HR: 1340h
AN: B43B-0266    [Abstracts]
TI: Do Amazonian Forests Get Greener in Dry Season?
AU: * Myneni, R B
EM: rmyneni@bu.edu
AF: Dept of Geography, Boston University, 675 Commonwealth Ave, Boston, MA 02215 United States
AU: Yang, W
EM: ywze@crsa.bu.edu
AF: Dept of Geography, Boston University, 675 Commonwealth Ave, Boston, MA 02215 United States
AU: Su, Y
EM: yinsu@crsa.bu.edu
AF: Dept of Geography, Boston University, 675 Commonwealth Ave, Boston, MA 02215 United States
AU: Huete, A
EM: ahuete@Ag.arizona.edu
AF: Dept of Soil, Water and Environmental Science, P.O. Box 210038, Tucson, AZ 85721 United States
AU: Nemani, R R
EM: ramakrishna.r.nemani@nasa.gov
AF: NASA Ames Research Center, NASA Ames Research Center, Moffett Field, CA 94035 United States
AU: Didan, K
EM: kamel@Ag.arizona.edu
AF: Dept of Soil, Water and Environmental Science, P.O. Box 210038, Tucson, AZ 85721 United States
AB: Amazonian rainforests form the largest contiguous, undisturbed forest on our planet, influencing global climate, water, and carbon dynamics, and housing the largest reservoir of biological diversity. Yet the metabolism at that place is poorly understood due to complex patterns of moisture, sunlight, and biologic constraints on productivity. Small-scale plot and flux tower studies have shown carbon fixation increasing in the dry season, other experiments show light augmentation in wet season increased vegetation activities significantly, and modeling studies suggest these tropical forests may be light-limited. We investigated what is going on at large scale by remotely sensed data. We found LAI of broadleaf forests increase dramatically at the beginning of dry season, keep relatively constant high from middle to end of dry season, and drop steeply entering wet season, the variation could be more than 20%. Further investigation reveals that in the whole basin region, the average annual rainfall with a dry season of five months or less is more than the best rainfall supply for forest. If the dry month really long enough with nine or more months, the average annual rainfall would make the forest suffer water stress, yet the total area of this region is only 1.55%. While pastures in nearly the same region display totally different behavior. Our results provide evidence to the hypothesis that tropical forests may be light-limited, and we attribute the green up in dry season to (1) increase of area per leaf, (2) increase of leaf numbers, or (3) increase of density of chlorophylls in leaves.
DE: 0429 Climate dynamics (1620)
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0480 Remote sensing
DE: 0495 Water/energy interactions (1878)
SC: Biogeosciences [B]
MN: Fall Meeting 2005