Table 1.
Characteristics of the four FACE experiments
| Name | Rhinelander | Duke | ORNL | POP-EUROFACE |
|---|---|---|---|---|
| Location | Rhinelander, WI | Durham, NC | Oak Ridge, TN | Tuscania (Viterbo), Italy |
| Latitude, longitude | 45°40′N, 89°37′W | 35°58′N, 79°05′W | 35°54′N, 84°20′W | 42°22′N, 11°48′E |
| Mean annual precipitation, mm | 810 | 1,140 | 1,390 | 818* |
| Mean annual temperature, °C | 4.9 | 15.5 | 14.2 | 14.1 |
| Growing season,† days | 150 | 200 | 190 | 247 |
| Soil classification (US) | Alfic Haplorthod | Ultic Hapludalf | Aquic Hapludult | Pachic Xerumbrept |
| Soil texture | Sandy loam | Clay loam | Silty clay loam | Loam and silt loam |
| Total soil N, g·kg−1 | 1.20 | 0.79 | 1.12 | 1.1–1.4 |
| Overstory vegetation | Populus tremuloides Michx., Acer saccharum Marsh., Betula papyrifera Marsh | Pinus taedaL. | Liquidambar styraciflua L. | Populus alba L. P. nigra L. P. x euramericana Dode Guinier |
| Peak leaf area index,‡ m2·m−2 | 2.7–3.4 | 3.4 | 5.5 | 4.6–7.4 |
| Year planted | 1997 | 1983 | 1988 | 1999 |
| Year of treatment initiation | 1997 | 1997 | 1998 | 1999 |
Data are taken from ref. 10.
*The POP-EUROFACE experiment used irrigation to avoid drought, so inferences regarding precipitation should be avoided for this site.
†For deciduous stands, the growing season is the duration that trees have leaves; for the evergreen system, it is the period of active stem growth.
‡Values of leaf area index are expressed as leaf area per ground area. Values for the Duke FACE site are projected, and values for the hardwood sites are one-sided.