HR: 0800h
AN: B11A-1009    [Abstracts]
TI: Fog and Vegetation on the California Channel Islands: A Tree Ring and Satellite Analysis
AU: * Williams, P
EM: williams@geog.ucsb.edu
AF: University of California, Santa Barbara, Geography Department 3611 Ellison Hall, Santa Barbara, CA 93117 United States
AU: Still, C
EM: still@icess.ucsb.edu
AF: University of California, Santa Barbara, Geography Department 3611 Ellison Hall, Santa Barbara, CA 93117 United States
AU: Fischer, D
EM: fischer@geog.ucsb.edu
AF: University of California, Santa Barbara, Geography Department 3611 Ellison Hall, Santa Barbara, CA 93117 United States
AU: Leavitt, S
EM: sleavitt@ltrr.arizona.edu
AF: University of Arizona, Laboratory of Tree Ring Research 105 W. Stadium Bldg. 51, Tucson, AZ 85721 United States
AB: Tree-ring width and stable isotope composition of rare pines in Channel Islands National Park reflect annual variations in water availability. α-cellulose was isolated from Bishop Pine ( Pinus muricata) cores from Santa Cruz Island (SCI). Individual annual rings from 1979-2003 were analyzed for carbon-13 (n = 4 trees). An average δ¹³C chronology was created and annual atmospheric ¹³CO₂ at La Jolla Pier, CA was subtracted to detrend the chronology for the steadily decreasing δ¹³C of atmospheric CO₂ that has resulted from anthropogenic emissions and biomass burning. Early and latewood δ¹³C were negatively correlated with annual rainfall in the SCI central valley (r = -0.5057, r = -0.6447, respectively). An annual ring width chronology (1908-2004) was also created from Torrey Pine ( Pinus torreyana) tree cores (n=17) collected on Santa Rosa Island. Ring width was positively correlated with SCI rainfall (r = 0.6993). On average, 87% of this precipitation falls between November and March. However, tree growth as measured by dendrometer bands continues throughout the summer months suggesting an additional source of water. Summer is also the peak fog season for the Islands. The last rain of the 2004 growing season was on March 1 and monthly NDVI data derived from MODIS show that the vast majority of the vegetation on SCI was dormant by mid-May. When summer NDVI is overlaid on an image of average summer-time 10:30AM cloud cover, created using a derivative of the MODIS cloud-mask product, it appears that the greenest parts of SCI during summer months are those regions that experience the most summertime cloud cover. The distribution of Bishop Pine also seems to be limited to elevations that intercept cloud banks, as opposed to regions that simply experience cloud cover. It is therefore possible that these tree ring width and stable isotope records document the intensity of summer fog inundation in addition to rainfall. Because we have observed consistently significant isotopic differences between rain and fog water on SCI, we believe that tree ring δ¹⁸O and δ²H (currently in analysis) will help us discern an annual fog signal. Reconstructing annual fog water usage will allow us to determine the ecological importance of this water source for the many rare and endemic coastal California conifers. We hope to use these methods to detect fog signals in tree rings from other fog-dependent ecosystems, such as tropical montane cloud forests.
DE: 0400 BIOGEOSCIENCES
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: Fall Meeting 2005