COS 5-3 - Soil respiration responses to temperature are affected by substrate supply and earthworm activities

Monday, August 8, 2011: 2:10 PM
6A, Austin Convention Center
Lijun Xia, Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD and K. Szlavecz, EPS, Johns Hopkins University, Baltimore, MD

The temperature dependence of soil respiration is of considerable ecological importance in the context of possible climate-change feed back effects. Multiple confounding factors could influence temperature sensitivity, as discussed by some studies, however, the effect of invertebrates on temperature sensitivity has never been discussed, and the experimental results of substrate supply on soil respiration are controversial. To look at if substrate supply and earthworm could influence soil respiration, we set up a field experiment in 70 and 150 year old temperate forest stands at the Smithsonian Environmental Research Center, in Edgewater, Maryland. We manipulated earthworm density, by removing and adding earthworms and substrate supply using American beech or Tulip poplar. We measured soil respiration, soil temperature and soil moisture from Nov 2008 to June 2010.



Average Q10 and seasonal Q10 were both calculated based on soil respiration and soil temperature data. Q10 had a large seasonal variation with the annual minimum occurring in midsummer and annual maximum occurring in the winter and spring. The higher Q10 value during winter and spring is probably due to the low soil temperature and increasing root respiration. Q10 value was higher in the treatments with beech leaf litter than with Tulip poplar, indicating that the temperature dependence of low quality substrate is higher than high quality substrate. Q10 value was lower with higher earthworm density in the old forest, indicating that earthworms could change the overall temperature response by stimulating carbon decomposition and redistributing fresh soil organic matter from soil surface to mineral layer. The effects of substrate quality, earthworm activities, soil moisture and temperature on Q10 have important implications for predicting the response of terrestrial ecosystems to future global warming.

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