PARENT SESSION
Oral Session # 93: Vegetation Change and Response.
Presiding: B Parry Hecht
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 105.
Recent growth increases of northern range margin trees: Disturbance, climatic, and site interactions.
Pederson, Neil*,1, Jacoby, Gordon1, Cook, Ed1, 1 Tree-Ring Laboratory, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY
ABSTRACT- Climate change has increased high-latitude treeline growth in Northern Hemisphere forests over the last century. An important question to ask is "have eastern US mid-latitude trees experienced similar changes?" These trees provide fiber products, aesthetics for ecotourism and comprise one of the largest aboveground global carbon pools. Growth of northern range-margin trees, a species treeline, is a good place to address this question. Here we focus on several populations of Carya glabra, Chamaecyparis thyoides, Pinus rigida, Quercus prinus, and Q. rubra. At least 20 trees of each population were cored along a northerly transect in the Hudson River Valley of NY and NJ. Sampling was limited mostly to forests with little recent disturbance. Growth rings were crossdated, measured and combined to create two annual chronology types, average raw and relative ring widths. Four species had consistent recent growth increases across populations, C. thyoides, P. rigida, Q. prinus, and Q. rubra. Populations with recent increased growth tended to be positively correlated to temperature. Site characteristics along with proximity to a northern range-margin seemed important for temperature sensitivity, although this has yet to be quantified. All C. thyoides populations had increased growth rates over the last 40 years. Two Q. prinus populations had increasing raw ring widths after being in the canopy for more than 100 years, contrary to typical ring width trends. Nearly one third of the rings more one standard deviation above the post-canopy accession mean have occurred since 1982. Both populations had an average DBH greater than 0.5 m and many individuals 280 to >425 years old. Wider rings around such large trees indicate a substantial increase in biomass and carbon uptake. Age was not a limiting factor in growth. Our initial research indicates that climate, perhaps interacting with site factors, and competition has spurred biomass production.
Key words: biomass, tree growth, climate change, carbon uptake