Experimental Warming Effects on Soil Respiration at the Temperate Boreal Forest Ecotone
Abstract
Climate models project that global mean annual temperature will increase by 1.1-6.4°C by the end of the 21st century. Whether terrestrial ecosystem feedbacks will mitigate or enhance warming represents a significant uncertainty in such projections of future climate. One of the largest potential positive feedbacks to climate warming is that arising from enhanced release of CO2 from warmer soils. Soils contain approximately twice as much carbon (C) as the atmosphere and microbial decomposition of soil C is expected to increase with climate warming, as temperature is often the most important factor in determining rates of soil organic matter decomposition. Thus, the aim of this investigation is to determine the soil respiration response to warming in a highly replicated open-air ecosystem warming experiment in two southern boreal forests of Minnesota. We measured in situ soil respiration response to ecosystem warming in an open-air warming experiment at two southern boreal forest sites in northern Minnesota. The experiment uses infrared heat lamps and soil heating cables (at 10-cm depth) to heat 7-m2 plots continuously by during the growing season by 2 or 4°C above ambient. Additionally, there are two ambient temperature treatments, one undisturbed, and the other with inactive soil warming cables (n=6). We measured soil CO2 flux every two weeks during the snow free season for two growing seasons (2009-2010) using a portable infrared gas analyzer with soil chamber attached. To date, we found slight increases in soil respiration in the two heated treatments relative to the disturbed soil control, corresponding to a 13% (2009) and 14% (2010) increase in soil CO2 flux in the +4°C treatment. These treatment effects are smaller than initial warming effects on soil respiration in many other studies. Several untested mechanisms could explain the smaller than expected warming effects on soil respiration. One likely explanation is that warming has significantly reduced soil moisture in the well drained upland soils of these southern boreal forest sites, offsetting positive effects of warming on respiration. These results suggest that warming-induced feedbacks from increased soil respiration may not be as large as would be predicted from simple temperature responses of respiration.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.B41E0370E
- Keywords:
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- 0428 BIOGEOSCIENCES / Carbon cycling;
- 0486 BIOGEOSCIENCES / Soils/pedology;
- 1630 GLOBAL CHANGE / Impacts of global change