HR: 08:00h
AN: H51M-01    [Abstracts]
TI: Differential Recovery Rates of Post Fire Runoff and Erosion: The Effects of Slope, Aspect and Vegetation
AU: * Wittenberg, L
EM: leaw@geo.haifa.ac.il
AF: Dept. of Geography and Environmental Studies University of Haifa, Mount Carmel, Haifa, 31905, Israel
AU: Malkinson, D
EM: dmalk@geo.haifa.ac.il
AF: Dept. of Geography and Environmental Studies University of Haifa, Mount Carmel, Haifa, 31905, Israel
AU: Malkinson, D
EM: dmalk@geo.haifa.ac.il
AF: The Golan Research Institute, University of Haifa, Sheizaf 3, Katzrin, 12900, Israel
AU: Barzilai, R
EM: ronel.b@gmail.com
AF: Dept. of Geography and Environmental Studies University of Haifa, Mount Carmel, Haifa, 31905, Israel
AB: Response of natural ecosystems in Mediterranean regions to wildfires has been extensively studied, particularly in context with the relationship of vegetation denudation and runoff/erosion processes. Following a 120 ha wildfire that took place during April 2005, at the Carmel Mountain ridge, we constructed monitoring plots to assess vegetation dynamics, runoff and erosion rates. Post-fire runoff and sediment were collected after each rain event for two rainy seasons from 14 plots (~10 m ²) located in different physio-geographic settings. Changes in vegetation cover were monitored by taking "aerial photographs" of the plots, using a digital camera mounted on a 6 m pole. Images were rectified and classified using image analysis software, and GIS layers of the vegetation cover were generated. These three factors: vegetation cover, runoff and erosion were assessed against slope aspect (north vs. south), slope steepness (steep vs. moderate), and fire severity (low vs. high). Results indicated differential spatio-temporal changes in erosion, runoff and vegetation growth. By the end of the second winter percentage of vegetation cover was comparable with non-burned control plots. Vegetation in the burnt plots, however, was predominated by herbaceous cover, in contrast to woody vegetation in the control plots. Vegetation cover was significantly higher in north facing slopes compared to south facing ones. Both sediment and runoff yields were significantly higher on south facing slopes, steep slopes and high-severity burnt areas. Sediment yield decreased during the second year, and was correlated with the increase in vegetation cover (or the reciprocal decrease in exposed stoniness). In contrast to other studies, cumulative runoff yields were not lower during the second rain season compared to the first one, though runoff coefficients slightly decreased, but insignificantly; we attribute this to the presence of predominantly herbaceous vegetation. The sharp decrease in sediment yield was not proportional to the modest decrease in runoff rates. On south facing, steep slopes and severely burnt plots runoff values were correlated with maximum I _{10 min} rain intensity, while on north facing moderate slopes and low-severity burnt plots runoff was correlated with the amount of precipitation during a given event. We suggest that in steep and south facing slopes Hortonian processes dictate runoff generation, while at moderate and north facing slopes runoff generation is governed by non-Hortonian processes. Differential fire effects on various the physio-geographic settings resulted in different predominating runoff mechanisms which have implications for recovery processes of the burnt landscape.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1815 Erosion
DE: 1851 Plant ecology (0476)
SC: Hydrology [H]
MN: 2007 Fall Meeting