Post-fire soil respiration in relation to burnt wood management in a Mediterranean mountain ecosystem

After a wildfire, the management of burnt wood may determine microclimatic conditions and microbiological activity with the potential to affect soil respiration. To experimentally analyze the effect on soil respiration, we manipulated a recently burned pine forest in a Mediterranean mountain (Sierra Nevada National and Natural Park, SE Spain). Three representative treatments of post-fire burnt wood management were established at two elevations: (1) "salvage logging" (SL), where all trees were cut, trunks removed, and branches chipped; (2) "non-intervention" (NI), leaving all burnt trees standing; and (3) "cut plus lopping" (CL), a treatment where burnt trees were felled, with the main branches lopped off, but left in situ partially covering the ground surface. Seasonal measurements were carried out over the course of two years. In addition, we performed continuous diurnal campaigns and an irrigation experiment to ascertain the roles of soil temperature and moisture in determining CO2 fluxes across treatments. Soil CO2 fluxes were highest in CL (average of 3.34 +/- 0.191 mu mol m(-2) s(-1)) and the lowest in SL (2.21 +/- 0.11 mu mol m(-2) s(-1)). Across seasons, basal values were registered during summer (average of 1.46 +/- 0.04 mu mol m(-2) s(-1)), but increased during the humid seasons (up to 10.07 +/- 1.08 mu mol m(-2) s(-1) in spring in CL). Seasonal and treatment patterns were consistent at the two elevations (1477 and 2317 m a.s.l.), although respiration was half as high at the higher altitude. Respiration was mainly controlled by soil moisture. Watering during the summer drought boosted CO2 effluxes (up to 37 +/- 6 mu mol m(-2) s(-1) just after water addition), which then decreased to basal values as the soil dried. About 64% of CO2 emissions during the first 24 h could be attributed to the degasification of soil pores, with the rest likely related to biological processes. The patterns of CO2 effluxes under experimental watering were similar to the seasonal tendencies, with the highest pulse in CL Temperature, however, had a weak effect on soil respiration, with Q(10) values of ca. 1 across seasons and soil moisture conditions. These results represent a first step towards illustrating the effects of post-fire burnt wood management on soil respiration, and eventually carbon sequestration. (C) 2011 Elsevier B.V. All rights reserved.