Wood Decomposition Following a Perennial Lupine Die-Off: A 3-Year Litterbag Study |
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Authors: | Justin L Bastow Evan L Preisser Donald R Strong |
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Institution: | (1) Center for Population Biology, University of California Davis, One Shields Ave, Davis, California 95616-8584, USA;(2) Present address: Bodega Marine Laboratory, University of California, P.O. Box 247, Bodega Bay, California 94923, USA;(3) Present address: Department of Biological Sciences, University of Rhode Island, 100 Flagg Rd, Kingston, Rhode Island 02881, USA |
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Abstract: | Woody debris is a conspicuous feature of many ecosystems and can be a large pool of stored carbon and nutrients. In the California
coastal prairie, yellow bush lupines (Lupinus arboreus) experience mass die-offs, producing large quantities of woody detritus. Live lupines are fed upon by the stem-boring caterpillars
of the ghost moth, Hepialus californicus, and outbreaks of ghost moths are one factor contributing to lupine die-offs. A common detritivore, the terrestrial isopod
Porcellio scaber, frequently inhabits ghost moth tunnels in lupine wood. We used a litterbag experiment to test the hypothesis that H. californicus increases decomposition of woody lupine detritus by facilitating its use by P. scaber. Isopod access to wood was crossed with simulated ghost moth boring to measure the independent and interactive effects of
these two arthropods on total mass loss, as well as on carbon, nitrogen, and lignin dynamics. Isopods initially colonized
litterbags but were not more abundant on L. arboreus logs that had simulated ghost moth boring than on logs without boring. They were rare in litterbags collected at 12 months
or later and had no effect on wood decomposition. Simulated ghost moth boring increased wood decomposition (P = 0.0021), from 50.5 to 55.1% mass loss after 3 years. This effect was likely due to increased surface area for microbial
utilization of the wood. Lupine wood had an initial lignin content of 14.70 ± 0.67%, but lignin did not appear to decompose
during the 3 years of this study, and by the end of the experiment accounted for 32.6 ± 1.12% of the remaining wood. Neither
ghost moth boring nor isopod access affected lignin loss. Lupine wood from a die-off in 2002 was estimated to have contained
three times more nitrogen per unit area than the yearly input of annual grass litter. The slow decomposition of lupine wood,
however, restricts the rate at which nitrogen is released into the soil and results in the storage of carbon and nutrients
in lupine wood for several years following such die-offs. |
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Keywords: | woody debris herbivore coastal prairie detritivore isopod Lupinus arboreus Hepialus californicus Porcellio scaber nitrogen lignin |
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