canopy structure classes and the total volume occupied by 
vegetation material, as measured by the combined volume of 
the euphotic and oligophotic zones. 
Euphotic/ 
Oligophotic 
Threshold 
Cumulative Canopy Closur 
   
    
  
  
  
      
  
International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 3W14, La Jolla, CA, 9-11 Nov. 1999 
Open 
Gap 
Space 
  
  
10 
TZ 
  
60 
] Euphotic 
Zone 
  
  
  
E 4 | Oligophotic 
= Zone 
= 1 
= 
1 
1 Closed 
3 Gap 
Space 
  
  
  
  
     
0.1 
Canopy Closure 
Empty/Filled Threshold Value 
à $ Oligo. Zone. 
  
7 
  
Fig. 4. The Canopy Volume Method (Lefsky et al., 1999b) 
Fig. 5 presents canopy volume profile diagrams for 
representative young, mature and old-growth plots. These 
diagrams indicate, for each 1 meter vertical interval, the 
percent of each plot's 25 waveforms that belong to each of the 
four canopy structure classes. Young stands are characterized 
by short stature, a uniform canopy surface (as indicated by the 
height distribution of the interface between the euphotic zone 
and open gap space), and an absence of empty space within the 
canopy (ie. closed gap space). Mature stands are taller, but still 
are characterized by a uniform upper canopy surface. In 
contrast to young stands, mature stands have a large volume of 
closed gap space. Mature stands of Douglas-fir often have a 
high density of large trees with uniform DBH. The uniformity 
of size leads to the uniform canopy surface height, and the 
interception of light and other resources by these trees results in 
the absence of canopy material at lower levels. Old-growth 
stands are distinguished from mature stands by their uneven 
canopy surface, and the wide vertical distribution of each of the 
four canopy structure classes. Whereas stands from earlier 
stages in stand development have canopy structure classes in 
distinct vertical layers, in the old-growth stands each canopy 
structure class occurs throughout the height range of the stands. 
The continuous distribution of canopy surfaces from the top of 
the canopy to the ground has been cited as a key physical 
feature of old-growth forests distinguishing them from the 
simpler canopies of young and mature stands (Spies and 
Franklin, 1991) 
Scatterplots of predicted vs observed stand structure attributes 
are presented in Fig. 6. The strength of the relationships 
developed here are very strong in comparison to other remote 
sensing techniques, and compare favorably with allometric 
equations relating complementary aspects of individual tree 
geometry. Examination of the scatterplots indicates that the 
predicted values of aboveground biomass and LAI show no 
asymptotic tendency, even at extremely large values (1200 
Mg/ha Biomass, LAI of 12). The equation predicting biomass 
involved positive correlations with the total filled volume, and 
the number of waveforms taller than 55 m. The equation 
predicting LAI involved a positive correlation with the total 
filled volume and the open gap volume, and a negative 
correlation with the closed gap volume. This may be interpreted 
as suggesting that the all-sided surface area of leaves is 
proportional to the volume they are distributed in. Increases in 
the vertical range of the upper canopy surface tends to increase 
height (m) 
  
height (m) 
   
Intern 
LAI, and the pr 
to decrease LAI 
use the total 
scatterplots anc 
values of each 
other than the o 
Young Stand 
0 Volum 
Old- growtl 
(~250 ys 
60 
Ts 
© 
N 
o 
  
  
g RUM RD-C 
-= 100 
Observed 
00 À 
01* 
204 
-200 20 
Predic! 
Bio 
  
  
  
Fig. 6. Predic 
Metho 
The developme 
sensing will : 
organization, a 
organization. U 
made several i 
sensor with tw