The latest edition of Ecology is now available. The journal includes studies on a wide variety of topics, including:
Demography of the Yellowstone Grizzly Bears
Yellowstone's grizzly bears (Ursus arctos) may seem awesomely powerful to
National Park visitors, but a new study suggests they are still very threatened
as a species. Written by Craig Pease (Vermont Law School) and David Mattson (US
Geological Survey, Biological Resources Division), the paper analyzed nearly two
decades of data on radio-collared bears in the Yellowstone ecosystem. The
researchers concluded that the number of bears has changed little in the past
two decades, despite intensive grizzly bear management. Bear mortality is
nearly double in years when the whitebark pine crop fails, and the whitebark
pine itself is in trouble, say the authors. The pine crop is now failing almost
every other year, and widespread suppression of fires has also been detrimental
to its health. Global warming may also pose a threat to the tree species.
People also cause bear mortality in both direct and indirect ways, the
researchers assert. Humans have directly caused 70-90% of all known grizzly bear deaths in the Yellowstone ecosystem since the 1970s. Whitebark
pines are found at higher elevations that tend to be less used by humans. When
the pine crop fails, the bears move to lower-elevation sites (which are closer
to humans) to feed. "When the whitebark pine crop fails, the grizzly bear is hit
with a double whammy," says Pease. "Simply being around more people increases
their immediate chance of death. And by foraging closer to humans, grizzlies
lose their natural wariness of people. Those bears will then have an increased
risk of death forever, even in years with abundant pine seeds."
The Fern Understory as an Ecological Filter
They are seedless, flowerless and relatively small in stature, but a new study
suggests that ferns can play an important role in determining the future
composition of forests. Lisa George and F.A. Bazzaz of Harvard University
examined how the growth rates of several kinds of trees were affected by the
presence of a fern understory. Working for three years in the Harvard Forest of
Massachusetts, the researchers compared the survival rates of red maples (Acer
rubrum), yellow birches (Betula alleghaniensis) and red oaks (Quercus rubra) in
fern covered areas to the survival rates of these same kinds of trees in
fern-free areas. They discovered that hayscented ferns (Dennstaedtia
punctilobula) and interrupted ferns (Osmunda claytonia) affected the growth and
survival rates of seedlings for all of the species, but the magnitude of the
effect differed among the various kinds of trees. All of the seedlings grew
more slowly in fern covered areas. But, say the researchers, the ultimate survival of the oak seedlings did not differ between fern and fern-free
areas. By contrast, the birch seedlings were highly affected, with only one
third of the birches under the ferns surviving after two years. Shade provided
by the fern fronds was the main determining factor in the growth patterns of the
trees in the study. "The fern understory is a powerful filter," says George.
"Fern presence in a forest can determine the size, the species, and the density
of the trees."
Earthworms Shed Light on Plant Responses to Climate Change
Earthworms first achieved celebrity status when their role in food compost and
soil health was discovered. Surprisingly enough, scientists now believe that the
next claim to fame for these little subterranean creatures is in their fecal
droppings. Johann Zaller and John Arnone at the Universitaet Basel in
Switzerland (now at Utah State University and the Desert Research Institute in
Reno, Nevada, respectively) conducted studies investigating plant responses to
climate change in grassland ecosystems. Their work has demonstrated a unique
relationship between plant growth and earthworm castings under different levels
of CO2. The rich earthworm castings, which are more abundant in nutrients than
surrounding soils, are valuable resources for plants. Zaller and Arnone
discovered that plant species that grew in closer association with worm
excrement displayed more growth under higher levels of CO2 than non-associated
species. According to Zaller and Arnone, "Worm castings have a significant impact on the community structure of grasslands and will continue to
influence their future structure as global CO2 levels continue to rise."
Ecology is a peer-reviewed journal published eight times a year by the Ecological Society of America (ESA). Copies of the above article are available free of charge to the press through the Society's Public Affairs Office. Members of the press may also obtain copies of ESA's entire family of publications, which includes Ecology, Ecological Applications, Ecological Monographs, and Conservation Ecology. Others interested in copies of articles should contact the Reprint Department at the address in the masthead.
Founded in 1915, the Ecological Society of America (ESA) is a scientific, non-profit, organization with over 7000 members. Through ESA reports, journals, membership research, and expert testimony to Congress, ESA seeks to promote the responsible application of ecological data and principles to the solution of environmental problems. For more information about the Society and its activities, access ESA's web site at: http://esa.sdsc.edu.
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Ecology