185
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onventional
;. On
nail
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1:5000
:ions were
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ill scale
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sful upto
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) used
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3 teak
) height
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and volume
verted
nd best
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level
eparation
. volume
ttempted
using photo height and photo crown closure as independent variables for
teak trees against mean ground height and plot volume as dependent
variables . Various combinations with mean photo height and mean ground
height, mean ground dbh, plot volume and so also mean crown closure
and mean crown diameter were tried. Best results were obtained with
mean photo height and mean crown closure with plot volume. The S.E.
of the regression line varied from 5% to 3 0%. JOSHI ( 5 ) used photo
height and photo crown closure as independent variables for dry decidu
ous forests on various scales. The S.E. of the estimate was 3 0%.
It was noticed that the inclusion of parameter photo crown closure did
not significantly reduce the error of the regression line as almost all
the variation was accounted for by using photo tree height as the indepen
dent variable. No significant difference with different scales was
noticed.
"Area Determination"
In resource inventories the usual practice has been to transfer
the delineated forest types on maps and calculate the area of various
types by dot grid of varying intensity. Significant gains in precision,
time and cost have been reported by this method TOMAR ( 12 ). This
has necessarily reduced the error of scale variation inherent in aerial
photographs but the error of misinterpretation and also of the maps ie
transfer error etc. were not taken into account. TIWARI ( 7 ) carried
out investigations on the use of photo plot sampling method for Sal
forests of Dehra Dun. He accounted for the misinterpretation and scale
variation errors and compared the adjusted proportions with those
obtained by purely conventional methods. No significant difference was
obtained and use of method and aerial photographs was advocated for
working plan preparations. JOSHI ( 4 ) estimated the area proportions
of forest types on scales 1:5,000 to 1:20,000 and indicated no signifi
cant difference.
"Direct Estimation of Growing Stock"
Investigations were carried out for Sal forests on 1;20,000
scale. Initial stratification into three volume classes of nearly 100
cum per ha. range was done on the basis of photo height, crown
closure, crown diameter and texture of the tree canopy. Volume in 0.1
ha. circular plots was estimated on a number of photo plots on the
basis of stereograms covering the entire range of volume. Mean volume
in each stratum was adjusted by regression of photo volume and ground
volume of double plots. The S.E. of estimate varied from 5% to 2 0%.
The method gave encouraging results and better precision can be obtain
ed with larger scale and recent photographs.
RESOURCE INVENTORIES
Existing conventional management plans were made for small
units of forest areas and since they were directed towards scientific
management of forests and fulfilment of local demands they were unable to
supply data on wood resources for large industrial units. With a greater
number of species becoming of economic importance, the need for regional in
ventories which could provide sufficiently reliable data for large industrial