Biodiversity publications archive

Biodiversity and Fire: The effects and effectiveness of fire management

Proceedings of the conference held 8-9 October 1994, Footscray, Melbourne
Biodiversity Series, Paper No. 8

Biodiversity Unit
Department of the Environment, Sport and Territories, 1996

9. Effects of fuel reduction burning on flora in a dry sclerophyll forest

Kevin Tolhurst,
Fire Research, Dept. Conservation & Natural Resources, Victoria

9.1 Abstract

This study looked at the effects of two successive fuel reduction burns on plant species composition, structure, method of persistence and seasonal growth patterns in a dry sclerophyll footholl forest in north-central Victoria. The effects of burning and spring or autumn were compared.

All species present before burning were present after burning following both spring and autumn burning. Recovery from a second rotation fire in quick succession was slower than after the first rotation. Populations of individual species in long unburnt sites were of mixed age, but after burning were dominated by juvenile individuals. No species relied totally on seedling regeneration, but seedling establishment was more pronounced following autumn fires than after spring fires. The period of vegetative growth after spring burning was longer than the period of growth on unburnt sites and sites burnt in autumn. Neither spring or autumn burning had an irreversible effect in the short term, but frequent rotational burning has the capacity to significantly alter the species and structural diversity of the understorey in these forests.

Key words: fuel reduction, burning effects, sclerophyll forest, understorey flora, fire adaptations, Victoria.

9.2 Introduction

The understorey strata in open forest usually include a combination of shrubs, grasses, sedges and heath species, most of them with fire adaptive traits (Gill 1981). However, many species decrease in abundance after burning and so are disadvantaged by frequent fires, while a few shrubs and graminoids increase (Purdie & Slatyer 1976). Changes in a fire regime, particularly fire frequency, can therefore change the proportion of each species within a community, even though the species complement may remain the same.

This flora project aimed to describe the effects of burning on growth and development of individual species and plants with similar lifeforms within the understorey community. Plant community structure, demographics of selected species, and growing cycles of individual species are being studied in relation to repeated spring and autumn burning treatments and climatic variables. Five fire treatments are being studied and these are being repeated in five study areas within the Wombat State Forest in west-central Victoria. A summary of the results is presented here, but a full account of the methods and results is given in Tolhurst and Oswin (1992).

9.3 Results and discussion

9.3.1 Species composition

No plant species was gained or lost from any treatment. This was also the finding of other studies in similar vegetation (Christensen & Kimber 1975; Wark et al. 1987; Purdie & Slatyer 1976; Bell & Koch 1980). No sclerophyllous plant has ever been reported as having been made extinct as a direct result of burning, but some species have been eliminated from local areas as a result of frequent fires (e.g. mountain ash and alpine ash were eliminated in some areas of the Central Highlands of Victoria when burnt in 1926 and again in 1939). The relative abundance of different species varied with time since burning depending on the rate of development and the method of persistence.

9.3.2 Plant community structure

Plant structure is described for common species or groups of species with similar growth habit. The groups and species used, and their relative dominance, are given in Table 1. A total of 218 species have been recorded across the five FESAs.

The cover, density and height of the eleven plant groups and the total plant cover are considered below.

Total plant cover (understorey)

Total plant cover in the understorey on unburnt plots increased significantly from 27 per cent in 1985 to 44 per cent in 1989, and then appeared to plateau. This increase was predominantly attributable to wire-grass, bracken and tussocks. Herb cover declined over the same period, and most other plant groups remained about the same. This overall increase may be due to a long-term recovery in leaf area following the decade of below average rainfall culminating in the 1982/3 drought. Specht (1983) has shown that projective foliage cover is related to the climatic moisture regime and therefore such an increase in total plant cover could be expected.

Because of the variation in the control treatment with seasonal factors, the changes in the burnt treatments have been compared with the changes in the control. This approach shows the changes due to the fire treatment alone.

Total plant cover returned to pre-burn conditions two to three years after the first rotation spring burning, but there was little recovery within 50 months of first rotation autumn burning. Recovery was also slow within 27 months of the second rotation spring burning.

Table 1: Average cover, density and height of major plant groups in the understorey for control treatments across all study areas (1985-1991)
Plant Groupa Coverb
(%)
Densityc
(plants m-2)
Height
(cm)
Wire-grass 12.4 37.0 52.3
Bracken 9.9 1.2 75.5
Herbs 4.0 140.5 5.0
Tussocks 3.9 2.3 22.2
Poa tussock-grass 2.4 14.1 11.3
Shrubs (0.5 - 4 m) 1.8 0.2 79.9
Trees (>15 m) 1.3 0.3 146.4
Small shrubs (<0.5 m) 0.8 2.3 17.2
Climbers 0.2 0.7 22.5
Geophytes 0.1 0.5 27.4
Small trees (4-15 m) 0.1 0.2 26.2
Other 0.8 - -

Notes:
a Plant groups based on anticipated mature growth form.
b Cover is a measure of projected crowns.
c Density is the number of plants per square metre.

Wire-grass

Wire-grass density remained constant after a single spring fire and increased marginally after autumn burning. The stoloniferous habit of the plant (i.e. the ability to take root at nodes along the stem) meant that density was increased when the plant was fragmented by burning. Seedlings were rarely seen and flowering did not occur in the first four years after burning. Second rotation spring burning reduced density in the following year, possibly due to the death of some of the smaller plants and in the absence of seedling establishment. Height and cover were significantly reduced by burning. Recovery after autumn burning was much slower than after the spring burning.

Bracken

Bracken responded more vigorously to spring than autumn burning, increasing in both frond density and cover (Fig. 1). Bracken burnt in autumn increased in frond density, but was smaller and hence only maintained the cover of the pre-burn population. Burning in either season reduced frond height. This is consistent with Boomsma and Karjalainen (1982) who reported a fourfold increase in density of fronds 12 months after spring burning, but is not totally consistent with Hamilton's (1986) reported fourfold increase in biomass after autumn burning. Ashton (1970) also provided anecdotal evidence of bracken being favoured by autumn burning, but the results presented here and by Veitch (1990) indicate that spring burning also stimulates bracken. The maximum average frond height is determined in part by its edaphic and physical environment; and in part by the energy stored in the rhizome system. Since the edaphic and overstorey environment of the bracken was not greatly affected by burning, the reduction in frond height in the first year may have been due to reduced rhizome reserves; possibly as a result of the fire, extra demands on those reserves from the increased density of fronds, as was found by Preest and Cranswick (1978), and to reduced understorey height. In each subsequent year, as the understorey plants increased in height, the bracken gradually increased in height until the average maximum preburn height was regained.

Figure 9.1: Changes in frond density, cover and height of bracken with time since spring and autumn burning compared with the control treatment.

Figure 9.1: Changes in frond density, cover and height of bracken with time since spring and autumn burning compared with the control treatment.
Herbs

Herb density and cover both consistently declined in the control treatments over the seven years of measurement This trend did not occur on treatments burnt in spring or autumn. Cover of herbs after spring burning took one to two years to return to the level of the control treatment and then exceeded it. Density of herbs in the spring treatment was always as great or greater than the control treatment, but the herbs were not set back at all after autumn burning so that four years after the burning, herb density and cover were both significantly greater than the control. This increase in herb cover after burning was also reported by Kirkpatrick and Dickinson (1984) and Baird (1984). Herb density and cover increased as a result of seedling establishment. This was greatest after autumn burning which also has been reported by others such as Purdie (1977a) and Christensen et al. (1981). The response of herbs to second rotation spring burning was a greater decline in the first year and then a recovery to preburn conditions in the second and third years after the second burn. There was no indication of herb promotion after the second spring fire.

The decline in herb cover and density on the control treatments may be due to an initial abnormally high herb abundance in 1985. This was following the drought of 1982/3 when the tree and shrub canopy had been reduced by the dry conditions; wiregrass, bracken and tussocks cover has increased since that time. This decline has been longer than expected and continues to be a strong trend seven years after the drought.

Tussock

Tussock density, as measured by the number of emergent tillers at ground level, at least doubled compared with the control after both spring and autumn burning within the first year. Two years after spring burning, and four years after autumn burning, density had returned to pre-burn conditions. The second rotation spring burn did not significantly affect density.

The cover of tussocks was the attribute most dramatically affected by burning (Fig. 9.2). One year after both spring and autumn burning, cover was around 40 per cent of the initial level. After four years, tussock cover had returned to around 80 per cent of pre-burn level. During the first two years after the second rotation spring burning, there seemed to be a slower recovery than after the first rotation fires.

Figure 9.2: Increase in tussock grass with time since spring and autumn burning compared with the control treatment.

Figure 9.2: Increase in tussock grass with time since spring and autumn burning compared with the control treatment.

Tussock height was significantly reduced, for 12 months, by both spring and autumn burning and then returned to pre-burn conditions within the second year.

Overall, there was little difference between the effects of a single spring or autumn fire on tussock density, cover and height. Three years after burning, the tussocks had recovered to their original density and height, but cover remained below the pre-burn level four years after burning. The initial impact of a second rotation spring burn was to maintain density without the initial doubling as seen following the first fires. The recovery of height was similar to that following first rotation burning, but cover appeared to be slower to increase.

Poa tussock-grass

A single spring fire tended to increase Poa tussock-grass tiller density and cover and marginally reduce its height. The second spring fire reduced the plant's tiller density, cover and height indicating that the response to repeated burning was different to a single fire. It is postulated that this was due to a loss of regenerative energy, that is, a decrease in the number of shoot buds and carbohydrate, lasting for at least three years following the first fire.

A single autumn burn dramatically increased the tiller density of Poa, but cover and height were reduced. The stimulation of tillers by burning seemed to be greater under autumn conditions than spring conditions, but the regenerative energy was less in autumn, possibly as a result of moisture and temperature stress during the preceding summer and early autumn period or increased grazing pressure by native animals.

Height reduction was greater following autumn burning than after spring burning. This may also have resulted from the increased grazing pressure in autumn due to the palatability of the new shoots at a time when other green fodder was limited. Grazing of new shoots was observed to be common after autumn burning. Increased grazing pressure brought about by the high palatability of fresh shoots after burning may also reduce the regenerative energy of plants as was shown by Leigh and Holgate (1979) in southern New South Wales.

Small shrubs (<0.5m)

The impact of a single spring fire on small-shrub density, cover and height was minimal four years after burning. The recovery in height and cover after autumn burning will take much longer; however in the longer term, the increased density due to the establishment of new seedlings will probably increase the population provided they are not burnt or disturbed for at least six years. Early indications are that the second rotation spring burning had a greater effect than the first rotation, and that recovery will be much slower.

Shrubs (0.5-4m)

Recovery of shrub height and cover was faster following spring burning than after the autumn burning, but there was limited recruitment through burningstimulated seedling establishment and suckering. Autumn burning changed the structure of the shrub layer more dramatically, increasing the number of new plants, but decreasing the height and cover of existing plants. A second rotation spring fire appeared to reduce population levels more than the first rotation spring burning after 27 months, and therefore may have a significant impact in the longer term.

Trees

Small trees have a mature height of between four and 15 m, but only young small trees were measured in this study. The maximum height measured was 4m.

Small trees seemed to be slow growing and significantly reduced in size or killed by burning. Seedling establishment after burning replaced those small trees killed, but the seedlings will take a long time (probably more than 15 years) to grow large enough to survive another fire.

Trees measured in this part of the study have a potential mature height of more than 15 m, but to be included here must have foliage below 2 m or be no taller than 4 m, i.e. be small regrowth trees. A 4 m height limit was used in measurements.

The main effect of burning on trees was to reduce their cover (up to 4 m above the ground). The second rotation spring burning had a greater effect on reducing tree height and cover, indicating that the trees had not fully recovered from the first rotation of burning two or three years earlier. Tree density remained about the same after burning.

Climbers

Climbers were uncommon in this forest so structural data were unreliable. The evidence that was available indicates that autumn burning did not affect the density of the climbers. A similar conclusion was drawn for the effects of spring burning, until a dramatic drop in density three years after burning. The second rotation spring burn more than doubled the density of climbers within one year of being burnt. More observations are needed before these effects can be confirmed.

The height of climbers was reduced for less than three years by spring burning, but was little affected by autumn burning. Second rotation spring burning had a similar effect to the first rotation, but there were indications that the recovery of climbers back to pre-burn height would be slower.

Geophytes

Fluctuations in geophyte density, height, and cover due to seasonal conditions mask the effects of fires. The tendency, if any, was for there to be fewer plants four years after both spring and autumn burning.

9.3.3 Species characteristics

Species characteristics have been classified according to the scheme described by Noble and Slatyer (1980). This scheme has three parts: 1) the method of regeneration (persistence) used by a species after a disturbance such as burning, 2) the environmental conditions required to regenerate, and 3) the length of time taken for a plant to go through each lifestage (juvenile, mature, senescent etc.). Only the method of persistence after low-intensity fire is reported here.

Method of persistence

Sufficient data were collected to enable the classification of 66 out of 106 plant species into their method of persistence after low-intensity burning. The method of persistence, or regenerative response, applies to plants whose aerial parts were completely scorched or burnt, but with the overstorey tree canopy remaining intact after the fire. Regeneration from seed may have been more common if the tree canopy was also completely scorched or burnt. Purdie (1977b) for example, found that all except the geophytic species had some seedling regeneration following a moderate intensity fire (830 to 4200 kW.m-1) in dry sclerophyll forest. A summary of the number of plants in each regenerative category is given in Table 2.

Table 2 Numbers of plant species in the Fire Effects Study Areas using the methods of persistence as defined by Noble and Slatyer (1980)

Table 2: Numbers of plant species in the Fire Effects Study Areas using the methods of persistence as defined by Noble and Slatyer (1980)
Symbol meaning Method of persistence Number
D Seed: dispersed long distances 1
S Seed: stored, maintains viability 2
G Seed: long lived, exhausted after first germination 0
C Seed: short lived, exhausted after first germination 3
V Sprouters: all ages survive 36
U Sprouters: mature remain mature, juvenile remain juvenile 0
W Sprouters: mature remain, juveniles die 13
Y Sprouters: juveniles remain, mature die 0
s Dispersed seed + mature resprout + juvenile ± resprout 4
S Seed store + mature resprout + juvenile ± resprout 7
G seed store with one germination + only mature resprout 0

Understorey plants in this study regenerated primarily by resprouting. Sixty out of the 66 plants classified (91 per cent) used vegetative regeneration to some degree after being completely scorched, and only six (nine per cent) relied totally on seed for regeneration (obligate seed regenerators). However, 26 per cent of plants regenerated by seed to some degree. The proportion of plants in fire prone environments relying on seed regeneration is usually less than those reproducing vegetatively. For example, the proportion of plants regenerating from seed in some other communities were: 31 per cent in Jarrah forest (Bell & Koch 1980), 27 per cent in heath at Wilsons Promontory (Russell & Parsons 1978), 27 per cent in eucalypt woodland near Canberra (Purdie & Slatyer 1976), and 56 per cent in chaparral in California (Hanes 1971).

While obligate seed reproducers are a small proportion of the total, they are potentially the most vulnerable to burning. Three of the six obligate seed reproducers in this study were potentially vulnerable to a single fire since the seed pool was short-lived and exhausted after the first germination; these were thin-leaf wattle, prickly moses, and small poranthera. However, all three species regenerated well after being burnt.

9.3.4 Seasonal growth cycles of selected species

Bracken

In control treatments, bracken sprouts (croziers) appeared between mid-September and the end of November. Burning in spring stimulated the sprouts so that they appeared right through to the February after the fire. In the second and subsequent years, sprout production was similar to the control treatment. Autumn burning stimulated the sprouts to appear during the winter and spring (from June to October) after the fire. Therefore, killing the standing fronds with burning stimulated resprouting as soon as moisture was available, regardless of the time of year.

Frond growth took place between October and March. The first rotation spring burning was followed by a twelve month growth period and the autumn burning was followed by an early start to the growth period in August rather than October. In the second and subsequent years, the frond growth period was similar in burnt and unburnt areas.

Frond mortality normally took place between August and November. After both spring and autumn burning, fronds died over a longer period (July-March) for the first three years after the fires Many fronds produced after burning were quite small and weak and died at times when normal, healthy fronds did not.

In summary, sprouts were produced within eight weeks of burning if there was sufficient soil moisture. The growing period of fronds was extended for
the first year after burning and then returned to normal. Frond death occurred over a longer period for at least three years after burning, probably due to the greater number of weaker fronds and greater frond density.

Narrow-leaf wattle

Shoot growth of narrow-leaf wattle normally occurred over a seven month period between October and April. Burning killed most established shoots so there was no shoot growth after spring or autumn burning until the second year. After the initial dormant period following spring burning, shoot growth occurred almost continuously for the next three years, possibly in response to the additional nutrients made available by the fire or the greater vigour of the new shoots. This extended growing season in the second, third and fourth years after burning did not occur with autumn burning. Second rotation spring burning again did not kill all shoots and so growth on the surviving plants continued normally, after an initial interruption of about ten weeks following the fire.

Sprouts from stem bases or root suckers were not present in the control treatment, but appeared in the first two years after burning. Sprouts seemed to appear sporadically in any season.

Flowering occurred from mid-September to mid-November in the unburnt areas. Autumn burning did not affect the flowering time of surviving mature individuals. No flowering was observed in the springburnt areas for at least four years even though some mature plants survived. This may be due to the increased vigour of the shoot growth after spring burning which may limit flowering. Since this increased vigour was not observed after autumn burning, flowering continued as normal. Narrow-leaf wattle rarely set seed. Seed-set was observed only in unburnt areas and then in summer after flowering.

Shoot mortality was observed only after sprouts appeared. Some sprouts died shortly after being produced. Some older shoots died as a result of burning. Overall, not all mature shoots were killed by the spring and autumn fires. Spring burning increased the period of active shoot growth and autumn burning had no effect. Sprouts were produced after both spring and autumn burning, but not on the unburnt areas. Seedling establishment was not observed and seed-set was rare.

Poa tussock-grass

Poa shoot growth normally occurred in spring from August to November (Fig. 9.3). Spring burning stimulated shoot growth soon after the fire and this growth continued from late spring through the summer. The growth period was longer than normal for two years after the spring and autumn burning, and then returned to normal in the third year. Sprouts were observed only after the existing plants had been burnt. Sprouts appeared within about four weeks of burning regardless of whether the fires were in spring or autumn.

Figure 9.3: Effects of spring and autumn burning on the timing of shoot growth, flowering and seed-setting of Poa tussock-grass.

Figure 9.3: Effects of spring and autumn burning on the timing of shoot growth, flowering and seed-setting of Poa tussock-grass.

Note: "F" indicates the time of burning.

Flowering occurred between mid-November and January. Burning had little effect on flowering time except after the first rotation spring burning when flowering was delayed for about two months. Seed-set followed flowering in late summer/early autumn.

Seedling establishment was uncommon and was observed only in late spring soon after the spring burning. No plants were recorded as having died. However, tillers die each year and new ones replace them nearby, making the recording of the period of mortality very difficult.

Overall, both spring and autumn burning extended the period of shoot growth during the first two years after burning. Sprouts and seedlings grew within two months of all fires. Burning had negligible effect on the timing of flowering and seed-set.

Messmate stringybark

Mature trees in the overstorey were observed in this part of the study. Messmate stringybark grew for most of the year. Growth usually stopped during the winter (June-July) and sometimes during extended dry periods (usually about April). Burning in spring or autumn did not change this pattern. The crowns of messmate stringybark and other trees in the overstorey were rarely visibly affected by the experimental fires.

Flowering occurred in March and April regardless of burning treatment, and was exceptionally heavy in 1987. Flowering started in February in the 2R spring burning treatment, two years after burning. Burning did not significantly affect the observed growth period of messmate stringybark.

Ivy-leaf violet

Ivy-leaf violet normally grew from August to mid-March. Shoot growth continued through the autumn and into the winter for the first year after spring burning. After autumn burning, shoot growth took place only during the normal spring and summer period. Establishment of seedlings and sprouts was not observed in the control treatment, but did occur soon after spring and autumn burning.

Flowering and seed-set took place during late spring and summer. Burning in spring or autumn did not affect this pattern, except that there was no observed seed-set after the first flowering in the spring burning treatment and no flowering or seed-set in the first year after second rotation spring burning. Spring burning, therefore, stopped seed-set in the year after burning, but extended the shoot growing period. Periods of sprouting and seedling establishment occurred soon after both spring and autumn fires.

9.3.5 Population dynamics

Population age structure has been studied so that computer simulation models can eventually be used to predict the changes likely to occur under different fire and climatic regimes.

Population dynamics of the major understorey species were monitored annually in summer on small plots. Poa tussockgrass and wiregrass were monitored on 1 m² plots, and bracken, silvertop wallabygrass, thin-leaf wattle, hop wattle, and prickly moses were monitored on 4 m² plots. Each plant within a plot was tagged or pinned to identify the stage of development and the year that stage was attained. Stages of development were classified
as follows:

Bracken

In the control treatment, the frond population structure of bracken was relatively constant. Approximately equal numbers of senescent and mature fronds were present at each assessment (in December) and a few sprouts (croziers) were counted. This same trend was evident after the first rotation spring and autumn burning treatments with two variations: first the number of the fronds were two to three times greater; and second there was a pronounced peak in mature frond abundance in the first year after autumn burning. Following the second rotation spring burning, there was a peak in immature fronds at the time of assessment, about two months after the burning. Therefore burning affected the frond population structure only for the first two years. This is discussed in greater detail in Tolhurst (1990).

Silvertop wallaby-grass

Wallaby-grass populations were dominated by sprouts (i.e. plants not known to have flowered) in the unburnt and spring burnt treatments. Flowering of mature and previously designated sprout individuals was recorded in the second year after both spring and autumn burning; but was most pronounced after the autumn burning. Only one individual was recorded flowering in the control treatment during six years of observations.

Poa tussock-grass

Populations of Poa were dominated by sprouts. A small proportion of the population flowered each year regardless of whether or not it was burnt. The proportion of flowering and non-flowering mature plants remained approximately the same. Observations suggested that mature individuals tended to flower every second year so that there was a regular exchange between the status of flowering and non-flowering each year.

Silver wattle

Unfortunately, only one specimen of silver wattle was present in the control treatment and it died after the first year. Only sprouts were present after burning in spring or autumn. Mature, senescent and seedling plants present before burning were either killed or reduced to numerous sprouts which generally arose from roots near the surface.

Narrow-leaf wattle

In the control treatment, sprout, mature and senescent plants, both flowering and not, were present. During the six years of observation, the populations of narrow-leaf wattle had aged until there were no longer any sprouts within the plots and the proportion of senescent plants had increased. In the burnt treatments the populations were predominantly sprouts arising from the roots or the stem base, with a few seedlings present in some areas (Fig. 9.4).

Figure 9.4: Simplication of the age structure of narrow-leaf wattle populations after spring and autumn burning treatments compared with the control treatment

Figure 9-4: Simplication of the age structure of narrow-leaf wattle populations after spring and autumn burning treatments compared with the control treatment
Hop wattle

As with narrow-leaf wattle, hop wattle populations aged so that mature plants became senescent in the control treatment. No seedlings established within the plots burnt in spring, even though seedlings were common elsewhere in the same study areas, but large numbers of seedlings did establish after autumn burning. The first rotation spring burning was not intense enough to kill the mature plants being studied. These plants continued to flower and became senescent three years after the fires. All mature and senescent plants were burnt in the second rotation spring burning, but there was still no seedling establishment within the study plot. The population after the second spring burning consisted entirely of sprouts. A few sprouts were also present after the autumn burning, but the population was predominantly seedlings. These seedlings were still dominant four years after burning.

9.4 Conclusions

All species present in the understorey plant community before burning were still present following both spring and autumn burning. Fire has been a part of this ecosystem for thousands of years and all species had regeneration strategies to cope with periodic fire disturbance. The structure of the understorey was modified by burning for at least four years, predominantly because of the reduced height of the non-herbaceous plants such as small-trees, shrubs and wire-grass, but also because of reduced cover after autumn and second rotation spring burning.

Recovery from second rotation spring burning was slower than after the first rotation; this effect can be partially attributed to seasonal affects (Tolhurst 1992). But it is postulated that the main effect was caused by a reduction in the regenerative reserves of the plants following the first fires, and that these reserves take more than three years to be replenished. Repeated burning may therefore significantly deplete regenerative reserves and result in species loss if fires are more frequent than the time needed for plants to fully recover from the effects of being burnt.

Populations of wattles and perennial grasses were of mixed age before burning, but were dominated by sprouts or seedlings after burning. Thus burning simplified the age structure of these populations. However, the population age structure of bracken fronds was little affected because of the relatively short life-span of individual fronds. Seedling establishment, when it occurred, was more pronounced after autumn burning than spring burning. No species relied totally on seedling establishment for survival. Seedling regeneration was often supplemented by resprouting plants or a small proportion of the pre-burn population that remained unburnt.

Resprouting was most vigorous after first rotation spring burning. The period of shoot growth was extended after spring burning, but not affected by autumn burning. Total plant cover returned to preburn levels within three years of a single spring fire.

While there were qualitative and quantitative differences between the effects of single spring and autumn low-intensity fires, neither had any irreversible effect on the understorey plants. However, frequent repeated fires are likely to alter significantly the species diversity and structure of plant communities studied here; and this may be a legitimate management objective in some cases. This is the subject of continuing research in the Wombat State Forest where short and long rotational burning in both spring and autumn is under investigation. The findings also highlight the need for long-term studies of repeated burning at varying frequencies if the true effects of repeated fuel reduction burning are to be identified.

9.5 Acknowledgements

I would like to acknowledge the significant effort in collecting the data reported on here, made by the technical staff at the Creswick Forest Research Station, especially Don Oswin, Amanda Ashton, Chris Norman, Kevin Brooker, Peter Novotny, and Tony Morris.

9.6 References

Ashton, D.H. 1970, 'Fire and Vegetation', in Second Fire Ecology Symposium, Monash University, Melbourne.

Baird, A. 1984, 'Observations in Kings Park', in The Management of Small Bush Areas in the Perth Metropolitan Region, ed. S.A. Moore, Seminar, Department Fisheries & Wildlife, Perth. pp. 18-20.

Bell, D.T. & Koch, J.M. 1980, 'Post-fire succession in the northern Jarrah forest of Western Australia', Australian Journal of Ecology, vol. 5, pp. 9-14.

Boomsma, D.B. & Karjalainen, U. 1982, 'The control of perennial weeds, grasses and braken fern for radiata pine plantation establishment, part 2 bracken fern control', in Proceedings Workshop on Establishment of Coniferous Plantations , Sept 1982, Mt Gambier, South Australia.

Christensen, P., Recher, H. & Hoare, J. 1981, 'Response of open forests (dry sclerophyll forests) to fire regimes', in Fire and the Australian Biota, eds. Gill, A.M. Groves, R.H. & Noble, I.R., Australian Academy of Science, Canberra, pp. 367-393.

Christensen, P.E. & Kimber, P.C. 1975, 'Effect of prescribed burning on the flora and fauna of south-west Australian forests', Proceedings Ecology Society of Australia, vol. 9, pp. 85-106.

Gill, A.M. 1981, 'Adaptative responses of Australian vascular plant species to fires', in Fire and the Australian Biota, eds. Gill, A.M. Groves, R.H. & Noble, I.R. Australian Academy of Science, Canberra. pp. 243-272.

Hamilton, S.D. 1986, The effects of fuel reduction buring on biomass and nitrogen in Eucalyptus obliqua L'Herit forest, Master Applied Science thesis, Royal Melbourne Institute of Technology, Melbourne.

Hanes, T.L. 1971, 'Succession after fire in the chaparral of southern California', Ecology Monograph, vol. 41, pp. 27-52.

Kirkpatrick, J.B. & Dickinson, K.J.M. 1984, 'The impact of fire on Tasmanian alpine vegetation and soils', Australian Journal of Botany, vol. 32,
pp. 613-629.

Leigh, J.H. & Holgate, M.D. 1979, 'The responses of the understorey of forests and woodlands of the southern tablelands to grazing and burning', Australian Journal of Ecology, vol. 4, pp. 25-45.

Noble, I.R. & Slatyer, R.O. 1980, 'The use of vital attributes to predict successional changes in plant communities subject to recurrent distances', Vegetation, vol. 43, pp. 5-21.

Preest, D.S. & Cranswick, A.M. 1978, 'Burn-timing and bracken vigour', Proceeding 31st N.Z. Weed and Pest Control Conference, New Plymouth, New Zealand, pp. 69-73.

Purdie, R.W. 1977a, 'Early stages of regeneration after burning in dry sclerophyll vegetation I. Regeneration of the understorey by vegetative means', Australian Journal of Botany, vol. 25, pp. 21-34.

Purdie, R.W. 1977b, 'Early stages of regeneration after burning in dry sclerophyll vegetation II. Regeneration by seed germination', Australian Journal of Botany, vol. 25, pp. 35-46.

Purdie, R.W. & Slatyer, R.O. 1976, 'Vegetation succession after fire in sclerophyll woodland communities in south-eastern Australia', Australian Journal of Ecology, vol. 1, pp. 223-236.

Russell, R.P. & Parsons, R.F. 1978, 'Effects of time since fire on heath floristics at Wilson's Promontory, southern Australia', Australian Journal of Botany, vol. 26, pp. 53-61.

Specht, R.L. 1983, 'Foliage projective covers of overstorey and understorey strata of mature vegetation in Australia', Australian Journal of Ecology, vol. 8, pp. 433-439.

Tolhurst, K.G. 1990, 'Response of bracken to intensity prescribed fire in open eucalypt forest in west-central Victoria', in Bracken Biology and Management, eds. J.A. Thomson & R.T. Smith, Australian Institute of Agricultural Science, Sydney, pp. 53-62.

Tolhurst, K.G. 1992, 'Climate and growing season in the fire effects study areas – Wombat State Forest', Department Conservation & Environment, Victoria, Forest Research Report, no. 349,

Tolhurst, K.G. & Oswin, D.A. 1992, 'Effects of spring and autumn low intensity fire on understorey vegetation in open eucalypt forest in west-central Victoria', Department Conservation & Environment, Victoria, Forest Research Report, no. 349

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Wark, M.C., White, M.D., Robertson, D.J. & Marriott, P.F. 1987, 'Regeneration of heath and heath woodland in the north-eastern Otway Ranges following the wildlife of February 1983', Proceedings from the Royal Society of Victoria, vol. 99, pp. 51-88.

9.7 Appendix 1

Common and scientific names of plant species mentioned in this summary report.

Species in brackets are mentioned in the report, but do not occur in the study areas.

Many additional species occur in the study areas, but are not mentioned in this summary report.

[Alpine ash] Eucalyptus delegatensis R. Baker
Australian clematis Clematis aristata R.Br. ex DC.
Bidgee widgee Acaena anserinifolia (J.R. & G. Forster) Druce
Black wattle Acacia mearnsii De Wild.
Blackwood Acacia melanoxylon R.Br.
Bracken Pteridium esculentum (G.Forster) Cockayne
Candlebark Eucalyptus rubida Deane & Maiden
Common lagenifera Lagenifera stipitata (Labill.) Druce
Common raspwort Gonocarpus tetragynus Labill.
Crane's bill Geranium potentilloides L'Herit.
Fireweed Senecio minimus Poiret
Flatweed Hypochoeris radicata L.
Hedge wattle Acacia paradoxa DC.
Hop wattle Acacia stricta (Andrews) Willd.
Ivy-leaf violet Viola hederacea Labill.
Long-leaf box Eucalyptus goniocalyx F. Muell ex Miq.
Messmate stringybark Eucalyptus obliqua L'Herit
[Mountain ash] Eucalyptus regnans F. Muell.
Narrow-leaf peppermint Eucalyptus radiata Sieber ex DC.
Narrow-leaf wattle Acacia mucronata Willd. ex H.H. Wendl.
Poa tussock-grass Poa sieberiana Sprengel
Prickly moses Acacia verticillata (L'Herit) Willd.
Prickly tea-tree Leptospermum juniperinum Smith
Prickly woodruff Stellaria pungens Brongn.
Silver wattle Acacia dealbata Link
[Silvertop] Eucalyptus sieberi L. Johnson
Silvertop wallaby-grass Chionochloa pallida (R.Br.) S.W.L. Jacobs
Small poranthera Poranthera microphylla Brongn.
Tall sword-sedge Lepidosperma elatius Labill.
Thin-leaf wattle Acacia aculeatissima Macbr.
Trailing goodenia Goodenia lanata R. Br.
Wattle mat-rush Lomandra filiformis (Thunb.) Britten
Wire-grass Tetrarrhena juncea R. Br.