| Bristlecone pine tree in the mountains of Arizona.
G. Koch |
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| Investigators |
| Dr. George W. Koch, Associate Professor, Department of Biological Sciences, Northern Arizona University
Mr. Todd Erickson, Research Assistant, Department of Biological Sciences, Northern Arizona University
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What is the Issue? |
| PHYSIOLOGICAL ADAPTATION(S) TO THE ENVIRONMENT BY TIMBERLINE TREE SPECIES |
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Bristlecone pine (Pinus aristata) is a long-lived species that grows in high elevation areas which display harsh environmental conditions. Engelmann spruce (Picea engelmannii) co-exists with bristlecone pine in these mountainous areas. Because of its longevity, bristlecone pine has been used extensively in the dendrochronological reconstruction of past climates. However, a full examination of the different environmental factors which influence the yearly growth cycles of bristlecone pine has not yet been fully undertaken. Investigation of factors such as variation in moisture availability and soil temperature, and how individual trees react to variations such as these, is crucial in understanding the ecophysiology of species which grow in arid, high altitude environments. Results from this study will aid the understanding of water use and photosynthesis by timberline tree species and provide baseline data for understanding potential future changes in the productivity and distribution of bristlecone pine and Engelmann spruce. A deeper understanding of how these species survive will also benefit their application and use as a paleoecological tool.
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What is our goal? |
| UNDERSTANDING THE ECOLOGY OF TREES GROWING UNDER HARSH ENVIRONMENTAL CONDITIONS.
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Where we currently stand. |
| This study commenced in summer 2000 and will run for two years. The primary study area is situated in the San Francisco Peaks, near Flagstaff, Arizona. Study sites have been selected, and sap flow techniques have been developed. Regular measurements of site environmental conditions are being taken, along with physiological measurements of 6-10 selected trees of each species. Initial sampling of Bristlecone pine indicates that needle growth may be a sensitive indicator of past weather conditions. Needle production was not reduced as dramatically in Bristlecone pine during the extreme drought of 1995/96 as it was in pinon pine, the dominant pine at lower elevations in northern Arizona. This suggests that temperature, rather than moisture, may be the overriding abiotic limitation on growth at high elevations in this region. Stable carbon isotope measurements of needles produced in years of different precipitation will reveal the extent to which stomatal conductance limitation of photosynthesis may respond to soil moisture. Outcomes from this study will be published in a peer-reviewed journal and presented at a national scientific meeting.
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