HR: 15:10h
AN: B53D-06    [Abstracts]
TI: Constraining spatial patterns and secular trends of springtime phenology with contrasting models based on plant phenology gardens and carbon dioxide flux networks
AU: * White, M A
EM: mikew.usu@gmail.com
AF: Utah State University, Department of Watershed Sciences, Logan, UT 84322-5210, United States
AU: Baldocchi, D D
EM: baldocchi@nature.berkeley.edu
AF: University of California, Berkeley, Department of Environmental Science, Policy & Management, Berkeley, CA 94720-3110, United States
AU: Schwartz, M D
EM: mds@uwm.edu
AF: Department of Geography, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, United States
AB: Shifts in the timing and distribution of spring phenological events are a central feature of global change research. Most evidence, especially for multi-decade records, indicates a shift towards earlier spring but with frequent differences in the magnitude and location of trends. Here, using two phenology models, one based on first bloom dates of clonal honeysuckle and lilac and one based on initiation of net carbon uptake at eddy covariance flux towers, we upscaled observations of spring arrival to the conterminous US at 1km resolution. The models shared similar and coherent spatial and temporal patterns at large regional scales but differed at smaller scales, likely attributable to: use of cloned versus extant species; chilling requirements; model complexity; and biome characteristics. Our results constrain climatically driven shifts in 1981 to 2003 spring arrival for the conterminous US to between -2.7 and 0.1 day/23 years. Estimated trend differences were minor in the biome of model development (deciduous broad leaf forest) but diverged strongly in woody evergreen and grassland areas. Based on comparisons with the normalized difference vegetation index (NDVI) and a limited independent ground dataset, predictions from both models were consistent with observations of satellite-based greenness and measured leaf expansion. First bloom trends, which were mostly statistically insignificant, were also consistent with NDVI trends while the net carbon uptake model predicted extensive trends towards earlier spring in the western US that were not observed in the NDVI data, showing the implication of model application outside the biome range of initial development.
DE: 0429 Climate dynamics (1620)
DE: 0476 Plant ecology (1851)
DE: 0480 Remote sensing
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting