HR: 1340h
AN: B23A-0933    [Abstracts]
TI: Evidence of Vigorously Growing Old Trees in Eastern U.S. Forests
AU: * Pederson, N
EM: adk@ldeo.columbia.edu
AF: Tree-Ring Laboratory, LDEO, P.O. Box 1000, Palisades, NY 10964 United States
AU: Cook, E R
EM: drdendro@ldeo.columbia.edu
AF: Tree-Ring Laboratory, LDEO, P.O. Box 1000, Palisades, NY 10964 United States
AU: Hopton, H M
EM: hmh@columbia.edu
AF: Tree-Ring Laboratory, LDEO, P.O. Box 1000, Palisades, NY 10964 United States
AU: Jacoby, G C
EM: druid@ldeo.columbia.edu
AF: Tree-Ring Laboratory, LDEO, P.O. Box 1000, Palisades, NY 10964 United States
AB: Many ecological, forestry and carbon sequestration models operate under the assumption that growth declines as trees age. Tree-ring studies at latitudinal and altitudinal treeline locations suggest that this may not always be true, especially over the last 150 years. Increment cores from > 1200 southern temperate trees were used to test the age-related decline hypothesis in the eastern U.S. Trees in this database range in age from 70 to 463 years, are comprised of four species ({\it Querucs alba, Q. prinus, Liriodendron tulipifera, Chameacyparis thyoides}) and include the oldest individuals documented by dendrochronology for {\it Q. alba} (463 years), {\it Q. prinus} (426 years), and {\it L. tulipifera} (335 years). {\it Quercus} trees were combined and grouped into six periods (1851-1900, 1801-1850,.pre-1651) to avoid a potential bias in growth trend by younger trees. Because age structure of {\it L. tulipifera} and {\it C. thyoides} forests are generally much younger, unique age classes were created for each species. The oldest trees for all species had periods of statistically significant, above average ring-width during the 20th century. The current trend of increased growth started in the mid- to late-1800s for {\it Quercus} and {\it L. tulipifera} while it started in the 1920s for {\it C. thyoides}. Using allometric equations to convert all chronologies to carbon increment reveals strong, positive trends in growth over the last century. These results show that even the oldest trees are taking up more carbon today than in the past. Because {\it L. tulipifera} and {\it C. thyoides} are less shade tolerant and have considerably different life-history traits than {\it Quercus}, it seems less likely that stand dynamics is the most important factor of these trends. Though old-growth forests are rare in temperate zones, our data can serve as a model for the large number of forests 100-180+ years old. It may not necessarily be true that forests in the eastern US will slow down in growth at ages 200 year and beyond. If ecosystem productivity declines with increasing tree age, changes in stand structure, environmental growth conditions or tree size may be the primary causes. Regardless, our results support treeline location studies to show that tree-scale productivity does not necessarily decline with age.
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting