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

Abstract

Wildfires have shaped the biogeography of south Chilean AraucariaNothofagus 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 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 (CORECarom), a relative measure for char. The LF fraction, a strong NH4+ sink, decreased as a result of fire, while CORECarom increased in the burned soil profile and stimulated NO3- 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

Dietary patterns in human populations from northwest Patagonia during Holocene: an approach using Binford’s frames of reference and Bayesian isotope mixing models

“…use of pottery and increased frequency of dental caries in human remains- (Della Negra 2008;Fernández 1988Fernández -1990Gordón and Novellino 2016; Barbosa 1988-1990;Lema et al 2012;Neme 2007). With the aim of establishing the contribution of different resources to the diet of the human populations under study, we built an isotope ecology using 113 values of δ 13 C and δ 15 N taken from published databases (Boeckx et al 2005;Fernández et al 2016;Giardina et al 2014;Gil et al 2006Gil et al , 2009Gil et al , 2011Gil et al , 2016Quiroga et al 2016;Rivas et al 2012) and from this work (Supplementary Tables S1 and S3). This information corresponds to archeological and modern plants and animals from Neuquén and South Mendoza.…”

How wildfires affect soil properties. A brief review

“…Death of burned trees causes the loss of mycorrhizal associations and the uptake of nutrients decreases, increasing soil N content (Smithwick et al, 2005). Active resprouting plants prevent the alteration of the N cycle in soil, but N may be leached if vegetation is severely affected (Rivas et al, 2012). Although different impacts of fire on N availability have been observed by scientists, prediction is limited by a low understanding of the post-fire processes (Smithwick et al, 2005).…”

“…Inorganic N concentrations tend to increase in burned areas more than in unburned control areas in the first years after fire (Smithwick et al, 2005;Turner et al, 2007;Boerner et al, 2009). Fire-induced changes in soil inorganic N content can be attributed to a combination of direct and indirect effects of fire, N release from dead roots and compounds where it was previously immobilized (Smithwick et al, 2005;Rivas et al, 2012). Nitrification is improved especially in burned acid soils, since decreased acidity enhances microbial activity and induces the germination of nitrogen-fixing legumes, such as Ulex parviflorus (Neary et al, 1999;Pastor-López and Martin-Martin, 1995;Raison et al, 2009), so that N levels are restored quickly (Kutiel and Naveh, 1987;Gimeno-García et al, 2000;Giovannini et al, 1990).…”

Variación en el contenido de glomalina relacionada a las proteínas del suelo, después de un incendio forestal en un Andisol en bosques de Araucaria araucana del centro-sur de Chile

“…En el presente estudio, el fuego produjo en primera instancia una disminución en la densidad de las especies de plantas micorrícicas hospederas y cambios en las propiedades físico químico de la materia orgánica del suelo, principalmente en los primeros 10 cm (Knicker et al 2007b, Rivas et al 2012b). La pérdida de especies hospederas pudo afectar la concentración de GRSP total en el suelo, variando de acuerdo a la severidad del incendio.…”