Effects of fuels treatments and wildfire on understory species and fuels in the ponderosa pine zone of the Colorado Front Range

The first clear indication that unnaturally dense forest conditions existed in ponderosa pine – Douglas-fir forests of the Colorado Front Range was the Buffalo Creek Fire, a large, catastrophic wildfire that burned in 1996. Ongoing research in the Front Range indicated that the Buffalo Creek Fire likely would have burned very differently under pre-settlement forest conditions; early photographs and written descriptions, as well as fire history and stand reconstruction data, all suggested that historically these forests were characterized by a matrix of low-density forests and shrubland or grassland openings that was created and maintained by a mixed-severity fire regime. As a result of the Buffalo Creek Fire and several other large and intense wildfires in the Colorado Front Range – Bobcat Gulch and Hi Meadows in 2000, and Schoonover, Snaking, and Hayman in 2002 – managers began to plan forest restoration treatments to reduce the risk of unnaturally large, stand-replacing fires, and to return ecological sustainability to the landscape through research-guided restoration actions. Managers and others are obviously concerned about how both forest restoration treatments and intense wildfires impact the forest overstory, and these impacts are widely studied. Less studied, though, are how these disturbances impact the forest floor – in terms of both understory species composition and surface fuels that would carry a future fire. As wildfires continue to occur in the Front Range, and as forest restoration treatments continue to expand to much larger land areas, it is becoming critical for forest managers to understand how both restoration actions and wildfire influence forest understories and fuel loadings. Our objective for this project was to conduct a holistic ecosystem evaluation of the changes in forest understory communities, fuel characteristics, and potential fire behavior that result from restoration activities and wildfires. To address this objective, we established one study area within a recently treated forest, one study area within a forest recently burned by wildfire, and three study areas within untreated, unburned reference forests. All study areas were located within the Upper South Platte Watershed of the Pike National Forest, Colorado, USA, approximately 60 km southwest of Denver. Our treated study area was located in an area that was mechanically thinned in late 2002 and early 2003. The primary management objective was to reduce the risk of crown fires and to restore sustainable and ecologically appropriate overstory conditions by decreasing stand density, minimizing fuel ladders, and increasing canopy openings. Small canopy trees were sheared near ground-level using a boom-mounted hot saw on a tracked vehicle. Downed tree tops and limbs were crushed and further broken apart by driving over them with the tracked vehicle. In early 2003, where terrain and financial resources permitted, hand crews used chain saws to create additional openings and further reduce basal areas. The hand-cut trees were subsequently cut-to-length, piled, and burned. Our wildfire study area was located within the Hayman Fire, which burned 55,800 ha in 2002. Approximately half of the Hayman Fire area burned as a stand-replacing crown fire, much of it in a single day of extreme weather. The other half of the area burned as a mixed-severity fire, creating a mosaic of burn severities on the landscape. Our study area was situated in a transitional zone between these two fire behaviors, and therefore contained components of each. Three reference study areas were established near the treated and wildfire study areas to provide information about the untreated and unburned condition. The reference sites had not been disturbed by fire or other agents in the preceding five years. Each study area contained fifteen 0.1-ha plots, which were stratified by aspect (north, south, and east/west) to minimize the potential effects of topography on our findings. In each plot we measured understory species composition and cover, surface fuel loading, and overstory structure. Understory data were measured in all plots in 2004, 2005, and 2006, while surface fuels and overstory data were generally only measured in one of the three years. Prefire understory, surface fuel, and overstory data collected in 1997 were also available for the Hayman Fire plots

Aquilegia, Vol. 30 No. 1, January-February 2006: Newsletter of the Colorado Native Plant Society

https://epublications.regis.edu/aquilegia/1115/thumbnail.jp

Lodgepole pine management guidelines for land managers in the wildland-urban interface

As a consequence of the current mountain pine beetle epidemic, many landowners and land managers are concerned about how to actively manage lodgepole pine stands. The following guidelines cover treating the dead standing trees killed by the insects, protecting homes and communities from wildfire, and ensuring that the future forest is better structured to prevent widespread mortality from insect epidemics and wildfire

Vasodilator factors in the systemic and local adaptations to pregnancy

We postulate that an orchestrated network composed of various vasodilatory systems participates in the systemic and local hemodynamic adaptations in pregnancy. The temporal patterns of increase in the circulating and urinary levels of five vasodilator factors/systems, prostacyclin, nitric oxide, kallikrein, angiotensin-(1–7) and VEGF, in normal pregnant women and animals, as well as the changes observed in preeclamptic pregnancies support their functional role in maintaining normotension by opposing the vasoconstrictor systems. In addition, the expression of these vasodilators in the different trophoblastic subtypes in various species supports their role in the transformation of the uterine arteries. Moreover, their expression in the fetal endothelium and in the syncytiotrophoblast in humans, rats and guinea-pigs, favour their participation in maintaining the uteroplacental circulation. The findings that sustain the functional associations of the various vasodilators, and their participation by endocrine, paracrine and autocrine regulation of the systemic and local vasoactive changes of pregnancy are abundant and compelling. However, further elucidation of the role of the various players is hampered by methodological problems. Among these difficulties is the complexity of the interactions between the different factors, the likelihood that experimental alterations induced in one system may be compensated by the other players of the network, and the possibility that data obtained by manipulating single factors in vitro or in animal studies may be difficult to translate to the human. In addition, the impossibility of sampling the uteroplacental interface along normal pregnancy precludes obtaining longitudinal profiles of the various players. Nevertheless, the possibility of improving maternal blood pressure regulation, trophoblast invasion and uteroplacental flow by enhancing vasodilation (e.g. L-arginine, NO donors, VEGF transfection) deserves unravelling the intricate association of vasoactive factors and the systemic and local adaptations to pregnancy

BMQ

BMQ: Boston Medical Quarterly was published from 1950-1966 by the Boston University School of Medicine and the Massachusetts Memorial Hospitals