Microbial and Root Components of Respiration of Sod-Podzolic Soils in Boreal Forest

The microbial contribution to the respiration of sod-podzolic soils has been estimated during two seasons (2012-2013) in boreal forest (Valdai district in Novgorod oblast, Russia) by a combination of methods of substrate induced respiration (SIR) and integration of components (IC). Despite the higher accuracy of SIR in estimating soil microbial respiration (R-mic), it is found that the combined application of these two methods results in a better correspondence of field experiments to the published data based on laboratory experiments. The contribution of microbial respiration differs between wooded and degraded sites. Hence, these sites should be investigated separately in upscaling studies of microbial respiration in soils of a boreal forest. The underestimation of microbial respiration should also be noted when using the IC method in field experiments. Among the main controls of Rmic are abiotic ones (soil temperature at a depth of 10 cm; month of the vegetation season), as well as the type of the mesohabitat. The seasonal dynamics of microbial respiration was related to the Selyaninov hydrothermal factor. Despite seasonal and cross-habitat differences in Rmic, it was specific for the particular type of soil and ecosystem.