2 research outputs found

    Soil nitrogen dynamics three years after a severe Araucaria-Nothofagus forest fire

    No full text
    Wildfires have shaped the biogeography of south Chilean Araucaria-Nothofagus rainforest vegetation patterns, but their impact on soil properties and associated nutrient cycling remains unclear. Nitrogen (N) availability shows a site-specific response to wildfire events indicating the need for an increased understanding of underlying mechanisms that drive changes in soil N cycling. In this study, we selected unburned and burned sites in a large area of the National Park Tolhuaca that was affected by a stand-replacing wildfire in February 2002. We conducted net N cycling flux measurements (net ammonification, net nitrification and net N mineralization assays) on soils sampled 3years after fire. In addition, samples were physically fractionated and natural abundance of C and N, and 13C-NMR analyses were performed. Results indicated that standing inorganic N pools were greater in the burned soil, but that no main differences in net N cycling fluxes were observed between unburned and burned sites. In both sites, net ammonification and net nitrification fluxes were low or negative, indicating N immobilization. Multiple linear regression analyses indicated that soil N cycling could largely be explained by two parameters: light fraction (LF) soil organic matter N content and aromatic Chemical Oxidation Resistant Carbon (COREC arom), a relative measure for char. The LF fraction, a strong NH 4 + sink, decreased as a result of fire, while COREC arom increased in the burned soil profile and stimulated NO 3 - production. The absence of increased total net nitrification might relate to a decrease in heterotrophic nitrification after wildfire. We conclude that (i) wildfire induced a shift in N transformation pathways, but not in total net N mineralization, and (ii) stable isotope measurements are a useful tool to assess post-fire soil organic matter dynamics.This study was funded by the Bilateral Scientific and Technological Cooperation between Flanders and Chile (BOF, UGent), the National Commission for Scientific and Technological Research – Chile PhD Scholarship for Yessica Rivas, (Fondecyt, N°1080065 and N°1090455), and the Dirección de Investigación y Desarrollo – Universidad Austral de Chile (DID- UACh). Yessica Rivas thanks the MECESUP Program of the doctoral school in Forest Sciences of the Universidad Austral de Chile (UACh-VCO). Dries Huygens is a postdoctoral fellow of the Fund for Scientific Research – Flanders (FWO). Pascal Boeckx thanks Fondecyt N°1085081 for the financial support during his scientific visit.Peer Reviewe
    corecore