Evidence of a Holocene and continuing recent expansion of lowland rain forest in humid, tropical North Queensland

Abstract. The identification and radiocarbon dating of charcoal collected under tropical rain forest indicated that sclerophyll forests dominated by Eucalyptus occupied parts of the wet tropical lowlands in the Daintree region of North Queensland at least intermittently from 12,000 yr bp until very recently. The results extend the late Pleistocene expansion of pyrophytic, sclerophyll forests which occurred in the upland rain forests to a humid, megathermic coastal lowlands region. Unlike the early Holocene re-expansion of rain forests which occurred generally on the uplands, the sclerophyll forests in the lowland study area were present until at least 1400 yr bp. Changes in coastal geomorphology and coastline positions during the late Quaternary were examined in the study area by superimposing sea levels derived from published curves on sea-bed contours. The results indicate that a very rapid decrease in the extent of the coastal plain occurred during the late Pleistocene. Between 12,000 and 9000 yr bp, 26 km of the coastal plain was submerged and this would have inevitably resulted in concentrations of Aboriginal populations in the area of the present coastline. It is suggested that burning activities by Aborigines in the coastal lowlands were sufficient to reestablish sclerophyll forests during the latter part of the Holocene from approximately 4000 yr bp following a wanner and wetter period which would have been conducive to rain forest re-expansion. Although the evidence suggests that the most recent rain forest recolonization occurred in the study area more than 1000 years ago, the process is still continuing elsewhere in the wet tropical lowlands in North Queensland. The process of eucalypt forest replacement by rain forest may have accelerated since the arrival of Europeans and the concomitant decrease in Aboriginal management.     

Factors affecting the growth of Eucalyptus delegatensis seedlings in inhibitory forest and grassland soils

In many highland forests of Eucalyptus delegatensis in Tasmania the establishment and healthy growth of eucalypts is promoted and maintained by fire. In the absence of fire, secondary succession from eucalypt forest to rainforest occurs, during which the eucalypts decline and die prematurely. On sites that are prone to radiation frost severe reduction or removal of a tree canopy allows a sward of tussock grasses to develop, in competition with which seedlings of eucalypts decline in growth and a high proportion dies.Factors of the soil that could contribute to these phenomena were investigated by means of pot experiments that used soils from:o     

Chloroplast sharing in the Tasmanian eucalypts

The biogeographic pattern of chloroplast DNA (cpDNA) haplotypes in Eucalyptus on the island of Tasmania is consistent with reticulate evolution, involving at least 12 Tasmanian species from the subgenus Symphyomyrtus. Intraspecific cpDNA polymorphism in 14 of 17 species is coupled with extensive sharing of identical haplotypes across populations of different species in the same geographic area. Haplotype diversity is lowest in central regions of Tasmania formerly occupied by alpine vegetation during glacial intervals and in northern regions that were periodically linked to continental Australia by land bridges. The observed distribution of several cpDNA haplotypes unique to Tasmania coincides with modeled locations of glacial refugia in coastal areas of Tasmania and shows the power of cpDNA in unraveling the complex history of past distributions of Eucalyptus. The results suggest that the model of evolution of the eucalypts should be reassessed to allow for the anastomosing effects of interspecific hybridization and introgression.     

Allocasuarina tree hosts determine the spatial distribution of hypogeous fungal sporocarps in three tropical Australian sclerophyll forests

Across three tropical Australian sclerophyll forest types, site-specific environmental variables could explain the distribution of both quantity (abundance and biomass) and richness (genus and species) of hypogeous fungi sporocarps. Quantity was significantly higher in the Allocasuarina forest sites that had high soil nitrogen but low phosphorous. Three genera of hypogeous fungi were found exclusively in Allocasuarina forest sites including Gummiglobus, Labyrinthomyces and Octaviania, as were some species of Castoreum, Chondrogaster, Endogone, Hysterangium and Russula. However, the forest types did not all group according to site-scale variables and subsequently the taxonomic assemblages were not significantly different between the three forest types. At site scale, significant negative relationships were found between phosphorous concentration and the quantity of hypogeous fungi sporocarps. Using a multivariate information theoretic approach, there were other more plausible models to explain the patterns of sporocarp richness. Both the mean number of fungal genera and species increased with the number of Allocasuarina stems, at the same time decreasing with the number of Eucalyptus stems. The optimal conditions for promoting hypogeous fungi sporocarp quantity and sporocarp richness appear to be related to the presence and abundance of Allocasuarina (Casuarinaceae) host trees. Allocasuarina tree species may have a higher host receptivity for ectomycorrhizal hypogeous fungi species that provide an important food resource for Australian mycophagous animals.     

Native forest regeneration and eucalyptus plantations in the Malagasy Highland

Eucalyptus plantations (EP) offer a number of goods and services that can reduce pressure on native forests. Eucalyptus trees can also be invasive and have a negative impact on native species diversity and regeneration. This article deals with the complex interaction between EP and native forests by studying the case of the humid forests of Malagasy Central High Land that are surrounded by EP. Floristic inventories were carried out on 400 m² plots in adjacent secondary forests (n = 5) and EP (n = 6). Eucalyptus has not spread to secondary forests understory. Native species from secondary forests have colonised EP understory.     

Few Mendelian genes underlie the quantitative response of a forest tree, Eucalyptus globulus, to a natural fungal epidemic

Foliar fungal pathogens from the genus Mycosphaerella affect eucalyptus in natural forests and plantations worldwide. QTL analysis was conducted to dissect the genetic control of resistance in Eucalyptus globulus to a natural infection by Mycosphaerella leaf disease, using a clonally replicated outbred F2 family (112 genotypes) planted in a field trial. Two major QTL, with high LOD support (20.2 and 10.9) and high genomewide significance, explained a large proportion (52%) of the phenotypic variance in the severity of damage by Mycosphaerella cryptica, which may be indicative of oligogenic control. Both QTL were validated in a second F2 family and one was validated in a third F2 family. The mean values of different genotype classes at both major QTL argue for Mendelian inheritance with resistance dominant over susceptibility. There were strong correlations between the levels of Mycosphaerella damage in related genetic material planted in three widely separated locations in Tasmania. These findings together provide evidence that the genes controlling resistance to Mycosphaerella damage are stable in different genetic backgrounds and across different environments.     

Contracting Tasmanian montane grasslands within a forest matrix is consistent with cessation of Aboriginal fire management

The persistence of treeless grasslands and sedgelands within a matrix of eucalypt and rainforest vegetation in the montane plateaux of northern Tasmania has long puzzled ecologists. Historical sources suggest that Tasmanian Aborigines were burning these treeless patches and models seeking to explain their maintenance generally include fire, soil properties and Aboriginal landscape burning. We aimed to provide a new historical perspective of the dynamics of the vegetation mosaics of Surrey Hills and Paradise Plains in north‐west and north‐east Tasmania, respectively, and used vegetation surveys and soil sampling to explore the role of vegetation and soils in these dynamics. Sequences of historical maps (1832 and 1903) and aerial photography showed that many treeless patches have persisted in the landscape since European settlement and that forests have rapidly expanded into the treeless patches since the early 1950s. Stand structure and floristic data described an expanding forest dominated by Leptospermum, which is consistent with vegetation succession models for the region. Soils under expanding forest boundaries did not have higher soil nitrogen or phosphorus than those under stable boundaries, signalling a lack of edaphic limitation to forest expansion. The magnitude of forest expansion at Paradise Plains (granite), Surrey Hills (basalt) and south‐west Tasmania (quartzite) appears to follow a nutrient availability gradient and this hypothesis is backed by differences in soil phosphorus capital between the three systems. Given that existing vegetation boundaries in northern Tasmania do not coincide with soil nutrient gradients, we suggest that treeless vegetation was maintained by Aboriginal landscape burning and that the recent contraction of treeless vegetation is related to the breakdown of these fire regimes following European settlement. The observed rates of forest expansion could result in a substantial loss of these grasslands if sustained through this century and therefore our work supports the continuation of prescribed burning to maintain this high conservation value ecosystem.     

Gene flow of the canker pathogen Botryosphaeria australis between Eucalyptus globulus plantations and native eucalypt forests in Western Australia

Abstract The eucalypt plantation industry in Western Australia provides a unique opportunity to study the movement of pathogens between closely related host taxa. Eucalyptus globulus, a native to Tasmania and south‐eastern Australia, is the predominant species in Western Australian plantations, often being planted adjacent to native forest containing Eucalyptus marginata and Eucalyptus diversicolor. Since the commencement of the plantation industry 20 years ago, several fungal species, previously known only to eastern Australia or overseas, have been reported on E. globulus in Western Australia. Botryosphaeria australis is a newly described species, recently found causing cankers on Acacia spp. in eastern Australia. However, during a routine survey, B. australis was found to be the predominant species associated with E. globulus plantations and native Eucalyptus spp. in Western Australia. In this study, six short simple repeat markers were used to evaluate genetic diversity and gene flow between collections of B. australis from native eucalypt forest and E. globulus plantations at two locations in south‐western Australia. In both cases, there was no restriction to gene flow between the plantations and the adjacent native forest. Botryosphaeria australis has now been isolated from a wide range of hosts across south‐western Australia and was not isolated from E. globulus in Tasmania or South Australia. This extensive distribution and host range suggests B. australis is native to Western Australia. This study demonstrates the ability of a pathogen to move between plantation and forests.     

西班牙桉树林下土小平盘菌复合群中两个独立的种——暗柔膜菌属一新组合及一新种:分类、分子生物学、生态与分布(英文)

土小平盘菌复合群原产澳大利亚,其中两个土生种在西班牙报道,很可能是在18世纪中叶引入西班牙。根据形态学特征和序列分析的结果,建立一个新组合和一个新种,分别定名为Phaeohelotium undulatum comb.nov.和Phaeoh.succineoguttulatum sp.nov.。对其宏观和微观形态特征进行了详尽的描述和图示,ITS rDNA序列分析的结果显示,它们以100%的支持率与Phaeohelotium monticola聚类在同一个分支。文中提供了该复合群Phaeohelotium属5个土生种的分种检索表,并对它们的生态习性与世界分布进行了深入讨论。     

Is decline in high altitude eucalypt forests related to rainforest understorey development and altered soil bacteria following the long absence of fire?

Abstract The objective of this study was to identify attributes of the understorey vegetation, soil root biomass, soil chemistry and microbial community that may be associated with tree decline in high altitude eucalypt forests in Tasmania. The sites studied were in healthy eucalypt forest, forest in decline and forest containing dead eucalypts dominated by rainforest, in north‐east (Eucalyptus delegatensis forest) and in north‐west (Eucalyptus coccifera forest) Tasmania. In both regions bare ground, rock and shrubby species were associated with healthy sites whereas decline sites were associated with moss and a tall understorey with a high percentage cover of rainforest species. Healthy sites had low root biomass in the top 10 cm of the soil profile relative to decline and rainforest sites. Seedlings of high altitude species were grown in rainforest soil (0.314% N and 0.060% P) and healthy eucalypt soil (0.253% N and 0.018% P). The four eucalypt species studied had similar root to shoot ratio in the two soils, but the rainforest species, Nothofagus cunninghamii and Leptospermum lanigerum, had higher root to shoot ratio in the healthy eucalypt than in the rainforest soil. We produced three soil filtrates: (i) fungi and bacteria present; (ii) bacteria only present and; and (iii) sterile, from healthy, decline and rainforest sites in north‐east and in north‐west Tasmania and used linseed as a germination bioassay. Filtrates from the north‐east decline and rainforest sites induced a significantly greater dysplastic germination response than healthy sites in (i) and (ii) filtrates, but this was not found in filtrates from sites in the north‐west. We conclude that while the development of a rainforest understorey and elevated soil root biomass in the long absence of fire is generally associated with high altitude eucalypt decline, altered bacterial and/or chemical attributes of soil are not always associated with high altitude eucalypt decline.     

Patterns of genotype-by-environment interaction in diameter at breast height at age 3 for eucalypt hybrid clones grown for reafforestation of lands affected by salinity

The commercial viability of plantations established for the recovery of saline lands may be supported by the deployment of improved genetic material matched to these particularly challenging environments. Patterns of genotype-by-environment interaction were investigated in a highly unbalanced data set of diameter at breast height at approximately 3 years for a total of 841 genotypes from ten Eucalyptus camaldulensis × Eucalyptus globulus and Eucalyptus camaldulensis × Eucalyptus grandis hybrid families assessed across 21 trials grown on a range of saline and non-saline low rainfall sites from southeast Queensland through central NSW, Victoria, Tasmania and southeast South Australia to southwest Western Australia using factor-analytic mixed-model methods. There was significant heterogeneity among trials in estimates of family variance, genotype-within-family variance, the ratio of family variance to total genetic variance and individual broad-sense heritability. Cluster analyses indicated that family effects were highly correlated across a main group of 19 trials and that most trials fell into two major groups for genotype-within-family effects, with an average correlation among trials within these groups of 0.55. There was, however, no obvious geographical or other explanation for the patterns, suggesting that genotypes should be deployed on the basis of broad-scale adaptation.     

Impact of commercial forest management on geophilous carabid beetles (Coleoptera: Carabidae) in tall,wet Eucalyptus obliqua forest in southern Tasmania

Abstract The impact of silvicultural practices (clearfelling, slash burning and sowing) on carabid beetle communities in tall wet Eucalyptus obliqua forests in southern Tasmania was examined using traplines of pitfalls in a chronosequence of regenerating coupes. Total species richness (n= 18) was modest compared to other temperate forests and was not systematically changed by forest management, although it was considerably lower in 20 year old regrowth than in younger regrowth or old-growth controls, possibly due to habitat simplification. The Shannon-Weiner Index was at a minimum in intermediate aged regeneration. TWINSPAN analysis assisted recognition of beetle communities typical of broad stages in the forest succession, with a major dichotomy between most old-growth sites plus young sites and intermediate plus advanced regeneration sites. Vector fitting of environmental variables in an ordination of the sites by non-metric multidimensional scaling revealed a significant influence for the age of regeneration and litter depth, but not bare ground percentage or soil pH. Survival of carabids in the habitat mosaic created by commercial forestry activity is likely to depend on both reinvasion from edges and survival of individuals in the fire-protected refuges that exist within the coupes. Pioneer species were winged, small in size, and non-endemic whereas the opposite was true of the fauna in the older sites. Carabids in eucalypt forests have good potential as indicators but their seasonality in occurrence demands that sampling be extended over most of the year.     

Detection and visualization of spatial genetic structure in continuous Eucalyptus globulus forest

Visualizing the pattern of variation using microsatellites within a Eucalyptus globulus forest on the island of Tasmania provided surprising insights into the complex nature of the fine-scale spatial genetic structure that resides in these forests. We used spatial autocorrelation and principal coordinate analysis to compare fine-scale genetic structure between juvenile and mature cohorts in a study area, 140 m in diameter, located within a typical, continuous E. globulus forest. In total, 115 juvenile and 168 mature individuals were genotyped with eight highly polymorphic microsatellite loci. There was no significant difference in the level of genetic diversity between cohorts. However, there were differences in the spatial distribution of the genetic variation. Autocorrelation analysis provided clear evidence for significant spatial genetic structure in the mature cohort and significant, but weaker, structure in the juvenile cohort. The spatial interpolation of principal coordinate axes, derived from ordination of the genetic distance matrix between individuals, revealed a spatially coherent family group which was evident in both cohorts. Direct comparison of the genetic structure within each cohort allowed visualization of a shift in the spatial distribution of genetic variation within the population of approximately 10 m. As the shift coincided with the direction of prevailing winds, it is hypothesized that this phenomenon is due to downwind dispersal of seeds and is indicative of the important role of prevailing winds in forcing eastward gene flow in these high-latitude forests.     

Glacial refugia and reticulate evolution: the case of the Tasmanian eucalypts

Tasmania is a natural laboratory for investigating the evolutionary processes of the Quaternary. It is a large island lying 40-44 degrees S, which was repeatedly glaciated and linked to southeastern continental Australia during the Quaternary. Climate change promoted both the isolation of species in glacial refugia, and an exchange between Tasmanian and mainland floras. Eucalyptus is a complex and diverse genus, which has increased in abundance in Australia over the past 100 kyr, probably in response to higher fire frequency. Morphological evidence suggests that gene flow may have occurred between many eucalypt species after changes in their distribution during the Quaternary. This paper summarizes recent genetic evidence for migration and introgressive hybridization in Tasmanian Eucalyptus. Maternally inherited chloroplast DNA reveals a long-term persistence of eucalypts in southeastern Tasmanian refugia, coupled with introgressive hybridization involving many species. Detailed analysis of the widespread species Eucalyptus globulus suggests that migration from mainland Australia was followed by introgression involving a rare Tasmanian endemic. The data support the hypothesis that changes in distribution of interfertile species during the Quaternary have promoted reticulate evolution in Eucalyptus.     

Pollen dispersal from exotic eucalypt plantations

The introgression of genes from exotic species or populations into gene pools of native species is a widespread concern in agricultural systems. This is also an issue of increasing importance in forest systems as there has been a dramatic expansion of tree plantations, which have now reached 180 million ha globally. This has recently occurred in Australia with eucalypts. To help assess the risk of genetic pollution, we assess the pattern of realised pollen dispersal from exotic Eucalyptus nitens plantations into native E. ovata forest in Tasmania. We assessed the frequency of F₁ hybrids in open-pollinated seed collected from native E. ovata trees located at varying distance from three exotic E. nitens plantations in Tasmania. Over 119,000 seedlings were screened for morphological markers diagnostic of each species and the F₁ hybrid. F₁ hybridisation averaged 7.2% within 100 m of the exotic E. nitens, with one native tree reaching 56%, but diminished to 0.7% by 200–300 m and continued at this low level to the limits of the sampling at 1.6 km. The decay in the percentage of interspecific F₁ hybridisation with distance followed a power function with a negative exponent (%F₁ = 91.435distance^–0.789; R²=0.84). Eucalyptus nitens is exclusively pollinated by small insects (smaller than honeybees), which the study shows can disperse pollen over 1.6 km. However, the restriction of most exotic F₁ hybridisation to within 200 m of exotic plantations presents clear opportunities to manage the genetic impacts of plantations on native forests.     

A quantitative description of the forest vegetation on an altitudinal gradient in the Mount Field National Park,Tasmania, and a discussion of its history and dynamics

The aim of this study was to describe the forest vegetation along an altitudinal transect running from 158 m to 1220 m (treeline) in the Mount Field National Park, Tasmania. Eighteen 1 ha plots were sampled along this transect, using a modified point-centred quarter method for species composition and density. Size frequency distributions were used to calculate basal areas. Estimates of relative density, frequency and basal area for each species were combined in to an importance value. The altitudinal ranges of all woody species were determined. The altitudinal temperature lapse rate was measured, and data on soil pH obtained. The initial ‘direct gradient’ analysis revealed relatively well marked discontinuities in the vegetation which were further examined by ordination and classification techniques. The latter provided a simple threefold classification into altitudinal zones. The lower zone reaches from the Park entrance (158 m) to between 600 and 670 m, and comprises tall open forest dominated by Eucalyptus regnans and/or E. obliqua and with a ‘wet sclerophyll’ understorey characterized by Olearia argophylla. The middle zone stretches from c. 670 to 940 m and comprises closed rainforest or ‘mixed’ forest (i.e. with senescent emergent eucalypts) dominated by Nothofagus cunning hamii and Atherosperma moschatum. This zone is characterized by the absence of O. argophylla and the presence of Phyllocladus aspleniifolius. The upper part of this zone constitutes an interdigitating transition to the subalpine forests, usually dominated by E. coccifera and occurring on suitable sites between c. 880 m and the timberline. The transition to subalpine forests is associated with a marked decline in basal area. Species richness (of woody plants) increases with altitude to reach a peak in the sub-alpine zone. This trend is the reverse of that normally encountered elsewhere in the world, and is mainly due to relatively high α and β diversities in the shrub stratum of this zone. The significance of fires, aspect and substrate is discussed in relation to the variations in composition within each zone. The low diversity of Nothofagus-dominated rainforest is thought to be due, in part, to the intense competitive thinning in the eucalypt re-growth phase following burning, and the subsequent ‘capture’ of the Eucalyptus niche by Nothofagus. It is speculated that, in Tasmania, the downhill migrations during the cooling phases of the Pleistocene were associated with extinctions of lowland forest taxa, while uphill migrations during warming phases were associated with speciation on the plateaux of the present subalpine zone. This hypothesis implies that the relative proportions of land area available at different altitudes, now and in the past, have determined the relative rates of speciation and extinction, and hence the altitudinal gradients of species richness.     

Comparison of insects and vertebrates as removers of seed and fruit in a Western Australian forest

Removal from the forest floor of seed or fruit of the six commonest species of trees in upland areas of the northern jarrah forest of Western Australia was studied experimentally. The smallest seeds (Eucalyptus marginata, Allocasuarina fraseriana) were taken by insects (presumably ants). Heavier seeds or fruits (E. calophylla, Banksia grandis, Persoonia longifolia, P. elliptica) were taken more often by vertebrates (presumably srrmll mammals). Seeds of E. calophylla and B. grandis were most preferred by vertebrates, possibly because they have the highest relative concentrations of nitrogen and phosphorus.     

引种桉树对本地生物多样性的影响

桉树以速生和适应多种环境的特性成为世界著名的造林树种.但引种桉树对环境可能产生负面影响,如导致土地退化、地下水水位下降和多样性降低等,特别是对林下本地生物物种多样性的影响及其原因还存有争议.本文对此进行了综述,认为大部分桉树人工林本地物种数量低于天然林,一般不高于乡土树种人工林,但总体上好于其他外来树种人工林.导致桉树人工林生物多样性低的原因主要是桉树的生理生态特性、人类不合理的规划和砍伐等,其中人为因素起主导作用.若根据引种地的群落性质,通过严格的设计和科学管理,可以将这种负面影响最小化.应按照有利于群落正常发育和植被更新的方式栽种桉树人工林,保留天然植被,减少人为干扰,从而减轻引种桉树的负面影响.     

Effects of Clearfell Harvesting on Lucanid Beetles (Coleoptera: Lucanidae) in Wet and Dry Sclerophyll Forests in Tasmania

The effects of commercial forestry harvest and regeneration practices (clearfelling and slash-burning) on the lucanid fauna of the wet sclerophyll forests of southern Tasmania and the dry sclerophyll forests of eastern Tasmania were examined using pitfall catches. Lucanids are saproxylic beetles, dependent on dead, moribund and decaying wood. Samples taken from old-growth forest and from a chronosequence of sites regenerating after logging, in each forest type, were used to compare the species richness and abundance of the lucanid assemblages. In both forest types, species richness and abundance was highest in the youngest regeneration sites (1–3 year), reflecting the species richness of the original and adjacent unlogged forest, lowest in the older (20–25 year) sites, and variable in the old-growth sites. TWINSPAN cluster analysis showed no clear distinction between regeneration and old-growth forest. The post-harvest slash and stump residue provided an important refugium and initial habitat, but our research indicates that some species may not maintain populations in the long term. Our results suggest that most species of lucanids will find a continuous supply of suitable habitat only in old-growth forests; and such species may become less common as clearfell harvesting leads to a replacement of heterogeneous old-growth forest with single-aged monospecific stands. Continuity of supply of wood in all decay stages, the maintenance of sufficient source areas, and biological connectivity between old-growth stands to enable dispersal, are all likely to be essential to maintain lucanid beetle community integrity. If similar principles apply to other saproxylic species of invertebrate, then clearfelling and slash-burning may cause a gradual extinction of an important element of the forest biota.     

The riddle of Tasmanian languages

Recent work which combines methods from linguistics and evolutionary biology has been fruitful in discovering the history of major language families because of similarities in evolutionary processes. Such work opens up new possibilities for language research on previously unsolvable problems, especially in areas where information from other sources may be lacking. I use phylogenetic methods to investigate Tasmanian languages. Existing materials are so fragmentary that scholars have been unable to discover how many languages are represented in the sources. Using a clustering algorithm which identifies admixture, source materials representing more than one language are identified. Using the Neighbor-Net algorithm, 12 languages are identified in five clusters. Bayesian phylogenetic methods reveal that the families are not demonstrably related; an important result, given the importance of Tasmanian Aborigines for information about how societies have responded to population collapse in prehistory. This work provides insight into the societies of prehistoric Tasmania and illustrates a new utility of phylogenetics in reconstructing linguistic history.