Fire severity and surface rock fragments cause patchy distribution of soil water repellency and infiltration rates after burning

Abstract

Although fire-induced soil water repellency (SWR) and its effects on soil hydrology and geomorphology have been studied in detail, very few studies have considered the effect of rock fragments resting on the soil surface or partly embedded in soil. In this research, we have studied the effect of rock fragments on the strength and spatial distribution of fire-induced SWR at different fire severities. A fireaffected area was selected for this experiment and classified into different zones according to fire severity (unburned, low, moderate and high) and rock fragment cover (low, <20% and high, >60%). During 7 days after fire, SWR and infiltration rates were assessed in the soil surface covered by individual rock fragments and in the midpoint between two adjacent rock fragments (with maximum spacing of 20 cm). SWR increased with fire severity. Rock fragments resting on the soil surface increased the heterogeneity of the spatial distribution of fire-induced SWR. SWR increased significantly with rock fragment cover in bare areas under moderate and high fire severity, but quantitatively important changes were only observed under high fire severity. In areas with a low rock fragment cover, water repellency from soil surfaces covered by rock fragments increased relative to bare soil surfaces, with increasing SWR. In areas with a high rock fragment cover, SWR increased significantly from non-covered to covered soil surfaces only after low-severity burning. Rock fragment cover did not affect infiltration rates, although it decreased significantly in soil surfaces after high-severity burning in areas under low and high rock fragment cover.

Effects of rock fragment cover on hydrological processes under rainfall simulation in a semi‐arid region of China

“…The effects of different rock fragment cover treatments on soil loss are shown in Table . Soil loss decreased with increasing rock fragment coverages in cases where rock fragments were resting on the soil surface, which was comparable to previous results (Fang, Shi, Chen, Zhang, & Wang, ; Gordillo‐Rivero, García‐Moreno, Jordán, Zavala, & Granja‐Martins, ). The mean soil loss rate was small (5.5 g m −2 min −1 ) for RL when R c = 40%, which was much less than that in bare land (10.8 g m −2 min −1 ).…”

How wildfires affect soil properties. A brief review

“…At 800 o C, water repellency begins to diminish after only 10 minutes and is completely destroyed after 20 minutes, while soil renders completely wettable after only 10 minutes at 900 o C (DeBano and Krammes, 1966). Field studies have shown that rock fragments on the soil surface cause an heterogeneous pattern of temperature gradients, which contribute to enhance and/or destroy water repellency (Gordillo-Rivero et al, 2013).…”

Glomalin‐related Soil Protein Response to Heating Temperature: A Laboratory Approach

“…However, the relationship between SWR response and temperature is not as easy as it appears. SWR development, induction, enhancement or decrease, depends on many other factors such as the nature of atmospheric heating (Bryant et al, 2005), the quantity and quality of soil organic matter content, soil moisture (Doerr et al, 2000), soil texture (Arcenegui et al, 2007), mineralogy of clay fraction (Mataix-Solera et al, 2008) or even rock fragments (Gordillo-Rivero et al, 2014). In our case, SWR increased at low temperatures when natural SWR was initially present and was mainly caused by the high SOC content (Gata and Aitana samples, clay and clay loam soils, respectively).…”