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- Info
Responses of tree crown conditions to natural and induced variations in throughfall
| Author: |
Leininger, T.D. |
| Date: |
2002 |
| Periodical: |
In: Gen. Tech. Rep. SRS–48. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station |
| Link: |
http://www.srs.fs.usda.gov/pubs/gtr/gtr_srs048/article/gtr_srs048-leininger01.pdf
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| Abstract: |
Concentrations of greenhouse gases, such as carbon dioxide, methane, and oxides of nitrogen, in the atmosphere are predicted to double in the next one hundred years. Forecasts of climatic variation across the southeastern United States resulting from these increases range from higher average temperatures and decreased summertime precipitation to lower maximum temperatures and greater precipitation. Since 1993, the effects of increased and decreased precipitation have been studied on an upland hardwood forest in the Walker Branch Watershed near Oak Ridge, TN. Soil moisture was altered by gravity-driven transport of throughfall from a 'dry' (-33 percent of ambient) treatment plot across an ambient treatment plot to a 'wet' ( 33 percent of ambient) treatment plot. Beginning in August 1996, crown conditions of saplings and mature trees were monitored annually for responses to seasonal and treatment-related differences in soil moisture. The crown condition classification system developed by the USDA Forest Service, Forest Health Monitoring Program (FHMP) was used to rate tree crowns according to five variables: crown diameter, live crown ratio, foliage density, foliage transparency, and crown dieback. Preliminary analyses indicate differences in crown condition variables between soil moisture treatments and between years within treatments. A full analysis of five years of data, including August 2000, is presented. Results are discussed in relation to climate change predictions for the southeastern United States, and the usefulness of the FHMP crown condition classification system for monitoring forest health in a changing environment. |
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