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Title
Proceedings of the Symposium on Global and Environmental Monitoring

836
CHARACTERIZING TREE INFORMATION
ON SAMPLED AREAS
Prior to the RPA, FIA researchers determined
forest type by the percent foliar cover or the
percent stocking of trees on sample areas. Over
time, shifts in relative tree foliar cover or
stocking between two inventories could be
measured, and conclusions drawn about changes in
tree species composition.
Researchers also recorded the age of dominant
trees, usually by taking increment cores and
measuring tree height. The cores, particularly
those showing total tree age, are chronological
records of growth changes. The changes in tree
growth are often related to climatic changes
(Hornbeck and Smith, 1985). Sample observations
from increment cores or from remeasurement
comparisons between two monitoring occasions also
serve as a measure of periodic diameter growth.
Some additional, but more subjective, evaluations
of forest health were also made for detecting
tree defects, pathogens and insects.
Prior to the mid-1960s, tree data in Alaska were
measured on fixed-area plots. In the mid-1960s,
FIA changed plot configurations to a
variable-area plot format, which are more
efficient for measuring tree data (Bitterlich,
1984). This is especially true where interest
focuses on larger trees of greater economic
importance. Some FIA units retained some
fixed-area plots for re-measurement purposes.
Such tree measurements provide a limited but
sound baseline data set for objective
observations of changes in forest health and
vigor. But little information was collected on
the health and vigor of non-tree vegetation in
sample areas.
CHARACTERIZING ALL VEGETATION
ON SAMPLED AREAS
In the early 1970s, a powerful new procedure was
established for characterizing all vegetation
from sample points. The procedure, the
horizontal-vertical (HV) vegetation profile
system, involves estimating plant species foliar
cover stratified by the natural non-tree
vegetation layers. The observations are made on
100-square meter, fixed-area plots. Initially
developed in the southeastern United States
(Cost, 1979), the system has been modified for
use in Alaska (Mead et al, 1986).
These non-tree vegetation observations from
fixed-area plots are merged with tree
observations from variable-area plots in a way
that produces a detailed vegetation profile of
foliar cover by plant species. These profile
data start at the forest floor and rise to the
top of the highest sampled tree.
During the early 1980s, the Anchorage FIA
Research Work Unit cooperated with the University
of Alaska to develop a set of vegetation biomass
prediction coefficients within the HV vegetation
profile system. These were first prepared for
the major Alaska tree species (Yarie and Mead,
1982). Subsequent studies developed biomass
coefficients for the major shrub, forb, grass,
moss and lichen species of the Tanana River basin
(Yarie and Mead, 1988), and for southeast Alaska
(Yarie and Mead, 1989).
This development of biomass coefficients, based
on species foliar cover and their relative
vertical position in the stand, empowered
inventory users to predict the oven-dry weight of
foliar biomass per hectare (Mead et al, 1986).
The technique has promise as a valuable tool for
predicting the animal carrying capacity of a
given vegetation condition. Wildlife information
also can be gathered by determining plant species
and degree of use in a stand.
Having taken the major step of developing biomass
coefficients to predict tree, shrub, forb, grass,
moss and lichen biomass in Alaska, it is
relatively easy to estimate plant carbon content
(Birdsey, In Press). This allows us to predict
the carbon sequestering abilities of various
vegetation complexes.
This proposed monitoring system should allow us
to determine which plants are dropping out of or
encroaching into the ecosystem over time, thus
flagging a change in the sensitive plant
composition. In some cases, this identification
will help in determining what additional
indicator-plant research is needed.
Overall, the HV vegetation profile system is
simple to use. When applied to non-tree
vegetation and coupled with standard forest
inventory tree sampling methods, it shows promise
in characterizing total vegetation health and
vigor.
LINKING FOREST HEALTH CHANGES
WITH PROBABLE STRESSORS
Linkages between change in forest health and
probable forest stressors must be developed in
order to estimate changes in vegetation health
and vigor, and to establish correlations to
changes in global climate. It is believed that,
given appropriate methods for observing changes
in plant stress or vigor, the standard forest
inventory procedures, coupled with the
horizontal-vertical vegetation profile system,
will provide general estimates of vegetation
health, biomass, and vigor by plant species. The
design will monitor all plants from the mosses
and lichens, up through the tallest trees in the
forest canopy.
It is further believed that, by using rigorous
documentation, including mapping of various
health and vigor conditions within the monitored
plot, changes over time can be observed through
subsequent revisitation and re- evaluation of the
areas.
However, we must develop a methodology for
consistently observing and recording variations
in vegetation health for various plant species.
It is important that this methodology be
sensitive enough to differentiate between normal
successional processes and climate induced
processes. This is a challenging undertaking.