A HOLOCENE POLLEN DIAGRAM FROM LYNCH'S CRATER, NORTH-EASTERN QUEENSLAND, AUSTRALIA

Transcription

1 New Phytol. (1983) 94, A HOLOCENE POLLEN DIAGRAM FROM LYNCH'S CRATER, NORTH-EASTERN QUEENSLAND, AUSTRALIA BY A. P. Department of Geography, Monash University, Clayton, Victoria, 3168 Australia {Accepted 26 February 1983) SUMMARY Pollen analysis of this core from Lynch's Crater provides a more detailed and continuous Holocene record than has been obtained previously from the site. The pattern of dry-land vegetation changes appears broadly similar to those from other sites covering this period from the Atherton Tableland, though problems of dating do place some restriction on temporal correlations between them. Swamp forest is recorded for the first time within the region from pollen and plant macroremains, and this existed from the time of arrival of rainforest, probably about 8500 years B.P. until between 6000 and 4500 B.P. Firing by Aborigines in addition to climate change is considered to have been an important factor in swamp forest destruction and in the promotion of subsequent changes in swamp vegetation. INTRODUCTION Previous palynological investigations of Lynch's Crater have revealed a long Late Quaternary record of vegetation and environmental conditions (Kershaw, 1974, 1976, 1978). Unfortunately the Holocene sediment sequence, containing the younger rainforest phase of Kershaw (1976), is poorly represented due to slow sediment accumulation rates and recent disturbances to the swamp surface. This paper presents a more detailed and complete record of this Holocene rainforest phase, felt necessary for two major reasons. The first is for comparison with other Holocene pollen diagrams from the Atherton Tableland (Kershaw, 1970, 1971, 1975) to provide a firmer basis for determination and explanation of regional vegetation patterns and changes. The second reason is that the sediments contain evidence of the existence of an extensive swamp rainforest, a vegetation type not recorded previously in or on Holocene peat sediments within Australia, to my knowledge. The presence of this forest was exposed by peat-mining operations, which are stripping the topmost sediments. Well-preserved stumps, with diameters ranging from a few centimetres to a metre, were encountered every few metres over the mining section, which now includes the coring position. Details of the site and its setting are given in Kershaw (1976). FIELD AND LABORATORY METHODS Much of the swamp surface has been lowered in historical times by frequent burning to promote fresh vegetation growth for cattle grazing. Consequently, in order to recover as complete a record as possible, a residual hummock was chosen for the coring site. This was located near the centre of the swamp, about 80 m east-south-east of an earlier coring position (Kershaw, 1976,fig. 2). Four 3 m X/83/ S03.00/ The New Phytologist

2 670 A. P. KERSHAW length cores from within a 20 cm square were taken with a D-section sampler to provide sufficient material for radiocarbon dating in addition to pollen analysis. The surfaces of cores were cleaned before being combined in 50 cm lengths. One cubic centimetre samples were taken at 5 cm intervals from the cores for pollen analysis. These were treated with hydrofiuoric acid to remove silica in addition to processing by standard acetolysis (Faegri and Iversen, 1964). The pollen was mounted in silicone oil and examined under an Olympus Vanox photomicroscope. From initial examination of samples, the sclerophy 11/rainforest boundary was located at a depth of about 120 cm, so samples were not examined for pollen far below this level. Pollen counts were continued until 150 'dry land' grains, excluding pteridophyte spores, had been recorded except in the top three samples, where pollen was too sparse for counts to exceed 100 grains. The number of grains per cm^ and number of charcoal particles above 20 fim maximum length per cm' were also calculated for each sample. These were minimum estimates as no allowance was made for losses during preparation. Material from the same level as each pollen sample was used for the determination of percentage moisture and inorganic contents of dry weight. In addition, inorganic contents were determined for samples lower than the pollen analysed section, to assist in correlation between this core and that of Kershaw (1976) over an extended period. THE POLLEN DIAGRAMS The results of all analyses are shown in diagrammatic form on Figures 1 and 2. Figure 1 includes pollen and spore taxa likely to have derived mainly from aquatic plants. Poaceae, which may contain a significant dry-land component, is included here, but it is considered that the major input will have been from local swamp sources. Figure 2 contains those taxa whose parent plants are now largely restricted to dry-land environments within the region. Evidence for the presence of swamp forest, though, indicates that this has not always been the case. ' Common dry land' taxa are those identified as major contributors in previously published Holocene pollen diagrams from the Tableland, and their separation from other taxa provides a basis for rapid comparison between records. All 'dry land' plant taxa with the exception of pteridophytes and also Asteraceae (tubiflorae), whose representation is likely to have been influenced greatly by recently introduced species, make up the pollen sum on which all percentages are based. Both diagrams are zoned intuitively on major changes in abundance of well-represented dry-land taxa. Suffixes of BenninghoflF and Kapp (1962) are used as an indication of the degree of certainty of taxon identification. In some cases a morphological term has been used, either as a label for an important but unknown taxon or added to a family name to represent a known taxonomic group within the family. Any changes to the identification status of taxa from Kershaw (1975 and 1976) are shown in Appendix A, which also contains some taxonomic and ecological information on previously unrecorded taxa. Nomenclature follows Clifford and Ludlow (1978) for angiosperms and Clifford and Constantine (1980) for pteridophytes and conifers. Core stratigraphy Description is based on field and laboratory examination of the whole core together with water and inorganic content measurements of individual samples.

3 A Holocene pollen diagram 671 Depth below surface; 0 to 27 cm Very decomposed, grey-black, granular, organic material with abundant living and dead roots which form a mat in the top few centimetres. Inorganic residues vary between 30 and 40 % of sample dry weight while water content remains about 300 % of dry weight. 27 to 63 cm Very decomposed, grey-black, sticky organic material with some roots, stem and leaf remains. Inorganic residues are consistently less than 10%, while water contents average 400% of dry weight. 63 to 135 cm Red-brown to grey-brown plant detritus within a matrix of decomposed organic material. Inorganic values are consistently low between 75 and 100 cm and between 120 and 135 cm, and peak to no more than 12% between 65 and 75 cm and between 100 and 120 cm. Water content averages 500% of dry weight except in the basal 20 cm, where it increases to 700 %. Zonation of diagrams Zone LC6. The sclerophyll taxa Casuarina and Eucalyptus dominate dry-land pollen, and all other taxa within the pollen sum and dry-land Pteridophyta are poorly represented. Charcoal values are moderately high throughout, while pollen concentrations are high in the basal two samples and then decrease towards the top of the zone. Swamp vegetation is dominated by Cyperus, monolete psilate spores (mainly from the swamp fern Blechnum indicum) and probably also Poaceae. Many Poaceae grains could have been derived from dry-land vegetation, but extremely erratic inter-sample variation suggests a dominant local swamp source. The presence of some open water is indicated by consistent representation of the floating-leaved aquatic, Nymphoides. Aquatic pollen makes up between 75 and 85 % of total pollen. Zone LC5. There is a sharp change at the zone LC6/LC 5 boundary between sclerophyll and rainforest domination of dry-land pollen. Casuarina decreases through the zone while Rapanea increases to become the best-represented taxon at the top. The zone is characterized by highest representations in the diagram of ' Eugenia' complex and the fern Nephrolepis. Cunoniaceae (tricolpate) has relatively high values while other consistently represented rainforest taxa are Cunoniaceae (dicolpate), Elaeocarpus, Flindersia, Ereycinetia and Loranthaceae. Canopy and sub-canopy taxa are the most important rainforest angiosperm components, and other lifeforms, apart from secondary trees at the base of the zone, have low representation. Pollen concentrations increase through the zone to high levels while charcoal concentrations, after a high peak in the basal sample, decline to negligible amounts at the top. Aquatic taxa decrease through the zone from over 80 % of total pollen at the base to about 30% at the top. Greatest declines are in Cyperus and Poaceae, but Machaerina, Haloragis, Hydrocotyle and Anthoceros show peaks in the lower part of this zone or in the top sample of zone LC6. Stylidium has its last representation in the diagram here. ZoneLC4. The understorey tree Rapanea dominates dry-land pollen, achieving over 60% of the pollen sunn in all samples, and all other taxa, apart from Cunoniaceae, 'Eugenia' complex, Elindersia and the ferns Nephrolepis and Dicksonia, have low values. A number of minor pollen taxa, including Glochidion/ Rubiaceae, Alphitonia, Argophyllum, Ereycinetia and Leea comp. are fairly 22 ANP94

4 "a cf. Charcoal particttt cm' Ilia Monolttt (p»ilat«) Lygo<lium microphyllum 't T3 "yclosorus Tricolporott (unknown) Stytidiufn Polygonum MalastomotQCMe Hydrocotyte Haloragis Drostra Typha Phftydru/Tt O a T3 c Poacta* Eriocaufon..ihi Cyptractae (other} 3 tr u Cyp0rus /Rhynchospora Cyperus Utricutaria f f f I I i Dry lond poltcn Aquatic polttn ond sports Oapth tmtow urfacc (cm) III Rodlocorbon dotifig somplit a I 3 Vin«s and cpiphytis Secondary tr«ct Undtrstor«y taia [] Canopy tr«*s Sclcrophyll taxa Rainforait anqiotparms Roinforast gymnotpirmt Dapth btlow surface (cm) Radiocarbon dating tamplts

5 A Holocene pollen diagram 673 consistently present while the latter taxon is restricted to the zone. Sclerophyll taxa and charcoal particles occur at very low levels throughout, while pollen concentrations reach maximum levels for the diagram in the lower samples and then decrease towards the top. All aquatic taxa, except for monolete psilate spores, have very low values. Zone LC J.This zone is characterized by high values of Cunoniaceae (tricolpate) and a high diversity of dry-land taxa. Rapanea declines to very low levels within the zone while Elaeocarpus, Casuarina and Myrtaceae achieve significant representation. Cunoniaceae (dicolpate), Marcaranga/Mallotus, Balanops, Macaranga tanarius comp., Argyrodendron trifoliatum. Calamus, Quintinia and Apodytes are consistently present, and a number of these occur for the first time. The ferns, particularly Platycerium and Polypodium subauriculatum have increased representation and Botrichium sim. has its highest values for the diagram. Pollen concentrations are relatively low, but charcoal values increase to a maximum level for the diagram towards the top of the zone. A large increase in aquatics to an average of about 70 % of total pollen is due mainly to Gleicheniaceae spores and also Machaerina towards the top of the zone. Drosera is recorded for the first time and is consistently present. Zone LC2. The major features of the dry-land pollen diagram are an increase in Elaeocarpus relative to Cunoniaceae, the consistent presence of Cardwellia comp. and Cordyline/Orania which have little or no previous representation, a continued increase in the proportion of sclerophyll taxa, and another high peak of charcoal particles. The aquatic pollen diagram shows the beginning of sustained high levels of Eriocaulon, Poaceae, Haloragis, Hydrocotyle, Melastomataceae, Anthoceros and Lygodium microphyllum. Zone LC1. There is no marked change in abundance of common taxa except that Podocarpus achieves consistent representation for the first time in the diagram hut pollen from sclerophyll vegetation and secondary trees has increased. Macaranga/Mallotus has increased representation relative to Cunoniaceae and Elaeocarpus, while the ferns Platycerium and Polypodium subauriculatum achieve highest values for the diagram. Dry-land pollen concentrations are very low and charcoal values are significant but reduced from those in zone LC2. A major feature of the zone is the large increase in Asteraceae (tubifiorae). Aquatic pollen consistently makes up more than 90 % of total pollen and there is high diversity of swamp taxa. Poaceae and monolete psilate spores are dominant though all cyperaceous taxa, except Elaeocharis which is not represented, Haloragis, Hydrocotyle and Anthoceros achieve very high values. Gleichenia is the only taxon consistently present in zone 2 to suffer an actual decline. DATING AND CORE CORRELATION It was suspected that the dates from the top part of a previous core, including those designed to date the sclerophyll/rainforest boundary, were too young (Kershaw, 1976). This suspicion was aroused by the fact that the sclerophyll/rainforest boundary was dated at least 1000 years younger than at Bromfield Swamp, a site existing now and assumed always to have existed under lower rainfall than Lynch's 22.-2

6 074 A. f. KERSHAW J Fig. 3. Proposed stratigraphic correlations between two sediment cores from Lynch's Crater. Crater. The relevant dates of 6850±90 and B.P. from the Lynch's Crater core are shown on Figure 3. In order to determine the source of any contamination, material from around the sclerophyll/rainforest boundary was dated as two fractions: a coarse fraction and a fine fraction separated by a 700 /i mesh sieve. The coarse fraction (ANU- 1538A, B.P.) dated older than the fine fraction (ANU-1538B, 6O5O± 120 B.P.), though neither was significantly older than the previous dates. It was suggested that the fine fraction could have been contaminated by soluble organic matter moved down the profile and that a carefully cleaned coarse fraction may produce a 'more reliable' date (John Head, pers. comm.). However this process produced a date (ANU-1686, B.P.) that was obviously far too young. Without having resolved this dating problem, further samples were dated from within the rainforest period and these conveniently fell along an age/depth gradient (see Fig. 3). The oldest of these though is intermediate in age between the fine and coarse fraction dates of ANU-1538 despite being 25 cm higher in the core. This adds further weight to the belief that the sclerophyll/rainforest boundary dates are too young. With the exposure of the swamp forest during mining, it was possible to collect

7 A Holocene pollen diagram 675 a sample of unaltered in situ wood which could be considered free of contamination. A section of a stump, subsequently found to belong to a species oi Flindersia (Joyce Lanyon, pers. comm.), was selected for dating. This gave an age of 7270±80 B.P. (WK-346). Unfortunately it was not possible to determine the exact stratigraphic position of this wood sample. However, some idea of its position can be gauged from the representation of Flindersia pollen in the pollen diagram if the not unreasonable assumption that the pollen was largely derived from locally growing Flindersia trees is made. Although Flindersia is recorded just above the sclerophyll/rainforest boundary, its highest values and therefore most likely representation on the swamp surface is during the period represented by zone LC4. This would mean that the dates from both the base of zone LC4 and from the sclerophyll/ rainforest boundary are significnatly too young. The presence of swamp forest could explain the problems with these dates. Deep root penetration ofthe sediments may have caused contamination ofthe coarse fraction while some root decomposition may have allowed infilling by fine material consequently affecting the fine fraction. Some measure of the accuracy of the younger dates may be made from a comparison of pollen changes here with those at other sites. In the Bromfield Swamp diagram, Rapanea and Freycinetia decline at about 6000 B.P. suggesting that the date of B.P. for the same events at Lynch's Crater is about 1500 years too young. The youngest date of 3200 ± 60 appears realistic in light of pollen changes in other diagrams but there is insufficient consistency between diagrams at this time to be completely confident about the date. It is not possible to extend this kind of comparison to the determination ofthe age ofthe sclerophyll/rainforest transition because of variables involved in rainforest migration. It might be assumed that because Lynch's Crater occurs under higher rainfall than other sites, rainforest would have arrived here earlier. However, it has been suggested that rainforest may have arrived first around Bromfield Swamp because of its closer proximity to potential highland refugia occupied during the previous sclerophyll phase (Ash, 1983). Percentage inorganic values, together with the position ofthe rainforest/sclerophyll boundary, are used to correlate the two Lynch's Crater cores on Figure 3. It would appear that as much as 50 cm of sediment may have been missing from the original core. A major peak in inorganic values allows correlation between the lower parts of the core. The date of B.P. for the end of the inorganic phase corresponds well with a basal organic date of B.P. from Bromfield Swamp, suggesting a time of major environmental change. THE SCLEROPHYLL PHASE AND SCLERPHYLL/RAINFOREST TRANSITION It has been estimted that effective rainfall must have been less than half that of present for rainforest to have been excluded from this area (Kershaw, 1976). Most severe climatic conditions could have occurred between about and B.p. where the high inorganic sediment component suggests very slow swamp growth or greater inwash of soil from sparsely vegetated crater slopes. This is out of phase with the generally accepted period of late Pleistocene maximum aridity for Australia, centred on years B.P. (Bowler et al., 1976). However, recent information from a continuous sediment core derived from Lake Bullenmeri on the Victorian Western Plains indicates driest conditions occurred there between and 1000 years B.P. (Dodson, 1979). In the light of this information from

8 070 A. r. KERSHAW continuous datable sediment cores, a case is made for the re-examination of the timing of this arid phase, at least for subcoastal parts of the continent. The similarity in sediment composition between the sclerophyll samples of zone LC6 and subsequent rainforest zones, combined with high levels of moisturedemanding swamp taxa such as Lygodium and monolete psilate spores which are generally associated with rainforest environments in zone LC6, suggests that rainfall had already risen to levels sufficient to support rainforest. These levels could have been achieved after the dry period, as early as B.p. The substantial gap between climatic amelioration and time of arrival of rainforest around the site could provide some indication of the rate at which rainforest is able to expand from refugia. However, high charcoal levels in the sediments suggest that fire was an important environmental factor and would have assisted in the maintenance of sclerophyll vegetation and impeded the progress of rainforest. The arrival of rainforest around Lynch's Crater is marked by significant representation of secondary tree taxa, including Macaranga/Mallotus, Tretna and Melicope, but these are soon excluded by 'primary' rainforest taxa. The charcoal curve peaks at the rainforest/sclerophyll boundary possibly because of greater fuel levels with the arrival of rainforest to promote occasional intense fires. Evidence for fire then declines with a reduction in sclerophyll vegetation through the period represented by zone LC5. THE RAINFOREST PHASE One of the important features here is the expansion of rainforest over the swamp surface. Two taxa, Eugenia cf. kuranda and Elindersia cf. pimeliana were certainly part of the swamp forest, as they have been identified from wood samples sawn from in situ stumps (Joyce Lanyon, pers. comm.). Although it has not proved possible to determine for certain the pollen of these taxa in core samples they can probably be related to a Eugenia type, which is extremely well represented in zone LC5, and to Elindersia, which is best represented in zone LCR4, respectively. Rapanea comp., which dominates rainforest pollen in zones LC5 and LC4, was probably a major swamp taxon as it is difficult to conceive of pollen from an understorey plant achieving significant dispersal beyond the forest canopy. High pollen concentrations from ' dry-land' taxa within these zones also support the idea of a very local rainforest presence. Major dry-land taxa, Cunoniaceae and Elaeocarpus, which dominate the earlier parts of the rainforest phase in other diagrams from the Tableland are greatly reduced during this period, suggesting that they did not form a substantial component of the swamp forest and that dry-land taxa generally must have had poor representation due to dilution from swamp forest taxa. It is therefore likely that all taxa achieving their highest values within zones LC 5 and LC 4 were present on the swamp surface. These would have included the taxa G/oc/it^^/on/Rubiaceae, Alphitonia, Argophyllum, Drimys, Elindersia, Ereycinetia, Glochidion harveyanum, Leea comp. and probably Cunoniaceae (dicolpate) and the ferns Nephrolepis and Dicksonia. Greater insight into the nature of this swamp forest may be gained from comparisons with those occurring in Central Sumatra whose history has been elucidated from one site, Danau Padang (Morley, 1982). This is the only other swamp forest site lying between tropical lowland and montane rainforest types known to me which has been examined. Here pollen of Myrsine, a genus closely

9 A Holocene pollen diagram 677 related to Rapanea, dominates the pollen rain, Glochidion and Fugenia are well represented and Nephrolepis is the dominant identifiable fern. Monolete psilate fern spores are also common and, as at Lynch's Crater, many of these could be referred to the swamp fern Blechnum indicum. Vines are well represented, and one of the most common, Flagellaria indica, could be the ecological equivalent of Freycinetia at Lynch's Crater. It might be assumed that structural similarities would have been even greater. 'Myrsine' swamp forest today forms a community up to 5 m in height, and is sufficiently open to allow the growth of numerous vines. This may have been the nature of the 'Rapanea' forest. Taller swamp forests, up to 20 m in height, occur in more marginal Sumatran swamps, and the presence of wide-diameter trunks, such as those of Flindersia recorded from Lynch's Crater, suggests that taller swamp forests were also present. Of proposed swamp forest taxa at Lynch's Crater, the majority have been found to be more prevalent at altitudes higher than Lynch's Crater in surface samples from the region, while only one, Nephrolepis, was more common in lowland samples (Kershaw, 1973). This suggests that temperatures may have been cooler than those of today, though the more continuous cloud cover and regular drizzle during the 'dry' season at higher altitudes are important additional variables to determination of vegetation patterns. A less seasonal climatic regime may in fact have favoured the development of swamp forest at this time. Because of dilution by swamp forest taxa, pollen from dry-land sources is poorly represented in zones LC5 and LC4. Cunoniaceae (tricolpate) achieves highest values though Elaeocarpus, Urticaceae/Moraceae and Casuarina are consistently present. The domination of the ratio-diagram by Cunoniaceae supports the climatic interpretation from swamp forest taxa that a cool wet climate prevailed. It is probable that many swamp taxa also occurred within dry-land forest. The early part of the rainforest phase at Bromfield Swamp shows highest values for Rapanea, Freycinetia, Glochidion harveyanum, Flindersia and Nephrolepis as at Lynch's Crater, yet here open water prevailed, with little evidence of marginal swamp, and it is unlikely that swamp forest could have been present within the catchment. These taxa, though, may have fringed the lake margins and consequently had high representation through water as well as wind dispersal. Sharp changes occur in pollen spectra at the zone LC4/LC3 boundary. The increased importance of canopy tree taxa together with a greater pollen diversity suggests higher representation of dry-land vegetation at the expense of swamp forest. The majority of those taxa which are considered to have occurred on the swamp decline or disappear within the zone except for the tree fern Dicksonia, which appears to maintain its position on the swamp. A rise in charcoal particle concentrations to very high levels within the zone suggests that fire may have been an important factor in the destruction of swamp forest. Replacement largely by the ground fern Gleichenia but including Drosera and Machaerina is consistent with this hypothesis, as the ability of these taxa to colonize burnt swamp forest environments has been demonstrated elsewhere (e.g. Rigg, 1962; Wardle, 1977). Whether this vegetation change was associated with any climatic change is debatable. The domination of dry-land pollen by Cunoniaceae and high values for taxa such as Balanops, Elaeocarpus, Quintinia and Calamus which are characteristic or high rainfall areas, together with low values for secondary trees, suggests that moisture was not a critical factor. However, as important 'swamp taxa' decline at a similar time at Bromfield Swamp, which was still in an open-water phase, a

10 678 A. P. KERSHAW regional explanation must be invoked. A rise in temperature was the preferred reason at Bromfield Swamp (Kershaw, 1975) and there is some support for this from the Lynch's Crater diagram, with increased representation of Macaranga tanarius comp.. Calamus and Apodytes, which attained higher percentages in surface samples at or lower than the altitude of Lynch's Crater (Kershaw, 1973). As mentioned previously, an increase in seasonality may also have had some infiuence. From the beginning of zone LC 2 both dry-land and swamp vegetation begin to take on present-day characteristics. A reduction in Cunoniaceae and increase in Elaeocarpus is evidence of a further increase in mean annual temperature and/or greater rainfall seasonality. Associated with this are increases in taxa indicative of marginal or less complex rainforest such as Podoearpus and Macaranga/Mallotus, and higher values for sclerophyll taxa which suggest that the climate became drier. The boundary between zones LC 2 and LC 1 is marked by a large increase in Asteraceae. As the only recorded species of this family on the swamp and within the catchment are the introduced plants Ageratum conizoides Linn, and Erechtites valerianifolia D.C, zone LCI could mark the period of European mans's infiuence. A relatively rapid sedimentation rate of 25 cm within the last 60 years or so could be explained by deposition of soil material eroded from the catchment as a result of deforestation. The large increase in inorganic matter within the sediment combined with very low concentrations of dry-land pollen is consistent with this interpretation. An alternative explanation is that the topmost sediments have been mixed through ploughing for cultivation or to encourage pasture in the past, and that the zone LC 1 provides an average of conditions existing within the last few thousand years. There is certainly little variation in pollen composition between the top six pollen spectra, and pollen concentrations, if aquatic taxa were included, would be extremely high. The low concentrations of dry-land pollen could then be explained by a combination of deforestation during European occupation and the presence, through the last few thousand years, of complex rainforest containing few anemophilous species. Zone LC 2 marks a transition on the swamp from a Gleichenia dominated to a diverse vegetation. A number of factors, including a reduction in moisture as the swamp sediments accumulated to the level of the stream outlet, increased inorganic content of the sediment, increased disturbance and a warmer or more seasonal climate may have contributed to these changes. THE INFLUENCE OF ABORIGINAL MAN There has been increasing awareness in Australia of the degree to which aboriginal man may have modified the plant landscape with his conscious use of fire and other practices related to his food-gathering activities (e.g. Jones, 1975). Some of the evidence for the impact of man has been derived from Lynch's Crater. A massive increase in charcoal concentrations around B.P. has been interpreted as the result of aboriginal burning, which brought about a change in regional vegetation from moist araucarian rainforest to sclerophyll vegetation (Singh, Kershaw and Clark, 1981). Burning pressure was maintained, and it is reasonable to consider that the fire regimes responsible for charcoal deposition in the early Holocene were those imposed by Aborigines. With increased rainfall, man was probably unable to prevent the incoming of complex rainforest and its extension over the swamp surface. However, the

11 A Holoeene pollen diagram 679 charcoal curve rises again about 5000 to 6000 years ago while complex rainforest still covered the Tableland. Without a flammable sclerophyll vegetation within the area a regional charcoal source is unlikely, and all charcoal was probably derived from burning on the swamp surface. It is unlikely that chance fires caused by lightning would be sufficient to produce the consistently high levels of charcoal recorded, and a human cause must be invoked. The fact that man visited the swamp is demonstrated by the collection of stone tools exposed during mining operations (John Campbell, pers. comm.). It is only possible to speculate on the reasons for man's interest in this swamp environment. Original visitations may have been for plant foods such as the roots of Cyclosorus gongylodes (Schkuhr) Link and Blechnum indicum Burm. F. known to have been used by aborigines of this region (Golson, 1971). Cyclosorus is identified from its spores while Blechnum is likely to have made up a significant proportion of monolete psilate spores. Burning may have facilitated access or encouraged the growth of these and other desirable swamp species. At present, the swamp supports a number of additional food plant species such as Lepironia articulata (Retz) Domin., Melastoma malabathricum L. and Typha domingensis Pers. (Golson, 1971) - and these may have been promoted by the activities of man. CONCLUSIONS The analysis of this core has revealed a much more detailed and complete record of the naore recent vegetation history from Lynch's Crater than that of Kershaw (1976). The pattern of dry-land vegetation changes corresponds in broad terms to those revealed in studies of previous Holoeene sites on the Atherton Tableland, especially Bromfield Swamp, but detailed correlations are made difficult by the presence of local swamp forest and problems of accurately dating the condensed Lynch's Crater sequence. From the nature of Late Pleistocene sediments it is suggested that the major arid period occurred between about and years B.P. Climatic conditions may have ameliorated sufficiently by B.P. to support rainforest, but the replacement of sclerophyll vegetation by rainforest did not occur until at least 8500 B.p., possibly due to the distance rainforest had to travel from refugia occupied during the arid period combined with the retarding eflfect of fires generated within sclerophyll vegetation. 'Temperate' or montane vegetation dominated the early part of the rainforest phase under cooler and effectively wetter conditions than those of today. A number of taxa which formed part of this forest invaded the swamp surface to form a swamp forest which appears to have shared some characteristics with swamp forest types from Sumatra, existing under similar climatic conditions. The decline of swamp forest at some time between 6000 and 4500 B.P. was associated with a change to warmer or more seasonal conditions but its physical destruction probably resulted from firing. Gleichenia swamp replaced the swamp forest and was itself replaced by a diverse swamp vegetation within the last 3000 years. At this time surrounding dry-land vegetation took on a present-day 'subtropical' appearance due to a further increase in temperature or seasonality. Some vegetation changes suggest that there may have also been a decrease in rainfall, though these could have resulted from disturbance to the vegetation by aboriginal man.

12 68o A. P. KERSHAW ACKNOWLEDGEMENTS I am very grateful to Geoff Hope, Carl Shaw, Garrey Werren, Roy Phelps and Skip Rhodes for assistance with fieldwork, to Janet Williams for preparation of some pollen samples, to Joyce Lanyon of the Forestry Commission of New South Wales for wood sample determinations, to Professor D. Walker for his very valuable comments on a draft of the paper, to Helen MacDonald for typing the text and to Gary Swinton and Sue Tomlins for drafting the figures. The project was greatly assisted by an A.R.G.C. grant. REFERENCES ASH, J. E. (1983). Rainfall patterns in N.E. Queensland, B.P. In: Proceedings of the CLIMANZ Conference 1981 (Ed. by J. M. Bowler, J. Chappell & J. Hope). Australian Academy of Science, Canberra, (in press). BENNINGHOFF, W. S. & KAPP, R. O. (1962). Suggested notations to indicate identification status of fossil pollen. Potten et Spores, 4, 332. BOWLER, J. M., HOPE, G. S., JENNINGS, J. N., SINGH, G. & WALKER, D. (1976). Late Quaternary Climates of Australia and New Guinea. Quarternary Research, 6, CLIFFORD, H. T. & CONSTANTINE, J. (1980). Ferns, Fern Allies and Conifers of Australia: a Laboratory Manual. University of Queensland Press, Queensland. CLIFFORD, H. T. & LUDLOW, G. (1978). Keys to the Families and Genera of Queensland Flowering Plan 2nd edn. University of Queensland Press, Queensland. DODSON, J. R. (1979). Late Pleistocene vegetation and environments near Lake BuUenmeri, western Victoria. Australian Journal of Ecology, 4, 419^27. FAEGRI, K. & IVERSON, J. (1964). Textbook of Pollen Analysis, 2nd edn. Blackwell Scientific Publications Qxford. GOLSON, J. (1971). Australian aboriginal food plants: some ecological and culture-historical implications. In Aboriginal Man and Environment in Austratia (Ed. by J. Mulvaney & J. Golson), pp A.N.U. Press, Canberra. JONES, R. (1975). The Neolithic, Palaeolithic and the hunting gardeners: man and land in the Antipodes. The Royal Society of New Zealand Bulletin, 13, KERSHAW, A. P. (1970). A pollen diagram from Lake Euramoo, north-east Queensland Australia Netv Phytologist, 69, KERSHAW, A. P. (1971). A pollen diagram from Quincan Crater, north-east Queensland, Australia Neui Phytologist, 70, KERSHAW, A. P. (1973). Late Quaternary vegetation of the Atherton Tableland, north-east Queensland Australia. Unpublished Ph.D. thesis, Australian National University. KERSHAW, A. P. (1974). A long continuous pollen sequence from northeastern Australia Nature KERSHAW, A. P. (1975). Stratigraphy and pollen analysis of Bromfield Swamp, north-eastern Queensland, Australia. New Phytologist, 75, KERSHAW, A. P. (1976). A late Pleistocene and Holoeene pollen diagram from Lynch's Crater, north-eastern Queensland, Australia. New Phytologist, 77, KERSHAW, A. P. (1978). Record of last interglacial-glacial cycle from northeastern Queensland Nature MoRLEY, R. J. (1982). A palaeoecological interpretation ofa 10,000 year pollen record from Danau Padang, Central Sumatra, \ndonesia. Journal of Biogeography, 9, RiGG, H. H. (1962). The pakihi bogs at Westport, New Zealand. Transactions of the Royal Society of New Zealand (Botany), 1, SINGH, G., KERSHAW, A. P. & CLARK, R. (1981). Quaternary vegetation and fire history in Australia. In: Fire and Australian Biota (Ed. by A. M. Gill, R. A. Groves & I. R. Noble), pp Australian Academy of Science, Canberra. WARDLE, P. (1977). Plant communities of Westland National Park (New Zealand) and neighbouring lowland and coastal areas. New Zealand Journal of Botany, 15,

13 A Holocene pollen diagram 681 APPENDIX Some information on taxa represented on the pollen diagrams different to that detailed in Kershaw (1975, 1976). Pollen taxon Family Plant habit Known ecology and distribution mainly in north-east Queensland Argyrodendron peralatum comp. Botrychium sim. Cardteellia comp. Carnarvonia Cordyline Orania Cyathea Cyclosorus Dicksonia Drosera ' Eugenia' complex Evodiella Flagetlaria Gleichenia Hodgkinsonia Hypserpa Ilex Leea comp. Loranthaceae Lycopodiaceae Sterculiaceae Ophioglossaceae Proteaceae Proteaceae Agavaceae Aracaceae Cyatheaceae Thelypteridaceae Dicksoniaceae Droseraceae Myrtaceae Rutaceae Flagellariaceae Gleicheniaceae Rubiaceae Menispermaceae Aquifoliaceae Leeaceae Loranthaceae Lycopodiaceae Canopy trees Ground ferns Canopy trees Canopy trees Normally understorey shrubs Subcanopy feather palms Tree ferns Ground ferns Tree ferns Insectivorous herbs Canopy trees Secondary trees Vines Ground ferns/ vines Shrub Vines Canopy trees Secondary shrubs Parasites Ground ferns Drier rainforests Widespread outside rainforest Widespread in rainforests Most common in cooler, wetter rainforests or in rainforests on low-nutrient-status soils Common in swampy lowland forests and at high altitudes on rainforest margins Common in lower montane forests In high-altitude rainforests and along streams in wet sclerophyll forests, especially where cool Common onfloatingroot mat swamps but also in rainforest Wet, cool rainforests generally, but surviving in moist gullies in some warmer rainforests In wet sclerophyll forests and on drier swamps Currently under revision; the majority of eugenias will be transferred to Syzygium and Acmena (B. P. M. Hyland, pers. comm.). Very widespread in rainforests but extending into open woodlands in Cape York Peninsula Uncommon trees in montane rainforests Common in drier or disturbed lowland rainforests and in monsoon forests Cover large areas of cool, wet simple rainforests on poor acidic soils Dense in drier sub-montane rainforests Common throughout north Queensland rainforests Known only from coastal swamp palm forests in north Queensland Widespread along rainforest margins Widely distributed Indicators of disturbance within rainforests

14 682 A. P. KERSHAW APPENDIX {continued) Pollen taxon Family Plant habit Known ecology and distribution mainly in north-east Queensland Lygodium microphyllum Melicope broadbentiana comp. Muehlenbeckia Nephrolepis Ophiorrhiza Platycerium Polygalaceae Polypodium subauriculatum Rhipogonum Stenocarpus Tetracera comp. Lygodiaceae Rutaceae Polygonaceae Oleandraceae Rubiaceae Polypodiaceae Polygalaceae Polypodiaceae Smilacaceae Proteaceae Dilleniaceae Vines Secondary or sub-canopy trees Vines Ground ferns and epiphytes Herbs Epiphyte Mainly herbs and shrubs Epiphyte Wiry vines Sub-canopy trees Vines Scrambles over taller graminoids on stable floating root mat and drier stable root mat swamps Widespread in rainforests Rainforests Common ground ferns in disturbed areas and widespread epiphytes in rainforests Common and widespread in rainforests Common within rainforest margins Generally heath plants with one rainforest tree, Xanthophyllum, widespread in north Queensland In early publications labelled Davalliaceae or Polypodiaceae/ Davalliaceae. Common within rainforest margins Widespread in rainforests especially on soils derived from granite Widespread in rainforests Two widespread species in rainforests

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