Biochemical bases for the biogeography of C3/C4 grasses and implications for changing distributions since the last glacial maximum
- NASA/GSFC, Greenbelt, MD (United States)
- Duke Univ., Durham, NC (United States)
- Carnegie Institution of Washington, Stanford, CA (United States)
Differential distributions of C3 and C4 grass taxa correlate with geographic and climatic factors. A simple model based on the temperature dependence of the photosynthetic quantum yield of C3 plants and the lack of response of the C4 quantum yield to temperature is used to predict the global distribution of C4 grasses at current atmospheric CO2 concentrations and climate. The model predicts a cross over temperature at which the quantum yield responses intersect; at temperatures above the cross over point C4 grasses are favored over C3. The cross over temperature is about 22{degrees}C at current atmospheric CO2 concentrations. Using this criterion an accurate 1x1 degree map of C4 grass dominance over C3 grasses is produced from climatological mean monthly temperatures. Accuracy is improved by considering the co-occurrence of sufficient rainfall for growth during the months warm enough for C4 dominance. Rising temperatures and CO2 concentrations since the last glacial maximum (LGM) are expected to have an impact on past C4 grass distributions. We have used climate generated by the NCAR CCM to predict the extent of climatic regions favoring C4 over C3 since the LGM. Though low temperatures favor C3 photosynthesis, the low CO2 concentrations in the past more than off-set this effect. The extent of C4 favorable climates are predicted to have been greater during the LGM and have shrunk since then. The model does not take into account important biotic factors such as competition for light and herbivory or abiotic factors such as fire frequency that can affect the dominance of grasslands over other vegetation types.
- OSTI ID:
- 95768
- Report Number(s):
- CONF-9507129-; ISSN 0012-9623; TRN: 95:004728-0033
- Journal Information:
- Bulletin of the Ecological Society of America, Vol. 76, Issue 2; Conference: 80. anniversary of the transdisciplinary nature of ecology, Snowbird, UT (United States), 30 Jul - 3 Aug 1995; Other Information: PBD: Jun 1995
- Country of Publication:
- United States
- Language:
- English
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