Temperate Wetland Methanogenesis: The Importance of Vegetation Type and Root Ethanol Production
- Christopher J. Williams *a and
- Joseph B. Yavittb
We evaluated the hypothesis that soil microorganisms inhabiting wetland soils prefer plant litter and soil organic matter to fuel methanogenesis rather than root exudates. Root ethanol production, microbial respiration, concentrations of dissolved organic C (DOC), and the biochemical composition of litter from four contrasting plant species were compared to CH4 production. Rates of CH4 production varied from as little as 67 μmol kg−1 d−1 associated with Lythrum salicaria L., to 675 to μmol kg−1 d−1 with Carex lacustris Willd., 1555 μmol kg−1 d−1 with Juncus effuses L., and 1647 μmol kg−1 d−1 with Typha latifolia L. Ethanol production was pronounced in Typha roots in the spring and autumn, and in Lythrum in midsummer, but showed little seasonal pattern in Juncus or Carex Concentrations of DOC did not vary with plant species and were greater in subsurface soil (13.3 mg C L−1 at 20 cm) than in surface soil (8.6 mg C L−1 at 5 cm). Our analysis of lignin oxidation products revealed plant-related differences in the lignin chemistry of soil. The p-coumaric acid content was 24 to 38% of the lignin yield in the surface soil, whereas vanillyl phenolics were dominant in the deeper soil. The ratio of acid to aldehyde was greater at depth in soils for all species except Juncus The acid/aldehyde ratio for syringyl phenolics increased with depth in soil associated with Carex Our results show that different plant species can create significant variation in soil methanogenesis, but plant-induced differences were probably caused by variation in the biochemical composition of litter rather than root ethanol production.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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