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  d-1 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.