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Home , Aristotelia (plant), Atherospermataceae, Athrotaxis, Athrotaxis cupressoides, Athrotaxis selaginoides, Eucalyptus vernicosa

191

REGENERATION OF SELAGINOIDES AND OTHER ON LANDSLIDE FACES IN

by Phil Cullen

(with four tables and two text-figures)

Seedling surveys indicated that landslide faces provide opportunities for and to regenerate in thamnic and high altitude callidendrous rainforest. The spatial distribution of mature A. selaginoides stems at some sites suggests that they have originated on past landslides. Leptospermum scoparium and vernicosa seedlings were also present at some of the sites investigated. Therefore, landslides may provide regeneration opportunities for these species in rainforest communities in the absence of fire. Thephysical attributes of A. selaginoides suggest that the species would be advantaged by canopy disturbance of the scale caused by landslides as opposed to smaller treefall gaps. The cooler climate, higher levels of slope instability, avalanches and snowstorms during the last glacial would have been well suited to this species. Key Words: Athrotaxis selaginoides, rainforest, regeneration, Tasmania.

In BANKS, M.R. et al. (Eds), 1991 (31:iii): ASPECTS OF TASMANIAN -A TRIBUTE TO WINIFRED CURTIS. Roy. Soc. Tasm. Hobart: 191-200. https://doi.org/10.26749/rstpp.124.2.191

At present, fire is the major form of catastrophic INTRODUCTION disturbance in A. selaginoides dominated forests. However, fire is more likely to destroy the species than Recent research has demonstrated that Athrotaxis promote its regeneration. The fire regime since the selaginoides (nomenclature follows Buchanan et al. a..TTival of Europeans in Tasmania has resulted in the 1989) is reliant upon canopy disturbance, resulting loss of large areas of rainforest and alpine vegetation from treefalls or natural catastrophes, for regeneration within the range of the species (Kirkpatrick & Dickinson opportunities in evergreen (Cullen 1987 a, 1984a, b). Brown (1988) estimates that about 30% of Read & Hill 1988a). Infrequent catastrophic disturbances standing A. selaginoides stems have been killed by fire. in one form or another are now seen as integral In Tasmania, ecologists have paid much attention components of many forest ecosystems (e.g. White to the effects of fire (for example Jackson 1968, Mount 1979). In southern South America and New Zealand, 1979, Kirkpatrick & Dickinson 1984a). With the events such as landslides and rockfalls (often caused exception of Hughes (1987), who studied the effects of by seismic activity), avalanches, burial by volcanic floods on riparian and aquatic plant communities, there debris, fires, windstorms, and floods are common have been no ecological studies dealing with other and can cause widespread disturbances in cool forms of catastrophic disturbance. temperate rainforests in montane and subalpine areas. The present frequency of catastrophic disturbances, Many and Nothofagus species rely upon other than fire, in forests containing A. selaginoides is catastrophic disturbances to maintain their positions not known. However, landslides and rockfalls are of dominance in these forests from one common on steep slopes in the high rainfall, mountain­ generation to the next (Hutchinson 1932, ous, western and southern regions of Tasmania. They McKelvey 1953, Lloyd 1960, Cameron 1960, occur on a variety of rock types,often in areas supporting Beveridge 1973, Wardle 1970, 1974, Burke 1974, thamnic or high altitude callidendrous rainforest Clayton-Green 1977, Veblen & Ashton 1978, dominated by A. selaginoides and Nothofagus Veblen 1982, Veblen & Stewart 1982, Norton 1983, cunninghamii (see Jarman et al. 1984 for definitions of Veblen et al. 1983, Veblen & Lorenz 1987). rainforest terminology). It seems probable that landslides However, Tasmania has no volcanoes, seismic could create conditions suitable for A. selaginoides activity is much less intense and the mountains regeneration (Cullen 1987a). Linear stands of A. here do not receive large snowfalls or support selaginoides, perpendicular to the contours, on steep glaciers. As a consequence, catastrophic mountain slopes, have been sighted from the air in the disturbances caused by these agents do not achieve south of the state. These stands may have established the same prominence in the landscape as they do in on past landslides, thus accounting for their orientation. either southern South America or New Zealand. 192 P' Cullen

This study was conducted to assess the suitability of 1- J~~j'l ------"- landslides as sites for regencration of A. S<:IuglfiC'IWe,1 and othcr tree species in thamnic and high altitude ~ " ~_/~0 callidcndrous rainforests.

METHODS

• DR Landslides and rockfalls were investigated at Frenchmans Cap (quartzite), Mt Victoria Cross (sandstone), and at Dunning Rivulet on the Great Western Tiers (dolerite) (fig. 1). In all, six study sites ~ .co /~ were selected at thcse three localitics (table 1), located on areas disturbed by landslide or rockfall and adjacent to mature rainforest containing A.. selaginoides . At each site, forest composition was investigated using 5 m wide transects of varying lengths. The transects I ~\~ :f~9! were orie11tated parallel to thc contours and locatcd so as to cross the centres of the areas disturbed by landslide and to ex tend into undisturbed forest. ~<)tJ" .. Along each transcct the height of sccdlings of all l___ ,J species capable of growing to be trees and the diameter FiG. 1 -- Location of the three areas of study for of all tree species greater than 10 mm d.b.h. were landslides and rockfalls. DR '" Dunning Rivulet, recorded. Recording was terminated when approx­ FC = Frenchmans Cap, VC '" Mt Victoria Cross. imately 200 individuals were measured. The projected cover of all species was estimated, using Braun-Blanquet cover classes.

TABLE 1 Stand Designation, Locality and Characteristics of Study Sites

Stand/designation Grid Altitude Aspect Parent material Soil pH reference (m) (top 100 mm)

------~~- -"------"------~~----- Frenchmans Cap FC] 043193 900 SW 30-35 Quartzite 4.5 FC2 059912 820 SE 25-30 Quartzite 4.5

Mt Victoria Cross VCI 721876 920 WNW 20-25 Sandstone/dolerite talus 4.5 VC2 722878 920 WNW 20-25 Sandstone/dolerite talus 4.5 VC3 72388] 920 WNW 20-25 Sandstone/dolerite talus 4.5

Dunning Rivulet DR2 683775 980 WNW 17.5 Dolerite 5 ---_._--- tree species on landslide faces in Tasmania 193

Seedling densities for disturbed and undisturbed disturbed site when analysing the data for this table forests were calculated. Percentage frequencies for because it had been bumt relatively (c. 35 seedlings and adults of all tree species in 100 mm size years Many of the species recorded on the classes were determined for each stand, the size classes landslides are those more commonly found at higher used being 1 = <10 mm d.b.h. (seedlings), 2 == 10- altitudes. A comparison with appendix A of Jannan et 95 mm, 3 == [00-195 mm and ensuing 100 mm size al. (1984), reveals that 29 out of the 34 species found classes. A positive relationship between size and to be confined to the disturbed sites have not diameter was assumed for A. selaginoides (Ogden been recorded in thamnic rainforest. Fourteen of these 1978 and Cullen 1987a). Read & Hill (1988a) found a have not been recorded in rainforest at all (table 2) and positive relationship between age and diameter [or N most of the remainder have been recorded cunninghamii. moschatum, from open montane laIllH}'''''' lucida, Phyllocladus aspleniifolius and Athrotaxis IS those dominated by Athrotaxis selaginoides at a number of sites. Therefore, trunk forests are generally found at higher altitudes than diameter can be used as a crude estimate of stem age for those containing A. selaginoides, or in frost hollow these species. Increment cores were taken from mature situations (Cullen & Kirkpatrick 1988). A. selaginoides stems at stands DR2, FC1, VC2 and A.. selaginoides seedlings are common on the VC3 to obtain estimates of minimum age since landslide faces at the six study sites, and seedling disturbance and the period for which the site was open densities are greater for A. selaginoides than for any to A. selaginoides recruitment. other tree species at all but one site (DR2, table 4). In The cover class information for the species recorded three out of six cases, A.. selaginoides seedlings are at each site was tabulated and sorted with the assistance absent from adjacent mature forest despite the close of the ecological data base system ECOPAK (Minchin proximity of adult A. selaginoides. The seedlings present 1986). in the mature forest at stands FC2 and VC2 are restricted The mature forests at the study sites were classified to single patches close to the disturbed areas, suggesting subjectively according to the rainforest classification of that the loss of adjacent canopy cover may have Jarman et al. (1984) and by comparison to the forests produced conditions which favoured their growth. At described by Cullen (l987b). stand FC I the "mature" part of the study site was bumt Aerial photographs at a scale of 1:20 000 were used at least 35 years ago (date obtained from ring counts on to assess the incidence of landslides in the Mt Victoria a fire damaged A. selaginoides stem). A number of adult Cross region. Unfortunately aerial photographs of a A.. selaginoides stems survived this fire and have suitable scaJe were not available for the other regions provided a source for the burnt area and the investigated. landslide face. Thus, there is a heavy stocking of A. selaginoides regeneration in the "mature" section of the forest RESULTS AND DISCUSSION Nothofagus cunninghamii seedlings display a similar pattem to those of A. selaginoides. With the exception The sites investigated support either thamnic or high of stand FC 1, discussed above, seedling densities are altitude callidendrous rainforest. Although floristic higher in the disturbed areas than in the adjacent composition and canopy height of the forests varies undisturbed forests. In fact, much of the N. from site to site, in all cases the main canopy is formed cunninghamii regeneration in the mature forest is from by an unbroken stratum dominated by Nothofagus basal sprouts rather than seedlings. These findings cunninghamii with emergent Athrotaxis selaginoides support those of Read & Hill (1985, 1988a), who found and scattered individuals of Atherosperma moschatum, that N. cunl1inghamii regenerates in canopy gaps and Eucryphia lucida or E. milliganii, and Phyllocladus that many of the seedling-sized N. cunninghamii stems aspleniifolius. Beneath the main canopy a layer of within undisturbed forests are basal sprouts. broad , the palm-like pandanifolia, At Mt Victoria Cross, Eucryphia milliganii is present and, at the Mt Victoria Cross sites, R. scoparia form a on the disturbed sites in similar concentrations to N. discontinuous second stratum. The ground layer at an cunninghamii. There are also a number of small the sites is composed of scattered shrubs, mosses, fems, diameter E. milliganii stems which may have been and herbs, with much of the ground covered by litter survivors from the previous forest or coppice regrowth (table 2). from stems damaged in the landslides. Atherosperma The canopy disturbance caused by landslides has moschatum and E. lucida were only recorded at stands favoured the growth of shrubs and herbaceous species FC2 and DR2. As seedlings, they occur in similar (table 3), in particular, grasses and composite herbs. abundance in both the disturbed area and the mature The "mature" portion of stand FCI was included as a forest at FC2. Seedling populations ofthese two species 194 P.Culien

TABLE 2 Species Distribution and Cover Class

-"-"'-~------'---'" Species an~ family* Habitt Stand designation and VC3 Fe2 DR2 VC2 Vel FCI VC3 DR2 vez Vel FCZ FCI

lIabitat:j: ------.--.-- - --~""--- -. - -_.------, -"'---- Mature/undisturbed or disturbed M M M M M M D D D D D D

.~------.-.. -~-- _. ------"'---~-- NOlhofagus gunnii (Fa) + Olearta ledifolia (Co) sN + Oriles millixanii (Pr) s I + Helichrysum dendroideum (Co) liN + Archeria comberi (Ep) sN + Epacr!s impressa (Ep) sN + Libertia pulchella (Ir) h + Scirpus aucklandicus (Cy) hOB + Agraslis palvijlora (Po) hN + Oriles revoluta (Pr) 80M + Gentianella diemensis CO e) hN + Danlhonia jortunae- hibernae (Po) hO + Carex spp. (Cy) h + phlogopappa (Co) sOM + thymifolia (Ep) sN + Helichlysum ledifolium (Co) sN 1 Cardamine spp. (Cf) hN + Cyalhodes parvifolia (Ep) sHAC ! Senecio biserratus (Co) hN + + EPOCTis serpyllifolia (Ep) sOM + 1 Luzula sp. (Ju) hN + + Poa labillardieri (Po) h 2 + + P. gunnii (Po) h + + -I- + + Riehea sprengelioides (Ep) sOM 2 2 1 + Hypolepis rugosula (De) pN + + 2 + Gaultheria hispida (Er) sN -I- + + + Leptospermum scoparium (My) t I 2 + 2 1 Epilohium spp. (On) hO + He/ichrysum adenophorum (Co) hN + + + Gnaphalium spp. (Co) hN + + + luncus spp. (Ju) hN -I- + + Oreoholus oxycarpus (Cy) hOM + + + + + Brachycome tenuiscapa (Co) hN + + + + + Helichrysum backhousii (Co) sOM 1 + 2 1 (Ep) sit 2 + 2 I 2 + + Athrotaxis selaginoides (Ta) 1 2 1 1 1 2 1 1 Nothofaglls cunninghamii (Fa) 2 2 3 2 2 I 1 1 Coprosma nitida (Ru) + + 1 + 1 + Tasmania lanceolala (Wi) s + + + + + + 1 (Ep) sit 2 + 1 1 + + 1 Polystichum proliferllm (As) p + + + Eucryphia milliganii(Mo) 2 + 2 2 1 1 Oriles diversijolia (Pr) + + + + 2 2 Blechnum wattsii (Bl) p + 1 + + + + Oxalis lactea (Ox) h + + + + Histiopteris incisa (De) p + + 2 + Lycopodium spp. (Ly) p + + Acacna mOlltana (Ro) hN + + Senecio leptocarpus (Co) hN + + tree species on in Tasmania 195

Species and family* :Uahiti' Stand designation ami ve" FeZ DIU vcz vel Fe!. VC:; fHU vez Vel Fez Fe} iJ.abitatt ------Maturc!undisturbed /,r disturbed M M MOD 0 o o o

Exocarpos humifusus (Sa) sOM + +- Hieroc'hloe fraseri (Po) hN -I- -I- (My) sit N ~ -I- Oreobolus acutifolius (Cy) h + -I- Isophysis tasmanica (Ir) hN -I- -I- Euphrasia striata eSc) hN -I- -I- Aceana novae-zelandiae (Ro) hN -I- -I- Areheria serpyllifolia (Ep) s ! 2 2 Lagenophora stipitata (Co) h + + Senecio peetinatus (Co) hN + -I- Epilobium billardierianum (Co) hN -I- -I- Eucryphia lucida (Mo) t Olearia pinifolia (Co) sOM Uncinia tenella (Cy) h -I- Plantago dalton!! (PI) h -I- Anopterus glandulosus (Sax) s Olearia persoonioides (Co) s I Areheria hirtel/a (Ep) Cyathodes juniperina (Ep) s -I- (Li) h -I- Trochocarpa cunninghamii (Ep) -I- Prionotes cerinthoides (Ep) e -I- Grammitis billardieri (Gr) p -I- Phyllocladus aspleniifolius (Pod) Atherosperma mosehatum (At) Archeria eriocarpa (Ep) -I- Telopea truneata (Pr) s Pittosporum bieolor (Pi) sit Blandfordia punicea (Li) h Ranunculus spp, (Ra) hN Plantago spp, (PI) hN Drosera areturi (Dr) hOM Prasophyllum spp, (Or) hN Carpha alpina (Cy) hN peduncularis (Til s Monotoea submutica (Ep) s I Troehocarpa gunnii (Ep) s Diplarrena latifolia (Ir) h Apteropteris applanata (Hy) P Dip/aspis eordifolia (Urn) hN -I- Grammit!s poeppegania (Gr) pN -I-

* Families: As = Aspidaceae, At = Atherospermataceae, BJ = Blechnaceae, Co = Compositae, Cr = Crucifcrae, Cy = Cyperaceae, De = Dennstaedtiaceae, Ep = Epacridaceae, Er = , Fa = Fagaceae, Ge = Gentianaceae, Gr = Grammitidaceae, Hy = Hymenophyllaceae, Ir= Iridaceae, J u = Juncaceae, Mo= Monomiaceae, My = , On = Onagraceae, Or = Orchidaceae, Pi = Pittosporaceae, PI = Plantaginaceae, Po = Poaceae, Pod = Podocarpaceae, Pr = Proteaceae, Ra = Ranunculaceae, Ro = Rosaceae, Ru = Rubiaceae, Sa = Santalaceae, Sax = Saxifragac:eae, Sc = Scrophulariaceae, Ta = , Ti = , Ox = Oxalidaceae, Urn = Umbelliferae, Wi = Winteraceae, t Habit: e = epiphyte, h = herb, p = pteridophyte, s = , t = tree, :j: Habitat (from Jarman et ai, 19S4): B = rainforest bogs, G = gallery rainforest, HAC = high altitude callidendrous rainforest, I = recorded in implicate rainforest, N = not recorded in rainforest, OM = open montane rainforest. 196 p, Cullen

TABLE 3 Summary of Table 2 by Lifeform and Family

Lifefonn Disturbed Undisturbed

Poaceae 11 1 Compo sitae (herbs) j6 6 Compositae (others) 11 4 All herbaceous species 60 27 Epacridaccae (shrubs) 27 2(J

TABLE 4 Seedling Densities (per m2) at the Study Sites

Species Stands*

FCld FCl FC2d FC2 veld VCl ve2d VCl VC3d VC3 DR2d DR2

Athrotaxis seZaginoides 0,]4 0.63 2.16 0.04 0.12 0.27 (J.O? L05 0016 Nothofagus cunninghamii 0.06 (J.l3 0.91 0.10 0.05 0.03 0.07 0,02 0.68 0.13 0.46 nm Atherosperma moschatum 0.02 0.03 Eucryphia Lucida 0.G2 0.04 Eucryphia milliganii 0,05 0.06 0.06 0.04 0.29 Leptospermum scoparium 0.Q2 0.02 .. _-_. * d = disturbed area, nm = not measured.

were not investigated at stand DR2. Phyllocladus - -Nothofagus gunnii aspleniifolius was only recorded in low numbers at communities in the central highlands (author's three of the sites and only once, as a seedling, on a observations). Jarman & Brown (1983) consider that disturbed area. This is somewhat surprising, as P. Eucalyptus species may be able to regenerate in some aspleniifolius is common in disturbed plant communities subalpine environments in the absence of fire. Infrequent in western Tasmania (Kirkpatrick 1977). Read & Hill catastrophic disturbances, such as landslides, may (1988a) found demographic structures for this species provide limited opportunities for Eucalyptus species to to be suggestive of past catastrophic disturbances. The persist without fire in communities that contain virtual absence of P. aspleniifolius from the landslide extremely fire sensitive species. faces may be explained by a lack of seed, as there are Leptmpermurn scoparium is present on all the land· few mature trees of the species in the sun-ounding slides areas at Mt Victoria Cross and there are a few forests. large individuals in the undisturbed forest at stand VCI. The presence of Eucalyptus vernicosa at stand FC 1 L. scopariurn is a common early seral species in and that of Leptospermum scoparium at stands VCI, regenerating podocarp forest in New Zealand (Cameron VC2, and VC3 warrants further discussion. 1960). It has been recorded as a pioneer species on Three E. vernicosa individuals were recorded at stand landslides in southern New Zealand (Mark et ai. 1964). FC I. One is a seedling on the landslide face and two They found that it still occupied an important position adults occur on the site which had been burnt in the in the canopy 50 years after disturbance but that its past. Eucalyptus regeneration is usually associated with lifespan was only approximately 100 years. The success fire but Eucalyptus coccifera has been observed of L. scoparium on these sites was attributed to its high regenerating without disturbance in mixed E. coccifera drought tolerance. Rainforest tree species 011 in Tasmania 197

FCl n", 186 VC1 n "" 189 No Ev Pa As Nc Em 20 ::Ls~10 __ L 1 3 5 7 9 11 13 15 17 l 1 :'I 5 7 9 Sbe Class SiZ6 Class

FC2 VC2 n = 204

No Em Pa Ls L"L_ L

VC3 n =207 FC2 Nc Em Ls Am EI L L L

DR2 n '" 74 As Am EI

! 10 J * ~L ~1 3 5 Sizlt Class

FIG. 2 - Percentage frequency versus size class for tree species recorded on the transects. Size classes are: 1 = <10 mm d.h.h., 2 = 10-95 mm, 3 = 100-195 mm, and so on. Hatched areas represent the proportion of seedlings located on landslide faces. n = total number of stems measured at each stand. Species are: Am = Atherosperma moschatum, As = Athrotaxis selaginoides, Ev = Eucalyptus vemicosa, El = Eucryphia lucida, Em = Eucryphia milliganii, Ls = Leptospermum scoparium, Nc = Nothofagus cunninghamii, Pa = Phyllocladus aspleniifolius. The role of Leptospermum species in Tasmanian The histograms of the size/class structure of the forests rainforest communities remains uncertain. Jarman & investigated are presented in figure 2. The proportion Brown (1983) consider Leptospermum riparium to be of A. selaginoides seedlings occurring on the disturbed a "true" rainforest species in gallery rainforests but the sites and in the undisturbed forest at each site is shown. status of L. nitidum, L. ianigerum, and L. scoparium is The lack of A. selaginoides regeneration and the unclear. These species are largely associated with fire presence of only large-sized A. selaginoides stems in prone vegetation. However, L. lanigerum may be the undisturbed rainforest at all the sites investigated capable of regeneration in rainforest in canopy gaps supports the contention that the species requires canopy created by its own death. Gibson et al. (1987) found disturbances for adequate regeneration in evergreen L.lanigerum to be regenerating in canopy gaps and at rainforest (Cullen 1987a). The forest at Mt Victoria stand edges in swamp forests that may be edaphically Cross is very similar in composition and structure to a deflected climax rainforests. The results of the present stand of evergreen rainforest at Mt Anne (stand A2 in study suggests that L. scoparium could maintain its Cullen 1987b). At the time of documentation there was presence in rainforests, provided that disturbances re­ no canopy disturbance and there were no small-sized occurred within the lifespan of the species. A. selaginoides individuals at the Mt Anne stand. 198 P. Cullen

Likewise, the mature forest at stand Fe2 was similar to peaks in the Southern 255 were counted on the that of stand B3 at Mt Bobs (see Cu] len 1987b) where aerial photographs. occurred in an area of 160 km2 the only A. selaginoides regeneration pfesenl was which supports many and burnt stands of located in a gap caused by the faB of a lnature N. Ii (Brown 1988)_ In addition, there were cunninghamii stem. at least as many small ~feas of disturbed ground which The necessity for canopy disturbance may have been caused failure. The rate at demonstrated at stand DR2. Mature A. which landslides occur could be assessed in the future trees overhang the cliffs above and would if another set of aerial for the to both a gap created by rockfall and tbe region. Observations closed thamnic rainforest A. sClag,IYW'lUl:S landslides are common at the other study is only present on the disturbed area. The ot'ler stands areas and in other cool temperate of A. setagi noides in this area may have been initiated rainforest, for the lower Gordon River Valley in a similar manner. They occur on steep, rocky (Mike Pemberton, pers. comm.) below dolerite crags, are of limited extent and contain no small-sized individuals. Increment cores obtained from individuals at VC3 GENERAL DISCUSSION and DR2 il1dicate that the sites have been open to A. selaginoides recruitment for periods of between 50 and The impact of landslides is likely to be intermediate 100 years. The largest stem at DR2 was aged at a between that of minor events such as treefal! gaps and minimum of 33 years (core extracted at ground level), more extensive events such as . Consequently, but the site appears to be still open to regeneration of landslides are likely to create unique regeneration niches the species. Adjacent to this gap, a group of pole sized in rainforest communities, A. selaginoides and N. cunninghamii stems occupy an At all the sites visited, the extent of canopy disturbance area which appears to have been disturbed over 100 was much greater than that likely to occur with the years ago, This area lacks A. selaginoides seedlings. Two wind throw of one or a small group of trees. In small A. selaginoides stems yielded minimum ages of 50 and canopy gaps, light--demanding species such as A. 112 years (cores extracted I m above ground level), selaginoides will be at a disadvantage. The amount of again indicating a prolonged recruit.ment period. A light reaching the forest floor will be less in small burnt site at Mt Bobs (see Cullen 1987b) appears to canopy gaps, especially as the surrounding adult trees have been open to A. selaginoides regeneration for 60 will have a tendency to expand to occupy the vacant to 70 years, canopy space, causing suppression of regenerating At stand VC3, 15 mature individuals ranging in size seedlings, from 200 to 605 mm d.b.h. were aged. They form part The temperature regime is likely to be more extreme of a stand which is orientated orthogonal to the contours. on a landslide face than in a treefall gap, Nunez & This stand is approximately 15 m wide and 100 m long. Bowman (1986) found that there was little difference Minimum ages for these stems also suggest that they between the nightly minimum temperatures experienced were recruited over a period of approximately 70 years. in unlogged forest and in those where 42% of stems had The stand contains no small stems or seedlings, The been removed, but minimum temperatures were 3-4°C age structure and spatial distribution of the stems lower on an adjacent clear-felled site and resulted in strongly support the contention tbat the stand germinated repeated, severe frosts, In high light, low temperature on a past landslide. situations, A. selaginoides is capable of higher growth It appears that extended periods of A. selaginoides rates than N. cunninghamii, Athero,11Jerma moschatum, seedling recruitment may be nOlmal on catastrophically E. lucida and P. aspleniifolius (Read 1985); it is disturbed sites, The extended recruitment of faster marginally less frost resistant thanN. cunningham!i but growing species would create muiti-age/multi-size class more frost resistant than A, moschatum, E. lucida and stands. However, the extremely slow growth rates and P. aspleniifolius (Read & Hill 1988b). This could the great longevity of A. se/aginoides result in what account, at least in part, for its success as a coloniser of appear to be more or less even-aged stands, despite the landslide sites. The presence of species usually found fact that the individuals have been recruited over a long in open montane rainforests or alpine vegetation may time-period, Stands with size/age structures which can reflect a higher incidence of frost on these sites, Once be attributed to extended recruitment periods have been established, these species would provide the necessary recorded at many locations (Cullen 1987b, Kirkpatrick cover for less hardy species to establish. & Harwood 1980, Ogden 1978, Read & Hill 1988a). Landslides remove all or most of the subcanopy and Landslides were very common on the steep sandstone ground cover. Altematively ,treefalls or canopy damage slopes below the dolerite cliffs which form many of the from wind or snowstorms will leave the subordinate Tree species in Tasmania 199 vegetation more or less intact. Thus, shade-tolerant tree for the development of new stands of the and shrub species which are present in the understorey numbers of landslides have occurred in and survive tile disturbance will be at an advantage. that are an integral On the other hand, disturbances caused by land­ rainforest environment, at least slides will be less extensive than those caused by all but the most localised fires. Unlike fires, landslides are The incidence of landslides and other forms of not likely to create disturbance beyond the seed disturhance which can promote A. dispersal range of poorly dispersed species such as are to have been more common A. selaginoides, and complete clearance of the landslide and imerstadial Thus, the species face will remove those species which can regenerate may have been in these limes. vegetatively following burning, thus reducing the ,.,v'CUlm)', distribution on the landslide faces indicates competition for new seedlings. CUi~mni!.hGil111 can also regenerate on The frequency and extent of catastrophic disturbances, these sites. In addition, landslides provide other than fire, which can create conditions suitable for opportunities for limited regeneration of the regeneration of A. selaginoides are not known. and species. Whether landslides occur Landslides and rockfalls must be considered to be an with sufficient regularity to maintain these minor species integral part of the environment in at least some within rainforest communities is not known. mountainous regions in Tasmania. These events and others, such as windstorms and heavy snowfalls, are ACKNOWLEDGEMENTS likely to be more common in mountain environments than at lower altitudes, and a lack of disturbance events I wish to thank the following people: Sian Smith and suitable for A. selaginoides regeneration may be a Mark Neyland for assistance in the field, Jamie contributing factor controlling the distribution of the Kirkpatrick, who provided constructive criticism and species at low elevations. continued support, Airlie Alam for preparing the The incidence of disturbances which would promote illustrations and Rosie Bickel for typing the manuscript. A. selaginoides regeneration is likely to have been much The project was undertaken through the Department of higher during colder climates prevailing during the last Geography and Environmental Studies, University of glacial and preceding interstadial than at present. Glacial Tasmania and was funded by a grant from the Office of climates produced greater slope instability than occurs the National Estate to the Tasmanian Conservation Trust. now or during most of the Holocene (Kiernan 1985). In Assistance was also provided by the Tasmanian the Cascade Range of northwestern USA, Oliver et al. Department of Parks, Wildlife and Heritage World (1985) found that the alternating advance and retreat of Heritage Directed Research Program. a glacier, rockfalls, avalanches and other events caused widespread disturbance in forested areas adjacent to REFERENCES the glacier. Wardle (1973, 1980) has investigated similar phenomena in New Zealand. The glaciers on the West BEVERIDGE, J.L., 1973: Regeneration of podocarps in central Coast Range of Tasmania, and possibly further inland, North Island podocarp forests. Pmc. NZ Ecol. Soc. would have been similar to those found in New Zealand 11: 48--55. and Patagonia at present (Kiernan 1980, 1985). It is BROWN, M.J., 1988: Distribution and conservation of King Billy . A report to the World Wildlife Fund reasonable to assume that the glaciers in Tasmania . extended down to and below the treeline on occasions, BUCHANAN, A.M., MCGEARy-BROWN, A. & ORCHARD, A.E., creating conditions similar to those reported by Oliver 1989: A CENSUS OF 111E VASCULAR et al. (1985) and Wardle (1973). Disturbance caused by OF TASMANIA. Tasm .. Herb. Oecas. Publ. 2. heavy snowfalls and avalanches is also likely to be BURKE, W.D., 1974: Regeneration of podocarps on Mt increased during a colder climate. Tarawera, Rotorua. NZ J. Bot. 12: 219-226. 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