Teng Dexiong, He Xuemin, Wang Jingzhe, Wang Jinlong, Lv Guanghui
College of Resources and Environment Science, Xinjiang University, Urumqi, Xinjiang, China.
Key Laboratory of Oasis Ecology of Education Ministry, Xinjiang University, Urumqi, Xinjiang, China.
PeerJ. 2020 Feb 10;8:e8530. doi: 10.7717/peerj.8530. eCollection 2020.
In most eddy covariance (EC) studies, carbon flux measurements have a high defect rate for a variety of reasons. Obtaining the annual sum of carbon dioxide exchange requires imputation of data gaps with high precision and accuracy. This study used five methods to fill the gaps in carbon flux data and estimate the total annual carbon dioxide exchange of the Tugai forest in the arid desert ecosystem of Ebinur Lake Basin, Northwest China. The Monte Carlo method was used to estimate the random error and bias caused by gap filling. The results revealed that (1) there was a seasonal difference in the friction velocity threshold of nighttime flux, with values in the growing season and non-growing season of 0.12 and 0.10 m/s, respectively; (2) the five gap-filling methods explained 77-84% of the data variability in the fluxes, and the random errors estimated by these methods were characterized by non-normality and leptokurtic heavy tail features, following the Laplacian (or double-exponential) distribution; (3) estimates of the annual sum of carbon dioxide exchange using the five methods at the study site in 2015 ranged from -178.25 to -155.21 g C m year, indicating that the Tugai forest in the Ebinur Lake Basin is a net carbon sink. The standard deviation of the total annual carbon dioxide exchange sums estimated by the five different methods ranged from 3.15 to 19.08 g C m year, with bias errors ranging from -13.69 to 14.05 g C m year. This study provides a theoretical basis for the carbon dioxide exchange and carbon source/sink assessment of the Tugai forest in an arid desert ecosystem. In order to explore the functioning of the Tugai forest at this site, a greater understanding of the underlying ecological mechanisms is necessary.
在大多数涡度相关（EC）研究中，由于各种原因，碳通量测量存在较高的缺失率。获取二氧化碳交换的年度总和需要高精度和准确性地插补数据缺口。本研究采用五种方法填补碳通量数据缺口，并估算中国西北艾比湖流域干旱荒漠生态系统中胡杨树林的年度二氧化碳总交换量。使用蒙特卡罗方法估算缺口填补引起的随机误差和偏差。结果表明：（1）夜间通量的摩擦速度阈值存在季节差异，生长季和非生长季的值分别为0.12和0.10 m/s；（2）五种缺口填补方法解释了通量数据变异性的77 - 84%，这些方法估算的随机误差具有非正态性和拉普拉斯（或双指数）分布的尖峰厚尾特征；（3）2015年在研究地点使用这五种方法估算的二氧化碳交换年度总和范围为-178.25至-155.21 g C m² year⁻¹，表明艾比湖流域的胡杨树林是一个净碳汇。五种不同方法估算的年度二氧化碳总交换量总和的标准差范围为3.15至19.08 g C m² year⁻¹，偏差误差范围为-13.69至14.05 g C m² year⁻¹。本研究为干旱荒漠生态系统中胡杨树林的二氧化碳交换和碳源/汇评估提供了理论依据。为了探究该地点胡杨树林的功能，有必要更深入地了解其潜在的生态机制。
