HR: 1340h
AN: B33D-1578    [Abstracts]
TI: How do forest ecosystems respond to a warm and dry weather event during the early growing season in eastern North America?
AU: * Arain, M
EM: arainm@mcmaster.ca
AF: McMaster University, School of Geography and Earth Sciences, 1280 Main Street West, Hamilton, ON L8S3M2, Canada
AU: Peichl, M
EM: peichlm@mcmaster.ca
AF: McMaster University, School of Geography and Earth Sciences, 1280 Main Street West, Hamilton, ON L8S3M2, Canada
AU: Brodeur, J
EM: brodeujj@mcmaster.ca
AF: McMaster University, School of Geography and Earth Sciences, 1280 Main Street West, Hamilton, ON L8S3M2, Canada
AU: McLaren, J
EM: mclarejd@mcmaster.ca
AF: McMaster University, School of Geography and Earth Sciences, 1280 Main Street West, Hamilton, ON L8S3M2, Canada
AU: Restrepo, N
EM: ncoupe@email.arizona.edu
AF: McMaster University, School of Geography and Earth Sciences, 1280 Main Street West, Hamilton, ON L8S3M2, Canada
AU: Khomik, M
EM: khomikm@mcmaster.ca
AF: McMaster University, School of Geography and Earth Sciences, 1280 Main Street West, Hamilton, ON L8S3M2, Canada
AB: Many studies are being conducted under global Fluxnet to understand how forest ecosystems may respond to short-term weather events such as warm and dry periods. We measured energy, water vapour and carbon dioxide (CO2) fluxes in an age-sequence (66, 33, 17 and 5 year old) of temperate conifer forests (eastern white pine, -Pinus strobus L.) on the northwest shore of Lake Erie in southern Ontario, Canada, from 2003 to 2006 using the Eddy Covariance (EC) technique. Net ecosystem productivity (NEP) and water use efficiency (WUE) of the 17-yr-old stand was highest, followed by the 33-yr-old, 66-yr-old, and 5-yr-old forests. In 2005, eastern parts of North America experienced a warm and dry spring and early summer drought that significantly reduced NEP of these forest ecosystems. Compared to previous years, the warm and dry summer of 2005 resulted in a decrease of about 100-200 g C m ^-2 y ^-1 at all four sites, mostly because of a decrease in gross ecosystem productivity due to water stress and an increase in ecosystem respiration due to warm soil temperatures. The sensitivity of drought stress increased with increasing stand age. An EC flux component study utilizing sapflow and soil water content measurements in the 66-year stand indicated the occurrence of hydraulic redistribution during drought periods. The nightly increase in soil water (up to 0.50 mm) provided by hydraulic redistribution may have reduced drought intensity in the root zone by maintaining soil water contents at levels above the minimum observed soil moisture threshold (~ 0.07 mm) in these sandy soils. Similar reductions in measured NEP in 2005 were also observed in other forest ecosystems in the region. The results of this study indicate how eastern North American forest ecosystems might be affected by environmental stresses and drivers if this region experiences more extreme climatic conditions in future, including frequent warm and dry periods.
UR: http://www.science.mcmaster.ca/geo/faculty/arain/
DE: 0428 Carbon cycling (4806)
DE: 0495 Water/energy interactions (1878)
DE: 1812 Drought
DE: 1818 Evapotranspiration
DE: 1840 Hydrometeorology
SC: Biogeosciences [B]
MN: 2007 Fall Meeting