Plantations at Myrtleford and Bright were often established on steep land cleared of native forest and there was considerable public concern about soil erosion and the potential deterioration of water quality affecting the water supply of down-stream users of the Ovens River. This prompted the FCV in 1973 to establish the Cropper Creek Hydrology project comprising three 1st order catchments of native forest in the Black Range at Dandongadale. The catchment weirs and gauging equipment were installed by Leon Bren and this forest hydrology project became his life-time occupation. After a three year calibration period of the three eucalypt catchments, one of the catchments was converted to Radiata Pine retaining a 30 m wide undisturbed buffer zone of native forest along the stream channel (Bren et al. 1979). Conversion was found to have little impact on stream water quality and exports of nutrients and suspended solids increased mainly due to higher stream flow following clearing of native forest (Hopmans et al. 1987). A study of nutrient inputs in rainfall and outputs in stream water was conducted prior to clearing as part of a benchmark nutrient budget for small forested catchments (Flinn et al. 1979c). Such data are an important input for determining the sustainability of pine plantations. Subsequent studies at Cropper Creek examined the impacts of thinning and fertiliser on water quality; this again showed short-term changes in water quality (6 to 12 months) and demonstrated the importance of the buffer zone in protecting water quality values (Hopmans and Bren 2007).

The next stage of the project was to determine the effects of harvesting the plantation and the establishment of the next pine rotation on stream flow dynamics, water yield, water quality and nutrient and sediment export. Unfortunately in December 2006 the three catchments were completely burnt by wildfire including the buffer zone of the pine catchment. The plantation was salvage logged and replanted with Radiata Pine in 2007. This major fire disturbance changed the hydrologic behaviour of the catchments for several years and in the logged catchment resulted in significant soil erosion, deterioration in water quality and large sediment losses. The impacts of wildfire and salvage logging declined over three years and water quality returned to pre-fire values over this period both in the plantation and native forest catchments (Smith et al. 2011 and 2012). The Cropper Creek Forest Hydrology project started by FCV in 1973 then continued by the Department of Conservation, Forests and Lands (DCFL) and successor organisations and more recently by Hancock Victorian Plantations in collaboration with the current School of Ecosystem and Forest Sciences at the University of Melbourne. This long-term project has provided a wealth of knowledge on forest hydrology and the effects of plantation management and the impact of wildfire on stream flow, water quality and nutrient and sediment export in comparison with native forest.

References

Bren LJ, Flinn DW, Hopmans P, Leitch CJ (1979) 'The hydrology of small forested catchments in north eastern Victoria: 1. Establishment of the Cropper Creek project.' Forests Commission Victoria, Melbourne. Bulletin No 27, pp. 48.

Flinn DW, Bren LJ, Hopmans P (1979c) Soluble nutrient inputs from rain and outputs in stream water from small forested catchments. Australian Forestry 42, 39-49.

Hopmans P, Bren LJ (2007) Long-term changes in water quality and solute exports in headwater streams of intensively managed radiata pine and natural eucalypt forest catchments in south-eastern Australia. Forest Ecology and Management 253, 244-261.

Hopmans P, Flinn DW, Farrell PW (1987) Nutrient dynamics of forested catchments in south-eastern Australia and changes in water quality and nutrient exports following clearing. Forest Ecology and Management 20, 209-231.

Smith HG, Sheridan GJ, Lane PNJ, Bren LJ (2011) Wildfire and salvage harvesting effects on runoff generation and sediment exports from radiata pine and eucalypt forest catchments, south-eastern Australia. Forest Ecology and Management 261, 570-581.

Smith HG, Hopmans P, Sheridan GJ, Lane PNJ, Noske PJ, Bren LJ (2012) Impacts of wildfire and salvage harvesting on water quality and nutrient exports from radiata pine and eucalypt forest catchments in south-eastern Australia. Forest Ecology and Management 263, 160-169.