Dead trees tell tales. In the past six months, tree-ring researchers at Kerala Agricultural University (KAU) have hauled teak discs from Thrissur forests to the College of Forestry's wood science laboratory for a dendroclimatological study on teak, claimed to be the first ever in the State.
Dendrochronologists (scientists who study tree rings) at KAU are piecing together facts stored in teak about past climates.
“Tree rings record history. They tell us about climate changes or cultural influences during a particular period in a particular region. Dendrochronologists are time-travellers. Studying tree rings, they tell you about fires, frosts and floods of the past,” said E.V. Anoop, Associate Professor and Head of Department of Wood Science, who leads the study.
He and his team have identified 10 study sites and collected about 100 samples from 75-year-old plantations. “In the next phase, we will collect samples from all forest divisions that will afford a complete picture of past climatic conditions in the State, including monsoon variations. The KAU plans to submit a proposal to the Ministry of Environment and Forests seeking funds for the study,” he added.
A tree adds a new layer of wood to its trunk every growth season. The number of growth rings in a tree reveals its age. Each ring has a wide, light part and a narrow, dark part.
Wide rings indicate favourable conditions for growth — water, sunshine and plenty of nutrients. Narrow rings denote less favourable
conditions such as drought, insect attacks, coldness, disease and lack of nutrients.
Why did dendrochronologists at the KAU choose to study rings of teak trees?
“Teak being ring-porous (early wood-late wood differences being very large) and long-lived, it is sought-after in tree-ring studies. The only other species in our region that is ring porous and ideal for such studies is Toona ciliata (called ‘Chandanavempu' in Malayalam), but it is found scattered in natural forests,” Dr. Anoop said.
Dendrochronologists date the samples and measure the ring width using an increment measuring machine. They fathom the vessel area of early wood and late wood through image analysis. They use Mean Vessel Area (MVA) of the dated tree ring sequences to analyse any relationship between climate and vessel area. To remove non-climatic signals, appropriate filters such as cubic spline, negative exponential or linear regression are used.
The findings of the study will help formulate crop management protocols. “Everything has been favourable to us so far. The study is progressing well,” he said.
