How will elevated CO₂ affect the timing, duration and quality of nectar production in E. tereticornis, and what will be the consequences for nectarivores

Project leader, researchers and collaborators: Assoc Prof Ben Moore (Lead), Co-investigator Assoc Prof Ricky Spencer

Funding period: 3 years

Funding agency: Some acoustic monitors is funded by UWS sustainability fund

Project summary: Most studies of nectar production have shown a rapid increase in nectar production (50% increases are common) under elevated CO₂. This can result from greater rates of nectar production, longer duration of flowering and production of nectar and changes to the concentration of nectar. Nectar quality may also change in terms of the composition of sugars and free amino acids.

Previous studies of eucalypt flowers have shown the concentration of sugars in nectar to be highly variable between years. Although less studied, the quantity and quality of pollen produced may also change.

I propose to study the productivity of floral resources using both phenological observations and floral/nectar bagging and sampling.

Nectarivores in the Cumberland Plain Woodland are numerous. By their nature (they rely on a emphermeral, energy-rich food source), most nectarivores are highly mobile and often migratory or nomadic. E. tereticornis is a prolific winter flowerer and is visited by many vertebrates and invertebrates. Birds include lorikeets and the endangered swift parrot (related to the seed-eating rosellas but inhabiting the nectarivous niche of the lorikeets) and honeyeaters including the endangered Regents honeyeater. Mammals include marsupials (sugar glider, squirrel glider and yellow-bellied glider) and eutherians (the threatened grey-headed flying fox). E. tereticornis is also an important floral resource for native and introduced insects, and probably indirectly for the microchiropteran bats that feed on them. It is an important source of nectar and pollen for honeybees (honey is an $80m industry in Australia). 

 Most nectarivores are very noisy when feeding, reflecting their energy-rich diet, and their presence can be monitored acoustically. I propose to monitor the use of E. tereticornis flowers by these nactarivores in control and CO₂ fumigation rings using acoustic monitoring to test whether changes in floral productivity are significant enough to alter nectarivore foraging and whether use of the floral resource increases or decreases under elevated CO₂.

I propose to study the productivity of floral resources using both phenological observations and floral/nectar bagging and sampling. Bagging of flowers is required to prevent the removal of nectar by nectarivores for a fixed period (probably 12 or 24 hrs) prior to sampling of nectar with a pipette. E. tereticornis usually flowers in winter and monitoring will commence in Winter 2012, prior to the commencement of fumigation and continue annually for at least three years.

I propose to monitor flowers of five fumigated trees and five control trees, matched for size. Access to the canopy by crane will be required. Use of floral resources within the FACE rings will be monitored acoustically. At least 4 microphones will be positioned around each FACE ring and these will record to digital recorders on four separate channels, either to a single recorder or to separate recorders will synchronised digital clocks. Synchronisation is essential to enable precise location of the origin of sounds (inside or outside the rings) by triangulation based around the differential arrival of signals at each microphone. The detection and identification of bird and bat calls will be automated as far as possible with commercially available software such as SoundScope (wildlife acoustics Pty Ltd). Paired control and fumigation rings will be monitored simultaneously. The proposed sound recorders can also monitor insectivorous bats.