TEAK PLANTATIONS IN NILAMBUR - Kerala Forest Research Institute

Different thinning operations are considered separately. In each set of
operations, a distinct shift from better to poorer site quality class over time
can be seen. In the third silvicultural thinning (3S) while the yield from 13
plantations raised during 1935-39 reflected a site quality of II by 1950-54 the
yields from 4 plantations showed a site quality of only IV and during the
period 1960-64, 61% of the area of plantations shifted further to the ‘failure’
class. Only in the final felling category, there is a slight improvement but here
the difference between the year of planting is only 10 years i.e. between 1930-
34 and 1940-44. Plantations raised in the subsequent years will be available for
final felling only after 1995. In the fourth silvicultural thinning (4S), 91% of
the 20 plantations that were planted during the period 1930-34 showed a site
quality class of I. By 1940-44 no plantations belonged to either site quality I
or even II. Plantations raised in the period 1950-54 showed a mean site
quality of IV. Although no definitive conclusions can be made, the general
indication is that there has been a decline in the productivity level in
successive periods as observed in the thinning yields of plantations.
Another exercise was done using the period of working as a criterion for
observing the changes in productivity levels. Table 5.2 shows the percentage
distribution of area of teak plantations in Nilambur Divisions based on year
of working classified in different site qualities based on actual yields. It is
interesting to find that within each thinning operation, the site quality
distribution considered on the basis of actual yield showed a shift from higher
to lower classes in successive periods of operation. For example, while 26%
of the plantations that were taken up for final felling during the period
1970-74 belonged to site quality II and 26% belonged to site qualitv III.
During 1990-94, 57% of the area of plantations finally felled belonged to site
quality IV and 31% came in the ‘failure’ category.
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