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Increased soil respiration in response to experimentally reduced snow cover and increased soil freezing in a temperate deciduous forest

Reinmann, Andrew B., Templer, Pamela H.
Biogeochemistry 2018 v.140 no.3 pp. 359-371
air temperature, climate models, deciduous forests, ecosystems, fine roots, freezing, frost, latitude, mortality, necromass, snow, snowpack, soil, soil organic matter, soil respiration, temperate forests, winter, Massachusetts
Winter snowpack in seasonally snow-covered regions plays an important role in moderating ecosystem processes by insulating soil from freezing air temperatures. However, climate models project a decline in snowpack at mid and high latitudes over the next century. We conducted a snow removal experiment in a temperate deciduous forest at Harvard Forest in Massachusetts, USA to quantify the effects of a reduced winter snowpack and increased soil freezing on total soil respiration and its bulk (i.e. heterotrophic) and root-rhizosphere components. Snow removal increased soil freezing severity by more than three-fold, which resulted in a 27.6% increase in annual total soil respiration (p = 0.058). Across our plots and years of this study, we found that the severity, rather than simply the presence of soil freezing, was the primary driver of the soil respiration response to reduced winter snowpack. Bulk soil respiration made the largest contribution to total soil respiration with root-rhizosphere respiration contributing up to 26.1 ± 6.5% of total soil respiration across plot types and years. Snow removal significantly increased fine root mortality (p = 0.03), which was positively correlated with soil frost depth and duration (p = 0.068, [Formula: see text] = 0.46), rates of total soil respiration (p = 0.075; [Formula: see text] = 0.27) and the contribution of root-rhizosphere respiration to total soil respiration (p = 0.004; [Formula: see text] = 0.58). We conclude that increased rates of soil respiration in response to soil freezing are driven by plant-mediated processes, whereby soil frost-induced root mortality stimulates respiration through decomposition of root necromass with additional enhancements possibly related to priming of soil organic matter decomposition and elevated rates of root respiration associated with growth.