Trees used as gauge for climate shift

Volunteers put plastic bands around 500 trunks to measure their growth
Siau Ming En Straits Times 29 May 12;

EVERY Saturday for the past 18 months, a team of 10 volunteers and researchers has been trekking through the Bukit Kalang forest, armed with plastic strips, springs and crimping tools.

The volunteers - staff from HSBC Bank and researchers from the Smithsonian Tropical Research Institute's Centre for Tropical Forest Science (CTFS) - then proceed to wrap trees with the plastic bands.

Last weekend, they marked a milestone by banding their 500th tree.

This tree-banding exercise is a joint effort by the CTFS and HSBC. The objective: To study tree growth in response to climate changes.

'It turns out that measuring tree growth enables us to also calculate carbon uptake because roughly one-half of the mass of a tree is made up of carbon,' explained Dr Shawn Lum, 49, principal investigator of the research team, who is also a lecturer at the National Institute of Education, a partner of the CTFS.

Dr Lum is also president of the Nature Society Singapore.

The volunteers have been working on a 2ha site - the size of two football fields - and can band 15 to 25 trees in a span of four hours each time.

The plastic strips that go around the girth of the trees come with inserted springs to take in the trees' expansion, which indicates carbon uptake over a six-month period.

Typically, the trees are measured at the 1.3m height, but volunteers have to ensure the point of measurement is not at a malformed or bumpy part of the trunk. Because trees absorb carbon dioxide as they grow, they are able to offset the population's carbon footprint - the amount of carbon dioxide emitted from people's urban lifestyles.

Dr Lum said a longer-term use of these tree-banding results is that it can 'help us determine which species and type of trees can help us efficiently offset our carbon footprint'.

This is not the first time a tree-banding survey has been conducted here.

In 2008, a similar project of 1,000 trees was carried out at the Bukit Timah Nature Reserve.

The team studied Bukit Kalang this time because it needed to compare the carbon uptake by the coastal hill land in Bukit Timah with the low-lying land in Bukit Kalang.

While the Bukit Kalang project is still in its early stages, preliminary findings are similar to those from the Bukit Timah study.

That study had shown that primary forests can store more carbon than secondary forests.

Trees in primary forests are bigger and taller, have a lower propensity to regenerate, and take a longer time to grow.

Tree-banding has been carried out by researchers in some 20 countries under the respective CTFS internationally, said Dr Lum.

There are plans to extend the project to a new area - either to another patch of forest or to study the existing site in greater detail.

'Or we can do both, which is what we currently aim to do,' added Dr Lum.