CAJ | 학술논문

陆地生态系统CO_2和水热通量变化特征及其环境控制机制是理解生态系统水碳耦合循环过程和模型开发的基础.农田生态系统水碳通量特征的研究对把握作物生产力水平和水分利用效率的高低具有重要意义.本研究基于涡度相关技术对华北平原冬小麦农田生态系统齐穗期水碳通量的日变化特征进行了分析.结果表明:以C_3作物冬小麦构成的农田生态系统晴天CO_2通量、水汽通量和冠层导度均存在明显的"午休"现象,"午休"的原因是晴天强光造成的"光抑制";CO_2通量对光合有效辐射呈米氏响应,其表观量子效率为0.002 997 mg/μmol,潜在最大碳通量为3.349 4 mg/(m~2·s);水汽通量和冠层导度与光合有效辐射之间均存在极显著线性关系,但在相同光合有效辐射下,下午的冠层导度明显小于上午,其原因在于同化产物的反馈抑制;下午的水汽通量明显大于上午,则主要受控于温度和VPD的变化.由于下午的水汽通量大于上午,而CO_2通量在上午和下午无明显差异,使得农田生态系统上午的水分利用效率明显高于下午.
륙지생태계통CO_2화수열통량변화특정급기배경공제궤제시리해생태계통수탄우합순배과정화모형개발적기출.농전생태계통수탄통량특정적연구대파악작물생산력수평화수분이용효솔적고저구유중요의의.본연구기우와도상관기술대화북평원동소맥농전생태계통제수기수탄통량적일변화특정진행료분석.결과표명:이C_3작물동소맥구성적농전생태계통청천CO_2통량、수기통량화관층도도균존재명현적"오휴"현상,"오휴"적원인시청천강광조성적"광억제";CO_2통량대광합유효복사정미씨향응,기표관양자효솔위0.002 997 mg/μmol,잠재최대탄통량위3.349 4 mg/(m~2·s);수기통량화관층도도여광합유효복사지간균존재겁현저선성관계,단재상동광합유효복사하,하오적관층도도명현소우상오,기원인재우동화산물적반궤억제;하오적수기통량명현대우상오,칙주요수공우온도화VPD적변화.유우하오적수기통량대우상오,이CO_2통량재상오화하오무명현차이,사득농전생태계통상오적수분이용효솔명현고우하오.
Characteristics of CO_2,water and heat fluxes of terrestrial ecosystems and related mechanisms involved provide insights into the coupling cycle of water and carbon and the model development.It's necessary to investigate the characteristics of water and carbon fluxes for understanding the crop productivity and water use efficiency. In this study, we analyzed the diurnal changes of water and carbon fluxes at full heading time of winter-wheat in North China based on the eddy covariance technique. The results showed that there existed evident midday depression of CO_2, water vapor and canopy conductance under clear sky condition, as a result of photo-inhibition caused by strong radiation. The responses of CO_2 flux to photosynthetically active radiation could be expressed by Michaelis-Menten function, with apparent quantum yield 0.002 997 mg/fzmol photons and maximum potential of carbon flux 3.349 4 mg/(m~2·s) .The water vapor flux and canopy conductance were significantly correlated with photosynthetically active radiation.However,at the same light con-dition, canopy conductance in afternoon was apparently smaller than that in the morning due to the feedback restrain of photosynthate, whereas water vapor flux in afternoon was much larger than that in the morning, resulting from the changes of air temperature and vapor pressure deficit. Note that water use efficiency in the morning was higher than that in the af-ternoon , because water vapor flux in afternoon was much larger than that in the morning, while no obvious difference exited for CO_2 flux between the morning and afternoon.