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Application of 210 Pb ex inventories to measure net hillslope erosion at burned sites
Author(s) -
Perreault Lauren M.,
Yager Elowyn M.,
Aalto Rolf
Publication year - 2013
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.3266
Subject(s) - environmental science , erosion , hydrology (agriculture) , sediment , organic matter , geology , ecology , geomorphology , geotechnical engineering , biology
Fallout radionuclides, including lead‐210 excess ( 210 Pb ex ), have been broadly and successfully used to quantify net hillslope sediment transport in agricultural, pastoral and forested landscapes but have only recently been applied in burned terrain. Quantifying post‐fire erosion is important because fires can amplify hillslope erosion, impacting terrestrial and aquatic habitat and water quality. However, we lack a basic understanding of the fate of 210 Pb ex in fires. To address this knowledge gap, we collected over 400 soil samples from unburned, moderately and severely burned forested sites in central Idaho. We measured soil 210 Pb ex content at stable reference and eroding sites and in mineral and organic soil components. At all sites, organic matter had the highest concentration of 210 Pb ex , representing 30% to 73% of the total activity. At the severely and moderately burned sites, 210 Pb ex reference inventories were lower by 58% and 41%, with about 40% less organic mass, relative to the unburned site. These results indicate that most 210 Pb ex in our semi‐arid, forested sites was bound to organic matter, and that a substantial portion of this lead was lost due to forest fires. These losses likely occurred through volatilization and wind transport of smoke and ash. In the moderately burned site, 210 Pb ex losses were more spatially variable, potentially due to spatially uneven fire intensity and effects. Despite equal percent losses of 210 Pb ex , lower inventories at the burned sites produced lower calculated net erosion rates relative to the unburned site. Thus, given methodological uncertainties, 210 Pb ex losses due to fire, and the subsequent sensitivity of calculated net erosion rates to these lower 210 Pb ex inventories, we suggest this method should not be used in burned terrain to calculate absolute net erosion and deposition rates. However, within a given burned site, 210 Pb ex inventories still provide useful information describing relative soil losses and storage across the landscape. Copyright © 2012 John Wiley & Sons, Ltd.