Post-Wildfire Potential for Carbon and Nitrogen Sequestration in the Southwestern United States in Restored Ephemeral and Intermittent Stream Channels
Abstract
Although ephemeral and intermittent streams have characteristics of both floodplains and perennial streams, they play a unique role in ecohydrologic systems. Globally, they make up more than half the length of all rivers and streams. Yet, studies focused on their hydrologic and biochemical function remain limited, especially with respect to carbon (C) and nitrogen (N) storage and movement. Increased frequency and extent of high intensity wildfires is causing significant losses of C and N from ecosystems through wind transport of vapor and ash, and through water transport of ash, char, and woody debris. Losses caused by water transport are exacerbated by decreased permeability of charred soils and decreased surface roughness, both of which can promote flooding, erosion, and debris flows. These in turn promote biological and chemical oxidation C and N, and consequent losses to the atmosphere. Efforts to stabilize hillslopes and reduce erosion in burned and degraded watersheds can reduce loss of C and N by promoting above and below-ground storage through capture and burial of C- and N-rich sediments, growth of new vegetation, and anoxic conditions below rising water tables. This study measured C and N and their stable isotopes in samples of sediments taken within ephemeral channels upgradient of erosion control structures in two different watersheds. We combined the results with information on landcover, and fire history and severity to understand sources and amount of C and N. Results indicate that greater fire severity was linked to increased C and N content in sediments captured upgradient of erosion control structures. Carbon isotopes indicate that a higher proportion of C3 plant material was delivered in sediments captured by erosion control structures in the watershed that had a higher proportion of forest and greater burn severity. The potential for sequestration of carbon in the southwest US was calculated using the median carbon content found upgradient of erosion control structures, yielding a conservative estimate of 0.019 Pg of carbon. Though relatively small compared to the amount estimated in previous studies to be stored globally in the top meter of soils (>1500 Pg), it is significant in terms of ecosystem services and regional efforts to promote storage and reduce losses of carbon.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMEP22B..01C
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0483 Riparian systems;
- BIOGEOSCIENCESDE: 1820 Floodplain dynamics;
- HYDROLOGYDE: 1856 River channels;
- HYDROLOGY