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Australian Journal of Botany, 2007, 55, 433–438

Can age be predicted from diameter for the obligate seeder Allocasuarina littoralis (Casuarinaceae) by using dendrochronological techniques? Alana L. BurleyA,D , Stephen PhillipsA and Mark K. J. OoiB,C A

School of Environmental and Applied Sciences, Griffith University, PMB 50 Gold Coast Mail Centre, Qld 9726, Australia. B Institute for Conservation Biology, School of Biological Sciences, University of Wollongong, NSW 2522, Australia. C Biodiversity Conservation Science Section, Policy and Science Division, Department of Environment and Conservation (NSW), PO Box 1967, Hurstville, NSW 2220, Australia. D Corresponding author. Present address: School of Anthropology, Geography and Environmental Studies, The University of Melbourne, 221 Bouverie St, Carlton, Vic. 3010, Australia. Email: [email protected]

Abstract. In fire-prone regions, assessing stand age of obligate-seeding species provides an estimate of time since last fire. If a relationship exists between tree age and diameter, measuring the stem diameter of trees is a simple field method for determining age-class distribution within a stand. In this study, we examined whether age of the obligate seeder Allocasuarina littoralis could be estimated from diameter by using dendrochronological applications. Analysis of radial samples established that A. littoralis puts down annual growth rings. The relationship between the number of growth rings and stem diameter was tested for both male and female stems by using regression analysis. For female plants, this relationship varied significantly between sites. In contrast, male stems provided a strong relationship between age (as a function of the number of growth rings) and diameter, regardless of site. A regression model estimating age from stem diameter, based on male trees only, was subsequently developed and tested with data collected from trees of known age. Predicted estimates from stem diameter were within 3.76 years of the true age. Field measures of stem diameters can therefore provide a tool for estimating the fire history, especially time since last fire, in areas where stands of this species occur.

Introduction In many areas fire is a recurrent landscape disturbance and subsequently plays a pivotal role in plant population dynamics (Whelan 1995). Historical fire data are an essential ingredient for accurate ecological interpretations. Although the boundaries and timing of most major fires are recorded, many smaller or less destructive fires may go unrecorded. These fires can nevertheless be ecologically important (Banks 1991). Similarly, unburnt patches at both large and small scales may occur within large fire boundaries (Clark et al. 2002; Ooi et al. 2006). Because of this, vegetation within the landscape may have a more complex age structure than mapped fire boundaries would suggest. For a full understanding of population ecology, as well as for informed fire management, effective field-sampling methods with widespread applicability are required to accurately determine the fire history of a site. Assessing the age-class distribution of species that have the majority of adult plants killed by intense fire, known as obligate seeders, can help determine the fire-disturbance history of a population. For such species, recruitment is predominantly linked to fire and as a result, cohorts will be related to fire © CSIRO 2007

episodes (Whelan 1995). Because monitoring the growth of long-lived perennial plants is not practicable, the development of simpler methods is required to estimate plant age. Recent studies have shown that counting growth whorls of obligate-seeding Banksia species provides one possible method for assessing time since last fire (Wills 2003; Jenkins et al. 2005). Another simple, non-destructive method proposed in our study, is to measure tree stem diameter. The accuracy of this method is dependent on the existence of a relationship between stem diameter and tree age, which is species specific. Although there are many examples of reliable correlations between stem diameter and tree age in non-tropical climate zones (e.g. Taylor et al. 1996; Singer and Burgman 1999; Rozas 2003, 2004), there are relatively few from tropical and subtropical climates. An absence of seasonality, one of the main reasons for a lack of well defined annual growth rings (Jacoby 1989), may in part be the reason for fewer tropical examples. However, tree species from regions that experience a consistent annual dry season grow only, or predominantly, during the following wet season, irrespective of seasonal temperatures (Ogden 1981; Boninsegna et al. 1989; Worbes 1995; Grau et al. 10.1071/BT06160

0067-1924/07/040433

Australian Journal of Botany

(1) do annual growth rings occur in A. littoralis and is the species suitable for dendrochronological study? and (2) is there a relationship between stem diameter and age, and can an accurate age–diameter model be developed? Materials and methods Study sites The study was conducted in fire-prone coastal vegetation in eastern Australia. Fire is the predominant natural disturbance in the region, with return intervals within the range of 15–30 years (Watson and Wardell-Johnson 2004). Two study sites comprising A. littoralis stands were used to obtain radial samples and cores from individual trees. The Southport site, in southeastern Queensland (E537452 N6906509 ± 7.1 m; datum AGD66), consisted of regenerating open forest dominated by Eucalyptus spp. with a substrate predominantly of lownutrient free-draining podzolics. The Tugun site, ∼20 km further south and just over the state border in northern NSW (E549200 N6883700 ± 9.0 m; datum AGD66), is an open forest similarly dominated by Eucalyptus spp. and Melaleuca spp., with regenerating rainforest on a substrate consisting predominantly of similarly low-nutrient Quaternary sand. The Southport site experienced two recent fires in relatively quick succession in 1993 and 2003 (N. Currie, pers. comm.), whereas the Tugun site last experienced fire c. 1981 (D. Boyd, pers. comm.). Climatic data were obtained from the Bureau of Meteorology for weather stations located at Southport and Coolangatta (the closest station to the Tugun site). The study region is subtropical and experiences an annual winter dry season of 2–3 months (July–September), with an average monthly rainfall of between 35.9 and 57.9 mm. The highest rainfall was received in the summer to early autumn period (December–April), with average monthly rainfall between 130.5 and 224.5 mm (Fig. 1).

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2003). Annual growth rings reflecting the annual rainfall cycle are subsequently produced. The use of tree rings has been broadly applied in ecological studies for determining tree ages and investigating changes in growth rates and deducing their causes (Norton et al. 1987; Boninsegna et al. 1989; Worbes et al. 2003). Age measurements have often been used to determine the age-class distribution of a tree population from which inferences on the dynamics of that population are drawn (Norton et al. 1987; Rozas 2004). Studying tree-ring chronologies coupled with stand and age structures, land-use history, climatic data and ecological attributes of individual species has proven to be a particularly useful approach for understanding forest dynamics (Ruffner and Abrams 1998; Pollmann 2003; Rozas 2004; Piovesan et al. 2005). In the present study, we investigated whether the age of the widespread species Allocasuarina littoralis (Salisb.) L. Johnson can be predicted from diameter by using dendrochronological applications. If a relationship between age and diameter exists, the diameter of the obligate-seeding A. littoralis could be used to determine age-class distribution, and subsequently fire-disturbance history, for a large area of fire-prone eastern Australia. Specifically, the questions posed in this study were as follows:

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Month Fig. 1. Average monthly rainfall for Coolangatta (solid bars, left axis) and average daily temperature (dashed line, right axis). Very similar averages were also obtained from the Southport weather station (data not presented).

Study species Allocasuarina littoralis was used in this study primarily because it is a serotinous obligate-seeding species (Gill and Bradstock 1992; Melville 1995; Morrison 1995) with a widespread distribution. Seed release in serotinous species is normally triggered by fire and seeds subsequently germinate during the first favourable period (Cowling and Lamont 1987). Allocasuarina species in general appear to be strongly serotinous (Pannell and Myerscough 1993; C. M. Pickering, pers. comm.) and the fire-stimulated seed release results in mass establishment of seedlings in the following year (Whelan 1995). Such a response to fire makes A. littoralis an ideal candidate for developing a simple field measure of population dynamics using an age–diameter model. Additionally, the widespread distribution of the species increases the applicability of any potential model produced, covering a linear range of over 2000 km of fire-prone coastal habitat. Collection of radial wood samples and cores Following the protocols detailed by Fritts (1976) and Ogden (1978), trees were selectively sampled at each site, using either increment cores (Suunto 5 mm Increment Borer) and/or radial samples. Radial samples were obtained only from trees that had fallen within the last 6 months, had no evidence of growth and were presumed dead. As dead stems were used, there were incidences of rotten wood and at both sites additional radial samples were taken to account for this in order to obtain a representative sample. These samples also represented the range of size classes present within the site, which was determined by visual site inspection. Each tree selected was measured (± 2 mm) for its diameter at breast height over bark (dbh) at 1.3 m with a diameter tape. The core and radial samples obtained from the tree were then taken at this height. Each stem was also sexed by the presence or absence of cones. A minimum stem diameter of 25 mm was selected to ensure trees had reached reproductive status.

Predicting age from diameter for A. littoralis

Sample preparation Once the core was removed from the tree it was stored within a cylindrical paper bag, similar to the size of the core. Cores were air-dried and then mounted for sanding and surfacing. Both core and radial samples were sanded with a disc sander attached to an electric drill or a belt sander, and generally starting with coarse sandpaper (40 grit), and then proceeding to very fine sandpaper (400 or 600 grit) (McBride 1983). Slicing the surface of increment cores with a single-edge razor blade or knife further improved surfaces for ring counting (McBride 1983). To further enhance the rings, both the core samples and radial samples were stained with a mixture of one candle melted in 500 mL of mineral turpentine (S. Wild, pers. comm.) and left to dry for 24 h at room temperature. Growth rings In total, 23 radial and 23 core samples from individual trees were collected from the Tugun site and 21 of each sample type from the Southport site. After sample preservation the rings were counted visually or with the aid of a ×10 optical glass binocular magnifier (Opti-VISOR). The use of radial samples as opposed to core samples allowed wedging rings to be more accurately identified as those that did not persist around the radial extent. Missing or false rings were more difficult to detect; however, cross-dating tree-ring series, the only accurate detection method, was beyond the scope of this study. Growth rings were counted along four radii (where possible, depending on the deterioration of the wood) of each radial sample and the lowest number of growth rings was used in the analysis to account for missing and false rings. As for several other studies, linear regression was used to develop the age–diameter model as this provided the best statistical and graphical fit for all tested variations of the model (Armesto et al. 1992; Rozas 2003, 2004). The line of fit that best explained the relationship between diameter and age was determined. Analysis of covariance (ANCOVA) was then used to ascertain any differences in the age–diameter relationship that may have been attributable to gender and/or site location. Trees of known age A sample of trees of known age in the median strip along the Chinderah bypass section of the Pacific Highway in the Tweed area of far-northern NSW (within 20 km of the Tugun site) were recorded for gender and measured for dbh. This was done both to test the age–diameter model developed and to obtain a correction factor for more accurate age determination. Trees growing on the Chinderah bypass were progressively planted from 1994 to 1996 on a substrate of Quaternary sand. Subsequently, tree age was based on the known timing of planting. It was assumed that growth rates were similar to the other study sites and that trees were at least 2 years old before planting; this placed them in an age range of between 9 and 11 years at the time of study, for which the mean age is 10 years. The dbh measurements of the male trees were inserted into the equation for the lowest number of growth rings and a mean value of age and dbh was calculated with 95% confidence intervals. The difference between the mean known age and the mean predicted age based on the ring counts was subtracted from the y-intercept of the


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equation. This intermediate equation was then applied to the mean and 95% confidence intervals for the dbh values of the trees of known age and was passed through zero on both the x- and y-axis. This corrected model was regarded as the working-model equation that best explained the relationship between diameter and age of A. littoralis. Results Core samples v. radial samples Cursory examination of 24 increment cores after sample preparation indicated several shortcomings of using cores in this analysis. This was due to the difficulty of accurately identifying growth rings, asymmetry of the growth rings and the capacity of the increment borer to miss the chronological centre of the tree. Because the core samples did not provide a clear enough account of the presence of growth rings, it was decided that subsequent measurements and analyses be based solely on the radial samples. Age–diameter relationships Radial samples obtained from the Tugun site established that female stems were initially smaller in size than males with the same number of growth rings. This trend reversed at ∼100 mm dbh, with females becoming larger in size than males of the same age (Fig. 2a). The age–diameter relationship between male and female stems from the Tugun site was significantly different (F = 17.068; P = 0.001). Growth patterns between genders for the Southport site followed a similar trend as that for the Tugun site, albeit to a lesser degree (Fig. 2b), but were not significantly different (F = 0.771; P = 0.392). As there were significant gender differences, site effects were analysed separately for males and females. For the female age– diameter relationship, ANCOVA found a significant difference between sites (F = 9.900, P = 0.007) (Fig. 3a). There were no significant site effects for the male age–diameter relationship (F = 0.459, P = 0.505) (Fig. 3b). Owing to inconsistency of the age–diameter relationship among female stems, an age–diameter model was developed for male stems only. The model developed for age (A) and diameter (d) was as follows: A = (0.099 ± 0.011) × d + (4.347 ± 1.250). Trees of known age Male trees of known-age (n = 13) were calculated to have a mean dbh of 95.15 ± 10.09 mm (95% CI). The difference between the mean known age and the mean predicted age derived from the model above is 3.76 years, resulting in an intermediate equation A = (0.099 ± 0.011) × d + (0.587 ± 1.251). The application of the intermediate model to the mean and 95% confidence intervals of the trees of known age provided the following final, corrected age–diameter model for male trees: A = (0.105 ± 0.003) × d + (0.013 ± 0.261). This, in turn, provided a corrected mean age with 95% confidence intervals (Table 1).

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Diameter at breast height (mm) Fig. 2. Growth-pattern variation exhibited by male and female Allacasuarina littoralis, as shown in radial samples, at (a) the Tugun site, females ( with a solid line, n = 9, r2 = 0.953) and males (䊏 with a dashed line, n = 14, r2 = 0.897); and (b) the Southport site, females ( with a solid line, n = 10, r2 = 0.939) and males (䊏 with a dashed line, n = 11, r2 = 0.959).

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Discussion Providing simple field methods to accurately estimate time since last fire is important for areas where fire history is not known (Wills 2003; Jenkins et al. 2005). This study set out to assess the suitability of the obligate seeder A. littoralis for predicting age from stem diameter, by using dendrochronological techniques, to ascertain its potential as one such field method for eastern Australia. A strong relationship was found between age and stem diameter, and an accurate predictive model was developed for estimating age. In addition to the age–diameter model, this study also provided one further example of a subtropical species that is suitable for dendrochronological study. Climatic data from the study region indicated that rainfall patterns were strongly seasonal. The winter dry season, consisting of average monthly rainfall levels below 60 mm, followed by a regular wet season during summer and early autumn, provided conditions appropriate for annual growth ring production. Evidence from other studies has shown that similar conditions promote growth-ring production in other tropical regions (Ogden 1981; Boninsegna et al. 1989; Jacoby 1989; Worbes 1995; Grau et al. 2003). The age–diameter relationship was determined by growthring counts from radial samples. The efficacy of a relationship between tree age and stem diameter is one that has been examined by many studies with varying results. Although some have

Fig. 3. Variation in the number of growth rings attributed to site location for (a) female stems, Southport site ( with a solid line, n = 10, r2 = 0.939), Tugun site (䊏 with a dashed line, n = 9, r2 = 0.953); and (b) male stems, Southport site ( with a solid line, n = 11, r2 = 0.959), and Tugun site (䊏 with a dashed line, n = 14, r2 = 0.897).

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indicated that a strong relationship can exist between stem diameter and tree age (e.g. Armesto et al. 1992; Taylor et al. 1996; Singer and Burgman 1999; Rozas 2003, 2004), there can be large intraspecific variation in the age–size relationship, particularly for tropical trees (Martin and Moss 1997; Worbes et al. 2003; Brienen and Zuidema 2006). Although the results from our study presented a strong age–diameter relationship for the subtropical species A. littoralis, with little intraspecific variation, this relationship was affected by differences between both gender and site characteristics. The age–diameter model developed was based on male plants only, owing to the consistent age–diameter relationship found between sites. Significant differences existed both between male and female plants, and between sites for female plants. The differential allocation of resources to reproduction and vegetative growth by male and female plants may lead to differences in growth patterns. At the Tugun site, females of the same age as males were initially smaller in size. However, once stem diameters exceeded 100 mm, this trend reversed and females were larger than males of the same age. Females may have to achieve a greater size before flowering, owing to higher expenditure on resources for reproduction, than males (Delph 1999) and, as a result, the average size of flowering female plants in a population may be greater than that of flowering males (Delph 1999; Pickering 2000). Delph and Meagher (1995) found that, at maturity, female plants of Silene latifolia produced more vegetative growth and put more biomass into reproduction

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Table 1. Mean diameter at breast height (dbh) and estimated age in years (± 95% confidence intervals) of the trees of known age determined using the initial age-diameter model and the subsequent estimated age as calculated by the corrected age-diameter model Parameter Mean Dbh (mm) Age (years)

95.15 13.76

Initial age-diameter model Lower 95% CI Upper 95% CI 85.06 12.76

105.25 14.76

than did males. Although not assessed in our study, 100 mm may be a size-class threshold that coincides with the time that female A. littoralis have established themselves reproductively. Once established, females may be able divert more resources to vegetative growth, resulting in a larger size than male plants of the same age. It is not certain as to why the same pattern did not exist for female plants at the Southport site. Both sites are in close proximity to each other, with similar climates, vegetation structures and nutrient-poor soils. The only identifiable difference found between sites was the more frequent and recent fire disturbance experienced at Southport. Several factors associated with more frequent fire may affect growth, gender specifically. Houssard et al. (1994) concluded that allocation of resources to sexual reproduction by females of the dioecious Rumex acetosella made them more sensitive to environmental change, and to variation in nutrient levels, than male plants. Gehring and Monson (1994) also found that for Silene latifolia, females were often more negatively affected than males when both sexes were growing in the same stressful environment. Taking these findings into account, the higher level of fire disturbance experienced at the Southport site may have had a greater negative impact on female plants than males, subsequently reducing the variation in size between the sexes. Although it is unlikely that there is a uniform effect of fire disturbance on the age–diameter relationships (cf. Singer and Burgman 1999), further investigations on a larger scale are required to determine whether the trends found in our study are evident in other populations of A. littoralis. One of the main problems often associated with using growth rings to study population dynamics of trees is that the estimated age may vary considerably from the true age (Norton et al. 1987; Baker 2003). For A. littoralis, the age–diameter model was tested with trees of known age from the Chinderah bypass, with the calculated age within 3.76 years of the true age. This was considered to be a relatively accurate estimate. Eshete and St˚ahl (1999) found deviations ranging from −3 to +3 for the number of rings counted in trees with known age, which they attributed to missing or false rings. It is possible that missing or false rings are also found in samples from A. littoralis; however, it is not considered a large enough difference to indicate regular sub-annual rings. The age–diameter model developed for male A. littoralis stems (A = (0.105 ± 0.003) × d + (0.013 ± 0.261)) provides a good estimate of age from a measure of stem diameter and thus provides a simple field method for determining age-class distribution. Although the model has been developed with male stems only, this would not diminish its capacity as a field tool. In the field, male stems of A. littoralis are easily distinguishable owing to persisting cones found only on female stems.

Mean – 10.00

Corrected age-diameter model Lower 95% CI Upper 95% CI – 8.94

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Since A. littoralis is an obligate seeder, the model may provide a useful tool for elucidating the fire history of areas where stands of this species occurs. Coastal habitats in eastern Australia are particularly fire-prone and fire mapping is often either unavailable, or imprecise at smaller scales (Wills 2003), necessitating the need for such a field tool. Fire-return intervals, and subsequently A. littoralis tree age, are generally less than 30 years in this region, and predictions from the model are not based on large extrapolations. This further increases the accuracy of the model for estimating age. The widespread distribution of A. littoralis, potentially makes this model applicable for much of the coastal fire-prone regions in eastern Australia. Acknowledgements Thanks go to Nick Currie, Brenton Hunt and Vaughn Penfold for their help with sample collection and to the Griffith University OTS staff for their helpful advice and procuring the required materials. A Burley received financial support from a Patience Thoms Honours Scholarship from Griffith University during this study. Two anonymous reviewers provided valuable and constructive comments to the improvement of the manuscript. Thanks go also to Felicia Pereoglou, Samantha Ward and Marama Hopkins for their assistance in the field.

References Armesto JJ, Casassa I, Dollenz O (1992) Age structure and dynamics of Patagonian beech forests in Torres del Paine National Park, Chile. Vegetatio 98, 13–22. doi: 10.1007/BF00031633 Baker PJ (2003) Tree age estimation for the tropics: a test from the southern Appalachians. Ecological Applications 13, 1718–1732. Banks JCG (1991) A review of the use of tree rings for the quantification of forest disturbances. Dendrochronologia 9, 51–70. Boninsegna JA, Villalba R, Amarilla L, Ocampo J (1989) Studies on tree rings, growth rates and age-size relationships of tropical tree species in Misiones, Argentina. International Association of Wood Anatomists Bulletin 10, 161–169. Brienen RJW, Zuidema PA (2006) Lifetime growth patterns and ages of Bolivian rain forest trees obtained by tree ring analysis. Journal of Ecology 94, 481–493. doi: 10.1111/j.1365-2745.2005.01080.x Clark JS, Gill AM, Kershaw AP (2002) Spatial variability in fire regimes: its effects on recent and past vegetation. In ‘Flammable Australia: the fire regimes and biodiversity of a continent’. (Eds RA Bradstock, JE Williams, AM Gill) pp. 199–237. (Cambridge University Press: Cambridge, UK) Cowling RM, Lamont BB (1987) Post-fire recruitment of four cooccurring Banksia species. Journal of Applied Ecology 24, 645–658. doi: 10.2307/2403899 Delph LF (1999) Sexual dimorphism in live history. In ‘Gender and sexual 9 dimorphism in flowering plants’. (Eds MA Geber, TE Dawson, LF Delph) pp. 149–173. (Springer-Verlag: Berlin) Delph LF, Meagher TR (1995) Sexual dimorphism masks life history trade-offs in the dioecious plant Silene latifolia. Ecology 76, 775–785. doi: 10.2307/1939343

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Eshete G, St˚ahl G (1999) Tree rings as indicators of growth periodicity of acacias in the Rift Valley of Ethiopia. Forest Ecology and Management 116, 107–117. doi: 10.1016/S0378-1127(98)00442-3 Fritts HC (1976) ‘Tree rings and climate.’ (Academic Press: London) Gehring JL, Monson RK (1994) Sexual differences in gas exchange and response to environmental stress in dioecious Silene latifolia (Caryophyllaceae). American Journal of Botany 81, 166–174. doi: 10.2307/2445630 Gill AM, Bradstock RA (1992) A national register for the fire responses of plant species. Cunninghamia 2, 653–660. Grau HR, Easdale TA, Paolini L (2003) Subtropical dendroecology dating disturbances and forest dynamics in northwestern Argentina montane ecosystems. Forest Ecology and Management 177, 131–143. doi: 10.1016/S0378-1127(02)00316-X Houssard C, Thompson JD, Escarré J (1994) Do sex-related differences in response to environmental variation influence the sex-ratio in the dioecious Rumex acetosella? Oikos 70, 80–90. doi: 10.2307/3545702 Jacoby GC (1989) Overview of tree-ring analysis in tropical regions. International Association of Wood Anatomists Bulletin 10, 99–108. Jenkins ME, Morrison DA, Auld TD (2005) Use of growth characteristics for predicting plant age of three obligate-seeder Proteaceae species. Australian Journal of Botany 53, 101–108. doi: 10.1071/BT04067 Martin DM, Moss JMS (1997) Age determination of Acacia tortilis (Forsk.) Hayne from northern Kenya. African Journal of Ecology 35, 266–277. doi: 10.1111/j.1365-2028.1997.067-89067.x McBride JR (1983) Analysis of tree rings and fire scars to establish fire history. Tree-ring Bulletin 43, 51–67. Melville S (1995) The effect of fire on casuarina (Allocasuarina littoralis) regrowth communities: an urban bushland case study. In ‘The sixth Queensland fire research workshop: working papers’. (Ed. B Roberts) pp. 68–79. (University of Southern Queensland: Toowoomba, Qld) Morrison DA (1995) Some effects of low-intensity fires on populations of cooccurring small trees in the Sydney region. Proceedings of the Linnaean Society of NSW 115, 109–119. Norton DA, Palmer JG, Ogden J (1987) Dendroecological studies in New Zealand 1. An evaluation of tree age estimates based on increment cores. New Zealand Journal of Botany 25, 373–383. Ogden J (1978) On the dendrochronological potential of Australian trees. Australian Journal of Ecology 3, 339–356. doi: 10.1111/j.1442-9993.1978.tb01184.x Ogden J (1981) Dendrochronological studies and the determination of tree ages in the Australian tropics. Journal of Biogeography 8, 405–420. doi: 10.2307/2844759 Ooi MKJ, Whelan RJ, Auld TD (2006) Persistence of obligate-seeding species at the population scale: effects of fire intensity, fire patchiness and long fire-free intervals. International Journal of Wildland Fire 15, 261–269. doi: 10.1071/WF05024 Pannell JR, Myerscough PJ (1993) Canopy-stored seed banks of Allocasuarina distyla and A. nana in relation to time since fire. Australian Journal of Botany 41, 1–9. doi: 10.1071/BT9930001

Pickering CM (2000) Sex specific differences in floral display and resource allocation in Australian alpine dioecious Aciphylla glacialis. Australian Journal of Botany 48, 81–91. doi: 10.1071/BT97121 Piovesan G, Di Filippo A, Alessandrini A, Biondi F, Schirone B (2005) Structure, dynamics and dendroecology of an old-growth Fagus forest in the Apennines. Journal of Vegetation Science 16, 13–28. doi: 10.1658/1100-9233(2005)016[0013:SDADOA]2.0.CO;2 Pollmann W (2003) Stand structure and dendroecology of an old-growth Nothofagus forest in Conguillio National Park, south Chile. Forest Ecology and Management 176, 87–103. doi: 10.1016/S0378-1127(02)00279-7 Rozas V (2003) Tree age estimates in Fagus sylvatica and Quercus robur: testing previous and improved methods. Plant Ecology 167, 193–212. doi: 10.1023/A:1023969822044 Rozas V (2004) A dendroecological reconstruction of age structure and past management in an old-growth pollarded parkland in northern Spain. Forest Ecology and Management 195, 205–219. doi: 10.1016/j.foreco.2004.02.058 Ruffner CM, Abrams MD (1998) Relating land-use history and climate to the dendroecology of a 326-year-old Quercus prinus talus slope forest. Canadian Journal of Forest Research 28, 347–358. doi: 10.1139/cjfr-28-3-347 Singer RJ, Burgman MA (1999) The regeneration ecology of Kunzea ericoides (A.Rich.) J.Thompson at Coranderrk Reserve, Healesville. Australian Journal of Ecology 24, 18–24. doi: 10.1046/j.1442-9993.1999.00942.x Taylor VL, Harper KT, Mead LL (1996) Stem growth and longevity dynamics for Salix arizonica Dorn. The Great Basin Naturalist 56, 294–299. Watson P, Wardell-Johnson G (2004) Fire frequency and time since fire effects on the open-forest and woodland flora of Girraween National Park, south-east Queensland, Australia. Austral Ecology 29, 225–236. doi: 10.1111/j.1442-9993.2004.01346.x Whelan RJ (1995) ‘The ecology of fire.’ (Cambridge University Press: Cambridge, UK) Wills TJ (2003) Using Banksia (Proteaceae) node counts to estimate time since fire. Australian Journal of Botany 51, 239–242. doi: 10.1071/BT01074 Worbes M (1995) How to measure growth dynamics in tropical trees a review. International Association of Wood Anatomists Journal 16, 337–351. Worbes M, Staschel R, Roloff A, Junk WJ (2003) Tree ring analysis reveals age structure, dynamics and wood production of a natural forest stand in Cameroon. Forest Ecology and Management 173, 105–123. doi: 10.1016/S0378-1127(01)00814-3

Manuscript received 1 August 2006, accepted 12 December 2006

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