Effects of Fire and Vegetation Cover on Hydrological Characteristics of a Mediterranean Shrubland Soil

26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 An experimental study based on the effects of fire on soil hydrology was developed at the Experimental Station of “La Concordia” (Valencia, Spain). It is located on a calcareous hillside facing SSE and composed of nine erosion plots (4 x 20 m). In summer 2003, after eight years of soil and vegetation recovery from previous fires in 1995 (with three fire treatments: T1 high intensity fire, T2 moderate intensity, and T3 not burned), experimental fires of low intensity were again conducted on the plots already burned, to study the effects of repeated fires on the soil water infiltration, soil water content and runoff. Infiltration rates and capacities were measured by the mini-disk infiltrometer method (MDI), assessing the effects of vegetation cover by comparing the under canopy microenvironment (UC) and it ́s absence on bare soil (BS), immediately before and after the fire experiments. Soil properties like water retention capacity (SWRC), and water content (SWC), were also determined for the different fire treatments (T1, T2 and T3) and micro-sites (UC and BS). Hydrological parameters, such as runoff and infiltration rate, were monitored at plot scale from July 2002 to July 2004. In the post-fire period, data displayed a 20% runoff increase and a decrease in infiltration (18%). Differences in the steady-state infiltration rate (SSI) and infiltration capacity (IC) were tested with the MDI on the different treatments (T1, T2 and T3), and between the UC and BS microsites of each treatment. After fire, the SSI of the UC soil declined from 16 mm h to 12 mm h on T1, and from 24 mm h to 19 mm h on T2. The IC was reduced by 2/3 in the T1 UC soil, and by half on T2 UC soil. On the bare soil of T1 and T2, the fire effect was minimal and higher infiltration rates and capacities were reached. Therefore, the presence/absence of vegetation when burnt influenced the post-burnt infiltration patterns at soil microscale. On the T3, different rates and capacities were obtained depending on the microsites (UC and BS),