TY - JOUR

T1 - Soil carbon loss in warmed subarctic grasslands is rapid and restricted to topsoil

AU - Verbrigghe, Niel

AU - Leblans, Niki I. W.

AU - Sigurdsson, Bjarni D.

AU - Vicca, Sara

AU - Fang, Chao

AU - Fuchslueger, Lucia

AU - Soong, Jennifer L.

AU - Weedon, James T.

AU - Poeplau, Christopher

AU - Ariza-Carricondo, Cristina

AU - Bahn, Michael

AU - Guenet, Bertrand

AU - Gundersen, Per

AU - Gunnarsdóttir, Gunnhildur E.

AU - Kätterer, Thomas

AU - Liu, Zhanfeng

AU - Maljanen, Marja

AU - Marañón-Jiménez, Sara

AU - Meeran, Kathiravan

AU - Oddsdóttir, Edda S.

AU - Ostonen, Ivika

AU - Peñuelas, Josep

AU - Richter, Andreas

AU - Sardans, Jordi

AU - Sigurðsson, Páll

AU - Torn, Margaret S.

AU - Van Bodegom, Peter M.

AU - Verbruggen, Erik

AU - Walker, Tom W. N.

AU - Wallander, Håkan

AU - Janssens, Ivan A.

PY - 2022

Y1 - 2022

N2 - Global warming may lead to carbon transfers from soils to the atmosphere, yet this positive feedback to the climate system remains highly uncertain, especially in subsoils (Ilyina and Friedlingstein, 2016; Shi et al., 2018). Using natural geothermal soil warming gradients of up to +6.4 degrees C in subarctic grasslands (Sigurdsson et al., 2016), we show that soil organic carbon (SOC) stocks decline strongly and linearly with warming (-2.8 t ha(-1) degrees C-1). Comparison of SOC stock changes following medium-term (5 and 10 years) and long-term (> 50 years) warming revealed that all SOC stock reduction occurred within the first 5 years of warming, after which continued warming no longer reduced SOC stocks. This rapid equilibration of SOC observed in Andosol suggests a critical role for ecosystem adaptations to warming and could imply short-lived soil carbon-climate feedbacks. Our data further revealed that the soil C loss occurred in all aggregate size fractions and that SOC stock reduction was only visible in topsoil (0-10 cm). SOC stocks in subsoil (10-30 cm), where plant roots were absent, showed apparent conservation after > 50 years of warming. The observed depth-dependent warming responses indicate that explicit vertical resolution is a prerequisite for global models to accurately project future SOC stocks for this soil type and should be investigated for soils with other mineralogies.

AB - Global warming may lead to carbon transfers from soils to the atmosphere, yet this positive feedback to the climate system remains highly uncertain, especially in subsoils (Ilyina and Friedlingstein, 2016; Shi et al., 2018). Using natural geothermal soil warming gradients of up to +6.4 degrees C in subarctic grasslands (Sigurdsson et al., 2016), we show that soil organic carbon (SOC) stocks decline strongly and linearly with warming (-2.8 t ha(-1) degrees C-1). Comparison of SOC stock changes following medium-term (5 and 10 years) and long-term (> 50 years) warming revealed that all SOC stock reduction occurred within the first 5 years of warming, after which continued warming no longer reduced SOC stocks. This rapid equilibration of SOC observed in Andosol suggests a critical role for ecosystem adaptations to warming and could imply short-lived soil carbon-climate feedbacks. Our data further revealed that the soil C loss occurred in all aggregate size fractions and that SOC stock reduction was only visible in topsoil (0-10 cm). SOC stocks in subsoil (10-30 cm), where plant roots were absent, showed apparent conservation after > 50 years of warming. The observed depth-dependent warming responses indicate that explicit vertical resolution is a prerequisite for global models to accurately project future SOC stocks for this soil type and should be investigated for soils with other mineralogies.

KW - ORGANIC-CARBON

KW - GEOTHERMAL ECOSYSTEMS

KW - CLIMATE-CHANGE

KW - TEMPERATURE

KW - RESPONSES

KW - TERM

U2 - 10.5194/bg-19-3381-2022

DO - 10.5194/bg-19-3381-2022

M3 - Journal article

VL - 19

SP - 3381

EP - 3393

JO - Biogeosciences

JF - Biogeosciences

SN - 1726-4170

IS - 14

ER -