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Arnold Arboretum

Climbing trees

May 25, 2011 by Cam Webb

‘WX,’ one of our climbers, in action with a pruning pole

Amazingly, the timing of our expedition has gone almost exactly to plan. Before we started, I could only estimate that setting up, morphotyping, and collecting from six 0.25-hectare plots might take two months. Until I finished the final image matching a week and a half ago, we didn’t know how many trees we would need to collect. But in the final week, the climbing team did a truly fantastic job collecting from the remainder of the 323 trees we eventually sampled. Except for a handful of species, we managed to locate a tree for each taxon that the climbers could climb. The fundamental problem with doing botanical collecting in Bornean rainforest is that the trees are so darn tall! The tallest measured rain forest tree, at 88 meters, is a Shorea faguetiana (Dipterocarpaceae), also on Borneo in the Tawau Hills Park, Sabah. Collecting means reaching the forest canopy somehow. Various methods have been attempted including shooting down twigs with a rifle (you must be an excellent marksman!), and accessing the canopy from above by balloon. The famous botanist E.J.H. Corner, author of the unmatched ‘Wayside Trees of Malaya,’ used trained pig-tailed macaques to collect. We have experimented with various alternative collection techniques. Shooting a fishing line over a branch with a catapult, pulling up a section of chainsaw chain and sawing the branch is promising, but the chain always gets pinched as the branch sags. Our best alternative to climbing is to shoot a fishing line and pull up a heavy rope to form a slip-knot around the branch, and then simply pull hard on the rope until the branch is snapped off. But this is time-consuming.

If good climbers are available, there is no better method than to have someone climb and hand-select the right samples. Edy and WX are superb, safe climbers, and have been working with me for over two years now. They have slightly different climbing styles: Edy leans back on his outstretched arms, with his feet walking up the trunk. WX holds his chest close to the trunk, with legs locked in a squatting position. When sampling from the taller trees, and when using the pole pruner to reach twigs from neighboring trees, we ask them to use a climbing harness and webbing as a belay; accidents seem more likely when they are focusing on activities other than holding onto the tree. Safety is obviously my main concern, but I trust their judgment concerning slippery trunks, being tired, and other matters.

Not all twigs are easy to press in newspaper! Collections of Artocarpus anisophyllus (Moraceae) made by Edy and Manto

Our current method is for them to cut two, 2-3 cm diameter branches. They usually do this with a parang (the indispensable, long forest knife that everyone carries in the forest). They then carefully climb down and process the specimens: i) a small section of young leaf for DNA, placed in a tea-bag in silica gel, ii) two 10-cm-long sections of branch wood (for wood density analysis), iii) two twigs with a minimum of five leaves each, for measurement of leaf area and specific leaf area, and iv) a set of two twigs for a nice botanical voucher specimen. In the few cases where we have been unable to reach the tree’s canopy, we have collected a DNA sample from the cork cambium, using a tool I found in Bogor for punching holes in leather (locally-sourced supplies are much more sustainable!). However, in these cases, we are left with only fallen leaves for our vouchers, which may make positive identification more difficult. A major part of the success of this trip has been the dedication of our climbers (Manto and Kasah, as well as Edy and WX). According to them, there are many capable climbers in this area because of coconut harvesting, honey collection, and the ‘cleaning’ of durian trunks to encourage fruiting. I’m concerned about whether we will be as lucky finding good climbers on the other islands we will visit.


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