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Measuring flying and understory invertebrate abundance and diversity in ambient and enriched CO2 conditions

Project leader, researchers and collaborators: 
Dr Scott Johnson, PhD Sarah Facey, Prof David Ellsworth, Dr Lisa Bromfield, Dr Markus Riegler, Assoc Prof Uffe Nielsen,

Funding period: 

Project summary: The abundance and diversity of invertebrates in the understory of forests is known to be affected by concentrations of atmospheric CO2 (Hamilton et al., 2012).

In particular, evidence Duke Forest Experiment showed that herbivorous insects declined whereas predaceous insects increased in abundance under elevated CO2 conditions (Hamilton et al., 2012).

The reasons for this remain unclear, though increased habitat complexity resulting from increased plant biomass is known to favour some predators but reduce parasitoid efficacy (Langellotto and Denno, 2004; Gols et al., 2005). Likewise, lower nutritional quality of foliage (e.g. higher C:N) in higher CO2 environments generally has deleterious effects on herbivorous insects. Sampling invertebrates from the understory using sticky yellow traps proved successful at the Duke FACE site (Hamilton et al., 2012).

We propose to extend this by sampling flying insects at different heights along the central towers in each ring to coincide with the location of anemometers in one of the rings. In addition to determining any difference between the two CO2 environments, this will provide an insight into the stratification of different flying invertebrate groups in eucalypt forests.

Understory sampling will be achieved with brief vortis sampling (60 seconds) in areas of understory on a monthly basis (Leather, 2005), supplemented with four pitfall traps already assigned to spaces alongside the litter traps.

The aim of the project is to characterise the effects of enhanced and ambient CO2 on invertebrate groups associated with the eucalypt understory and identify patterns of stratification in invertebrates along a vertical transect.