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Experimental evaluation of herbivory on live plant seedlings by the earthworm Lumbricus terrestris L. in the presence and absence of soil surface litter.

Kirchberger J, Eisenhauer N, Weisser WW, Türke M - PLoS ONE (2015)

Bottom Line: Lumbricus terrestris preferred to consume legume litter over litter of the other plant functional groups.Pulling live plants into earthworm burrows might induce microbial decomposition of leaves to make them suitable for later consumption.Herbivory on plants beyond the initial seedling stage may only play a minor role in earthworm nutrition and has limited potential to influence plant growth.

View Article: PubMed Central - PubMed

Affiliation: Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, D-85354 Freising, Germany.

ABSTRACT

Background: Recent studies suggested that the earthworm Lumbricus terrestris might act as a seedling predator by ingesting emerging seedlings, and individuals were observed damaging fresh leaves of various plant species in the field. To evaluate the significance of herbivore behavior of L. terrestris for plant and earthworm performance we exposed 23- to 33-days-old seedlings of six plant species to earthworms in two microcosm experiments. Plants belonged to the three functional groups grasses, non-leguminous herbs, and legumes. Leaf damage, leaf mortality, the number of leaves as well as mortality and growth of seedlings were followed over a period of up to 26 days. In a subset of replicates 0.1 g of soil surface litter of each of the six plant species was provided and consumption was estimated regularly to determine potential feeding preferences of earthworms.

Results: There was no difference in seedling growth, the number of live seedlings and dead leaves between treatments with or without worms. Fresh leaves were damaged eight times during the experiment, most likely by L. terrestris, with two direct observations of earthworms tearing off leaf parts. Another nine leaves were partly pulled into earthworm burrows. Lumbricus terrestris preferred to consume legume litter over litter of the other plant functional groups. Earthworms that consumed litter lost less weight than individuals that were provided with soil and live plants only, indicating that live plants are not a suitable substitute for litter in earthworm nutrition.

Conclusion: Our results demonstrate that L. terrestris damages live plants; however, this behavior occurs only rarely. Pulling live plants into earthworm burrows might induce microbial decomposition of leaves to make them suitable for later consumption. Herbivory on plants beyond the initial seedling stage may only play a minor role in earthworm nutrition and has limited potential to influence plant growth.

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Weight change of earthworms feeding or not feeding on litter material.Comparison of weight change of individuals of L. terrestris which fed on litter material (n = 12, 0.1 g shoot litter per plant species was offered = 0.6 g in total) and individuals not feeding on litter material (n = 19) at the end of the experiments. Weight change differed significantly between groups (ANOVA, p = 0.017). Results are given as mean ± SE.
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pone.0123465.g006: Weight change of earthworms feeding or not feeding on litter material.Comparison of weight change of individuals of L. terrestris which fed on litter material (n = 12, 0.1 g shoot litter per plant species was offered = 0.6 g in total) and individuals not feeding on litter material (n = 19) at the end of the experiments. Weight change differed significantly between groups (ANOVA, p = 0.017). Results are given as mean ± SE.

Mentions: Body weight of earthworms at the start of the experiments did not differ between herbivory and seedling mortality experiment (ANOVA; F1,38 = 0.134, p = 0.717). Nine out of the 40 earthworms in both experiments were not found at the end of the experiment and most likely died during the experiments. The initial weight of individuals that were still alive after the experiment (5.19 ± 0.20 g mean ± SE, range 3.32–7.89, n = 31) was significantly higher than of individuals that died during the experiment (3.96 ± 0.58 g, range 3.49–6.45, n = 9) (S1 Statistics, S1.9; GLM; z = 2.24, p = 0.0253) indicating that mainly weak individuals died during the experiment. Eight of the nine earthworms died in microcosms without surface litter material, while only one individual died in microcosms with litter material, but neither litter consumption had a significant impact on survival (z = 1.18, p = 0.237) nor the type of experiment (z = 1.80, p = 0.0724). At the end of the experiments all living individuals of L. terrestris had lost weight. Individuals lost significantly less weight if litter material was consumed (28.92 ± 2.38%, range 5.24–39.08%, n = 12) than those which did not feed on litter material (35.39 ± 1.55%, range = 24.84–46.27%, n = 19) (Fig 6; ANOVA; F1,29 = 6.45, p = 0.0167).


Experimental evaluation of herbivory on live plant seedlings by the earthworm Lumbricus terrestris L. in the presence and absence of soil surface litter.

Kirchberger J, Eisenhauer N, Weisser WW, Türke M - PLoS ONE (2015)

Weight change of earthworms feeding or not feeding on litter material.Comparison of weight change of individuals of L. terrestris which fed on litter material (n = 12, 0.1 g shoot litter per plant species was offered = 0.6 g in total) and individuals not feeding on litter material (n = 19) at the end of the experiments. Weight change differed significantly between groups (ANOVA, p = 0.017). Results are given as mean ± SE.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401770&req=5

pone.0123465.g006: Weight change of earthworms feeding or not feeding on litter material.Comparison of weight change of individuals of L. terrestris which fed on litter material (n = 12, 0.1 g shoot litter per plant species was offered = 0.6 g in total) and individuals not feeding on litter material (n = 19) at the end of the experiments. Weight change differed significantly between groups (ANOVA, p = 0.017). Results are given as mean ± SE.
Mentions: Body weight of earthworms at the start of the experiments did not differ between herbivory and seedling mortality experiment (ANOVA; F1,38 = 0.134, p = 0.717). Nine out of the 40 earthworms in both experiments were not found at the end of the experiment and most likely died during the experiments. The initial weight of individuals that were still alive after the experiment (5.19 ± 0.20 g mean ± SE, range 3.32–7.89, n = 31) was significantly higher than of individuals that died during the experiment (3.96 ± 0.58 g, range 3.49–6.45, n = 9) (S1 Statistics, S1.9; GLM; z = 2.24, p = 0.0253) indicating that mainly weak individuals died during the experiment. Eight of the nine earthworms died in microcosms without surface litter material, while only one individual died in microcosms with litter material, but neither litter consumption had a significant impact on survival (z = 1.18, p = 0.237) nor the type of experiment (z = 1.80, p = 0.0724). At the end of the experiments all living individuals of L. terrestris had lost weight. Individuals lost significantly less weight if litter material was consumed (28.92 ± 2.38%, range 5.24–39.08%, n = 12) than those which did not feed on litter material (35.39 ± 1.55%, range = 24.84–46.27%, n = 19) (Fig 6; ANOVA; F1,29 = 6.45, p = 0.0167).

Bottom Line: Lumbricus terrestris preferred to consume legume litter over litter of the other plant functional groups.Pulling live plants into earthworm burrows might induce microbial decomposition of leaves to make them suitable for later consumption.Herbivory on plants beyond the initial seedling stage may only play a minor role in earthworm nutrition and has limited potential to influence plant growth.

View Article: PubMed Central - PubMed

Affiliation: Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, D-85354 Freising, Germany.

ABSTRACT

Background: Recent studies suggested that the earthworm Lumbricus terrestris might act as a seedling predator by ingesting emerging seedlings, and individuals were observed damaging fresh leaves of various plant species in the field. To evaluate the significance of herbivore behavior of L. terrestris for plant and earthworm performance we exposed 23- to 33-days-old seedlings of six plant species to earthworms in two microcosm experiments. Plants belonged to the three functional groups grasses, non-leguminous herbs, and legumes. Leaf damage, leaf mortality, the number of leaves as well as mortality and growth of seedlings were followed over a period of up to 26 days. In a subset of replicates 0.1 g of soil surface litter of each of the six plant species was provided and consumption was estimated regularly to determine potential feeding preferences of earthworms.

Results: There was no difference in seedling growth, the number of live seedlings and dead leaves between treatments with or without worms. Fresh leaves were damaged eight times during the experiment, most likely by L. terrestris, with two direct observations of earthworms tearing off leaf parts. Another nine leaves were partly pulled into earthworm burrows. Lumbricus terrestris preferred to consume legume litter over litter of the other plant functional groups. Earthworms that consumed litter lost less weight than individuals that were provided with soil and live plants only, indicating that live plants are not a suitable substitute for litter in earthworm nutrition.

Conclusion: Our results demonstrate that L. terrestris damages live plants; however, this behavior occurs only rarely. Pulling live plants into earthworm burrows might induce microbial decomposition of leaves to make them suitable for later consumption. Herbivory on plants beyond the initial seedling stage may only play a minor role in earthworm nutrition and has limited potential to influence plant growth.

Show MeSH
Related in: MedlinePlus