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Almost 50 years of monitoring shows that climate, not forestry, controls long‐term organic carbon fluxes in a large boreal watershed
Author(s) -
Lepistö Ahti,
Futter Martyn N,
Kortelainen Pirkko
Publication year - 2014
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/gcb.12491
Subject(s) - environmental science , hydrology (agriculture) , watershed , surface runoff , total organic carbon , boreal , soil carbon , climate change , precipitation , taiga , land use , ecosystem , soil water , soil science , forestry , ecology , geography , geology , geotechnical engineering , machine learning , computer science , meteorology , biology
Here, we use a unique long‐term data set on total organic carbon ( TOC ) fluxes, its climatic drivers and effects of land management from a large boreal watershed in northern Finland. TOC and runoff have been monitored at several sites in the Simojoki watershed (3160 km 2 ) since the early 1960s. Annual TOC fluxes have increased significantly together with increased inter‐annual variability. Acid deposition in the area has been low and has not significantly influenced losses of TOC . Forest management, including ditching and clear felling, had a minor influence on TOC fluxes – seasonal and long‐term patterns in TOC were controlled primarily by changes in soil frost, seasonal precipitation, drought, and runoff. Deeper soil frost led to lower spring TOC concentrations in the river. Summer TOC concentrations were positively correlated with precipitation and soil moisture not temperature. There is some indication that drought conditions led to elevated TOC concentrations and fluxes in subsequent years (1998–2000). A sensitivity analysis of the INCA ‐C model results showed the importance of landscape position, land‐use type, and soil temperature as controls of modeled TOC concentrations. Model predictions were not sensitive to forest management. Our results are contradictory to some earlier plot‐scale and small catchment studies that have shown more profound forest management impacts on TOC fluxes. This shows the importance of scale when assessing the mechanisms controlling TOC fluxes and concentrations. The results highlight the value of long‐term multiple data sets to better understand ecosystem response to land management, climate change and extremes in northern ecosystems.