Jungle Fever - measuring chlorophyll in the rainforests of Borneo

A chlorophyll meter courtesy of APPF found its way to Sabah in Malaysian Borneo where Hannah Carle, a PhD student at ANU, used it to measure chlorophyll content - among a suite of plant traits she is using in an attempt to predict the long-term survival and growth of trees used to restore forest restoration landscapes following selective logging.

Hannah's field site is in the heart of Malua Forest – an aseasonal rainforest selectively logged in 20 to 30-year cycles. The target species for logging are typically Dipterocarpaceae (common name: dipterocarps), a hyperdiverse group of predominantly Southeast Asian canopy-forming trees known for their impressive supra-annual en masse flowering events, called masting.

Working with a team including Research Assistant Mohammad Fauzi (SEARRP) and two undergraduate volunteers from the Universiti Malaysia Sabah, the chlorophyll meter allowed Hannah to measure chlorophyll concentrations in situ for about 600 dipterocarp trees.

They worked on six-year-old saplings planted into experimental plots comparing the effects of different neighbourhood diversities and exposure to periodic drought on survival and growth.

"We took measurements on each of four fully expanded upper canopy leaves per tree – an interesting challenge when some of the saplings are more than 3 metres tall," according to Hannah.

In spite of difficult terrain and often challenging access to the canopy of these trees, having the device allowed Hannah and her team to take large numbers of measurements.

Chlorophyll concentration indicates photosynthetic capacity and reflects the nutrient status of the plant. Because both light and nutrients can be limiting in tropical forests, leaf chlorophyll concentrations might be expected to affect the survival and growth of rainforest trees.

Hannah also used the OptiSciences CCM300 device to make chlorophyll concentration ‘maps’ for each of the six dipterocarp species in the experiment.

Preliminary analysis of the data suggests that chlorophyll varies significantly between species and on average, is significantly higher (nearly double) in lowland forest plots; where soils are better developed as compared to the sandy riparian and well-drained ridge plots. Some species also appear to exhibit differences in chlorophyll concentration according to the environment – riparian or up-slope – of their maternal line.

Pictured is Hannah with her research team: Research Assistant Mohammad Fauzi in the middle, left is Ezron Gerald and right is Mick Fraydones (both undergraduate students at the Universiti Malaysia Sabah).

Research access was granted by Danum Valley Management Committee, Sabah Biodiversity Council and Sabah Forestry Department. Funding courtesy of AGRTP (Australian Government Research Training Partnership), ANU Research School of Biology and the Ecological Society of Australia (Student Research Award).

27 July 2020