Vegetation and flora of a diverse upland remnant of the Western Australian wheatbelt
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- Bu səhifədəki naviqasiya:
- Introduction
- Results Vegetation and habitat.
- Discussion Vegetation and habitat.
- Table 1
| 19 Vegetation and flora of a diverse upland remnant of the Western Australian wheatbelt (Nature Reserve A21064). F J Obbens 1 & L W Sage 2 1 C/o Western Australian Herbarium, Department of Conservation and Land Management Locked Bag 104, Bentley Delivery Centre WA 6983 bushtech@wa1.quik.com.au 2 Swan Coastal District, Department of Conservation and Land Management, 5 Dundebar Road, Wanneroo WA 6065 leighs@calm.wa.gov.au
In the Western Australian wheatbelt, small intact remnants of bushland can contribute significantly to overall biodiversity. Our comprehensive vascular flora survey of Nature Reserve A21064, a reserve of 110 hectares near the town of Arthur River, has highlighted this aspect. Comprehensive surveys of selective wheatbelt reserves provide benchmarks to help us better understand the flora and vegetation in this highly cleared and fragmented agricultural landscape. In the diverse flora of this relatively undisturbed upland remnant ten distinct plant communities encompassing heaths, herbfields, mallee and woodlands can be recognised. The survey identified 323 vascular plant taxa including one rare species, seven priority species and a number of taxa of special interest recorded from 51 families. Weeds accounted for 22 species (6.8% of total flora), however, the extent of invasion is relatively low.
Vegetation and flora survey, upland remnant, biodiversity, wheatbelt woodlands (Manuscript received January 2003; accepted December 2003) Journal of the Royal Society of Western Australia, 87:19–28, 2004 Introduction Nature Reserve A21064 is an upland bush remnant of high conservation value (i.e. “A” class nature reserve) with a diverse flora (see species list in Appendix 1). It is approximately 110 ha in area and is located about 190 km directly south-east of Perth near the town of Arthur River, Western Australia (Fig 1). The district has a dry Mediterranean type climate with very warm, dry summers and cool, wet winters. Average annual rainfall for the reserve is about 470 mm, which is typical of the wetter western (inner) margins of the wheatbelt. The reserve is situated at the end of an eroded and generally flattened ridgeline and its upper slopes; the ridge is the watershed between Mailling Gully to the south and a smaller unnamed tributary to the north. These streams eventually drain into the Arthur River about 7 km west of the reserve. The Arthur River and adjacent Norcott Plains also run north of the reserve, about 3 km away. The reserve is a small L-shaped remnant with the longest east-west boundary (1.9 km) roughly parallel to the ridgeline/plateau. The north- south arm of the L measures approximately 1.2 km (Fig 2). Slopes descend gently off the ridgeline and the predominant aspect is north or north-west. A pattern of low undulating hills/ridges with interspersed small valleys and/or plains is typical locally and is a familiar topography for much of this inner wheatbelt region. Granite outcrops and/or lateritic breakaways are often found on the upper slopes or hilltops. Historically, many upland areas were not cleared for cropping because of the rougher topography. Also upland areas were generally abundant in the poisonous Gastrolobium species that killed domestic stock. Alternatively, some were left as ‘shade and shelter belts’. Today, very few of these upland remnants have survived completely intact. Significant numbers have had a reduction in tree cover due to past logging (e.g. for timber and fence posts), insect pests, disease etc, and this has occurred in a © Royal Society of Western Australia 2004
. Location of A21064 Nature Reserve, near Arthur River, in the south-west of Western Australia; also shown are 100 mm rainfall isohyets. 20 Journal of the Royal Society of Western Australia, 87(1), March 2004 relatively short time frame (Landsberg et al. 1990). The majority of these remnants are also depauperate in understorey taxa due to selective clearing (e.g. of ‘poison plants’), frequent grazing by domestic stock, changed burning regimes, nutrient enrichment, weed invasion, and other human influenced disturbances (Hobbs & Atkins 1988; Hobbs 1993; Panetta & Hopkins 1991; Pigott 1994; Yates & Hobbs 1997; Yates et al. 1999; Yates et al. 2000). The wheatbelt region as a whole has been altered from a mosaic of perennial native vegetation to predominantly cleared agricultural land with fragmented small bushland remnants (Hobbs 1998; Scanlan et al. 1992). A21064, which is surrounded by agricultural land, is no different. Beard (1980a) mapped the pre-existing vegetation cover of this entire region using aerial photography in conjunction with a wide-ranging examination of the remaining bushland remnants and their preferred habitat requirements (i.e. soil, slope, aspect, evelation etc). These vegetation maps show the reserve’s wider surrounding district as predominantly York gum (Eucalyptus loxophleba) and wandoo (E. wandoo) woodland, while several local upland areas (including A21064) are mapped as wandoo and mallet (Eucalyptus astringens) woodland. This is a reasonably accurate representation, although these upland areas also contain significant patches of sheoak (Allocasuarina huegeliana). Approximately 20-25 km west of the reserve, wandoo woodland predominates, but marri (Corymbia calophylla) and jarrah (Eucalyptus marginata) become more common about another 20 km further westwards within Hillman and Godfrey State Forest Blocks (Smith 1974). Powder bark wandoo (E. accedens) is more abundant amongst the York gums around the Narrogin area, about 35 km north of the reserve (Beard 1980b). Salmon gum (E.
km), while the Beaufort River area, about 30 km south of the reserve, has a mix of wandoo, yate (E. occidentalis), teatree (Melaleuca sp.), Casuarina obesa and samphire flats (Beard 1980a). Overall, the district was once dominated by open woodlands; however, patches of heath (often Dryandra dominated), herbfield and mallee were also relatively common. Flora surveys of wheatbelt remnants are sparse (Obbens et al. 2001). Although not intensive, Muir’s (1977a) pioneering surveys of 24 wheatbelt reserves are a notable exception. There are very few flora surveys of remnants from around this district, reflecting the high costs of surveying remnants within this vast wheatbelt region (i.e. 18 million hectares). The soon to be released Salinity Action Plan (SAP) surveys will change this situation. While larger remnants (i.e. >2000 ha) are certainly important for conserving biodiversity and helping to maintain many of the ecological processes of this region, this paper aims to highlight the important contribution of smaller remnants to regional biodiversity, particularly if they remain intact. A further aim is to present more botanical survey data for this significant region.
Methods The vegetation communities of Nature Reserve A21064 were interpreted from a 1996 aerial photograph and confirmed in the field during 1999 and 2002. Classification of these vegetation communities is based on Muir (1977b). This classification assesses vegetation structure by taking measures of lifeform/height class and canopy cover/density class to produce a vegetation type. For example, trees 15-30 m with a 10-30% canopy cover were designated woodlands, while the same trees with a canopy cover of 2-10% would be designated as open woodlands. To a significant extent this classification also reflects the species compositional differences. Additionally, brief investigations were made of the soils in each vegetation community. The soil surface was inspected and then shallow holes (3-5 cm depth) were made to assess soil texture and colour. The flora survey and collections were accomplished by walking along 13 transects (10 spaced at 150 m apart and 3 spaced at 100 m apart) that spanned the full width of the reserve in a north-south orientation. The first transect proceeded in a southerly direction from Noble Road and approximately 50 m in from the reserve’s north-east corner. Subsequent transects crossed every vegetation type several times using this technique. This transect survey was undertaken during mid/late spring (i.e. October and November 1998). An additional 8 surveys were also carried out between the summer of 1998 and the spring of 2002. On these occasions a ‘randomized stratified walk’ technique (Hopper et al. 1997) was used. This method involves specimen collections via random walks in each vegetation community. The purpose of this intensive surveying was to obtain a voucher specimen of each taxa and to compile a more complete vascular flora list. All specimens were submitted for incorporation at the WA Herbarium. The species names follow the currently accepted botanical binomials of WACENSUS (WA Herbarium census of Western Australian vascular plants), while conservation status of species is according to the Department of Conservation and Land Management’s (CALM) Declared Rare Flora and Priority Flora list (Atkins 2001). The authors also received invaluable information from WA Herbarium database records (WAHERB and FLORABASE). The term “total ‘Liliaceae’” refers to the number of closely related, but different new families that have been split from Liliaceae in recent years. For A21064 this includes the families Anthericaceae, Boryaceae and Phormiaceae.
Interpretation of the aerial photograph and site survey indicated ten major vegetation communities (Fig 2), including four variants (all explained below). However, there is considerable variability within some communities and at differing locations throughout the reserve. Additionally, there was a range of community boundaries, some very distinct (e.g. between pure mallet stands and wandoo woodland or when pure
herbfield areas). However, diffuse boundaries have been drawn at roughly midpoint where any two communities overlapped (e.g. as demonstrated when Low Woodland and Low Forest communities merge).
21 1 Open Woodland. Dominated by Eucalyptus wandoo with a generally very open, but variable understorey. This includes areas of almost pure Gastrolobium trilobum or Melaleuca aff uncinata or ‘parkland-like’ areas with numerous orchids/annuals/grasses and smaller shrubs. Many trees are large to 25 m high with a canopy density about 5 – 15% (i.e. very sparse to sparse). Soils are either grey coarse sandy loams or, at the reserve’s western end, brown coarse loams with some lateritic gravels. This community represents the top end of shallow drainage lines that form defined creeks further down slope outside the reserve boundaries.
Open Woodland. A variant of above, again, dominated by Eucalyptus wandoo of generally smaller stature and with a denser canopy cover, about 10 – 25% (i.e. sparse). Lying entirely on lateritic ridge country, it demarcates itself from community 1 along the line of a small breakaway. A sparse to mid dense understorey of predominately
residual soils on the top edge of the breakaway and up slope at the ridgeline. Elsewhere is fairly open with various scattered shrubs and some annuals on soils of red- brown clay loam with numerous gravels.
Low Woodland. A mixed woodland with a mid dense canopy cover (i.e. about 30 – 70%) consisting of almost equal proportions of Eucalyptus wandoo (up to 20 m high) and Allocasuarina huegeliana on grey-brown sandy loams sometimes with varying amounts of gravel. Understorey is variable including open areas of low shrubs, annuals and some grasses to mid dense areas of Acacia or Gastrolobium. 2a Low Woodland. A mixed woodland variant of above with mid dense canopy consisting of Eucalyptus wandoo (up to 20 m high) and interspersed individuals or patches of Eucalyptus astringens subsp astringens (Brown Mallet) and occasionally with scattered Allocasuarina huegeliana. Again, a variable understorey ranging mostly open to mid dense in parts. Soils are red-brown coarse clay loams with gravels and sometimes there is exposed lateritic hardcap.
3 Low Forest. Predominantly pure stands of Allocasuarina huegeliana with occasional scattered Eucalyptus wandoo and generally mid dense to dense canopy cover (i.e. > 70%). Soils are grey-brown to red-brown sandy or clayey sand loams sometimes with a little gravel. The understorey canopy cover is open to mid dense, including numerous annuals and commonly a tall Lepidosperma sp (FO204/98), Agrostocrinum scabrum and Hypocalymma angustifolium. This community occurs where granite is close to the surface and often outcropping or boulder stacks are nearby.
Woodland. Composed of pure stands of tall (i.e. 25 – 30 m) Eucalyptus longicornis with a very sparse understorey of Acacia erinacea, Acacia lasiocarpa var. sedifolia, a few sedges and annuals found on red-brown clay loams. These areas appear to be associated with shallow drainage zones.
Heath. A heath of mid dense to dense canopy cover containing a diverse mix of shrubs about 1 – 2 m high on grey-brown sandy clay loams with some gravel content. The families Myrtaceae, Proteaceae, Goodeniaceae, Papilionaceae and Stylidiaceae are well represented along with many others. This community occurs on the gentle mid slope areas of the reserve and never appears on the ridge top.
Heath. A variant of the above comprising a diverse mix of shrubs (about 1 – 2 m) with interspersed emergent shrubs (to about 3.5 m) namely Dryandra sessilis and Nuytsia floribunda. This unusual combination occurs on a localised sheet of white sand, which probably overlays lateritic and/or granitic profiles seen adjacent to this community. Eremaea pauciflora dominates although many other species are present.
Low Heath. A very diverse mix of small to mid sized shrubs (about 0.25 – 1.5 m) with a mid dense canopy cover found on white-grey clayey loams with occasional gravel content. This soil profile is possibly exposed and eroding kaolin, and occurs extensively on lower parts of the flattened ridgeline. This community contains the same families as outlined for community 5; however, it also has a marginally greater diversity of taxa than the above heaths. Figure 2 . Map of vegetation communities of A21064 Nature Reserve that include 1 and 1a Open Woodland, 2 and 2a Low Woodland, 3 Low Forest, 4 Woodland, 5 and 5a Heath, 6 Low Heath, 7 Thicket (Tall Heath), 8 Herbfield, 9 and 9a Mallet Woodland, 10 Mallee Woodland and G Rehabilitated gravel pits. Communities are described below. Obbens & Sage: Vegetation and flora of an upland remnant, Western Australian wheatbelt
22 Journal of the Royal Society of Western Australia, 87(1), March 2004 7 Thicket (Tall Heath). Comprising a dense mix of taller shrubs (about 1.5 – 3.0 m) dominated by Dryandra, particularly D. armata and D. nobilis, but including some other tall Proteaceae species (e.g. Adenanthos cygnorum and Hakea trifurcata) and occasionally interspersed mallees. These thickets are located on the flattened ridgeline. The soils are red-brown to grey-brown coarse clayey loams or sandy loams with abundant lateritic gravels, rocks and some exposed hardcap. 8 Herbfield. Exposed or near-surface granite sheets with some residual surface soil or soil pockets frequently covered by Borya sphaerocephala, mosses and lichens, but including numerous annual herbs and some sedges. Generally abutting or surrounded by Allocasuarina woodland.
Mallet Woodland. Dense pure stands of Eucalyptus astringens subsp astringens (about 10 to 20 m) with an almost absent understorey except for a few resilient shrubs and abundant bark litter. Soils are red-brown to brown coarse clay loams with numerous gravels. All occurrences in the reserve are on the ridgeline including one area adjacent to and on a lateritic breakaway slope. 9a Mallet Woodland. This community, a variant of the above, comprises more open and generally taller (about 15 to 25 m) stands of Eucalyptus astringens subsp astringens often interspersed with E. wandoo or Allocasuarina huegeliana and with variable canopy cover ranging from open to mid dense. The open to mid dense understorey includes Acacia celastrifolia, A. pulchella,
are red-brown to grey-brown clayey loams containing numerous gravels with rocks/hardcap regularly occurring within this ridgeline community. 10 Mallee Woodland. Consisting of various mallee species, but occasionally pure stands to 4 m high and sometimes with other tree species interspersed or with tall shrubs. In the western end of the reserve these mallees tend to be Eucalyptus aspersa, E. falcata, E. latens and E. thamnoides subsp megista while in other areas mainly E. incrassata and E. pluricaulis subsp pluricaulis. This community is located either on the ridge or the adjacent upper slope areas where the soils are red-brown loams with gravels. .
Rehabilitated gravel pits. Old gravel extraction sites that have been deep ripped and allowed to regenerate naturally. At this stage, the flora comprises mainly pioneer species and limited occurrences of several weed species.
Flora. A total of 323 vascular plant taxa (including 22 weed species) from 51 families was listed for Nature Reserve A21064 with dicots and shrub species being the predominant taxa for the reserve (Table 1). The most represented families were Myrtaceae (39), Proteaceae (29), Papilionaceae (26), Orchidaceae (26), Poaceae (20), total ‘Liliaceae’ (20), Asteraceae (17), Stylidaceae (17), Cyperaceae (16), and Goodeniaceae (12). Nine Poaceae and three Asteraceae species recorded are weeds. The genera with the greatest number of species were Stylidium (15), Eucalyptus (12), Acacia (10), Caladenia (9), Hakea (8), Lepidosperma (8), Dryandra (7), Drosera (6) and Austrostipa, Leucopogon, Dampiera, Goodenia, Melaleuca, Daviesia and Petrophile with five species each. One declared rare species (Conostylis drummondii) and seven priority species (Dryandra rufistylis, Eucalyptus
Dongolocking, Microcorys lenticularis and Thysanotus cymosus) were recorded for the reserve. Discussion Vegetation and habitat. The vegetation of the reserve is not unique because similar vegetation types or variants thereof can be found in other upland remnants in this region. Overall the vegetation of the reserve is relatively pristine and contains a wide representation of upland communities for its small size. This alone makes it quite special in
Plant type and lifeform for all taxa collected at A21064. Taxa Total Dicotyledons Monocotyledons Gymnosperms Pteridophytes Families
51 37 12 1 1 Genera 155 98 55 1 1 Taxa: (a) native 301
211 88 1 1 (b) exotic 22 11
0 0 Lifeform Tree 8 8 0 0 0 Mallee/Tree 1 1 0 0 0 Mallee 7 7 0 0 0 Tall shrub 19 18 0 1 0 Low shrub 113
112 1 0 0 Herb (annual) 42 33
0 0 Herb (perennial) 127 37 89 0 1 Vine 6 6 0 0 0 TOTAL 323 23 terms of value as public conservation estate. These woodlands can be moderately diverse due to the abundant annuals present, but more frequently it is the open heaths and patches of other communities within these woodlands that account for the greater proportion of species diversity, particularly perennial species (Yates
shrub taxa listed, the next highest being perennial herbs at 127 taxa, but with significantly less vegetative cover overall than the shrubs produce. Kataloq: publications -> Journal publications -> Клиники невролоэийа publications -> Dövlət Satınalmaları Journal -> Lincoln laboratory journal Journal -> Journal of the Royal Society of Western Australia, 84: 53-61, 2001 Journal -> Variation in seed production and germination in 22 rare and threatened Western Australian Verticordia (Myrtaceae) Journal -> Plants of Western Australian granite outcrops Journal -> Flora and vegetation of the Eastern Goldfields Ranges: Part Mt Manning Range Journal -> Flora and vegetation of the Eastern Goldfields Ranges: Part Middle and South Ironcap, Digger Rock and Hatter Hill Journal -> Flora and Vegetation of the Eastern Goldfields Ranges: Part Bremer Range Yüklə 91,66 Kb. Dostları ilə paylaş:
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