Digging by vertebrates as an activity promoting the development of water-repellent patches in sub-surface soil

Dry sclerophyll woodlands in south-western Australia are refugia for remnant populations of woyliesBettongia penicillata . These marsupials create holes as they forage for the fruiting bodies of hypogeous fungi. The effect of these holes on the water-repellent woodland soils was evaluated using simulated diggings. Water repellency was significantly higher in surface than in sub-surface soils, although patches of moderately water-repellent sub-soils did occur. In situ assessments of simulated diggings that were allowed to decay showed a five-fold increase in water repellency in sub-surface soil once they had become filled-in. Buried organic material was found in many decayed diggings that were severely water-repellent, and very severe water repellency occurred where masses of fungal hyphae were present. This suggests that vertebrate diggings in which surface litter and organic debris become trapped can provide a site for the development of sub-surface water repellency