东北春玉米关键生育期蒸腾及干物质分配对干旱胁迫的响应及模拟研究

Transpiration and dry matter partition are two very sensitive processes of crop in response to drought stress. It is inevitable to induce large uncertainties when the current crop growth models with empirical and simplified parameterization schemes of the two processes are applied to simulate the response of crop to drought stress, which reduces necessarily availablity of the model to access effects of drought. To this project, based on the balance relationship between the canopy evapotranspiration and root water uptake and plant functional equilibrium theory, water stress experiment will be carried out and biological and environmental variables (including photosynthesis, transpiration, respiration, root distribution, biomass of every organ, radiation, soil water, canopy temperature etc) related to transpiration and dry matter partition as well as mechanisms of their responses to drought stress will be systematically observed and investigated by considering comprehensively principal processes of plant physiology and ecology. In addition, simulation scheme of transpiration process will be improved by optimizing crop coefficient and reduction factor for transpiration and introducing root water uptake scheme. At the same time, a mechanistic model of dry matter partition which is able to response dynamically to drought stress will be developed with data from experiments. Finally, WOFOST crop model will be improved by using the above mentioned parameterization schemes in order to simulate more effectively crop growing process under the condition of drought stress. This study will strengthen the understandings of the mechanism of farmland water consumption and the process of forming drought disasters and then will provide scientific basis for developing the technique of drought impact assessment for maize.

植物的蒸腾和干物质分配过程对干旱胁迫响应非常敏感。现有主流作物模型采用经验或简化方式对两个过程进行参数方案设置，不能准确模拟作物对水分胁迫的响应，降低了模型对干旱影响评估的适用性。本项目基于蒸腾耗水与根系吸水的平衡关系、植物功能平衡理论，拟针对东北春玉米关键生育期开展干旱胁迫试验，通过对蒸腾和干物质分配过程的相关生物（光合、蒸腾、呼吸、根分布和各器官生物量）和环境因子（辐射、土壤湿度、冠层温度等）进行系统观测，综合考虑主要生理生态过程，研究二者对干旱的响应机制；通过优化作物系数、潜在蒸散消减系数的参数方案，并引入根系吸水方案来改进蒸腾过程模拟方案，同时，利用实测资料发展能够对干旱动态响应的干物质分配机理模型。利用以上方案对WOFOST作物模型进行优化，以提高其对干旱胁迫条件下作物生长过程的模拟能力。本项目将为加强玉米农田耗水机制及干旱致灾过程的理解，发展玉米干旱影响评估技术提供科学依据。

研究内容：基于2018-2020年玉米盆栽和池栽和多年分期播种试验资料，开展干旱胁迫对春玉米关键生育期干物质积累(DMA)和分配(DMP)以及蒸腾过程的影响机制、干物质积累和分配参数方案构建及模拟、WOFOST作物模型蒸腾过程参数方案优化及模拟研究。.重要结果：1）揭示营养（VP）和生殖（RP)阶段蒸腾（Tr）的干旱响应机制：叶片Tr干旱响应快于光合速率(Pn)，Tr对干旱后复水的恢复能力小于Pn。植株Tr的主要影响因素是饱和水汽压差(VPD)和叶面积指数（LAI），VPD受气温和辐射影响，反映能量的作用。VP干旱时土壤湿度通过影响LAI间接影响Tr，以能量影响为主，RP干旱对Tr以水分影响为主。2）基于CoLM模型揭示根长密度（RLD）对根系吸水（RWU）分布的影响大于根生物量。引入真实RLD和决定累计吸水效率和分布的阈值参数优化了RWU方案，提高干旱年模型精度。3）揭示了轻旱促进叶、茎干物质向果实转移，重度干旱抑制该过程；高温和干旱协同作用对DMA的影响大于单独干旱，对DMP影响有限；VP干旱对叶影响小于茎，使根和叶干物质分配比例（DMPR）增大；复水使茎DMPR增大，收获指数（HI）减小。RP干旱对绿叶面积和叶干重的影响大于VP干旱，对茎干重的影响小于叶，使营养器官DMPR增大,HI减小。VP和RP干旱及复水都使根冠比增大。4）建立考虑相对干物重与相对积温的地上干物重Logistic模型。指出Friedlingstein模型对叶和根DMP的模拟能力较弱。发展了考虑干旱程度及生育进程的叶和茎DMP模型。5）确定了WOFOST模型重要发育参数，引入动态作物系数和penman-montieth公式对模型蒸腾过程优化，有效提高干旱状态下模型性能。.科学意义:增强对玉米蒸腾、干物质积累和分配干旱响应机制的理解，促进作物模型性能的改进，为准确评估干旱影响提供科学依据。