FIRE EFFECTS GUIDE - National Wildfire Coordinating Group

levels of moisture content. (See II.C.2., this Guide.)
In the Alaskan interior, maximum foliar moisture content levels for
Labrador tea (Ledum decumbens) were only 145 percent, and that peak
value occurred about a month after the maximum moisture values were
reached in associated deciduous shrub species (Norum and Miller
1981). Moisture content of new leaves of chamise (Adenostoma
fasciculatum) in California were at 125 percent in late May, dropped to
about 60 percent in early September, and rose to about 90 percent
when the plants again became physiologically active in early December
(Dell and Philpot 1965). Maximum moisture levels for galberry foliage
(Ilex glabra) averaged about 140 percent in North Carolina, while
minimum values were about 100 percent (Wendel and Story 1962).
Maximum values for redbay (Persea borbonia) foliage were about 120
percent, while fall and winter minima were around 60 percent (ibid.).
f. Herbaceous plants. Herbaceous moisture content can also vary
significantly among species. Moisture levels can be much higher at the
beginning of the growing season than for other species groups because
all of the plant is new tissue. Also, because there is no residual
material, all of the plant can become cured, sometimes before the end
of the growing season. This is especially notable for grasses and other
species in areas with hot, dry summer weather. In north Idaho, moisture
content of cheatgrass (Bromus tectorum), an annual grass, for example,
was measured to be 150 percent on June 20, but was only 9 percent on
July 20 (Richards 1940). All of the plant material, once cured, responds
to atmospheric conditions as a dead fine fuel, as reflected by the 9
percent moisture level just cited.
Some species of grasses and forbs in some regions can produce new
growth in the fall, after a summer of quiescence, thus causing fall greenup
and associated increase in moisture content. Green-up is caused by
renewed growth of perennial species and germination of seeds.
Some herbaceous species do not cure and dry out during the summer,
rather only begin a significant amount of curing as frost occurs in the
fall. In north Idaho, moisture content of fireweed (Epilobium
angustifolium) plants was 426 percent on June 20 and 241 percent on
September 10 (ibid.). In interior Alaska, bluejoint reedgrass
(Calamagrostis canadensis) was first measured at about 400 percent
moisture content on May 27 when the plants had about 1 to 1-1/2 feet
of leaf growth. Moisture content of plants declined to about 260 percent