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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.