CHAPTER 6
ciinIkcm-nTsa. Ics AN D FTRF_] VULNERABILITY ASSESSMENT OF THE DRY RATNP-ORET REOURCE
6.1 Introduction
This chapter presents the results of investigations into the configuration and some key characteristics of the dry rainforest patches, leading to the development of a procedure for classifying the fire vulnerability of dry rainforest patches.
In recognising the significance of fire to dry rainforest communities (as discussed in Chapter 2), certain characteristics of the dry rainforest patches that occur in the Apsley - Macleay Gorges are thought to be relevant in evaluating the importance and perhaps the historical role of fire to each patch and to the rainforest resource as a whole. In this chapter, the relevant patch characteristics are categorised into fire susceptibility factors and fire proneness factors which are discussed below. These two factors are subsequently combined into a fire vulnerability index.
6.2 Characteristics Determining The Fire Susceptibility and Fire Proneness of Rainforest Patches
6.2.1 Fire Susceptibility
As used in this thesis, the fire susceptibility of dry rainforest patches relates to the perceived impact a fire event or series of fire events would be likely to have on rainforest
81 Chapter 6 patches. That is, it refers to the significance of fire to the integrity and continued existence of the rainforest patches should a fire event occur. Susceptibility does not refer to the likelihood of a fire event occurring, a matter discussed under the heading of fire proneness in the next section.
The configuration of patches (i.e., their shape, size and area perimeter ratio) is thought to be the primary variable influencing their fire susceptibility. For example, it appears that the significance of and potential for fire damage was greater for the smaller and more linear shaped dry rainforest patches and less for the larger, more compact patches. Furthermore, the greater distance of boundary relative to the patch area (characteristic of the smaller, linear shaped patches and reflected in the measurement of their area : perimeter ratio) ensure that potential fire impacts would be significant to the integrity and continued existence of the patch as a whole. The protective nature of the rainforest microclimate is less well developed in these patches and would be likely to break-down more rapidly than in the larger, compact patches with high area : perimeter ratios.
The current configuration of a patch may, in addition to indicating its current fire susceptibility, also reflect the past impact of fire. Indeed, patch configuration may largely be the result of fire superimposed on other controlling factors, including edaphic and topographic conditions. As such, therefore, alteration of fire regimes may permit patch configuration to change and hence the currently perceived susceptibility of the patch may also alter.
6.2.2 Fire Proneness
The fire proneness of rainforest patches is somewhat independent of susceptibility and refers largely to those factors that have some bearing on the actual potential for fire occurrence and its likely behaviour in the vicinity of patches. Patch fire proneness characteristics include: patch
82 Chapter 6 physiographic factors (i.e., aspect, slope angle, topographic position and elevation); the flammability and fuel loading of adjoining vegetation communities; and also climatic factors. In essence, fire proneness refers to the actual likelihood of a particular rainforest patch being influenced by fire.
6.2.2.1 Physiographic Factors
Physiography is a major factor governing fire proneness through its influence on fire behaviour. The most significant components of physiography are aspect, slope angle, topographic position, local relief or elevation, and gorge type and orientation.
As aspect influences both the amount of solar radiation an area receives and also the degree of exposure to prevailing winds, those dry rainforest patches with a predominantly north-west aspect are likely to be drier than those with south-east aspects and hence may be more fire prone and / or likely to reflect greater past fire impact. While being drier and permitting fuels to dry out faster, north-west aspects also may tend to support less vegetation and thus less potential total fuel loads. However, the drier, desiccating conditions of the north-west aspect may also slow litter decomposition, thereby permitting fuels to accumulate. Further, aspects facing the prevailing winds may also be subject to more frequent and intense fires. Fire weather in N.S.W. is most serious when hot, dry winds blow from the inland, principally the north-west (Luke and McArthur 1978, 291).
Slope modifies fire behaviour in much the same way as wind. Increasing slope angle and wind speed bring flames into closer contact with the fuel bed and result in more efficient preheating by radiation and more efficient ignition by point contact (Cheney 1981, 171). Thus, fires tend to burn more rapidly upslope (up to approximately 30° slope after which fuel discontinuities may occur ) and less rapidly downslope (McArthur 1962; Cheney 1981, 172). Consequently, up to a point, fire spread and intensities are likely to be greater on
83 Chapter 6 the steeper slopes in the gorges and hence are likely to have a greater impact on those dry rainforest patches that occur there.
The topographic position of patches is particularly important with regard to both fire occurrence and fire behaviour. Both meso-scale and micro-scale meteorological variables and the accompanying influences on fuel moisture content and wind speed near the ground vary with topographic position in the landscape (Cheney 1981, 171). Further, as a general rule, dry rainforest patches positioned in gully lines are probably relatively protected from fire, both in terms of climatic factors and fire occurrence, with these positions usually being moister. In addition, fire influences on these gully-line patches are usually only possible from above the community. Indeed, patches in these positions may actually be "fire-safe", although their current refugial distribution may reflect past fire occurrences and / or current fire limits. Patches in other topographic positions have greater potential for fire impact, as fire potentially may occur both upslope and downslope of the dry rainforest patch and conditions are likely to be less mesic.
As a general rule, minimum and maximum temperatures decrease with increasing elevation. Accordingly, rainforest patches at lower elevations are likely to experience higher summer temperatures than patches at higher elevations, and hence may dry out more rapidly. Thus, fires may be more frequent and/or more severe at lower elevations (Cheney 1981, 171).
6.2.2.2 Fuel and Flammability Factors
The nature and proximity of adjoining vegetation communities to dry rainforest patches may have a substantial bearing on the relative proneness of patches to fire events and the intensity of individual fire events. Furthermore, the top and bottom margins of patches have differential proneness to fire. They also have differential likely response related to differing
84 Chapter 6
fire intensities that are likely to occur on the upslope and downslope positions of patches.
Fuel levels, flammability and fire frequency vary with the type of vegetation community. Consequently, the type of vegetation community adjoining dry rainforest patches may indicate both the past likely intensity and frequency of fire events and the potential likelihood or proneness of the patches to fires in the future. As stated previously, the vegetation communities adjoining rainforest dry out more rapidly than the rainforest and carry fire much more effectively and frequently. These fires can enter rainforest under certain conditions, but more often they result in scorching and mortality of the rainforest margin to varying degrees. If these events recur frequently or intensely enough, alteration to the rainforest margin structure or its geographic location will result.
6.2.2.3 Climatic and Edaphic Factors
Rainfall and edaphic factors such as geology and soils may also influence the fire-proneness of dry rainforest patches and affect their ability to regenerate after fire events. Dry rainforest patches on the drier and / or poorer sites are likely to have a more open canopy and lower stature predisposing them to drying out and hence to fire. These factors also exert considerable influence on the ability of a damaged community to regenerate, protracting their recovery period and hence increasing patch proneness to further fire.
Thus, certain intrinsic patch characteristics influence the susceptibility and proneness of rainforest patches to fire events. The likelihood that fire will come into contact with a rainforest patch, and the impact that any particular fire will have on the patch will vary and be influenced by the actual dry rainforest structural type, in addition to the various inherent (patch configuration) and key ecological factors outlined above. The severity and duration of dry seasons prior to and after fire events will also be important as will the nature and extent of any damage to the structure of
85 Chapter 6 the dry rainforest community. This latter factor will control the accumulation of fuel and the establishment of flammable `weed species within the community itself.
6.3 Specific Objectives of the Investigation
Due to the extensive nature of the study area, the overall objective of this phase of the study is to devise, implement and subsequently evaluate a low-cost, management-oriented method to assess the current fire vulnerability of the dry rainforest in the Apsley - Macleay Gorges.
The aim is to develop a management prescription that can be implemented by NPWS field personnel, utilizing extensive, low cost procedures such as remote imagery resources coupled with periodic aerial reconnaissance.
The specific objectives are twofold. The first involves describing the resource of rainforest patches both in terms of inherent characteristics (i.e., their configuration) which have a bearing on patch susceptibility to wildfire, and the key ecological characteristics which relate to patch proneness to wildfire. The second involved developing a provisional classification of rainforest patch fire vulnerability based on the fire susceptibility and proneness criteria used to assess each patch. The resulting classification aims to identify several classes of dry rainforest patch that range from low to high fire vulnerability.
Each group of rainforest patches so defined are effectively comprised of rainforest patches with similar attributes which have a bearing on both their relative fire susceptibility and fire proneness. The classification, therefore, aims to provide a basis for prioritising and targeting fire management prescriptions in the Gorges.
Detailed descriptions of the results of the investigations are reported elsewhere (Bennett and Cassells 1989). In this
86 Chapter 6 chapter, the results of the investigations are presented as a series of summary statistics and statements about the distribution and nature of the rainforest and the fire vulnerability status of the resource.
6.4 Methodology
6.4.1 Interpretation and Mapping
A broadscale methodological approach was used for the study with all data being derived from vegetation maps produced by the Armidale Office of the National Parks and Wildlife Service. These maps were compiled utilising the available black and white aerial photography of the study area which was of varying scale (i.e., ranging from 1:47,000 to 1:210,000 scale) and age (i.e., photography ranging in age from 1967 to 1975).
The total population of each vegetation community within the study area, exceeding approximately a half hectare in area, was able to be delineated by Service staff on the aerial photos and their boundaries subsequently transferred to the 16 corresponding 1:25,000 scale topographic map sheets with appropriate scale rectification. The map sheets covering the study area are listed in Appendix 6.1.
The accuracy of the vegetation boundaries on the final vegetation maps is influenced by several factors, of which the most important included: i) operator error in identifying and delineating ve g etation boundaries on aerial photographs and in the subsequent transferring of this scale-rectified data to map sheets; ii) the varying scale and age of photography affecting precise location of vegetation boundaries due to resolution problems and vegetation dynamics occurring over time; and
87 Chapter 6 iii) the inferiority of available black and white aerial photography in comparison to colour photography for accurate vegetation boundary determination.
The extent of inaccuracy is variable throughout the study area depending on the age and scale of the appropriate photo runs but overall is considered to be sufficiently minor in view of the broadscale nature of this study. Data collection is, therefore, limited to those parameters that are observable and measurable from these remote resources.
By its nature, this implies some limitations to the accuracy of the study. However, patterns delineated at this scale and detail and subsequently sam p led and tested in the field were thought to be the most efficient and satisfactory method available in view of the objectives and time constraints of the study.
6.4.2 Data Collection
Initially, the 290,000 Ha. study area was sub-divided into geographic management zones (GMZs) to facilitate the grouping of rainforest patches into zones that can be treated as distinct management units. Eight GMZs (of unequal areas) were recognised and delineated, their boundaries utilising natural features such as rivers and ridge-lines wherever possible (see Figure 6.1). Sub-division was based on largely subjective criteria, including: access; precipitation gradients; perceived fire history; and gross observable differences (at 1:100,000 scale) in rainforest patterns in terms of patch shape and size.
Rainforest patches (predominantly dry rainforest but also including small areas of subtropical, warm and cool temperate rainforest) formed the fundamental unit for analysis in this study. Accordingly, data was extracted from the vegetation maps on the total population of individual rainforest patches exceeding approximately a half hectare in area. Each rainforest patch was uniquely coded (identifying it within GMZ
88 Figure 6.1
Geographic Management Zones
75 80 85 90 95 00 05 10 15 20 25 30 35 40
20 20
15. 15
10 10
(1)5 05
95 g5
90. 90
85 85
80 80
5 75
70
55 65
60.. 60
55: 55
50 .50
45 75 30 85 90 95 00 05 10 15 20 25 30 35 Chapter 6 and map sheet) and described in terms of inherent and ecological characteristics.
The inherent characteristics measured, described the configuration of the rainforest patch and included the shape, area, perimeter and area perimeter ratio of each patch. Ecological characteristics measured included those factors affecting the distribution of the patch in the landscape, such as physiography (i.e., slope angle, elevation, topographic position and gorge type and orientation) rainfall, adjoining vegetation community and fire history.
This information, extracted from the 1:25,000 scale map sheets, was coded onto Fortran coding sheets before being entered onto the University of New England s GOULD Mainframe computer.
Where possible, variables were measured in real terms, i • e actual area, perimeter lengths, area : perimeter ratios and elevation, however, the majority were assessed according to ordinal variable classes, often arbitrarily derived.
The study encompassed the entire population of rainforest patches in the Gorges and hence detailed statistical analysis of data is unnecessary. Consequently, only descriptive statistical analysis (frequencies and crosstabulations) were undertaken on the data, utilizing the Statistical Package for the Social Sciences (SPSS x ) (Nie 1983). To agglomerate rainforest patches into groups in terms of similarity, exploratory cluster analyses using the CLUSTAN programme was attempted. However, the cluster patterns described by this programme did not produce any groupings from the very large data base that were useful for management planning purposes. Thus, the more laborious "select if" command on the SPSSX package was used to define groupings of the rainforest patches.
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Chapter 6
6.4.3 Inherent Rainforest Patch Characteristics
6.4.3.1 Area, Perimeter and Area : Perimeter Ratio
The area, perimeter length and derived area : perimeter ratios of each patch were measured using a digital planimeter on the University of New England Tektronix 4054 computer. Patch area was measured to the nearest hectare, perimeter to the nearest metre and area : perimeter ratio calculated in terms of square metre of patch area per metre of boundary.
Because of the very rugged and steep nature of the terrain of the study area, the simple plan measurements of area, perimeter and area : perimeter ratio of rainforest patches probably underestimates their true extent, particularly in the steepest areas. Consequently, all measurements are likely to represent minimum values. However, as the plan measurements essentially maintain relativities between different patches this possible underestimation is not considered to affect the usefulness of the results of the study for management purposes.
Actual measurements of patch area, perimeter and area : perimeter ratio were grouped into several classes. These groupings are listed in Table 6.1.
Table 6.1
Patch Area, Perimeter and A:P Ratio Classes
Area Perimeter Area:Perimeter Ratio (ha.) (km.) ( m2 /m) <5 <1 <20
5-20 1-5 20-50
20-100 5-10 50-100
>100 10-20 >100
>20
90 Chapter 6
6.4.3.2 Shape
A qualitative hierarchical patch shape classification was developed from observations of rainforest patch patterns delineated on 1:100,000 scale maps of the study area.
Each patch was assessed according to this classification into one of eight shape classes. The classification system is hierarchically arranged according to three levels. These are listed below: i) BLOCK / LINEAR
- Block: patch distinctly block shaped, with a compact margin relative to area;
- Linear: patch elongated or in thin strips usually along gully lines with large boundaries relative to area. ii) SIMPLE / COMPLEX
- Simple: patch predominantly (80-90%) block or linear in shape;
- Complex: patch of mixed shape, with one predominating but the other also important.
iii) BRANCHED / NON-BRANCHED
- Branched: evident branching of rainforest from main block or linear patch
- Non-branched: branching not evident from main block or linear patch.
To minimize the complexity of analysis, the eight shape classifications were grouped into four main categories. These were: Block-Simple; Block-Complex; Linear-Simple; Linear- Complex. It was thought that these two parameters of shape were sufficient for analysis, and that little definition was lost at the broadscale level with the omission of the third parameter of branched / non-branched.
91 Chapter 6
6.4.4 Ecological Characteristics of Rainforest Patches
6.4.4.1 Aspect
Each rainforest patch was assessed in terms of the predominant direction or aspect it was facing and allocated to one of the eighteen 20° aspect classes that best represented the entire unit. Patches restricted to gully lines were classified as being oriented in the direction of the gully. For analysis, the eighteen aspect classes were further grouped into two main categories of westerly (drier, 0° - 20°, 201° - 360°) and easterly (moister, 21° - 200°) aspects.
6.4.4.2 Slope
The predominant slope angle of the terrain on which each patch was positioned was measured through examination of contour spacing on the 1:25,000 scale map sheets. Logistically, only slopes up to approximately 220 could be accurately differentiated from contour spacings.
Ideally, slope angles greater than 22° should be further separated, particularly those slopes exceeding 30°, where fuel discontinuities may occur. However, limitations of the accuracy and resolution of the map sheets did not facilitate accurate and rapid assessment beyond approximately 22°. For analysis slope angle classes were grouped into three main categories. These were as follows:
i) 0-12° (low)
ii) 12-22° (moderate)
iii) >22° (high)
6.4.4.3 Elevation
The altitude or elevation of each rainforest patch was estimated in actual metres above sea level (ASL) from contours on the 1:25,000 scale topographic map sheets. Each patch was recorded in terms of its maximum elevation (the top edge of the patch), minimum elevation (the bottom edge of the patch), and
92 Chapter 6 average elevation (the average elevation of the unit as a whole).
Actual measurements of maximum, minimum and average elevation were grouped into three classes of elevation to facilitate analysis. These were from low to high as follows:
i) <400m (low)
ii) 401 - 800m (medium)
iii) >801m (high)
6.4.4.4 Topographic Position
Each rainforest patch was recorded as positioned in one of four major groups of topographic position that have particular importance in differentiating the potential fire proneness of rainforest patches. The four categories were, from least to most fire prone, as follows:
i) restricted to gully lines;
ii) gully line with side-slope extensions;
iii) side-slopes; and
iv) upper slope / ridge line.
6.4.4.5 Rainfall
Each rainforest patch was allocated to an annual average rainfall class based on the rainfall isohyet map of the study area prepared by King (1980, 19) (see Figure 3.2). These classes provide a convenient index of water availability to plant communities. However, the location of the isohyet boundaries are only very approximate and are therefore indicative rather than definitive.
6.4.4.6 Gorge Type and Orientation
The gorge within which each rainforest patch was located was classified and recorded in terms of its orientation (i.e., direction gorge facing) and width (i.e., wide or narrow).
93 Chapter 6
Gorges were considered "wide" if their width exceeded their length, and "narrow" if their length exceeded their width. Eight categories of gorge type - orientation were delineated.
6.4.4.7 Adjoining Community
Each rainforest patch was further described in terms of the vegetation community adjoining the patch on both the upslope and downslope margins. Other communities adjoining the patches from the sides were also recorded in addition to the major upslope and downslope communities.
Due to the peculiarity of some rainforest patch shapes, the classification of the downslope adjoining community was difficult. Some patches had very small downslope extensions of the patch to rivers and creeks, but the majority of the downslope edge was actually higher than these features and adjoined other vegetation communities. In all cases, therefore, the downslope community was taken as the dominant community adjoining the patch from below and may indeed extend up the sides of the patch.
Five categories of adjoining community were recorded in this study according to their perceived flammability and hence fire proneness (Greg Roberts N.P.W.S. pers. comm.). These categories were, from most to least flammable:
i) Lantana;
ii) Cleared / grassland;
iii) Eucalypt forest;
iv) Eucalypt woodland and Acacia scrub; and
v) Inert (rock, scree or river).
Whilst the broadscale assessment did not reveal any Lantana adjoining rainforest patches, field investigations did in fact locate areas of this vegetation adjoining rainforest. This variation occurred as a result of the broadscale nature of the remotely sensed resources available for the study and indicates some of the limitations of total reliance on this approach.
94 Chapter 6
6.4.4.8 Fire History
Information regarding past fire events in the gorges was obtained from the N.P.W.S. 1:100,000 scale maps of recorded fires compiled from aerial reconnaissance and landholder interviews. This data was used in conjunction with the information gained from the more comprehensive land manager fire history questionnaire survey presented in Chapter 5. Both these sources of information are subject to considerable uncertainty due to the nature of mapping fire boundaries from the air and inaccuracies associated with the recollections of precise fire boundaries from landholders memories. Consequently, rainforest patched were recorded according to the simple procedure of whether they occurred within or outside the boundaries of recorded fire events. The lack of sufficiently high-resolution aerial photographs of the study area precluded assessment of the boundary condition (as discussed in Chapter 4) of rainforest patches, which provides an indication of past fire impact.
6.4.5 Fire Vulnerability Assessment
The fire vulnerability of the rainforest patches was assessed in terms of both the susceptibility of the patch to damage should it be impacted by fire and the proneness of the patch in terms of the likelihood of it actually experiencing a fire event. Matrices of key variables of both susceptibility and proneness were subsequently combined into an overall fire vulnerability matrix. The procedures for classifying the patches in the matrices are described below.
6.4.5.1 Fire Susceptibility Matrix
As discussed in Section 6.4.1, the configuration (i.e., shape, size and area : perimeter ratio) of patches was the best available assessment of the susceptibility of patches to damage from fire events. The variable, patch shape was simplified into two classes (i.e., linear and block shape) and the
95 Chapter 6 variables, patch area and area : perimeter ratio were each subdivided into the four classes as defined in Table 6.1.
The rainforest patch fire susceptibility matrix was constructed using these three variables differentially weighted. Weightings were applied to each variable class reflecting the perceived importance of each class in terms of affecting the susceptibility of each rainforest patch to damage should a fire come into contact with it. The higher the variable class weighting the less the significance to fire susceptibility.
Essentially, therefore, patches with high indices of susceptibility are less susceptible to fire damage than those with low indices. The variable classes and associated weightings are listed in Table 6.2 below.
Table 6.2
Susceptibility Matrix Variables and Weightings
Shape (weight) Area (weight) A:P Ratio (weight) ( ha. ) ( m 2 int )
Linear (1) <5 (1) <20 (1)
Block (2) 5-20 (2) 20-50 (2)
20-100 (6) 50-100 (4)
>100 (12) >100 (6)
Linear and block shaped patches were separated because they are easily visually distinguishable from aerial photography. However, due to the subjective nature of their delineation their separation did not warrant more than a 1 : 2 weighting. Patch area was considered to be the most im p ortant single variable, with small patches thought to be particularly susceptible to fire damage and the larger patches considerably less so. The weightings applied reflect this perception. Furthermore, A:P ratio was also considered quite important,
96 Chapter 6 but less so than area, a perception again reflected in the nominated weightings.
The result of the matrix was a list of variable class combinations of the patch variables used and a numeric index of the variable class combination susceptibility. The index was derived from summing the weightings of the three variable classes making up each particular combination. Some variable class combinations were found to be non-existent in the study area and were excluded. The full listing of possible combinations is provided in Appendix 6.2.
Based on the susceptibility index, the listing of variable class combinations were subdivided into four approximately equal groups representing differential patch susceptibility to damage from fire events (i.e., indexes :6, 6-10, 11-15 and 16- 20). Group one patches were most susceptible while group four patches were least susceptible. Groupings reflected perceived differences in the likely responses of patches to fire.
6.4.5.2 Fire Proneness Matrix
The proneness of rainforest patches to fire events was thought to relate to the key ecological characteristics of patches identified in Section 6.2.2. The most significant of these were thought to be predominant aspect; predominant slope angle; predominant topographic position; and the patch s predominant downslope adjoining community. Aspect was taken as being east or west, slope angle and topographic position each according to their combined classes presented earlier, and downslope adjoining community as the four classes defined in Section 6.4.4.7.
Again differential weightings were ap p lied to each variable class reflecting the perceived importance of the variable class in effecting fire proneness characteristics of patches. The higher the weighting the less fire prone the patch variable class.
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Chapter 6
The matrix was constructed using the four ecological variables defined above and the differential weightings attached to the various classes of each parameter. The proneness variables and their allocated weightings are presented in Table 6.3.
Table 6.3
Fire Proneness Variables and Weightings
Aspect (weight) Slope Angle (weight)
West (1) >22° (1)
East (2) 12-22° (2)
<12° (3)
Downslope Adj. Comm (weight) Topo. Position (weight)
Cleared/Grassland (1) Upper Sl./Ridge (1)
Forest. (2) Low-Mid Slope (2)
Woodland/Acacia (6) Gully Extent. (4)
Inert (12) Gully Line (6)
All four of these variables were thought likely to influence the behaviour of any potential fires. The delineation of variable classes reflect perceived significant differences between the classes. The downslope adjoining community and topographic position of rainforest patches were thought to be particularly important fire proneness variables, whilst aspect and slope angle were somewhat less important. The allocated weightings reflect these perceptions of the importance of the variables.
The results of the fire proneness matrix, like the susceptibility matrix, occurred as a gradational list of combinations of variable classes with a numeric inde:;.
98 Chapter 6 reflecting the fire proneness of each combination. The full listing of possible proneness combinations are presented in Appendix 6.3. Based on the proneness index the possible variable combinations were subdivided into four fire proneness categories (i.e., <8, 8-14, 15-20, and 21-27). Group 1 patches were most prone and group 4 least prone to fire events.
6.4.5.3 Fire Vulnerability Matrix
As stated previously, the fire vulnerability of individual rainforest patches refers to the combined susceptibility and proneness of patches to fire. Some rainforest patches may be highly susceptible to fire impacts but occur in positions that are not prone to fire occurrence and vice versa. Accordingly, a matrix was constructed which produced all the possible combinations from combining the four classes of susceptibility with the four classes of proneness similarly weighted. The variables and weightings are summarised in Table 6.4.
Table 6.4
Vulnerability Variables and Weightings
Fire Susceptibility (weight) Fire Proneness (weight)
Extreme (1) Extreme (1)
High (2) High (2)
Moderate ( 3 ) Moderate ( 3 )
Low (4) Low (4)
The resulting vulnerability matrix listed the possible combinations of patch susceptibility and proneness to fire and a numeric index of each combination s fire vulnerability. The full listing of possible vulnerability combinations is presented in Appendix 6.4.
99 Chapter 6
The vulnerability indexes were subsequently grouped into four classes of fire vulnerability (i.e., indices <4, 4, 5-6, and 7- 8). The entire resource of rainforest patches was assessed by this class index and classified according to overall fire vulnerability.
6.5 Results and Discussion
6.5.1 Inherent Rainforest Patch Characteristics
Within the 290,000 ha. study area, there exists some 735 discrete patches or pockets of rainforest vegetation each exceeding approximately half hectare in plan area. As was described by King (1980, 39), some rainforest species in the Gorges occur as isolated individuals or in very small groups (i.e., less than half hectare), too small to be mapped from aerial photography and hence not included in this analysis. However, the exclusion of this very small aerial component should not substantially affect this assessment of the overall dry rainforest resource in the study area.
Collectively the rainforest patches cover approximately 18,430 ha. or some 6.4% of the study area. However, due to the steeply sloping nature of much of the terrain in the Apsley - Macleay Gorges, this measure of the plan areas of rainforest patches probably underestimates the true aerial extent of this vegetation type in the Gorges.
Three of the 735 rainforest patches identified occurred partially outside the study area and hence were excluded from analysis. Of the 732 patches assessed, patch size ranged from less than 1 ha. through to some 1,020 ha. in area. The mean patch size was approximately 25.3 ±66.5 ha., while the median size was only some 7 ha. The distribution of rainforest patches according to size was negatively skewed and leptokurtic
Standard Deviation
100 Chapter 6 i.e., distribution is skewed towards the smaller values and is more clustered / peaked than a normal distribution.
The length of rainforest patch perimeters were also markedly variable ranging from a minimum of just 40 metres through to a maximum length of some 83,000m. The mean patch perimeter• length was approximately 3,600 + 6,440m while the median len,ah was some 1,730m. Distribution of patches according to perimeter length was also negatively skewed and leptokurtic. As with the plan measurement of patch areas, the measured extent of patch perimeters probably underestimates their true extent to some degree.
The ratio of rainforest patch area (in square metres (m 2 ) ) to patch perimeter (in metres (m)) was again quite variable ranging from less than 1 m 2 /m through to some 281 m2 /m. The mean patch area : perimeter (A:P) ratio was approximately 50 35 m2 /m while the median was only some 39 m2 /m. Again, the distribution of patches according to A:P ratio was negatively skewed and leptokurtic.
Large A:P ratios indicate those patches that have a relatively large area with respect to their perimeter length whilst those with low ratios indicate the converse. Rainforest patches with high ratios tend to be large and compact, with less convoluted boundaries than those patches with low ratios. Hence, the larger the patch and the more circular the shape of it s boundary, the higher the A:P ratio.
6.5.1.1 Rainforest Patch Area Categorisation
The proportions of the rainforest resource categorised into four patch area classes are summarised in Figure 6.2. The mean perimeter lengths and A:P ratio of patches within each of these patch area categories are presented in Table 6.5. This Table illustrates that mean area : perimeter ratio of patches does not increase in proportion with increasing patch area.
It is immediately obvious that the majority of the patches of rainforest in the Gorges are small, with almost 76% of patches
101 Fig. 6. 2 Patch Area Classes
100 100
90 ,■ Total Patches 90
, 80 4 Total Area 80
70 70
60 60 c 0 •■• 50 50
40
30 30
20 20
10 10
i 0 <5 20- 100 Area Class (Ha.) Chapter 6 covering 20 ha. or less in area. However, in terms of the proportion of the total area of rainforest, most (81%) is contained within those patches exceeding 20 ha. in size. In particular, patches exceeding 100 ha. in area account for only some 6% of patches but nearly 51% of the total area of rainforest.
Thus, the rainforest resource within the Gorges consists of numerous small and very few large patches. Collectively the small patches cover a relatively small area of forest while the few large patches account for the bulk of the area.
Table 6.5
Patch Mean Perimeter and A:P Ratio By Area Class
Area Class Mean Perimeter Mean A:P Ratio (ha.) (km) ( m2 im )
<5 0.9 ±0.4 29.7 ±16.0
5-20 2.5 ±1.1 47.7 116.1
20-100 6.5 l3.4 72.1 1-31.1
>100 20.8 ±17.2 129.7 163.1
6.5.1.2 Rainforest Patch Perimeter Categorisation
Figure 6.3 illustrates the proportions of the rainforest resource occurring within five defined perimeter length classes.
Some 81% of patches have perimeters of 5 km or less in length but when combined cover less than 28% of the existing total area of rainforest. The remaining 19% of patches have perimeters exceeding 5 km in length but these patches account for approximately 72% of the area of rainforest in the Gorges.
102 Fig. 6.3 Patch Perimeter Classes
100 100
90 - Total Patches — 90 80 - Total Area - BO
70 1- 70
60 - - 60
50 - - 50
40 - - 4-0
30 30
20 - 20
10 10
<1 1-5 5-10 10-20 Patch Perimeter Class (km) Chapter 6
6.5.1.3 Rainforest Patch Area : Perimeter Ratio Categorisation
The proportions of the rainforest resource occurring within the four defined patch area : perimeter ratio classes (i.e., patches with A:P ratios are presented in Figure 6.4. Table 6.6 summarises the mean patch area and perimeters within each of these classes.
Very few patches have very small (i.e., <20 m 2 /m) or very large (i.e., >100 m 2 /m) A:P ratios. . The largest proportion of patches (almost 60%), have A:P ratios between 20 - 50 m2/m while a further 27% have A:P ratios between 50 - 100 m2/m. Obviously, the patches with the larger ratios account for the majority of the area of rainforest in the Gorges. Indeed, although only 6% of patches have A:P ratios exceeding 100 m2/m, they collectively cover some 38% of the total area of rainforest while the 60% of patches with ratios between 20 - 50 m2/m cover only 20% of the total area of rainforest.
Table 6.6
Mean Patch Area and Perimeter By A:P Ratio Class
A:P Ratio Class Mean Area Mean Perimeter ( m2 /m) (ha.) ( km )
<20 1.4 20.9 0.8 20.5
20-50 3.6 + 13.4 2.4 3.4
50-100 38.0 158.4 5.5 28.5
>100 153.3 1184.1 9.9 112.7
6.5.1.4 Rainforest Patch Shape Classification
Figure 6.5 illustrates the proportions of the rainforest resource that were categorised into each shape class and Table
103 Fig. 6.4 Patch Area : Perimeter Ratio Classes
100 100
= 90 Total Patches 90
80 Total Area 80
70 70
60 60 c 0 =L_ 550 50 0 a o 40 40 L_ a_ 30 30
20 20
10 10
to <20 1 20-50 50- >100 100 Area : Perimeter Ratio Class (m /m)
104 Fig. 6.5 Patch Shape Classes
100 100
,,,....■■/ 90 Total Patches — 90 Total Area 80 A — 80
70 70 ...; 60 — 60 c 0 50 50 L 0 Q. 0 40 40 L 0 30 — 30
20 — 20
10 — 10
i 0 SL CL CB SB Patch Shape Class Chapter 6
6.7 presents shape class means for patch area, perimeter, and A:P ratio.
The majority of patches (52%) are Simple-Linear (SL) shape. Simple-Block (SB) shape patches are also important accounting for a further 29% of patches, whilst relatively few patches were classified as Complex-Block (CB) or Complex-Linear (CL) shape (accounting for 11% and 7% of patches respectively).
However, in terms of the total area of rainforest, CB shaped patches account for the largest single proportion, covering some 7,330 ha. or 40% of the rainforest area, whilst the remaining extent of the resource is divided between the other categories of shape in approximately equal proportions.
Table 6.7
Patch Shape Class Mean Values
Shape Class Area Perimeter A:P Ratio (ha.) (km) ( m2 /m )
SL 11.0 117 2.7 ±3 35.3 119
CL 71.6 195 11.8 ±14 58.0 !16
CB 90.5 ±151 8.4 1.11 86.4 141
SB 15.8 ±38 1.6 t2 59.0 143
Thus, it is readily apparent from Figure 6.5 that although CL and CB shape patches are relatively few in number they are generally considerably larger in size than the other patch shapes and hence account for the majority of the area of rainforest in the Gorges. Combined, only 17% of patches are CL or CB in shape but these patches cover almost 10,840 ha. or 59% of the total area of rainforest in the Gorges. Conversely, the more numerous but generally smaller sized SL and SB shape patches account for a proportionally much smaller area of rainforest.
105 Chapter 6
This suggests, and it is confirmed in Table 6.7, that the patch shape categories have a differential mean patch size and associated with this a differential mean perimeter length. CL and CB shape patches had both considerably larger mean patch areas than either SL or SB shaped patches and this is also reflected to some degree in their mean perimeter length.
Figure 6.6 illustrates the break-up of patches within each shape class by the patch area classes discussed previously. It is clear from Figure 6.6 that the majority of rainforest patches that are 5 ha. or less in area are SL or SB in shape. Those patches between 5 and 20 ha. in area occur relatively equally in all shape classes. In contrast, patches between 20 to 100 ha. in area, and particularly those greater than 100 ha. are predominantly CL or CB in shape.
Patch mean A:P ratios reflect both the mean area and perimeter of the patches within each shape class. CB shape patches, with their large mean area associated with only a relatively moderate mean perimeter length have a large mean patch A:P ratio. SL shape patches, on the other hand, had a particularly low A:P ratio resulting from their generally small size in relation to their perimeter lengths. As evident in Table 6.7, CL and SB shape patches have reasonably similar average A:P ratios despite quite different mean patch areas. This results from the proportionally much greater perimeter lengths associated with the CL shape patches and also the higher standard deviation of the SB shape patches size.
Figure 6.7 further summarises the trends of A:P ratio associated with each patch shape class. SL patches have low A:P ratios generally less than 50 m 2 /m, CL and SB patches are variable but are predominantly between 20 and 100 m 2 /m whilst CB patches generally exceed 50 m2/m.
Thus, in summary, SL and SB shape patches are numerous but predominantly small in area. However, the generally shorter mean perimeter lengths of the SB shape patches ensure that these patches have proportionally considerably larger A:P ratios than the SL shape patches as illustrated in Figure 6.7
106 Fig. 6.6 Patch Shape By Area Classes
100
90 Patch Shape Class
SL Patches 80 CL Patches
70 CB Patches SB Patches 60 0 50 0 0 40 a_ 30
20
10
5-20 20-100 >100 Patch Area Class (Ha.)
107 Fig. 6.7 Patch Shape By A:P Ratio Classes
100 100
90 Patch Shape Class 90
SL Patches 80 , 80 CL Patches
70 CB Patches i 70 El SB Patches 60 60 c L. 50 50 0 o_ --....-4 Lo 40 40 a_ 30 30
20 / 20
10 10 ,7 , _A , _____ty7,/, 0 <20 20-50 50-100 >100 Patch Area : Perimeter Ratio Class (m /m) Chapter 6 above. In contrast, CB and CL shape patches are relatively few and generally larger in area and hence account for the majority of the total area of rainforest in the Gorges. The generally longer perimeters of the CL shape patches result in their relatively low A:P ratios, whilst the CB shape patches have the highest A:P ratios.
6.5.2 Rainforest Patch Ecological Characteristics
6.5.2.1 Patch Rainfall Categorisation
Average annual rainfall varies markedly over the study area and unequal proportions of the area lie within the different annual rainfall isohyet classes delineated within the Gorges (see Figure 3.2).
The frequency of patches and proportion of the total area of rainforest falling within the six rainfall classes identified and delineated within the Gorges are summarised in Figure 6.S.
Rainforest patch distribution within each of the average annual rainfall isohyet classes largely reflects the proportions of the study area falling within each isohyet class with the exception of the 800-900mm and 1,100-1,200mm classes. The former class has proportionally less rainforest than its area would suggest (i.e., covers some 45% of the study area but accounts for only 25% of the rainforest area) whilst the latter has proportionally more (i.e., covers only 4% of the study area but accounts for 13% of the rainforest resource). However, the apparent under-representation of rainforest in the 800 - 900mm isohyet class, which occurs mainly in the west of the study area, may result from the steeper, narrower gorge-type that appears to dominate the landscape rather than the direct influence of rainfall itself.
Thus, the distribution of dry rainforest patches does riot appear to be greatly influenced by rainfall gradients existing within the study area. Rainforest is distributed across the full range of rainfall isohyets including the lowest classes,
108 Fig. 6.8 Patch Annual Rainfall lsohyet Classes
60
Total Patches _ 50 M Total Area
40
r 10
0 / / 800- 900- 1000- 1100- >1200 900 1000 1100 1200 Rainfall lsohyet Class (mm) Chapter 6 in proportions approximately parallelling the respective areas of each isohyet class. The occurrence of mists in the drier autumn and winter months (May - August) may be an important supplement to moisture availability for those rainforests that are located in the lower rainfall areas of the gorges. Furthermore, ground water movement through the heavily jointed rocks in the study area may also provide supplementary water to plant communities in the drier areas of the gorges.
6.5.2.2 Patch Physiographic Position Classification
6.5.2.2.1 Elevation
Rainforest patch elevation or altitude was measured in three ways. Maximum elevation refers to the top-most edge of patches, minimum elevation refers to the bottom-most edge of patches, and average elevation refers to the height position at which most of the patch is located.
The maximum elevation of rainforest patches ranged from as low as 200m through to some 1,400m while the mean value was approximately 820 + 170m, and the median value was 860m.
The minimum elevation of rainforest patches ranged from only 90m through to almost 1,100m and averaged approximately 540 200m, with a median value of some 500m.
The average elevation of rainforest patches ranged from 180m through to 1,100m and had a mean of approximately 670 165m, and a median of some 680m. Figures 6.9, 6.10, and 6.11 summarise the frequency of patches and proportion of the total rainforest resource occurring within the three defined altitude categories (i.e., patches falling within <400, 401-800, >800m altitudinal classes) for maximum, minimum and average rainforest patch altitude positions respectively.
The distribution of the rainforest resource is markedly positively skewed in terms of maximum elevation, moderately negatively skewed in terms of minimum elevation and relatively- normally distributed with respect to average elevation. The
109 Fig. 6,9 Patch Maximum Altitude Classes
100 100
90 Total Patches — 90
80 --- Total Area — 80
70 — 70 ..--, 60 — 60 c 0 -4-•..... 50 — 50 1,... 0 a o 40 — 40 a_ 30 — 30
20 — 20 / 10 — 10
A i 0 i <400 401 - 800 Altitude Class (m)
110 Fig.6 10 Patch Minimum Altitude Classes
100 100
90 Total Patches 90
80 Total Area 80
70 - 70 ri-N7; 60 60 0 4-L- 50 50 0 0 40 - 40 a_ 30 - 30
20 20
10 - 10
0 401 - >801 800 Altitude Class (m)
111 Fig. 6.11 Patch Average Altitude Classes
100
90 —11 Total Patches
80 2 Total Area
70
60 C 0 L 50 0 a 0 40 L._ a_ 30
20
10
77./7/7, <400 401 - >801 800 Altifude Class (m) Chapter 6 maximum or top-edge of rainforest patches occur predominantly (i.e., 60% of patches covering 80% of the rainforest area) at elevations exceeding 800m. The minimum or bottom edge of patches, in terms of the area of rainforest, is evenly split between elevations less than 400m and those between 400 - 800m.
Ey far the majority of the resource is situated in the 400 - 800m average altitude class, where some 75% of patches covering 84% of the rainforest area occurs. Of the remaining area of rainforest in this average altitude range class, less than 2% occurs below 400m or less, whilst only some 14% exceeds 800m elevation.
Appendix 3.1 indicates that some 13% of the study area is located below 400m, 38% is located between 400 and 800m, whilst the balance, some 49% exceeds 800m in elevation. Thus, in terms of the land area within each of these elevation classes, there exists proportionally a considerably greater area of rainforest patches in the 400 to 800m elevation range. Furthermore, those areas of the Gorges that are less than 400m elevation and particularly those areas that exceed 800m are proportionally considerably under represented in terms of rainforest distribution.
This suggests that rainforest distribution in the Gorges may be affected by altitude, with distribution particularly favouring intermediate elevations i.e., those between 400 and 800m altitude. The lower temperatures and number of frost-free clays, increased exposure and hence less mesic conditions that may be associated with the higher elevations may partly explain the relative scarcity of rainforest distribution in those areas of the Gorges exceeding 800m elevation. Furthermore, the very small proportion of rainforest occurring below 400m may result from generally higher temperatures and the probable greater levels of human activity (e.g., fire and clearing) associated with the seasonal grazing operations undertaken in the Gorges.
112 Chapter 6
6.5.2.2.2 Slope
The frequency of rainforest patches and the proportion of the total area of rainforest falling within six defined slope categories are summarised in Figure 6.12.
The vast majority of the rainforest resource in the Gorges is situated on slopes that are predominantly in excess of 12°. The greatest single proportion occurs on 18-22° slopes, where approximately 43% of patches and 55% of the area of forest is located. A further 22% of patches but only an additional 13% of the area of the resource occur on slopes greater than 29 . Combined, therefore, slopes exceeding 12° account for almost 91% of patches and some 88% of the total area of rainforest. Whilst slopes less than 12° account for only a very small proportion of the resource.
When compared with areas of land covered by each slope class as presented in Appendix 3.1, it appears that the lowest (i.e., <9°) and highest (i.e., >2 9 °) slope classes are considerably under-represented both in terms of the number of rainforest patches and particularly rainforest area in each class. It also appears that patches on the very steep slopes are generally small in size. Combined, these two slope classes cover almost 70% of the study area whilst accounting for only some 25% of patches and 14% of the total area of rainforest. Furthermore, the 18 - 99 slope class accounts for a disproportionately high percentage of the rainforest resource.
Thus, the data suggests that rainforest distribution is favoured by intermediate slopes, particularly the two classes between 12° and 22° , and is restricted on the gentle and very steep slopes in the study area. The small amount of rainforest located on gentle slopes may result because much of this slope class actually may represent the segments of tableland country within the boundaries of the study area, areas subject to greater temperature and frost limitations. Also, slope instability or absence of suitable substrate may explain the restricted distribution and small patch size of rainforest on the very steep slopes. However, in this latter situation fire
113 Fig. 612 Patch Slope Classes
100 100
,•■•••••• 90 Total Patches — 90 80 – Total Area – 80
70 – 70
60 – 60 0 50 – 50 0 a_ 40 – 40 a_ 30 – 30
20 – 20
10 – 10
0 3-9 i 9-12 12-18 18-22 >22 Patch Slope Class (degrees) Chapter 6 may also be playing a role, as the rate of fire spread increases with slope angle.
6.5.2.2.3 Aspect
Figure 6.13 summarises the proportions of the rainforest, resource positioned within the eighteen 20° aspect classes.
As discussed in Section 6.2.2.1, easterly aspects (i.e., between 21° and 200°) should be more mesic than westerly aspects as they receive less direct insolation and also face the prevailing moisture laden winds that occur in Summer and Autumn. As such, easterly aspects should tend to support more rainforest vegetation. This was quite evident in Figure 6.13 where the majority of the resource, almost 63% of patches covering some 66% of the total area of rainforest occur on easterly aspects. However, Appendix 3.1 indicates that approximately 61% of the study area is comprised of easterly aspects. Consequently there does not appear to be a significant preferential distribution of rainforest for these aspects.
Despite this, analysis of aspect preference by patch size classes highlighted the trend for larger patches (i.e., >20 ha.) to favour easterly aspects, whilst the numerous small patches (particularly those less than 5 ha.) had no clear relationship with any particular aspect. The majority of these smaller patches are almost totally restricted to gully lines which may negate the influence of aspect.
The proportion of patches and the area of rainforest occurring within each aspect class largely parallel each other except in the case of the 0-20° and 80-100° aspect classes where the proportion of patches is considerably exceeded by the area of rainforest. In these cases individual patches are quite large and hence account for a proportionally substantial portion of the area of rainforest.
There appears to be no significant overall preferential distribution of rainforest towards easterly aspects. However,
114 Fig. 6.33 . Patch Aspects
20 20
19 19
18 - 18
17 Total Patches 17
16 16 Total Area 15 .■■•■■■ 15
14 -114
13 -+ 13
12 12
11 - 11 0 10
0 9 0_ 0 8 S._ CL
5
3
2
1
0 f 21 41 1 61 T 81 1 01 121 141 61 81 01 r 221 41 261 281 301 r 321 341 -20 -40 -60 -80 -100 -120 -140 -160 -180 -200 -220 -240 -260 -280 -300 -320 -340 -360 Aspect Class (degrees) Chapter 6 this may simply reflect the numerous small, linear patches that occur along gully water courses not strongly correlated with aspect. This factor will be assessed further on.
6.5.2.2.4 Topographic Position
The frequency of patches and the proportion of the area of rainforest occurring in the four physiographic position categories (i.e., patches positioned on upper- slope/ridge (us/rl), side-slope (ss), gully-line with side-slope extensions (g1 ex), or restricted to gully-line physiographic position (rgl)) are summarised in Figure 6.14.
Approximately 624 or almost 86% of all the rainforest patches in the Gorges are centred on gully-lines, which largely parallels the findings of King (1980, 86). This is comprised of nearly 50% of patches which were entirely restricted to gully-lines, while the remaining 36% had varying extents of side-slope extension. Collectively, these patches cover .just over 90% of the total area of rainforest in the Gorges. However, despite the greater number of patches totally restricted to gully lines (50%), they collectively cover only some 21% of the total area of rainforest. By way of comparison, the less numerous patches that have side-slope extensions cover almost 70% of the rainforest area.
The numerous patches totally restricted to gully-lines are individually quite small, averaging only some 11 t21Ha. in area. By way of contrast, those patches with sideslope extensions are much larger, with these patches averaging approximately 48 183Ha.
Less than 15% of patches and 10% of the rainforest area occurs on slopes or ridges with no connections to evident gully-lines. In particular, those patches that are positioned on lower to mid slopes are individually small and hence collectively cover only a very small area of the rainforest resource.
Obviously, rainforest distribution favours topographic positions centred on gully-lines where conditions should be
115 Fig. 6.14 Patch Topographic Position
100 100
90 — 7 Total Patches 90 , Total Area 80 — 80
70 — 70
60 60 c _ 0 50 — 50 o- a_ 40 40 oL a_ - 30 — 30
20 — 20
10 r---- 10
1,777,71. z 0 US/RL SS I GL EX RGL Physiographic Position Chapter 6 more mesic and fire proneness may be less. Many patches are indeed totally restricted to gully lines and may actually reflect limits to rainforest distribution such as moisture, and edaphic factors and / or past and current fire influences.
In many cases, rainforest may be limited to gully-lines which act as fire refugia. These positions are also more mesic and tend to accumulate higher levels of plant nutrients. Hence they may permit greater rainforest structural development. Gully lines also tend to experience more limited fire impacts because fires must approach them from potentially less damaging upslope positions. Fires which travel downslope burn less intensely and hence have less impacts on adjoining downslope vegetation communities.
A lesser number of patches but the vast majority of the rainforest area occurs in gully with side-slope extension positions. Here again, the rainforest is centred or connected to gully-lines but have been able to extend up the adjacent slopes to varying extents. Perhaps in these cases other environmental variables (e.g., soil) may not be limiting. Indeed, preliminary field investigations suggest that soils are comparatively uniform with no evident differences existing between soils under rainforest and those under other vegetation communities. It appears likely, therefore, that in these particular locations fire events have been less frequent and / or less intense, permitting rainforest to remain or to be slowly retreating. It is also possible in some of these areas that the rainforest is able to expand upslope from the gully- lines due to changing fire regimes.
The fact that rainforest can and does occur, seemingly totally unconnected with gully-lines, indicates that the community can exist in perceived less mesic and less fire-protected environments. Indeed, as stated previously, almost 10% of the total area of rainforest occurs on mid-slope - ridgelirie positions in the study area. However, the very small patches that occur as unconnected isolates on the lower-slope to mid- slope positions may reflect their very fire prone position,
116 Chapter 6 with fire influences possible from below as well as above the community.
6.5.2.2.5 Gorge Type and Orientation
The proportions of the resource located within the eight categories of gorge type and orientation, as defined in Section 6.4.4.6 are summarised in Figure 6.15.
The bulk of the resource occurs in those gorge types defined as narrow, particularly those oriented predominantly south. Indeed, this gorge type (NS) accounts for some 52% of patches and 44% of the area of rainforest. Further, Narrow-North (NN) gorges accounted for a further 19% of both patches and area of rainforest. Together, the narrow type gorges account for 91% of patches and 90% of the total area of rainforest. Of the wide type gorges, the greatest proportion of the rainforest is situated in those oriented east or south, accounting for a further 6% and 4% of the area respectively.
The predominance of patches in the narrow north and south type gorges may simply reflect the abundance of this particular gorge type in the study area, rather than any specific locational advantage of these positions. The available data does not readily permit assessment of this factor. However, theoretically, the narrow gorges may also provide more mesic conditions due to shading and some protection from prevailing weather. They may also have a reduced number of potential fire ignition points, as grazing practices are largely restricted to the broader gorges where river terraces have developed.
6.5.2.3 Adjoining Vegetation Communities
The vegetation communities adjoining the rainforest patches were separated into those adjoining from upslope of the patch and those adjoining from downslope. The five identified adjoining communities were, from most to least flammable: Lantana; cleared/grass; forest; woodland/Acacia scrub; and inert material such as rock/scree or river.
117 Fig. 6.15 Patch Gorge Type/Orientation
100 100
90 Total Patches 90
80 Total Area 80
70 — 70
60 — 60 0 50 50 0 0 40 40 a_ 30 30
20 20
10 10
0 NW NN NS WE WW WN WS Gorge Type/Orientation Class
118 Fig. 6.16 Patch Downslope Adjoining Community 100 100
Il.....■•■• 90 — Total Patches 90
80 Total Area — 80 70 70
60 — 60 c 0 :7-- 50 —j 50 0 oca. 40 40 1._ a_ H 30 --- 30 20 — 20 / 10 -111 10
/ / A 0 Cleared Forest Woodland Inert Downslope Adjoining Community
119 Chapter 6
The frequency of patches and the proportion of the area of rainforest that have the defined categories of downslope adjoining community are summarised in Figure 6.16. Figure 6.17 also summarises the frequency of patches and the proportion of the area of rainforest according to the vegetation community adjoining the upslope margin of rainforest patches.
Eucalypt forest is the major vegetation community adjoining rainforest patches on both the downslope and particularly the upslope margins of rainforest patches. In this latter position, some 75% of patches covering almost 87% of the rainforest area adjoin Eucalypt forest communities. Woodland/Acacia Scrub is the next most important community, being particularly common on the downslope margins of patches, where some 41% of both patches and area of rainforest adjoin this vegetation type. In contrast only approximately 22% of patches accounting for 12% of the rainforest area adjoin this community on the upslope margins of rainforest patches.
Very little cleared/grassed land or inert material adjoins the rainforest patches from either upslope or downslope. Indeed, collectively only some 6% of patches covering 4% of the area of rainforest adjoin these communities from downslope positions, while still less are surrounded by these communities from upslope positions.
As evident in Appendix 3.3, Eucalypt forest forms the predominant vegetation type in the study area, covering almost 60% of the total area. Woodland/Acacia is also an important community as is the cleared/grassland community. However, this latter community may largely be associated with the portions of tableland country that occur within the boundaries of the study area, where rainforest does not occur. This may partly explain the relative discrepancy in terms of the proportion of rainforest adjoining this community with the proportion of the study area that is cleared/grassland.
Thus, the relative dominance and proportions of forest and woodland/Acacia scrub vegetation communities adjoining rainforest is to be expected. However, the differential
120 Fig. 6,17 Patch Upslope Adjoining Community
1 00 100
90 Total Patches 90 r 80 4 Total Area 80
70 70
60 60 c 0 47- 50 L 50 0 a o 40 40 L... a_ 30 30
20 20
10 10
/ 0 Cleared Forest Woodland Inert 1 Upslope Adjoining Community Chapter 6 representation of the Eucalypt forest community adjoining rainforest from upslope compared to downslope is not so easily explained. In terms of fire proneness of rainforest patches, downslope adjoining communities are considerably more important than upslope communities due to the influence of slope on fire behaviour. The lesser proportion of rainforest patches adjoining the perceived more flammable forest communities on their downslope margins may reflect the greater intensity of fire that may occur in those Eucalypt forest communities. Thus, given the right conditions of topography etc and a fire ignition source, rainforest patches may be actively retreating or totally destroyed where they occur upslope of this community type.
Alternatively, woodland/Acacia scrub may have replaced much of the Eucalypt forest downslope of rainforest patches under the influence of fire, whilst the fire-buffering nature of the patches have permitted the Eucalypt forest to persist above the patches.
6.5.2.4 Fire History
Of the 732 patches assessed some 218 or almost 30% were located within the boundaries of one or more recorded fire events dating back to about the early 1960s. Collectively these patches cover some 9,501 ha. and account for approximately 52% of the entire area of rainforest still existing in the Gorges.
Thus, both human-related and natural fire ignition sources obviously exist in the study area. In recent times, with the increased interest in the area by the NPWS, many known fires have been recorded in areas of rainforest occurrence. Hence, it is now more certain that fires may have impacted on the community to varying extents in this time. Indeed, the survey results presented in Chapter 5 indicated that one quarter of the land managers in the study area perceived that fire was impacting on the rainforest patches. However, the history of fire occurrence in the area is still only imprecisely known and
121 Chapter 6 it may have had significant undocumented impacts on the resource over time.
6.5.3 Fire Susceptibility, Proneness and Vulnerability of Rainforest Patches
The vulnerability of rainforest patches in the Apsley - Llacleay Gorges to fire is a function of the fire susceptibility and fire proneness of each patch.
To reiterate the concepts outlined in Section 6.4, high fire susceptibility connotes greater likely patch damage from fire impact and is governed by the size, shape and area : perimeter ratio of patches. The higher the patch fire proneness, the greater the likelihood of a fire actually impacting the patch and the more intense the fire is likely to be. Proneness is largely governed by the predominant aspect, topographic position, slope angle and adjoining vegetation community of patches.
Combined, therefore, these two parameters determine the fire vulnerability of individual rainforest patches. That is, both the significance of fire impact and the actual likelihood of fire impact occurring.
As discussed in Section 6.4.5, an index was developed for each of patch fire susceptibility, fire proneness and fire vulnerability. The results of these matrices are presented below.
6.5.3.1 Fire Susceptibility Index
The fire susceptibility matrix utilizing key, differentially weighted, rainforest patch inherent characteristics produced a numeric index of fire susceptibility for each combination of variables. The index ranged from 3 to 20 reflecting decreasing fire susceptibility of possible variable-class combinations. The full listing of the possible fire susceptibility index parameter combinations are presented in Appendix 6.2. Several
122 Chapter 6
impossible combinations were excluded, and the listing subdivided into four equal susceptibility classes based on the derived susceptibility indices. Fire susceptibility classes were allocated as follows:
1. extreme (susceptibility index 1 to 5);
2. high (susceptibility index 6 to 10);
3. moderate (susceptibility index 11 to 15); and
4. low (susceptibility index 15 to 20).
The number of rainforest patches and area of rainforest within each of the four fire susceptibility classes are summarised in Table 6.8.
Table 6.8
Fire Susceptibility Index
Fire Susceptibility Patches Rainforest Area (ha.)
1. Extreme 425 (58%) 2,102 (11%)
High 162 (22%) 2,575 (14%)
3. Moderate 101 (14%) 4,695 (26%)
4. Low 40 (6%) 9,040 (49%)
The results listed in Table 6.8 were riot unexpected in view of the description of the inherent characteristics of rainforest patches presented previously. Many patches are extremely susceptible to fire impacts should fire events come into contact with their boundaries. However, the total area of rainforest contained within these extremely fire susceptible patches is relatively low. By contrast, very few rainforest patches have a low fire susceptibility, but these few patches are individually very large and cover almost half of the entire area of rainforest in the gorges.
123 Chapter 6
6.5.3.2 Fire Proneness Index
The results of the fire proneness matrix, which utilized key, differentially weighted, rainforest patch ecological characteristics, occurred as a gradational _list of combinations of proneness variable-classes with a numeric index reflecting the fire proneness of each combination. The full listing of the possible fire proneness parameter combinations are presented in Appendix 6.3. Several impossible combinations were excluded and the listing subdivided into four equal proneness classes based on the derived proneness index. Fire proneness classes were allocated into four approximately equal classes as follows:
1. extreme (proneness index 1 to 7);
2. high (proneness index 8 to 14);
3. moderate (proneness index 15 to 20); and
4. low (proneness index 21 to 27).
The number of rainforest patches and area of rainforest within each of the four fire proneness classes are summarised in Table 6.9.
Table 6.9
Fire Poneness Index
Fire Proneness Patches Rainforest Area (ha.)
1. Extreme 41 (6%) 425 (2%)
2. High 312 (43%) 13,902 (75%)
3. Moderate 360 (49%) 3,706 (20%)
I. Low 15 (2%) 398 (2%)
By far the majority of rainforest patches occur in positions that were classified as moderately or highly prone to fire
124 Chapter 6 events. That is, those patches are perceived as moderately to highly likely to be subject to fire events due to their position in the landscape and nature of adjoining community. Further, the majority, just over three quarters of the total area of rainforest, is highly prone to fire.
In contrast, only very few rainforest patches were classified as extremely prone or low prone to fire. These few patches also only cover a small area of the total area of rainforest in the gorges.
6.5.3.3 Fire Vulnerability Index
The results of the fire vulnerability matrix, which combined the four classes of patch fire susceptibility (implicitly reflecting patch shape, size, and area : perimeter ratio) and the four classes of patch fire proneness (reflecting patch aspect, slope angle, downslope adjoining vegetation community and topographic position), was a ranked numeric index of the possible combinations of these two parameter classes. The index associated with each combination reflected the perceived fire vulnerability of the combination. The full listing of combinations is presented in Appendix 6.4.
The listing was subdivided on the bases of the derived vulnerability index into four classes of fire vulnerability reflecting perceived differences in the likely vulnerability of patches. The four classes were allocated as follows:
1. Extreme (vulnerability index 2 to 3)
2. High (vulnerability index 4)
3. Moderate (vulnerability index 5 to 6)
4. Low (vulnerability index 7 to 8)
The number of rainforest patches and area of rainforest within each of the four fire vulnerability classes are summarised in Table 6.10. Appendix 6.5 presents a list of each numerically coded rainforest patch with its associated fire vulnerability index identified by the geographic management zone and 1:25,000
125 Chapter 6 scale mapsheet of its occurrence. These 16 coded mapsheets are held by the Armidale Office of the National Parks and Wildlife Service, in conjunction with the report "Characteristics and Fire Vulnerability Assessment of the Dry Rainforest in the Apsley - Macleay Gorges" (Bennett and Cassells 1989)..
Table 6.10
Fire Vulnerability Index
Fire Vulnerability Patches Rainforest Area (ha.) 1. Extreme 140 (19%) 687 (4%)
2. High 386 (53%) 3,112 (17%)
3. Moderate 202 (28%) 13,806 (76%)
4. Low 4 (0.5%) 631 (4%)
A majority of the rainforest patches in the Apsley - Macleay Gorges were classified as being high or extremely vulnerable to fire influences. In essence, this suggests that many of the rainforest patches are both susceptible to damage from fire impact and are in positions that are likely to experience fire events in the future, providing a fire ignition source exists (either from natural sources or human activity). Indeed, in excess of 70% of the rainforest patches have high or extreme vulnerability to fire. However, despite the numerous patches in this rather parlous situation, collectively they only cover approximately 21% of the area of rainforest in the Gorges. The majority of the area of rainforest patches (almost 80%) is in a better situation, being classified as either moderate or low vulnerability.
The proportion of rainforest patches classified according to fire vulnerability are summarised in respect to the eight defined geographic management zones (GMZs) in Table 6.11.
126 Chapter 6
Appendix 6.6 presents the proportions of the study area contained within each of the GMZs.
Table 6.11
Fire Vulnerability of Patches According to GMZ
GMZ Patches Area Proportion of Patches in Each Vulnerability Class
Ext High Mod Low
(%) (%) (%) (%) (%) (%)
1 28 15 26 56 19 0
2 25 17 22 50 27 0.5
3 14 13 14 52 32 1
4 3 8 20 28 52 0
5 9 17 5 45 48 3
6 4 6 15 52 33 0
7! 3 2 29 48 24 0
8 14 22 14 65 21 0
The data summarised in Table 6.11 does not suggest any evident patterns of fire vulnerability of patches exists within the study area. Each vulnerability class, except for the very limited number low category, is represented in every GMZ. Marginal differences in the proportions of patch fire vulnerability classes exists between each GMZ. The most important of these apparent geographic differences in patch fire vulnerability appears to be the relatively large proportion of patches in GMZ 1, 7 and 8 with high and extreme fire vulnerability. By comparison, patches in GMZ 4 and 5 aro proportionally less vulnerable.
127 Chapter 6
6.6 Conclusion and Summary of Major Findings
6.6.1 Inherent Rainforest Patch Characteristics
Approximately 735 discrete patches of rainforest covering some 18,400 ha. occur in the Apsley - Macleay Gorges. From assessment of this total population of rainforest patches, it was found that patches are extremely variable in their area, perimeter length, and area : perimeter ratios. However, their distribution in general is negatively skewed. That is, most of the patches are relatively small and have low area : perimeter ratios.
While there are numerous rainforest patches in the Apsley - Macleay Gorges, the majority of the area of rainforest is contained within a comparatively few large patches with relatively high area : perimeter ratios. Most patches are in fact small in area and have relatively low area : perimeter ratios, they account for only a small fraction cf the total area of the rainforest in the Gorges.
The numerous, small patches are predominantly Simple-Linear or Simple-Block in shape, whilst the less numerous, larger patches more usually are Complex-Linear or Complex-Block in shape.
6.6.2 Rainforest Patch Ecological Characteristics
Average annual rainfall varies markedly over the study area, from less than 800mm to in excess of 1,200mm. Dry Rainforest patches occur over the full range of rainfall isohyets with the majority located within areas receiving less than 1,000mm per annum. However, rainfall does not appear to be greatly influencing rainforest distribution within the overall gorge system.
Dry rainforest patches occur over a wide altitudinal range in the gorges, reflecting the deeply disected and complex terrain. Patches range from a minimum altitude of some 90m through to a
128 Chapter 6 maximum of 1,400m. Altitude appears to be influencing rainforest distribution to some extent with the majority of the resource positioned between 400 and 800m elevation with the lower and higher altitudinal ranges considerably under represented.
Rainforest patches occur in all aspect classes, but tend to marginally predominate on the more easterly aspects. The data suggests that aspect influences are more pronounced for the larger rainforest patches while the many small patches that are totally restricted to gully-lines reflect more the gully orientation than the influence of aspect.
Almost all the resource is centred on gully-lines, some being totally restricted to these positions whilst the majority of the total area of rainforest occur in patches which extend from gully lines up the side-slopes to varying degrees. Thus, only very few patches that were evident from the remotely sensed data base were not associated with gully-lines.
The existence of some rainforest patches away from gully-lines demonstrates the ability of the community to exist outside of the perceived more mesic gully positions. It appears possible therefore, that some of those patches restricted to gully lines may in fact have retreated and are currently limited to those relatively fire-safe positions under the influence of prevailing fire regimes.
The majority of the resource is situated in those gorges that are narrow and oriented north or south. This distribution may again simply reflect the proportion of the study area with these characteristics rather than environmental benefits obtained from those locations. However, it is possible that these gorge types offer greater protection and hence favour rainforest development than the wider and / or east, west oriented gorges.
Eucalypt forest is the dominant community in the study area and hence is the most frequent community type adjoining rainforest patches both from upslope and downslope positions. However, it
129 Chapter 6 appears to be considerably more frequent on upslope margins of rainforest patches than on the downslope margins. Woodland/Acacia scrub communities increase in importance on downslope patch margins.
The somewhat lower proportion of rainforest patches with eucalypt forest communities adjoining on their downslope margins may reflect the increased potential fire proneness of this community and the associated impacts on rainforest distribution. That is, less rainforest patches now exist upslope of the more fire-prone forest community because they have previously been removed by this agent. Alternatively, woodland/Acacia scrub may have replaced much of the Eucalypt forest downslope of rainforest patches under the influence of fire, whilst the fire-buffering nature of the patches have permitted the Eucalypt forest to persist above the patches.
Many fires have been recorded in the study area over recent times, suggesting that fires are still a relatively frequent phenomenon in the gorges that may indeed still be impacting on rainforest patches and influencing the distribution of the communities. Based on landholder recollections and aerial reconnaissance, over 50% of the area of rainforest has potentially experienced fire since about the early 1960 s.
6.6.3 Fire Vulnerability Assessment
The vulnerability of rainforest patches in the Apsley - Macleay Gorges to fire is a function of the fire susceptibility and fire proneness of each patch. Overall, the majority of individual dry rainforest patches in the gorges were classified as being extremely susceptible to fire and moderately / highly prone to fire.
No geographic pattern of dry rainforest patch fire vulnerability was particularly evident in the Apsiey - Macleay Gorges study area. The majority of patches were classified as being either high or extremely vulnerable to fire influences. In essence, this suggests that many of the rainforest patches
130 Chapter 6
are both susceptible to damage from fire impact and are in positions that are likely to experience fire events in the future, providing a fire ignition source exists (either from natural sources or human activity). Indeed, in excess of 70% of the rainforest patches have high or extreme vulnerability to fire. However, despite the numerous patches in this rather parlous situation, collectively they cover only approximately 21% of the area of rainforest in the Gorges. The majority of the area of rainforest patches (almost 80%) is in a better situation, being classified as being of either moderate or low vulnerability.
From a conservation viewpoint therefore, this study suggests that the majority of the area of rainforest patches is reasonably safe or resilient to fire, despite the likelihood that a large number of the individual patches may actually be at considerable risk.
1_31 CH AI) I) ER 7
DISCUSSION A 1■Ir ID IC C) INT C: S C) i■T
7.1 Introduction
Dry rainforest is recognised as a vegetation community which warrants considerable conservation action. The dry rainforest in the Apsley - Macleay Gorges are extensive in area and also have a distinctive floristic composition. Combined, these two features make the gorges an important conservation resource.
Fire represents a significant threat to dry rainforest. It is implicated as a predominant factor responsible for severely reducing and fragmenting distribution of the community type in Australia. A fortiori, dry rainforest will rapidly recolonise areas previously devastated by fire.
Accordingly, fire management is essential for the areas of the National Park Estate which contain dry rainforest. Manipulation of fire regimes in those areas will promote the conservation of this presently poorly conserved and little understood vegetation community.
The distribution of the dry rainforest community in the Apsley Macleay Gorges is a function of a myriad of factors, including physiography, moisture availability, temperature and slope stability (see King 1930, 115). However, the results of research by Floyd (1980, 1983) and the N.P.W.S (1985), indicate the predominate role played by fire. The experts workshop, presented in Chapter 4 and in Bennett and Cassells (1988a), considered that unmanaged" fire was indeed a significant factor controlling the distribution of dry rainforest in the Gorges. It was also concluded that dry rainforest expansion would be promoted with a reduction or total cessation of burning.
132 Chapter 7
This chapter will review key findings of the study with a view to highlighting management implications and developing specific management and research recommendations.
7.2 Fire Management in the Apsley - Macleay Gorges
Fire management in the Apsley -Macleay Gorges is complex. The implementation of any overall management strategy is complicated by the varying tenure of land in the gorges, and the relatively numerous pastoral landholders controlling these lands. The management objectives and actions of these landholders markedly differ from those of the National Parks and Wildlife Service, which is now the largest single land owner in the gorges.
Fire represents a cheap and effective agricultural management tool (Johnson and Purdie, 1981, 497) to the landholders in and adjacent to the Apsley - Macleay Gorges. It is being used extensively to improve stock forage and to reduce bushf ire risks through fuel reduction burning. Burning operations are widespread and are undertaken on a relatively frequent basis (usually every one to five years). It appears, however, that fire frequencies have declined. On the adjoining tableland, the reduction of burning has occurred in response to the expanding area of improved pastures. In the gorges seasonal conditions over the past few years have kept fuel levels low and hence have reduced the need for fuel reduction burning. Furthermore, the importance of the gorges as a grazing resource is apparently declining, reducing the use of fire.
Historically, fire was used more extensively on the tablelands adjoining the gorges to burn the native pastures and improve their forage value. Improvement of pastures through the addition of fertilizer and better species largely alleviates the need for frequent burning. Indeed, the Department of Agriculture (1985, 7) has estimated that carrying capacities (i.e. DSE s/ha.) can be increased by some 350% to 480% with pasture improvement in this region.
133 Chapter 7
Most burning in the gorges is undertaken between late Winter through mid Spring (August - October) when landholders are moving their stock back onto the tablelands from their gorge leases. At this time precipitation and temperatures are usually low. The prevailing westerly winds are strong, dry and desiccating, providing optimum conditions for management burning operations. While this may be optimum from a pasture management perspective, it could also create burning conditions intense enough to impact on the dry rainforest communities that. occur in the Gorges.
In addition to management fires, bushfires are widespread in the gorges, and in some areas are quite frequent (averaging a fire once every 1-3 years). Most bushfires are thought to originate within the gorges and result predominantly from lightning strike or escaping burnoff operations undertaken by landholders and public authorities.
Lightning ignition would primarily occur on high points in the study area, such as ridgelines. These fires would largely have to burn downslope from the ridges, and consequently would be less intense and have less impact on vegetation than those fires which ignited in the gorge bottoms and burnt upslope. However, as these lightning strike fires are most likely in the hotter summer months, fire intensities may still be considerable. In contrast, "escaping" management fires, ignited on the river flats and footslopes, would burn upslope, and consequently be of greater intensity and potentially more destructive to the vegetation communities that exist there.
Bushfires are impacting on dry rainforest. Indeed, reconnaissance field investigations of some rainforest patches identified significant fire scarring of rainforest trees. This scarring occurred quite deeply into the communities, with the ecotone reflecting particularly high levels of tree fire scars.
The season of burning affects the post-fire recovery of vegetation primarily through it s effect on fire intensity. In southern Australia, fires during Winter and Spring are usually. of low intensity owing to low temperatures and higher fuel
134 Chapter 7 moisture contents, whilst fires in late Summer and Autumn are more intense (Christensen, Recher, and Hoare 1981, 374). However, in transitional Summer rainfall areas like the Apsley - Macleay Gorges, the peak bushfire danger period tends to he earlier, in late Spring or early Summer, provided the normal summer rains occur.
Accordingly, serious bushfires are most prevalent during the hotter Summer and Autumn months when the region s main incidence of precipitation has not eventuated. Even in normal years, soil-water deficits are common and result from the high evapotranspiration potentials that can occur during the Summer (Smith and Johns 1975, 252-253). Furthermore, rainfall is unpredictable from the thunderstorm events prevalent at this time, and it is not uncommon to have some years with very low rainfall in these months (N.P.W.S., 1985, Ch.2).
As stated previously, rural landholders and the National Parks and Wildlife Service have divergent management objectives. Good (1988, 11) has stated that fire suppression in national parks in N.S.W. is still perceived by many as the role and function of rural bushfire brigades. He suggests that this perception is an historic one as the volunteer brigades are staffed by the rural community which often has had a long affiliation with the areas which are now park but which were previously leasehold or freehold grazing lands. Further, a degree of historic animosity remains between the rural community and park managers over management issues such as weeds and feral animal control. These engender scepticism about N.P.W.S. staff and their skills in fire management (Good 1988, 11). This indeed appears to be the situation that currently exists with managers in the Apsley - Macieay Gorges.
Traditional fire management strategies are based on entrenched and sometimes very inflexible management concepts (Good 1988, 11). Good states further that there is considerable pressure, through what he termed "pyre-politics", to maintain the status quo in fire management. In the Apsley - Macleay Gorges this
135 Chapter 7 would imply the continuation of regular and widespread burning during specific periods of the year.
In order to incorporate conservation values in the management of currently non-national park areas, stricter controls need LO be placed on burning operations. Current problems include: Leo frequent burning; burning during hazardous conditions; and the escape of fires from specified areas. The existing fire permit system could be sufficiently tightened to address some of these issues. In addition, N.P.W.S. personnel could be allocated to educate, advise and assist property managers in their burning programmes.
Therefore, improved liaison between landholders and the Service is essential. A need exists for the N.P.W.S. to define an immediate policy for fire management, and managers must be made aware of the policy and its supporting rationale. Furthermore, as property managers currently contribute to programmes for control of dingos, noxious weeds and animals, and bushrires, it is vital that the N.P.W.S. be seen to be allocating sufficient managerial resources to the newly formed and expanding area of national park. This should aim to adequately deal with the concerns of these programmes and alleviate further potential animosity.
7.3 Characteristics of the Dry Rainforest Resource
Some 735 discrete patches of rainforest covering appro.\imaeiy 18,000 ha. occur in the 290,000 ha. Apsley - Macleay Gorges study area. These patches represent some 14% of the vegetation that occurs in the gorges proper. The rainforest patches are extremely variable in both their configuration (i.e., size, area perimeter ratio and shape) and distributional characteristics. They reflect the myriad of factors influencing this vegetation community type in the Gorges.
Overall, patches are relatively small, with over three quarters being less than 20 ha. in area. However, the majority of the
136 Chapter 7 total area of rainforest in the Gorges is contained within the few large patches (i.e., those exceeding 100 ha.) that exist.
A rainfall gradient across the study area (i.e., ranging from annual averages of <800mm to in excess of 1,200mm) appeared to have negligible impact on rainforest distribution. This is in accord with the suggested drought tolerance of the community (Gillison 1987, 305). However, water relationships within the gorges are thought to be influenced by frequent mists and near- surface ground water (King 1980, 113), and this may help to alleviate moisture shortfalls in the lower rainfall areas of the gorges.
The overall aspect preference of patches was minor and appeared to be more important for the larger patches which favoured the moister, south-easterly aspects. The dominating influence of the orientation of the gorges in which most of the small patches are restricted, may reduce the importance of aspect to the smaller patches.
Despite the fact that most of the rainforest is centred on gully and drainage lines within the gorges a significant proportion of rainforest actually extends up the adjacent, steep gully slopes to varying degrees. In addition, a small proportion of rainforest does occur seemingly totally unconnected with gully and drainage lines. This suggests, that given freedom from disturbance, rainforest appears to be able to exist out of the more favourable gully-line habitats. Indeed, this is consistent with the findings of Ash (1988, 622) who has stated that under marginal climatic or edaphic conditions, rainforests typically occur on the lower slopes of valleys but also, occasionally on rocky outcrops, localities which afford some protection from fire.
Rainforest patch distribution suggests a bias towards areas in the gorges with particular slope angles and local relief or elevation. Areas of the gorges with both high and low extremes of slope angle have restricted rainforest occurrence whilst intermediate slopes (i.e., 18-22 0 ) appear to favour rainforest development. Furthermore, the patch distribution suggests that
137 Chapter 7 areas of intermediate elevations (i.e., 400-800m) also appear to be favoured by rainforest, with higher and lower elevations proportionally under represented.
Eucalypt forest vegetation is the most prevalent vegetation community in the gorges and hence is the dominating community adjoining rainforest patches. However, the differential predominance of this community in positions upslope and downslope of patches may reflect differential fire regimes between these positions and / or the removal by fire of previously existing rainforest patches above this perceived highly flammable community. The proportion of patches adjoining woodland/Acacia scrub vegetation is also reasonably high, particularly on the downslope margins of patches.
Reconnaissance field investigations suggest that while fuel loads in adjoining forest and woodland communities may be relatively low in comparison with similar communities elsewhere, fuel loads in the ecotone immediately surrounding some rainforest patches can be very high, reaching in excess of some 20 t/ha. This is high enough to indicate that some positive management response is needed.
7.4 Fire Vulnerability of the Dry Rainforest
Overall, in terms of area, the rainforest of the Apsley Macleay Gorges occurs predominantly in a low and to a lesser extent moderately fire susceptible configuration but almost exclusively in positions that have a high proneness to fire. Combining these two key parameters indicated that although the majority of individual patches were classified as highly vulnerable to fire, the vast majority of the area of rainforest was only moderately vulnerable.
138 Chapter 7
7.4.1 Evaluation of the Fire Vulnerability Classification
Classification of the dry rainforest resource in the Apsley Macleay Gorges enabled the concurrent consideration of many fire-pertinent factors. This facilitated the grouping of patches within which certain attributes are definable and repeatable.
Classification provided a simplified picture of a complex resource, and is convenient and practical for management and planning purposes. An implicit assumption here is that within each group, all the patches have similar fire vulnerability characteristics. Hence they are likely to respond in a similar way with regard to fire and their potential for management.
Each of the four fire vulnerability groups produced from the classification were comprised of individual patches with a definable range of key measured attributes of relevance to fire. For example, patches of highest vulnerability ha\e characteristics which make them both very susceptible and prone to fire while the characteristics of less vulnerable patches make them either less susceptible or less prone to fire, or both.
Due to the broadscale nature of the data used in the classification of rainforest patches, field verification of the groupings is certainly required. Field examination of representative samples of patches from each fire vulnerability class would facilitate the evaluation of the validity of the groupings.
In addition, a key factor which was omitted from the classification due to the lack of sufficiently high-resolution aerial photography, was that of the condition of the rainforest patch boundaries. As discussed in Chapter 2, the boundary condition of rainforest patches often reflects the role of fire to the patch. However, field investigations to date have shown that the boundary conditions on most patches are complex, with combinations of both sharp and diffuse boundary types ot-L- relatively short distances.
139 Chapter 7
Thus, while the actual boundary conditions may indeed provide an indication of the fire dynamics at that particular point, the pervasive variability of the boundary precludes use of such parameters for extensive, detailed management planning. Indeed, the reliance on the more easily observed overall patch characteristics used in this study seems to be the only practical alternative to a spatially complex and extremely demanding, high-cost management approach based on actual boundary condition types.
7.4.2. Implications for Management
The majority of individual rainforest patches were classified as highly or extremely vulnerable to fire. However, the majority of the actual total area of rainforest in the gorges was of only moderate, or to a lesser extent, low vulnerability. Therefore, much of the area of dry rainforest in the gorges is reasonably safe from or resilient to fire events, despite the fact that many of the individual rainforest patches are at considerable risk and may potentially be damaged or totally destroyed by fire events in the future.
The vulnerability of patches is variable throughout the study area with no marked geographic pattern of vulnerability classes particularly evident. However, a slightly greater proportion of patches in Geographic Management Zone 1, 7, and 8 are of high or extreme vulnerability, whilst GMZ s 1 and 5 contain a proportionally larger number of patches of moderate and low vulnerability to fire.
Fire ignition sources are perceived to be more prevalent in the eastern zone of the study area (within GMZ 7 and 8), due to high levels of pastoral activity (Chapter 4; Bennett and Cassells 1988a, 11). Consequently, a large proportion of patches in those GMZs are under significant threat as many are of high or extreme fire vulnerability. Indeed, the high / extreme vulnerability of many of the patches in these areas may
140 Chapter 7 actually reflect the effects of this higher fire frequency- scenario.
Implicit within the fire vulnerability classification of rainforest patches is the significance of fire to the patch, the likelihood and the behaviour of fire in the vicinity of the patch, and the potential of the patch for management. As the fire vulnerability of patches increases, so does the significance, likelihood and damaging behaviour of a fire event. Management potential declines with the increasing vulnerability of patches. This situation is reversed with decreasing patch fire vulnerability.
Thus, patches with a low fire vulnerability by definition are more viable rainforest units. They are generally larger and more compact in shape and hence have high integrity and robustness. Fire is likely to be a less frequent event in their vicinity, but if and when it does occur it would be of low intensity and potentially simple to control. Finally, their management potential is high, with probably only the upslope boundary of the patch requiring protection. This could be undertaken through back-burning operations which if executed under appropriate climatic conditions should be easily implemented from the ground or air.
In contrast, patches which are of extreme or even high fire vulnerability are usually less viable rainforest units. These patches are smaller and less compact, and hence have reduced integrity and robustness. Fire is likely Lo be a recurrent event in their vicinity and by nature of the likely terrain and adjoining vegetation community, would probably be intense and difficult to control. Management would probably need to consider both the upslope and downslope boundaries of the patch and any burning operations undertaken would be considerabLy more difficult to implement and control.
It is obvious that some form of differential management input is required for the dry rainforest patches in the gorges. This is possible for the differing patch vulnerability groupings and such a strategy should produce differential benefits in terms
141 Chapter 7 of rainforest conservation. Management can range from very little or extensive management input for the lower vulnerable patches (which in many cases may be largely self protected), through to very high and intensive input (if at all possible) for the more highly vulnerable patches.
The extensive and fragmentary nature of the dry rainforest in the Apsley - Macleay Gorges, coupled with the budgetary and labour constraints faced by the N.P.W.S., precludes the active management of every individual patch in the total resource. Consequently, a management programme must prioritise and target its operations to areas where management is both possible and would result in maximum rainforest conservation benefits.
At first glance, it appears that the management priority should be to address those patches with extreme and high fire vulnerability. These patches are at greatest risk and are probably subject to recurrent fire. However, due to the condition, extensive number, and dispersed nature of these patches, their management would consume substantial resources and time. The resulting gains in terms of rainforest protection would be limited as these patches account for only a small proportion of the total area of rainforest in the gorges.
A more effective management approach would be to target management input to patches with lower vulnerability ratings. These patches are less at risk from fire and are in a condition that would involve less intensive management. Also, management strategies would be more be successful and achieve long term rainforest protection.
Management programmes for these patches could potentially consist of extensive aerial-ignited backburn operations, with low intensity fires burning downsiope from the ridgelines. This would provide low fire risk buffers close to the patches. In this way large areas of the resource could be adequately protected with the involvement of only limited manpower and equipment.
142 Chapter 7
Indeed, it seems likely that much of the low and moderately fire vulnerable patches could be largely self protecting through topographic or other factors. The active protection of these patches and a limited number of the extremely numerous more vulnerable (and generally small) patches from fire impact may permit their expansion if they were previously fire limited. Furthermore, the adoption of such a strategy could facilitate the coalescing and consolidation of some patches into even larger units, with a probable concomitant reduction in their combined fire vulnerability. However, with the slow- growing nature of the dry rainforest communities in these gorges (Floyd 1983, 2), such a strategy for selected fire vulnerable patches would need to involve time commitments of a decade or more to be effective.
7.4.3 Implications for Research
The broadscale patch classification system developed in this study provides a practical basis for ensuring the conservation of the vast majority of the existing dry rainforest resource in the Apsley - Macleay Gorges. Initially at least, the patch classification system and any management programme that flows from it should only be regarded as an interim, first approximation. This should be subject to continuing evaluation through environmental monitoring to determine its effectiveness.
Rigorous recording of the extent and impact of both management fires and bushfires needs to be undertaken. In conjunction with this is the need for regular monitoring of the persistence of the rainforest resource and the response of any actively protected patches.
However, understanding what is happening is only the first requisite for effective, long-term management. Sustainable, scientifically-based decision making can only be achieved if managers know how and why changes in the vegetation are occurring. Managers must have a realistic appreciation of the
1-13 Chapter 7 ecological processes behind the vegetation changes. Therefore investigation of the ecological processes influencing rainforest boundary dynamics is clearly a longer term research priority.
The consensus of the experts workshop presented in Chapter 4 was that there is considerable potential for rainforest expansion in the gorges in the absence of fire. Of significant importance is the assessment of the boundary dynamics of the rainforest patches in the gorges. As discussed in Chapter 2, the structure and composition of the boundary or ecotone separating rainforest from other vegetation communities provides an indication of the dynamic nature of the rainforest boundary. This is largely perceived to be in response to differing fire regimes and fire behaviour. Thus, an understanding of the boundary dynamics of patches should provide some indication of the importance of past and current fire regimes on patches and the potential of the patch for expansion in the absence of fire.
Logically, such process investigations should be organised around the various boundary types described earlier (Chapter 4 and in Bennett and Cassells (1988a, 32). For each boundary type, the following research questions need to be addressed:
Are edaphic conditions limiting rainforest distributions?
What is the nature of the rainforest microclimate and under what conditions might it break down and facilitate the ingress of fire? Can this information be used to refine the existing patch vulnerability classification?
What are the regenerative capabilities of the various rainforest species? How rapidly can rainforest colonise areas in the absence of fire and what is the ultimate potential for expansion of the community?
144 Chapter 7
7.5 Conclusions and Recommendations
The investigations described in this study have extended knowledge about the fire history and current fire management environment of the Apsley - Macleay Gorges. Most importantly, it describes the potential fire vulnerability of the dry rainforest resource that exists in the Gorges.
Whilst the majority of individual rainforest patches were classified as high or extremely vulnerable to fire, by far the majority of the total area of rainforest in the c ordes- was of only moderate, or to a lesser extent, low vulnerability. Therefore, much of the area of dry rainforest in the gorges is reasonably safe from or resilient to fire events. This is despite the fact that many of the individual rainforest patches are at considerable risk and may potentially be damaged or totally destroyed by fire events in the future.
The management strategy suggested in this report involves a low cost holding operation to ensure the conservation of the bulk of the rainforest resource. Simultaneously, the fire interaction status of the large number of generally small, vulnerable patches is clarified. The strategy recognises the impracticality of actively protecting every small patch in the gorges. It is therefore based on a more selective two-pronged approach.
The first aspect of this approach is to protect those patches which have a low to moderate fire vulnerability. These patches cover a significant proportion of the total resource and are relatively easy to manage. Protection would be assisted by early buffer burning to isolate the patch edges from the impact of later, more damaging fires that might either scorch the rainforest edge or encroach into the rainforest proper. The timing of these buffer burns should be determined by PREPLAN analysis. Given the constraints of access and topography, these burns would almost certainly involve aerial ignition from helicopter or light plane.
145 Chapter 7
The second aspect of the approach is the active protection of a small number of the generally smaller, highly vulnerable rainforest patches. These patches represent a different aspect of rainforest in the gorges. Their active protection would ensure their preservation and provide a test of the potential for rainforest expansion in the absence of fire. Similar buffer burning techniques to those outlined above for the lower vulnerable patches could be used, However, an additional requirement would be the need to maintain an unburnt buffer of at least 40 - 50 metres around each patch to allow for any rainforest expansion that might occur.
Additional management oriented research is also required for more effective, more scientifically based decision-making in the future. The most immediate priority is the rigourous monitoring of both fire occurrence and fire impacts in the gorges. A longer term priority is to develop a better understanding of the ecological processes that control the boundary dynamics of dry rainforest patches in the gorges.
The assessment procedures and management recommendations developed in this study should also be relevant to other areas with similar resource characteristics. One area where they could perhaps be immediately applied is the nearby Guy Fawkes River National Park, where very similar ecological conditions and management problems exist.
146 FLEFER.ENCES
Ash, J. 1988. The Location and Stability of Rainforest Boundaries in North-Eastern Queensland, Australia. J. Biogeography 15, 619-630.
Baur, G.N. 1957. Nature and Distribution of Rainforests in New South Wales. Aust. J. Bot. 5, 190-233.
Baur, G.N. 1968. The Ecological Basis of Rainforest Management. Forestry Commission of N.S.W., Sydney.
Bennett, R.J. and Cassells, D.S. 1988a. Dry Rainforests Fire Interactions: Considerations For Research and Management. Unpublished Report to the N.P.W.S. Department of Ecosystem Management, University of New England.
Bennett, R.J. and Cassells, D.S. 1988b. Apsley - Macleay Gorges Fire History Survey. Unpublished Report to the N.P.W.S. Department of Ecosystem Management, University of New England.
Bennett, R.J. and Cassells, D.S. 1939. Characteristics and Fire Vulnerability Assessment of the Dry Rainforest in the Apsley - Macleay Gorges. Unpublished Report to the N.P.W.S. Department of Ecosystem Management, University of New England.
Brickhill, J. 1974. An Investigation of the Macleay River Gorges to Assess Their Suitability as a National Park. Unpublished B.Nat.Res. Thesis. University of New England.
Cheney, N.P. 1981. Fire Behaviour. In Gill, A.M., Groves, R.H. and Noble, I.R. Fire and the Australian Biota. pp.151-176. Australian Academy of Science, Canberra.
Christensen, P., Recher, H., and Hoare, J. 1981. Responses of Open Forest to Fire Regimes. In Gill, A.M., Groves, R.H. and Noble, I.R. Fire and the Australian Biota. pp.367- 394. Australian Academy of Science, Canberra.
Clayton-Greene, K.A. and Beard, J.S. 1985. The Fire Factor in Vine Thicket and Woodland Vegetation of the Admiralty Gulf Region, North-West Kimberly, Western Australia. Proc. Ecol. Soc. Aust. 13, 225-230.
Cremer, K.W. 1960. Eucalypts in Rainforests. Aust. For. 24, 120-126.
Cromer, D.A.N. and Pryor, L.D. 1942. Contribution to Rainforest Ecology. Proc. Linn. Soc. N.S.W. 67, 249-268.
147 References
Crown Lands Office, N.S.W. 1985. Land Asessment and Disposition Process for Crown Land - Macleay-Apsley Area. Submission to the Department of Environment and Planning.
Department of Agriculture, N.S.W. 1985. An Agricultural Survey to Determine the Effects on Agriculture of Proposed Developments by the N.P.W.S. and/or the Electricity Commission of N.S.W. Submission to the Department of Environment and Planning.
Department of Environment and Planning. 1986. Macleay Report -Apsley Natural Resources and Landuse toStudy. the Minister for Planning and Environment.
Dodson, J.R. 1984. Dynamics of Nothofagus moorei Rainforest at Barrington Tops, New South Wales. In Werren, G.L. and Kershaw, A.P. (eds.) Australian National Rainforest Study Report, Volume 1. pp.520-523. Monash University, Melbourne.
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151 References
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153 F, ID X 3 _ -i
1-11 IR ER I ST I CS OF STU CYY AR EA
Proportion of Study Area in Each Elevation Class
Elevation Area (ha.) % of Total
0-100 125 <1 100-200 4250 1.5 200-300 12625 4.4 300-400 21925 7.6 400-500 25725 8.9 500-600 29725 10.3 600-700 25400 8.8 700-800 28375 9.8 800-900 37850 13.1 900-1000 65875 22.8 1000-1100 27725 9.6 1100-1200 7850 2.7 >1200 1850 0.6
Proportion of Study Area in Each Slope Angle Class
Slope Angle (degrees) Area (ha.) Proportion of Study Area (%)
0-1 13175 4.6 1-3 7550 2.6 3-6 28700 9.9 6-10 39350 13.6 10-20 83425 28.8 20-40 116200 40.2 40-70 350 0.1 >70 550 0.2
Proportion of Study Area in Each Aspect Class
Aspect (degrees) (ha.) Proportion of Study Area (%)
0-45 70725 24.5 45-90 38450 13.3 90-135 18875 6.5 135-180 49425 17.1 180-225 26425 9.1 225-270 34450 11.9 270-315 15475 5.4 315-360 35275 12.2
154 Appendix 3
APPENDIX 3.2
Proportion of Study Area in Each Rainfall Isohyet Class
Isohyet Class (mm) Proportion of Study Area (%)
<800 20 800-900 45 900-1000 8 1,000-1,100 5 1,100-1,200 4 >1,200 18 Appendix 3
APPENDIX 3.3
Proportion of Study Area Covered by Each Vegetation Type
Vegetation Community Area (ha.) Proportion of Study Area (%)
Woodland 53750 18.6 Open Forest 171350 59.2 River Terrace 500 0.2 Rainforest 13225 4.6 Acacia Scrub 350 0.1 Rock 525 0.2 Cleared/Grassland 49600 17.1
156 Appendix 4
A FF E NJ ID X 4 - 1
W CDR K S 1-1 C.) F F ARTiC I F3 A NI T S
Dr J. Ash, Botany Department, Australian National University.
Ms K. Baily, National Rainforest Conservation Program.
Mr R. Bennett, Department of Ecosystem Management, University of New England.
Mr J. Brandis, Forestry Commission of N.S.W.
Mr D. Cassells Department of Ecosystem Management, University of New England.
Mr P. Davies, National Parks and Wildlife Service of New South Wales, Armidale.
Dr J. Duggin, Department of Ecosystem Management, University of New England.
Mr N. Fenten National Parks and Wildlife Service of New South Wales, Port Macquarie.
Dr S. Ferrier, National Parks and Wildlife Service of New South Wales, Armidale.
Mr A. Floyd, National Parks and Wildlife Service of New South Wales.
Dr M. Gill, Division of Plant Industry, CSIRO, Canberra. Appendix 4
Dr A. Gillison, Division of Wildlife and Ecology Research, CSIRO, Atherton, Queensland.
Mr R. Good, National Parks and Wildlife Service of New South Wales, Canberra.
Mr G. Holloway, National Parks and Wildlife Service of New South Wales, Grafton.
Mr J. Kent National Parks and Wildlife Service of New South Wales,
Mr R. Leggatt, Superintendant, National Parks and Wildlife Service of New South Wales, Armidale.
Ms R. Lott, Department of Ecosystem Management, University of New England.
Mr. W. McDonald, Botany Branch, Queensland Department of Primary Industry.
Professor H. Nix, Director, Centre for Resource and Environmental Studies, Australian National University.
Mr S. Phillips, National Parks and Wildlife Service of New South Wales, Lismore.
Mr G. Roberts, National Parks and Wildlife Service of New South Wales, Armidale.
158 Appendix 4
Ms C. Sandecoe, Queensland National Parks and Wildlife Service.
Mr P. Sattler, Queensland National Parks and Wildlife Service.
Dr J. Smith, Department of Geography and Planning, University of New England.
Dr G. Stocker, Division of Forest Research, CSIRO, Atherton, Queensland.
Ms S. King, National Parks and Wildlife Service of New South Wales, Sydney.
Mr G. Unwin, Division of Wildlife and Ecology Research, CSIRO, Atherton, Queensland.
Mr G. Watson, Department of Ecosystem Management, University of New England.
Mr J. Whitehouse, Director, National Parks and Wildlife Service of New South Wales,
Mr J. Williams, Botany Department, University of New England. APPENDIX 5.1 SURVEY QUESTIONNAIRE DEPARTMENT OF ECOSYSTEM MANAGEMENT THE UNIVERSITY OF NEW ENGLAND
ARMIDALE. N.S.W. 2351. AUSTRALIA
`4 REPLY PLEASE COTE
CONFIDENTIAL
Rural Fire Management in the Maclea y - Apsley Gorg es Region
This is a questionnaire prepared for a survey of all landholders in or adjacent to the Macleay - Apsley gorge region of Northeastern New South Wales, which is to be undertaken between January - February, 1988.
The purpose of this questionnaire is to compile a comprehensive assessement of past fire events in the Macleay - Apsley Region, including both bushfires and fires ignited by landholders for management purposes.
Understanding the historical and current fire patterns in this area will provide an information base of the role and complexities of fire management in agricultural and natural systems, particularly the influence fire has on existing vegetation patterns. The Macleay - Apsley gorges region was chosen as the study site because it has a well established agricultural and pastoral industry and is experiencing increasing interest in its resources for outdoor recreation, tourism and nature conservation. It therefore provides an ideal case study of the problems and opportunities associated with integrated rural land-use.
A summary of the results of this survey will be forwarded to you, if you indicate your interest to the interviewer.
160 1. What is the total size of your property, in area?
(hectares) or (acres)
2. Dividing your property into its gorge-land and top-land components, what is the size of each component, in area?
Gorg e countr y : (hectares) or (acres) Top country : (hectares) or (acres)
3. What area of your property is under native forest at present?
Gorg e country : (hectares) or (acres) Top country : (hectares) or (acres)
4. Do you maintain rainfall records for your property? yes no
5. If you do maintain rainfall records, a) how long have you been recording them and b) what is your average annual rainfall? a) (years)
b) (millimetres) or (points) or (inches)
6. Would you be willing to make your rainfall records available to University staff for research purposes?
yes no
7. Do you use fire in the management of your property?
yes sometimes never
If ou answered NEVER t lease •roceed directl to 16
161 8. If fire is used in the management of your pro p erty, Please list, on the lines provided, the specific purpose(s) for which it is used, and in the box below tick the appropriate rating of importance for each purpose. a)
essential important I not important
b)
essential important [ not important [ c)
essential important not important
9. For any particular area of your property, how frequently would you use fire as part of your management program? every year every two - three years every four - five years every six - seven years every eight - nine years other (please specify period)
10. What area of your property do you burn as part of your management program?
Gorg e country (hectares) or (acres) Top country (hectares) or (acres)
11. Are there any particular areas of your property where you try to keep fire out? no
yes (please specify what areas and why)
162 12. In what month(s) do you usually carry out burning operations for your property?
13. Predominantly, what type of fires occur during your burning program?
grass fires only grass and undergrowth fires tree-top fires all of the above
14. How has your use of fire to assist in the management of your property changed over time? unchanged more frequent burns less frequent burns
15. If your use of fire has changed, why has it changed?
The following questions are concerned with UNPLANNED BUSHFIRES only
16. Are unp lanned bushfires of concern to you and your property?
yes no
17. In order of importance (1 = most important) where do most unplanned bushfires that affect your property start?
gorge-lands neighbouring property own property unsure other (please specify)
163 18. From your knowledge, what are the causes of these unplanned bushfires? (please rank these in order of importance, 1= most important)
escaping landholder management burnoffs carelessness by tourists and bushwalkers lightning strike deliberate arson other (please specify)
19. How often does the gorge-lands country portion of your property burn as a result of unplanned bushfires? yearly every two - three years every four - five years every six - seven years every eight - nine years other (please specify) -
20. How often does the top-country portion of your property burn as a result of unplanned bushfires? yearly every two - three years every four - five years every six - seven years every eight - nine years other (please specify)
21. From your knowledge of the area, do you recall any major unplanned bushfire events that have burnt your property over the years?
yes I unsure 1 no
1
22. If you do recall major bushfire events, could you please list the dates of these fires as precisely as possible and indicate their location on the map provided?
164 22. In order of frequency (1= most common) what type(s) of unplanned bushfire(s) occur in the gorge-lands? grass fires grass and undergrowth fires tree-top fires all of the above together
24. From your knowledge, have any of the patches of rainforest scrub in the gorge-lands burnt during any fire event(s)? yes unsure no
25. Has the area of rainforest scrub on your property changed over time? expanded I contracted I unchanged I uncertain
26. Are there any particular areas of your property that you feel need protection from fire?
no yes (please specify where and why)
27. What fire control methods do you use on you property?
28. In your opinion, what additional help or techniques are needed for fire control in your area?
165 29. Are you aware of any access tracks/paths into the gorge-lands that may he useful for fire control purposes?
no yes (could you please locate these on the map)
30. Are there any public authorities with land management and/or fire-control responsibilities in the gorgelands in your area?
no yes (please specify what authorities)
31. Have you had any contact or involvement with any of these government authorities? no yes (please specify which authorities and pupose of contact)
32. Do the gorge-lands cause you any problems in the management of you property? no yes (please specify management problems)
33. The New South Wales Government has recently ap p ointed a community based advisory committee to bring local concerns about the management of the districts national parks to the attention of the National Parks and Wildlife Service. One of the major parks of concern to the committee is the Oxley Wild Rivers National Park, which covers parts of the gorge-lands country. Are you aware of the existence of this commitee?
yes no
166 34. If you are aware of this commitee, do you know how to contact its members to discuss matters that concern you with regard to the management of the gorge-lands country? yes no 1 I
Note: Any further comments on any aspect arising from this questionnaire would be greatly appreciated.
167 Atc=• F t■IIDIX 5.2
II■111- 1:2\1ICW LIST AND RAINFALL_ FRECCDFZED
a b d e f g
1 2 Blomfield Cheyenne 354 58 813 2 2 Firenze Uruga 803 8 864 3 2 Giovanovic Table Top 1040 1 965 4 2 Harrison Paradale 845 5 2 Blomfield Kambala 1149 15 864 6 2 Blomfield Karori 1140 43 950 7 2 Schaeffer Ellandoran 551 7 914 8 2 Weber Glendowner 1610 30 890 9 2 Thomas Rowleys Creek 1134 28 914 10 2 Mathews Jiskadale 907 16 890 11 2 O Keefe Garibaldi 4200 57 40 864 12 2 Hoare Bushmede 242 1140 13 1 Edgar Rosewood 487 46 822 14 1 Browning Wattle Grove 1296 27 813 15 2 Lawrence The Peak 330 838 16 2 Bagnall Nyendanni 436 63 914 17 2 Glasson Hole Creek 660 18 1 Jerrett Ellera 2000 97 19 2 Watts Bulimba Downs 1616 8 890 20 2 Lockyer The Retreat 240 890 21 2 Partridge Falls View 836 9 800 22 2 Vance Yarrobindi 2029 10 19 1000 23 2 Watt Burraki 3307 18 9 1220 24 Madeley Benditi 2000 15 1090 25 2 Ireland Bundagra 1037 3 840 26 2 Stuart Rambrah 963 50 840 27 9 Kermode Tral ee 502 18 810 28 2 O Keefe Bulgroo 1724 5 46 820
168 Appendix 5
29 2 O Keefe Oaklands 14800 95 51 813 30 2 O Neill Days Mountain 7189 99 889 31 1 Johnston Beguna 630 813 32 2 Hoy Paradice 512 3 1067 33 2 Blake Millbank 4000 50 965 34 2 Noakes Old Wombi 984 25 940 35 2 Kirton Carinya 953 914 36 1 Scheef Avondale 48 2 37 2 Young The Park 488 3 787 38 2 Beattie Gisborne Park 140 10 780 39 2 Hammond Clonmel 1600 40 2 Hammond Kylie 724 39 41 2 Waters Silverton 2667 45 26 813 42 1 Moffit Fortrose 1640 50 813 43 1 King Waterloo 245 44 2 Fletcher Cairnie 1320 35 685 45 2 Goodwin Glenville 14400 100 46 2 Cameron Tiara 2000 47 2 Lockyer The Retreat 1600 914 48 2 Halloran Ti-tree Springs 405 26 1016 49 2 Sendal/Curran Kimberly Park 1600 20 965 50 2 Welsh Rock End 800 13 14 914 51 2 Beattie Braeburn 265 18 900 52 2 Boydell Riverglade 860 914 53 2 Erratt/Pettit Brookside 1055 54 2 Partridge Summervale 860 9 813 55 2 Leahy Victoria Park 2320 10 1070 56 1 Rogers Meroo 356 31 34 762 57 1 Rowbottom New Park 960 42 5 1015 58 1 Waters East View 5000 82 38 864 59 1 Wright Jeogla Stn. 6200 85 997 60 1 Lawrence Hillgrove 398 30 864 61 1 Booth 62 4 Brennan Table Top 945 30 864 63 1 Faint May View 12400 95 50 914 64 1 Mullen Mt. View 779 65 1 Swindale Apple Grove 66 1 Townsend Sylvannia 486 25 752 Appendix 5
67 1 Morgan Enfield North 1840 34 915 68 2 Hicks Beaufort 5772 88 25 1078 69 2 Coffey Kenwood Park 1240 6 762 70 1 McClenaghan Acaire 400 890 71 1 McRae Briston Park 19840 97 20 914 72 9 Saunders/Knight Sunnyside 1000 20 967 73 9 Ruthberg/Tombs Spike Island 390 16 813 74 9 Hands St. Helena 1200 75 1 Morgan Taabinga 680 76 1 Anderson Brookside 77 1 Cicolini Isle of Clouds 30900 87 965
a. = Interview case number
b. = Geographic management zone
= Manager / owner
d. = Property name
e. = Total property area (Ha. . Percent of property in gorges
Q. = Period rainfall records maintained
h. = Average annual rainfall (mm)
170 Appendix 5
A P PEN ID I X _
etliS1-1F• IlF2 PC)INITS
GORGE (Ranking From Most to Least Important) 1 2 3 4 5 (%) (%)) ( %) (%)) (%)
Total 65.3 68.3 22.8 0 23.6 T l 66 9.4 1.9 0 22.6 G T l 61.1 5.6 5.6 0 27.8
NEIGHBOURING PROPERTY 1 2 3 4 5
Total 16.7 18.1 5.6 0 59.7 T l 11.3 20.8 5.7 0 62.3 G T l 33.3 11.1 5.6 0 50
OWN PROPERTY , 1 2 .3 4 5
Total 9.7 4.2 1.4 0 84.7 T l 11.3 3.8 1.9 0 03 G T l 5.6 5.6 0 C 83.9
UNSURE 1 2 3 4 5
Total 4.2 0 0 0 95.8 T l 5.7 0 0 0 94.3 G T l 0 0 0 0 100
171 Appendix 5
OTHER 1 2 3 4 5
Total 8.3 2.8 0 0 88.9 T l 11.3 0 0 0 88.7 G T l 0 11.1 0 0 88.9
APP'ENOTX 5_4
CAUSES CDF BUSIAFTIR IGNITION
ESCAPING MANAGEMENT BURNOFFS 1 2 3 4 5
(%) ( %) ( %) (%) ( % )
Total 34.7 24 4 0 37.3 T l 99.1 29.1 1.8 0 40 G T l 47.4 10.5 10.5 0 31.6
CARELESSNESS 1 2 ..,3 4 5 Total 13.7 16.4 4.1 1.4 64.4 T l 13 16.7 5.6 1.9 63 G T l 16.7 16.7 0 0 66.7
LIGHTNING 1 2 3 4 5
Total 56.8 29.7 1.4 0 12.2 T l 60 27.3 1.8 0 10.9 G T l 44.4 38.9 0 0 16.7
172 Appendix 5
ARSON 1 2 3 4 5
Total 1.4 0 2.7 4.1 91.8 T l 1.9 0 1.9 3.7 92.5 G T l 0 0 5.6 5.6 88.9
OTHER 1 2 3 4 5
Total 2.7 2.7 1.4 0 93.2 T l 3.7 3.7 1.9 0 90.7 G T l 0 0 0 0 100
_
1313S1-1F- TIRE FIFRIE
GRASS 1 2 3 4 5 (%) (%) (%) (36) (%)
Total 26.9 13.4 0 57.7 T l 22.4 10.2 0 65.3 G T l 35.3 23.5 0 41.2
GRASS AND UNDERGROWTH 1 2 3 4 5
Total 68.7 13.4 0 17.9 T l 69.4 16.3 0 14.3 G T l 70.6 5.9 0 23.5
173 Appendix 5
CANOPY 1 2 3 4 5
Total 3 10.4 10.4 76.1 T l 4.1 10.2 10.2 75.5 G T l 0 11.8 11.8 76.5
ALL 1 2 3 4 5
Total 10.4 4.5 3 82.1 T l 10.2 6.1 2 81.6 G T l 11.8 0 5.9 82.4
174 APPENDIX 6_1
1:2S,000 SCALE MAPHEETS, OF THE STUDY AREA
Mapsheet Study Code
Gostwyck 1
Hillgrove 2
Enmore 3
Winterbourne 4
Rowleys Creek 5
Apsley 6
Tia 7
Yarrowitch 8
Jeogla
Bighill 10
Carral 11
Kunderang 12
Green Gully 13
Kangaroo Flat 14
Will Willi 15
Kemps Pinnacle 16
175 ARRENEDIX 6 - 2
r- r)-t. i b i 1 i ty Rar-ametE Cc mti rii -t- I ores and ci ices
Index Shape Area Class A:P Ratio Class
(ha.) (m2/m)
3 linear <5 <20
4 block <5 <20
4 linear 5-20 <20
4 linear <5 20-50
5 block <5 20-50
5 linear 5-20 20-50
6 block 5-20 20-50
6 linear <5 50-100
7 block <5 50-100
7 linear 5-20 50-100
8 block 5-20 50-100
8 linear <5 >100
9 linear 20-100 20-50
10 block 20-100 20-50
10 block 5-20 >100
176 Appendix 6
11 linear 20-100 50-100
12 block 20-100 50-100
13 linear 20-100 >100
14 block 20-100 >100
15 linear >100 20-50
17 linear >100 50-100
18 block >100 50-100
20 block >100 >100
177 APPENDIX 6 ,... 3
F i r- r- r-1 s s ram-t r- s a_ rl cl I rl cl
Index Aspect Slope DAC Topo. Pos.
(0 )
4 west >22 grass ridge
5 east >22 grass ridge
5 west 12-22 grass ridge
5 west >22 forest ridge
5 west >22 grass low-mid
6 east >22 forest ridge
6 west 12-22 forest ridge
6 west >22 forest low-mid
7 east 12-22 forest ridge
7 east >22 forest low-mid
7 west 0-12 forest ridge
7 west 12-22 forest low-mid
0 east 0-12 forest ridge
8 east 12-22 forest low-mid
8 west >22 forest ext
9 east 12-22 grass ext
Q east >22 forest ext
9 west 12-22 forest ext
9 west >22 woodland ridge
178 Appendix 6
10 east 12-22 forest ext
10 east >22 woodland ridge
10 west 0-12 forest ext
10 west 12-22 woodland ridge
10 west >22 woodland low-mid
11 east 0-12 forest ext
11 east 12-22 woodland ridge
11 east >22 woodland low-mid
11 west 12-22 woodland low-mid
12 east 12-22 woodland low-mid
12 west >22 woodland ext
13 east >22 woodland ext
13 west 12-22 woodland ext
14 east 12-22 woodland ext
14 east >22 grass gully
14 west 12-22 grass gully
14 west >22 forest gully
15 east 12-22 grass gully
15 east >22 forest gully
15 west 12-22 forest gully
15 west >22 inert ridge
16 east 12-22 forest gully
16 east >22 inert ridge
16 west 0-12 forest gully
16 west 12-22 inert ridge
16 west >22 inert low-mid
17 east 0-12 forest gully
17 east >22 inert low-mid
179 Appendix 6
17 west 12-22 inert low-mid
18 east 12-22 inert low-mid
18 west >22 inert ext
18 west >22 woodland gully
19 east >22 inert ext
19 east >22 woodland gully
19 west 12-22 inert ext
19 west 12-22 woodland gully
20 east 12-22 inert ext
20 east 12-22 woodland gully
20 west 0-12 woodland gully
21 east 0-12 woodland gully
24 west >22 inert gully
25 west 12-22 inert gully
26 east 12-22 inert gully
180 AF F ENIEDIX 6 _
FIRE VULNERABILITY LISTING AND INDEX
Fire Susceptibility Fire Proneness Index
Extreme Extreme 2 Extreme High 3
High Extreme
Extreme Moderate 4
High High 4
Moderate Extreme 4
Extreme Low 5
High Moderate 5
Moderate High ..)5
Low Extreme 5
High Low 6
Moderate Moderate 6
Low High 6
Moderate Low 7
Low Moderate 7
Low Low 8
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ND ND NO ND N) N) N) ND k) ND CD CD Tx CO CD CD Go Go CO CD a) Go CO N3 1 0 NJ UD -4 -4 -4 -4 cn cn cn cn Cn Cn 44 44 ND ro PO -1 -4 -4 -A OD
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z m GMZ ID MS GMZ ID MS INDEX
1 68 2 1 70 2 4 1 72 2 1 73 2 4 1 75 2 1 76 2 4 1 77 2 1 78 2 4 1 79 2 1 83 5 4 1 84 5 1 85 5 4 1 87 5 1 88 5 4 1 90 5 1 91 5 4 1 92 5 1 93 5 4 1 94 5 1 95 5 4 1 207 5 1 100 5 4 1 111 4 1 112 4 4 1 113 4 1 114 4 4 1 115 4 1 116 4 4 1 117 4 1 118 4 4 1 119 4 1 .120 4 4 1 121 4 1 122 4 4 1 123 4 1 125 4 4 1 126 4 1 127 4 4 1 128 4 1 129 4 4 1 131 4 1 132 4 4 1 134 4 1 136 4 4 1 138 4 1 139 4 4 1 145 4 1 146 4 4 1 147 4 1 149 4 4 1 151 4 1 152 4 4 1 154 4 1 155 4 4 1 156 4 1 157 4 4 1 158 4 1 160 4 4 1 161 4 1 164 4 4 1 165 4 1 167 4 4 1 168 4 1 169 4 4 1 171 4 1 174 4 4 1 180 4 1 181 4 4 1 183 4 1 185 6 4 1 187 6 1 190 6 4 1 192 6 1 103 5 4 1 207 4 2 2 6 4 2 3 6 2 4 6 4 2 5 6 2 6 6 4 2 7 6 2 8 6 4 2 11 6 2 12 6 4 2 14 6 2 15 6 4 2 16 6 2 17 6 4 2 18 6 2 19 6 4 2 20 6 2 21 6 4 2 23 6 2 28 6 4 2 30 6 2 36 6 4 2 37 7 2 40 7 4 2 41 8 2 43 8 4 2 47 8 2 49 8 4 24. 50 8 2 51 8 4 2 54 8 2 55 8 4 2 59 8 2 61 8 4 2 68 8 2 70 8 4 2 77 11 2 78 11 4 2 79 11 2 81 11 4
184 GMZ ID MS GMZ ID MS INDEX
2 82 11 2 88 11 4 2 90 11 2 89 11 4 2 91 11 2 92 11 4 2 95 11 2 96 11 4 2 101 11 2 103 11 4 2 104 11 2 105 11 4 2 107 11 2 108 11 4 2 109 11 2 112 11 4 2 114 11 2 115 11 4 2 116 11 2 117 11 4 2 120 11 2 121 11 4 2 122 11 2 124 11 4 2 125 11 2 131 12 4 2 132 12 2 135 12 4 2 138 12 2 140 12 4 2 141 12 2 142 12 4 2 145 12 2 146 12 4 2 148 12 2 150 12 4 2 151 12 2 152 12 4 2 153 12 2 154 12 4 2 155 12 2 156 12 4 2 159 12 2 164 12 4 2 165 12 2 166 12 4 2 167 12 2 168 14 4 2 173 14 2 181 15 4 2 183 15 2 184 15 4 2 185 15 2 186 12 4 3 1 2 3 2 2 4 3 3 2 3 5 2 4 3 7 5 3 9 5 4 3 10 5 3 11 5 4 3 13 5 3 14 5 4 3 16 5 3 18 5 4 3 20 5 3 22 5 4 3 23 5 3 27 5 4 3 28 5 3 31 5 4 3 32 5 3 33 5 4 3 34 5 3 37 5 4 3 40 5 3 41 5 4 3 42 5 3 43 5 4 3 44 5 3 46 5 4 3 47 5 3 49 5 4 3 50 5 3 53 5 4 3 54 5 3 55 5 4 3 56 5 3 58 5 4 3 59 5 3 61 5 4 3 62 5 3 66 5 4 3 71 5 3 74 5 4 3 77 5 3 78 5 4 3 82 5 3 84 5 4 3 89 7 3 90 7 4 3 92 7 3 99 7 4 3 103 7 3 104 5 4 3 105 5 3 106 5 4 4 2 7 4 3 7 4 4 7 7 4 10 7 4 7 4 11 7 4 17 i 4
185 GMZ ID MS GMZ ID MS INDEX
4 20 7 5 4 9 4 5 5 9 5 6 9 4 5 7 9 5 8 9 4 5 10 9 5 11 9 4 5 12 9 5 17 9 4 5 20 9 5 25 9 4 5 28 9 5 29 9 4 5 33 9 5 32 9 4 5 34 9 5 36 9 4 5 37 9 5 41 9 4 5 43 9 5 45 9 4 5 46 9 5 49 9 4 5 50 9 5 53 9 4 5 55 9 5 58 9 4 5 61 9 5 64 9 4 6 3 12 6 4 12 4 6 9 12 6 13 12 4 6 16 12 6 17 12 4 6 18 12 6 19 12 4 6 20 12 6 22 12 4 6 23 12 6 24 13 4 6 26 13 6 27 13 4 7 1 12 7 4 12 4 7 8 13 7 9 13 4 7 13 13 7 16 13 4 7 17 13 7 19 13 4 7 20 13 7 21 13 4 8 1 9 8 2 9 4 8 3 9 8 4 9 4 8 9 9 8 10 9 4 8 12 9 8 15 9 4 8 17 9 8 18 9 4 8 19 9 8 20 9 4 8 21 10 8 22 10 4 8 23 10 8 27 10 4 8 28 10 8 35 13 4 8 36 13 8 37 13 4 8 38 13 8 39 13 4 8 40 13 8 42 13 4 8 44 13 8 45 13 4 8 46 13 8 47 13 4 8 48 13 8 50 13 4 8 51 13 8 53 13 4 8 55 13 8 56 13 4 8 58 13 8 61 13 4 8 62 13 8 63 13 4 8 64 13 8 66 13 4 8 67 13 8 68 10 4 8 69 13 8 70 13 4 8 71 13 8 73 13 4 8 74 13 8 75 13 4 8 76 13 8 77 13 4 8 79 16 8 81 16 4 8 82 16 8 83 16 4 8 85 16 8 86 16 4 8 87 16 8 89 13 4 8 90 16 8 94 15
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OD -A -A CD CD CD CD CD cD CD 01 CD Ch CD CD cD CD 01 CD cD CD 0 CD CD CD CD CD cD CD CD CD CD CD cn Cn Cn Cn Cn cn Cn cn Cn cn Cn Cn 01 cn cn 01 cn Cn Appendix 6
APPENDIX 6.6
Proportion of Study Area Within Each Geographic Management Zone
GMZ Area (km.) Proportion of Study Area (%)
1 660 23.0 2 1117 39.0 3,D 305 10.7 4 83 2.9 5 237 8.3 6 80 2.8 7 38 1.3 8 346 12.1
189