Tree species demographics and dynamics in the native forest at Wondo Genet College of Forestry and Natural Resource Management, central Ethiopia

The extent and ecological integrity of native forests in Ethiopia have been greatly diminished during the past century. Native forests continue to be threatened by conversion to agricultural fields or plantations of non-native tree species, by excessive harvesting and wood collection, and by climate change. Due to a paucity of research, we know little about the ecology of most native forest species, about the overall dynamics of native forest communities, or about the capacity of individual native tree species to respond to current and future threats. A group of students and faculty at Wondo Genet College of Forestry and Natural Resource Management in central Ethiopia examined the demography of two common tree species in a 8-ha tract of native forest located on the College campus. Numbers and diameters of Podocarpus falcatus and Croton macrostachus were tallied in six 200-600 m2 plots. The size class distribution of Podocarpus resembled an inverse J form, with a preponderance of smaller stems but some large individuals up to 226 cm dbh--indicative of a relatively stable population capable of regenerating beneath the established forest canopy. In contrast, most Croton were 20-50 cm dbh, with only a few larger or smaller individuals--reflecting a discrete pulse of regeneration, probably following a local disturbance that created gaps in the forest canopy. These results suggest that the shade-intolerant Croton is more resilient to clearing or harvesting than is the shade-tolerant Podocarpus. However, key questions remain, notably the date and nature of the disturbance that produced this documented pulse of Croton regeneration, the optimal and maximum size of opening can be colonized by Croton, and whether Podocarpus regeneration is restricted to intact canopy settings (as suggested by these findings) or if this species can regenerate in openings as well.National Science Foundation

Bringing back the Kaibab deer story: A complete case study for land stewardship

The classic story of predator control, deer population explosion, and habitat degradation on the Kaibab Plateau was a cornerstone of population ecology and natural resources through the 1960s. The story has almost disappeared from natural resources, following several papers in the 1970s that questioned the quality of the evidence and the truth of the overall story. We reexamined the classic story from the viewpoint of habitat impacts of large deer populations; if the story were true, aspen regeneration should have been severely reduced in the 1920s. We also evaluated other lines of evidence, including the secondary irruption of the deer population in the 1950s

The interaction of fire, fuels, and climate across Rocky Mountain forests

Understanding the relative influence of fuels and climate on wildfires across the Rocky Mountains is necessary to predict how fires may respond to a changing climate and to define effective fuel management approaches to controlling wildfire in this increasingly populated region. The idea that decades of fire suppression have promoted unnatural fuel accumulation and subsequent unprecedentedly large, severe wildfires across western forests has been developed primarily from studies of dry ponderosa pine forests. However, this model is being applied uncritically across Rocky Mountain forests (e.g., in the Healthy Forests Restoration Act).We synthesize current research and summarize lessons learned from recent large wildfires (the Yellowstone, Rodeo-Chediski, and Hayman fires), which represent case studies of the potential effectiveness of fuel reduction across a range of major forest types. A “one size fits all” approach to reducing wildfire hazards in the Rocky Mountain region is unlikely to be effective and may produce collateral damage in some places.Keywords: Fire ecology, Climate, Rocky Mountain forests, Forest health, Forest managementKeywords: Fire ecology, Climate, Rocky Mountain forests, Forest health, Forest managemen

The interaction of fire, fuels, and climate across Rocky Mountain forests

Understanding the relative influence of fuels and climate on wildfires across the Rocky Mountains is necessary to predict how fires may respond to a changing climate and to define effective fuel management approaches to controlling wildfire in this increasingly populated region. The idea that decades of fire suppression have promoted unnatural fuel accumulation and subsequent unprecedentedly large, severe wildfires across western forests has been developed primarily from studies of dry ponderosa pine forests. However, this model is being applied uncritically across Rocky Mountain forests (e.g., in the Healthy Forests Restoration Act). We synthesize current research and summarize lessons learned from recent large wildfires (the Yellowstone, Rodeo-Chediski, and Hayman fires), which represent case studies of the potential effectiveness of fuel reduction across a range of major forest types. A “one size fits all” approach to reducing wildfire hazards in the Rocky Mountain region is unlikely to be effective and may produce collateral damage in some places.Keywords: climate, forest health, Rocky Mountain forests, forest management, fire ecolog

Historical and modern disturbance regimes of pinon-juniper vegetation in the Western U.S.

Pinon-juniper vegetation covers some 100 million acres in the western U.S. where it provides economic products, ecosystem services, biodiversity, and aesthetic beauty in some of the most scenic landscapes of North America. There are concerns, however, that the ecological dynamics of pinon-juniper woodlands have changed since Euro-American settlement, that trees are growing unnaturally dense, and that woodlands are encroaching into former grasslands and shrublands. Yet surprisingly little research has been conducted on historical conditions and ecological processes in pinon-juniper vegetation, and the research that does exist demonstrates that pinon-juniper structure, composition, and disturbance regimes were very diverse historically as well as today. The purpose of this report is to briefly summarize our current understanding of historical stand structures, disturbance regimes, and landscape dynamics in pinon-juniper vegetation throughout the western U.S. The authors gathered for a workshop in Boulder, CO, on August 22-24, 2006, to develop the information presented here

Associations between COPD related manifestations:a cross-sectional study

Background: Cardiovascular disease, osteoporosis and emphysema are associated with COPD. Associations between these factors and whether they predict all-cause mortality in COPD patients are not well understood. Therefore, we examined associations between markers of cardiovascular disease (coronary artery calcification [CAC], thoracic aortic calcification [TAC] and arterial stiffness), bone density (bone attenuation of the thoracic vertebrae), emphysema (PI-950 and 15th percentile) and all-cause mortality in a COPD cohort. Methods: We assessed CAC, TAC, bone attenuation of the thoracic vertebrae, PI-950 and 15th percentile on low-dose chest computed tomography in COPD subjects. We measured arterial stiffness as carotid-radial pulse wave velocity (PWV), and identified deaths from the national register. Results: We studied 119 COPD subjects; aged 67.8 ±7.3, 66% were males and mean FEV1% predicted was 46.0 ±17.5. Subjects were classified into three pre-specificed groups: CAC = 0 (n = 14), 0 < CAC ≤ 400 (n = 41) and CAC > 400 (n = 64). Subjects with higher CAC were more likely to be older (p < 0.001) and male (p = 0.03), and more likely to have higher systolic blood pressure (p = 0.001) and a history of hypertension (p = 0.002) or ischemic heart disease (p = 0.003). Higher CAC was associated with higher PWV (OR 1.62, p = 0.04) and lower bone attenuation (OR 0.32, p = 0.02), but not with 15th percentile, after adjustment for age, sex and pack-years of smoking. In a Cox proportional hazards model, CAC, TAC and 15th percentile predicted all-cause mortality (HR 2.01, 2.09 and 0.66, respectively). Conclusions: Increased CAC was associated with increased arterial stiffness and lower bone density in a COPD cohort. In addition, CAC, TAC and extent of emphysema predicted all-cause mortality

Measuring and interpreting the ecosystem service of forest biodiversity

Biodiversity provides a supporting service to millions of people in the world and for those living in the Bale Mountains of Ethiopia. Collecting data, analyzing data and interpreting results on forest biodiversity is challenging and this presentation provides a description of the terms, methods and analysis associated with this task.National Science Foundation

Fire and Landscape Diversity in Subalpine Forests of Yellowstone National Park

Fire history was determined by fire scar analysis in a subalpine watershed in Yellowstone National Park, Wyoming, USA. Evidence was found for 15 fires since 1600, of which 7 were manor fires that burned \u3e 4 ha, destroyed the existing forest, and initiated secondary succession. Most of the upland forest area was burned by large, destructive fires in the middle and late 1700\u27s. Fires since then have been small and have occurred at long intervals. Fire frequency in this area is partly controlled by changes in the fuel complex during succession. Fuels capable of supporting a crown fire usually do not develop until a stand is 300-400 yr old, and ignitions prior to that time usually extinguish naturally before covering more than a few hectares. Thereafter a destructive crown fires is likely whenever lightning ignites small fuels during warm, dry, windy weather. On the extensive subalpine plateaus of Yellowstone National Park there appears to be a natural fire cycle of 300-400 yr in which large areas burn during a short period., followed by a long, relatively fire-free period during which a highly flammable fuel complex again develops. The study area appears to be about midway between major fire events in this cycle. This, rather than human fire suppression, apparently is the major reason for the small number and size of fires in the area during the last 180 yr. On the basis of the fire history data, the sequence of vegetation mosaics during the last 200 yr was reconstructed for the watershed. Indices of landscape diversity were computed for each reconstruction, treating forest types and successional stages as taxa and incorporating components of richness, evenness, and patchiness. Landscape diversity was highest in the early 1800\u27s following the large fires in the 1700\u27s, then declined in the late 1800\u27s during a 70—yr period when no major fires occurred and the landscape was dominated by even—aged forests developing on the areas burned in the 1700\u27s. Landscape diversity has increased somewhat during the last half—century as a result of two small fires and the effects of the mountain pine beetle. These landscape reconstructions for the last 200 yr suggest that the Yellowstone subalpine ecosystem is a nonsteady—state system characterized by long—term, cyclic changes in landscape composition and diversity. Such cyclic patterns may significantly influence wildlife habitat, streamflow, nutrient cycling, and other ecological processes and characteristics within the Park, and they may be an important consideration in judging whether recent ecological changes are natural or man induced. The landscape reconstructions were also made using a simulation model based on hypothetical fire management policies of total fire exclusion and selective fire control (permitting only small fires to burn). These hypothetical management policies generally reduced the richness and patchiness of the landscape compared to the natural fire regime, but they increased the evenness and reduced the magnitude of periodic fluctuations in overall landscape diversity. At times, overall landscape diversity may actually be higher with a fire control policy than with a natural fire regime. At other times, fire significantly increases landscape diversity, as would be expected