Control of transpiration from the upper canopy of a tropical forest: the role of stomatal, boundary layer and hydraulic architecture components Export

@article{citeulike:4301731, abstract = {Concurrent, independent measurements of stomatal conductance (gs), transpiration (E) and microenvironmental variables were used to characterize control of crown transpiration in four tree species growing in a moist, lowland tropical forest. Access to the upper forest canopy was provided by a construction crane equipped with a gondola. Estimates of boundary layer conductance (gb) obtained with two independent methods permitted control of E to be partitioned quantitatively between gs and gb using a dimensionless decoupling coefficient (03A9) ranging from zero to 1. A combination of high gs (c. 3002013600 mmol m22122 s22121) and low wind speed, and therefore relatively low gb (c. 1002013800 mmol m22122 s22121), strongly decoupled E from control by stomata in all four species (03A9= 0.720130.9). Photosynthetic water-use efficiency was predicted to increase rather than decrease with increasing gs because gb was relatively low and internal conductance to CO2 transfer was relatively high. Responses of gs to humidity were apparent only when the leaf surface, and not the bulk air, was used as the reference point for determination of external vapour pressure. However, independent measurements of crown conductance (gc), a total vapour phase conductance that included stomatal and boundary layer components, revealed a clear decline in gc with increasing leaf-to-bulk air vapour pressure difference (Va because the external reference points for determination of gc and Va were compatible. The relationships between gc and Vc and between gs and Vs appeared to be distinct for each species. However, when gs and gc were normalized by the branch-specific ratio of leaf area to sapwood area (LA/SA), a morphological index of potential transpirational demand relative to water transport capacity, a common relationship between conductance and evaporative demand for all four species emerged. Taken together, these results implied that, at a given combination of LA/SA and evaporative demand scaled to the appropriate reference point, the vapour phase conductance and therefore transpiration rates on a leaf area basis were identical in all four contrasting species studied.}, address = {Hawaii Agriculture Research Centre, 99193 Aiea Heights Drive, Aiea, HI 96701, USA; Department of Botany, University of Hawaii at Manoa, Honolulu, HI 96822, USA; Biological Laboratories, Harvard University, Cambridge, MA 02138, USA; Departamento de Ciencias Biolgicas, Universidad de los Andes, Bogot, Colombia; Department of Biology, University of California, Los Angeles, CA 90024, USA}, author = {Meinzer, F. C. and Andrade, J. L. and Goldstein, G. and Holbrook, N. M. and Cavelier, J. and Jackson, P.}, citeulike-article-id = {4301731}, citeulike-linkout-0 = {http://dx.doi.org/10.1111/j.1365-3040.1997.tb00702.x}, citeulike-linkout-1 = {http://www3.interscience.wiley.com/cgi-bin/abstract/119148242/ABSTRACT}, doi = {10.1111/j.1365-3040.1997.tb00702.x}, journal = {Plant, Cell and Environment}, number = {10}, pages = {1242--1252}, posted-at = {2009-04-11 18:59:08}, priority = {2}, title = {Control of transpiration from the upper canopy of a tropical forest: the role of stomatal, boundary layer and hydraulic architecture components}, url = {http://dx.doi.org/10.1111/j.1365-3040.1997.tb00702.x}, volume = {20}, year = {1997} }

TY - JOUR ID - citeulike:4301731 L3 - citeulike-article-id:4301731 N2 - Concurrent, independent measurements of stomatal conductance (gs), transpiration (E) and microenvironmental variables were used to characterize control of crown transpiration in four tree species growing in a moist, lowland tropical forest. Access to the upper forest canopy was provided by a construction crane equipped with a gondola. Estimates of boundary layer conductance (gb) obtained with two independent methods permitted control of E to be partitioned quantitatively between gs and gb using a dimensionless decoupling coefficient (03A9) ranging from zero to 1. A combination of high gs (c. 3002013600 mmol m22122 s22121) and low wind speed, and therefore relatively low gb (c. 1002013800 mmol m22122 s22121), strongly decoupled E from control by stomata in all four species (03A9= 0.720130.9). Photosynthetic water-use efficiency was predicted to increase rather than decrease with increasing gs because gb was relatively low and internal conductance to CO2 transfer was relatively high. Responses of gs to humidity were apparent only when the leaf surface, and not the bulk air, was used as the reference point for determination of external vapour pressure. However, independent measurements of crown conductance (gc), a total vapour phase conductance that included stomatal and boundary layer components, revealed a clear decline in gc with increasing leaf-to-bulk air vapour pressure difference (Va because the external reference points for determination of gc and Va were compatible. The relationships between gc and Vc and between gs and Vs appeared to be distinct for each species. However, when gs and gc were normalized by the branch-specific ratio of leaf area to sapwood area (LA/SA), a morphological index of potential transpirational demand relative to water transport capacity, a common relationship between conductance and evaporative demand for all four species emerged. Taken together, these results implied that, at a given combination of LA/SA and evaporative demand scaled to the appropriate reference point, the vapour phase conductance and therefore transpiration rates on a leaf area basis were identical in all four contrasting species studied. IS - 10 JF - Plant, Cell and Environment AD - Hawaii Agriculture Research Centre, 99193 Aiea Heights Drive, Aiea, HI 96701, USA; Department of Botany, University of Hawaii at Manoa, Honolulu, HI 96822, USA; Biological Laboratories, Harvard University, Cambridge, MA 02138, USA; Departamento de Ciencias Biolgicas, Universidad de los Andes, Bogot, Colombia; Department of Biology, University of California, Los Angeles, CA 90024, USA EP - 1252 TI - Control of transpiration from the upper canopy of a tropical forest: the role of stomatal, boundary layer and hydraulic architecture components VL - 20 SP - 1242 AU - Meinzer, FC AU - Andrade, JL AU - Goldstein, G AU - Holbrook, NM AU - Cavelier, J AU - Jackson, P PY - 1997/// UR - http://dx.doi.org/10.1111/j.1365-3040.1997.tb00702.x ER -