 |
| Titel |
Post-fire Vegetation regeneration effects on runoff and sediment yield: slope, aspect and fire severityPost-fire Vegetation regeneration effects on runoff and sediment yield: slope, aspect and fire severity |
| VerfasserIn |
R. Barzilai, L. Wittenberg, D. Malkinson |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029304
|
|
|
|
|
|
| Zusammenfassung |
| 1 Post-fire Vegetation regeneration effects on runoff and sediment yield: slope, aspect
and fire severity
During the last several decades fire occurrence at the Carmel Mountain ridge has been
increasing, showing similar trends to the ones observed in the Mediterranean basin.
Wildfires damage and destroy the vegetation and therefore alter the components of
the eco-geomorphic system, which leads to an increase in runoff and sediment
yields.
In April, 2005 a wildfire consuming 154 ha of planted and natural vegetation occurred at
the north-western part of the Carmel ridge. Following the event, a 2x2x2 factorial design of
monitoring plots was established to examine the relationship between vegetation
recovery, runoff and sediment yield. Namely, slope aspect, slope steepness and fire
severity were specifically examined in relation to the above mentioned response
variables.
The research methods included (a) the establishment of 14 plots of ~ 10.5m2 each,
designed for runoff and sediment collection and for monitoring vegetation cover change. (b)
Monthly aerial photography of the research plots using a pole-mounted camera. The
images were digitally classified to identify rock cover, vegetation cover, and bare soil
patches. The time dependent vegetation regeneration was used for assessing landscape
recovery. (c) Collection of runoff and sediment yield after each rain event. Multiple
regression analysis was conducted in order to determine the relative importance of
land cover classes and different precipitation parameters on runoff and sediment
yield.
Vegetation recovery rates during the first wet season were relatively low; by the
end of the first spring season vegetation cover reached 30%-35%. During the first
summer, a year after the fire, there was a slight decrease in vegetation cover, due to the
die off of the annual herbaceous vegetation. In the second winter vegetation cover
continued to increase, and by the end of the research period (summer 2007) average
vegetation cover of all plots reached 61.7%. Results indicate that runoff and sediment
yields in southern aspect areas, on steep slopes or after high severity fires, were
significantly higher than runoff and sediment yields in northern aspect areas, on the
moderate slopes or after low fire severity, respectively. Results also show that between
the first and second rain seasons after the wildfire, runoff yield did not decrease
significantly, while sediment yield did. It has been found that the main factors influencing
runoff yield during these seasons were the amount of precipitation and rain intensity
(I10-
6).
Results of the analysis of the sediment-generating mechanisms show that the vegetation
and soil cover were the main factors that were correlated with the decreasing amounts of
sediment yields. By the end of the first wet season and the beginning of the second one,
sediment yields decreased in some cases by an order of magnitude and more. In the southern
aspect, where vegetation cover increased from 26.4% to 33.7%, sediment yield diminished by
an order of magnitude.
While sediment yield responded to changes of vegetation cover, as has been
widely observed in other studies, runoff coefficients did not decrease during the
second season, contrasting our expectations. We propose that this pattern may be
explained by the rapid regeneration of the herbaceous vegetation, which may act as a
land cover feature impeding particle movement, but facilitates surface sheet flow. |
|
|
|
|
|
|