Chapter

Global Change and Mediterranean-Type Ecosystems

Volume 117 of the series Ecological Studies pp 326-342

Ecosystem Response to Elevated CO2: Nutrient Availability and Nutrient Cycling

  • W. D. Stock
  • , G. F. Midgley

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Abstract

Atmospheric CO2 levels have risen from an estimated preindustrial concentration of 280µLL-1 (Friedli et al., 1986; Neftel et al., 1985) to 350µLL-1 today (Boden et al., 1990) and, even using conservative assumptions regarding future energy sources, could increase to 600 µLL-1 by the end of the next century (Ausubel et al., 1988). The increase in agricultural crop yield which could result from a doubling of preindustrial CO2 levels has been suggested to be in the range of 30–40% (Kimball, 1983; Cure and Acock, 1986). However, natural ecosystem responses to increasing atmospheric CO2 levels are more difficult to predict, as their mechanistic basis remains poorly understood (Bazzaz, 1990), especially in terms of system processes and interactions between system components (Morison, 1990). Such an understanding depends heavily on the elucidation of the linkages between plant carbon uptake, carbon allocation, and nutrient cycling. Because these processes interact, disruption of any one often induces changes in others, which then leads to either positive reinforcement or negative feedback at the ecosystem level. This interaction is critical for the ultimate structural, functional, and floristic nature of the altered ecosystem. Natural ecosystems of certain Mediterranean climate regions have been shown to be altered substantially by changes in nutrient availability (Specht, 1963) in terms of species composition and system functioning, and it appears that rising atmospheric C02 levels may hold a similar threat, but at a global scale.