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Tanzania is rich in pine forests which have the potential to produce valuable resin.
In recent years Tanzania has embarked on commercial resin tapping at Sao Hill Forest
Plantation. However, current information on resin tapping in the country is scanty and
unreliable. Knowledge of factors that affect resin productivity is important for it is those
factors that can be manipulated to enhance resin yield. The focus of this study was to fill
this knowledge gap by exploring some pine tree stands in terms of capacity to produce
resin, factors that influence productivity, optimum age of commencing resin tapping and
finally the potential revenue gain from tapped trees. Two-stage sampling was used to
obtain estimates of tree characteristics and resin yield by first selecting seven
representative compartments. In the second stage, 21 sample plots of dimensions 12 x 12
m were systematically established, 3 in each compartment. All trees in each plot were
measured for diameter at breast height (dbh). In addition, total height, stem height and
crown size of the smallest, medium and largest trees were measured. All trees in a plot
were tapped for resin. Dilute sulphuric acid (40%) was sprayed to the wounded part of
stem to stimulate and maintain resin flow. Recording of resin weight and re wounding of
trees were done after a minimum period of every ten days in ten sessions from October
2018 to January 2019. Annual resin yield ranged from 0.56 kg/tree to 1.32 kg/tree for
P. elliottii and from 0.47 kg/ tree to 1.98 kg/ tree for P. patula. Dbh and crown diameter
were found to be important predictors of resin at tree level while yield per ha could well
be predicted using stand variables in particular age, volume and basal area per ha.
The recommended minimum dbh for resin tapping is 20 cm while 15 years could be used
as minimum age to commence tapping. TZS 4 589 884 350 can be raised annually
through resin tapping from 2 618 568 mature trees in state owned plantations. Results of
this study will be useful to pine tree stakeholders in realizing income while waiting for the conventional rotation age for timber harvesting. Further research on effect of resin
tapping on tree growth and wood quality can be very useful to tree growers. |
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