Fuel Moisture, Forest Type, and Lightning-Caused Fire in Yellowstone National Park

The occurrence and behavior of lightning-caused fires in Yellowstone National Park, Wyoming, are evaluated for a 17-yr period (1972-88) during a prescribed natural fire program. Both ignition (occurrence) and spread (stand-replacing fire activity) of fires were strongly influenced by fuel moisture and forest cover type. Fuel moisture estimates of 13% for large (\u3e7.6 cm) dead and downed fuels indicated a threshold below which proportionately more fire starts and increased stand-replacing fire activity were observed. During periods of suitable fuel moisture conditions, fire occurrence and activity were significantly greater than expected in the old-growth, mixed-canopy lodgepole pine (Pinus contorta var. latifolia) and Engelmann spruce/subalpine fir (Picea engelmannii/Abies lasiocarpa) forest types, and significantly less than expected in the successional lodgepole pine forest types. During periods of extended low fuel moisture conditions (drought), sustained high winds significantly reduced the influence of forest cover type on stand-replacing fire activity. These extreme weather conditions were observed during the later stages of the 1988 fire season, and, to a lesser extent, for a short duration during the 1981 fire season. The Douglas fir (Pseudotsuga menziesii) forest type typically supported little stand-replacing fire activity, even though a high frequency of fire starts was observed

EFFECTS OF BROWSING BY NATIVE UNGULATES ON THE SHRUBS IN BIG SAGEBRUSH COMMUNITIES IN YELLOWSTONE NATIONAL PARK

Volume: 55Start Page: 201End Page: 21

Bark beetles, fuels and future fire hazard in contrasting conifer forests of Greater Yellowstone

The extent and severity of bark beetle (Curculionidae: Scolytinae) epidemics and the frequency of large, severe fires have reached unprecedented levels in recent decades, and these trends are expected to continue with ongoing climate change. Insects and fire have tremendous ecological and economic effects in western forests, yet their interactions are poorly understood. We combined field studies and simulation modeling to understand how bark beetle infestation and post-outbreak management affect fire hazard in two widespread but contrasting forest types, lodgepole pine (Pinus contorta) and Douglas-fir (Pseudotsuga menziesii) in the Greater Yellowstone Ecosystem (GYE) in northwestern Wyoming. We directly addressed key barkbeetle research priorities identified by US Forest Service scientists for the western US, via three primary questions and several supplemental studies. (1) How do effects of bark beetle outbreaks on fuel profiles and subsequent fire hazard differ between lodgepole pine and Douglas-fir forests? (2) How was the severity of recent fire in lodgepole pine and Douglas-fir forests affected by prior bark beetle infestation, and does the combination of beetle infestation and fire compromise forest recovery? (3) What post-beetle fuel treatments are likely to change the hazard of subsequent severe fire in lodgepole pine and Douglas-fir forests