HR: 1340h
AN: A13B-0114    [Abstracts]
TI: Physiological Regulation of Stomatal Conductance in Boreal Forest Species: Do Species Differ and Does it Matter?
AU: * Berry, J A
EM: joeberry@stanford.edu
AF: Carnegie Institution of Washington, Department of Global Ecology 260 Panama St, Stanford, CA 94305-4101 United States
AU: Wolf, A
EM: awolf@ucdavis.edu
AF: University of California, Department of Agronomy and Range Science, Davis, CA 95616 United States
AU: Vygodskaya, N N
EM: igorn@pochamt.ru
AF: IPEE, RAS, Leninskiy pr, Moscow, 117071 Russian Federation
AB: Measurements of energy and water balance over Boreal forest ecosystems have generally shown very large ratios of sensible heat flux to latent heat flux (Bowen ratio) - especially on fine summer days. This strong control on evaporation at the plant scale can restrict precipitation and effect hydrometeorlogy at the regional scale. The large Bowen ratio is, in part, explained by the low maximum stomatal conductance of Boreal forest tree species and is probably related to their very low photosynthetic capacity. However, mid-day conductance can be much lower than expected on this basis and reflects the additional effect of a dynamic feedback system between stomatal conductance and the properties of the atmospheric boundary layer. Low stomatal conductance leads to a large sensible heat flux which, in turn, leads to a deeper, warmer and dryer atmospheric boundary layer and to a greater evaporative demand on the plant, causing the stomata close still more. Predicting the response of this non-linear system presents a major challenge. Physiological studies conducted in the Canadian Boreal forest show very large differences in the tendency of species to experience mid day stomatal closure. Jack pine was found to be quite susceptible while black spruce the most resistant to mid day stomatal closure. These species had very similar photosynthetic capacity (Vmax) and Ball-Berry stomatal sensitivity coefficients. Jack pine was, however, more sensitive to inhibition of photosynthesis by elevated temperatures and, as a consequence, stomata closed as temperature and the vapor pressure deficit increased during mid day. In contrast, black spruce was much less effected. These differences could have profound implications for simulating regional scale hydrometeorology over large areas dominated by monospecific stands in the NEESPI domain.
DE: 3307 Boundary layer processes
DE: 1655 Water cycles (1836)
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting