THE EFFECTS OF LOGGING BURNED WOOD ON SOIL EROSION RATES, A PRELIMINARY STUDY

In response to the hotly-debated question about whether or not salvage lumbering should be allowed in badly-burned areas of the National Forest 2002 Rodeo-Chediski Fire, Arizona, sediment run-off in logged, un-logged and unburned sites were collected and compared. Numerous variables were measured: vegetation, quantity of litter, presence/absence of rocks, rainfall, slope, drainage area and subsequent treatment of area. These variables were analyzed against the amount of sediment collected by silt-fences erected in each area. Tentative results indicate that logging has little effect on erosion rates, but that the degree of slope and the presence or absence of rocks in the area does.

Winter of 2003-2004 showed erosion rate differences between the unburned sites (1kg/h/yr to 21 kg/h/yr) and the burned sites (65 kg/h/yr to 3,985 kg/h/yr), none of which were logged at this time. The burned-unlogged sites together showed an average erosion rate of 152.7 times higher than the unburned control sites. Summer erosion rates for 2004 also showed a similar difference between the unburned sites (134 kg/h/yr to 349 kg/h/yr) and burned-unlogged (30,493 kg/h/yr to 86,935 kg/h/yr). However, the data portrayed no significant difference between the erosion rates of the burned-unlogged and the burned-logged (3,208 kg/h/yr to 44,803 kg/h/yr). The burned sites (burned-unlogged and burned-logged) on average had an erosion rate 156.7 times higher than the unburned sites. In every case, the summer erosion rates were much higher than the winter rates. In the unburned control sites, the range was from 11.3 to 134 times higher. In the burned sites, the range was from 21.8 to 469.1 times.