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	Unravelling the spatiotemporal variation of pCO(2) in low order streams: Linkages to land use and stream order
	Gu, Shijie1,2,3; Xu, Y. Jun4,5; Li, Siyue6
	2022-05-10
摘要	Headwater streams make the majority of cumulative stream length in a river basin, carbon dioxide (CO2) emission from headwater (low order) streams is thus an essential component. Anthropogenic activities in headwater areas such as land use change and land use practices can strongly modify terrestrial carbon and nutrient input, which could affect the level of partial pressure of dissolved carbon dioxide (pCO(2)) and CO2 degassing from streams. However, there are large uncertainties in estimates due to the lack of data in subtropical rivers of rapidly developing rural regions. The spatiotemporal variation and driving factors of the pCO(2) and CO2 degassing from low-order streams remain to be explored. In this study, we assess multi-spatial scale effects of land use on pCO(2) dynamics in seven headwater tributary rivers in Central China during 2016, 2017 and 2018 in rainy and dry seasons. Our results reveal that the stream pCO(2) level consistently increases as the stream order increases from 1 to 3 under apparent seasonal variations. Riverine pCO(2) is positively related to the percentage of urban land and cropland surrounding the river segments, but is negatively related to the percentage of forest land. The stream pCO(2) is more closely correlated with the 1000 and 2000 m diameters of circular buffers at upstream sampling sites than the circular buffers with 100 and 500 m diameters. There exist significant relationships of pCO(2) with the concentrations of TN, TP, DO, and DOC in the low-order streams. The partial redundancy analysis quantifies the relative importance of anthropogenic land uses, natural factors and water chemical variables in mediating stream pCO(2), showing that influences of anthropogenic land uses (urban and cropland) on pCO(2) decrease, with a percentage role of 34%, 14%, and 4% in the 1st-, 2nd- and 3rd-order streams, respectively. The impact of nutrients on pCO(2), however, increases as the stream order increases. Urban influence on stream pCO(2) also decreases as stream order increases. Our study highlights the effect of land use/land cover types and stream order on riverine pCO(2) and provides new insight into estimating CO2 emission in headwater streams. Future studies are needed on the linkage between riverine CO2 degassing and stream orders under changing land use conditions.
关键词	Riverine pCO(2) Low order streams CO2 emission Land use/land cover Han River Yangtze River
DOI	10.1016/j.scitotenv.2022.153226
发表期刊	SCIENCE OF THE TOTAL ENVIRONMENT
ISSN	0048-9697
卷号	820页码:10
通讯作者	Li, Siyue(syli2006@163.com)
收录类别	SCI
WOS记录号	WOS:000766807000014
语种	英语