咖啡果皮与枯落物覆盖对土壤有机碳组分的影响

Effects of Coffee Peel and Litter Mulch on Soil Organic Carbon Fractions in Coffee Plantations

农田土壤有机碳库作为陆地土壤碳库的重要组成部分,其有机碳储量受到种植模式等人为干预的强烈影响。咖啡作为世界热带地区种植面积较大的的经济作物之一,其栽培模式的微小变化即可显著影响陆地生态系统的碳收支平衡。覆盖栽培是咖啡的传统栽培模式之一,然而其对咖啡园土壤有机碳组分的影响仍不明确。因此,本研究基于课题组前期使用咖啡果皮与枯落物等咖啡废弃物替代传统覆盖物对咖啡进行覆盖栽培,采用完全随机区组设计,分别设置未覆盖咖啡废弃物(CK)、覆盖咖啡枯落物(L)、覆盖咖啡果皮(P)和覆盖咖啡枯落物+果皮(PL)4种处理;监测咖啡园的土壤微环境、微生物群落多样性及生物量碳、有机碳组分等指标,通过分析土壤微环境、微生物群落结构与有机碳组分之间的内在关系,明确覆盖咖啡废弃物对土壤碳组分的影响及其关键驱动因子。结果显示:覆盖咖啡果皮与枯落物均不影响土壤有机碳、重组有机碳和可溶性有机碳含量,而分别显著提高土壤轻组有机碳含量13.31%和14.12%。覆盖咖啡废弃物不影响土壤微环境指标与微生物群落多样性。覆盖咖啡果皮显著提高土壤微生物量碳14.05%,并且分别显著增加变形菌门(Proteobacteria)和厚壁菌门(Firmicutes)相对丰度18.60%和80.77%,并减少蓝细菌门(Cyanobacteria)相对丰度70.14%,却对土壤真菌群落的影响较小;而覆盖咖啡枯落物分别显著增加变形菌门和厚壁菌门相对丰度14.43%和57.63%,并减少蓝细菌门相对丰度73.43%,同时显著提高真菌子囊菌门(Ascomycota)相对丰度14.79%。本研究中咖啡废弃物覆盖不影响土壤有机碳含量主要归因于重组有机碳等主要土壤有机碳组分对咖啡废弃物覆盖处理不敏感;而咖啡废弃物覆盖引起微生物量碳的提高以及厚壁菌门在土壤微生物群落相对丰度的增加,促进了外源有机碳输入引起的激发效应,是显著提高土壤轻组有机碳含量的主要原因之一。咖啡废弃物短期覆盖显著提高土壤轻组有机碳含量,有助于提升咖啡园土壤碳固存以及为优化咖啡绿色低碳生产模式提供理论支撑。

As an important component of terrestrial soil carbon reservoirs,the agricultural soil organic carbon pool is greatly influenced by cultivation patterns.Coffee,one of the major economic crops in tropical regions of the world,a minor changes of its cultivation pattern can significantly affect the carbon balance of terrestrial ecosystems.Mulching cultivation is one of the traditional cultivation models for coffee,but its impact on the organic carbon composition of coffee plantation soil is still unclear.Therefore,based on the previous research of our team using coffee peel and leaf litter as substitutes for traditional mulch to cultivate coffee,four mulching treatments were set up in this study:uncov-ered coffee waste(CK),coffee leaf litter mulch(L),coffee peel mulch(P),and both coffee peel and litter mulch(PL).Soil micro-environment,microbial community diversity and biomass,organic carbon fractions,and other indicators were monitored in the coffee plantation,and the intrinsic relationships between soil micro-environment,microbial community structure,and organic carbon fractions were analyzed to investigate the effects of coffee waste cover on soil components and the key driving factors.The results showed that coffee waste cover did not affect the content of soil organic carbon(SOC),heavy fraction organic carbon(HFOC),and dissolved organic carbon(DOC),while coffee peel and litter mulch significantly increased the content of soil light fraction organic carbon(LFOC)by 13.31%and 14.12%,respectively.Coffee waste mulch did not affect soil micro-environment indicators or microbial diversity.Coffee peel cover significantly increased soil microbial biomass by 14.05%,and increased the relative abundance of Proteobacteria and Firmicutes by 18.60%and 80.77%,respectively,while reducing the abundance of Cyanobacteria by 70.14%,but had little impact on soil fungal community.Coffee litter mulch significantly increased the relative abundance of Proteobac-teria and Firmicutes by 14.43%and 57.63%,respectively,while reduced the abundance of Cyanobacteria by 73.43%,and significantly increased the relative abundance of dominant fungi Ascomycota by 14.79%.The reason why coffee waste mulch did not affect the soil organic carbon content is mainly attributable to the insensitivity response of HFOC content to coffee waste mulching.The increase of microbial biomass and the increase relative abundance of Firmicutes are the main reasons to enhance the excitation effect caused by external organic carbon input,thus significantly in-creasing the content of soil LFOC content.The short-term mulch of coffee waste significantly increased the content of soil LFOC content,which is contribute to improve the soil carbon storage of coffee plantations and optimize the green and low-carbon production mode of coffee.