ORNL FACE Leaf Area Index (LAI)

Leaf area data are available for 1999-2006. There is a daily file
for each year which contains the leaf area index values (m2/m2).
Leaf area index (LAI, total one-sided leaf area above a unit of ground area)
was calculated for each plot for every day of the growing season.
Leaf area production in the spring was calculated from the fractional
transmittance of PAR (T), which was calculated from daily total PAR above
and below the canopy. A curve was fit to ln(T)/-k data, where
the extinction coefficient k was set such that maximum leaf area
production at budset (early to mid July) was equal to that determined
from litter basket collections. A canopy-averaged value of leaf mass per
unit leaf area was used to convert abscised leaf mass in litter baskets to
green leaf area. A curve was fit through litter basket data to generate
cumulative daily leaf area loss, which was subtracted from the leaf area
production curve to generate daily LAI.

The data were generated for the elevated CO2 rings 1 and 2, and
the ambient CO2 rings 3, 4, and 5. The following reference describes
these data in more detail: Norby RJ, Sholtis JD, Gunderson CA,
Jawdy SS. 2003. Leaf dynamics of a deciduous forest canopy: no
response to elevated CO2. Oecologia, DOI 10.1007/s00442-003-1296-2