摘要
摘要:为了探究不同管理措施对湖北省主要稻作系统CH₄和N₂O周年排放的影响, 利用田间观测数据验证DNDC模型后, 结合地理信息系统(ArcGIS)模拟和测算湖北省不同稻作系统温室气体的周年排放。本研究于2019年在鄂西北的枣阳市设置水稻-小麦(RW)、水稻-再生稻(RO)稻作系统, 在鄂东南的武穴市设置RO、水稻-油菜(RR)稻作系统, 在江汉平原的潜江市设置RW、RO、RR稻作系统, 每个稻作系统均设置常规栽培和优化栽培(包括氮肥深施、节水灌溉、秸秆还田等)两个模式, 通过静态箱法测定温室气体CH₄和N₂O的周年排放特征。大田验证试验结果显示, 不同稻作系统不同栽培模式下CH₄和N₂O排放实测值与模拟值归一化均方根误差(NRMSE)值为19.3%~24.2%, 模型拟合度在可接受范围之内。DNDC模型模拟和估算结果表明, 湖北省稻作区增温潜势(GWP)表现为江汉平原>鄂东南>鄂西北, 不同区域稻作系统CH₄的排放总量、N₂O的排放总量和GWP均表现为RW>RO>RR。优化栽培管理模式可以明显减少CH₄和N₂O排放, 与常规栽培管理模式相比, 优化栽培管理模式下RW、RO和RR的单位面积CH₄排放量分别降低9.5%~18.0%、7.3%~18.4%和18.2%~22.4%, N₂O排放量分别降低4.2%~14.2%、6.9%~24.7%和8.8%~18.1%。优化栽培管理后, 各地区的GWP表现为, 鄂西北: 襄阳>十堰>神农架; 鄂东南: 黄冈>咸宁>武汉>黄石>鄂州; 江汉平原: 荆州>荆门>孝感>随州>天门>仙桃>潜江。优化栽培管理模式下鄂西北、鄂东南和江汉平原稻田CH₄周年排放总量较常规栽培管理模式分别降低11.8%、14.4%和16.3%, 稻田N₂O周年排放总量分别降低82.4%、77.5%和83.0%。本研究结果表明, DNDC模型可以较好地模拟湖北省不同稻作系统下温室气体的排放, 同时优化稻作管理模式对稻田生产具有好的减排效果, 为在湖北省推广该模式提供理论依据。
关键词:稻作系统/
优化管理/
DNDC模型/
甲烷/
氧化亚氮
Abstract:This study explored the impacts of different management measures on the annual emissions of methane (CH₄) and nitrous oxide (N₂O) from the main rice-based cropping systems in Hubei Province using the denitrification-decomposition (DNDC) model and observed emission data to estimate the annual greenhouse gas emissions via a geographic information system (ArcGIS). In 2019, rice–wheat (RW) and rice–ratoon rice (RO) cropping systems were implemented in Zaoyang City of Northwest Hubei, RO and rice–oilseed rape (RR) cropping systems were implemented in Wuxue City of Southeast Hubei, and RW, RO, and RR cropping systems were implemented in Qianjiang City of the Jianghan Plain. There were two cultivation modes for each rice-based system: conventional cultivation and optimized cultivation. The optimized mode included deep application of nitrogen fertilizer, water-saving irrigation, and straw returning to the field. The annual fluxes of CH₄ and N₂O were measured using the static closed chamber method. The field validation results showed that the normalized root mean square error between the observed and simulated values of CH₄ and N₂O emissions ranged from 19.3% to 24.2% under different rice-based cropping systems with different management practices, and the degree of model fitting was acceptable. According to the simulation results of the DNDC model, the global warming potential (GWP) for the rice growing regions in Hubei Province followed the order of Jianghan Plain > Southeast Hubei > Northwest Hubei, and the annual cumulative emissions of CH₄, N₂O, and GWP under different rice-based cropping systems in different regions was in the order of RW > RO > RR. The cultivation modes significantly affected the CH₄ and N₂O emissions. Compared with conventional cultivation, optimized cultivation lowered the CH₄ emissions per unit area by 9.5%–18.0%, 7.3%–18.4%, and 18.2%–22.4% under RW, RO, and RR, respectively. The N₂O emissions lowered by 4.2%–14.2%, 6.9%–24.7%, and 8.8%–18.1%, respectively. Moreover, compared with conventional cultivation, optimized cultivation decreased the annual cumulative CH₄ emissions by 11.8%, 14.4%, and 16.3% in Northwest Hubei, Southeast Hubei, and the Jianghan Plain, respectively, and decreased the annual cumulative N₂O emissions by 82.4%, 77.5%, and 83.0%, respectively. Under optimized cultivation, the GWP for Northwest Hubei was in the order of Xiangyang > Shiyan > Shennongjia, that for Southeast Hubei was in the order Huanggang > Xianning > Wuhan > Huangshi > Ezhou, and that for the Jianghan Plain was in the order Jingzhou > Jingmen > Xiaogan > Suizhou > Tianmen > Xiantao > Qianjiang. Our results show that the DNDC model can suitably simulate the greenhouse gas emissions of different rice-based cropping systems in Hubei Province. An optimized cultivation mode is needed to mitigate greenhouse gas emissions during rice production in Hubei Province.
Key words:Rice-based cropping system/
Optimized cultivation/
Denitrification-decomposition (DNDC) model/
CH₄/
N₂O



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