夏玉米农田生态系统土壤呼吸碳源效应对植株固碳的补偿机制

Under the background of global climate continues to changing, in view of the agricultural production practices need of decreasing carbon emissions and increasing crops production capacity, considering soil respiration and plant photosynthesis interaction mechanism, the key link to further reveal the adaptation mechanism of the carbon/carbon sinks in farmland ecosystem, under global climate change, also has important guiding significance for crops production practice. This project select a typical summer maize farmland ecosystem as the research object in North China Plain, adopting water, temperature, and carbon as the main control factors to develop indoor environment change control experiment, combining with the summer maize field and micro-plot experiment to study the effects of soil tillage and straw returning on summer corn farmland CO2 release, soil moisture and temperature. Simulation analysis the time sequence of soil respiration intensity of carbon release and the degree of response on water, temperature and carbon factors and plant photosynthesis. Using stable carbon isotope ratio mass spectrometry method , to explore the proportion of carbon soil respiration provides carbon source in the process of summer maize plants photosynthetic carbon sequestration, and the mechanism of effects on soil respiration carbon source in different population structure. Meanwhile, by building high carbon conversion efficiency group, exploring soil respiration carbon compensation effect of canopy carbon capture, obtaining high carbon conversion efficiency group structure, the relationship of soil respiration carbon emissions of carbon source and plant carbon of carbon sink helped be clarified. So as to explore the reasonable agricultural management measures of carbon source reduction and carbon sink increase in summer maize farmland ecosystem, providing theoretical foundation and scientific support for a comprehensive understanding and scientific evaluation of regional low carbon source and carbon sequestration effect and the establishing of high yield and low carbon cultivation techniques.

在全球气候持续变化背景下，针对农业生产切实需要解决的固碳减排和增加作物生产力等问题，考虑土壤呼吸CO2释放和植物光合作用固定CO2的互作机制，是探寻农田生态系统合理碳管理的关键环节。本项目以黄淮海平原典型夏玉米农田生态系统为研究对象，开展以水热碳为主控因子的室内控制试验，结合大田和微区试验，研究土壤耕作和秸秆还田对夏玉米农田CO2释放、土壤水分及温度等的影响，模拟分析土壤呼吸碳释放强度的时间顺序以及对水热碳因子和植株光合作用的响应程度；运用稳定碳同位素质谱方法，研究夏玉米各层次植株固碳过程中土壤呼吸提供碳源占总碳源的比例，探讨不同群体结构对土壤呼吸碳源效应的作用机理；构建高碳转化效率群体，探索土壤呼吸碳排放对冠层碳截获的补偿效应，阐明土壤呼吸碳排放的碳源效应和植株固碳碳汇效应的关系及其在产量形成中的作用机理。研究结果将为全面理解农田碳源碳汇效应及制定高产低碳栽培技术提供理论基础和技术支撑。

在全球气候持续变化背景下，本研究针对农业生产切实需要解决的固碳减排和增加作物生产力等问题，立足农田植株固碳与土壤表面CO2 释放的截获再利用机制，以黄淮海平原典型夏玉米农田生态系统为研究对象，以长期定位保护性耕作试验点农田为平台，研究了土壤耕作和秸秆还田对夏玉米农田CO2释放、土壤呼吸碳源效应在产量形成中的作用机理。主要研究结果如下：.1）室内土样培养实验模拟分析土壤表面CO2释放强度对水热碳因子的响应机制。空气湿度x1通过空气温度 x2 对土壤呼吸速率y的间接作用较大，其间接通径系数 r12×P2.y=0.215912；空气湿度x1和土壤温度x3共同对土壤呼吸速率y的相对决定程度为0.477， 决定系数最大，且x1对R2的总贡献为0.259464。免耕土壤微生物量碳在65%湿度培养后含量最高，深松土壤微生物量碳则随湿度的增加微生物量碳降低。.2）构建高碳转化效率群体，研究夏玉米群体在不同耕作措施和秸秆还田下的光合碳高效利用机制。深松可显著提高夏玉米生育后期功能叶的叶绿素含量、光合速率、气孔导度和蒸腾速率等光合性能，降低非气孔因素对光合作用的不利影响，还可以延长花后功能期，维持功能叶光合强度一直处于较高水平，并且提高夏玉米花后干物质积累量和对籽粒的贡献率，最终提高单季和周年产量。.3）运用稳定性碳同位素，分析阐明土壤呼吸碳排放的碳源效应和植株固碳碳汇效应的关系及其在产量形成中的作用机理：模拟方程表明，夏玉米开花期穗位叶光合的 20.17%是来源于土壤排放的 CO2。空气 CO2对穗位叶光合的影响是土壤释放 CO2的 3.96 倍。深松提高夏玉米的穗粒数和千粒重，从而提高产量，产量平均提高18.9%。.综上结果表明，碳源输入方式、水热因子以及耕作方式对土壤呼吸产生的CO2在进入大气之前被玉米冠层重新截获利用有着调控意义，深松调控表现为作物植株固碳的碳增效效应，从而为农田生态系统制定优化的碳调控技术与真正意义上的提高作物生产力和农田减排提供理论基础和技术支撑。