Increased CO₂ efflux due to long-term experimental summer warming and litter input in subarctic tundra – CO₂ fluxes at snowmelt, in growing season, fall and winter

TY - JOUR

T1 - Increased CO2 efflux due to long-term experimental summer warming and litter input in subarctic tundra – CO2 fluxes at snowmelt, in growing season, fall and winter

AU - Nielsen, Tora Finderup

AU - Ravn, Nynne Marie Rand

AU - Michelsen, Anders

N1 - CENPERM[2019]

PY - 2019/11/1

Y1 - 2019/11/1

N2 - Aims: Soils of northern latitude tundra ecosystems have accumulated large amounts of carbon that might be released as CO2 when temperature rises and the tree-line moves north. We aim to investigate the potential CO2 flux changes at a subarctic tundra heath under changing climate. Methods: We measured daytime ecosystem respiration and photosynthesis at a subarctic heath over a full year under ambient conditions and in factorial long-term (13 years) increased summer temperature and leaf litter addition plots, and in additional short-term (2 years) summer warming plots. Results: Under ambient conditions the ecosystem was a daytime sink of CO2 in the five warmest months, but a net daytime source in the cold season. Thirteen years of summer warming by 1 °C at soil surface increased CO2 emissions, as daytime respiration increased by 37% and photosynthesis by 29% over the year. Short-term warming likewise increased fluxes. Litter addition also increased the emission of CO2 as ecosystem respiration rose by 21% but photosynthesis remained unchanged. Both warming and litter addition significantly enhanced the amount of green biomass. Conclusions: This study suggests that in a changed climate subarctic ecosystems will act as a positive feedback source of atmospheric CO2. It shows the significance of CO2 fluxes outside the growing season and demonstrates a cold-season long- but not short-term legacy effect of increased summer warming on CO2 emission.

AB - Aims: Soils of northern latitude tundra ecosystems have accumulated large amounts of carbon that might be released as CO2 when temperature rises and the tree-line moves north. We aim to investigate the potential CO2 flux changes at a subarctic tundra heath under changing climate. Methods: We measured daytime ecosystem respiration and photosynthesis at a subarctic heath over a full year under ambient conditions and in factorial long-term (13 years) increased summer temperature and leaf litter addition plots, and in additional short-term (2 years) summer warming plots. Results: Under ambient conditions the ecosystem was a daytime sink of CO2 in the five warmest months, but a net daytime source in the cold season. Thirteen years of summer warming by 1 °C at soil surface increased CO2 emissions, as daytime respiration increased by 37% and photosynthesis by 29% over the year. Short-term warming likewise increased fluxes. Litter addition also increased the emission of CO2 as ecosystem respiration rose by 21% but photosynthesis remained unchanged. Both warming and litter addition significantly enhanced the amount of green biomass. Conclusions: This study suggests that in a changed climate subarctic ecosystems will act as a positive feedback source of atmospheric CO2. It shows the significance of CO2 fluxes outside the growing season and demonstrates a cold-season long- but not short-term legacy effect of increased summer warming on CO2 emission.

U2 - 10.1007/s11104-019-04282-9

DO - 10.1007/s11104-019-04282-9

M3 - Journal article

SN - 0032-079X

VL - 444

SP - 365

EP - 382

JO - Plant and Soil

JF - Plant and Soil

IS - 1-2

ER -