基于光合参数对水氮响应机理的东北春玉米冠层碳通量模型改进研究

Maximum carboxylation rate is the most important photosynthetic physiological parameter in the process model of terrestrial carbon cycling. The influences of soil moisture and nitrogen content to its value are more complex. The study of the response mechanism of Vcmax to water stress and nitrogen addition is of great significance to reveal the carbon cycle of farmland ecosystem under the background of global change and human activities, and to accurately estimate and forecast carbon revenue and expenditure. This project takes the spring maize in Northeast China as the research object. Based on artificial drought and nitrogen fertilization, curve fitting method will be used to observe the photosynthetic parameters of spring maize in northeast China in important growth stages(jointing period and big trumpet period), and the effects of water stress, nitrogen addition and the co-processing on photosynthetic parameters will be studied. Based on above results, the canopy carbon flux model of maize agroecosystem will be improved. And the results will be analyzed by eddy covariance and soil observation. That provides a scientific basis for understanding the carbon cycle mechanism.

植物叶片最大羧化速率（maximum carboxylation rate，Vcmax）是陆地碳循环过程模型中重要的光合生理参数，其值受土壤水分和土壤氮含量的影响较为复杂。研究Vcmax对水分胁迫和氮添加的响应机制，对揭示全球变化和人类活动背景下农田生态系统碳循环规律、准确评估和预测碳收支具有重要意义。本项目拟以东北春玉米为研究对象，在人工干旱和施氮处理的基础上，采用曲线拟合法观测关键生育时期（拔节期、大喇叭口期）的光合参数，探索水分胁迫和氮添加及二者的协同处理对光合参数的影响规律，基于上述规律对玉米农田生态系统冠层碳通量模型进行改进，并利用玉米农田生态系统涡动相关和土壤观测结果进行检验，为准确理解农田碳循环机制提供科学基础。

本项目以东北春玉米为研究对象，在人工干旱和施氮处理的基础上，采用了曲线拟合法观测关键生育时期（拔节期、抽雄期、乳熟期）的光合参数，探索了水分胁迫和氮添加及二者的协同处理对光合参数的影响规律，基于上述规律对玉米农田生态系统冠层碳通量模型进行了改进，并利用玉米农田生态系统涡动相关和土壤观测结果进行了检验，结果表明：玉米叶片最大羧化速率（maximum carboxylation rate，Vcmax）随玉米的生长，逐渐增大，拔节期达到最大（最大值分别为67.8和74.0μmol m-2 s-1），之后减小。随着施氮量的增加，Vcmax先增加，一定程度后降低。施氮量为240kg/hm2时光合参数的值最大。干旱胁迫导致光合参数明显降低；随着干旱程度增加，光合参数受影响程度增加。施氮后对中度干旱胁迫有所缓解。不同发育期干旱，乳熟影响大于抽雄；复水后Vcmax随施氮量增加先增加后下降。改进后的模型模拟效果较好，模拟精度提高了3.8%。2020年生长季碳通量30 min模拟值与实测值相关系数分别为0.801，就总平均值来说，多层模型对Fc低估了约1.6%。模型能够较好的模拟碳通量日、季节变化，其中白天拟合效果好于夜间；生长季旺盛期好于初期。轻度、中度、重度干旱条件下玉米生长季冠层碳通量30 min值较常年分别降低19.4%、39.3%和73.4%。研究结果对揭示全球变化和人类活动背景下农田生态系统碳循环规律、准确评估和预测碳收支具有重要意义。