10/30/2013
Faster Organic Matter Decomposition Predicted for Well-Drained Boreal Soils Following Permafrost Degradation
Summary
Roots and litterfall can release readily decomposable carbon sources into soil. This newly added carbon may increase or suppress the decomposition of older soil organic matter phenomena known as positive or negative “priming effects.” In temperate regions, recent research suggests priming effects can be a critical mechanism controlling soil carbon dynamics, yet virtually nothing is known about priming effects in boreal ecosystems. To investigate the importance of priming effects in boreal forest soils, researchers at Argonne National Laboratory developed a mechanistic model that can simulate simultaneously occurring soil physical, chemical, biological, and hydrological processes and their interactions. The model was then used to perform sensitivity analyses for two black spruce forest sites, with and without underlying permafrost. Overall, priming effects were strongly controlled by the intensity and frequency of dissolved organic carbon (DOC) inputs to soil. Greater priming effects were predicted for the site with favorable soil water flow than for the site where soil water flow was limited because water flow can carry DOC to deep soil layers, which are rich in organic carbon in boreal soils. Modeling results suggest that priming effects might be accelerated for sites where permafrost degradation leads to drier soil conditions and favorable water transport into deeper layers. In addition to DOC dynamics, priming effects were most sensitive to changes in the composition of solid soil organic carbon, followed by biomass changes in the soil microbial community. The findings from this model sensitivity analysis highlight the urgent need to better study these key parameters in future laboratory and field experiments in permafrost regions.
References
Fan, Z., J. D. Jastrow, C. Liang, R. Matamala, and R. M. Miller. 2013. “Priming Effects in Boreal Black Spruce Forest Soils: Quantitative Evaluation and Sensitivity Analysis,” PLoS ONE 8, e77880. DOI:10.1371/journal.pone.0077880.