Methane emissions from tree stems in neotropical peatlands

Neotropical peatlands emit large amounts of methane (CH4) from the soil surface, but
fluxes from tree stems in these ecosystems are unknown. In this study we investigated CH4
emissions from five tree species in two forest types common to neotropical lowland peatlands
in Panama.
Methane from tree stems accounted for up to 30% of net ecosystem CH4 emissions. Peak
CH4 fluxes were greater during the wet season when the water table was high and temperatures
were lower. Emissions were greatest from the hardwood tree Campnosperma
panamensis, but most species acted as emitters, with emissions declining exponentially with
height along the stem for all species.
Overall, species identity, stem diameter, water level, soil temperature and soil CH4 fluxes
explained 54% of the variance in stem CH4 emissions from individual trees. On the landscape
level, On the landscape level, the high emissions from C. panamensis forests resulted in that
they emitted at 340 kg CH4 d1 during flooded periods despite their substantially lower areal
cover.
We conclude that emission from tree stems is an important emission pathway for CH4 flux
from Neotropical peatlands, and that these emissions vary strongly with season and forest
type.