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| Titel |
Effects of Post-fire Salvage Logging on Soil Water Repellency |
| VerfasserIn |
Lee MacDonald, Robert Coats, Peter Robichaud, Joseph Wagenbrenner, Robert Brown |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250057402
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| Zusammenfassung |
| Post-fire soil water repellency (SWR) is often cited as a key cause of the large increases in
surface runoff and erosion after high-severity fires. Post-fire salvage logging is an important
management option, but little is known about how logging or other types of site
disturbance affect SWR, infiltration, and sediment yields. The objectives of this paper
are to: (1) determine how two different types of logging tracks affect SWR; (2)
compare results from two techniques for assessing SWR; and (3) assess how the
changes in SWR due to salvage logging affect infiltration and sediment yields. The
primary study site was the 14,000 ha Red Eagle Fire in northern Montana USA, which
burned a dense mixed coniferous forest in September 2006 and was partially logged
in early summer 2007. Precipitation falls mostly as snow with some occasional
summer rainstorms, so data were collected from summer 2007 through summer
2009.
The basic study design compared data from burned control sites to lightly-traveled
feller-buncher tracks, more heavily-trafficked skid tracks, and logged convergent
hillslopes (“swales”). SWR was measured at 2-cm intervals using the water drop
penetration time (WDPT) and critical surface tension (CST), but both methods
were not necessarily used at all sites for each year. Compaction was measured with
a pocket penetrometer in 2007 and 2009, and infiltration was assessed using the
mini-disk tension infiltrometer (MDI). Sediment yields were measured with sediment
fences.
In 2007 there was significantly less SWR in the logging tracks than the adjacent points
outside the tracks. SWR was slightly stronger in 2008, presumably due to drier soil
conditions. SWR significantly decreased from 2008 to 2009 in the more heavily trafficked
skid tracks, and in 2009 the skid tracks were again less repellent than the areas
adjacent to the tracks and the control plots. SWR also was lower in the logged than
the unlogged swales. These results indicate that the disturbance due to logging
generally decreased SWR, particularly in the more trafficked areas, but the high
variability made it difficult to detect significant differences, particularly for the
WDPT.
Both types of logging tracks were significantly more compacted than the adjacent areas,
and this compaction was stronger and more persistent in the skid tracks than the
feller-buncher tracks. Infiltration significantly increased over time outside of the tracked areas
but not in the tracks. There were no significant differences in infiltration between the tracked
and untracked areas within years, possibly because the compaction in the tracks compensated
for the reduction in SWR. Sediment yields in the tracks and logged swales were at least an
order of magnitude higher than the controls. Sediment yields decreased with increasing
SWR because the logging tracks had significantly less SWR. Multivariate analysis
indicated that sediment yields are more closely related to percent ground cover
rather than SWR. These results indicate that the disturbance due to salvage logging
can reduce SWR, but the associated compaction and reduction in surface cover
are more persistent and detrimental than any potential benefit due to lower SWR. |
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