MORPHOLOGICAL RESPONSE OF SMALL WATERSHEDS IN THE SOUTHWESTERN OAK-SAVANNAS TO WARM AND COOL SEASON PRESCRIBED FIRE: PELONCILLO MOUNTAINS, NM

Oak-savannas comprise over 80,000 km² of the southwestern United States and northern Mexico. However, there is a paucity of data to assist in the management of these lands. Fire, which was once the most important natural disturbance in this system, has been excluded due to past over-grazing and fire suppression practices. Prescribed fire is one management technique to restore natural processes within southwestern oak-savannas by reducing woody species density, increasing herbaceous plant production, and creating vegetative mosaics on the landscape. However, questions concerning the seasonality of burn treatments and the overall effects of these treatments on physical and ecological processes need to be addressed prior to broad management application. The Cascabel Watershed Study is a collaborative effort between multiple government agencies, universities, local land managers, and environmental interest groups to evaluate the impacts of warm and cool season burn treatments on an array of ecosystem processes. The 182.6 ha study area is located on the Coronado National Forest in the eastern Peloncillo Mountains, New Mexico at about the 1,640 m elevation. It consists of 12 small watersheds each with a series of channel cross-sections to evaluate morphology throughout the reach. The parent material is fine-grained Tertiary rhyolite that is part of an extensive lava field that was formed about 25 to 27 M ybp. A US Forest Service soil survey in the area classified 45% of the soils as Typic Haplustolls, coarse-loamy, mixed, mesic, 25% as Typic Haplustalfs, and 15% rock outcrops. Here, we evaluate within-channel processes to determine whether or not either of the burn treatments applied, or the wildfire that ensued following the warm season treatment, have a significant effect on channel morphology and overall sediment production. Initial results indicate that burn treatments have not had a discernable impact on basin morphology across the 12 watersheds.