Table 1. Characteristics of the four FACE experiments
Characteristic DukeFACE AspenFACE ORNL-FACE POP-EUROFACE
Location Durham, NC Rhinelander, WI Oak Ridge, TN Tuscania (Viterbo), Italy
Latitude, longitude 35°58′N, 79°05′W 45°40′N, 89°37′W 35°54′N, 84°20′W 42°22′N, 11°48′E
Mean annual precipitation, mm 1,140 810 1,390 818*
Mean annual temperature, °C 15.5 4.9 14.2 14.1
Growing season, days 200 150 190 247
Soil classification (U.S.) Ultic Hapludalf Alfic Haplorthod Aquic Hapludult Pachic Xerumbrept
Soil texture Clay loam Sandy loam Silty clay loam Loam and silt loam
Total soil N, g·kg-1 0.79 1.20 1.12 1.1-1.4
Overstory vegetation Pinus taeda L. Populus tremuloides Michx., Acer saccharum Marsh., Betula papyrifera Marsh. Liquidambar styraciflua L. Populus alba L., P. nigra L., P. × euramericana Dode Guinier
Peak leaf area index, m2·m-2 3.4 2.7-3.4 5.5 4.6-7.4
Year planted 1983 1997 1988 1999
Year treatment initiation 1996 1997 1998 1999
  • * 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; the range in values describes portions of experimental plots occupied by different species after LAI was no longer increasing.