There are several plantations at Rocky Creek Dam. The site is in public ownership (Rous County Council) around a water catchment. It was previously dairy farm and originally subtropical rainforest. The plantations in the area have been established for several reasons: amenity, revegetation, stabilisation and commercial timber. The plantations at the Dam have been established and managed by Mr Ralph Woodford, with assistance at various times from Greening Australia, the Dorroughby Field Studies Centre and the Subtropical Farm Forestry Association. Mr Woodford has actively pruned and thinned the plantations throughout their lives.
The growth of the trees at several of the sites has been monitored by staff and students at Southern Cross University. One of the oldest of the plantations at Rocky Creek Dam was part of a comparative study of the growth of cabinet species funded by the Rural Industries Research and Development Corporation (Specht 1999)(1). The data were collected using the Subtropical - Tree - Site - Management (STSM) database, a PC-based tree performance database which takes into account site characteristics, provenance and management. STSM is based on, and compatible with, Treedat of Forest Services, Queensland Department of Primary Industries, and MPT-DAT of the CSIRO Division of Forest Products in Canberra. Part of the output from this database is the map which you have been provided with today, allowing accurate location of individual trees for re-measurement.
The growth rates obtained at four and five years of age in this planting allow a comparison between the species (Fig. 1).
 

The comparison between the performance of species at various sites in the region (north-east New South Wales and south-east Queensland) that suggests several factors about the sites are important to species performance. This is illustrated by the strong relationship between height growth and rainfall during the growing period for Elaeocarpus grandis (blue fig). The growth of other species, such as Gmelina leichhardtii (white beech), although also strongly dependent on rainfall is also strongly correlated with pH among other factors (Fig. 2).

Measurements were recently made by Southern Cross University forestry students in their Forest Mensuration class of a sample of the oldest section of the most recent plantation in the area (plantation 4). This plantation is immediately to the right of the main entry, straddles a shallow valley. The site measured was stratified into two according to slope: (i) the slope down into the valley and (ii) the plantings within the valley. The preliminary results for this confirm the stratification adopted, with significant differences between the performance of the trees, as indicated by height and dbh, according to the section (p<0.0001). The performance of the different species was also significantly different, but the interaction of species and location showed the growth of some species was highly favoured by being in the gully, while others not (Fig. 3).

Staff at SCU are currently participating in a project funded by the Australian Greenhouse Office to assess the equations and methodologies in the Greenhouse Challenge Workbook. The task also includes the development of equations and biomass figures for less traditional species in farm plantings. Rous County Council is an Ally in this project and the plantations at Rocky Creek Dam have become one of the first used for such measurements. Grevillea robusta is one of the target species for complete biomass assessment and the initial results for this species show the majority of the biomass is found (as expected) in the stem (Fig. 4).

The plantations at Rocky Creek Dam provide a considerable resource for research and teaching. They have enabled students to obtain the necessary skills for species assessment and identification, and have also facilitated research into the effects of site and management factors. The adjacent regeneration areas and natural forests, both eucalypt and rainforest, have provided a very useful comparison and a learning experience in their own right.

author: Alison Specht
with assistance from Byron Yeo and Jerry Vanclay.

(1) Specht A. (1999) High Value Trees on Farms. RIRDC Research Report.