Table III.
The response of leaf respiration to changes in (CO2) for species grown at long-term elevated (CO2) experiments
The mean respiration rate and its sem are given on an area basis and a dry weight basis. n indicates the number of plots or open-top chambers from which measurements of each treatment were made. Bold values show the critical long-term comparison of leaves grown and measured at their growth concentrations. An asterisk indicates that leaves grown and measured at elevated (CO2) have significantly different rates (P < 0.05) to those grown and measured at current ambient (CO2).
| a) Respiration on Leaf Area Basis (μmol O2 m−2 s−1)
| ||||||
|---|---|---|---|---|---|---|
|
|
n
|
Growth CO2 concentration (μmol mol−1)
|
Measurement CO2 concentration (μmol mol−1)
|
2000
|
||
| 0 | 368 | 550/700 | ||||
| Sugar maple | 3 | 368 | 0.54 ± 0.06 | 0.54 ± 0.06 | 0.54 ± 0.05 | 0.55 ± 0.06 |
| 560 | 0.55 ± 0.02 | 0.55 ± 0.03 | 0.54 ± 0.03 | 0.55 ± 0.04 | ||
| B. papyrifera | 3 | 368 | 0.86 ± 0.12 | 0.89 ± 0.11 | 0.82 ± 0.12 | 0.83 ± 0.10 |
| 560 | 0.85 ± 0.03 | 0.86 ± 0.04 | 0.82 ± 0.02 | 0.82 ± 0.01 | ||
| G. max cv pana | 4 | 368 | 1.27 ± 0.10 | 1.28 ± 0.10 | 1.29 ± 0.10 | 1.28 ± 0.09 |
| 550 | 1.54 ± 0.05 | 1.55 ± 0.06 | 1.56 ± 0.06* | 1.57 ± 0.05 | ||
| P. taeda | 3 | 368 | 0.76 ± 0.10 | 0.76 ± 0.10 | 0.76 ± 0.10 | 0.76 ± 0.09 |
| 550 | 0.78 ± 0.03 | 0.78 ± 0.03 | 0.78 ± 0.02 | 0.78 ± 0.02 | ||
| P. tremuloides | 3 | 368 | 1.37 ± 0.09 | 1.39 ± 0.08 | 1.39 ± 0.07 | 1.39 ± 0.07 |
| 560 | 1.36 ± 0.06 | 1.37 ± 0.06 | 1.37 ± 0.06 | 1.38 ± 0.06 | ||
| Q. geminata | 8 | 368 | 0.59 ± 0.04 | 0.60 ± 0.04 | 0.59 ± 0.04 | 0.60 ± 0.04 |
| 700 | 0.73 ± 0.03 | 0.75 ± 0.04 | 0.74 ± 0.05* | 0.75 ± 0.05 | ||
| Q. myrtifolia | 8 | 368 | 0.66 ± 0.06 | 0.65 ± 0.06 | 0.62 ± 0.05 | 0.63 ± 0.05 |
| 700 | 0.72 ± 0.08 | 0.72 ± 0.07 | 0.73 ± 0.08 | 0.72 ± 0.08 | ||
| b) Respiration on leaf dry mass basis (μmol O2 kg−1 s−1)
| ||||||
|---|---|---|---|---|---|---|
| Species
|
n
|
Growth CO2 concentration (μmol mol−1)
|
Measurement CO2 concentration (μmol mol−1)
|
|||
| 0 | 368 | 550/700 | 2000 | |||
| Sugar maple | 3 | 368 | 9.01 ± 1.12 | 8.92 ± 1.1 | 8.87 ± 1.05 | 9.14 ± 1.1 |
| 560 | 8.27 ± 1.3 | 8.31 ± 0.21 | 8.30 ± 0.22 | 8.29 ± 0.34 | ||
| B. papyrifera | 3 | 368 | 11.5 ± 1.4 | 12.0 ± 1.2 | 11.1 ± 1.5 | 11.2 ± 1.3 |
| 560 | 11.5 ± 0.1 | 11.6 ± 0.2 | 11.2 ± 0.1 | 11.2 ± 0.3 | ||
| G. max cv pana | 4 | 368 | 20.5 ± 1.7 | 20.6 ± 1.7 | 20.7 ± 1.7 | 20.7 ± 1.6 |
| 560 | 25.0 ± 0.9 | 25.1 ± 0.9 | 25.3 ± 0.9* | 25.5 ± 0.8 | ||
| P. taeda | 3 | 368 | 5.07 ± 0.24 | 5.08 ± 0.19 | 5.08 ± 0.15 | 5.09 ± 0.11 |
| 550 | 5.56 ± 0.05 | 5.56 ± 0.06 | 5.59 ± 0.08* | 5.55 ± 0.10 | ||
| P. tremuloides | 3 | 368 | 15.1 ± 2.0 | 15.1 ± 2.1 | 15.2 ± 2.1 | 15.2 ± 2.2 |
| 560 | 15.4 ± 0.7 | 15.6 ± 0.7 | 15.7 ± 0.6 | 15.7 ± 0.6 | ||
| Q. geminata | 8 | 368 | 3.07 ± 0.23 | 3.14 ± 0.22 | 3.12 ± 0.22 | 3.13 ± 0.24 |
| 700 | 3.28 ± 0.21 | 3.34 ± 0.21 | 3.28 ± 0.20 | 3.34 ± 0.24 | ||
| Q. myrtifolia | 8 | 368 | 4.57 ± 0.47 | 4.54 ± 0.43 | 4.31 ± 0.38 | 4.41 ± 0.40 |
| 700 | 4.75 ± 0.63 | 4.72 ± 0.60 | 4.79 ± 0.64 | 4.76 ± 0.68 | ||