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Trees and Drought
| Article
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15333 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
8 / 1989 |
1,633 Words |
| Author
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Merrill R. Kaufmann
Merrill R. Kaufmann is a principal plant physiologist with the
USDA Forest Service's Rocky Mountain Forest and Range
Experiment Station in Fort Collins, Colorado. He is the team
leader for ecosystem studies in a multifunctional research
unit studying subalpine and montane forest management. |
Stephen Hales was an English clergyman who spent much of his life conducting research on fluids in living organisms. His book, Vegetable Staticks, published in 1727, was the first to explain that plants do not have a circulation system like animals, but rather take in large quantities of water through their roots and "perspire" (transpire) the water through the leaves.
Much has been learned in the last several decades about how water moves through plants. It is astonishing, however, that so much of this "new" knowledge is a formalization of concepts Hales described so clearly over 250 years ago. And the research introduced by Hales has important relevance in today's scientific concerns.
Water is a critical component of plant tissues. It is important as a solvent for cell constituents, for transport of nutrients absorbed by the root system, and for translocation of carbohydrates produced by the leaves during photosynthesis. Water is responsible for turgor (the positive pressure that accounts for cell expansion during growth) in cells and also for the opening of stomata (the small pores on leaf surfaces through which gases are exchanged). When water supplies to plants are limited, serious problems develop within plants, including a reduction in photosynthesis and in growth of various plant tissues.
Issues of global climate changes are in the forefront of news today, and many are concerned about what to expect of our earth in the century ahead. While future conditions are still uncertain, researchers anticipate not only significant warming but also increased drought in many regions of the world. Forests cover huge areas of land, and their behavior in a changing climate is extremely important. Forests fix CO2 and provide fiber products, as well as affect the supply of water for farm, urban, and industrial uses. Forests also provide habitat for wildlife and contribute to aesthetic experiences. The health of our forests is a critical concern.
Because of their size and the length of their life cycle, trees respond to drought quite differently than annuals or other small plants having life cycles lasting only a few years. A month of drought is only a brief time for a tree that lives to be 100 years old, whereas it represents a major portion of the growth period for a roadside annual. Since trees tend to be more deeply rooted and often conserve water better than herbs and grasses, a timely rain for a wheat or corn farmer may be critical, but the lack of rain may have relatively limited effect on a forest unless it
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