Belowground nematode herbivores are resistant to elevated atmospheric CO2 concentrations in grassland ecosystems |
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Authors: | Edward Ayres Diana H. Wall Breana L. Simmons Christopher B. Field Daniel G. Milchunas Jack A. Morgan Jacques Roy |
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Affiliation: | 1. Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, USA;2. Department of Biology, Colorado State University, Fort Collins, CO 80523, USA;3. Department of Global Ecology, Carnegie Institution, 260 Panama Street, Stanford, CA 94305, USA;4. Forest, Rangeland and Watershed Stewardship, Colorado State University, Fort Collins, CO 80523, USA;5. USDA-ARS Rangeland Resources Research Unit, Crops Research Laboratory, 1701 Center Avenue, Fort Collins, CO 80526, USA;6. Centre d’ Ecologie Fonctionnelle et Evolutive, CNRS, 34293 Montpellier Cedex 5, France |
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Abstract: | Grasslands are considered to be one of the most sensitive ecosystems to rising atmospheric CO2 concentrations, since, in addition to direct effects of elevated CO2 on plant growth, indirect increases in water availability as an effect of elevated CO2 may enhance primary production and alter plant community composition in these typically dry ecosystems. Moreover, grasslands support large populations of belowground herbivores that consume a major portion of plant biomass. The direct trophic link between herbivores and plants suggests that primary consumers may be particularly sensitive to rising CO2 concentrations; however, the responses of belowground grassland herbivores have rarely been investigated. Here, we report the response of a range of herbivorous nematode populations to elevated CO2 concentrations from three distinct grassland experiments. The three studies each involved 5–6 years of CO2 fumigation, utilized natural or representative plant and soil communities, and were sampled at the end of the growing season. In the vast majority of cases, elevated CO2 did not affect the abundance of nematode families; only two nematode families were significantly influenced by CO2 enrichment (Anguinidae increased in one case and Hoplolaimidae decreased in another). Similarly, elevated CO2 did not influence the total abundance, family richness, diversity or plant parasitic index of the herbivorous nematode community. These neutral responses to CO2 enrichment occurred despite increased root production in all three experiments, suggesting a simultaneous antagonistic mechanism may have operated, possibly decreased root quality and/or changes in the soil environment. Whatever the mechanism, our findings suggest that herbivorous nematodes in grassland ecosystems are resistant to rising atmospheric CO2 concentrations. |
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