Carbon respiration from subsurface peat accelerated by climate warming in the subarctic

TY - JOUR

T1 - Carbon respiration from subsurface peat accelerated by climate warming in the subarctic

AU - Dorrepaal, Ellen

AU - Toet, Sylvia

AU - van Logtestijn, Richard S. P.

AU - Swart, Elferra

AU - van de Weg, Martine J.

AU - Callaghan, Terry V.

AU - Aerts, Rien

PY - 2009/7/30

Y1 - 2009/7/30

N2 - Among the largest uncertainties in current projections of future climate is the feedback between the terrestrial carbon cycle and climate(1). Northern peatlands contain one-third of the world's soil organic carbon, equivalent to more than half the amount of carbon in the atmosphere(2). Climate-warming-induced acceleration of carbon dioxide (CO2) emissions through enhanced respiration of thick peat deposits, centuries to millennia old, may form a strong positive carbon cycle-climate feedback. The long-term temperature sensitivity of carbon in peatlands, especially at depth, remains uncertain, however, because of the short duration or correlative nature of field studies(3-5) and the disturbance associated with respiration measurements below the surface in situ or during laboratory incubations(6,7). Here we combine non-disturbing in situ measurements of CO2 respiration rates and isotopic (C-13) composition of respired CO2 in two whole-ecosystem climate-manipulation experiments in a subarctic peatland. We show that approximately 1 degrees C warming accelerated total ecosystem respiration rates on average by 60% in spring and by 52% in summer and that this effect was sustained for at least eight years. While warming stimulated both short-term (plant-related) and longer-term (peat soil-related) carbon respiration processes, we find that at least 69% of the increase in respiration rate originated from carbon in peat towards the bottom (25-50 cm) of the active layer above the permafrost. Climate warming therefore accelerates respiration of the extensive, subsurface carbon reservoirs in peatlands to a much larger extent than was previously thought(6,7). Assuming that our data from a single site are indicative of the direct response to warming of northern peatland soils on a global scale, we estimate that climate warming of about 1 degrees C over the next few decades could induce a global increase in heterotrophic respiration of 38-100 megatonnes of C per year. Our findings suggest a large, long-lasting, positive feedback of carbon stored in northern peatlands to the global climate system.

AB - Among the largest uncertainties in current projections of future climate is the feedback between the terrestrial carbon cycle and climate(1). Northern peatlands contain one-third of the world's soil organic carbon, equivalent to more than half the amount of carbon in the atmosphere(2). Climate-warming-induced acceleration of carbon dioxide (CO2) emissions through enhanced respiration of thick peat deposits, centuries to millennia old, may form a strong positive carbon cycle-climate feedback. The long-term temperature sensitivity of carbon in peatlands, especially at depth, remains uncertain, however, because of the short duration or correlative nature of field studies(3-5) and the disturbance associated with respiration measurements below the surface in situ or during laboratory incubations(6,7). Here we combine non-disturbing in situ measurements of CO2 respiration rates and isotopic (C-13) composition of respired CO2 in two whole-ecosystem climate-manipulation experiments in a subarctic peatland. We show that approximately 1 degrees C warming accelerated total ecosystem respiration rates on average by 60% in spring and by 52% in summer and that this effect was sustained for at least eight years. While warming stimulated both short-term (plant-related) and longer-term (peat soil-related) carbon respiration processes, we find that at least 69% of the increase in respiration rate originated from carbon in peat towards the bottom (25-50 cm) of the active layer above the permafrost. Climate warming therefore accelerates respiration of the extensive, subsurface carbon reservoirs in peatlands to a much larger extent than was previously thought(6,7). Assuming that our data from a single site are indicative of the direct response to warming of northern peatland soils on a global scale, we estimate that climate warming of about 1 degrees C over the next few decades could induce a global increase in heterotrophic respiration of 38-100 megatonnes of C per year. Our findings suggest a large, long-lasting, positive feedback of carbon stored in northern peatlands to the global climate system.

KW - SOIL CO2 EFFLUX

KW - WATER-TABLE

KW - TEMPERATURE SENSITIVITY

KW - NATURAL-ABUNDANCE

KW - ECOSYSTEM

KW - BOG

KW - DECOMPOSITION

KW - GROWTH

KW - CYCLE

KW - MINERALIZATION

UR - http://www.scopus.com/inward/record.url?scp=68149181762&partnerID=8YFLogxK

U2 - 10.1038/nature08216

DO - 10.1038/nature08216

M3 - Article

SN - 0028-0836

VL - 460

SP - 616

EP - 619

JO - Nature

JF - Nature

IS - 7255

ER -