Primary productivity as a control over soil microbial diversity along environmental gradients in a polar desert ecosystem

Kevin M Geyer; Cristina D Takacs-Vesbach; Michael N Gooseff; John E Barrett

doi:10.7717/peerj.3377

Primary productivity as a control over soil microbial diversity along environmental gradients in a polar desert ecosystem

PeerJ. 2017 Jul 25:5:e3377. doi: 10.7717/peerj.3377. eCollection 2017.

Authors

Kevin M Geyer¹, Cristina D Takacs-Vesbach², Michael N Gooseff^{3

4}, John E Barrett⁵

Affiliations

¹ Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH, USA.
² Department of Biology, University of New Mexico, Albuquerque, NM, USA.
³ Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA.
⁴ Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, CO, USA.
⁵ Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA.

Abstract

Primary production is the fundamental source of energy to foodwebs and ecosystems, and is thus an important constraint on soil communities. This coupling is particularly evident in polar terrestrial ecosystems where biological diversity and activity is tightly constrained by edaphic gradients of productivity (e.g., soil moisture, organic carbon availability) and geochemical severity (e.g., pH, electrical conductivity). In the McMurdo Dry Valleys of Antarctica, environmental gradients determine numerous properties of soil communities and yet relatively few estimates of gross or net primary productivity (GPP, NPP) exist for this region. Here we describe a survey utilizing pulse amplitude modulation (PAM) fluorometry to estimate rates of GPP across a broad environmental gradient along with belowground microbial diversity and decomposition. PAM estimates of GPP ranged from an average of 0.27 μmol O₂/m²/s in the most arid soils to an average of 6.97 μmol O₂/m²/s in the most productive soils, the latter equivalent to 217 g C/m²/y in annual NPP assuming a 60 day growing season. A diversity index of four carbon-acquiring enzyme activities also increased with soil productivity, suggesting that the diversity of organic substrates in mesic environments may be an additional driver of microbial diversity. Overall, soil productivity was a stronger predictor of microbial diversity and enzymatic activity than any estimate of geochemical severity. These results highlight the fundamental role of environmental gradients to control community diversity and the dynamics of ecosystem-scale carbon pools in arid systems.

Keywords: Biogeochemistry; Environmental gradients; McMurdo Dry Valleys; Microbial ecology; Primary production; Pulse amplitude modulation fluorometry.

Grants and funding

This research was funded by McMurdo LTER NSF OPP grant 1115245. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.