Interannual Variations of Water and Carbon Dioxide Fluxes over a Semiarid Alpine Steppe on the Tibetan Plateau

IF 2.1 4区 地球科学 Q3 METEOROLOGY & ATMOSPHERIC SCIENCES
Yang Liu, Huizhi Liu, Feng Li, Qun Du, Lujun Xu, Yaohui Li
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Abstract

Water and carbon exchanges between grassland and the atmosphere are important processes for water balance and carbon balance. Based on eddy covariance observations over a semiarid alpine steppe ecosystem in Bange on the Tibetan Plateau during the growing season from 2014 to 2017, the variations in evapotranspiration (ET), net ecosystem exchange (NEE), and their components and the associated driving factors were analyzed. Linear and nonlinear models were applied to investigate the relationships between fluxes and their controlling factors over different timescales. The results show that the average ET for the growing season ranged from 1.1 to 2.4 mm/d with an average of 2.0 mm/d for the four consecutive years. Drought conditions reduced the surface conductance and hence the Priestley–Taylor coefficient. Mean T/ET was low (0.34) due to low vegetation cover. Plant growth increased the T/ET ratio during the growing season, whereas soil water content (SWC) explained most of the variation of ET and E on daily and monthly scales. The Enhanced Vegetation Index (EVI) was the most important controlling factor for temperature. Transpiration increased with SWC in dry conditions. For the growing season in 2014, 2016, and 2017, Bange was a carbon sink, while it was a carbon source in 2015. The largest CO2 flux was higher and the temperature sensitivity coefficient (Q10) was lower for 2015 than for the other three years. SWC affected these photosynthesis and respiration parameters. The ratio of respiration (Re) to gross primary production (GPP) was the highest during the 2015 growing season. Both on daily and monthly scales, Re was positively and linearly correlated with GPP. The most important controlling factor for the CO2 flux was EVI on daily and monthly scales.
青藏高原半干旱高寒草原水和二氧化碳通量的年际变化
草原与大气之间的水碳交换是水平衡和碳平衡的重要过程。基于2014-2017年青藏高原班戈半干旱高寒草原生态系统生长季节的涡度协方差观测,分析了蒸散量(ET)、净生态系统交换量(NEE)及其组成和相关驱动因素的变化。应用线性和非线性模型研究了不同时间尺度上通量及其控制因素之间的关系。结果表明,生长季节的平均ET在1.1到2.4之间 mm/d,平均2.0 mm/d连续四年。干旱条件降低了表面电导,从而降低了Priestley–Taylor系数。由于植被覆盖率低,平均T/ET较低(0.34)。植物生长增加了生长季节的T/ET比,而土壤含水量(SWC)解释了ET和E在日尺度和月尺度上的大部分变化。植被指数(EVI)是影响气温的最重要的控制因子。在干燥条件下,随着SWC的增加,蒸腾作用增加。在2014年、2016年和2017年的生长季节,班戈是一个碳汇,而在2015年它是一个碳源。与其他三年相比,2015年的最大CO2通量更高,温度敏感系数(Q10)更低。SWC影响这些光合作用和呼吸参数。呼吸(Re)与初级生产总值(GPP)的比率在2015年生长季节最高。无论是在日尺度还是月尺度上,Re都与GPP呈正相关。对CO2通量最重要的控制因素是日尺度和月尺度上的EVI。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Advances in Meteorology
Advances in Meteorology 地学天文-气象与大气科学
CiteScore
5.30
自引率
3.40%
发文量
80
审稿时长
>12 weeks
期刊介绍: Advances in Meteorology is a peer-reviewed, Open Access journal that publishes original research articles as well as review articles in all areas of meteorology and climatology. Topics covered include, but are not limited to, forecasting techniques and applications, meteorological modeling, data analysis, atmospheric chemistry and physics, climate change, satellite meteorology, marine meteorology, and forest meteorology.
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