and broad-leaved bottle-tree Plate 9. Vine thicket (type 5) with large emergent ooline (Cadellia pentastylis) (Brachychiton australis), "Bimbadeen", Taroom (site 61).

( harpophylla), upper Zamia Creek, Palmgrove National Plate10. Vine thicket (type 8) with emergent brigalow Park, north-west of Taroom (site 52). 192

CHAPTER FIVE

LOCAL (LARGE-SCALE) PATTERN IN VINE THICKET AND ASSOCIATED BRIGALOW () VEGETATION IN CENTRAL .

Vine thickets and brigalow (Acacia harpophylla) communities are commonly associated over large areas of central inland Queensland. Vine thickets generally occupy more well-drained, elevated parts of the landscape, often merging with Acacia harpophylla communities on lower slopes, forming a layered open-forest in the transition zone (Johnson 1984).

These transitions are relatively narrow in areas of more pronounced relief, but areas of

Acacia harpophylla with a dense vine thicket understorey occurred extensively on gently undulating terrain prior to clearing. They are estimated (Gunn and Nix 1977) to have occupied at least 4000km2 in the central and southern Fitzroy catchment.

Gunn (1974) provided a brief description of vine thicket/soil relationships in his account of a catenary sequence on lateritised basalt in the Central Highlands. He described a soil sequence from deep red massive clay soils on the crest and upper slopes through shallow to deep dark reddish- brown to brown light to heavy clay soils on the upper slopes to deep reddish brown cracking clay soils on lower slopes. The corresponding vegetation sequence is bendee (Acacia catenulata) low open-forest through Macropteranthes leichhardtii-dominated vine thicket, then Acacia harpophylla open-forest with Macropteranthes understorey to A. harpophylla with Terminalia oblongata,

Lysiphyllum carronii and Geijera parviflora.

Johnson (1980) studied vegetation patterns along a 3.7 km transect at Brigalow Research

Station in central Queensland. Six communities were defined, including bonewood

(Macropteranthes leichhardtii) semi-evergreen vine thicket and brigalow (Acacia harpophylla) semi-evergreen vine thicket. M leichhardtii vine thicket formed a major unit on the highest section of the transect on a mosaic of duplex, gradational and clay soils, while A. harpophylla vine thicket occurred in a few plots on loamy duplex soils.

Johnsons (1980) analysis was based on a subset of 89 plots (i.e. every second plot), due to computational limitations. The present study seeks, using the full data set for the vine thicket 193 plots, to determine species patterns and abundance within these communities and to establish relationships with site attributes. The results also provide baseline data from which to assess the floristic changes which have occurred in a subset of 16 plots in the 25 years since the transect was established (see Chapter 6).

5.1 Description of the study area

The study utilises data from a permanently marked belt transect established by Johnson

(1980) on the Queensland Department of Primary Industries Brigalow Research Station (24°50S lat., 149°50E long.), c. 32 km NW of Theodore in central Queensland. The research station was established in 1963 during Stage 1 of the Fitzroy Basin (Brigalow) Land Development Scheme and comprises excisions from the properties "Thomby", "Highworth" and "The Rhyddings". The transect consists of 182 contiguous 20 m X 20 m plots (a total length of 3.7 km) from Roundstone

Creek easterly along the northern boundary of Brigalow Research Station. The transect was laid out during 1968-1970 and is buffered within a 400 m wide belt of retained vegetation. The adjacent paddocks were cleared between 1964 and 1966, and stock have been excluded from the transect since then.

The present study focuses on the vine thicket communities, which are confined to the western one-third of the transect (plots 11-66) (see Figure 5.1).

5.1.1 Climate

The climatic averages for Brigalow Research Station are given in Table 5.1. Daily rainfall totals have been collected since early 1966 and temperature, humidity and evaporation data are also available (Clewett et al. 1994). Annual rainfall is slightly above 700 mm, with two-thirds of this occurring during the summer period (October - March). There is a small but significant mid- winter rainfall peak (June/July). Longer-term rainfall data are available for "Coorada" and

Bauhinia Downs to the west and "Banana" and "Barfield" north of Brigalow Research Station (see

Table 5.2 and Clewett et al. 1994). Vegetation Group 1 5 6 5 3 5 4 5 3 5 4 3 5 2

20 f Wr ■, p v _ . - 19 1 1 18 Relative He.ght depth above 17 of soil datum A (m) 16 horizon 15 - _ . 14 2 3 4 3 2 2 2 2 2 2 2 2 6 4 3 4 5 5256443234345655555334223322222222 G. 04500000000000260141772242201230 82123405321000000000000 C. 13 1344112111111133553344434465533433545546^4333222222222222 E .G. 12 R RRRR R RRRR RRRR 11

10 _____ 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 R1 64 65 66 (E.G.) Environmental Group (1-6) (C.) Clay Content 1 =< 10%, 2 = 10-20, 3 = 20-30, 4 = 30-40%, etc. R = indicates plots re-measured in 1990-92. (G.) Gilgai 0 = 0%, 1 = 1-10%, 2 = 10-20%, 3 = 20-30%, etc.

FigureS.i Schematic diagram of Brigalow Research Station permanent transect, plots 1 1-36 showing vegetation groups and major site attributes. 195

5.1.2 Landform and soils

The topography of the transect is gently undulating to almost level and changes are generally at right angles to the transect. The geology is described in the 1:250 000 geological series map for Baralaba (Olgers, Webb, Smit and Coxhead 1966) as mainly soil and alluvia overlying the Triassic Moolayember Formation (map units Cz/Rm). The area forms part of the

Highworth Land System (land unit 7) of Speck et al. (1968). Soils were surveyed and described by Webb (1970)

Table 5.1 Mean monthly rainfall and temperature data for Brigalow Research Station (1965-1990).

Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. TOTAL Rainfall (mm) Mean 97 96 48 46 51 29 39 35 32 68 80 111 733 Median 75 79 39 19 41 23 32 26 20 57 75 86 708 Minimum 9 15 3 0 0 0 0 0 0 4 6 11 436 Maximum 227 297 134 227 280 89 172 177 166 233 181 361 1111

Temperature Mean Max. 33.4 32 31.2 28.6 25 21.6 21.3 23.3 26.5 29.6 31.4 33.1 28.1 Days >35°C 9 4 2 1 4 8 Mean Min. 20.8 20.4 18.8 15.1 11.8 7.5 6.3 7.3 10.4 14.6 17.7 19.8 14.2 Days <2.2°C 3 7 3

Table 5.2 . Mean and median monthly rainfall totals (mm) for the Bauhinia Downs-Moura district of central Queensland. (Source: Clewett et al. 1994)

Centre Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Tot. Records 1. Bauhinia Downs mean 104 107 65 43 35 37 33 24 28 49 61 96 683 100 years median 82 74 49 19 26 23 22 13 16 43 58 83 688 2. "Coorada" mean 105 114 68 49 41 36 36 22 29 57 68 98 726 80 years median 93 88 56 31 25 24 21 15 20 47 62 80 702 3. "Banana" mean 99 96 70 36 38 40 33 22 29 53 67 93 677 123 years median 88 85 52 22 26 28 21 14 18 43 64 85 685 4. "Barfield" mean 84 84 52 29 38 30 28 16 20 48 64 76 570 74 years median 76 65 35 19 33 20 21 11 13 41 59 73 565

5.2 Data collection

5.2.1 Vegetation data

From each 20 m X 20 m plot, 3 sets of data were collected (Johnson 1980). 196

(a) canopy and understorey trees. All with at least one stem greater than 2.5 cm diameter at 30 cm above the ground were regarded as trees for the purpose of data collection

(Johnson 1980). Each plot was sampled in four quarters (10 m X 10 m) and recordings made of density, height, diameter breast height and canopy cover. Canopy cover was estimated by projecting the canopy onto a 20 m tape stretched along the centre line of the transect. Because of the high density of stems of Macropteranthes leichhardtii, counts of this species were generally made only along the central 4 m strip (see (b) below).

(b) shrubs and lianas. This category included all woody plants over 30 cm high not recorded as trees. The sample area was defined as a 2 m belt each side of the centre tape. Data were recorded in four contiguous areas (each 5 m X 4 m) and pooled for the plot. Attributes recorded were density, height and canopy cover (which was estimated as for the trees).

(c) ground flora. The ground flora was taken to include all grasses and forbs as well as seedlings of trees, shrubs and lianas less than 30 cm in height. The sampling unit was a 75 cm X

60 cm quadrat placed at approximately 1.5 m intervals along the centre line. Ten quadrats were used in each plot and the data pooled.

Attributes recorded for each quadrat were density and canopy cover. The canopy was estimated in class intervals as described by Daubenmire (1959). Frequency was calculated on the basis of presence of species in the ten quadrats.

It was noted by Johnson (1980) that although the ground flora was sampled at the end of the summer growing season (early autumn 1970), rainfall had been below average and hence cover estimates were relatively low, while many ephemeral species were not recorded or were very sparse.

5.2.2 Environmental data

In addition to the vegetation data, eleven environmental attributes were measured for each of the 182 plots along the transect (Johnson 1980). They included soil, topographic and light parameters. 197

5.2.2.1 Soil

Soils in each of the plots were classified to principal profile form according to the

Northcote (1971) system. Johnson selected a subset of five attributes from these

classificatory units.

El. Primary profile group - three types (uniform, gradational and duplex) were

distinguished.

E2. pH of surface (10 cm) soil.

E3. Percentage clay content of surface soil - estimated in broad class intervals (5-10%).

E4. Depth to B horizon (cm).

E5. Presence of free carbonate in surface soil.

5.2.2.2 Topography

Johnson surveyed the transect recording, along the central line, the elevation of the plot boundaries relative to the first plot. Three attributes were estimated;

E6. Mean height of plot above datum (m).

E7. Percentage slope.

ES. Aspect (3 categories - easterly, westerly and level).

As was noted above, the transect has a very subdued relief, with a total range of elevation of 20 m over the 3.7 km (Johnson 1980).

5.2.2.3 Micro-relief

Two attributes were used to describe the extent of gilgai development;

E9. Percentage of plot occupied by gilgais.

MO. Depth of gilgais (1 - 3 scale - visual estimate). 198

5.2.2.4 Light

Ten light intensity readings were made at ca. 1.5 m intervals along the centre line in each

plot (Johnson 1980), with the light sensor held ca. 30 cm above the ground. The readings were

pooled (Ell) to provide estimates both of the light available to the ground flora and the density of

the combined tree and shrub strata (Johnson 1980).

Table 5.3 presents the 11 environmental attributes for each of the 56 vine thicket plots (11-66).

5.3 Data Analyses

From the vegetation data collected by Johnson (1980) (see above) for plots 11 - 66, two

subsets were selected for analysis in the present study;

(a) canopy and understorey tree data (i.e. stems _ 2.5 cm diameter). Importance values (Curtis and McIntosh 1950) were calculated for each species, viz.

I.V. = Relative density + relative dominance (basal area) + relative frequency.

Relative frequency is based on occurrence in each of the 10 m X 10 m subplots. Because of the large numbers of stems of Macropteranthes leichhardtii where it predominates, densities, basal areas and frequencies of this species were extrapolated from counts in the 4 m central belt, i.e. 10 m x 2 m subplots.

(b) shrubs and lianes (i.e. stems < 2.5 cm diameter, but  30 cm in height).

A modified importance value was calculated, viz.

I.V. = Relative density + relative cover + relative frequency.

The two vegetation data sets and the environmental data for the 56 plots were classified using the Bray-Curtis dissimilarity measure and flexible UPGMA clustering (13 = - 0.1) (see

Chapter 3.4) within the PATN package (Belbin 1992). A second association measure (mean 199

Table 5.3 Environmental attributes for Brigalow Research Station transect plots 11-66.

Site-group Environmental Attributes Plot Veg. Envt El E2 E3 E4 E5 E6 E7 E8 E9 E10 El 1 11 1 1 3 6.87 12.5 15.24 0.00 16.58 2.06 1 0 0 480.10 12 1 3 3 6.75 22.5 13.46 0.00 17.2 0.08 1 40 1 322.00 13 5 4 1 6.87 42.5 0 0.00 17.23 2.46 1 50 1 289.10 14 5 4 1 6.75 39.2 10.16 0.00 17.98 1.26 1 0 0 256.40 15 5 1 3 7.00 22.5 30.48 0.00 18.36 0.47 1 0 0 246.20 16 5 1 3 7.25 15.0 27.94 0.00 18.5 0.67 1 0 0 426.40 17 6 2 3 7.87 15.0 20.32 0.00 18.71 0.43 -1 0 0 270.00 18 6 1 2 7.00 12.5 18.54 0.00 18.58 0.13 1 0 0 416.90 19 6 1 2 6.75 12.5 18.54 0.00 18.62 0.15 1 0 0 204.10 20 6 1 2 6.75 12.5 15.24 0.00 18.66 0.47 1 0 0 213.90 21 6 1 2 6.75 12.5 15.24 0.00 18.81 0.08 1 0 0 323.80 22 6 1 2 7.12 12.5 15.24 0.00 18.83 0.08 1 0 0 123.60 23 6 1 2 6.50 12.5 15.24 0.00 18.85 0.26 -1 0 0 130.60 24 6 1 2 6.87 12.5 12.19 0.00 18.78 0.29 -1 0 0 161.00 25 6 3 3 6.87 12.5 10.16 0.00 18.69 0.79 1 15 3 157.00 26 5 3 3 7.12 26.7 13.46 0.50 18.93 0.59 -1 60 3 355.80 27 5 5 1 7.37 51.8 0 0.50 18.75 0.36 -1 0 0 419.00 28 3 5 1 7.62 38.3 4.32 0.00 18.64 0.54 -1 10 3 311.20 29 5 3 3 7.75 30.0 7.62 0.25 18.47 1.07 -1 40 3 401.60 30 5 3 3 6.37 38.3 3.3 0.25 18.15 0.36 1 5 3 341.00 31 4 4 1 7.75 45.8 0 0.50 18.26 0.26 1 70 2 326.00 32 4 4 1 7.37 45.8 0 0.00 18.34 0.21 1 65 2 432.10 33 5 4 1 8.37 41.7 3.3 0.25 18.4 0.56 1 20 1 458.20 34 5 3 3 7.62 16.7 15.24 0.25 18.57 1.02 -1 15 2 213.00 35 3 4 1 6.62 40.8 5.84 0.00 18.26 0.87 1 40 1 453.00 36 5 4 1 6.62 51.5 0 0.00 18.53 0.18 1 20 1 394.20 37 5 6 1 8.37 39.2 5.08 0.50 18.58 0.44 -1 15 1 184.10 38 5 5 1 8.25 32.5 5.08 0.00 18.45 0.71 -1 0 0 340.70 39 5 5 1 6.87 29.2 5.33 0.00 18.23 0.21 -1 10 3 309.40 40 5 3 3 7.00 15.8 14.73 0.00 18.17 0.71 -1 20 2 185.30 41 5 3 3 7.12 20.8 10.92 0.00 17.95 0.00 0 30 2 238.00 42 5 4 1 6.87 33.3 2.54 0.00 17.95 0.77 1 0 0 485.00 43 5 3 3 7.00 24.2 20.32 0.00 18.05 1.33 -1 40 3 248.80 44 4 3 3 6.75 30.2 20.32 0.00 17.64 0.90 1 80 3 314.50 45 4 5 1 7.62 42.7 10.16 0.00 17.92 0.09 -1 15 2 363.30 46 4 4 1 6.50 55.0 0 0.00 17.89 0.03 1 10 2 324.10 47 4 5 1 6.37 45.0 2.54 0.00 17.9 0.20 -1 20 2 340.50 48 4 5 1 6.62 41.7 2.54 0.00 17.84 0.57 -1 30 1 456.30 49 4 4 1 6.87 45.8 0 0.50 17.67 0.77 1 40 1 435.70 50 4 6 1 6.50 41.7 0 0.50 17.9 0.47 -1 0 0 196.10 51 4 4 1 7.00 44.2 2.54 0.50 17.76 0.84 1 50 2 255.20 52 3 3 3 7.00 25.0 7.62 0.50 18.01 1.29 -1 30 2 304.60 53 5 3 3 8.00 27.5 10.92 0.50 17.62 0.27 1 20 2 307.60 54 5 3 3 7.37 32.0 17.78 0.50 17.7 0.56 -1 10 1 348.90 55 5 2 3 6.87 19.2 24.89 0.00 17.53 0.07 -1 0 0 119.70 56 5 2 3 7.37 12.5 21.08 0.00 17.51 0.27 -1 0 0 383.80 57 5 2 3 7.62 25.0 11.94 0.00 17.43 0.16 -1 0 0 608.80 58 5 2 3 7.00 25.0 13.46 0.00 17.38 0.58 -1 0 0 435.40 59 5 2 3 7.75 12.5 22.86 0.00 17.2 0.87 -1 0 0 432.40 60 2 2 3 6.75 12.5 27.94 0.00 16.94 1.14 -1 0 0 228.20 61 2 2 3 6.75 12.5 27.94 0.00 16.59 1.27 -1 0 0 197.20 62 2 2 3 6.75 12.5 36.83 0.00 16.2 0.97 -1 0 0 219.50 63 2 2 3 7.37 12.5 45.72 0.00 15.91 0.89 -1 0 0 165.70 64 2 2 3 6.87 12.5 37.34 0.00 15.64 0.78 -1 0 0 378.20 65 2 2 3 6.75 12.5 29.21 0.00 15.4 0.63 -1 0 0 369.60 66 2 2 3 6.00 12.5 38.1 0.00 15.21 0.24 -1 0 0 413.20 200 square of Euclidean distance)(MSED) was used with the environmental data, followed by clustering based on Wards Sum of Squares (Belbin 1992).

Ordinations were carried out using detrended correspondence analysis (DCA) and semi- strong hybrid multidimensional scaling (SSH) within PATN (see Chapter 3.4). Relationships between classificatory groups and environmental factors were explored using the group statistics (GSTA) and principal axis correlation (PCC) procedures within PATN. Other statistical analyses (non-parametric procedures) were undertaken within the Statistica for Windows package (see Chapter 3.4).

5.4 Results

5.4.1 Vegetation classifications

(a) canopy and understorey trees

Agglomerative classification of importance value index data for the 33 species produced 6 groups of 2 or more plots (see Figure 5.2 and Table 5.4). The four main vegetation groups comprise 7, 10, 25 and 9 plots respectively and are more or less discrete entities (see Figure 5.3).

They correspond closely with the units recognised by Johnson (1980), viz. vine thicket (group 6), brigalow/vine thicket (with or without Macropteranthes leichhardtii dominant) (groups 2 and 5) and brigalow/belah (group 4). Group 3 (3 plots) occupies transitional sites between groups 5 and

4 and group 2 includes the two westernmost plots. The groups are described further below.

(b) shrubs and lianes

The classification of the understorey and vine component of the vegetation, also at the 6- group level, showed limited agreement with the groups derived from canopy data. Group 2 is equivalent to (canopy) group 4, the Acacia harpophylla - Casuarina cristata community. The most abundant understorey species in this community is the chenopodiaceous shrub Rhagodia spinescens, which has a mean importance value index (IVI) of 0.43. Group 6 occurs at the eastern end of the transect, mostly in association with (canopy) group 2. Characteristic understorey species here are Carissa ovata and Canthium vacciniifolium (mean IVIs of 0.31 and 0.12). 201

The largest understorey groups (groups 4 and 5) are dominated by small stems of

Macropteranthes leichhardtii and Croton insularis. Group 4 (13 sites) is broadly equivalent to

(canopy) group 6, the "pure" vine thicket community. M leichhardtii has a mean IVI of 0.35. The largest group, group 5 (19 sites), has less dense M leichhardtii (IVI 0.15) and correspondingly higher abundances of Carissa ovata (0.30).

5.4.2 Environmental classifications

Results of the two classifications using environmental attributes were almost identical, with 54 plots being placed in equivalent groups at the 5-group level. Plots 23 and 24 (vine thicket plots) were placed in groups 1 and 2 respectively using the Bray-Curtis and MSED association measures. Group definitions are presented in Table 5.4.

Table 5.4 Comparison of site-groups produced by classification of vegetation and environmental data for Brigalow RS transect plots 11-66.

(a) Importance value indexes

Group No. Plots 1 2 11 12 2 7 60 61 62 63 64 65 66 3 3 28 35 52 4 10 31 32 44 45 46 47 48 49 50 51 13 5 25 13 14 15 16 26 27 29 30 33 34 36 37 38 39 40 41 42 43 53 54 55 56 57 58 59 6 9 17 18 19 20 21 22 23 24 25

(b) Environmental attributes*

Group No. Plots 1 10 11 15 16 18 19 20 21 22 23 24 2 13 17 55 56 57 58 59 60 61 62 63 64 65 66 3 13 12 25 26 29 30 34 40 41 43 44 52 53 54 4 11 13 14 31 32 33 35 36 42 46 49 51 5 7 27 28 38 39 45 47 48 6 2 37 50

* using Bray - Curtis association measure.

The distributions along the transect (see Figure 5.1) of the groups derived from environmental and vegetation data respectively correspond quite closely, indicating the influence of edaphic factors on vegetation patterns. These relationships are explored further below. 1.2790

1.0496

0.8202

0.5907

0.3613 Gp1 Gp2 Gp3 Gp4 Gp5 Gp6

3 10 25 9 n ,., 2 7 C> N Figure 5-.2 Classification of Brigalow Research Station transect plots 1 1-66 based on importance values and Bray-Curtis coefficient with UPGMA clustering. 203

Brigalow RS transect - vegetation groups

1.5

• 1 ■ • 0.5 - • s• Group 1 • ■ Group 2 cv o A Group 3 it 0 o Group 4 X 0 Group 5 -0.5 o Group 6 o 41)

-1 0 O

-1.5 -1.5 -1 -0.5 0 0.5 1 1.5 DCA 1

Brigalow RS transect - vegetation groups

1.5 • 0 0 • 0 Group 1 O 0.5 • ■ X ■ Group 2 C•1 0 ■ A Group 3 CC 0 ■ o Group 4 0I Group 5 • o Group 6 o A -0.5 X 0 o 0 O 0 x a -1.5 -1 -0.5 0 0.5 1 SSR 1

Figure 5.3 Ordination (DCA and SSR) of Brigalow Research Station transect plots 11-66. SymboLs show site-groups based in classification (B-C/UPGMA clustering) of importance data. 204

5.5 Description of vegetation groups.

The mean importance value indices and number of records of each canopy species per group are presented in Table 5.5. Approximately half these species (16) occur in fewer than 10 plots, while the most frequent are Alectryon diversifolius (51 plots) and the alien Opuntia tomentosa (52 plots).

The four main groups are differentiated primarily by the presence and relative importance of the three species Acacia harpophylla, Casuarina cristata and Macropteranthes leichhardtii.

Groups 2, 4 and 5 comprise brigalow vegetation, with Acacia harpophylla either dominating the canopy or emergent above low trees of vine thicket species. Group 6 is characterised by an absence of A. harpophylla.

Groups 2 and 5, as noted above, have a well-developed vine thicket understorey. In group 5, this is generally dominated by Macropteranthes leichhardtii, but at the eastern end of the transect, M leichhardtii is absent from most of the plots making up group 2.

Group 2 also has emergent cambageana, and significant vine thicket species include Alectryon diversifolius, Canthium vacciniifolium, Ehretia membranifolia and Geijera parviflora. After Macropteranthes leichhardtii, the most abundant vine thicket species in group 5 are Opuntia tomentosa and Ehretia membranifolia (see Table 5.5).

Group 4 is essentially a woodland to open-forest of Acacia harpophylla and Casuarina cristata as co-dominants. Although vine thicket species are present (e.g. Alectryon diversifolius, Geijera parviflora), they do not form a definable low tree layer.

The vine thicket community characterising group 6 is also dominated by Macropteranthes leichhardtii, but other significant species include Acacia fasciculifera, ,

Canthium vacciniifolium, Croton insularis and Ehretia membranifolia.

Group 1 (plots 11 and 12) is distinguished from group 2 by the presence of Croton phebalioides and Macropteranthes leichhardtii and the absence of Canthium vacciniifolium and 205

Table 5.5 Mean importance value indices for tree and shrub species (2.5 cm dbh) - Brigalow RS transect plots 11-66.

Species Gp 1 (2) Gp 2 (7) Gp 3 (3) Gp 4 (10) Gp 5 (25) Gp 6 (9) ACACFASC 1.8 (3) 1.3 (4) 21.2 (8) ACACHARP 52.8 (2) 50.9 (7) 93.5 (3) 97.2 (10) 43.0 (23) ALECDIVE 6.9 (2) 30.6 (7) 12.5 (2) 15.1 (10) 11.1 (22) 9.4 (8) APOPANOM 12.7 (2) 6.8 (6) 6.9 (1) 3.7 (4) 6.2 (17) 7.0 (4) ATALSALI 3.0 (1) 1.8 (1) 2.7 (5) 19.8 (8) BRACRUPE 8.6 (3) 1.4 (1) 9.8 (8) 4.9 (5) BREYOBLO 0.8 (1) CANTBRIG 14.7 (6) 2.0 (1) 1.6 (1) CANTVACC 52.2 (7) 1.7 (1) 1.6 (1) 10.6 (18) 16.4 (7) CAPPLORA 1.1 (2) 1.7 (1) 0.6 (1) 2.1 (6) 8.1 (7) CASSAUAN 0.7 (1) CASSTOME 1.7 (1) 1.2 (2) 0.9 (3) 1.4 (2) CASUCRIS 5.9 (4) 34.5 (3) 75.3 (10) 10.1 (2) 7.4 (3) CITRSPIN 2.9 (3) 1.6 (1) 0.2 (1) 0.5 (1) CROT1NSU 3.2 (2) 23.7 (3) 4.7 (2) 8.6 (18) 27.0 (9) CROTPHEB 27.2 (2) 0.5 (1) DENHOLEA 1,3 (2) 1.3 (2) 0.4 (2) 0.5 (1) DENHPITT 2.2 (3) 0.5(1) DIOSHUMI 6.8 (1) 3.2 (5) 0.6 (2) 1.9 (2) DIPLIXOR 1.7 (1) 0.9 (2) 1.8 (3) EHREMEMB 8.1 (1) 33.2 (7) 22.5 (3) 4.9 (4) 14.9 (23) 14.5 (9) EREMGLAU 2.7 (1) 2.0 (3) ERYTAUST 2.6 (3) EUCACAMB 51.5 (2) 25.6 (6) 20.1 (5) 3.1 (2) FLINCOLL 3.1 (1) 2.4 (8) 2.4 (3) GEIJPARV 36.4 (2) 35.7 (7) 16.7 (3) 17.4 (9) 13.8 (21) 0.5 (1) LYSICARR 7.7 (1) 1.0 (1) 1.2 (3) MACRLEIC 34.1 (2) 1.4 (1) 62.8 (3) 5.1 (3) 135.1 (24) 135.3 (9) MYOPDESE 10.5 (7) 0.2 (1) NOTEMICR 0.6 (1) 0.7 (1) OPUNTOME 47.1 (2) 11.9 (6) 14.7 (3) 34.1 (9) 18.0 (25) 7.2 7) PLANCOPU 3.0 (3) VENTVIMI 0.8 (1) 1.7 (1) 0.8 (2) 6.6 (3)

Figures in parenthesis are the numbers of plots (in each group) each species was recorded from.

C. sp. "brigalow" and by significantly higher importance values for Eucalyptus cambageana and Opuntia tomentosa.

Group 3 consists of three widely separated plots (28, 35 and 52) which appear to be transitional between groups 4 and 5 (see Figure 5.1). They differ from group 4 mostly in their lack of Eucalyptus cambageana and Myoporum deserti and in their lower abundance of Casuarina cristata and contrasting higher abundance of Macropteranthes leichhardtii, Croton insularis and Ehretia membranifolia. 206

5.6 Environmental relationships.

Five of the 11 environmental attributes were found to be highly correlated with the ordination vectors (principal axis correlation and Spearman rank order correlation, see Table 5.6). Analysis of variance (by the Kruskal-Wallis test) showed these effects to be significant (P<0.05) for all five attributes, viz. great soil group, % clay, depth to B horizon, altitude (height above datum) and % gilgai (see Table 5.7). These attributes are also illustrated in Figure 5.1.

Table 5.6 Correlations between 11 environmental attributes and vector scores from ordinations of vegetation data for BRS transect plots 11-66.

Principal axis correlation (PCC) Attribute DCA/FCC SSR/PCC El. Great soil group 0.458 0.484 E2. p1-1 0.304 0.270 ...... w.

::::::. ..:.:.:.:.,..:.::. . E. Carbonate 0.34 0 i§i. : ..,iic1: :. •••• •••• ••••• • . :::::::::::. ::,.... .,,....., E7. % slope 0.370 0.279 E8. Aspect 0.348 0.292 :•:.....x.:•:•:::.:4igii ...... ...... . :.:.:.:.:.:.:.:.:.:.:,...,... ::::••:: •••.,•::::... Ell. Light 0.259 ii.3 i

The most significant differences between vegetation groups (P<0.001) were recorded for altitude, % clay and depth to B horizon (see Table 5.7). Minor differences were also recorded for great soil group and % gilgai (these latter were also correlated with % clay and depth to B horizon).

Group 4 (brigalow/belah) occupies heavy uniform clay soils with minimal A horizons. These soils have frequent, well-developed gilgai micro-relief

Groups 2 and 6 occur predominantly on relatively light clays with well-developed A horizons. Group 6 (bonewood) occurs on duplex (texture-contrast) soils on the most elevated (and presumably well-drained) part of the transect. Group 2, on the other hand, occupies a significantly lower position in the landscape and the (gradational) soils have particularly deep A horizons (see Table 5.7). 207

Table 5.7. Analysis of variance and comparison of group means for 11 environmental attributes - vegetation groups based on importance value indices for tree and shrub species in BRS transect plots 11-66.

Attribute "H" value Significance El. Great soil group 19.092 . E2...... pH. . 10.793 39.549 28.565 E5. Carbonate 8.794 n .s. 36.274 E7. % slope 11.182 E8.Aspect 11.443 • " •:••••: 22.414 ...... 17.927 10.202

Group mean comparisons:

Attribute Group %clay depth to B altitude (m) %gilgai horizon (cm) 1 17.5 14.4 156.5 20 2 12.5 34.7 155.3 0 3 34.7 5.9 157.7 26.7 4 43.8 3.8 157.4 38 5 29 11.9 157.5 14.2 6 12.8 15.6 158.2 1.7

Significant differences:# 3>2 3<2 3>2 4<2 4>1 4<2 4>2 4<5 4>2 5<2 5>2 5>2 6<2 6>1 5<4 6>4 6>2 6<3 6>4 6<4 6>5 6<5

using Tukey honest significant difference (HSD) test for unequal numbers

= P<0.05, = P<0.01, = P<0.001.

Group 5 (brigalow/bonewood) is found on soils of intermediate clay content and depth of topsoil. All three great soil groups are represented, with uniform and duplex soils predominating.

These soils have on average a significantly higher clay content (P<0.05) (and correspondingly greater gilgai development) than those associated with groups 2 and 6. 208

5.7 Discussion

Johnson (1980) identified a broad moisture gradient along the Brigalow RS transect from

Macropteranthes leichhardtii vine thicket at the western end, diverging through various Acacia harpophylla communities to Eucalyptus melanophloia - A. harpophylla woodland and Dichanthium grassland at the eastern end.

The present study, utilising a subset of the original data, has confirmed and clarified the soil/vegetation patterns distinguished by Johnson for the western end of the transect. The boundaries of the Acacia harpophylla - Casuarina cristata community on gilgaid cracking clay soils are as defined by Johnson and the brigalow/vine thicket community (community 2) occurring from plot 60 eastward on duplex soils with deep A horizons is also maintained as a distinct entity (group 2) in the present analysis.

With data from contiguous plots, it is possible to distinguish two communities within

Johnsons community 1 (Macropteranthes leichhardtii - dominant vine thicket) although there is some intergradation (see Figure 5.3). Johnson (1980) described the soils as a mosaic of duplex, gradational and clay soils. M leichhardtii is dominant throughout, but on the more clayey soils,

Acacia harpophylla is also a major component (see Table 5.5), forming vegetation group 5, as distinct from group 6 (pure M leichhardtii) which occurs on the deeper duplex and gradational soils.

There are two main zones of soils with relatively deep A horizons (see Figure 5.1), between plots 13 and 26 and from plot 59 eastward. Webb (1971) suggested that the first zone which represents the highest part of the transect, is part of an old levee bank associated with Roundstone

Creek. The second zone could well represent material blown and/or washed from the levee and in fact now has a deeper A horizon than the first area.

The freely-draining soils on the levee are occupied by a bonewood - dominant community.

Soils with shallower A horizons carry a structurally and floristically intermediate community of brigalow with a vine thicket understorey dominated by bonewood. The duplex soils to the east are also occupied by a brigalow/vine thicket community but despite the deeper A horizon, bonewood is absent from these plots. Some possible reasons for its absence are suggested in Chapter 7. 209

The only account of comparable vine thicket-soil relationships is given by Gunn (1974) in his study of a catenary sequence on lateritised basalt in the Central Highlands. Gunn described a soil sequence from deep red massive clay soils on the crest and upper slopes through shallow to deep dark reddish-brown to brown light to heavy clay soils on the upper slopes to deep reddish-brown cracking clay soils on lower slopes. The corresponding vegetation sequence is bendee (Acacia catenulata) low open-forest (with scattered emergents of Eucalyptus melanophloia and E. populnea) through Macropteranthes leichhardtii-dominated vine thicket, then Acacia harpophylla open-forest with Macropteranthes understorey to A. harpophylla with Terminalia oblongata, Lysiphyllum carronii and Geijera parviflora.

Gunn (1974) derived his catena from sampling areas near Capella and Gindie. The Gindie locality appears from the accompanying map to be the same general area as sites 35 and 43 from the detailed vine thicket survey (Chapter 3). The vegetation sequence noted at this location ("Bonnie

Doon") was Macropteranthes on the crest, Macropteranthes/Acacia catenulata on the upper and middle slope and Acacia harpophylla on the lower slope.

Gunn concluded that soil reaction is not a major controlling factor in the distribution of

Macropteranthes leichhardtii. He noted that this community "almost always occupies water- shedding sites on crests and upper slopes and good drainage is the most consistent common attribute" (Gunn 1974). He also noted that soils were mainly shallow, commonly gravelly and were capable of absorbing and conducting water rapidly. The soils occupied by Macropteranthes vine thicket had the lowest water retention capacity of the entire sequence and Gunn concluded that the roots of this species were able to extract water from the underlying clays.

In the present study, Macropteranthes leichhardtii vine thickets have been found also to occupy higher, more freely drained positions in the landscape relative to Acacia harpophylla communities.

In addition to enabling soil/vegetation relationships to be clarified, the Brigalow Research

Station data set has provided an opportunity to compare the results of the point-clump sampling approach used in the vine thicket survey (Chapter 3) with quadrat-based data. Site 7 from the detailed survey was located along the transect, with subplot 7A based on the western marker peg for transect plot 16 and 7B based on the marker peg for plot 18. Samples from the two procedures are compared in Table 5.8. 210

In terms of number of trees (..10 cm dbh) and species composition, subplot 7A and quadrats

15/16 have produced very similar results. The plotless sample has recorded single individuals of two species (Croton insularis and Notelaea microcarpa) which were not recorded by the quadrat method.

Subplot 7B, however, even when its larger size is taken into account, still has twice the density of stems compared with the sample from quadrats 17/18. This discrepancy can be explained largely in terms of the time interval between the quadrat measurements (1968/70) and the plotless survey

(1987). During this period there has been considerable recruitment of Macropteranthes stems into the 10 cm plus diameter classes along this section of the transect (i.e. a 75% increase, see Chapter

6).

Table 5.8 Comparison of records of vine thicket trees along Brigalow RS transect using quadrat (20 m X 20 m) and plotless sampling.

Species Transect Point clump 15/16 17/18 SO7A SO7B

ACACFASC 1 1 1 2 ALECDIVE 1 APOPANOM 1 1 ATALSALI 1 2 BRACRUPE 1 1 1 CAPPLORA 1 CROTINSU 1 EHREMEMB 1 1 2 2 FLINCOLL 1 1 1 GEIJPARV 2 4 MACRLEIC 15 10 19 23 NOTEMICR 1 OPUNTOME 1 1 1

Total 23 10 32 32

Area (m2) 400 400 550 610

The Brigalow Research Station vine thicket community (site S07) is representative of a widespread series of Macropteranthes leichhardtii stands which form a major structural and floristic unit within the vine thickets of central and southern Queensland (see Chapter 3). The occurrence of

M leichhardtii on soils with relatively deep, light-textured A horizons at Brigalow appears to be typical of its site preferences over much of the Central Highlands.

This part of the study has confirmed, with an expanded data set and modern numerical programs, the vegetation/soil patterns described by Johnson (1980). It has permitted the 211 selection of representative subsets of brigalow/vine thicket (vegetation group 5) and vine thicket

(vegetation group 6) quadrats for re-measurement to determine vegetation changes since establishment of the transect in 1968/70. It has also prompted the choice for re-measurement of two additional sets of quadrats in ecotonal situations adjacent to vine thicket vegetation. In the first situation (plots 12-14), the soil properties appear to be unfavourable for development of M leichhardtii-dominated vine thicket, whereas in the second (plots 58-61), soil properties are apparently non-limiting.