla in the soil were Proteobacteria and Acidobacteria,and most of the dominant genera were unclassified genera under them.There were differences in the relative abundance of bacterial communities under a single application of tea husk biochar,a single application of tea meal organic fertilizer,and tea meal organic fertilizer with tea husk biochar,but the effect of different planting methods on the structure of bacterial communities was not significant.In the short-term experiment,the effect of a single application of tea meal organic fertilizer on the bacterial community was more significant,and soil organic matter,organic carbon,easily oxidized organic carbon,total nitrogen,and fast-acting phosphorus were the main factors affecting the soil bacterial community.(4)Fertilizer application on soil fungal diversity and community composition.The highest fungal diversity was found in the cedar planting group.The organic fertilizer of tea meal alone with application significantly increased the fungal ACE index,Chaol index,and Shannon index,and reduced the gap of this index between different planting groups.Ascomycota,Basidiomycota,and Mortierellomycota were the dominant fungal phyla in the soil,and organic fertilizer significantly increased the relative abundance of the dominant fungal phyla.The fungal community structure was significantly different under different fertilization treatments,especially between tea shell biochar alone and tea meal organic fertilization alone.The fungal community structure in the soil with a single application of tea meal organic fertilizer and tea meal organic fertilizer with tea husk biochar was a cluster and more similar,and the single application of tea husk biochar and the control was a cluster.Short-term experiments showed that the plant cultivation and tea meal organic fertilizer application alone was more beneficial to enhance the connection and interaction between soil fungal communities.(5)Effect of fertilizer application on soil microbial carbon source metabolism.The application of tea meal organic fertilizer improved soil microbial activity and increased the functional diversity of soil microbial communities.Compared with a single application of tea husk biochar and tea meal organic fertilizer with tea husk biochar,a single application of tea meal organic fertilizer significantly increased the average absorbance value of microbial carbon source metabolism,and the main type of carbon source utilized shifted from polymers to carbohydrates,carboxylic acids,and alcohols;in the short term,tea meal organic fertilizer application significantly increased the Shannon index and McIntosh index of microorganisms.The correlation analysis between soil physicochemical properties and microbial metabolic functions showed that the contents of soil organic matter,total organic carbon,light component organic carbon and easily oxidized organic carbon were the key factors affecting the functional characteristics of soil microbial diversity.In conclusion,the pot experiment showed that,in the short term,the organic fertilizer with tea meal alone was more beneficial to the improvement of soil quality,which could significantly increase the content of soil available nutrients and carbon fractions,thus promoting plant growth,while providing sufficient carbon sources and nutrients for microbial growth,improving microbial carbon metabolism and soil carbon sequestration rate,and increasing soil carbon storage.