title: Excess of Organic Carbon in Mountain Spruce Forest Soils after Bark Beetle Outbreak Altered Microbial N Transformations and Mitigated N-Saturation.
abstract: Mountain forests in National park Bohemian Forest (Czech Republic) were affected by bark beetle attack and windthrows in 2004-2008, followed by an extensive tree dieback. We evaluated changes in the biochemistry of the uppermost soil horizons with the emphasis on carbon (C) and nitrogen (N) cycling in a near-natural spruce (Picea abies) mountain forest after the forest dieback, and compared it with an undisturbed control plot of similar age, climate, elevation, deposition, N-saturation level, and land use history. We hypothesised that the high litter input after forest dieback at the disturbed plot and its consequent decomposition might influence the availability of C for microorganisms, and consequently, N transformations in the soil. The concentrations of dissolved organic C (DOC) and N (DON) in soil water extracts rapidly increased at the disturbed plot for 3 yeas and then continually decreased. Net ammonification exhibited a similar trend as DOC and DON, indicating elevated mineralization. Despite the high ammonium concentrations found after the forest dieback (an increase from 0.5 mmol kg-1 to 2-3 mmol kg-1), net nitrification was stable and low during these 3 years. After the DOC depletion and decrease in microbial biomass 5 years after the forest dieback, net nitrification started to rise, and nitrate concentrations increased from 0.2-1 mmol kg-1 to 2-3 mmol kg-1. Our results emphasize the key role of the availability of organic C in microbial N transformations, which probably promoted microbial heterotrophic activity at the expense of slow-growing nitrifiers.
authors.affiliation: Institute of Hydrobiology, Biology Centre of the CAS, v.v.i., České Budějovice, Czech Republic; Department of Ecosystem Biology, Faculty of Science, University of South Bohemia in České Budějovice, České Budějovice, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Kaňa
authors.affiliation: Department of Ecosystem Biology, Faculty of Science, University of South Bohemia in České Budějovice, České Budějovice, Czech Republic.
authors.forename: Karolina
authors.initials: K
authors.lastname: Tahovská
authors.affiliation: Institute of Hydrobiology, Biology Centre of the CAS, v.v.i., České Budějovice, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Kopáček
authors.affiliation: Department of Ecosystem Biology, Faculty of Science, University of South Bohemia in České Budějovice, České Budějovice, Czech Republic.
authors.forename: Hana
authors.initials: H
authors.lastname: Šantrůčková
mesh_terms: D000818:Animals; D002244:Carbon / Q000378:metabolism*; D001517:Coleoptera / Q000382:microbiology / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism*; D028222:Picea / Q000378:metabolism*
chemical_list: D002244:Carbon; D009584:Nitrogen