PLANTS VS ZOMBIE PLANTS

FROM: U.S. NATIONAL SCIENCE FOUNDATION

Global Plant Diversity Hinges on Local Battles Against Invasive Species
January 17, 2013
In Missouri forests, dense thickets of invasive honeysuckle decrease the light available to other plants, hog the attention of pollinators and offer nutrient-stingy berries to migrating birds.

They also release toxins that decrease the germination of nearby native plants.

Why, then, do studies of invasive species come to different conclusions about their effects and lead some organizations to suggest we accept their presence?

Biologists Kristin Powell, Tiffany Knight and Jon Chase of Washington University in St. Louis have found an answer.

Most studies of the effects of invasive plants are done at a single scale, report the scientists in this week's issue of the journal Science. Some studies scrutinize biodiversity in meter-square quadrats, while others scan biodiversity in entire islands or regions.

Meanwhile, invasives decrease biodiversity at small--but not at large--scales, the researchers discovered, leading them to conclude that how invasive species research is conducted can produce conflicting results.

"Perhaps not surprisingly, the big picture perspective is fundamentally different than the small-scale perspective," says Doug Levey, program director in the National Science Foundation's (NSF) Division of Environmental Biology, which funded the research.

Probing for scale dependence

The biologists had long suspected that studies of invasive species came to different conclusions because of scale dependence.

To test this notion, they analyzed 57 previous studies and confirmed a pattern: Invasive plants cause a large loss in species richness at small scales, but this effect diminishes at larger scales.

To test for scale dependence in the field, they chose three study sites in different ecosystems across the United States, each straddling an invasion front: a hammock forest in central Florida; an oak-hickory forest in eastern Missouri; and a tropical forest on the Big Island of Hawaii.

The hammock forest, a mix of live oak, cabbage palm, sweet gum and pignut hickory, is being invaded by the flax lily (Dianella ensifolia). Native to Africa and Asia, the lily forms dense mats on the forest floor.

Amur honeysuckle (Lonicera maackii), a mid-story shrub introduced from East Asia as an ornamental to provide bird habitat, is the issue in the oak-hickory forests.

The fire tree (Morella faya), a canopy tree that boosts nitrogen levels in the soil, making it inhospitable to native species and more suitable for invasives, is the troublemaker in the Hawaiian forest.

Invasives don't just sweep the board

"We counted the number of species per unit area in plots that varied in size from one meter square to 500 meters square--a quarter the size of a football field--on either side of the invasion front and then plotted the number of species against the size of the plot," Powell says.

"At small scales, invaded plots had many fewer species than uninvaded plots, but they picked up species more rapidly. At broad scales the invasives' effect on diversity virtually disappeared."

The reason for this "scale effect" is probability, says Powell.

"Invasives reduce the number of individual plants in a plot, and if there are fewer plants, there are fewer species," she says.

The invaded sites can catch up with uninvaded ones, Knight says, because the number of species does not increase indefinitely.

"At any site, if you sample larger and larger areas, the number of species will eventually plateau," Knight says.

At an invaded site, she says, "you reach that plateau later, but you do reach it eventually."

What it means for gardeners

The research helps to explain seemingly contradictory findings in the scientific literature, but what does it mean for people who've been hacking down honeysuckle in their backyards, and brushing their boots before entering conservation areas to avoid bringing in invasives?

Is it worth it or not?

"Emphatically yes," Knight says.

"Invasive species are a serious threat. If we're going to deal with them, we need the cooperation of the public."

Invasive plants have negative effects on plant communities at smaller scales--the scales that are crucial for ecosystem services like water management and nutrient cycling.

Take the bush honeysuckle choking Missouri's natural areas, for example.

It was seeded by birds carrying honeysuckle berries from backyards. To prevent it from turning nature preserves into shrub monocultures, people must remove it from their yards or choose not to plant it in the first place.

While the small scale justifies the fight, the large scale offers hope.

"Invasive plant species are reducing the abundance of native plant species, but most species are still present when we search for them at broad scales," says Knight.

"They haven't gone extinct yet."

Which means that it's not too late to restore habitat and increase abundances of native species, says Knight, "so they can contribute to critical ecosystem services and are less vulnerable to extinction."

PATIENT SUCESSFULLY EVACUATED FROM ANTARTICA

FROM: U.S. NATIONAL SCIENCE FOUNDATION
An Australian Airbus A319 jet is shown at the annual Sea Ice Runway, near McMurdo Station in this file photo from 2007. During the August 2012 medical evacuation, an Australian Airbus landed at Pegasus Field near McMurdo, one of a few airstrips in Antarctica able to accommodate wheeled aircraft.  Credit: Photograph by: Ralph Maestas National Science Foundation
Patient Successfully Evacuated From Antarctica
August 9, 2012
A medical evacuation flight bringing a patient from the National Science Foundation's McMurdo Station in Antarctica arrived safely in Christchurch, New Zealand at approximately 3 a.m. Eastern Time on Thursday, Aug. 9.

Upon arrival, the patient was transported to a local hospital for treatment.

Due to medical confidentiality, NSF has no additional comment on the patient's status.

NSF decided earlier this week to fly the patient out of Antarctica to receive treatment that is not available at McMurdo. The medical facility at the station is equivalent to an urgent-care center in the United States and is not equipped for the type of procedure that was being contemplated.

Kelly Falkner, the acting director of NSF's Office of Polar Programs, expressed the gratitude of the U.S. Antarctic Program, which NSF manages, to government agencies in Australia and New Zealand that provided the vital assets to make the evacuation possible.

She noted that "this is an excellent example of the benefits of longstanding cooperation with our Antarctic partners, Australia and New Zealand in particular."

The Australian Antarctic Division, which manages Australia's Antarctic research program, provided an A319 Airbus to transport the patient as well as the aircrew and medical support staff aboard the plane. The Royal New Zealand Air Force contributed search-and-rescue coverage, which is integral to any medical evacuation flight at this time of year.

Winter is coming to a close in Antarctica, but daylight is minimal and restricted to midday twilight, and temperatures are extremely low.

An additional passenger was also permitted to leave McMurdo Station aboard the medical evacuation flight because of compelling personal circumstances.

NSF manages the U.S. Antarctic Program, through which it coordinates all U.S. research and the necessary logistical support on the continent and aboard ships in the Southern Ocean.

　

NSF ARTICLE ON RELATIONSHIP BETWEEN SNOWBELT AND WATER SUPPLIES

Credit: NSF Southern Sierra Critical Zone Observatory/Jenny Park
FROM: U.S. NATIONAL SCIENCE FOUNDATION
Research at NSF's Southern Sierra CZO links snowmelt with downstream water supplies
Discovery
A Tree Stands in the Sierra Nevada
A coniferous view of the link between snowmelt and water supplies in the U.S. West
White fir, ponderosa pine, Jeffrey pine. Sugar pine, incense cedar, red fir: These are conifers of the headwater ecosystems of California's Sierra Nevada.

If trees could talk, what tales they might tell of the health of the forests, of the winter snows that fall on their branches and of how much water they transpire to the atmosphere.

Now one tree may be poised to do just that, or at least to offer new insights into a place called the critical zone: the region where rock meets life between the top of the forest canopy and the base of weathered rock.

The Critical Zone Tree, this white fir is called. It's a scientific totem pole that stands tall in the forest of the Southern Sierra Critical Zone Observatory (CZO).

The Southern Sierra CZO is one of six such observatories supported by the National Science Foundation (NSF). Scientists there recently found that winter snow from Sierra blizzards foretells how much water will be at the base of the mountains during the summer.

This is important for people downstream who toil in California's multi-billion-dollar agricultural industry and depend on water from Sierra snowmelt. That water is the source of more than 60 percent of California's supply.

In addition, without torrents of melting snow cascading across hillsides, wildflowers won't bloom, and the birds and bees that need the flowers' nectar can't thrive.

But more and more, the rivers are running dry, running late or running early.

"NSF's CZOs are providing scientists with new knowledge of the critical zone and its response to climate and land use change," says Enriqueta Barrera, program director in NSF's Division of Earth Sciences, which funds the network of six CZOs.

"They're the first systems-based observatories dedicated to understanding how Earth's surface processes are coupled," says Barrera. "The results will help us predict how the critical zone will affect the ecosystem services on which society depends."

The water cycle; the breakdown of rocks and eventual formation of soil; the evolution of rivers and valleys; patterns of plant growth; and landforms we see all result from processes that take place in the critical zone.

"The CZOs are fostering an investigation of the critical zone as a holistic system," says Barrera.

NSF's CZOs are located in watersheds in the southern Sierra Nevada; Boulder Creek in the Colorado Rockies; Susquehanna Shale Hills in Pennsylvania; Christina River Basin on the border of Delaware and Pennsylvania; Luquillo riparian zone in Puerto Rico; and the Jemez River and Santa Catalina Mountains in New Mexico and Arizona.

At the Southern Sierra CZO, "we investigate how the water cycle drives critical zone processes," says lead scientist Roger Bales of the University of California, Merced. "Research focuses on water balance, nutrient cycling and weathering across the rain-snow transition line."

Society has long recognized the importance of water, soil, landforms and rivers to human welfare, says Bales, "but has only recently begun to look at their workings as a coupled system."

Water, vegetation and geochemistry are all interrelated, Bales and other scientists have found, with feedbacks from each influencing the others. But, how are they interrelated?

Enter the Critical Zone Tree--or trees. "In actuality," says Bales, "there are several of them."

The white fir and its coniferous relatives observe Sierra forests from the headwaters of the Providence Creek Basin. The trees and forest floor around them are covered with instruments that measure soil moisture, temperature, snow depth, solar radiation, sap flow and snowmelt patterns.

Beneath them are crisscrossing streams that course through a series of meadows. These rivers and creeks fan out across the mountains, carrying water across hill and dale--water that eventually sustains California's food-producing Central Valley.

The Critical Zone Trees play a starring role in the southern Sierra CZO story. They've become frontrunners for a series of wireless sensors that dot the forest like wildflowers in spring, transforming our understanding of the mountain water cycle.

The network of sensors tracks snowpack depth, water storage in soil, stream flow and water use by vegetation--information that's important for the wise use of water in the arid Mountain West.

"This type of wireless sensor network will revolutionize the way we understand our most important source of water in California--and far beyond," says Bales.

Natural resource managers often lack accurate estimates of precipitation, and the loss of water from the soil from direct evaporation and by transpiration from the surfaces of plants in the mountains. Therefore, they struggle to know how much water to retain in reservoirs, how much to release--and when.

In a future that holds even more uncertainty, the Southern Sierra CZO wireless sensor network will provide water officials with a way to better predict snowmelt runoff.

"This observation system is our window into the future of water availability in the southern Sierras," says Jun Abrajano, NSF acting deputy assistant director for Geosciences.

Climate warming means that more rain and less snow will fall in the Sierras and plant growth will change accordingly. How long will we be able to rely on the Sierra snowpack as a "water tower"?

"An understanding of 'water balance,' made possible by the CZO, is what's needed to predict how whole-scale changes in vegetation cover will affect the future amount and timing of water availability in this region," says Abrajano.

Scientists at the Southern Sierra CZO are finding answers by teasing apart the interconnected strands of critical zone processes. They're asking questions such as: how do variations in landscapes affect the way soil moisture, water use by vegetation, and stream flow respond to snowmelt and rainfall?

Bales and colleagues have found that small temperature differences between rain- and snow-dominated Sierra watersheds result in significantly different timing of runoff in the region's coniferous forests.

For every one degree Celsius increase in long-term average temperature, the scientists believe, runoff will happen seven to 10 days earlier in some locations.

"We've also found that across a broad range of elevations, forests transpire water year-round," says Bales, "with much higher water use than previously predicted."

The results highlight a new link between climate and the deeper subsurface beneath trees.

Getting to the root of water availability, it turns out, may fall in the domain of not one Critical Zone Tree, but across--and under--a whole forest of them.

Follow snowfall and snowmelt in the Sierras beneath The Critical Zone
http://www.nsf.gov/discoveries/disc_images.jsp?cntn_id=125091&org=NSF