FIGURE 10.1 Photomicrograph of a stomata on the underside of a leaf. Source: Dan Hungerford.
FIGURE 10.2 Role of Carbon and Photosynthesis in Global Carbon Cycle. Carbon in the deep oceans is massive, whereas active carbon is a small fraction of the total carbon pool. Carbon in the atmosphere pool is approximately 50% greater than the carbon of surface ocean waters and only slightly greater than the carbon pool in plant mass. Of the carbon pools active on short time frames, soil carbon is by far the greatest. Reproduced with permission from the Ecological Society of America.
FIGURE 10.3 Laboratory and Greenhouse Experiments. Diffusers and enclosures may be used to maintain constant elevated CO 2 levels, whereas greenhouses or other warming devices may be used to manipulate temperature. Courtesy of SCRI.
FIGURE 10.4 Decline in Single-plant Studies, Increase in Whole-vegetation Experiments. The blue bars indicate total number of publications from 1987 to 1996. The green bars indicate the change in percentage publication between the first half of the time period (1987 – 1991; top bar) and the second half of the time period (1992 – 1996; bottom bar). Reproduced with permission from the Ecological Society of America.
FIGURE 10.5 Increase in Biomass for Different Categories of Species (Herbaceous and Woody C 3 Plants, C 4 Species, and CAM Species). Graphs show an increase in biomass enhancement ratio, a measure of increase in biomass. Boxplots such as these indicate the 5th (bottom horizontal line), 25th (bottom line of box), 50th (midline of box), 75 th (top line of box), and 95th (upper horizontal line) percentile of the distribution. From Poorter, H. and Navas, M. L. 2003. Plant growth and competition at elevated CO2: On winners, losers and functional groups. New Phytologist 157, 175 – 198.
FIGURE 10.6 Effect of Experimental Conditions on Increase in Biomass Under Enhanced CO 2. (A) Biomass enhancement ratio of plants grown in isolation versus plants grown in monoculture. ( r 0.25, n 27, p 0.2). (B) Isolated plants versus plants grown in a mixed culture ( r 0.04, n 33, p 0.8). (C) Plants grown in monoculture versus plants grown in a mixture of species ( r 0.58, n 50, p 0.001). Dotted line 1:1. F rom Poorter, H. and Navas, M. L. 2003. Plant growth and competition at elevated CO2: On winners, losers and functional groups. New Phytologist 157, 175– 198.
FIGURE 10.7 Biomass Enhancement for Seven Tropical Plant Species Grown in Isolation and in a Mixed Community. The CO 2 enhancement observed in the isolated trial is not evident in the mixed community. From Poorter, H. and Navas, M. L. 2003. Plant growth and competition at elevated CO2: On winners, losers and functional groups. New Phytologist 157, 175 – 198.
FIGURE 10.8 Acclimation to Elevated CO 2 Over Time. Trees grown under elevated CO 2 show a strong response initially, but the response declines strongly with time. From Idso, S. B. 1999. The long-term response of trees to atmospheric CO2 enrichment. Global Change Biology 5, 493 – 495.
FIGURE 10.9 Active (a) and Passive (b) Warming Experiments. The active warming devices include the use of infrared warming lamps. Passive warming depends on blocking of air circulation or intensification of sunlight to create warmth. Passive warming devices are often simply circles or boxes of glass or clear plastic, which act much like miniature greenhouses but allow multispecies interactions and have minimal impact on received precipitation. (a) Courtesy of Charles Musil. (b) From the National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara.
FIGURE 10.10 Transplantation and Open-top Chamber Experiments. Transplantation preserves plant – plant interactions and soil properties. It is usually implemented with the movement of plants embedded in whole soil. Open- top chambers preserve plant and soil relationships over a limited area. Source: Finnish Forest Research Institute.
FIGURE 10.11 Free Air CO 2 Enrichment (FACE) Experiments. FACE experiments use massive diffusers to elevate CO 2 concentrations over a large area. Diffusers are often arrayed around a central measurement tower. (a) Courtesy of Jeffrey S. Pippen. (b) Courtesy of Professor Josef Nösberger, Swiss Face Experiment (ETH Zurich). (c) From Brookhaven National Laboratory.
FIGURE 10.12 Response to Warming. The effects of warming on soil moisture, soil respiration, mineralization, and plant productivity are shown for multiple studies from throughout the world. Measured mean effects at each study site are indicated by open circles; bars indicate 95% confidence intervals. The vertical line indicates no effect. From Rustad, L. E., et al. 2001. A meta-analysis of the response of soil respiration, net nitrogen mineralization, and aboveground plant growth to experimental ecosystem warming. Oecologia 126, 543 – 562.
FIGURE 10.13 Acclimation in Experimental and Natural Settings. Single-plant experiments seldom span long enough time frames to detect acclimation. Whole-ground experiments, usually conducted over longer time frames, clearly show the effect of acclimation. From Idso, S. B. 1999. The long-term response of trees to atmospheric CO2 enrichment. Global Change Biology 5, 493 – 495.
FIGURE 10.14 Slumping Arctic soils lead to changed vegetation composition. From Kokelj, S. V., et al. 2009. Origin and polycyclic behaviour of tundra thaw slumps, Mackenzie Delta Region, Northwest Territories, Canada. Permafrost and Periglacial Processes 20, 173 – 184.
Un- Figure 10.1Relevance of Living Plants to Atmospheric CO 2 Concentrations. The relationship of plants to atmospheric CO 2 is most important on timescales of 1 – 100 years. On scales of centuries, geologic processes such as mixing of the deep oceans are more important than plant influences. However, on very long timescales plants are once again important in determining atmospheric composition because buildup of plant material results in the formation of fossil fuels and accounts for buildup of oxygen in the atmosphere, with attendant implications for biogenic CO 2 production and consumption. Reproduced with permission from the Ecological Society of America.