Fires and hydrology of north eastern mixed-species forests

Fires and hydrology of north eastern mixed-species forests

In 2009 the fires in Victoria mainly burnt in mixed-species foothill forests. This forest type makes up much of the watersheds for catchments for Victoria and New South Wales and can be quite diverse, containing up to 10 species of Eucalyptus per hectare. Other forest types, such as open jarrah forest in south western Australia, are dominated by only one or two species.

It is well known that water yield from catchment areas is coupled with water use by trees. Older more established trees have a relatively lower water requirement than young, regenerating trees growing after a disturbance such as wildfire. As an example, a 5% change in water use of the vegetation (e.g. age-related, seasonal variation) is equivalent to 20% reduction in the return of water to stream flow.

There is no doubt that the fires in 2009 in mixed-species forest will cause a change in hydrological cycles and therefore water yield. The question is how big will that change be?

Research aims

We aim to develop our existing methods of quantifying overstorey water-use so they can be applied to resprouting mixed-species forests.

We will characterise the physiology of resprouting eucalypts for a range of species, soils and topographies and climates.

With this information we will refine existing model (SPA) to predict future tree water-use in regenerating mixed species forests at a landscape level.

Background research

Vegetation water-use in Ash-type forests (i.e. Eucalyptus regnans, E. delegatensis) has been studied extensively. Mixed-species forests differ from Ash-type forests in that they regenerate via sprouting shoots rather than seed.

Juvenile leaves on epicormic sprouts are physiologically and phenologically different to mature leaves. Little is known about the water-use of resprouting eucalypts and how this varies among species, topography, age.

Research sites

Four pairs of sites in north eastern Victoria have been selected according to age since fire (2006/07 and 2009) and elevation (300 and 900 m above sea level).

All sites have the dominant eucalypt species present (E. dives, E. radiata, E. mannifera, E. globulus) and are readily accessible for canopy-level measurements.

This project aims to:

  1. Further develop our existing methods of quantifying overstorey water-use so they can be applied to resprouting mixed-species forests
  2. Characterise the physiology of resprouting eucalypts for a range of species, soils and topo-climates
  3. Refine existing model (SPA) to predict future tree water-use in regenerating mixed species forests at a landscape level

Related news

Research has helped measure erosion following bushfires
What has been learned about how fire affects water supply, carbon emissions and smoke?
Quantifying the impact of fire on tree water use
Do mixed species eucalyptus forests use more water as they recover from fire?
The panel sessions were a popular addition to the forum program
More than 75 researchers, end users, PhD students, land managers and industry representatives attended the seventh Bushfire CRC Research Advisory Forum on 23-24 October, held at the NSW Rural Fire Service headquarters in Sydney.
Fire in the landscape - Tarryn Turnbull
A group of fire managers and scientists this month went deep into the forests of north east Victoria to view research sites.
The Bushfire CRC is leading a Fire in the Landscape field excursion as part of its professional development event series, on Tuesday 27 March 2012.

External References

Jessica Heath is conducting a PhD study with the Bushfire CRC at the University of Sydney on the impacts of wildfire on the water supply catchments of the Sydney Basin.

See video