Tree leaf litter composition and nonnative earthworms influence plant invasion in experimental forest floor mesocosms |
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Authors: | R Travis Belote Robert H Jones |
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Institution: | (1) Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA |
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Abstract: | Dominant tree species influence community and ecosystem components through the quantity and quality of their litter. Effects
of litter may be modified by activity of ecosystem engineers such as earthworms. We examined the interacting effects of forest
litter type and earthworm presence on invasibility of plants into forest floor environments using a greenhouse mesocosm experiment.
We crossed five litter treatments mimicking historic and predicted changes in dominant tree composition with a treatment of
either the absence or presence of nonnative earthworms. We measured mass loss of each litter type and growth of a model nonnative
plant species (Festuca arundinacea, fescue) sown into each mesocosm. Mass loss was greater for litter of tree species characterized by lower C:N ratios. Earthworms
enhanced litter mass loss, but only for species with lower C:N, leading to a significant litter × earthworm interaction. Fescue
biomass was significantly greater in treatments with litter of low C:N and greater mass loss, suggesting that rapid decomposition
of forest litter may be more favorable to understory plant invasions. Earthworms were expected to enhance invasion by increasing
mass loss and removing the physical barrier of litter. However, earthworms typically reduced invasion success but not under
invasive tree litter where the presence of earthworms facilitated invasion success compared to other litter treatments where
earthworms were present. We conclude that past and predicted future shifts in dominant tree species may influence forest understory
invasibility. The presence of nonnative earthworms may either suppress of facilitate invasibility depending on the species
of dominant overstory tree species and the litter layers they produce. |
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Keywords: | Ailanthus altissima Castanea dentata Decomposition Earthworms Invasional meltdown Leaf litter Lumbricus terrestris Plant invasions |
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