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Climate Videos and Webinars
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Climate, carbon cycling, and deep-ocean ecosystem
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Climate variation affects surface ocean processes and the production of organic carbon, which ultimately comprises the primary food supply to the deep-sea ecosystems that occupy 60% of the Earth’s surface. Warming trends in atmospheric and upper ocean temperatures, attributed to anthropogenic influence, have occurred over the past four decades. Changes in upper ocean temperature influence stratification and can affect the availability of nutrients for phytoplankton production. Global warming has been predicted to intensify stratification and reduce vertical mixing. Research also suggests that such reduced mixing will enhance variability in primary production and carbon export flux to the deep sea. The dependence of deep-sea communities on surface water production has raised important questions about how climate change will affect carbon cycling and deep-ocean ecosystem function. Recently, un- precedented time-series studies conducted over the past two decades in the North Pacific and the North Atlantic at >4,000-m depth have revealed unexpectedly large changes in deep-ocean ecosystems significantly correlated to climate-driven changes in the surface ocean that can impact the global carbon cycle. Climate-driven variation affects oceanic communities from surface waters to the much-overlooked deep sea and will have impacts on the global carbon cycle. Data from these two widely separated areas of the deep ocean provide compelling evidence that changes in climate can readily influence deep-sea processes. However, the limited geographic coverage of these existing time-series studies stresses the importance of developing a more global effort to monitor deep- sea ecosystems under modern conditions of rapidly changing climate.
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Climate-induced changes in the small mammal communities of the Northern Great Lakes Region
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We use museum and other collection records to document large and extraordinarily rapid
changes in the ranges and relative abundance of nine species of mammals in the northern
Great Lakes region (white-footed mice, woodland deer mice, southern red-backed voles,
woodland jumping mice, eastern chipmunks, least chipmunks, southern flying squirrels,
northern flying squirrels, common opossums). These species reach either the southern or
the northern limit of their distributions in this region. Changes consistently reflect
increases in species of primarily southern distribution (white-footed mice, eastern
chipmunks, southern flying squirrels, common opossums) and declines by northern
species (woodland deer mice, southern red-backed voles, woodland jumping mice, least
chipmunks, northern flying squirrels). White-footed mice and southern flying squirrels
have extended their ranges over 225 km since 1980, and at particularly well-studied sites
in Michigan’s Upper Peninsula, small mammal assemblages have shifted from numerical
domination by northern species to domination by southern species. Repeated resampling
at some sites suggests that southern species are replacing northern ones rather than
simply being added to the fauna. Observed changes are consistent with predictions from
climatic warming but not with predictions based on recovery from logging or changes in
human populations. Because of the abundance of these focal species (the eight rodent
species make up 96.5% of capture records of all forest-dwelling rodents in the region and
70% of capture records of all forest-dwelling small mammals) and the dominating
ecological roles they play, these changes substantially affect the composition and
structure of forest communities. They also provide an unusually clear example of change
that is likely to be the result of climatic warming in communities that are experienced by
large numbers of people.
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CLIMATE’S SMOKY SPECTRE
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With their focus on greenhouse gases, atmospheric scientists have largely overlooked lowly soot particles. But black carbon is now a hot topic among researchers and politicians.
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Climate: Sawyer predicted rate of warming in 1972
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Excerpt: "In four pages Sawyer summarized what was known about the role of carbon dioxide in enhancing the natural greenhouse effect, and made a remarkable prediction of the warming expected at the end of the twentieth century.He concluded that the 25% increase in atmospheric carbon dioxide predicted to occur by 2000 corresponded to an increase of 0.6 °C in world temperature..... In fact the global surface temperature rose about 0.5 °C between the early 1970s and2000. Considering that global temperatures had, if anything, been falling in the decades leading up to the early 1970s, Sawyer’s prediction of a reversal of this trend, and of the correct magnitude of the warming, is perhaps the most remarkable long-range forecast ever made.
Despite huge efforts, and advances in the science, the scientific consensus on the amount of global warming
expected from increasing atmospheric carbon dioxide concentrations has changed little from that in Sawyer’s time.
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Climatic change and wetland desiccation cause amphibian decline in Yellowstone National Park
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Amphibians are a bellwether for environmental degradation, even in natural ecosystems such as Yellowstone National Park in the western United States, where species have been actively protected longer than anywhere else on Earth. We document that recent climatic warming and resultant wetland desiccation are causing severe declines in 4 once-common amphibian species native to Yellowstone. Climate monitoring over 6 decades, remote sensing, and repeated surveys of 49 ponds indicate that decreasing annual precipitation and increasing temperatures during the warmest months of the year have significantly altered the landscape and the local biological communities. Drought is now more common and more severe than at any time in the past century. Compared with 16 years ago, the number of permanently dry ponds in northern Yellowstone has increased 4-fold. Of the ponds that remain, the proportion supporting amphibians has declined significantly, as has the number of species found in each location. Our results indicate that climatic warming already has disrupted one of the best-protected ecosystems on our planet and that current assessments of species’ vulnerability do not adequately consider such impacts.
global warming landscape change remote sensing amphibian community drought
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Climatic extremes improve predictions of spatial patterns of tree species
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Understanding niche evolution, dynamics, and the response of species to climate change requires knowledge of the determinants of the environmental niche and species range limits. Mean values of climatic variables are often used in such analyses. In contrast, the increasing frequency of climate extremes suggests the importance of understanding their additional influence on range limits. Here, we assess how measures representing climate extremes (i.e., interannual variability in climate parameters) explain and predict spatial patterns of 11 tree species in Switzerland. We find clear, although comparably small, improvement (20% in adjusted D2, 8% and 3% in cross-validated True Skill Statistic and area under the receiver operating characteristics curve values) in models that use measures of extremes in addition to means. The primary effect of including information on climate extremes is a correction of local overprediction and underprediction. Our results demonstrate that measures of climate extremes are important for understanding the climatic limits of tree species and assessing species niche characteristics. The inclusion of climate variability likely will improve models of species range limits under future conditions, where changes in mean climate and increased variability are expected.
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Climatic Impact of Tropical Lowland Deforestation on Nearby Montane Cloud Forests
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Tropical montane cloud forests (TMCFs) depend on predictable, frequent, and prolonged immersion in cloud. Clearing upwind lowland forest alters surface energy budgets in ways that influence dry season cloud fields and thus the TMCF environment. Landsat and Geostationary Operational Environmental Satellite imagery show that deforested areas of Costa Rica’s Caribbean lowlands remain relatively cloud-free when forested regions have well-developed dry season cumulus cloud fields. Further, regional atmospheric simulations show that cloud base heights are higher over pasture than over tropical forest areas under reasonable dry season conditions. These results suggest that land use in tropical lowlands has serious impacts on ecosystems in adjacent mountains.
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Climatic variability and episodic Pinus ponderosa establishment along the forest-grassland ecotones of Colorado
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The primary objective of this study was the detection of possible climatic influences on the recent (i.e., past c. 40 years) establishment of ponderosa pine (Pinus ponderosa) at or near forest-grassland ecotones in the northern Front Range of Colorado. Germination dates were precisely determined for >500 juvenile ponderosa pine collected in six widely dispersed sample areas. All sites sampled were open areas lacking an overstory tree cover but located near seed sources. To evaluate the effects of recent climatic variation on recruitment and survival patterns, three types of climate data were used: (1) instrumental climate records from nearby local weather stations; (2) a multivariate index of El Nino/Southern Oscillation (ENSO); and (3) a regional, ponderosa pine tree-ring index sensitive to moisture variation. There is a strong association between episodic recruitment of ponderosa pine and years in which spring and fall moisture availability is high in the instrumental climate record. During the past 40 years, tree establishment was highly episodic and concentrated mainly in four years—1973, 1979, 1983, and 1990. These years are also associated with large-scale warming of sea-surface temperatures in the eastern tropical Pacific (i.e., El Nin ̃o events). These years of abundant seedling establishment also coincide with years of above average radial growth in mature ponderosa pine. Thus, at open sites suitable for the survival of shade-intolerant ponderosa pine, successful establishment of seedlings is highly episodic depending on local moisture availability related to broad-scale climatic variation. This study demonstrates the climatic sensitivity of ponderosa pine recruitment at low elevation sites along forest-grassland ecotones in the northern Colorado Front Range.
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Clone history shapes Populus drought responses
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Just as animal monozygotic twins can experience different environmental conditions by being reared apart, individual genetically identical trees of the genus Populus can also be exposed to contrasting environmental conditions by being grown in different locations. As such, clonally propagated Populus trees provide an opportunity to interrogate the impact of individual environmental history on current response to environmental stimuli. To test the hypothesis that current responses to an environmental stimulus, drought, are contingent on environmental history, the transcriptome- level drought responses of three economically important hybrid genotypes—DN34 (Populus deltoides × Populus nigra), Walker [P. deltoides var. occidentalis × (Populus laurifolia × P. nigra)], and Okanese [Walker × (P. laurifolia × P. nigra)]—derived from two different locations were compared. Strikingly, differences in transcript abundance patterns in response to drought were based on differences in geographic origin of clones for two of the three genotypes. This observation was most pronounced for the genotypes with the longest time since establishment and last common propagation. Differences in genome-wide DNA methylation paralleled the transcriptome level trends, whereby the clones with the most divergent transcriptomes and clone history had the most marked differences in the extent of total DNA methylation, suggesting an epigenomic basis for the clone history-dependent transcriptome divergence. The data provide insights into the interplay between genotype and environment in the ecologically and economically important Populus genus, with implications for the industrial application of Populus trees and the evolution and persistence of these important tree species and their associated hybrids.
epigenetics | forest trees | poplar
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