Effects of three mulch treatments on initial postfire erosion in north-central Arizona

Mulching after wildfires is a common treatment designed to protect bare ground from raindrop impact and reduce subsequent erosion. We tested the effectiveness of three mulching methods on the Indian Fire near Prescott, Arizona, USA. The first method felled all fire-killed trees, chipped the logs and limbs, and spread the chips across the hillslope with a mobile selffeeding chipper. The second treatment spread compressed, tackified straw pellets that expand when wetted and release a soil flocculant. The third treatment was rice straw applied at 4.5 Mg ha-1 (2 tons ac-1). Each treatment was applied to a small catchment with a silt fence sediment trap at the mouth. Sediment yield from an untreated (control) catchment was also measured. The treatments were tested by three erosion-causing summer rain events. The chipping treatment and the pellets reduced sediment yield by 80 to 100 percent compared to the control in the first two storms. In the third event, a multi-day storm followed by an intense thunderstorm, the pellets and straw reduced sediment yield 42 and 81 percent, respectively. The effectiveness of the chip treatment could not be completely assessed because of partial failure of the sediment fence. Vegetation cover was low on all sites; ground cover from pellets decreased more than did straw or chips by mid-October, probably accounting for the lower effectiveness in reducing erosion compared to straw.