From canopy to consumer: what makes and modifies terrestrial DOM in a temperate forest

To investigate how source and processing control the composition of “terrestrial” dissolved organic matter (DOM), we combine soil tree leachates, DOM, laboratory bioincubations, ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry in three common landscape types (upland forest, forested wetland, poor fen) Southeast Alaska’s temperate rainforest. Tree (Tsuga heterophylla Picea sitchensis) needles bark layers from each site were leached, stemflow throughfall collected to examine DOM sources. Dissolved carbon concentrations as high 167 mg CL−1 for suggesting fluxes may be substantial given hypermaritime climate region. Condensed aromatics contributed much 38% relative abundance spruce hemlock leachates coniferous trees are potential sources condensed surface waters. Soil showed wetness dictates processing, with wetland soils producing more aromatic formulae allowing preservation traditionally biolabile, aliphatic formulae. Biodegradation impacted differently, though majority source-specific marker consumed all sources, some persisted. was highly biolabile (> 50%) compositional convergence where homogenized different In contrast, upland leachate diverged diversified during bioincubations. Increasing precipitation intensity predicted change Alaska will increase leaching flushing, tightening linkages between terrestrial export coastal ocean.