In situ soil respiration at reclaimed and unreclaimed post-mining sites: Responses to temperature and reclamation treatment

Soil respiration accounts for much of the CO2 released from terrestrial ecosystems into the atmosphere. Although respiration depends on temperature, the relationship between respiration and temperature may vary among soils. Here, we measured soil respiration and soil temperature in chronosequences of reclaimed and unreclaimed post-mining sites (10-50-year-old coal mining heaps near Sokolov, the Czech Republic) to determine the major factors affecting temperature-dependent soil respiration. Soil respiration was repeatedly measured in situ during 2011 and 2012 at five reclaimed sites (planted with alder) and five unreclaimed sites (overgrown with willow, birch, and aspen). In addition, spatial heterogeneity was assessed by repeatedly measuring soil respiration at 30 permanent points at one 28-year-old site (the "30-point" site) in 2007-2008. In all sites root biomass, soil carbon (C) content, soil pH, and the thickness of Oe layer were also measured. In the chronosequences and 30-point site, the relationship between soil respiration and temperature increased with soil C content; soil respiration was unrelated to temperature if soil C content was <9%. The increase in respiration with temperature was enhanced by a thick Oe layer and by high root biomass. Soil respiration at reclaimed sites increased with site age to age 30 years and then decreased. The decrease in respiration at the older sites was associated with a decrease in soil temperature (associated with increased shading). Respiration at unreclaimed sites increased with age and was usually lower than in reclaimed alder plantation of similar ages. (C) 2014 Elsevier B.V. All rights reserved.