局部灌溉农田水碳通量组分消长机制与节水固碳效应

Quantifying characterization of the growths and declines in components of water and carbon fluxes in the partial rootzone irrigating cropland is significant for the rational regulation of agricultural water use and the improvement of crop water efficiency for carbon sequestration. Based on the past research for partitioning evapotranspiration in croplands with stable isotopic method, stable water and carbon dioxide isotopic fluxes (Stable Isotopic Flux) will be monitored by advanced in situ continuous analysis system for stable isotopic composition in partially irrigated cropland to partition the components of water and carbon fluxes combined with Keeling-Plot method, which include dynamic processes of crop canopy transpiration and soil evaporation, photosynthesis and autotrophic respiration of crop, and soil heterotrophic respiration. These results will be compared and corrected with the values measured with the traditional methods. The quantitative relationship between the transient process of water carbon flux components and environmental factors were analyzed to find out the key control processes and the main control factors. The change trend of water/carbon flux components ratios will be studied to reveal the compensation effect of partial rootzone irrigation on crop transpiration/photosynthesis and its inhibiting mechanism of soil evaporation and respiration. Crop water efficiency for carbon fixation at the levels of leaves, canopy, ecosystem, dry biomass and economic yield will be compared and the interconnection relationship among them will also be qualified to determine the key scale transformation parameter, and provide the scientific basis for reasonable application of partial rootzone irrigation in China.

定量表征局部灌溉农田水碳通量组分消长规律，对合理调控农田水碳循环过程，提高作物水分固碳效率具有重要意义。在过去利用稳定同位素方法分摊农田蒸散研究的基础上，进行大田玉米局部灌溉控制试验，采用先进的稳定同位素原位连续分析系统监测农田水和二氧化碳稳定同位素通量(Stable Isotopic Flux)，结合Keeling-Plot方法分摊作物群体蒸腾与土壤蒸发以及作物群体光合、自养呼吸和土壤异养呼吸动态过程，并用传统方法的测定结果进行验证。分析农田水碳通量及其组分对局部灌溉的响应机理以及与环境要素的定量关系，找出关键控制过程和主控因子。研究春玉米田水碳通量组分构成比例变化，揭示局部灌溉对作物蒸腾-光合的补偿效应和土壤蒸发-呼吸的抑制机理。比较作物叶片、群体、农田生态系统、干物质和经济产量水平春玉米水分固碳效率，确定它们之间的互联关系以及关键尺度转换参数，为我国发展局部灌溉提供理论依据。

从水碳耦合作用的角度，科学系统地阐明局部灌溉条件下阐明基于水碳耦合的节水、增产和减排效应的作用机制，对发展局部灌溉技术及其制定合理的灌溉制度具有重要的科学意义。项目构建了农田水碳通量分割的稳定同位素方法及系统，监测分析覆膜滴灌和大水漫灌条件下农田土壤水蒸发与呼吸、作物茎秆液流与净光合、和冠层上方水碳通量及水碳氢氧稳定同位素的动态变化规律。采用Keeling-Plot方法确定作物蒸腾与蒸散日值、冠层叶片光合与群体净光合的比值，并与传统方法确定的日值比值进行了比较和校正。利用涡度系统确定的ET、Fc瞬时值和水碳稳定同位素分辨率瞬时值，分摊得到了作物群体蒸腾和土壤蒸发以及作物群体光合、自养呼吸和土壤异养呼吸瞬时值。确立了覆膜滴灌和大水漫灌条件下作物蒸腾和土壤蒸发以及作物群体光合、自养呼吸和土壤异养呼吸瞬时动态与不同层次的土壤含水率、气象因子、叶面积指数之间的定量关系，揭示了覆膜滴灌有效抑制土壤蒸发-呼吸并且促进玉米蒸腾-光合的机制。分析比较了植株群体和生态系统以及干物质、经济产量水平的春玉米水分固碳效率，发现覆膜滴灌作物群体、农田生态系统、干物质和经济产量水平水分固碳效率均显著高于大水漫灌。