Abstract
Understanding the spatio-temporal variability of controls on peatland carbon (C) cycling is essential to project the effects of future environmental change. While there is understanding of individual drivers of C cycling, the effect of multiple drivers, including interactions, remains poorly understood. Using a spatially and temporally explicit sampling framework, we examined the effects of biotic and abiotic controls on key indicators of peatland functioning: ecosystem respiration (Reco), photosynthesis (Pcal), net ecosystem exchange (NEE), methane (CH4) fluxes, and pore water dissolved organic carbon concentration ([DOC]). Measurements were made over 12 months in a blanket peatland hosting a wind farm in Scotland, UK. Overall, we found that (i) season and plant functional type (PFT) explained most variation in Reco and Pcal, (ii) PFT and spatial location within the wind farm, which integrates several peat properties, were dominant predictors of CH4 fluxes, and (iii) season and location within the wind farm correlated with pore water [DOC]. Examination of predictors indicated that interactions, between and within biotic and abiotic factors, explained a significant amount of variation in greenhouse gas fluxes and [DOC]. These findings indicate that combinations of biotic and abiotic factors could mediate or exacerbate the effects of future environmental change on peatland C cycling. Given this, studies of C cycling need to capture the spatial and temporal variance of biotic and abiotic factors and their interactions to project the likely impacts of environmental change.
Highlights
Peat soils are globally important carbon (C) stores, with approximately one-quarter of the world soil C1396 A
We hypothesized that (1) plant functional type (PFT) explains more of the variation in ecosystem CO2 and CH4 fluxes and [DOC] than spatial variation ‘site’; and (2) interactions, both between and within biotic and abiotic factors, explain a significant proportion of the variance in greenhouse gases (GHG) fluxes and [DOC] in northern peatlands
We describe our results in relation to our hypotheses that (1) PFT explains more of the variation in ecosystem CO2 and CH4 fluxes and [DOC] than the integrated effect of properties that vary with location on the peatland and (2) interactions, both between and within biotic and abiotic factors, explain a significant amount of the variance in GHG fluxes and [DOC] in northern peatlands
Summary
Peat soils are globally important carbon (C) stores, with approximately one-quarter of the world soil C1396 A. Armstrong and others through decomposition of organic matter, plant respiration, and the oxidation of CH4 (positive fluxes, together hereafter termed ecosystem respiration) and taken up through photosynthesis (negative fluxes). CH4 is produced during anaerobic decomposition but can be oxidized into CO2 by methanotrophs. DOC can be produced under aerobic and anaerobic conditions and exported from peatlands by drainage channels, and acts as a substrate for microbes, with CO2 efflux from streams comprising an important component of the overall C balance (Billett and Harvey 2013). The pore water [DOC] values give an indication of both potential DOC runoff [ discharge is known to dominate fluxes (Armstrong and others 2010)], and substrate available for microbial decomposition which may feed back to GHG fluxes
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