Extreme temperature events reduced carbon uptake of a boreal forest ecosystem in Northeast China: Evidence from an 11-year eddy covariance observation

Abstract

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 CO2 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 CO2 sink with an annual average NEE of -64.01 (± 24.23) g CO2 m-2 yr-1. 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 CO2 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.

Hydrometeorological controls on net carbon dioxide exchange over a temperate desert steppe in Inner Mongolia, China

“…It is generally agreed that in most ecosystems, radiation acts as the main regulating factor for NEE on a half-hourly scale (Baldocchi, 2014;Wang et al, 2019;Yan et al, 2023). However, certain studies have suggested that the two most important factors controlling carbon exchange in grassland ecosystems are temperature and water (Kim and Verma, 1990;Xue et al, 2014).…”

The Response of Daily Carbon Dioxide and Water Vapor Fluxes to Temperature and Precipitation Extremes in Temperate and Boreal Forests

“…The temperature effect on NEE and LE fluxes during the warm season did not differ significantly between boreal and temperate forests, with similar controlling mechanisms involved. Under positive temperature anomalies, it may be determined by suppressed assimilation processes due to high temperature and insufficient soil moisture [70][71][72], as well as a higher decomposition rate of soil organic matter and higher autotrophic respiration [21]. Under negative temperature anomalies, it may be caused by a large reduction in GPP at lower temperatures [73].…”

Long-term investigation of methane and carbon dioxide emissions in two Italian landfills

“…The above-mentioned limitations could be overcome using eddy covariance (EC). This technique, largely used in atmospheric and environmental science to determine trace gases exchanges over anthropic and natural ecosystems including urban areas [ 15 , 16 ], agricultural systems [ [17] , [18] , [19] ], grasslands [ 20 , 21 ], and forests [ 22 , 23 ], can provide continuous and automated measurements over long periods. Also, EC does not affect in depth and surface soil conditions, thus reducing uncertainties in the fluxes measured from landfill.…”