An example of the problems that heavy branching on Blue Mahoe (Hibiscus elatus) trees can cause when felling selectively in areas densely populated with Mahoe. An example from a recent experimental harvest involved a 60 feet tall Mahoe on a slope with a dbh (diameter at breast height)of 45cm (17inches), and a commercial height of 20 feet, where the tree branched heavily. The tree had a slight incline down slope.
The tree was felled down slope after discussion of the pros and cons of all the possible felling directions. The down slope decision arose as a result of safety issues and considering the damage that might occur at all other angles. The aim, of course, was to minimize damage to the surrounding trees as the target tree fell.
The tree was cut about 14inches from ground level, but the tree did not fall. Instead it slid off the stump and lodged itself in the ground. A large forked branch of the tree lodged in another tree 20 feet further down the slope, but not directly below. We had selected that tree to remain uncut.
Our qualified arborist, talked us through his method of evaluating the next step in such a situation. The felled, but unfallen tree was an unstable situation, rendering the entire area dangerous, and it was out of the question to now climb and debranch.
We attached rope and a pulley and tried to dislodge, from a distance, the trunk whose cut base was settled firmly in the ground near the stump.
Several attempts from different directions failed to make any difference. We hoped that branches would crack with the weight of the trunk moving or might dislodge with the weight of the tree falling.
We then chainsawed a 4ft piece from the bottom of the main trunk in the hope that shortening the lodged trunk would help the stuck branch slip away from the other tree. The shortened trunk simply dropped into the soil below, exactly as it had done on the first cut. Another four foot piece was cut and the target tree remained as firmly lodged in the other tree as before. This kind of work is very dangerous given the slope.
At this stage it became clear that the second tree would have to be felled.
If, in the first instance the tree had been climbed and de-branched, this situation would not have arisen. It was not apparent that this tree would need so much attention, but just one strong branch catching another tree meant the difference of the second tree necessarily being felled and then a third tree to bring them down, because the second tree was firmly lodged in an A shape with the first target tree. It took half a day to bring the target tree down and in the process two more trees had to be felled that were not selected for harvest.
3t’s Notes from the field. Tropic Ventures Sustainable Forestry, Patillas, Puerto Rico.
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Contributor's Note
3t Vakil and Andres Rua, are the 'we' referred to in the article. Both are volunteer directors at Tropic Ventures, involved in sustainable forestry where they are learning by doing.
Tropic Ventures Rainforest Enrichment and Sustainable Forestry Project is registered under the Auxiliary Forest Program of Puerto Rico, and is a demonstration project for students and foresters interested in the intelligent, sustainable management and preservation of tropical rainforest land.
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