Vulnerability of the carbon and water cycles in primary rainforest and agroforestry ecosystems in Indonesia to Climate Change
Current and future climatic changes are affecting the functioning of tropical rainforest ecosystems in Indonesia by altering the energy balance and fluxes of water and greenhouse gases and consequently the productivity of the ecosystems. There is particular concern that climate change could increase the vulnerability of these ecosystems to drought.
This project aims to
- determine the day-to-day and diurnal variability in surface layer air stable water isotopes (18O and 2H) at a coastal location (Palu) in Central Sulawesi, Indonesia,
- quantify the ecosystem – atmosphere exchange of energy, water and CO2 fluxes over a primary rainforest in relation to environmental drivers and
- use stable water isotopes to determine the origin and recycling of atmospheric water vapour over a primary rainforest.
In this project, we are combining eddy covariance (EC) measurements of sensible heat, water vapour, and CO2 fluxes with novel online measurements of 18O and 2H in water vapor using laser spectroscopy. The Bariri site is the only known EC site in a pristine high-elevation tropical rainforest, which in combination with the strong influence of the Asian monsoon and El-Nino Southern Oscillation (ENSO) in this region makes it a unique and valuable study site.
In Palu, day-to-day variations in surface air isotope values were largely determined by regional meteorology, as demonstrated by large shifts in isotope values coinciding with changes in air parcel back trajectories. Diurnal variations in isotope ratios were largely driven by the local meteorology, with δ18O and δ2H being significantly affected by relative humidity and air temperature, and deuterium excess by wind direction, as a result of the diurnal land-sea breeze at this location.
Eddy covariance measurements in the Bariri rainforest showed a high CO2 uptake (carbon sink). However, the expected increasing frequency of ENSO-caused drought in this region could lead to dramatic changes in carbon and water cycling in these stands. The isotopic composition of water vapour is expected to provide detailed information on the sources of atmospheric water vapour and subsequent mixing, and thus enable us to assess the vulnerability of these stands to climate change.
