Soil and heterotrophic respiration, understory photosynthesis, soil temperature and moisture, for Alaskan boreal forests with different burn frequencies

Fire frequency is increasing with climate warming in the boreal regions of interior Alaska, with short fire return intervals ( less than 50 years) becoming more common. Recent studies suggest these ‘‘reburns’’ will reduce the insulating surface organic layer and seedbanks, inhibiting black spruce regeneration and increasing deciduous cover. These changes are projected to amplify soil warming, increasing mineral soil organic carbon (SOC) decomposition rates, and impair re-establishment of understorey vegetation and the SOL (soil organic layer). We examined how reburns changed soil temperature, heterotrophic soil respiration (RH), and understorey gross primary production (GPP) and related these fluxes to soil environmental variables (temperature and moisture) and photosynthetically active radiation (PAR) and air temperature. Two distinct burn complexes previously covered by spruce were measured; both included areas burned 1x, 2x, and 3x over 60 years and mature (~90 year old) spruce forests underlain by permafrost.