A pulse-labeling experiment to determine the contribution of recent plant photosynthates to net methane emission in arctic wet sedge tundra

We conducted a C-14 pulse-labeling experiment under field conditions to estimate the contribution of recent photosynthates to methane (CH4) emission in arctic wet sedge tundra dominated by Carex aquatilis and Eriophorum angustifolium. The average CH4 emission rate from plant-soil mesocosms in this study was 0.45 g C m(-2) d(-1). Carbon assimilated by plants via photosynthesis during pulse-labeling turned over rapidly and appeared as emitted CH4 within 24 h. Integration of flux measurements made over a 2-week period shows that the contribution of recent photosynthates to mid-season CH4 emission is relatively low. Less than 1% of the C-14-labeled carbon dioxide taken up through photosynthesis was emitted as (CH4)-C-14 during this study. (C) 2002 Elsevier Science Ltd. All rights reserved.