Influence Of Fuel Reduction Alternatives On Forest Soil Properties And The Carbon Cycle
Project Description
Woody shrubs invading forest lands following fire create major problems in urban/wildland interfaces of the West. Aggressive woody shrubs not only weaken forest trees and delay the return of forest cover, they also lead to a continuous fuel buildup between the ground and tree canopy, thus creating a high risk of catastrophic losses from recurrent fire. The traditional means of dealing with fuel buildup -prescribed fire - is impractical in a mosaic of wildlands and residential holdings. Furthermore, prescribed fire leads to gaseous losses of carbon and nitrogen which may lower soil quality. Alternative means must be found that reduce fuel loads of woody shrubs, retain organic carbon and nitrogen on the site, and enhance soil properties associated with soil stability, water supply, and nutrient availability.
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Principal
Investigator(s) |
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Dale Johnson, Professor of Forest Soil Chemistry, Natural Resources & Environmental Science,
College of Agriculture, Biotechnology, and Natural Resources. dwj@cabnr.unr.edu
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| Participants | Robert F. Powers, USFS |
| Project Focus |
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Earth Science
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Terrestrial Life
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Fire
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Updated: 12/20/2004
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Wildfire Effects On A Sierran Forest Soil: Setting A New Trajectory For Ecosystem Development
Project Description
We have recently been assessing the effects of wildfire on long-term nutrient budgets at a former burn site (1981) near Little Valley, Nevada. From measurements of stumps, present-day biomass, and nutrient inventories both in nearby unburned forests and in the shrub ecosystem now occupying the site, we have reconstructed pre-fire carbon and nutrient contents, estimated losses, and calculated the redistribution of nutrients due to the wildfire. Results suggest that losses of C from the site were dominated by post-fire salvage logging rather than direct combustion whereas the reverse was true for N. Results also indicate that N losses were completely replenished within 20 years through N fixation by Ceanothus vefutinus. Large differences in soil exchangeable Ca and Mg were observed 20 years after the fire, in contrast to some other studies where increases in exchangeable base canons after fire were short-term. Furthermore, the apparent enrichment of exchangeable Ca due to the fire far exceeded estimates of Ca contents in vegetation and forest floor before the fire. We hypothesize that a large proportion of the exchangeable Ca enrichment was due to a combination of Ca release from disintegration/dissolution of soil minerals and from organically-bound Ca in soils. Some research has shown that soil minerals can be decomposed during fire, but nutrient budgets routinely ignore organic Ca, Mg, and K pools in soils, focusing instead only on the exchangeable and mineral phases. One of the greatest sources of uncertainty in reconstructing nutrient budgets after wildfire is the change in soil nutrient fractions. It can be safely assumed in this region that all foliage and forest floor 2 components are consumed by intense stand-replacing wildfires, but assessing the organic matter combustion in soils is problematic.
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Principal
Investigator(s) |
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Dale Johnson, Professor of Forest Soil Chemistry, Natural Resources & Environmental Science,
College of Agriculture, Biotechnology, and Natural Resources. dwj@cabnr.unr.edu
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W. Wally Miller, Professor of Soils and Hydrology, Natural Resources & Environmental Science,
College of Agriculture, Biotechnology, and Natural Resources. wilymalr@cabnr.unr.edu
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| Project Focus |
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Earth Science
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Terrestrial Life
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Fire
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Updated: 12/20/2004
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Wildfire In A Sierran Forest: Setting A New Trajectory for Ecosystem Development
Project Description
Catastrophic wildfire is increasing in forests of the Sierra Nevada and throughout the western US because of misguided policies of total fire suppression in the past. We hypothesize that wildfire resets the clock and establishes a new trajectory for ecosystem development in terms of carbon and nutrient cycling. Studies of wildfire are often plagued with uncertainties because of the lack of suitable control sites and pre-treatment sampling. We have an unparalleled opportunity to study the before and after effects of a recent wildfire in the Lake Tahoe Basin in Nevada. Nine of sixteen replicated plots previously laid out and sampled for a prescribed fire and harvesting study burned in an accidental wildfire set on 3 July 2002. Data from this site will allow us to test assumptions and algorithms previously used to reconstruct carbon and nutrient budgets on pre-existing wildfires and in extrapolating these results over the landscape. We propose to assess the effects of this wildfire on soil nutrient status, water quality, vegetation regrowth, carbon and nutrient budgets. Water quality measurements will include soil solution and surface runoff collections; soils and regenerating vegetation will be resampled twice during this study. We will extrapolate these results in time and space using a combination of simulation modeling and assessment of historic fire regimes in the region. This project will produce refereed journal publications and presentations at national meetings, outreach in the form of tours and class field trips, and the website will be updated with new information frequently. The project will employ several undergraduate students as hourly student employees and two graduate students as research assistants/interns dedicated to field data collection, laboratory analyses, data management, and information retrieval.
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Principal
Investigator(s) |
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Dale Johnson, Professor of Forest Soil Chemistry, Natural Resources & Environmental Science,
College of Agriculture, Biotechnology, and Natural Resources. dwj@cabnr.unr.edu
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W. Wally Miller, Professor of Soils and Hydrology, Natural Resources & Environmental Science,
College of Agriculture, Biotechnology, and Natural Resources. wilymalr@cabnr.unr.edu
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Roger F. Walker, Professor of Forestry, Natural Resources & Environmental Science,
College of Agriculture, Biotechnology, and Natural Resources. walker@cabnr.unr.edu
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| Project Duration | 7/1/2004 - 6/30/2007 |
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Earth Science
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Terrestrial Life
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Fire
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Updated: 3/3/2005
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