a A RR 
where Sp and Sc are residual mean squares from the regression analysis and 
if d,e,P can be treated as constants relative to the COV(a,b) and if b and 
P can be treated as constants relative to the COV(d,e) (Draper and Smith 
1966, p55). 
Estimates of mean crown diameter, P, for the test stand and of the 
variance for this estimate, V(P), were then required. These were obtained 
by randomly locating 80 trees on the aerial photography and measuring the 
crown diameter of each tree.P and V(P) were calculated. These estimates of 
P and V(P) and the results of the two regressions relating biomass to crown 
diameter and relating crown diameter to the photo measurements were all 
combined to estimate the average woody biomass per tree and to estimate the 
standard error of the estimate using equations 3. and 4. 
RESULTS AND DISCUSSION 
The regression equations predicting woody biomass from crown diameter 
produced correlation coefficients, R, ranging from 0.62 for A. reficiens 
to O.81 for A. tortilis and Commiphora Sp. (Table2). With the exception of 
A. reficiens which had a relatively low sample size, all were significant 
Tous 
Oven dry weights ranged from 92.0 to 93.5% of the air dry weight for 
Acacia sp. but averaged 63.6% for Commiphora sp. The consistent oven dry to 
alr weight relationship between all biomass catagories of Acacia sampled 
allowed the use of a single mean relationship of 93.1%. However, the data 
suggest that a different relationship should be used for Commiphora species. 
It is probable that oven dry to air dry relationships can be developed for 
groups of tree species having similar wood properties, this will reduce the 
need for subsequent oven drying of field samples. 
The predictive regression equations obtained from the comparison of 
field and aerial photo measurements of crown diameter showed high and similar 
correlation coefficients for 35 mm and 70 mm films (Table 1). The uniformly 
high correlations between photo and field measurements of crown diameter 
using either 70 mm or 35 mm indicate both to be useable for aerial photo 
surveys of biomass within the region. 
Table 1. Regressions predicting crown diameter on the ground, Y (m) from 
crown diameter on photograph,X (mm) using two types of film 
  
  
FILM PHOTOGRAPHIC SCALE REGRESSION EQUATION CORR. COEF. 
35 mm 1:1317 Y 5 1.04*1.09X 0.93 
70 mm 1:2000 Y5;1.57*1.13X 0.93 
* Significant (P<.05) 
  
The "F' test for commonality of regressions (Freese ,1967) indicated 
that the regressions for A. mellifera. A. reficiens and A. tortilis were 
not sifnificantly different from one another. Similarly, the regressions 
for A. drepanolobium and Commiphora Sp. were not significantly different 
from each other. There were significant difference between the two groups, 
416 
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