CHANGES IN SURFACE RUNOFF AND SEDIMENT PRODUCTION AFTER REPEATED RANGELAND BURNS

Prescribed burning of vegetation may increase the potential for surfac e runoff and erosion. Changes in surface runoff and sediment productio n were evaluated with time following fall and spring burns at two diff erent soil and vegetation type locations in southeastern Arizona. Rain fall simulations were conducted immediately after prescribed burns on four replicate areas and 1 yr later following a repeat burn on the sam e areas, and compared with paired unburned areas. The burn treatment a nd evaluation sequence was repeated in a second year on new areas to e valuate differences in years. After the first burn, runoff and sedimen t production on unburned and burned areas were similar within location s, and were greater at one location than the other. One location showe d significantly more runoff and sediment production in the fall season on both unburned and burned areas after the first burn treatment. The re was significantly greater runoff and sediment production from the b urned areas after the second burn and the burned areas were now simila r between locations. Runoff and sediment production for the fall seaso n and for the second year on the 1-yr-old areas was higher at both loc ations, regardless of treatment. The increases in runoff and sediment production were greater from the burning than the season or year effec ts after 1 yr. The management implications for these locations and con ditions are that, immediately after a rangeland burn, runoff and sedim ent production maybe unchanged, but within 1 yr significant increases can occur and significant seasonal and yearly differences may occur ir respective of a burn.