Nothofagus Gunnii Research Articles

Natural products isolation studies of the paleoendemic plant species Nothofagus gunnii and Nothofagus cunninghamii

The first natural product isolation studies of Nothofagus gunnii (Hook.f.) Oerst and Nothofagus cunninghamii (Hook.f.) Oerst have been undertaken. A previously unreported stilbene derivative, pinosylvin monoacetate, was isolated from the leaves of N. gunnii, in addition to 14 known compounds; including the flavonoids galangin, pinobanksin, catechin and quercetin; sesquiterpenoids such as, ilicol and (+)-β-costol acetate; 2,4-dihydroxy-6-methoxychalcone and pinosylvin. Four known flavonoid natural products, catechin, quercetin, ayanin, and avicularin were isolated from the leaves of N. cunninghamii. This study reveals that N. gunnii is a rich source of flavonoid, chalcone and stilbene compounds, while primarily hydroxyflavonoid compounds are found in N. cunninghamii. The isolated phytochemicals are consistent with the evolutionary relationships suggested to exist among Nothofagus species.

Climate change reduces resilience to fire in subalpine rainforests.

Climate change is affecting the distribution of species and the functioning of ecosystems. For species that are slow growing and poorly dispersed, climate change can force a lag between the distributions of species and the geographic distributions of their climatic envelopes, exposing species to the risk of extinction. Climate also governs the resilience of species and ecosystems to disturbance, such as wildfire. Here we use species distribution modelling and palaeoecology to assess and test the impact of vegetation-climate disequilibrium on the resilience of an endangered fire-sensitive rainforest community to fires. First, we modelled the probability of occurrence of Athrotaxis spp. and Nothofagus gunnii rainforest in Tasmania (hereon "montane rainforest") as a function of climate. We then analysed three pollen and charcoal records spanning the last 7,500calyear BP from within both high (n=1) and low (n=2) probability of occurrence areas. Our study indicates that climatic change between 3,000 and 4,000calyear bp induced a disequilibrium between montane rainforests and climate that drove a loss of resilience of these communities. Current and future climate change are likely to shift the geographic distribution of the climatic envelopes of this plant community further, suggesting that current high-resilience locations will face a reduction in resilience. Coupled with the forecast of increasing fire activity in southern temperate regions, this heralds a significant threat to this and other slow growing, poorly dispersed and fire sensitive forest systems that are common in the southern mid to high latitudes.

The legacy of mid‐Holocene fire on a Tasmanian montane landscape

AbstractAimTo assess the long‐term impacts of landscape fire on a mosaic of pyrophobic and pyrogenic woody montane vegetation.LocationSouth‐west Tasmania, Australia.MethodsWe undertook a high‐resolution multiproxy palaeoecological analysis of sediments deposited in Lake Osborne (Hartz Mountains National Park, southern Tasmania), employing analyses of pollen, macroscopic and microscopic charcoal, organic and inorganic geochemistry and magnetic susceptibility.ResultsSequential fires within the study catchment over the past 6500 years have resulted in the reduction of pyrophobic rain forest taxa and the establishment of pyrogenic Eucalyptus‐dominated vegetation. The vegetation change was accompanied by soil erosion and nutrient losses. The rate of post‐fire recovery of widespread rain forest taxa (Nothofagus cunninghamii and Eucryphia spp.) conforms to ecological models, as does the local extinction of fire‐sensitive rain forest taxa (Nothofagus gunnii and Cupressaceae) following successive fires.Main conclusionsThe sedimentary analyses indicate that recurrent fires over several centuries caused a catchment‐wide transition from pyrophobic rain forest to pyrophytic eucalypt‐dominated vegetation. The fires within the lake catchment during the 6500‐year long record appear to coincide with high‐frequency El Niño events in the equatorial Pacific Ocean, signalling a potential threat to these highly endemic rain forests if El Niño intensity amplifies as predicted under future climate scenarios.

Relationships among felt scale insects (Hemiptera:Coccoidea:Eriococcidae) of southern beech, Nothofagus (Nothofagaceae), with the first descriptions of Australian species of the Nothofagus-feeding genus Madarococcus Hoy

Species of southern beech (Nothofagus) have been studied extensively because of their importance in understanding southern hemisphere biogeography. Nothofagus species support a diverse assemblage of insect herbivores, including more than 30 described species of felt scales (Eriococcidae). We reconstructed the phylogeny of the Nothofagus-feeding felt scales with nucleotide sequence data and morphology. All but one of the exclusively Nothofagus-feeding species included in the analyses were recovered as a monophyletic group. This clade comprised the genera Chilechiton Hodgson & Miller, Chilecoccus Miller & González, Intecticoccus Kondo, Madarococcus Hoy (except for M. totorae Hoy), Sisyrococcus Hoy and several species of the genus Eriococcus Targioni Tozzetti. The genera Eriococcus and Madarococcus were not recovered as monophyletic. Here we revise Madarococcus. We expand the concept of the genus, provide a key to the adult females of the 31 species of Madarococcus and, for each named species, provide revised synonymies and any new collection or taxonomic information. We recognise the genus from Australia for the first time and describe the adult females of six new Australian species: Madarococcus cunninghamii Hardy & Gullan, sp. nov.; M. meander Hardy & Gullan, sp. nov.; M. megaventris Hardy & Gullan, sp. nov.; M. moorei Hardy & Gullan, sp. nov.; M. occultus Hardy & Gullan, sp. nov., and M. osculus Hardy & Gullan, sp. nov. We also describe the first-instar nymphs of M. cunninghamii, sp. nov., M. meander, sp. nov. and M. moorei, sp. nov. We transfer 17 species into Madarococcus from Eriococcus: M. argentifagi (Hoy), comb. nov.; M. cavellii (Maskell), comb. nov.; M. chilensis (Miller & González), comb. nov.; M. detectus (Hoy), comb. nov.; M. eurythrix (Miller & González), comb. nov.; M. fagicorticis (Maskell), comb. nov.; M. hispidus (Hoy), comb. nov.; M. latilobatus (Hoy), comb. nov.; M. maskelli, (Hoy), comb. nov.; M. montifagi (Hoy), comb. nov.; M. navarinoensis (Miller & González), comb. nov.; M. nelsonensis (Hoy), comb. nov.; M. nothofagi (Hoy), comb. nov.; M. podocarpi (Hoy), comb. nov.; M. raithbyi (Maskell), comb. nov.; M. rotundus (Hoy), comb. nov. and M. rubrifagi (Hoy), comb. nov. We transfer two species from Sisyrococcus into Madarococcus: M. intermedius (Maskell), comb. nov. and M. papillosus (Hoy), comb. nov. One species, M. totarae (Maskell), is excluded from Madarococcus, but cannot at present be placed in another genus and is listed as ‘M.’ totarae incertae sedis. We report the first collection of an eriococcid, M. osculus, sp. nov., on the deciduous beech, Nothofagus gunnii. With respect to biogeography, the results of our phylogenetic analysis are congruent with those obtained from recent analysis of Nothofagus; Australian and New Zealand species of Madarococcus form a monophyletic group to the exclusion of the South American species, suggesting that long-distance dispersal has played an important role in shaping the distributions of both the Nothofagus-feeding felt scales and their hosts.

Holocene Vegetation and Paleoclimatic and Paleomagnetic History from Lake Johnston, Tasmania

Lake Johnston cirque contains some of the best subalpine rainforest in Tasmania. Pollen from the sediments shows Lagarostrobos franklinii, which presently reaches 1040 m, may be a glacial relict. Nothofagus cunninghamii–Nothofagus gunnii subalpine rainforest developed between 9000 and 6000 14C yr B.P., with a maximum at 8700 14C yr B.P. After 6000 14C yr B.P. Nothofagus gunnii became more important, and from 3600 14C yr B.P. sclerophyll and heath components increased. Partial burning of the catchment occurred periodically. Early Holocene climate was warmer and wetter than late Holocene climate. The vegetation and climate changes are similar to those recorded from western South Island New Zealand and Chile. Radiocarbon dates give a sedimentation rate of 0.43 mm/yr. Cores are correlated by magnetic susceptibility. Magnetic ages are assigned by matching with the 14C-dated secular variation master curve for southeastern Australia. Magnetic ages are consistent with the 14C chronology when the former are adjusted by 350 years.

Late-glacial and Holocene record of vegetation and climate from Cynthia Bay, Lake St Clair, Tasmania

A Late-glacial–Holocene pollen record was obtained from a 3.96 m sediment core taken from Lake St Clair, central Tasmania. Modern vegetation and pollen analyses formed the basis for interpretation of the vegetation and climate history. Following deglaciation and before ca. 18450 yr BP Podocarpus lawrencei coniferous heath and Astelia–Plantago wet alpine herbfield became established at Lake St Clair. A distinct Poaceae-Plantago peak occurs between 18450 and 11210 yr BP and a mean annual temperature depression from ca. 6.2°C to 3°C below present is inferred for this period. The marked reduction in Podocarpus and strong increase of Poaceae suggests reduced precipitation levels during the period of widespread deglaciation (ca. 18.5–11 kyr BP). The local Late Pleistocene–Holocene non-forest to forest biostratigraphical boundary is dated at 11.2 kyr BP. It is characterised by expansion of the subalpine taxa Athrotaxis/Diselma with Nothofagus gunnii, and by the establishment of Nothofagus cunninghamii with Eucalyptus spp. A ‘Phyllocladus bulge’ prior to the expansion of Nothofagus cunninghamii, reported at other Tasmanian sites, is not present at Lake St Clair. Nothofagus cunninghamii cool temperate rainforest peaked at 7800 yr BP, probably under wetter climatic conditions than present. The maximum development of rainforest in the early–middle Holocene may indicate that the temperature was slightly warmer than present, but the evidence is not definitive. The expansion of Eucalyptus spp. and Poaceae after 6000 yr BP may be partly a disclimax effect as a result of Aboriginal burning, but appears also to reflect reduced precipitation. The changes in vegetation and inferred climate can be explained by major changes in synoptic patterns of southern Australia and the adjacent southwest Pacific. Copyright © 2000 John Wiley & Sons, Ltd.

Some Effects of Acclimation Temperature on Net Photosynthesis in Some Tropical and Extra-Tropical Australasian Nothofagus Species

The present investigation measured some effects of acclimatation temperature on net photosynthesis in Nothofagus gunnii, N. cunninghamii, N. moorei and some of the fourteen Nothofagus species from New Guinea, in order to determine differences between species which may be correlated with climatic characteristics of their range.

Comparative Responses to Temperature of the Major Canopy Species of Tasmanian Cool Temperate Rain-Forest and Their Ecological Significance .II. Net Photosynthesis and Climate Analysis

Net photosynthesis was measured in foliage of Tasmanian rainforest canopy species grown at 20°C and acclimated sequentially to a range of temperatures. Some trends in photosynthetic response (both instantaneous and acclimatory) correlated with aspects of species' distributions with respect to altitude, latitude and climate, and with their frost resistance. This was particularly evident in Athrotaxis selaginoides D.Don and Nothofagus cunninghamii (Hook.) Oerst. which are common at high altitudes. High-altitude provenances of these species showed a low optimum acclimation temperature (16-17°C) and maintained a high rate of photosynthesis (as a proportion of their maximum rate) at 8°C (84% and 76% respectively). However, the co-occurring winter-deciduous Nothofagus gunnii (Hook. f.) Oerst. showed a higher optimum acclimation temperature for photosynthesis (23°C) and a lower rate of photosynthesis at 8°C (60% of its maximum rate) and is apparently adapted photosynthetically to summer temperature conditions. Provenances of N. cunninghamii showed trends in photosynthetic responses (maxima and responses to extremes) and specific leaf area which correlated with the climate of the collection site and with frost resistance. This population variation may permit the very wide geographic and climatic range of this species, allowing tolerance of extreme temperatures as well as a relatively high competitive ability under more equable climates. Atherosperma moschatum Labill. showed a low photosynthetic tolerance of high and low temperatures compared with the other species. This is consistent with the general restriction of this species to microhabitats with an ameliorated climate and indicates that its wide latitudinal range is not due to a broader photosynthetic tolerance of temperature than co-occurring species. The determinants of the narrow latitudinal range of the Tasmanian endemic species, particularly those which are common at low altitudes (Phyllocladus aspleniifolius (Labill.) Hook, f., Eucryphia lucida (Labill.) Baill. and Lagarostrobos franklinii (Hook. f.) C.J. Quinn are less clear. Limited acclimation to high temperatures in E. lucida (and P. aspleniifolius under some conditions), and in the high altitude species, N. gunnii and A. selaginoides, suggests that the sensitivity of these species to high summer temperatures may directly limit their distribution. However, interpretation of the sensitivity of these species to high summer temperatures and low precipitation shown by the climate analysis is complicated by the interactions of these climatic features with the incidence of fire.

Phenology and germination in some rainforest canopy species at Mt Field National Park, Tasmania

The timing of shoot expansion, flowering, germination and leaf fall was recorded in some rainforest canopy species at Mt Field National Park, Tasmania. Seed collected from these and two other species was germinated in Hobart under controlled conditions. Most of the variation in phenology and germination requirements was continuous and correlated broadly with distribution with respect to the temperature climate. The species which commonly occur at high altitudes -Athrotaxis selaginoides, A. cupressoides, Nothofagus gunnii and N. cunninghamii-germinated earlier at low temperatures than the others, with provenance variation indicated in N. cunnillghamii. The cold-sensitive species Atherosperma moschatum failed to germinate at low temperatures, with a secondary dormancy indicated. Atherosperma moschatum and Phyllocladus asplelliifolius showed delayed shoot expansion during the cool growing season of 1984-85 which rendered the shoots more frost-sensitive. The periodicity of seed production is also greatest in the high altitude species, although the ecological implications are uncertain with respect to climate. Only P. aspleniifolius shows evidence of prolonged seed dormancy. This characteristic enables the populations to survive large-scale disturbance as soil-stored seed and therefore is an important feature of the regeneration ecology of this species.

Regeneration Patterns in Populations of Athrotaxis selaginoides D. Don. from Tasmania

Athrotaxis selaginoides is an emergent tree in cool temperate rainforests of western and southern Tasmania. The species is found growing with evergreen tree species and the deciduous tree Nothofagus gunnii, in a variety of rainforest communities. The regeneration strategy of A. selaginoides is investigated through an examination of the demographic structure and the floristic composition of fifteen widely located stands throughout Tasmania. A. selaginoides relies on gap formation or catastrophic disturbance for regeneration opportunities in forests dominated by evergreen tree species. However, in forests containing a high proportion of the deciduous tree, N. gulnnii, A. selaginoides regenerates continuously. It appears that low light levels beneath undisturbed evergreen rainforest canopies inhibit the regeneration of the species, while the lower, more open, forests dominated by N. gunnii allow greater light penetration to the forest floor.

PHOTOSYNTHETIC RESPONSES TO LIGHT OF AUSTRALIAN AND CHILEAN SPECIES OFNOTHOFAGUSAND THEIR RELEVANCE TO THE RAINFOREST DYNAMICS

SummaryPhotosynthetic responses to light have been examined in nine temperate rainforest species, includingNothofagusspecies from Australia and Chile, in order to correlate comparative light requirements with regeneration patterns and forest dynamics.Nothofagus gunnii(Hook. f.) Oerst. has the highest light requirements of the AustralianNothofagusspecies and this correlates with its failure to regenerate in closed forest.N. alpina(Poepp. et Endl.) Oerst. is the most shade‐tolerant of theNothofagusspecies examined in this study, and this result conforms with regeneration patterns observed in Chilean rainforest. The Australian species,N. cunninghamii(Hook.) Oerst. andN. moorei(F. Muell.) Krasser, and the Chilean species,N. obliqua(Mirbel) Oerst. andN. dombeyi(Mirbel) Oerst., have similar photosynthetic characteristics. Consequently, the comparative light requirements of theNothofagusspecies described here do not explain differences in the dynamics of rainforests dominated by these species. Differences in the regeneration characteristics of co‐occuring understorey and shade‐tolerant canopy species appear to be more important determinants of the dynamics of these forests.

Dendrochronological characteristics of some native Australian trees

Summary Collections of cores and discs from trees were used to identify species and methods best suited for dendrochronological studies in Australia. Three Tasmanien species, Phyllocladus aspleniifolius, Athrotaxis cupressoides, and A. selaginoides, offer excellent potential, having clear rings that can be accurately dated, ages over 500 years, and variations in ring width that can be related to climatic factors. Nothofagus gunnii occasionally can be dated, although ages over 300 years are unlikely. Dacrydium franklinii, the oldest of Australian conifers, has clear annual rings but little year-to-year variability. Crossdating in Callitris is hindered in many areas by false rings, but has been successful at 2 sites near Perth. Growth rings are of varying quality in different Eucalyptus species, but may be crossdated in some areas.