Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How trees manage water in arid environments

08.01.2007
Water scarcity is slowly becoming a fact of life in increasingly large areas.

The summer of 2006 was the second warmest in the continental United States since records began in 1895, according to the National Climatic Data Center. Moderate to extreme drought conditions were evident in about 40 percent of the country.

When Constance Brown moved from Arizona to Indiana two years ago, she was struck by a major difference: people in Indiana don't think about water every day the way people in Arizona do.

The difference shows up in many ways. In Arizona, Brown said, if you drop a piece of ice on the kitchen floor and ignore it, in a few minutes it will be gone -- melted and then evaporated. In Indiana, if you drop a piece of ice on the floor and ignore it, the water will just stay there until it's wiped up.

In Arizona, she said, if you need a particular garment on short notice and it's in the laundry, you can wash it by hand and hang it outside. It will be dry in 15 minutes. Not in Indiana.

In semi-arid environments such as the southwestern United States, humidity is so low that water is scarce to begin with and hard to hold onto when there is a rare cloudburst. Rain that collects in puddles is quickly sucked up by evaporation into the dry air. Most of the rest runs off before it can soak into the ground. Maintaining an adequate supply of water is a constant challenge, and water management is a top priority.

One way to make better use of scarce water resources would be to retain more of the water that falls during a heavy rain. To accomplish this, better understanding is needed about how water behaves in the environment. Brown, a micrometeorologist in the Atmospheric Science Program of Indiana University's Department of Geography, is one of the scientists working to provide this understanding. Her research is primarily funded by the National Science Foundation.

In a forthcoming paper in the Journal of Arid Environments, which is available on the Web at http://authors.elsevier.com/offprints/YJARE1769/

0dee34d6306f9059b870583e03a193bd, she reports the first results of a study designed to characterize the surface exchanges of water and carbon dioxide in a forest in the Santa Catalina Mountains near Tucson, Ariz. Mountain forests are an important source of water for the rest of such semi-arid regions, and these forests provide relatively isolated conditions where scientists can get a clearer picture of what is happening to the water that so many people depend on. In a desert region, such forests are found only at the tops of mountains because only there does precipitation exceed evaporation enough for forest vegetation to survive.

Understanding surface-atmosphere interactions is important to understanding a range of water resource phenomena including predictions about water supplies, Brown said. "This research seeks to characterize the explicit relationship between water availability and photosynthetic activities of the vegetation. This paper is the first step in that process, and it illustrates the seasonal characteristics of the forest vegetation-water relationship as observed during a three-year period during which there were extreme drought conditions in the semi-arid southwestern United States."

Brown's measurements showed that in this environment, there is a predominant, direct and immediate correspondence between water availability and photosynthetic activity of the vegetation. This is different from what happens in most coniferous forests, where the seasonal behavior of the trees is significantly influenced by temperature changes: the trees are largely dormant in winter and have a summer growing season. The mountain-top forest that she studied was in some ways the opposite.

"During the summer season before the heavy rains, when almost all the winter precipitation had been evaporated and the soil was extremely dry, the trees essentially closed down," she said. "This behavior suggests that the trees have little ability to access any moisture present in bedrock fractures. Because a late spring/early summer period without any rain is very common in southern Arizona, the mountain forest must have evolved the capability to survive it. The rapid recovery of this forest when heavy rains begin confirms the tight coupling between the trees and the available soil moisture."

In short, winter has a significant impact on the primary growing season for these mountain trees, because moisture is continually available from rain or snow, the tree root zones don't freeze, and there is enough sunlight for photosynthesis. The trees slow down during the pre-monsoon dry season in May and June when water is scarce, and then quickly respond to the sudden availability of water at the onset of the monsoon in July.

As unlikely as it may seem, Arizona does experience a monsoon every summer. Certain roads have yellow warning signs posted -- "Do Not Cross When Flooded." Though these signs may seem out of place in the middle of a desert, they have a serious purpose. In Arizona, as in other regions of the world such as India, residents must cope with a season of high temperatures, high winds and high moisture, resulting in potentially deadly weather.

The Arizona monsoon usually begins around July 7 and continues for the next two months, resulting in about one-third of the region's yearly rainfall. The monsoon varies from year to year in starting date, duration and intensity.

"The semi-arid forest ecosystem adapts to the extremes in the annual cycle of water availability by its ability to remain turned on during the winter," Brown said. "Water stress, rather than temperature, is the primary control on the forest's behavior. The trees will remain significantly active regardless of the season, providing they have access to moisture."

It remains to be seen whether coniferous forests at lower elevations in the western United States will be able to do the same if they are confronted with prolonged water scarcity.

Hal Kibbey | EurekAlert!
Further information:
http://www.indiana.edu

More articles from Ecology, The Environment and Conservation:

nachricht Preservation of floodplains is flood protection
27.09.2017 | Technische Universität München

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>