PNNL

Abstract

The aim of this study was to i) examine the magnitude of greenhouse gas (GHG) concentrations in tree stems across the Pacific Northwest, USA (PNW), and ii) determine if the stress of saline intrusion into surrounding soils influences GHG concentrations from healthy and dead trees. We measured the concentration of CH4, CO2, and N2O during summer and winter in live and dead tree stems of five species from six coastal watersheds and related this to soil porewater GHG concentrations and salinity. pCO2 and pN2O did not vary significantly with watershed, tree health, species, or position along the aquatic continuum, whereas pCH4 was significantly higher in upstream compared to salt-influenced reaches. Stem pCH4 was positively correlated with porewater pCH4 in contrast to other GHGs. Stem pCO2 was higher in deciduous trees compared to coniferous during the summer growing months, but not significantly different across species in the winter. The above results suggest that tree stem pCH4 in these coastal settings was primarily controlled by soil linkages, pCO2 was primarily regulated by tree physiology, and factors controlling pN2O remain unclear.