Author(s)

Daniel Beverly^1,2, Scott Franklin¹

¹School of Biological Sciences, University of Northern Colorado, Greeley, CO, USA.
²Botany Department, University of Wyoming, Laramie, WY, USA.

Carbon cycling research has increased over the past 20 years, but less is known about the primary contributors to soil respiration (i.e. heterotrophic and autotrophic) under dormant conditions. It is understood that soil CO₂ effluxes are significantly lower during the winter of temperate ecosystems and assumed microorganisms dominate efflux origination. We hypothesized that heterotrophic contributions would be greater than autotrophic under simulated dormancy conditions. To test this hypothesis, we designed an experiment with the following treatments: combined autotrophic heterotrophic respiration, heterotrophic respiration, autotrophic respiration, no respiration, autotrophic respiration in vermiculite, and no respiration in vermiculite. Engelmann spruce seedlings and soil substrates were placed in specially designed respiration chambers and soil CO₂ efflux measurements were taken four times over the course of a month. Soil microbial densities and root volumes were measured for each chamber after day thirty-three. Seedling presence resulted in significantly higher soil CO₂ efflux rates for all soil substrates. Autotrophic respiration treatments were not representative of solely autotrophic soil CO₂ efflux due to soil microbial contamination of autoclaved soil substrates; however, the mean autotrophic contributions averaged less than 25% of the total soil CO₂ efflux. Soil microorganism communities were likely the primary contributor to soil CO₂ efflux in simulated dormant conditions, as treatments with the greatest proportions of microbial densities had the highest soil CO₂ efflux rates. Although this study is not directly comparable to field dormant season soil CO₂ effluxes of Engelmann spruce forest, as snowpack is not maintained throughout this experiment, relationships, and metrics from such small-scale ecosystem component processes may yield more accurate carbon budget models.

Dormant Autotrophic Respiration, Heterotrophic Respiration, Dormant Soil CO₂ Efflux, Soil Respiration, Engelmann Spruce

Beverly, D. and Franklin, S. (2015) Heterotrophic and Autotrophic Soil Respiration under Simulated Dormancy Conditions. Open Journal of Forestry, 5, 274-286. doi: 10.4236/ojf.2015.53024.