HR: 0830h
AN: B51D-0994    [PDF]
TI: Rigidity and Plasticity of Leaf Carbon and Nitrogen Systematics in California Oaks
AU: * Krebs, T
EM: tkrebs@nature.berkeley.edu
AF: University of California at Berkeley, ESPM Ecosystem Sciences Division 151 Hilgard Hall #3110, Berkeley, CA 94720
AU: Baldocchi, D
EM: biomet@nature.berkeley.edu
AF: University of California at Berkeley, ESPM Ecosystem Sciences Division 151 Hilgard Hall #3110, Berkeley, CA 94720
AU: Xu, L
EM: lkxu@nature.berkeley.edu
AF: University of California at Berkeley, ESPM Ecosystem Sciences Division 151 Hilgard Hall #3110, Berkeley, CA 94720
AB: Mapping photosynthesis from space requires an understanding of photosynthetic efficiency. Current data sets prescribe global maps of photosynthetic parameters and relate them to greenness. It is the seasonality of greenness, and not of photosynthetic efficiency itself, which is presumed to drive photosynthesis. In fact, both greenness and photosynthetic efficiency convolve to produce seasonality in photosynthesis. If the scientific community is to globally retrieve photosynthetic rates from space, it must take this seasonality into account. We examine the rigidity and plasticity of photosynthetic capacity, its correlation to leaf nitrogen, and other leaf properties across geographic gradients of precipitation, soil moisture, air temperature, relative humidity and other measurables. In particular, these measurements focus on different species of oaks: blue oak (Quercus douglasii), coast live oak (Quercus agrifolia), black oak (Quercus velutina), and valley oak (Quercus lobata). Leaf chamber measurements with infrared gas analyzers and measurements of leaf specific mass, carbon isotope composition, and nitrogen content were performed in three Mediterranean ecosystems in California: Russell Reservation (coastal hills; oak woodland), Quail Ridge Reservation (near Lake Berryessa; Northern Coast Ranges; oak woodland), and Ione (Central Valley; oak savanna). Oaks of the same species adapted to more temperate microclimates such as shaded, north-facing slopes showed less pronounced seasonality in leaf nitrogen content and photosynthetic capacity. The comparison of evergreen and deciduous oak species yields relationships among leaf life span, specific leaf mass, and photosynthetic capacity that are consistent with the results of Reich. Our results confirm that oaks exhibit plasticity in their adaptation to more and less extreme environments. These results also explain why the deciduous oaks are less successful than the evergreen oaks near the coast and more successful in the interior. In addition, we examine the interactions between mesophyll conductance and leaf properties such as thickness and nitrogen content in driving the seasonality of apparent photosynthetic capacity. A new understanding of mesophyll conductance in relation to leaf thickness, leaf life span, and nitrogen content will be important to the study of isotopes.
DE: 0315 Biosphere/atmosphere interactions
DE: 0330 Geochemical cycles
DE: 0400 Biogeosciences
DE: 1040 Isotopic composition/chemistry
DE: 1812 Drought
SC: Biogeosciences [B]
MN: 2003 Fall Meeting