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Open AccessArticle

Biotic Interactions in Experimental Antarctic Soil Microcosms Vary with Abiotic Stress

1
Department of Biology, Colorado State University, Fort Collins, CO 80523-1878, USA
2
Department of Biology and Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523-1878, USA
*
Author to whom correspondence should be addressed.
Soil Syst. 2019, 3(3), 57; https://doi.org/10.3390/soilsystems3030057
Received: 29 June 2019 / Revised: 12 August 2019 / Accepted: 13 August 2019 / Published: 27 August 2019
(This article belongs to the Special Issue Nematodes in Soil Systems)
Biotic interactions structure ecological communities but abiotic factors affect the strength of these relationships. These interactions are difficult to study in soils due to their vast biodiversity and the many environmental factors that affect soil species. The McMurdo Dry Valleys (MDV), Antarctica, are relatively simple soil ecosystems compared to temperate soils, making them an excellent study system for the trophic relationships of soil. Soil microbes and relatively few species of nematodes, rotifers, tardigrades, springtails, and mites are patchily distributed across the cold, dry landscape, which lacks vascular plants and terrestrial vertebrates. However, glacier and permafrost melt are expected to cause shifts in soil moisture and solutes across this ecosystem. To test how increased moisture and salinity affect soil invertebrates and their biotic interactions, we established a laboratory microcosm experiment (4 community × 2 moisture × 2 salinity treatments). Community treatments were: (1) Bacteria only (control), (2) Scottnema (S. lindsayae + bacteria), (3) Eudorylaimus (E. antarcticus + bacteria), and (4) Mixed (S. lindsayae + E. antarcticus + bacteria). Salinity and moisture treatments were control and high. High moisture reduced S. lindsayae adults, while high salinity reduced the total S. lindsayae population. We found that S. lindsayae exerted top-down control over soil bacteria populations, but this effect was dependent on salinity treatment. In the high salinity treatment, bacteria were released from top-down pressure as S. lindsayae declined. Ours was the first study to empirically demonstrate, although in lab microcosm conditions, top-down control in the MDV soil food web. View Full-Text
Keywords: nematode; bacteria; soil communities; trophic interactions; biological interactions; polar; desert; top-down effects nematode; bacteria; soil communities; trophic interactions; biological interactions; polar; desert; top-down effects
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Shaw, E.A.; Wall, D.H. Biotic Interactions in Experimental Antarctic Soil Microcosms Vary with Abiotic Stress. Soil Syst. 2019, 3, 57.

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