and broad-leaved bottle-tree Plate 9. Vine thicket (type 5) with large emergent ooline (Cadellia pentastylis) (Brachychiton australis), "Bimbadeen", Taroom (site 61).
(Acacia 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 (ACACIA HARPOPHYLLA) VEGETATION IN CENTRAL QUEENSLAND.
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 plant 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.
Johnson s (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°50 S lat., 149°50 E 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 plants 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 Ward s 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)