Dobrowolski et al. Based on the findings of Dobrowolski et al. , one can predict that the aggregation of clays during a fire would increase sand-sized particle percent in the soil and decrease clay content in the upper layers, thus increasing the soil's water capacity. These effects are rather short lived, however, because there is no water loss from the soil due to transpiration, for there are no plants growing in it. The main source for hydrophobic soils are organic compounds that coat the soil particles. The theory is that aliphatic hydrocarbons become polarized and attach more readily to the soil grains.
Different factors affect the degree of water repellency in a soil.
Direct raindrop impact can also create slake, which will create a temporary sealing layer on top of a soil and thus affect the degree to which it is hydrophobic. Many of the hydrologic affects of fires on soils can increase the erodability of soils. First, the lack of vegetation influences the variability of stream flow in burned areas. These changes in stream flow can create times of very high energy in stream beds that have high erosion rates. In addition, fires can breakdown peds in soils and, as mentioned earlier, create sand-sized aggregates of the clays.