units was felt» So far an area of nearly 14.5 million ha. covering 
about 2 0 % of the entire forest area in different zones has been covered 
under regional inventories. The results have indicated useful potential 
for paper and pulp, saw milling, plywood and other wood based 
industries. One of the interesting facts revealed is that the total 
growing stock has been very much underestimated in the past small 
area inventories. 
"Role of Aerial Photographs" 
Aerial photographs were mainly used for forest type delinea 
tion, preparation of base maps and inventory maps, area determination 
of forest types and location of ground sample plots in the field. By 
restricting the inventory field, work in forested areas alone saved the 
cost and time by about 30% o Location of ground sample plots was 
found to be easier and much more reliable than conventional topographic 
line maps. The experience was varied in different types of forests on 
different scales. On smaller scales and in dense forests with poor 
identifiable features the plot centres were located by bearings and 
distance measurement for short traverses. In most of the cases the 
plot centre could be located by the image of the surroundings. Worst 
cases were in tropical wet Evergreen forests where plot location was 
mainly done by traversing. 
"Sampling Designs" 
In the initial stages, three different types of sampling designs 
were used in three different regions, in the Southern zone consisting of 
tropical wet evergreen forests, systematic strip plot sampling was used. 
In the central zone consisting of tropical moist and dry deciduous forests, 
a systematic cluster sampling with two plots in each cluster was used. 
In the Northern coniferous forest zone simple random point sampling was 
adopted. The usual method has been to systematically lay out sample 
plots on grid intersections (Latitude and Longitude) which provided the 
centre of the first plot of cluster. The intensity of the grids varied 
in different regions from 5'x5‘ to 1 1' x 11' depending on the varia- 
4 
bility and precision fixed. In general a precision of _+ 10% was 
prescribed'. 
Investigations into the optimum sampling design for different 
forest types were undertaken as exercises at IPI. Designs based on 
simple random sampling, line plot sampling, stratified random sampling 
with fixed plot size and variable plot sampling were tried. In the coni 
ferous forest zone of the Himalayas, stratification in volume classes was 
done and volume per unit area measured by variable plot sampling. 
Due to topographic consideration this method was found useful. In 
tropical forest areas line plot and stratified plot sampling were tried 
and in areas where stratification into different forest types or volume 
classes could be done this gave useful results, with fixed plot size. 
TIWARI ( 9 ) conducted investigations into fixed plot and variable plot 
sampling in Sal forests of Dehra Dun and no significant differences 
were found for basal area and volume estimates but tree count estimates 
were poor with variable plot sampling. However, in the majority of the 
tropical deciduous type of forest where forests are irregular and trees