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  • Key words Photosynthesis  (1)
  • Key words: climate change; permafrost; boreal peatlands; grassland/woodland boundary; northern Great Plains; warming; buffering; lagged responses.  (1)
  • Minnesota  (1)
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Keywords
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  • 1
    Electronic Resource
    Electronic Resource
    Effects of climate and atmospheric CO2 partial pressure on the global distribution of C4 grasses: present, past, and future (1998)
    Springer
    Oecologia 114 (1998), S. 441-454 
    Details
    ISSN: 1432-1939
    Keywords: Key words Photosynthesis ; C4 ; Climate change ; CO2 ; Grassland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract C4 photosynthetic physiologies exhibit fundamentally different responses to temperature and atmospheric CO2 partial pressures (pCO2) compared to the evolutionarily more primitive C3 type. All else being equal, C4 plants tend to be favored over C3 plants in warm humid climates and, conversely, C3 plants tend to be favored over C4 plants in cool climates. Empirical observations supported by a photosynthesis model predict the existence of a climatological crossover temperature above which C4 species have a carbon gain advantage and below which C3 species are favored. Model calculations and analysis of current plant distribution suggest that this pCO2-dependent crossover temperature is approximated by a mean temperature of 22°C for the warmest month at the current pCO2 (35 Pa). In addition to favorable temperatures, C4 plants require sufficient precipitation during the warm growing season. C4 plants which are predominantly graminoids of short stature can be competitively excluded by trees (nearly all C3 plants) – regardless of the photosynthetic superiority of the C4 pathway – in regions otherwise favorable for C4. To construct global maps of the distribution of C4 grasses for current, past and future climate scenarios, we make use of climatological data sets which provide estimates of the mean monthly temperature to classify the globe into areas which should favor C4 photosynthesis during at least 1 month of the year. This area is further screened by excluding areas where precipitation is 〈25 mm per month during the warm season and by selecting areas classified as grasslands (i.e., excluding areas dominated by woody vegetation) according to a global vegetation map. Using this approach, grasslands of the world are designated as C3, C4, and mixed under current climate and pCO2. Published floristic studies were used to test the accuracy of these predictions in many regions of the world, and agreement with observations was generally good. We then make use of this protocol to examine changes in the global abundance of C4 grasses in the past and the future using plausible estimates for the climates and pCO2. When pCO2 is lowered to pre-industrial levels, C4 grasses expanded their range into large areas now classified as C3 grasslands, especially in North America and Eurasia. During the last glacial maximum (∼18 ka BP) when the climate was cooler and pCO2 was about 20 Pa, our analysis predicts substantial expansion of C4 vegetation – particularly in Asia, despite cooler temperatures. Continued use of fossil fuels is expected to result in double the current pCO2 by sometime in the next century, with some associated climate warming. Our analysis predicts a substantial reduction in the area of C4 grasses under these conditions. These reductions from the past and into the future are based on greater stimulation of C3 photosynthetic efficiency by higher pCO2 than inhibition by higher temperatures. The predictions are testable through large-scale controlled growth studies and analysis of stable isotopes and other data from regions where large changes are predicted to have occurred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050468
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Long-term Perspectives on Lagged Ecosystem Responses to Climate Change: Permafrost in Boreal Peatlands and the Grassland/Woodland Boundary (2000)
    Springer
    Ecosystems 3 (2000), S. 534-544 
    Details
    ISSN: 1435-0629
    Keywords: Key words: climate change; permafrost; boreal peatlands; grassland/woodland boundary; northern Great Plains; warming; buffering; lagged responses.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in climate could have far-reaching consequences for ecosystems sensitive to changes in temperature and precipitation, such as boreal permafrost peatlands and grassland/woodland boundaries. The long-term data from our studies in these ecosystems suggest that transient responses of permafrost and vegetation to climate change may be difficult to predict due to lags and positive feedbacks related to vegetation and disturbance. Boreal permafrost peatlands comprise an ecosystem with strong local controls on microclimate that influence the formation and thaw of permafrost. These local controls may preserve permafrost during the transient stages of climate warming, producing lagged responses. The prairie–forest border region of the northern Great Plains has experienced frequent change and has complex dynamics involving transitions in the grassland composition of prairie and in the degree of woodiness in bordering forests. Fire frequency interacts with fuel loading and tree recruitment in ways that affect the timing and direction of change. Lags and thresholds could lead to sudden large responses to future climate change that are not readily apparent from current vegetation. The creation of adequate models to characterize transient ecosystem changes will require an understanding of the linkages among processes operating at the scale of 10s of meters and over long time periods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100210000047
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  • 3
    Electronic Resource
    Electronic Resource
    Landscape interactions among nitrogen mineralization, species composition, and long-term fire frequency (1990)
    Springer
    Biogeochemistry 11 (1990), S. 1-22 
    Details
    ISSN: 1573-515X
    Keywords: disturbance ; ecosystems ; forests ; indirect interactions ; landscape ecology ; Minnesota ; nitrogen ; nutrient cycling ; path analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Path analysis was used to determine the importance of long-term disturbance regime and the relative importances of correlations among vegetation patterns, disturbance history, and nitrogen (N) mineralization in old-growth forests of northwestern Minnesota. Leaf biomass (estimated by allometric equations), fire history (from fire scars on Pinus resinosa trees), and N mineralization rates (estimated from incubationsin situ) were determined from sample plots dominated by Betula papyrifera, Populus tremuloides, andP. grandidentata a mixture ofAcer saccharumandTilia americana, or Quercus borealis andOstrya virginiana. Results showed that topographic and soil-moisture controls on N mineralization, vegetation patterns, and disturbance are substantially stronger than is suggested by direct correlation. Indirect interactions among ecosystem variables played in important role. These interactions probably include the tendency for species that cycle large amounts of N to colonize more mesic sites that burned rarely in the past. Soil moisture was correlated both directly with N mineralization and indirectly, through its effects on vegetation pattern, and thus, litter quality. Although disturbance regime also depended on topography, the strengths of relationships between disturbance regime and other variables were relatively weak. These dependencies suggested that long-term fire regime is probably more a consequence than a cause for vegetation and fertility patterns. Topography, through its effects on soil moisture and microclimate, is an overriding influence on ecosystem properties, which in turn influence fire regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000849
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