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Patterns of microbial colonization and interactions between microbial processes and vascular plants on volcanic deposits have received little attention. Previous reports have shown that atmospheric CO and hydrogen contribute significantly to microbial metabolism on Kilauea volcano (Hawaii) deposits with varied ages and successional development. Relationships between CO oxidation and plant communities were not clear, however, since deposit age and vegetation status covaried. To determine plant-microbe interactions in deposits of uniform ages, CO and hydrogen dynamics have been assayed for unvegetated tephra on a 1959 deposit at Puu Puai (PP-bare), at the edge of tree islands within the PP deposit (PP-edge) and within PP tree islands (PP-canopy). Similar assays have been conducted for vegetated and unvegetated sites on a 1969 Mauna Ulu (MU) lava flow. Net in situ atmospheric CO uptake was highest at PP-edge and PP-bare sites (2.2±0.5 and 1.3±0.1mg COm2day 1, respectively), and least for PP-canopy (3.2±0.9mg COm 2day1, net emission). Respiration rates, microbial biomass and maximum CO uptake potential showed an opposing pattern. Comparisons of atmospheric CO uptake and CO"2 production rates indicate that CO contributes significantly to microbial metabolism in PP-bare and MU-unvegetated sites, but negligibly where vegetation is well developed. Nonetheless, maximum potential CO uptake rates indicate that CO oxidizer populations increase with increasing plant biomass and consume CO actively. Some of these CO oxidizers may contribute to elevated nitrogen fixation rates (acetylene reduction) measured within tree islands, and thus, support plant successional development. © 2008 International Society for Microbial Ecology. All rights reserved.

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ISME Journal

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