Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study Ties Forest "Greenness" in Western U.S. to Snowpack Extent

11.09.2012
Mid-elevation mountain ecosystems most sensitive to rising temperatures and changes in snowmelt

Results of a new study tie forest "greenness" in the western United States to fluctuating year-to-year snowpack extent.


A Sierra Nevada forest in Sequoia National Park: snow depth and forest pattern are related.

The results show that mid-elevation mountain ecosystems are the most sensitive to rising temperatures and to changes in precipitation and snowmelt.

University of Colorado-Boulder scientist Noah Molotch and colleagues used satellite images and ground measurements to identify the threshold at which mid-level forests sustained by moisture change to higher-elevation forests sustained by sunlight.

A paper reporting the results was published yesterday in the journal Nature Geoscience.

Molotch is the lead author. Co-authors are Ernesto Trujillo of the University of Colorado-Boulder and Ecole Polytechnique Fédérale de Lausanne in Switzerland; Michael Golden and Anne Kelly of the University of California, Irvine; and Roger Bales of the University of California, Merced.

"The research demonstrates yet another complexity in the response of mountain ecosystems to increasing temperatures," says hydrologist Tom Torgersen, program director in the National Science Foundation's Division of Earth Sciences, which funded the research. "High-elevation mountain forests are typically temperature-stressed and low-elevation mountain forests are often water-stressed.

"At mid-elevations, 'everything is just right'--until it goes wrong." Torgersen says, "Higher temperatures lead to reduced snowpack and reduced water availability, leaving trees at mid-elevations more stressed and more prone to fires."

The ability to identify this "tipping point" is important, Molotch says, because mid-level forests--at altitudes from roughly 6,500 feet to 8,000 feet--are where many people live and visit. They're also linked with increasing wildfires, beetle outbreaks and rising tree mortality.

"These results provide the first direct observations of snowpack-forest connections across broad scales," says Molotch.

"Finding the tipping point between water-limited [mid-elevation] forests and energy-limited [high-elevation] forests defines the region of the greatest sensitivity to climate change--the mid-elevation forests--which is where we should focus future research," he says.

Although the research took place in the Sierra Nevada mountain range in California, it's applicable to other mountain ranges across the West.

Climate studies show that the snowpack in mid-elevation forests in the western United States and other forests around the world has been decreasing over the past 50 years because of regional warming.

"We found that mid-elevation forests show a dramatic sensitivity to snow that fell the previous winter in terms of accumulation and subsequent melt," said Molotch, also a scientist at NASA's Jet Propulsion Laboratory in Pasadena.

"If snowpack declines, forests become more stressed, which can lead to ecological changes in the distribution and abundance of plant and animal species, and to more vulnerability to fires and to beetle kill."

Molotch says that about 50 percent of the greenness seen by satellites in mid-elevation forests is linked with maximum snow accumulation from the previous winter, with the other 50 percent related to soil depth, soil nutrients, temperature and sunlight.

"The strength of the relationship between forest greenness and snowpack from the previous year is very surprising," Molotch says.

The researchers initially set out to identify the various components of drought that lead to vegetation stress.

"We went after mountain snowpacks in the western U.S. because they provide about 60 to 80 percent of the water in high-elevation mountains," says Molotch.

The team used 26 years of continuous data from the Advanced Very High Resolution Radiometer, a space-borne sensor flying on a National Oceanic and Atmospheric Administration satellite, to measure the forest greenness.

The researchers compared it with long-term data from 117 snow stations maintained by the California Cooperative Snow Survey, a consortium of state and federal agencies.

In addition, the scientists used information gathered from "flux towers" in the southern Sierra Nevada mountain range. Instruments on these towers measure the exchanges of carbon dioxide, water vapor and energy between the land and the atmosphere.

Instruments on the towers, which are some 100 feet high, allowed scientists to measure the sensitivity of both mid-level and high-level mountainous regions to both wet and dry years--data that matched up well with the satellite and ground data.

"The implications of this study are profound when you think about the potential for ecological change in mountain environments in the West," says Molotch.

"If we look ahead to the time when climate models are calling for warming and drying conditions, the implication is that forests will be increasingly water-stressed in the future and more vulnerable to fires and insect outbreaks."

In the context of recent forest losses to fire in Colorado and elsewhere, the findings are something that really deserve attention, Molotch says.

"This tipping-point elevation is very likely going to migrate up the mountainsides as climate warms."

The research was also funded by NASA.

-NSF-

Media Contacts
Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
Jim Scott, University of Colorado-Boulder (303) 492-3114 jim.scott@colorado.edu
Related Websites
NSF discovery article: A Tree Stands in the Sierra Nevada: http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=125091&org=NSF
NSF Southern Sierra Critical Zone Observatory: https://eng.ucmerced.edu/czo/index.html

NSF Critical Zone Observatories: Where Rock Meets Life: http://www.criticalzone.org/

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2012, its budget is $7.0 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives over 50,000 competitive requests for funding, and makes about 11,000 new funding awards. NSF also awards nearly $420 million in professional and service contracts yearly.

Cheryl Dybas | EurekAlert!
Further information:
http://www.nsf.gov
http://nsf.gov/news/news_summ.jsp?cntn_id=125359&org=NSF&from=news

More articles from Earth Sciences:

nachricht Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center

nachricht NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>