Aquatic DOC export from subarctic Atlantic blanket bog in Norway is controlled by seasalt deposition, temperature and precipitation

Heleen A De Wit,José L J Ledesma,Martyn N Futter

doi:10.1007/s10533-016-0182-z

Abstract

Comprehensive and credible peatland carbon budgets, needed for global carbon accounting, must include lateral aquatic organic carbon export. Here, we quantify aquatic dissolved organic carbon (DOC) export for an Atlantic bog in subarctic Norway, the Andoya peatland, and test for sensitivity to climatic drivers. Hydrology, DOC concentrations and DOC export were simulated for 2000–2013 using the process-based catchment model Integrated Catchments model for Carbon (INCA-C), calibrated to site-specific water chemistry and hydrology (2011–2014) using readily-available data on temperature, precipitation and seasalt deposition. Measured streamwater DOC declined under seasalt episodes and was strongly positively related to temperature. Model calibrations successfully reproduced the water balance, variation in runoff (R2 = 0.67; Nash–Sutcliffe model efficiency NS = 0.67) and DOC concentrations (R2 = 0.85; NS = 0.84). The most sensitive model parameters related to temperature-sensitivity of DOC production and DOC (de)sorption sensitivity to seasalts. Model uncertainty related to parameter space was similar to interannual variation in DOC export. Mean annual modelled DOC export was 7.2 ± 0.7 g C m−2 year−1, roughly 35 % of the net land–atmospheric CO2 exchange at Andoya from 2009 to 2012 (estimated elsewhere). Current and antecedent mean temperature and precipitation were strong drivers of seasonal modelled DOC export, implying that warmer and wetter summers will lead to more DOC export. Evaluation of similar climate impacts on net peatland carbon accumulation requires additional exploration of the climate-sensitivity of land–atmosphere fluxes of CO2 and methane. Process-based models are valuable tools to account for lateral DOC exports in carbon balances of northern peatlands, especially where long-term monitoring data are lacking.

Highlights

IntroductionAquatic carbon fluxes are an important part of both boreal (de Wit et al 2015) and global carbon cycles (Cole et al 2007)
Aquatic carbon fluxes are an important part of both boreal and global carbon cycles (Cole et al 2007)
Aquatic export of dissolved organic carbon (DOC) in peat-dominated catchments is usually strongly promoted by precipitation (Olefeldt et al 2013), similar to what we found in the statistical analysis of catchment DOC export, but in Table 6 the highest absolute DOC export is found in Scotland, which is not the site with the highest annual precipitation

Summary

Introduction

Aquatic carbon fluxes are an important part of both boreal (de Wit et al 2015) and global carbon cycles (Cole et al 2007). Ecosystem carbon accumulation may be considerably overestimated when components of the net ecosystem carbon balance (NECB; Chapin et al 2006) are not accounted for, including lateral aquatic export of dissolved organic carbon (DOC) and particulate organic carbon, dissolved inorganic carbon (DIC and CO2) and methane fluxes (Nilsson et al 2008; Olefeldt et al 2012; Randerson et al 2002; Roulet et al 2007; Yu 2012) This is especially important in northern peatlands, which are among the largest terrestrial carbon stores (Gorham 1991; Yu 2012). Because climate is a major control of aquatic carbon export in peatland-dominated catchments (Holden 2005), a better understanding of the interactions between temperature and precipitation on all components of peatland carbon balances is needed for a more robust quantification of the fate of peatland carbon stores under a future climate

Methods

Results

Conclusion