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Soil nitrogen dynamics three years after a severe Araucaria–Nothofagus forest fire
Author(s) -
RIVAS Y.,
HUYGENS D.,
KNICKER H.,
GODOY R.,
MATUS F.,
BOECKX P.
Publication year - 2012
Publication title -
austral ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.688
H-Index - 87
eISSN - 1442-9993
pISSN - 1442-9985
DOI - 10.1111/j.1442-9993.2011.02258.x
Subject(s) - cycling , nitrogen cycle , nitrification , mineralization (soil science) , environmental science , soil water , rainforest , ecology , soil organic matter , nitrogen , environmental chemistry , agronomy , chemistry , forestry , biology , soil science , geography , organic chemistry
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 3 years after fire. In addition, samples were physically fractionated and natural abundance of C and N, and 13 C‐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.