FEATURE Converting a dairy farm back to a rainforest water catchment The Rocky Creek Dam story By Ralph Woodford Visitors to Rocky Creek Dam he site where I have been working 3 days and certainly marked the beginning of Tper week for the past 17 years, Rocky what has become a more extensive rain- perceive a park-like Creek Dam, is located in cleared rainforest forest regeneration programme supported country in Australia’s northern NSW coastal by Rous Water. landscape with picnic areas hinterland. The property would once have At the same time as we undertook the been covered with lowland subtropical rain- plantings in the picnic area at the entrance, sculpted into a remnant forest such as that occurring in the adjacent I was undertaking some tentative ecological 172 ha Big Scrub Flora Reserve (now part of restoration work in a declining grove of rainforest backdrop, but the Nightcap National Park). Blackwoods (Acacia melanoxylon), itself Initially cleared for grazing, the site was smothered in the exotic shrub Lantana reverse is true. Much of the acquired along with several other farms by (Lantana camara) (Fig. 2). Forty years pre- rainforest backdrop has Rous County Council (now renamed Rous viously,this grove had germinated from soil- Water) as a site for constructing a public stored seed after the soil was heavily been encouraged to water supply dam for Lismore and the sur- disturbed by bulldozing for the dam wall. rounding district. Construction of the dam Already, a lot of the dead trees had been regenerate by carefully was completed in 1952.When I commenced pushed into piles and the general assump- employment as a horticulturist with the tion was that this approach would continue. measured restoration County Council in 1983, the engineer, Mick However, on the basis that there was a good O’Keefe, instigated a proposal to plant sub- diversity of rainforest seedlings coming up interventions undertaken by tropical rainforest trees at the main entrance under the Lantana,I convinced management to the property to create an attractive public at Rous Water that better revegetation a ‘sole practitioner’. picnic area with a rainforest theme. Prior to results would be achieved by removing this this, the entrance site consisted of a toilet suppressing weed in a way that would not block, a few barbecues, the ever-present damage the natural regeneration that was swing and slide and scattered rainforest already occurring. The resulting regenera- trees in a mown Kikuyu (Pennisetum clan- tion could provide a varied and pleasant destinum) lawn. backdrop for a second picnic area and could Rainforest trees were subsequently supplement the site’s existing rainforest planted in circular beds around the exist- vegetation, which was thought to be more ing remnant trees in the expanse of lawn valuable for sustaining water quality than (Fig. 1). It was not until some years later was open pasture. Ralph Woodford (Whian Whian Road, Whian that we fully appreciated the fact that My work proceeded in an orderly pro- Whian, NSW 2480, Australia) has been working as planting rainforest trees under isolated gression over the approximately 1 ha Black- a rainforest restoration practitioner and consul- remnant trees was unnecessary at this site, wood grove: pulling Lantana and cutting tant for 18 years, after previously working in the given that so many species regenerated larger specimens of Small-leaved Privet native plant landscaping industry in Victoria. This naturally over the years from either the soil (Ligustrum sinense) and Camphor Laurel article is based on his experience working on his seed bank or from seed freshly dispersed (Cinnamomum camphora) low to the own property (itself recovering from logging) and under perches by birds and bats. Nonethe- ground and painting the cut stump with his restoration work at Rocky Creek Dam over the less, this planting has provided a useful glyphosate. Germination of weeds was last 17 years. public education and study opportunity occurring, but strong germination of ECOLOGICAL MANAGEMENT & RESTORATION VOL 1 NO 2 AUGUST 2000 83 FEATURE Where was the seed coming from? Seed of some of the initial pioneer species under the blackwoods may have been stored in the soil given the longer soil per- sistence of pioneer species (Whitmore 1991). We assume, however, that much of the more diverse regeneration is likely to have arisen from seed recently dispersed from the nearby rainforest remnant by fauna, because the longer-lived species do not usually form a persistent soil seed bank (Whitmore 1991).Also, seed-dispersing bird species such as the Topknot Pigeon (Lopho- laimus antarcticus), Green Catbird (Ail- uroedus crassirostris), Lewin’s Honeyeater (Meliphaga lewinii), Figbird (Sphecotheres viridis), Regent Bowerbird (Ptilonorhyn- chus chrysocephalus) and Satin Bowerbird (Ptilonorhynchus violaceus) are commonly observed perching in the grove.The impor- tance of trees in facilitating the dispersal of seed by birds into otherwise cleared areas that are close to stands of native vegetation is now well documented (McClanahan 1986; McClanahan & Wolfe 1987, 1993; Robinson et al. 1992; Robinson & Handel 1993). Our awareness of the role of perches in triggering regeneration, however, occurred gradually, along with the subtly expanding results of our regeneration work. Expansion into new areas Released from weed competition, the rain- Figure 1. Top: young plantings at Rocky Creek picnic area, photographed in 1987 (photo: T. forest species in the Blackwood grove put McDonald). Bottom: a nearby bed (similarly planted) 13 years later. Note that the dominant Acacias on rapid growth, soon out-competing and Pencil Cedars (which naturally regenerated on the site within the first 2–3 years after planting) have now overtopped the planted specimens (photo: R. Woodford). further weed regeneration and exponen- tially reducing my workload. This allowed me to take on a corresponding amount of pioneer rainforest species was clearly and desiccation nor completely smothered work in a new area each season. When I evident, including species such as Kangaroo by Lantana mulch.Ten years after this regen- realized that hand-weeding was limiting Apple (Solanum aviculare), Bleeding Heart eration began, I counted 40 native species the area I could manage,I began using herbi- (Omalanthus nutans) and Poison Peach developing in a 0.5-ha section of the Black- cide judiciously. (Trema aspera). The faster-growing species wood grove,of which 15 species were ‘early- In 1989, with management’s support, I of the next successional phase,the ‘early sec- successional’ species (a combination of four started weeding a new 25 ha area beyond ondary’ species, were also germinating, pioneer species and 11 early secondary the Blackwood grove (Fig. 2) that contained including Corkwood (Duboisia myopo- species) and 25 species were ‘late-succes- patches of rainforest regrowth struggling roides),Celery Wood (Polyscias elegans) and sional’ species (10 later secondary and 15 in competition with Lantana, Camphor Pencil Cedar (Polyscias murrayi). The best mature-phase species). (See box on next Laurel and Small-Leaved Privet (Ligustrum regeneration was occurring in the areas that page for definitions of successional terms). sinense). The same approach that was had received the most soil disturbance (i.e. A list of these species is provided in Table 1, adopted in the Blackwood grove worked the bulldozed sites) but which were neither along with information on their successional well in these new areas to rapidly consoli- excessively exposed to high temperatures phase and distribution mode. date the native regeneration and tip the 84 ECOLOGICAL MANAGEMENT & RESTORATION VOL 1 NO 2 AUGUST 2000 FEATURE Figure 2. Left: map of the entire Rocky Creek Dam site, showing the dam wall and location of Blackwood grove, natural regrowth area and the ‘regeneration area’. Right: detail of the ‘regeneration area’, showing the location of the adjacent remnant edge and areas worked in sequence from 1983 to 1999. Terms used to describe successional phases A number of models have been devised to describe and predict subtropical rainforest development on cleared land. Invariably they describe a process where ‘earlier’ successional phase species are replaced over time by ‘later’ successional phase species (Hopkins et al. 1977; Winter et al. 1991; Floyd 1999). All are more or less based on the following categorization of species into successional groups (Hopkins et al. 1977): Earlier successional phase A1 Herbs and soft-wooded shrubs A2 Pioneers B Early secondary species Later successional phase C Late secondary species D Mature phase (‘primary’) species ECOLOGICAL MANAGEMENT & RESTORATION VOL 1 NO 2 AUGUST 2000 85 FEATURE Table 1. Species recorded in 1985 regenerating under the Blackwood grove, Rocky Creek Dam. *Data from McDonald (1996). Scientific name Common name Successional phase* Dispersal mechanism* Acacia melanoxylon Blackwood A Ants; birds Acacia orites Nightcap Wattle A Ants; birds Achronychia pubescens Hairy Achronychia C Flying frugivores Alphitonia excelsa Red Ash B Flying frugivores Anthocarapa nitidula Incense Cedar D Flying frugivores Archontophoenix cunninghamiana Bangalow Palm C Flying frugivores Arytera divaricarta Coogera D Flying frugivores Beilschmedia obtusifolia Blush Walnut D Flying frugivores Cinnamomum oliveri Oliver’s Sassafras D Flying frugivores Cryptocarya obovata Pepperberry D Flying frugivores Cyathea cooperi Straw Treefern C Wind/water Cyathea leichhardtiana Prickly Treefern