The Tower Hill Experience

Ranald Anderson

Tower Hill is a State Game Reserve in far south-western Victoria situated on the Princes Highway between Warrnambool and Port Fairy. It occurs on the southern edge of the western Victorian volcanic plains at 38° 19' latitude and 142° 22' longitude and is a large nested maar volcano approximately 3kms by 2kms which erupted about 25,000 years ago. Tower Hill is a wetland reserve of approximately 610 hectares with half of the area being crater banks or islands in the shallow waters.

James Bonwick on visiting Tower Hill in 1857 wrote, "A stroll among the gigantic ferns of the valley, or a ramble among the cones and craters, has peculiar attractions. But these are not comparable to the winding path at the foot of the basaltic rises close to the lake. There the graceful fern tree waves ... almost tropical reeds rustle in the breeze ... leafy shrubs form delightful bowers and alcoves, and tender emotion in suitable company will receive a genial and as rapid a development. The various impediments arising in the walk, such as straggling roots, little inlets, tangled foliage and jutting rocks, will only present occasions for the offer of service, and the acceptance of kind assistance. Let the few who value sentiment in the colony sympathise with nature, who love an undisturbed communion with the grand and sublime, join one and all in the securing for themselves and posterity the authorised declaration that Tower Hill shall be an everlasting reserve."

James Dawson, an early settler wrote in the Camperdown Chronicle in 1891 (just 34 years later), "In the early days of this colony there was to be seen between Port Fairy and Warrnambool, one of the most beautiful and interesting specimens of an extinct volcano in all of Victoria. 'Tower Hill and Lake', then in their primitive state, attracted my attention so much, that fortunately for future generations, I commissioned a celebrated artist to paint the scene in oil on a large scale, and he carried out my wishes faithfully and beautifully. On visiting the scene lately, I was amazed and disgusted to find everything altered, the fine trees on the cones, and in the craters of the islands, all gone excepting half a dozen or so. But what a thousand times worse than this ruthless destruction of ornamental timber, the larger portion of the lake is made into a setting, stinking mud pool full of fermenting malarious matter, sufficient to poison the whole neighbourhood and enough to prevent any sensible person settling near it."

By the late 1850s, destruction of the vegetation within Tower Hill had started. The very dense native vegetation outside Tower Hill has already suffered a similar fate. Structural timber was being imported from Launceston, Tasmania by 1855. Despite this destruction and the alienation of 3/5ths of the banks, the Crown refused to relinquish control of Tower Hill. Initially reserved as a "reserve for public purposes in 1866", Tower Hill had a variety of management committees and names such as 'Tower Hill Acclimatisation Reserve' and 'Tower Hill State Forest'. Eventually, steps were taken to achieve what James Bonwick had suggested in 1858, "that Tower Hill be an everlasting reserve." This was done by an Act of Parliament on 5th December 1892 which declared Tower Hill to be a National Park - Victoria's first and one of the earliest in the world. With no additional funding for its management, Tower Hill National Park was vested in the Borough of Koroit for them to manage.

To ease the burden on ratepayers, the councillors were forced to seek returns from their new area of responsibility by continuing to collect royalties from quarrying of the volcanic road-making material and grazing leases. By the turn of the century, Tower Hill was a shadow of its former glory with bracken being the dominant vegetation and rabbits the dominant wildlife species. Quarry operations, rubbish dumping and grazing continued.

Tracing the Original Flora

Almost one hundred years since destruction commenced, forces benign to Tower Hill began to muster. The Warrnambool Field Naturalists obtained permission from the Borough of Koroit to begin some trial plantings of native Australian species on areas of Tower Hill with a view to large scale revegetation. The value of wetlands was being recognised as well. The rate of disappearance of wetlands prompted measures to preserve some of these important ecological communities. A system of wetland reserves was investigated across Victoria managed by the Fisheries and Wildlife Department. Tower Hill was declared a State Game Reserve within that system in 1961.

Whilst Tower Hill was an important wetland as it stood in 1961, it was realised that its value for wildlife would be greatly enhanced if its native flora was returned. As habitat improved many species of native fauna could be restored to the area. An ambitious program was begun in 1961 by the Fisheries and Wildlife Department with the aim of restoring as closely as practicable Tower Hill's indigenous flora and fauna.

To do this, one had to know what constituted the original flora and fauna. Records were sparse. Fortunately the pictorial record of Tower Hill in 1855 in the form of the original von Guerard oil painting "Tower Hill near Koroit" was located. This gave a good indication of the structure of the vegetation on Tower Hill before its destruction. Given the extent and thoroughness of the clearing in and around Tower Hill, the planners found they had a dearth of remnant vegetation to guide them in their project.

Helen Aston, Assistant Botanist at the National Herbarium and Cliff Beaugelhole carried out a survey of the vegetation of Tower Hill in 1960. There were: - Swamp Gum, Musk Daisy bush, Sweet Bursaria, Tree Everlasting, Kangaroo Apple, Blackwood, Boobialla and Drooping Sheoak. In all, they found a total of fifty-six native species with forty-six introduced species being identified as well.

Local observations in the 1850s gave a list of sixteen species. Aston gave confirmation of the likelihood of these species being present on Tower Hill by comparison with Mt Eccles and the Stony Rises flora. From these investigations she proposed a list of seventeen trees and shrubs "known to have been or very likely to have been constituents of the original flora" as well as many herbs, reeds, sedges, aquatic plants and ferns.

However, a valid point was made by Mr Jim L. Martin about the soils in Tower Hill compared with those at Mt Eccles and the Stony Rises. His point was that the soils at Tower Hill contained much more lime and that the salt spray from the sea just three kilometres south of Tower Hill would influence the flora. Climatic differences between the places were pointed out too. The pH of soils at Tower Hill were found to vary between 8.6 and 5.8. Mr Martin was a local resident with 50 years experience in local flora.

The von Guerard oil painting was seen by some as a means of identifying species growing at Tower Hill in 1855. A. R. Garnett examined the painting in 1960 and identified about one dozen species - some by inference. The most controversial being the grass tree and callitris species. J. H. Willis examined the painting in 1966 and identified ten species, including the Southern Grass tree which he suggested was included "in the nature of artistic licence" as the plant is unknown on any other volcanic tract.

The Callitris species is interesting in that pollen grain analysis of sediments in Tower Hill showed that Cupressaceae was a component of the flora here at times from 18,000 years ago. A couple of Callitris rhomboidea trees grew up behind the office at the Natural History Centre in Tower Hill some years back until an overzealous workman removed them. I have often wondered if they arose from disturbed soil in the making of the path up there or if they were introduced from outside Tower Hill. A member of a local family related to me a story of his forebears prizing the timber of the Tower Hill pine - a special pine, for furniture making. Did Tower Hill have a remnant stand of Callitris from past ages? Callitris rhomboidea are now found in the Grampian Ranges about eighty kilometres north of Tower Hill. Or was he referring to Exocarpus cupressiformis ?

Some Early Problems

A list of flora for Tower Hill was on hand. A decision was made to replicate pre European flora as purely as possible. Therefore only species considered to have been present at Tower Hill were to be planted. The next hurdle was to obtain the required plants. Nurseries were unable to provide shrubs or ground covers so a decision was made to proceed with tall tree species which were available. The concept of provenance was not in force then and this has led to some problems. The local Black Wattle, Acacia mearnsii, was not able to be supplied and was replaced by Acacia decurrens with assurances that the two were almost indistinguishable. They may be in seedling form and are from a great distance if they are not flowering! 25,000 of these were planted until 1974. They have flourished and left copious quantities of seed in the soil. Many are now senescent but many seedlings are germinating as well. They could be controlled by repeated burning, but other considerations such as the effect of fire on other species, and cost, come into play here. They have been the main source of wattle sap and seed for the sugar gliders of Tower Hill. Later plantings of Black Wattle have been of Acacia mearnsii from local seed sources. Planting of these may be done in areas of senescent Acacia decurrens to preclude seedling A.decurrens development.

Eucalyptus viminalis was supplied from stocks selected from East Gippsland which were for timber production with traits such as tall straight trunks. Local E.viminalis around Tower Hill have spreading habits with multiple stems from the butt, although in denser forest situations nearby, the species tends to grow straight and tall. Perhaps the telling point lies in the inability of the Gippsland stock to survive on higher, drier parts of Tower Hill in dry seasons. Many have not set seed either.

Local seed is used as a matter of course now, although not all desirable species are available locally so the nearest specimens of best fit in term of soil, climate and aspect are used. This seems to be succeeding although it is perhaps too early to be sure. The paucity of local remnant vegetation has left little choice in this matter.

Rehabilitation Commences

By 1964, planting at Tower Hill began in earnest. Labour in the guise of school children was co-opted to help with the mammoth task. This has resulted in widespread community ownership and pride in the reserve with many visitors saying, "I planted trees here when I was at school. I wouldn't know where, now that it has changed so much."

Looking across the revegetated slopes of Tower Hill towards coastal sand dunes and the Southern Ocean. Select the thumbnail image or highlighted name for a higher resolution image (25k).

The planting site selections and spacings were decided by on-site discussions, close examination of von Guerard's painting and early photographs, visual examination of soil and perceived needs for firebreaks and tracks. Species planted between 1964 and 1984 were Manna Gum, Swamp Gum, Blackwood, Early Black Wattle (until 1974), Late Black Wattle (1975 onwards), Drooping Sheoak, Silver Banksia, Woolly Teatree and a small number of Sweet Bursaria. In 1976 almost 600 Coastal Teatrees were planted. These have flourished and have been a source of much work for volunteers and staff in attempting to eradicate them!

Planting in most areas was preceded by ripping. It was quickly found that planting in areas covered by bracken was made much easier if the bracken was removed first. Some areas had bracken up to 2.4 metres high so school children were easily lost in it! It tended to clog the ripper and generally clumps up the topsoil if is was not burned first. Ripping was not done in areas where the furrow would visually impact for many years; for example, the tops of the scoria cones or where the terrain was unsuitable for safety reasons. However, some of the areas that were ripped look to me as though they would have to had to blindfold the driver beforehand.

One aspect of planting in riplines, of course, is that the trees grow in a line. Whilst this is readily visible in some instances we must remember that these plantings are really the seed source for natural regeneration of the area and that in the longer term this will disappear as trees regenerate randomly and disguise the riplines. Ripping achieved considerably better plant survival in the first few years and some 100% better growth according to Gavin Cerini, the officer in charge of the project. Rabbits persist on Tower Hill and they complicated the project by making it necessary to provide tree guards for each seedling in areas where infestation was high and/or species were of particular attraction to rabbit palates. This attraction extends to almost all species when herbaceous food is exhausted in dry years. Rabbits still persist and obviously must affect natural regeneration by eating natural seedlings. An ongoing effective pest animal program is needed for any revegetation program no matter what size it is.

Time has shown that the plantings have, in general, been a magnificent success with the landscape changing wonderfully from a bare monotonous cover of bracken, pasture grasses and introduced pine and cypress trees to a richly varied vista of shades of green, grey green and yellow. The landforms have been perhaps softened a little, but the volcanic geomorphology has been preserved.

The habitat has proven so attractive that over 120 or more species of birds have been sighted on Tower Hill contrasting to the 60 species recorded at the start of the project. Many mammals have been released, including sugar gliders, kangaroos, wallabies, ringtail and brushtail possums and koalas.

Lessons Learned

Over 250,000 plants were planted between 1964 and 1984. As time progressed a few lessons became evident. Aspect has a natural effect on tree spacing, particularly on the higher northern and north-eastern slopes where mortality was high in dry times, until sufficient natural thinning was carried out. Track networks need to be carefully planned and planting kept well back. The extent of the canopy spread was not considered in places on Tower Hill making for a constant pruning problem to maintain access along the main tracks. Even the trees along the main road have to be pruned as bigger and bigger coaches visit.

Possible rising water levels were also ignored during some water-edge plantings. Trees planted in July/August sometimes disappeared under water as levels rose until October/November peaks were reached. This problem occurs because Tower Hill is really the exposed local water table and this can continue to rise even after ground conditions have begun to dry as it takes a long time for surface water to percolate down to the lake level.

Around wet areas it was found that Woolly Teatree would only grow in a narrow zone from the high water mark to about 1/2 metre vertically above that where the roots were able to reach saturated soil in their first year - but were not entirely in it. Some areas of Tower Hill carry remnant Woolly Teatree in very damp soils. Seedlings planted in these areas failed. Surviving Swamp Gum also occurred on hilltops. Replanting was done in a narrow zone that merged with the Woolly Teatree plantings. Sheoaks were planted in drier shallow soil areas which generally meant hilltops or north/north east slopes. They have also grown well in some quarry floors and terraces where little soil exists. Between these two extremes, Blackwood, Black Wattle and Manna Gum were planted in equal proportions or up to 50% Manna Gum. The limiting factor was often nursery production. Spacings would have been greater than the 5 metres on the drier slopes. Also, Blackwoods would have been better kept to the lower wetter portions of Tower Hill.

Despite this, and we must bear in mind that this was an experiment with no precedent, the results were excellent. So much so, that many people would visit the Natural History Centre display and look at a copy of the von Guerard painting and a 1991 photograph of Tower Hill, sometimes make the comment that it didn't appear to have changed much in all those years!!

Understorey Investigations

Of course, to the experienced eye, Tower Hill is still a long way from resembling the pre-European floral structure. A glaring element of omission is the understorey. This was due to the inability of the nurseries to supply shrubs in the period of the most intense planting activity - 1964 to 1977.

In 1985, a study was undertaken of the flora present in Tower Hill and remnants in the area around Tower Hill. This gave us maps of the locality of many species of understorey plants. The list of plants probably occurring at Tower Hill was revised also.

A pollen grain analysis of the sediments that have accumulated in the Tower Hill basin since eruption ceased some 25,000 years ago, was also carried out. This gave us a record of the local flora going back approximately 18,000 years, as well as some information on the climate over that period.

In 1988 an understorey revegetation project was begun under a commercial sponsorship using A.T.C.V. labour and supervision. Seventeen species of understorey plants were introduced to suitable areas of Tower Hill by either growing out cuttings or transplanting. Also, about 5000 tall tree species seedlings were planted. Because of the timing of the project and its limited life, many of the cuttings were not given time to harden from the nursery conditions and success rates were generally quite disappointing. However, some plants survived and have been able to be used as a source of seed or cutting material for further plantings.

The most successful were the kangaroo grass plantings. The technique is labour intensive and nowhere near as efficient as direct seeding of kangaroo grass. However, this requires constant monitoring of the seed source and a ready workforce on standby, facilities which have eluded us to date.

Following the lack of success of this program, it was decided to trial understorey revegetation techniques in a scientific study with Deakin University, Warrnambool Campus. The project was funded through a National Estates Grant. Techniques such as direct seeding and cutting/seedling planting in a variety of conditions using a variety of treatments which would be applicable on a broad scale were trialed. Plant survival and vigour were to be trialed under such variables as:

• degree of canopy cover
• species composition of canopy
• site aspect
• type of site preparation prior to planting
• predation by rabbits

1. Transplanting of tube stock using a Hamilton tree planter, soaking the tube prior to planting and watering in, is associated with 97% success rate.
2. Open and north facing slopes with partial canopy are best for survival.
3. Overstorey species generally have little effect on survival.
4. Planting on steep slopes (shaded by facing south or by canopy)with loose friable soil in not wise. This is particularly so if the tube stock is small or prostrate.
5. Summer watering would help reduce plant loss between January and May, the time of greatest mortality.
6. Open south facing sites covered with bracken were generally no worse than other sites.
7. Acacia species were the best for direct seeding. Success in harder sites was similar to more favourable sites.
8. Residual herbicide did not give a clear cut advantage in these experiments,
9. Rabbits affected about 12% of plants in unfenced sites at 14 months.
10. Snail or slug predation of seedlings is of unknown significance. (Suspected though of causing high mortality rates in damp sites).
11. Highest survival rates of seedlings occur in least densities of weed infestation.
12. Best results in terms of lowest mortalities and highest plant growth were achieved in open areas along the edge of south facing canopies within 10 metres of the dripline. Canopy species is not significant.
13. For north facing canopies sowing inside or outside the dripline (5 metres) gives similar survival rates and heights.
14. Scalped seed rows close to Acacia melanoxylon gives rise to widespread suckering in the seed row.

The Friends has sponsored a LEAP project which has recently finished, leaving us with a large number of canopy and understorey plants planted in many areas, a nursery full of cuttings and seedlings waiting to be planted and a collection of seed waiting for the next opportunity to continue the revegetation of Tower Hill. It is to be hoped that the initial aim of the project is not lost and that momentum is kept up in this area, rather than seeing Tower Hill as a tourist destination only, a nice place to come and have a picnic and see some wildlife.

It is up to all of us to ensure that the vision of those who started the project is not lost.

The Society for Growing Australian Plants