Five‐Year Measurements of Net Ecosystem CO_2 Exchange at a Fen in the Zoige Peatlands on the Qinghai‐Tibetan Plateau

摘要

Little is known about the relationship between carbon sequestration and environment in some alpine peatland ecosystems, especially in remote areas such as the Qinghai‐Tibetan Plateau. In the present study, net ecosystem CO_2 exchange (NEE) flux was measured from 2013 to 2017 at the Riganqiao fen in the Zoige peatlands on the eastern Qinghai‐Tibetan Plateau using the eddy covariance technique. In the growing season, diurnal CO_2 uptake peaks occurred between 12:00 and 14:00, while emission peaks occurred between 21:00 and 22:00. Carbon uptake peak occurred mainly from June to July in the growing season, and the maximum daily net CO_2 uptake of -8.4 g C m~(-2) d~(-1) was observed in mid‐June 2016. The Riganqiao peatland was a net CO_2 sink, with uptake (g C m~(-2) yr~(-1)) of average ~(-1)71.4 ± 38.1 during the five years. Photosynthetically active radiation (PAR) and soil temperature (T_s) were significantly correlated with diurnal net CO_2 uptake. In growing seasons, PAR was significantly correlated with daytime CO_2 uptake, and T_s was a major determinant of ecosystem respiration during growing and nongrowing seasons, although the fitting functions differed between the two seasons. Rainfall influenced interannual variability of cumulative NEE and water table depth (WTD) and volumetric water content (VWC) were both significantly correlated with interannual NEE. Our results suggest that in the long term, peatland NEE is affected mainly by the water regime, which is influenced by soil temperature and water condition.