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

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Songbird response to increased willow (Salix spp.) growth in Yellowstone's northern range

Abstract. After nearly a century of height suppression, willows (Salix spp.) in the northern range of Yellowstone National Park, USA, are increasing in height growth as a possible consequence of wolf (Canis lupus) restoration, climate change, or other factors. Regardless of the drivers, the recent release of this rare but important habitat type could have significant implications for associated songbirds that are exhibiting declines in the region. Our objective was to evaluate bird response to releasing willows by comparing willow structure and bird community composition across three willow growth conditions: height suppressed, recently released, and previously tall (i.e., tall prior to the height increase of released willows). Released and previously tall willows exhibited high and similar vertical structure, but released willows were significantly lower in horizontal structure. Suppressed willows were significantly shorter and lower in horizontal cover than released or previously tall willows. Bird richness increased along a gradient from lowest in suppressed to highest in previously tall willows, but abundance and diversity were similar between released and previously tall willows, despite lower horizontal cover in the released condition. Common Yellowthroat (Geothlypis trichas) and Lincoln's Sparrow (Melospiza lincolnii ) were found in all three growth conditions; however, Yellow Warbler (Dendroica petechia), Warbling Vireo (Vireo gilvus), Willow Flycatcher (Empidonax traillii ), and Song Sparrow (Melospiza melodii ) were present in released and previously tall willows only. Wilson's Warbler (Wilsonia pusilla) was found in previously tall willows only, appearing to specialize on tall, dense willows. The results of our a priori habitat models indicated that foliage height diversity was the primary driver of bird richness, abundance, and diversity. These results indicate that vertical structure was a more important driver of bird community variables than horizontal structure and that riparian and willowdependent bird species have responded positively to increased willow growth in the region

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

Appendix A. Bird species observed in suppressed, released, and previously tall growth conditions in and around Yellowstone National Park's northern range.

Bird species observed in suppressed, released, and previously tall growth conditions in and around Yellowstone National Park's northern range

Phosphodiesterase 4 inhibition attenuates atrial natriuretic peptide-induced vascular hyperpermeability and loss of plasma volume

Inhibition of phosphodiesterase 4 (PDE4) to increase endothelial cAMP and stabilize the endothelial barrier attenuates acute inflammatory increases in vascular permeability. We extended this approach to attenuate physiological increases in vascular permeability in response to atrial natriuretic peptide (ANP), which acts with the kidney to regulate plasma volume. We measured blood-to-tissue albumin clearance and changes in plasma volume in isoflurane-anaesthetized mice (C57BL/6J) pre-treated with rolipram (8 mg kg−1i.p., 30 min). Rolipram significantly reduced albumin permeability, measured using a dual-label fluorescence method, in skin and skeletal muscle compared with ANP alone (500 ng kg−1 min−1). Skin and muscle tissue accounted for 70% of the reduction in whole body albumin clearance taking into account albumin clearance in gastrointestinal (GI) tissue, heart and kidney. The action of ANP and rolipram to modify albumin clearances in duodenum and jejunum could be accounted for by local increases in vascular perfusion to increase surface area for exchange. ANP increased haematocrit from 40.6% to 46.8%, corresponding to an average loss of 22% plasma fluid volume (227 μl), and this was almost completely reversed with rolipram. Renal water excretion accounted for less than 30% of plasma fluid loss indicating that reduced albumin permeability and reduced filtration into vasodilated GI tissue were the predominant actions of PDE4 inhibition. Similar fluid retention was measured in mice with endothelial-restricted deletion of the guanylyl cyclase-A receptor for ANP. Stabilizing the endothelial barrier to offset ANP-induced increases in vascular permeability may be part of a strategy to maintain plasma volume