Yan Yujie, Zhou Li, Zhou Guangsheng, Wang Yu, Song Jiaxin, Zhang Sen, Zhou Mengzi
School of Geo-Science and Technology, Zhengzhou University, Zhengzhou, China.
State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing, China.
Front Plant Sci. 2023 Jan 25;14:1119670. doi: 10.3389/fpls.2023.1119670. eCollection 2023.
Boreal forests, the second continental biome on Earth, are known for their massive carbon storage capacity and important role in the global carbon cycle. Comprehending the temporal dynamics and controlling factors of net ecosystem CO exchange (NEE) is critical for predicting how the carbon exchange in boreal forests will change in response to climate change. Therefore, based on long-term eddy covariance observations from 2008 to 2018, we evaluated the diurnal, seasonal, and interannual variations in the boreal forest ecosystem NEE in Northeast China and explored its environmental regulation. It was found that the boreal forest was a minor CO sink with an annual average NEE of -64.01 (± 24.23) g CO m yr. The diurnal variation in the NEE of boreal forest during the growing season was considerably larger than that during the non-growing season, and carbon uptake peaked between 8:30 and 9:30 in the morning. The seasonal variation in NEE demonstrated a "U" shaped curve, and the carbon uptake peaked in July. On a half-hourly scale, photosynthetically active radiation and vapor pressure deficit had larger impacts on daytime NEE during the growing season. However, temperature had major control on NEE during the growing season at night and during the non-growing season. On a daily scale, temperature was the dominant factor controlling seasonal variation in NEE. Occurrence of extreme temperature days, especially extreme temperature events, would reduce boreal forest carbon uptake; interannual variation in NEE was substantially associated with the maximum CO uptake rate during the growing season. This study deepens our understanding of environmental controls on NEE at multiple timescales and provides a data basis for evaluating the global carbon budget.
北方森林是地球上第二大陆地生物群落，以其巨大的碳储存能力和在全球碳循环中的重要作用而闻名。了解生态系统净CO2交换（NEE）的时间动态和控制因素对于预测北方森林中的碳交换将如何响应气候变化而变化至关重要。因此，基于2008年至2018年的长期涡度协方差观测数据，我们评估了中国东北北方森林生态系统NEE的日变化、季节变化和年际变化，并探讨了其环境调控机制。结果发现，北方森林是一个较小的CO2汇，年平均NEE为-64.01（±24.23）g CO2 m-2 yr-1。生长季北方森林NEE的日变化明显大于非生长季，碳吸收在上午8:30至9:30达到峰值。NEE的季节变化呈“U”形曲线，碳吸收在7月达到峰值。在半小时尺度上，生长季光合有效辐射和水汽压差对白天NEE的影响较大。然而，在生长季夜间和非生长季，温度对NEE起主要控制作用。在日尺度上，温度是控制NEE季节变化的主导因素。极端温度日的出现，尤其是极端温度事件，会减少北方森林的碳吸收；NEE的年际变化与生长季最大CO2吸收速率密切相关。本研究加深了我们对多时间尺度上NEE环境控制的理解，并为评估全球碳预算提供了数据基础。
