节水灌溉稻田叶片与冠层水碳通量联合模拟与机理性尺度提升

Variation and simulation of water and carbon fluxes in farmland have garnered much attention. Such information is important for agricultural water management and ecological sustainable development. Water-saving irrigation practice is the key to efficient water use, which results in the changes in energy and material circulation, as well as in water and carbon fluxes transfer at different interfaces in rice canopy. In the present study, water and carbon fluxes at leaf and canopy scales of paddy fields will be measured by portable photosynthesis system, soil automated CO2 flux measurement system, micro-lysimeter system and eddy covariance system, to analyze the variation and characteristics of water and carbon fluxes at the different scales in water-saving irrigation rice fields. The vertical distribution of the leaf area, leaf age and net radiation at different levels within the canopy will be discussed quantitatively, and then the coupling simulation model of water and carbon fluxes will be constructed at different scales or different interfaces. In addition, combined with the micro-meteorological conditions (net radiation, wind speed, temperature and humidity) within the canopy, the mechanistic up-scaling model of water and carbon fluxes from leaf to canopy scale will be achieved with the integration of each flux and meteorological factor. The current results are beneficial for understanding the process of water and carbon fluxes movement at different scales in water-saving irrigated paddy fields, and realizing the water use efficiency and reduction of carbon emissions. It is also of great theoretical and practical value in formulating the sustainable development of crop under the climate change conditions.

稻田水碳变化规律与模拟，是目前农田水管理与生态可持续发展的热点研究。节水灌溉模式是高效用水的关键，但其改变了物质和能量的循环过程，这必将导致稻田不同界面不同过程水碳通量的变化。本项目以节水灌溉稻田为研究对象，采用光合仪、土壤呼吸通量测量系统、微型蒸渗仪及涡度相关系统等连续监测叶片、冠层不同界面水碳通量，阐明节水灌溉稻田不同尺度水碳通量变化规律与主要特征；定量描述水稻冠层内部叶面积、叶龄的垂直分布，以及冠层辐射的垂直分布，构建节水灌溉条件下稻田不同界面的水碳通量精细模拟模型；结合冠层内微气象条件（风速、温、湿度垂直分布），通过各通量和气象因子在冠层内的积分，实现叶片到冠层尺度水碳通量的机理性提升。研究成果对于深刻认识节水灌溉稻田不同尺度水碳运动规律，实现稻田高效用水与减少碳排放，制定气候变化条件下可持续稻作发展对策等具有重要的理论意义和实用价值。

稻田水碳变化规律与模拟，是目前农田水管理与生态可持续发展的热点研究。节水灌溉模式是高效用水的关键，但其改变了物质和能量的循环过程，这必将导致稻田不同界面不同过程水碳通量的变化。本项目以节水灌溉稻田为研究对象，采用现场试验和模型模拟相结合的方法，研究了节水灌溉稻田叶片、冠层和田间三个尺度水碳通量的变化特征及其影响因素，揭示了水碳通量耦合过程及其尺度差异；分析叶片气孔导度（gsw）对叶龄（叶片出叶天数LA）、田间含水率（θ）和气象因子的响应关系，构建了引入参数LA的改进Jarvis叶片气孔导度模型；通过改进Jarvis叶片气孔导度模型连接Penman Monteith（P-M）和Farquhar叶片模型建立了适合于不同LA的叶片的水碳耦合（gsw-光合速率Pn-蒸腾速率Tr）模拟模型；通过Jarvis冠层导度模型连接P-M和Farquhar大叶模型分别拟合冠层和田间尺度的水碳通量，分析其模型尺度差异；分别通过叶片气孔导度到冠层的提升和叶片蒸腾光合到单穴水稻植株的提升，实现了叶片到冠层尺度水碳通量耦合模拟模型的机理性提升。引入叶片叶龄的稻田水碳通量耦合模拟模型能从机理上反映稻田不同尺度的水碳耦合关系和变化特征，机理性的水碳通量精细模拟与空间尺度提升模型将为理解稻田生态系统水循环和碳同化量积累过程，优化灌溉制度和提高水分利用效率提供基础依据。

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