灌溉农田动态耗水结构与群体蒸腾效率的稳定同位素研究

Irrigation is a key factor to guarantee a high and stable yield in agricultural system in the North China Plain (NCP). Given the limited available water resource in this region, researches on agricultural water consumption are primary for the sustainable utilization of water resource and the development of water-saving agriculture. Dynamic water consumption structure and group transpiration efficiency studies of the cropland have significant meanings for the reasonable use of water resource. Current studies mainly focused on the short-time period study by scattered sampling methods, lacking of a direct approach to obtain the evaporation-transpiration vapor data. As a result, it is hard to clarify the effect of irrigation to the land-atmosphere water transfer. Moreover, most findings paid attentions on the evapotranspiration partition itself, and ignored the relationship between water consumption structure and ecosystem productivity. This research was conducted in the typical irrigated agricultural ecosystem in the NCP by measuring the isotopic composition characteristic and water-carbon fluxes using stable isotopes analyzer - water vapor chamber combined eddy covariance system methods. Our aims are to clarify the annual, seasonal and daily change law of the isotopic composition of water vapor, to identify the spatio-temporal effects of irrigation on vapor transfer, further to illuminate the dynamic process of water consumption and group transpiration efficiency and therefore to understand the relationship between water transfer in the land-atmosphere system and ecosystem productivity. Our study will supply references to develop an efficient utilization system of irrigated water as well as to provide scientific basis for agricultural water management.

灌溉是华北平原农业高产稳产的重要保证，灌溉农田的水分消耗研究对该地区水资源可持续利用和节水农业发展具有重要意义，研究农田动态耗水结构和群体蒸腾效率有利于水资源的合理利用。以往的蒸散结构研究局限于短暂离散取样，缺少直接实时获取蒸腾和蒸发水汽的手段，难以明确灌溉对陆地-大气水分交换的影响，研究结果大多仅停留在蒸散分离本身，缺少与生态系统生产力的联系。本研究针对华北平原典型灌溉农田生态系统，采用稳定同位素分析仪-水汽室法结合涡度相关系统进行实时高频连续水汽稳定同位素组成特征和水、碳通量变化研究，明确农田水汽稳定同位素特征的年-季-日变化规律及灌溉对水汽转化产生的时空影响，阐明耗水结构的动态变化过程，揭示农田群体蒸腾效率变化规律，深入认识陆面-大气系统水分转化与生态系统生产力之间的关系，为灌溉水有效利用提供诊断依据，为农业水科学管理提供决策依据。

灌溉是华北平原农业高产稳产的重要保证，灌溉农田的水分消耗研究对该地区水资源可持续利用和节水农业发展具有重要意义，研究农田动态耗水结构和群体蒸腾效率有利于水资源的合理利用。以往的蒸散结构研究局限于短暂离散取样，缺少直接实时获取蒸腾和蒸发水汽的手段，难以明确灌溉对陆地-大气水分交换的影响，研究结果大多仅停留在蒸散分离本身，缺少与生态系统生产力的联系。本研究针对华北平原典型灌溉农田生态系统，采用稳定同位素分析仪-水汽室法结合涡度相关系统进行实时高频连续水汽稳定同位素组成特征和水、碳通量变化研究，发现农田水汽稳定同位素组成受降雨和蒸散水汽的影响全年呈现先变重后变轻的倒“V”形变化，蒸发与蒸腾水汽氢氧同位素组成具有很好的线性关系，氢同位素(D)在分馏过程中比氧同位素(18O)敏感，蒸发和蒸腾水汽稳定同位素的组成可以较好地反映蒸散量的变化，农田全年蒸散量700 mm左右，蒸发量占年蒸散量的43%左右，其中冬小麦季蒸发量为161 mm，夏玉米季蒸发量为146 mm，均占各季蒸散量的43%左右。夏玉米由于是C4作物其蒸腾效率最高可达4.29 gC / kgH2O比冬小麦高。该研究明确农田水汽稳定同位素特征变化规律，阐明耗水结构的动态变化过程，揭示农田群体蒸腾效率变化规律，深入认识陆面-大气系统水分转化与生态系统生产力之间的关系，为土壤水分有效利用提供诊断基础，为农业水科学管理提供了依据。