Global budgets ascribe 4-10% of atmospheric methane (CH ) sinks to upland soils and have assumed until recently that soils are the sole surface for CH exchange in upland forests. Here we report that CH is emitted from the stems of dominant tree species in a temperate upland forest, measured using both the traditional static-chamber method and a new high-frequency, automated system. Tree emissions averaged across 68 observations on 17 trees from May to September were 1.59 ± 0.88 μmol CH m stem h (mean ± 95% confidence interval), while soils adjacent to the trees consumed atmospheric CH at a rate of -4.52 ± 0.64 μmol CH m soil h (P < 0.0001). High-frequency measurements revealed diurnal patterns in the rate of tree-stem CH emissions. A simple scaling exercise suggested that tree emissions offset 1-6% of the growing season soil CH sink and may have briefly changed the forest to a net CH source.

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. The factors regulating soil animal communities are poorly understood. Current theory favors niche complementarity and facilitation over competition as the primary forms of non-trophic interspecifi c interaction in soil fauna; however, competition has frequently been suggested as an important community-structuring factor in earthworms, ecosystem engineers that infl uence belowground processes. To date, direct evidence of competition in earthworms is lacking due to the diffi culty inherent in identifying a limiting resource for saprophagous animals. In the present study, we offer the fi rst direct evidence of interspecifi c competition for food in this dominant soil detritivore group by combining fi eld observations with laboratory mesocosm experiments using 13 C and 15 N double-enriched leaf litter to track consumption patterns. In our experiments, the Asian invasive species Amynthas hilgendorfi was a dominant competitor for leaf litter against two European species currently invading the temperate deciduous forests in North America. This competitive advantage may account for recent invasion success of A. hilgendorfi in forests with established populations of European species, and we hypothesize that specifi c phenological differences play an important role in determining the outcome of the belowground competition. In contrast, Eisenoides lonnbergi , a common native species in the Eastern United States, occupied a unique trophic position with limited interactions with other species, which may contribute to its persistence in habitats dominated by invasive species. Furthermore, our results supported neither the hypothesis that facilitation occurs between species of different functional groups nor the hypothesis that species in the same group exhibit functional equivalency in C and N translocation in the soil. We propose that species identity is a more powerful approach to understand earthworm invasion and its impacts on belowground processes.