We use a mobile flux tower (AU-Mel) in conjunction with the OzFlux tower (AU-Cum) to assess how heterogeneous surface characteristics within the critically endangered Cumberland Plain woodland affect the carbon, water and energy fluxes of dry sclerophyll forests. The flux tower is mounted on a custom-built trailer and the mast can be extended to a height of up to 35 m, making it the tallest mobile flux tower in the southern hemisphere.
The mobile flux tower deployed within 300 m from the main flux tower in a Melaleuca dominated stand of the Cumberland Plain woodland.
The canopy of the Cumberland Plain woodland around the main flux tower is dominated by two Eucalyptus species (E. moluccana and E. fibrosa), and is surrounded by a relatively homogeneous patch of Melaleuca decora trees (they usually grow below the eucalypt canopy).
We used a paired-tower approach to examine how species distribution and forest structure (lidar point cloud in the top row) affect carbon and energy cycling in a heterogeneous ecosystem. The left section relates to the eucalypt-dominated stand (stationary flux tower) and the right section relates to the melaleuca-dominated stand (mobile tower). Photographs (bottom row) demonstrate the extensive shrub layer in the eucalypt stand in contrast to the sparse under-canopy vegetation in the melaleuca stand.
Using this paired-tower approach, we found that melaleucas can substantially contribute to the Australian carbon budget, as they had comparable high rates of quantum yield and photosynthesis along with a similar water loss compared to the eucalypt-dominated stand. However, melaleucas were more vulnerable to pronounced heat or drought stress, as they were less efficient in conserving water, especially when VPD exceeded 3kPa.
This study is published in the OzFlux-AsiaFlux Special Issue in Science of the Total Environment (link to paper).