Plant functional group identity influences short‐term peatland ecosystem carbon flux: evidence from a plant removal experiment

Abstract

1. Northern hemisphere peatlands are globally important stores of organic soil carbon. We examined effects of plant functional group identity on short-term carbon (C) flux in an ombrotrophic peatland in northern England, UK, by selectively removing one of each of the three dominant plant functional groups (ericoid dwarf-shrubs, graminoids and bryophytes). Carbon dynamics were quantified by a combination of CO(2) flux measurements and (13)CO(2) stable isotope pulse labelling approaches. 2. Significant effects of plant functional group removals on CO(2) fluxes and tracer (13)C uptake and turnover were detected. Removal of ericoid dwarf- shrubs had the greatest influence on gross CO(2) flux, increasing rates of respiration and photosynthesis by > 200% relative to the undisturbed control. After pulse labelling with (13)CO(2), we found that turnover of recent photosynthate, measured as respired (13)CO(2) was also greatest in the absence of dwarf- shrubs. 3. Analysis of (13)C tracer enrichment in leaf tissues from all plant removal treatments showed that the rate of fixation of (13)CO(2) and turnover of (13)C labelled photosynthate in leaf tissue was greatest in graminoids and lowest in bryophytes. Furthermore, graminoid leaf (13)C enrichment was greatest when growing in the absence of dwarf-shrubs, suggesting that the presence of dwarf- shrubs reduced the photosynthetic activity of graminoids. 4. We conclude that plant functional groups differentially influence the uptake and short-term flux of carbon in peatlands, suggesting that changes in the functional composition of vegetation resulting from global change have the potential to alter short-term patterns of carbon exchange in peatland.