REGULAR ARTICLE Experimental forest soil warming: response of autotrophic and heterotrophic soil respiration to a short-term 10°C temperature rise Andreas Schindlbacher & Sophie Zechmeister-Boltenstern & Barbara Kitzler & Robert Jandl Received: 5 June 2007 / Accepted: 1 December 2007 / Published online: 21 December 2007 # Springer Science + Business Media B.V. 2007 Abstract We warmed the top soil of a mature coniferous forest stand by means of heating cables on control and trenched plots within 24 h by 10°C at 1 cm soil depth (9°C at 5 cm depth) and measured the effect on the autotrophic (R A ) and heterotrophic (R H ) component of total soil CO 2 efflux (R S ). The short time frame of warming enabled us to exclude con- founding fluctuations in soil moisture and carbon (C) flow from the canopy. The results of the field study were backed up by a lab soil incubation experi- ment. During the first 12 h of warming, R A strongly responded to soil warming; The Q 10 values were 5.61 and 6.29 for 1 and 5 cm soil depth temperature. The Q 10 values for R A were almost twice as high as the Q 10 values of R H (3.04 and 3.53). Q 10 values above 5 are above reasonable plant physiological values for root respiration. We see interactions of roots, mycorrhizae and heterotrophic microbes, combined with fast substrate supply to the rhizosphere as an explanation for the high short-term temperature re- sponse of R A . When calculated over the whole duration (24 h) of the field soil-warming experiment, temperature sensitivities of R A and R H were similar (no significant difference at P <0.05); Q 10 values were 3.16 and 3.96 for R A and 2.94 and 3.35 for R H calculated with soil temperatures at 1 and 5 cm soil depth, respectively. Laboratory incubation showed that different soil mois- ture contents of trenched and control plots affected rates of R H , but did not affect the temperature sen- sitivity of R H . We conclude that a single parameter is sufficient to describe the temperature sensitivity of R S in soil C models which operate on larger temporal and spatial scales. The strong short-term response of R A may be of relevance in soils suspected to experience increasingly strong diurnal temperature variations. Keywords Autotrophic respiration . Heterotrophic respiration . Q 10 . Soil respiration . Soil warming Introduction Soil respiration is the largest terrestrial source of CO 2 to the atmosphere and currently represents an annual Plant Soil (2008) 303:323–330 DOI 10.1007/s11104-007-9511-2 Responsible Editor: Klaus Butterbach-Bahl. A. Schindlbacher (*) Institute of Forest Ecology, Department of Forest and Soil Science, University of Natural Resources and Applied Life Sciences, BOKU, Vienna, Austria e-mail: andreas.schindlbacher@bfw.gv.at A. Schindlbacher : S. Zechmeister-Boltenstern : B. Kitzler : R. Jandl Institute of Forest Ecology, Federal Office and Research Centre for Forests – BFW, Seckendorff-Gudent-Weg 8, 1131 Vienna, Austria