Lowland Rainforest in NSW North Coast and Sydney Basin Bioregion - endangered ecological community listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list Lowland Rainforest in the NSW North Coast and Sydney Basin Bioregions as an ENDANGERED ECOLOGICAL COMMUNITY in Part 3 of Schedule 1 of the Act. Listing of endangered ecological communities is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Lowland Rainforest in the NSW North Coast and Sydney Basin Bioregions is the name given to the ecological community of subtropical rainforest and some related, structurally complex forms of dry rainforest, excluding Littoral Rainforest (as described in the Final Determination gazetted on 4/6/04) and Lowland Rainforest on Floodplain in the NSW North Coast Bioregion (as described in the Final Determination gazetted on 13/8/99). Lowland Rainforest may be associated with a range of high-nutrient geological substrates, notably basalts and fine-grained sedimentary rocks, on coastal plains and plateaux, footslopes and foothills. In the north of its range, Lowland Rainforest is found up to 600m above sea level, but in the Sydney Basin bioregion it is limited to elevations below 350 m.

2. Lowland Rainforest, in a relatively undisturbed state, has a closed canopy, characterised by a high diversity of trees whose leaves may be mesophyllous and encompass a wide variety of shapes and sizes. Typically, the trees form three major strata: emergents, canopy and sub-canopy which, combined with variations in crown shapes and sizes, give the canopy an irregular appearance (Floyd 1990). The trees are taxonomically diverse at the genus and family levels, and some may have buttressed roots. A range of plant growth forms are present in Lowland Rainforest, including palms, vines and vascular epiphytes. Scattered eucalypt emergents (e.g. Eucalyptus grandis, E. saligna) may occasionally be present. In disturbed stands of this community the canopy continuity may be broken, or the canopy may be smothered by exotic vines. Although every stand of rainforest is unique in terms of its biota, Lowland Rainforest can be characterised by the following species.

A number of these species, including Acacia irrorata, A. melanoxylon, Adiantum formosum, Breynia oblongifolia and  Ceratopetalum apetalum, are locally abundant in some stands of the Lowland Rainforest, but may be more common overall in other communities.

3. The total species list of the community is considerably larger than that given above, with many species present only at one or two sites or in low abundance. The species composition of a site will be influenced by its physical environment (including geology and drainage), size of the site, recent rainfall or drought conditions and by its disturbance (including fire, windthrow and treefall) history. The species composition of individual stands is often unique, but the structure, physiognomy and species present permit recognition of stands as Lowland Rainforest. In addition to vascular plants the community also includes micro-organisms, fungi, cryptogamic plants, and a diverse fauna, both vertebrate and invertebrate. An indication of the richness and diversity of the invertebrate fauna is provided by Williams (1993, 2002).

4. Lowland Rainforest belongs to the Subtropical Rainforests class of Keith (2004), although some stands may be interpreted as structurally complex assemblages within the Dry Rainforests class.

Lowland Rainforest encompasses stands which fall principally within the following alliances and suballiances of Floyd (1990b):

Argyrodendron trifoliolatum alliance

1. Argyrodendron trifoliolatum suballiance

5. Castanospermum australe - Dysoxylum  muelleri suballiance

6. Archontophoenix - Livistona suballiance

Dendrocnide excelsa - Ficus spp. Alliance

14. Doryphora sassafras - Daphnandra micranthus - Dendrocnide excelsa Ficus-spp. -  Toona suballiance

15. Ficus spp. -  Dysoxylum fraserianum - Toona - Dendrocnide suballiance

Drypetes australasica - Araucaria cunninghamii alliance

21. Araucaria cunninghamii suballiance

22. Flindersia spp. -  Araucaria suballiance

(Nomenclature and numbering follows that in Floyd 1990a, Table 2 - a number of nomenclatural changes have occurred subsequently. Floyd (1990b) describes the characteristics and example stands of these suballiances in some detail.)

The inferred ecological relationships between different suballiances of rainforest have been interpreted by Floyd (1990b, see Appendix 2). While these suballiances differ floristically and in structure, individual stands of Lowland Rainforest may contain elements of more than one suballiance and the boundaries between different suballiances may intergrade. Nevertheless there are structural, habitat and floristic features which, in combination, link all the Lowland Rainforest suballiances, including the presence of emergent trees, variety of leaf and canopy shapes and sizes, the abundance and diversity of vines and vascular epiphytes, the association with nutrient-rich lithic substrates, etc. (see paragraph 2).

5. In addition to the principal suballiances listed above, Lowland Rainforest encompasses stands that display characteristics of some other suballiances. These stands occur in environments that are around the transitional limits of Lowland Rainforest with increasing altitude or maritime influence, or declining moisture status or soil nutrient status (Floyd 1990b).

With increasing altitude in far northeastern NSW, the Argyrodendron trifoliolatum alliance is replaced by the  Argyrodendron actinophyllum alliance (sometimes referred to as a cool subtropical rainforest). This alliance is well represented in the reserves included within the CERRA World Heritage listing. These stands are of great conservation significance but are not considered part of the Lowland Rainforest community. However, where the following suballiances occur towards their lower altitudinal limit, in conjunction with stands of any suballiance listed in paragraph 4, they are part of Lowland Rainforest.

7. Argyrodendron actinophyllum

8. Argyrodendron actinophyllum - Araucaria cunninghamii

9. Argyrodendron actinophyllum - Dysoxylum  muelleri - Syzygium francisii

10. Argyrodendron actinophyllum - Dendrocnide excelsa - Ficus

Lowland Rainforest, when optimally developed, has the structural and floristic form of subtropical rainforest (sensu Floyd 1990a, b), but may be interspersed with stands of dry rainforest as moisture status declines or topographic exposure increases. Stands of suballiances

23. Ficus- Streblus- Dendrocnide- Cassine

27. Choricarpia leptopetala

28. Backhousia sciadophora - Dendrocnide- Drypetes

29. Backhousia myrtifolia - Lophostemon confertus - Tristaniopsis

30. Backhousia myrtifolia - Acmena smithii

are part of Lowland Rainforest where they occur in transitional zones with any suballiance listed in paragraph 4.

As soil nutrient status declines, Lowland Rainforest may be replaced by warm temperate forms of rainforest. Lowland Rainforest typically occurs on relatively nutrient-rich, such as basic volcanic or fine-grained sedimentary substrates, but may also occur on substrates of intermediate fertility, including acid volcanics (Floyd 1990b). Warm temperate rainforests are extensive on granites in the Washpool district and commonly occur at elevated sites on acid volcanic substrates (e.g. on the Nightcap Range) and at lowland sites on sandstones, shales and mudstones in localised gullies southward from the Sydney Basin. These stands of warm temperate rainforest are generally excluded from Lowland Rainforest. However, the following suballiances (sensu Floyd 1990b) within the  Ceratopetalum apetalum alliance may occur on soils of intermediate fertility throughout the NSW North Coast and Sydney Basin bioregions, and are included within Lowland Rainforest where they occur in conjunction with stands of any suballiance listed in paragraph 4:

33. Ceratopetalum apetalum -  Schizomeria - Argyrodendron spp -  Sloanea suballiance

34. Ceratopetalum - Diploglottis australis - Acmena smithii suballiance

35. Ceratopetalum - Schizomeria - Caldcluvia suballiance

Where lithic substrates adjoin floodplain alluvium, Lowland Rainforest may occur in conjunction with Lowland Rainforest on Floodplain of the NSW North Coast Bioregion, listed as an Endangered Ecological Community under the Threatened Species Conservation Act 1995. Similarly, Littoral Rainforest in the NSW North Coast, Sydney Basin and South East Corner Bioregions, listed as an Endangered Ecological Community under the Threatened Species Conservation  Act , may replace Lowland Rainforest with increasing maritime influence. In both cases, the Determinations of these respective communities collectively encompass all transitional stands of rainforest.

6. There are strong latitudinal trends in the composition of Lowland Rainforest, with species diversity and structural complexity declining from north to south. The Hawkesbury River notionally marks the southern limit of Lowland Rainforest in the NSW North Coast and Sydney Basin bioregions. South of the Sydney metropolitan area, Lowland Rainforest is replaced by Illawarra Subtropical Rainforest of the Sydney Basin Bioregion, which is listed as an Endangered Ecological Community under the Threatened Species Conservation Act. Milton Ulladulla Subtropical Rainforest is a related rainforest endangered ecological community that occurs still further south in the South East Corner Bioregion.

7. Threatened species found in Lowland Rainforest include

The list provides an indication of the diversity of the ecological community, and an indication of species whose requirements will need to be considered in preparing conservation management plans. The number of threatened species listed above are restricted to the northern parts of the ecological community (paragraph 6). Presence of species in the list is not essential for characterising a stand as being a representative of the Lowland Rainforest ecological community.

8. Since European settlement Lowland Rainforest has undergone a large reduction in geographic distribution (particularly its area of occupancy) due to clearing (Floyd 1990a, b). For example, Floyd (1990a) estimated the Big Scrub lowland rainforest near Lismore, originally estimated to cover 75 000 ha, had been reduced to only 300 ha (0.07%) since European settlement. Other districts as far south as Ourimbah have suffered similar losses of Lowland Rainforest. Relative to the longevity of rainforest trees, many of which live for several hundred years, these represent large reductions in the geographic distribution of the community. 'Clearing of native vegetation' is listed as a Key Threatening Process under the Threatened Species Conservation Act.

9. Extensive clearing of Lowland Rainforest has resulted in fragmentation and loss of ecological connectivity. The integrity and survival of small, isolated stands is impaired by the small population size of many species, enhanced risks from environmental stochasticity, disruption to pollination and dispersal of fruits or seeds, and likely reductions in the genetic diversity of isolated populations (Lott 1990, Rossetto et al. 2004a, b). Disruption of these ecological processes may result in a large reduction in the ecological function of the community.

10. Weed invasion also poses a major threat to Lowland Rainforest, with introduced vines and scramblers having particularly serious impacts (Floyd 1990a). Principal weed species include:

Many of these exotic species form dense thickets capable of smothering indigenous plants, reducing both reproduction and survival (Floyd 1990a, Harden et al. 2004). The invasion and establishment of exotic species in Lowland Rainforest results in a large reduction in the ecological function of the community. 'Invasion and establishment of exotic vines and scramblers' is listed as a Key Threatening Process under the Threatened Species Conservation Act.

11. Although the interior of large stands of Lowland Rainforest are rarely flammable, inappropriate fire regimes associated with burning off and hazard reduction pose a threat to the margins of rainforest stands and the entirety of small stands in fragmented landscapes. Repeated burning is likely to change community structure and/or species composition of stands of Lowland Rainforest, as many of its species are poorly equipped with post-fire recovery mechanisms. 'High frequency fire resulting in disruption of life cycle processes in plants and animals and loss of vegetation structure and composition' is listed as a Key Threatening Process under the Threatened Species Conservation Act.

12. Other common threats include grazing by livestock, potential impacts of anthropogenic climate change and impacts associated with human visitation (including soil compaction, possible spread of pathogens, clearing of understorey and inappropriate collection of plant species). In addition, the collection and trade of some rainforest invertebrates may be greater than is generally appreciated. Collectively these processes may result in degradation of Lowland Rainforest habitat, and hence a large reduction in ecological function of the community.

13. Some stands of Lowland Rainforest are included within the conservation estate (including components of the Central Eastern Rainforest Reserves of Australia World Heritage listing). However, not all Lowland Rainforest suballiances occur in conservation reserves and many small stands, important for connectivity and maintenance of landscape-scale ecological processes, remain outside conservation reserves.

14. The Scientific Committee is of the opinion that Lowland Rainforest in the NSW North Coast and Sydney Basin Bioregions is not eligible to be listed as a critically endangered ecological community.

15. Lowland Rainforest in the NSW North Coast and Sydney Basin Bioregions is eligible to be listed as an endangered ecological community as, in the opinion of the Scientific Committee, it is facing a very high risk of extinction in New South Wales in the near future, as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:

Clause 25

The ecological community has undergone, is observed, estimated, inferred or reasonably suspected to have undergone, or is likely to undergo within a time span appropriate to the life cycle and habitat characteristics of its component species:

(b) a large reduction in geographic distribution.

Clause 27

The ecological community has undergone, is observed, estimated, inferred or reasonably suspected to have undergone, or is likely to undergo within a time span appropriate to the life cycle and habitat characteristics of its component species:

(b) a large reduction in ecological function,

as indicated by any of the following:

(f) disruption of ecological processes

(g) invasion and establishment of exotic species

(h) degradation of habitat

(i) fragmentation of habitat

Associate Professor Lesley Hughes
Chairperson
Scientific Committee

Proposed Gazettal date: 22/12/06

Exhibition period: 22/12/06 - 16/03/07

References:

Floyd A (1990a) Australian rainforests in New South Wales. Volume 1. (Surrey Beatty and Sons: Sydney.)

Floyd A (1990b) Australian rainforests in New South Wales. Volume 2. (Surrey Beatty and Sons: Sydney.)

Keith DA (2004) 'Ocean shores to desert dunes: the native vegetation of New South Wales and the ACT.' NSW Department of Environment and Conservation, Sydney.

Harden GJ, Fox MD, Fox BJ (2004) Monitoring and assessment of restoration of a rainforest remnant at Wingham Brush, NSW. Austral Ecology29 , 489-507.

Lott R (1990) Rainforest. Australian Heritage Commission, Canberra.

Rossetto M, Gross CL, Jones R, Hunter J (2004a) The impact of clonality on an endangered tree (Elaeocarpus williamsianus) in fragmented rainforest.  Biological Conservation117 , 33-39.

Rossetto M, Jones R, Hunter J (2004b) Genetic effects of rainforest fragmentation in an early successional tree (Elaeocarpus grandis).  Heredity93 , 610-619.

Williams GA (1993) Hidden rainforests: Subtropical rainforest and their invertebrate biodiversity. (UNSW Press: Sydney)

Williams GA (2002) A taxonomic and biogeographic review of the invertebrates of the Central Eastern Rainforest Reserves of Australia (CERRA) World Heritage Area and adjacent regions. Technical Reports of the Australian Museum 16 .