【摘要】 稻田甲烷（CH₄）排放通量的研究是当前陆地生态系统碳循环研究的重要组成部分和热点问题之一。利用2016年江苏句容生态实验站稻麦轮作农田生态系统涡度相关原位观测数据，分析了稻田CH₄排放通量昼夜变化特征及其主要影响因子（总初级生产力GPP,gross primary productivity、潜热通量LE,latent heat flux、空气温度TA,air temperature、土壤温度TS,soil temperature）,并采用波谱-Granger因果分析方法，从因果分析角度重点探讨了稻麦轮作农田生态系统中水稻生长季的稻田CH₄排放通量昼夜变化原因，结果表明：在稻麦轮作农田生态系统中小麦生长季的农田CH₄排放通量较低，昼夜变化特征不明显；水稻生长季的稻田CH₄排放通量呈现明显单峰值昼夜变化特征，峰值出现在13:00—16:00之间。在小时尺度上，GPP和LE昼夜变化的峰值出现的时间（11:30和14:00）早于稻田CH₄通量（14:30）,而温度（TA、TS）峰值（15:30和16:30）滞后于稻田CH₄通量和GPP、LE。在频率域上GPP、LE、TA、TS与稻田CH₄通量在1d和12h周期上存在较强的共振关系；GPP、LE与稻田CH₄通量之间存在明显的因果关系，而TA、TS与稻田CH₄通量之间在长时间尺度上的因果关系更加明显。在日内时间尺度，相对于气温和土壤温度，与光合和蒸散相关的GPP、LE是更重要的稻田CH₄通量昼夜变化的影响因子。本研究可为构建稻田CH₄排放模型提供因果机理性解释。更多还原

【Abstract】 The study of CH₄ emission flux in rice fields is an important part and one of the hot issues in the current carbon cycle research of terrestrial ecosystems. This paper was devoted to identifying diurnal change patterns of CH₄ emission fluxes by using eddy covariance（EC） measurement, and to analyzing the linkages of CH₄ fluxes with different biophysical factors on a diurnal timescale based on the spectral Granger causality analysis method in Jurong Ecological Experimental Station（JREES） in 2016. The results show that: the CH₄ fluxes showed distinguishable diurnal variations with single peaks during 13:00—16:00 h local time. In the non-rice growing season, the CH₄ fluxes were very low, and the diurnal variation characteristics were not obvious. At the diurnal timescale, CH₄ fluxes reached daily maximums at 14:30 h, later than gross primary productivity（GPP）（11:30 h） and latent heat flux（LE）（14:00 h）, and earlier than air temperature（TA）（15:30 h） and soil temperature（TS）（16:30 h）. Wavelet coherence has high periodic coherence at the 24 h and 12 h timescales and lower periodic coherence at the weekly timescales between TA, TS, and CH₄ fluxes throughout the rice-growing season. GPP regulates CH₄ fluxes after accounting for the effects of LE, TA, and TS on CH₄ fluxes. LE mirrored the diurnal pattern of CH₄ fluxes when the effects of TA and TS on CH₄ fluxes were considered. Therefore, GPP and LE related to photosynthesis and evapotranspiration are more important factors affecting the diurnal variation of CH₄ fluxes in rice fields than air temperature and soil temperature. This study can provide a causal mechanism explanation for constructing a CH₄ emission model from rice fields.更多还原