Abstract Boreal peatlands have significant emissions
of non-methane biogenic volatile organic
compounds (BVOCs). Climate warming is expected
to affect these ecosystems both directly, with increasing
temperature, and indirectly, through water table
drawdown following increased evapotranspiration.
We assessed the combined effect of warming and
water table drawdown on the BVOC emissions from
boreal peatland microcosms. We also assessed the
treatment effects on the BVOC emissions from the
peat soil after the 7-week long experiment. Emissions
of isoprene, monoterpenes, sesquiterpenes, other
reactive VOCs and other VOCs were sampled using
a conventional chamber technique, collected on
adsorbent and analyzed by GC–MS. Carbon emitted
as BVOCs was less than 1% of the CO2 uptake and
up to 3% of CH4 emission. Water table drawdown
surpassed the direct warming effect and significantly
decreased the emissions of all BVOC groups. Only
isoprene emission was significantly increased by
warming, parallel to the increased leaf number of the
dominant sedge Eriophorum vaginatum. BVOC
emissions from peat soil were higher under the
control and warming treatments than water table
drawdown, suggesting an increased activity of anaerobic
microbial community. Our results suggest that
boreal peatlands could have concomitant negative
and positive radiative forcing effects on climate
warming following the effect of water table drawdown.
The observed decrease in CH4 emission causes
a negative radiative forcing while the increase in CO2
emission and decrease in reactive BVOC emissions,
which could reduce the cooling effect induced by the
lower formation rate of secondary organic aerosols,
both contribute to increased radiative forcing.