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Potts 1954.pdf
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PEK-RIC
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Practitioner Information
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Prescribed Burning
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Practitioner Information
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If you are a prescribed fire practitioner, there is a lot of information you need to know. Luckily, if you work for an agency, much of that information will be provided to you. However, if you are new to fire, or do not work for an agency, you can find much of this information online, or gain experience by working with mentors, other practitioners, or Prescribed Burn Association (PBA) members.
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Prescribed Burning
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Predator-induced reduction of freshwater carbon dioxide emissions
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Predators can influence the exchange of carbon dioxide between ecosystems and the atmosphere by altering ecosys- tem processes such as decomposition and primary production, according to food web theory1,2. Empirical knowledge of such an effect in freshwater systems is limited, but it has been suggested that predators in odd-numbered food chains sup- press freshwater carbon dioxide emissions, and predators in even-numbered food chains enhance emissions2,3. Here, we report experiments in three-tier food chains in experimental ponds, streams and bromeliads in Canada and Costa Rica in the presence or absence of fish (Gasterosteus aculeatus) and invertebrate (Hesperoperla pacifica and Mecistogaster mod- esta) predators. We monitored carbon dioxide fluxes along with prey and primary producer biomass. We found substan- tially reduced carbon dioxide emissions in the presence of predators in all systems, despite differences in predator type, hydrology, climatic region, ecological zone and level of in situ primary production. We also observed lower amounts of prey biomass and higher amounts of algal and detrital biomass in the presence of predators. We conclude that predators have the potential to markedly influence carbon dioxide dynamics in freshwater systems.
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Climate Science Documents
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Predicting a change in the order of spring phenology in temperate forests
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The rise in spring temperatures over the past half-century has led to advances in the phenology of many nontropical plants and animals. As species and populations differ in their phenological responses to temperature, an increase in temperatures has the potential to alter timing-dependent species interactions. One species-interaction that may be affected is the competition for light in deciduous forests, where early vernal species have a narrow window of opportunity for growth before late spring species cast shade. Here we consider the Marsham phenology time series of first leafing dates of thirteen tree species and flowering dates of one ground flora species, which spans two centuries. The exceptional length of this time series permits a rare comparison of the statistical support for parameter-rich regression and mechanistic thermal sensitivity phenology models. While mechanistic models perform best in the majority of cases, both they and the regression models provide remarkably consistent insights into the relative sensitivity of each species to forcing and chilling effects. All species are sensitive to spring forcing, but we also find that vernal and
northern European species are responsive to cold temperatures in the previous autumn. Whether this sensitivity reflects a chilling requirement or a delaying of dormancy remains to be tested. We then apply the models to projected future temperature data under a fossil fuel intensive emissions scenario and predict that while some species will advance substantially others will advance by less and may even be delayed due to a rise in autumn and winter temperatures. Considering the projected responses of all fourteen species, we anticipate a change in the order of spring events, which may lead to changes in competitive advantage for light with potential implications for the composition of temperate forests.
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Climate Science Documents
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Predicting ecosystem shifts requires new approaches that integrate the effects of climate change across entire systems
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Most studies that forecast the ecological conse- quences of climate change target a single species and a single life stage. Depending on climatic impacts on other life stages and on interacting species, however, the results from simple exper- iments may not translate into accurate predictions of future ecological change. Research needs to move beyond simple experimental studies and environmental envelope projections for single species towards identifying where ecosystem change is likely to occur and the drivers for this change. For this to happen, we advocate research directions that (i) identify the critical species within the target ecosystem, and the life stage(s) most susceptible to changing conditions and (ii) the key interactions between these species and components of their broader ecosystem. A combined approach using macroecology, experimentally derived data and modelling that incorporates energy budgets in life cycle models may identify critical abiotic conditions that disproportionately alter important ecological processes under forecasted climates.
Keywords: climate change; ocean acidification; global warming; species interactions; ecosystem shift; productivity and consumption
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Climate Science Documents
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Predicting satellite-derived patterns of large-scale disturbances in forests of the Pacific Northwest Region in response to recent climatic variation
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Across the Pacific Northwest, the climate between 1950 and 1975 was exceptionally cool and wet compared
with more recent conditions (1995–2005). We reasoned that the changes in climate could result in expanded
outbreaks of insects, diseases, and fire. To test this premise, we first modeled monthly variation in photosynthesis
and growth of the most widely distributed species, Douglas-fir (Pseudotsuga menziesii), using a
process-based model (3-PG) for the two periods. To compare with remotely sensed variables, we converted
modeled growth potential into maximum leaf area index (LAImax), which was predicted to range from 1 to 9
across the region. On most sites, varying soil moisture storage capacity (θcap) from 200 to 300 mm while
holding soil fertility constant, made slight but insignificant difference in simulated LAImax patterns. Both
values of θcap correlated well with LAI estimates acquired from NASA's MODIS satellites in June, 2005
(r2= 0.7). To evaluate where 15 coniferous tree species might be prone to wide-scale disturbance, we used
climatically-driven decision-tree models, calibrated in the 1950–1975 period, to identify vulnerable areas
in 1995–2005. We stratified predictions within 34 recognized ecoregions and compared these results with
large-scale disturbances recorded on MODIS imagery acquired between 2005 and 2009. The correlation
between the percent of species judged as vulnerable within each ecoregion and the percent of forested
areas recorded as disturbed with a MODIS-derived Global Disturbance Index was linear and accounted for
65 to 73% of the observed variation, depending on whether or not disturbance by fire was excluded from
the analysis. Based on climate projections through the rest of the rest of the 21st century, we expect continued
high levels of disturbance in ecoregions located beyond the climatically buffering influence of the Pacific
Ocean.
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Resources
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Climate Science Documents
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Predictive traits to the rescue
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Climate change poses new challenges to the conservation of species, which at present requires data-hungry models to meaningfully anticipate future threats. Now a study suggests that species traits may offer a simpler way to help predict future extinction risks.
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Climate Science Documents
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Prescott Bridge 1991.pdf
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HEA-HOL
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Prescribed Burn
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