石膏改良剂减少苏打盐碱稻田甲烷排放的微生物学机制

Microbiological mechanisms of gypsum as an amendment to reduce methane emissions from saline-sodic paddy fields

摘要:

目的 阐明石膏改良剂减少苏打盐碱稻田甲烷(CH₄)排放的微生物学机制与主要路径。方法 开垦盐碱荒地为稻田，设置4个石膏用量处理：0 t/hm² (CK)、15 t/hm² (G₁₅)、30 t/hm² (G₃₀)和45 t/hm² (G₄₅)，每个处理设置3次重复。在水稻扬花期，采用静态箱法监测CH₄排放通量，随后采集箱内耕层(0-15 cm)土壤样品，用于宏基因组测序和土壤理化性质分析。结果 施用石膏15-45 t/hm²能够显著减少苏打盐碱稻田CH₄排放通量，减排幅度为85.62%-92.64%，且随着石膏用量增加减排效果逐渐增强。施用石膏并未改变苏打盐碱稻田土壤中产甲烷菌和甲烷氧化菌的优势菌门。产甲烷菌中氢营养型相对丰度高达90%。当石膏用量达到30 t/hm²时，Type Ⅱ型甲烷氧化菌相对丰度较CK处理提高了50.00%-61.54%；随着石膏用量增加，产甲烷菌和甲烷氧化菌的α多样性指数均增大，且甲烷氧化菌的增幅明显高于产甲烷菌。石膏显著降低了产甲烷功能基因torC的相对丰度，同时提高了甲烷氧化功能基因pps、hdrD和rnfB的相对丰度。CO₃^2-+HCO₃^-和pH是影响产甲烷菌和甲烷氧化菌群落结构的最主要土壤环境因子。结论 施用石膏通过降低土壤pH正向调节产甲烷菌和甲烷氧化菌的群落结构。然而，甲烷氧化菌群落结构对CH₄排放通量的负效应强于产甲烷菌群落结构对CH₄排放通量的正效应，从而减少CH₄排放。该结果为苏打盐碱地农业开发的生态效应评估提供了理论依据。

Abstract:

Objective To elucidate the microbiological mechanisms and major pathways of gypsum as an amendment to reduce CH₄ emissions from saline-sodic paddy fields.Methods The saline-sodic wasteland was reclaimed as a paddy field, and four gypsum application treatments were set up: 0 t/hm² (CK), 15 t/hm² (G₁₅), 30 t/hm² (G₃₀), and 45 t/hm² (G₄₅), with three replications. The CH₄ emission fluxes were monitored by the closed static chamber method at the rice flowering stage, after which soil samples were collected from the tillage layer (0-15 cm) within the chamber area for metagenomic sequencing and soil physicochemical property analysis.Results The application of 15-45 t/hm² gypsum significantly reduced the CH₄ emission flux of saline-sodic paddy fields by 85.62%-92.64%, and the reduction amplitude increases with the increase of gypsum application rate. The dominant phyla of methanogens and methanotrophs of saline-sodic paddy soils did not change with the application of gypsum, and the relative abundance of hydrogenotrophic type of methanogens was as high as 90%. The relative abundance of Type Ⅱ methanotrophs increased by 50.00%-61.54% compared with that of the CK treatment after the gypsum application reached 30 t/hm². The alpha diversity index of both methanogens and methanotrophs increased with the increase of gypsum application rate, and the increase of the former was significantly smaller than that of the latter. Gypsum significantly decreased the relative abundance of the methanogenic functional gene torC, and increased the relative abundance of the methane oxidation functional genes pps, hdrD and rnfB. CO₃^2-+HCO₃^- and pH were the most important environmental factors of soil affecting the community structure of methanogens and methanotrophs.Conclusion The application of gypsum positively affected the community structure of methanogens and methanotrophs by reducing soil pH, but the negative effect of the community structure of methanotrophs on CH₄ emission flux outweighed the positive effect of the community structure of methanogens on CH₄ emission flux, thus reducing CH₄ emission. The results can provide a theoretical basis for the evaluation of ecological effects of agricultural development in saline-sodic land.