Influence of Climatic Conditions on Resin Yield from Chir Pine (Pinus boxburghii Sargent)

The influence of climatic conditions on seasonal variation in resin yields in the case of chir pine has been examined with the help of data collected during the period 1956 to 1958 at 4 different localities covering the altitudinal range 2,300 feet to 4,500 feet. It has been noticed that production of resin is not influenced by humidity, rainfall or changes in the seasonal rate of growth of the species. On the other hand there is a very intimate connection between temperature and resin yields and fluctuation in the latter are easily explained by those in the former. Optimum yields are obtained under the mean daily temperature conditions of about 80°F. and above and a sharp fall in production occurs as the temperature drops down to about 75°F. The value of 78°F. appears to be critical from this view point as a fall below this point causes a sudden downward trend in the resin production graph. In the altitudinal range covered by the four stations from which the data were collected, the season of peak resin yields varies considerably depending upon the extent to which the temperature values are reduced by the monsoon rains in any particular case. The fall in the resin production graph at the close of the tapping season is more gradual as compared to the rise at the beginning of the season. It appears that the resin producing processes inside the tree take some time to respond fully to the wound stimulus.