HR: 08:15h
AN: H21I-02    [Abstracts]
TI: Impacts of Alien Tree Invasion on Evapotranspiration in Tropical Montane Cloud Forest in Hawai'i
AU: * Giambelluca, T W
EM: thomas@hawaii.edu
AF: Geography Dept., Univ. of Hawaii at Manoa, 2424 Maile Way, Saunders 445, Honolulu, HI 96822, United States
AU: Asner, G P
EM: gpa@stanford.edu
AF: Dept. of Global Ecology, Carnegie Institution, 260 Panama Street, Stanford, CA 94305, United States
AU: Martin, R E
EM: robin@globalecology.stanford.edu
AF: Geography Dept., Univ. of Hawaii at Manoa, 2424 Maile Way, Saunders 445, Honolulu, HI 96822, United States
AU: Martin, R E
EM: robin@globalecology.stanford.edu
AF: Dept. of Global Ecology, Carnegie Institution, 260 Panama Street, Stanford, CA 94305, United States
AU: Nullet, M M
EM: mnullet@hawaii.edu
AF: Geography Dept., Univ. of Hawaii at Manoa, 2424 Maile Way, Saunders 445, Honolulu, HI 96822, United States
AU: Huang, M
EM: mhuang@globalecology.stanford.edu
AF: Dept. of Global Ecology, Carnegie Institution, 260 Panama Street, Stanford, CA 94305, United States
AU: DeLay, J k
EM: delay@hawaii.edu
AF: Geography Dept., Univ. of Hawaii at Manoa, 2424 Maile Way, Saunders 445, Honolulu, HI 96822, United States
AU: Mudd, R G
EM: rmudd@hawaii.edu
AF: Geography Dept., Univ. of Hawaii at Manoa, 2424 Maile Way, Saunders 445, Honolulu, HI 96822, United States
AU: Takahashi, M
EM: mamit@hawaii.edu
AF: Geography Dept., Univ. of Hawaii at Manoa, 2424 Maile Way, Saunders 445, Honolulu, HI 96822, United States
AB: Hawaiian tropical montane cloud forests (TMCFs) are ecologically and hydrologically valuable zones. TMCFs in Hawai'i serve as refugia for the remaining intact native terrestrial plant and animal ecosystems, and are major sources of hydrologic input to surface water and groundwater systems. Invasion of alien tree species, with obvious effects on the ecological integrity of TMCFs, also threatens to impact the hydrological services these forests provide. Much speculation has been made about the hydrological effects of replacing native forest tree species with alien trees in Hawai'i, but until now no measurements have been made to test these assertions. We established two study sites, each equipped with eddy covariance and other micrometeorological instrumentation, one within native Metrosideros polymorpha forest and the other at a site heavily invaded by Psidium cattleianum, in the cloud forest zone of Hawai‘i Volcanoes National Park. We are conducting measurements of stand-level evapotranspiration, transpiration (using sapflow techniques), energy balance, throughfall, stemflow, and soil moisture at each site. Preliminary analysis of these measurements shows that the fraction of available energy used for evapotranspiration (ET Fraction) at the native site is much higher for wet canopy conditions. The ET Fraction at the native site has an annual cycle corresponding to the annual cycle in leaf area. Deviations from the annual cycle are more closely related to variations in canopy wetness than to variations in soil moisture. Overall, ET as a function of available energy is 27% higher at the invaded site than the native site. The difference in ET between the two sites is especially pronounced during dry canopy periods, during which the ET Fraction is 53% higher at the invaded site than the native site. Sapflow measurements using heat balance collars show that leaf-area-specific transpiration is much greater in invasive P. cattleianum trees than in remnant native M. polymorpha trees at the invaded site. These results indicate that the P. cattleianum invasion is altering the hydrological cycle of the TMCF where it is found, with potential significant negative consequences for island water supply.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 1813 Eco-hydrology
DE: 1814 Energy budgets
DE: 1818 Evapotranspiration
DE: 1836 Hydrological cycles and budgets (1218, 1655)
SC: Hydrology [H]
MN: 2007 Fall Meeting