HR: 14:30h
AN: H32E-03    [PDF]
TI: The Influence Of Water Tracks And Hillslope Position On The Physiology Of The Dominant Plant Species In The Imnavait Creek Watershed, Alaska
AU: * Griffin, K L
EM: griff@LDEO.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W 6 Biology, Palisades, NY 10964 United States
AU: Epstein, D J
EM: dje@columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W 6 Biology, Palisades, NY 10964 United States
AU: Shapiro, J B
EM: jbs59@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W 6 Biology, Palisades, NY 10964 United States
AU: Boelman, N T
EM: nboelman@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W 6 Biology, Palisades, NY 10964 United States
AU: Stieglitz, M
EM: marc@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W 6 Biology, Palisades, NY 10964 United States
AB: Within a small arctic tundra watershed located on the north slope of Alaska, we asked if plant abundance and physiological performance are linked to hillslope position by the hydrologic processes controlling nutrient availability. Our prediction was that down slope sites and within water track sites should have the greatest nutrient availability resulting in the highest photosynthetic capacity and productivity. To examine these relationships, two transects were established in the Imnavait Creek watershed, running from the northern ridge crest to a beaded stream. In total, 16 sites, one water track (WT) and one non water track (NWT), from 8 locations, each 100 m apart were examined. At each site, soil moisture, thaw depth, canopy water status (from spectral reflectance) and species diversity were recorded. Chlorophyll fluorescence was used assess the maximum capacity of each species to transport electrons within the photosynthetic membranes of individual leaves (ETR$_{MAX}$), a variable we expect to reflect both leaf N and general photosynthetic capacity. Significant differences were found within and among the major functional groups of plants growing in the watershed. In the two deciduous shrubs, {\it Betula nana} and {\it Salix pulchra}, ETR$_{MAX}$ generally decreased down slope but no significant difference were found between the WT and NWT sites. By contrast, ETR$_{MAX}$ in {\it Rubus chamaemors}, also a deciduous species, showed an initial decrease at the first two locations, but then remained constant further down slope and between WT and NWT sites. In the evergreen plants, {\it Ledum palustre} differed in that the maximum ETR$_{MAX}$ was found at the mid-slope locations while {\it Vaccinium vitis-idaea} had a characteristic decrease in ETR$_{MAX}$ down slope, with a large difference between WT and NWT at the first location. The forb {\it Petasites frigidus} displayed a unique pattern, with large difference in ETR$_{MAX}$ between WT and NWT at sites 4 and 5, the last two locations at which this species could be found. Finally, the only graminoid species studied, {\it Eriophorum vaginatu}, ETR$_{MAX}$ decrease down slope in a linear fashion and had the highest absolute ETR$_{MAX}$. Additionally leaf gas-exchange was measured in {\it Salix pulchra} and leaf N and canopy reflectance was measured at each site. Together, our results demonstrate that while hillsope position has a significant effect on the physiology, growth and diversity of species, the relationships were not as hypothesized. Clearly other ecological, morphological or environmental factors are contributing to the productivity of the watershed and ultimately impacting the biogeochemistry of this important ecosystem.
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 1640 Remote sensing
DE: 1851 Plant ecology
DE: 9315 Arctic region
SC: Hydrology [H]
MN: 2003 Fall Meeting