Early primary succession on Mount St. Helens,Washington, USA

Abstract. The north slope of Mount St. Helens was sampled with 141 circular 100-m² plots to describe vegetation and environmental patterns 13 yr after the 1980 eruption. At least 114 vascular plant taxa were encountered. We recognized four habitat types: Refugia, Pumice barrens, Pyroclastic surfaces and Drainages. A fifth category, Lupine patches, includes samples on primary surfaces that were rapidly colonized. Refugia provided small enclaves where underground portions of several species survived the eruption. They retained an inconsistent array of forest understory species and contained 86 species (mean = 20.8 per plot). Refugia are dominated by woody species such as Penstemon cardwellii, Rubus spp., Ribes spp. and Alnus sinuata, with herbs such as Agrostis diegoensis, Luzula parviflora and Anaphalis margaritacea. Anaphalis represents a suite of species that invaded Refugia after the eruption. Diversity (N₂ and H′) is significantly greater in Refugia than in any other habitat. No plants survived on primary sites, which remain sparsely vegetated and dominated by readily dispersed taxa. Total richness ranges from 36 species (9.9 per plot) on pyroclastic surfaces, through 42 species (11.2 per plot) in drainages, to 66 (11.7 per plot) on Pumice barrens. H′ and N₂ of the three habitats do not differ significantly. Lupine-dominated vegetation occurs sporadically in Pyroclastic and drainage habitats. Lupine patches are characterized by high Lupinus cover and a suite of invaders. These sites have high cover and 52 species (12.6 per plot). H′ and N₂ scores were significantly lower than any other habitat due to strong lupine dominance. Canonical Correspondence Analysis showed that site history and slope contributed most to species composition. Geographic effects accounted for 10 25 % of the explained species-environment relationship. Forest understory species have migrated only short distances and have made negligible contributions to vegetation development. A few species common in Refugia, including Agrostis diegoensis and Carex mertensii, have invaded barren surfaces, but most have not. Refugia also have been invaded by open site species abundant on the Pumice Plain. The heterogeneity of plots within habitat types and small statistical linkage of vegetation to environmental and spatial factors suggests that stochastic events have played a leading role in early primary succession.     

Long‐term dynamics of the long‐lived conifer Libocedrus bidwillii after a volcanic eruption 2000 years ago

Abstract. Question: Following a volcanic eruption of ca. 232 AD, known as the Taupo eruption, the emergent conifer Libocedrus bidwillii expanded on Mt. Hauhungatahi, upwards above the current tree‐line, and downwards into the mixed montane forest. We ask: (1) if current age‐structures at different altitudes support the patterns predicted by the temporal stand replacement model, with cohort senescence and progressively depleting recruitment at ca. 600 year intervals (average cohort age) since the eruption: and (2) if the case history of the population sheds light on the persistence of mixed conifer‐hardwood forests in general. Location: Mt. Hauhungatahi, Tongariro National Park, New Zealand. Methods: The species composition and structure of seven stands covering the altitudinal range of Libocedrus bidwillii, were quantified. Libocedrus trees were cored, and regression equations used to predict ages. Cohorts were identified. Results: Libocedrus densities and basal areas, and the abundance of seedlings and saplings, peaked at different altitudes. At the species’lower limits there has been no recruitment for ca. 550 years, and the angiosperm Weinmannia racemosa has gained dominance. In the tree line and sub‐alpine forest stands, a low level of continuous regeneration has been boosted by periodic cohort recruitment following exogenous disturbances. Conclusions: In the montane zone, the Libocedrus age structure, and its replacement by Weinmannia, are consistent with a model of depleting cohorts separated by ca. 600 years since the Taupo eruption. At higher altitudes more frequent disturbances and reduced competition have allowed Libocedrus persistence. Comparison with other studies suggests long‐term relationships between gymnosperms and angiosperms are mediated by the scale and frequency of disturbance.     

The effects of the Taupo Tephra eruption of c. 1718 bp on the vegetation of Mt Hauhungatahi, central North Island, New Zealand

Abstract. An altitudinal series of eleven fine resolution pollen diagrams were used to examine the role of volcanism in forest dynamics on Mt Hauhungatahi. Partial pollen diagrams from four of these sites, chosen to illustrate the major effects of the 1718 bp Taupo eruption, are presented. Following the eruption Libocedrus bidwillii expanded in all sites. Open sites created by the eruption may have facilitated an expansion already underway as a result of more variable climatic conditions since c. 3000 bp . Weinmannia racemosa invaded upper montane forest c. 650 bp . The current altitudinal sequence of forest types, with Libocedrus dominating the subalpine and Weinmannia the upper montane forests, has thus been synthesized only within the last 1800 years. This is interpreted as a consequence of individualistic species' responses to major disturbance by the eruption. The results support nonequilibrium theories of community composition.     

Regional tectonics, disturbance, and population size of isolated stands of Nothofagus fusca (Nothofagaceae) in a forest ecotone in south-western New Zealand

Aim New Zealand's cool temperate forests are usually dominated by one or more of the five native taxa of Nothofagus (Nothofagaceae; southern beech), but in certain regions there are sharp boundaries against podocarp–broadleaved forest where Nothofagus is rare or completely absent, either for historical (Pleistocene Glaciation) or climatic/biological (mild superhumid climate and competition) reasons. The dynamics of a Nothofagus boundary was investigated by monitoring disturbance-initiated establishment of isolated stands of N. fusca at the extreme limits of its regional distribution. Location The research was carried out in a regional forest ecotone between Nothofagus forest and podocarp–broadleaved forest in the upper Taramakau Valley, South Island, New Zealand. The survey region straddles a major, active fault system and associated tectonic movements and earthquakes with more distant epicentres have contributed to intermittent canopy disturbance of the local forests. Methods Isolated stands of Nothofagus fusca beyond the limits of continuous Nothofagus forest were investigated during two field surveys, separated by 7–10 years. Changes in population size, stem diameter of individual trees, stand basal area and mean annual diameter increment were calculated for each of fifty-four isolated stands. Types of past and recent disturbance and the probable cause of mortality of trees were noted. Results The total population of fifty-four sample stands, ranging in size from one to > 400 stems, increased by 37.4%, and compound basal area increased by 4.7% between the two surveys. Mean stem diameter growth of isolated stands was lower than expected by empirical data for N. fusca, suggesting reduced wood increment at the limits of its distribution. Tree mortality was 0.8% per year. Fifty-one per cent of the dead stems had died as a consequence of various types of natural disturbance, uproots being more common than snaps and crown breakage. Main conclusions The isolated N. fusca stands preferentially occupy sites likely to experience intermittent disturbance, mostly including disturbance of the soil cover, which facilitates their initial establishment and persistence. Because of causal relationships between mass movement on steep slopes and erosion/deposition of talus fans and river terraces, disturbance-initiated changes in forest composition are observed across a range of different landforms.     

Climatic relationships of some New Zealand forest tree species

Abstract. A dataset of some 10 000 plots was used to describe the climatic relationships of 33 widespread New Zealand tree species. Estimates of mean annual temperature, temperature seasonality, mean annual solar radiation, and moisture balance were derived from mathematical surfaces fitted to climate station data. Plots were also categorized into five lithological classes and three drainage classes. Generalized additive models were used to examine species/environment relationships. Mean annual temperature and mean annual solar radiation are most strongly correlated with current tree distributions, followed by moisture balance, temperature seasonality, lithology, and drainage. Most broad-leaved tree species other than Nothofagus spp. reach their greatest levels of occurrence in warm, moist environments with high solar radiation. In contrast, Nothofagus spp. generally reach their greatest levels of occurrence in cooler and/or lower insolation environments, and all have lower levels of occurrence on rhyolitic substrates which have resulted from large-scale geomorphic disturbance, mostly over the past few thousand years. Although coniferous species have widely differing climatic optima, many are biased towards lithological classes characterized either by large-scale geomorphic disturbance or harsh edaphic conditions. The relevance of these results to particular synecological questions is briefly discussed. Continuing adjustments in the range of slow-dispersing Nothofagus spp. are strongly suggested, and the climatic suitability of extensive rhyolitic basins in the central North Island, from which these species are largely absent, is confirmed.     

Late-glacial and Holocene vegetation history of the Magellanic rain forest in southwestern Patagonia,Chile

A ¹⁴C-dated high-resolution palaeoenvironmental record from a mire in southern Chile is used to reconstruct the Late-glacial and Holocene vegetation history of the Magellanic rain forest. The Late-glacial environment after around 15400–13500 cal b.p. was dominated by Gunnera magellanica, Nothofagus species (dombeyi type) and Gramineae (Poaceae) indicating an open parkland with cool and damp climatic conditions. At the end of the Late-glacial there was an increase in G. magellanica and a decline in Nothofagus dombeyi type. This ecological signal is interpreted as a result of a re-advance of the Gran Campo Nevado icefield, caused by either Younger Dryas cooling or a latitudinal shift of the southern Westerlies. After around 11250–10750 cal b.p. Nothofagus species, Drimys winteri and Embothrium coccineum expanded, indicating development of the Magellanic rain forest. At 4254±120 cal b.p. a tephra layer was deposited by the eruption of the Mt. Burney volcano leading to a long-term decline of the Nothofagus forest. A primary succession was then initiated, lasting for over 800 years before pre-eruption vegetation patterns redeveloped. In summary, our results indicate the extreme sensitivity of the Magellanic rain forest to climatic or volcanic impacts and the slow recovery of a mature forest after environmental changes.     

Are New Zealand's Nothofagus species in equilibrium with their environment?

Abstract. Past explanations of the large disjunctions in the distribution of New Zealand's four Nothofagus species have emphasized displacement during glacial cycles followed by slow re-occupation of suitable sites, or the effects of plate tectonics coupled with ecological and/or environmental limitations to further spread. In this study the degree of equilibrium between Nothofagus distribution and environment was compared with that of other widespread tree species by statistical analysis. Generalized additive regression models were used to relate species distribution data to estimates of temperature, solar radiation, soil water deficit, atmospheric humidity, lithology and drainage. For each species, the amount of spatial patterning remaining unexplained by environment was assessed by adding a variable describing species presence/absence on adjacent plots. Results indicate that Nothofagus species occur more frequently in environments suboptimal for tree growth, i.e. having various combinations of cool temperatures, low winter solar radiation, high root-zone water deficit, low humidity, and infertile granitic substrates. Despite these demonstrated preferences, they exhibit substantially more spatial clustering which is unexplained by environment, than most other widespread tree species. Predictions formed from regressions using environment alone confirm that several major Nothofagus disjunctions are not explicable in terms of the environmental factors used in this analysis, but more likely reflect the effects of historic displacement coupled with slowness to invade forest dominated by more rapidly dispersing endomycorrhizal species. The technique used in this study for detecting residual spatial autocorrelation after fitting explanatory variables has potentially wide application in other studies where either regression or ordination techniques are used for analysis of compositional data.     

Changes in rain forest tree diversity, dominance and rarity across a seasonality gradient in the Western Ghats, India

Aim We assessed the effects of latitude, altitude and climate on the alpha diversity of rain forest trees in the Western Ghats (WG) of India. We tested whether stem densities, dominance, the prevalence of rarity, and the proportion of understorey trees are significantly correlated with alpha diversity. Location The WG is a chain of mountains c. 1600 km in length, running parallel to the western coast of the Indian peninsula from above 8° N to almost 21° N latitude. Wet forests occur as a narrow strip in regions with heavy rainfall. Methods To assess tree diversity we used data from 40 small plots, < 1 ha in area, where all trees ≥ 3.18 cm d.b.h. had been inventoried. These plots were distributed across 7 latitudinal degrees and at elevations between 200 and 1550 m. Fisher's alpha was used as a measure of diversity. For each plot, the proportion of trees belonging to the understorey, the proportion of trees belonging to the most abundant species in the plot, as a measure of dominance, and the proportionate representation of singletons, as a measure of rarity, were estimated, and correlated with Fisher's alpha, elevation, rainfall and seasonality. Results Annual rainfall and seasonality increased towards the north, but were not significantly correlated. Tree diversity increased significantly with decreasing seasonality. Tree diversity was not significantly correlated with stem density or with the proportion of understorey tree species, but was significantly correlated with tree dominance and rarity. Dominance increased and rarity significantly decreased with increasing seasonality. Main conclusions This study demonstrates that seasonality influences rain forest tree diversity in the WG of India. The relationship between alpha diversity, dominance and rarity lends correlative support for the Janzen–Connell pest pressure hypothesis.     

Dynamics of Nothofagus-dominated rainforest on mainland Australia and lowland Tasmania

Cool temperate rainforest in Australia is commonly dominated by Nothofagus species. In Victoria and Tasmania, Nothofagus cunninghamii dominates old rainforest on optimal sites and is able to regenerate continuously. Size structure analysis of the major lowland tree species in this forest suggest that no major changes in species composition or dominance are occurring. This contrasts with the status of Nothofagus in lowland rainforest in New Zealand and rainforest below about 1000 m a.s.l. in south-central Chile. N. cunninghamii is a relatively light-demanding species, and is maintaining its dominance by seedling regeneration in canopy gaps created by the death of old individuals. The dynamics of the cool temperate rainforest in northern New South Wales are more complex. These forests are dominated by Nothofagus moorei, and size structure analysis indicates that persistence of this species within the rainforest is dependent on vegetative regeneration. On some sites this rainforest is being actively invaded by warm temperate and sub-tropical elements from lower altitudes. In these areas N. moorei in unable to regenerate beneath the canopy.Nomenclature follows Curtis (1963, 1967), Curtis & Morris (1975) and Williams (1982).We thank Mr. A. Floyd of the N.S.W. National Parks and Wildlife Service for his assistance in identifying species from the N.S.W. rainforests, and Mr. J. Hickey of the Tasmanian Forestry Commission for suggesting study sites in north-west Tasmania. Thanks are also due to the N.S.W. National Parks and Wildlife Service for allowing us access to National Parks for the purpose of this study. J. R. is supported by a Commonwealth Forestry Post-graduate Research Award.     

Does soil determine the boundaries of monodominant rain forest with adjacent mixed rain forest and maquis on ultramafic soils in New Caledonia?

Aim To determine the soil characteristics of Nothofagus‐dominated rain forests in an ultramafic region (i.e. soils having high concentrations of metals including Mg, Fe and Ni), and whether soil characteristics may explain the location of monodominant rain forest in relation to adjacent mixed rain forest and maquis (shrub‐dominated vegetation). Location New Caledonia. Methods Soil characteristics were compared among six Nothofagus‐dominated rain forests from a range of altitudes and topographic positions. At four of these sites, comparisons were made with soils of adjacent mixed rain forest and maquis. Results Soil characteristics varied among the monodominant Nothofagus forests, largely due to differences between ultramafic soils and soils influenced by non‐ultramafic intrusions. The soils of all vegetation types had low concentrations of nutrients, particularly P, K and Ca (both total and extractable/exchangeable), and high total concentrations of Ni, Fe, Cr and Mn. There were significant differences between the rain forests and adjacent maquis in soil concentrations of several elements (N, P, Ca, Mg and Mn), more so in surface soils than at depth, but much of this pattern may be caused by effects of vegetation on the soil, rather than of soil on the vegetation. However, there were no significant differences in soil concentrations of any mineral elements between Nothofagus forest and adjacent mixed rain forest. Main conclusions We found no evidence for soil mediation of boundaries of Nothofagus rain forest with mixed rain forest, and little evidence for the boundaries of either forest type with maquis. We suggest that the local abrupt boundaries of these monodominant Nothofagus forests are directly related to temporal factors, such as time since the last wildfire and frequency of wildfire, and that disturbance is therefore a major causal factor in the occurrence of these forests.     

Does leaf-level nutrient-use efficiency explain <Emphasis Type="Italic">Nothofagus</Emphasis>-dominance of some tropical rain forests in New Caledonia?

Tropical rain forests generally have a complex structure and a high diversity of species in their canopy, but in some rain forests the upper canopy is dominated by a single species. The factors controlling this dominance are uncertain. In New Caledonia, Nothofagus species dominate the upper canopy of some rain forests on ultramafic soils. Here we investigate whether leaf-level nutrient-use efficiency (NUE) could explain dominance by Nothofagus. We found no evidence of a competitive advantage in Nothofagus in terms of leaf-level NUE: Nothofagus species did not have lower leaf macronutrient concentrations, nor did they resorb more nutrients than co-occurring species on average. They did, however, have lower foliar Ni concentrations on average. Leaf decay rate across all species in a glasshouse-based trial correlated positively with foliar P and negatively with cell wall content, lignin:P, C:P, lignin:N, leaf toughness and tannin activity. Multivariate analysis suggested that total cell wall concentration exerted the strongest independent effect on variation among species in decomposition rate. Slow decomposition of Nothofagus leaf litter may facilitate continued dominance of the upper canopy by suppressing establishment and growth of co-occurring species or by promoting disturbance through fire, since disturbance has been suggested as necessary for regeneration and maintenance of dominance by Nothofagus species. However, the biological mechanisms allowing Nothofagus to achieve initial dominance of these post-disturbance forests are uncertain, and may still include plant-level NUE.     

Contrasting responses to water deficits of Nothofagus species from tropical New Guinea and high‐latitude temperate forests: can rainfall regimes constrain latitudinal range?

Aim Comparative responses of Nothofagus species to water deficits were studied to determine whether rainfall regimes could limit the latitudinal ranges of tropical and temperate forest species. Location The study species are native to New Guinea, New Caledonia, Australia, New Zealand, Chile and Argentina. Methods Seedlings of Nothofagus species from a broad latitudinal range were grown in a common environment. Changes in conductance, relative water content and water potential were measured in detached shoots, and together with measurements of tissue injury and biomass allocation, were compared between tropical and temperate species. Results Differences in responses to water deficits between tropical and temperate species appear to reflect differences in climate regimes. In particular, species native to ever‐wet rainfall regimes in New Guinea, where water deficits are generally likely to be short‐lived, were effective at conserving water by reduced stomatal conductance. In contrast, high‐latitude evergreen species on average showed greater development of traits that should enhance water uptake. This was particularly evident in Nothofagus cunninghamii from southern Australia, which developed low water potentials at moderate levels of tissue water deficit and higher root:leaf biomass than tropical species, potentially allowing carbon assimilation to be maximized during warmer, but drier, summer months. However, water relations varied among high‐latitude species. In particular, deciduous species on average showed higher rates of conductance, even during moderate levels of tissue water deficit, than evergreen species. Main conclusions The tropical species appear to conserve water during periods of water deficit (relative to temperate species), which is unlikely to have substantial opportunity costs for growth in ever‐wet climates. However, spread of tropical species to higher latitudes may be limited by water conservation strategies that limit carbon gain in climates in which temperature seasonality is often paired with drier summers. Evergreen species from high latitudes, such as N. cunninghamii, commonly showed traits that should increase water uptake. However, this strategy, while probably maximizing growth in temperate climates with cool winters and drier summers, must limit competitiveness at lower latitudes in summer‐wet climates. We conclude that responses to water regimes may make a significant contribution to the latitudinal limits of some evergreen rain forest species.     

西双版纳勐腊望天树热带季节雨林蕨类植物组成及生态特征

采用生态学样方调查及统计学方法,研究了云南勐腊望天树热带季节性雨林蕨类植物的组成及生态特征。结果表明:在1hm2(4个50m×50m,含400个5m×5m小样方)面积的样地里,记录有蕨类植物48种13 159株(丛);在生态特征上,40个地生蕨类的盖度之和占调查样地面积的22.45%,缺乏高盖度级种类;黑鳞轴脉蕨、长叶实蕨、多形叉蕨等属高频度级种类;长叶实蕨、多形叉蕨、黑鳞轴脉蕨、毛柄短肠蕨、薄叶牙蕨、思茅叉蕨等种的重要值之和占86.31%,它们是望天树林蕨类植物的典型代表种。生活型组成上,以地面芽植物占优势(达80%)。叶质主要由纸质叶(占54.17%)和草质叶(占27.08%)种类组成;叶形主要由羽状复叶种类组成(89.58%)。与西双版纳相同取样面积的山地常绿阔叶林比较,望天树林蕨类植物的种数及种群数量分别是山地常绿阔叶林的1.55倍及2.23倍。同一地区不同海拔和生境异质性是导致蕨类植物组成不同、种群数量变化的主要原因。该研究揭示了赤道热带北缘热带雨林蕨类植物的组成及生态特征,有利于与其它热带地区蕨类植物作进一步的比较研究。     

The abundance,distribution and structural characteristics of tree‐holes in Nothofagus forest,New Zealand

Tree‐holes provide an important microhabitat that is used for feeding, roosting and breeding by numerous species around the world. Yet despite their ecological importance for many of New Zealand's endangered species, few studies have investigated the abundance or distribution of tree‐holes in native forests. We used complementary ground and climbed tree surveys to determine the abundance, distribution and characteristics of tree‐holes in undisturbed Nothofagus forest in the Lewis Pass, New Zealand. We found that hole‐bearing trees were surprisingly abundant compared with many other studies, including Australian Eucalyptus species and American beech. In fact, we estimated as many as 3906 tree‐holes per hectare, of which 963 holes per hectare were potentially large enough to provide roost sites for hole‐nesting bats in New Zealand, while only eight holes per hectare were potentially suitable for specialist hole‐nesting birds. This was of great interest as primary cavity‐excavating animals are absent from New Zealand forests, compared with North America and Australia. Moreover, tree‐hole formation in New Zealand is likely to be dominated by abiotic processes, such as branch breakage from windstorms and snow damage. As has been found in many other studies, tree‐holes were not uniformly distributed throughout the forest. Tree‐holes were significantly more abundant on the least abundant tree species, Nothofagus fusca, than on either N. menziesii or N. solandri. In addition to tree species, tree size was also an important factor influencing the structural characteristics of tree‐holes and their abundance in this forest. Moreover, these trends were not fully evident without climbed tree surveys. Our results revealed that ground‐based surveys consistently underestimated the number of tree‐holes present on Nothofagus trees, and illustrate the importance of using climbed inspections where possible in tree‐hole surveys. We compare our results with other studies overseas and discuss how these are linked to the biotic and abiotic processes involved in tree‐hole formation. We consider the potential implications of our findings for New Zealand's hole‐dwelling fauna and how stand dynamics and past and future forest management practices will influence the structural characteristics of tree‐holes and their abundance in remnant forest throughout New Zealand.     

Diversity of forest vegetation across a strong gradient of climatic continentality: Western Sayan Mountains, southern Siberia

Southern Siberian mountain ranges encompass strong climatic contrasts from the relatively oceanic northern foothills to strongly continental intermountain basins in the south. Landscape-scale climatic differences create vegetation patterns, which are analogous to the broad-scale vegetation zonation over large areas of northern Eurasia. In their southern, continental areas, these mountains harbour forest types which potentially resemble the full-glacial forests recently reconstructed for Central Europe. To identify forest vegetation–environment relationships in the southern Siberian mountain ranges, forest vegetation of the Western Sayan Mountains was sampled on a 280 km transect running from the northern foothills with oceanic climatic features to the continental Central Tuvinian Basin in the south. Based on the species composition, vegetation was classified into hemiboreal forests, occurring at drier and summer-warm sites with high-pH soil, and taiga, occurring at wetter, summer-cool sites with acidic soil. Hemiboreal forests included Betula pendula-Pinus sylvestris mesic forest, Larix sibirica dry forest and Pinus sylvestris dry forest. Taiga included Abies sibirica-Betula pendula wet forest, Abies sibirica-Pinus sibirica mesic forest and Pinus sibirica-Picea obovata continental forest. Hemiboreal forests were richer in vascular plant species, while taiga was richer in ground-dwelling cryptogams. Vegetation–environment relationships were analysed by indirect and direct ordination. Winter and summer temperatures and precipitation exerted a dominant influence on species composition. Soil pH was also an important correlate of species composition, but this factor itself was probably controlled by precipitation. At a more local scale, the main source of variation in species composition was topography, producing landscape patterns of contrasting plant communities on slopes of different aspects and valley bottoms. The response of tree species to major environmental factors was expressed with Huisman–Olff–Fresco models. Larix sibirica appeared to be most resistant to drought and winter frosts, Pinus sibirica was adapted to low temperatures both in winter and summer, and Picea obovata had an intermediate response to climate. Betula pendula, Pinus sylvestris and Populus tremula were associated with the warmest sites with intermediate precipitation, while Abies sibirica was the most moisture-demanding species, sensitive to deep winter frosts.     

Two decades of compositional and structural change in deciduous old-growth forests of Indiana,USA

Aims Using a network of permanent plots, we determined how multiple old-growth forests changed over an 18–19-year period at a state-wide scale. This examination of change allowed us to assess how the compositional and structural stability of each forest varied with site characteristics (topography, physiography and productivity) and stochastic disturbance.Methods In 2011, we resampled 150 plots distributed across five old-growth hardwood forests in Indiana, USA that were originally sampled in 1992–1993. Within each plot, we relocated and remeasured the diameter at breast height (dbh) of all trees (≥10.0cm) present during the 1992–1993 sample, which allowed us to track their individual fates through time for growth and mortality calculations. Trees that grew to ≥10.0cm dbh since plot establishment were designated as ingrowth. The dbh and species of all saplings (stems ≥2.0cm but <10.0cm dbh) were also recorded. For each forest, we calculated density (stems ha^-1), basal area (BA; m 2 ha^-1) and importance value (relative density + relative BA)/2) of trees by species. For saplings, density per ha was calculated by species for each forest. We also calculated annual mortality rate (AMR) for three diameter classes (10–29.9, 30–59.9 and ≥60cm) and species richness (S), evenness (E) and Shannon–Weiner diversity (H?) for the tree and sapling layers. Differences between years were compared for each forest using paired t -tests and Wilcoxon signed rank tests.Important findings Although we observed commonality in changes across some sites, our results suggest that these forests differ in their rates and trajectories of change. Changes in total stand BA and density varied across sites and were influenced by past disturbance and mortality rates. We observed a general increase in the overstory dominance of Acer saccharum coupled with a general decrease in the dominance of Quercus section Lobatae (red oak group) species. Mortality of overstory trees present in 1992–1993 ranged from 27% to 49% over the study period (mean AMR 1.6–3.7%). Most sites experienced greater mortality of early and mid-successional species, but one site experienced heavy mortality of Fagus grandifolia, a shade-tolerant late-successional species. Shade tolerant species, A. saccharum in particular, dominated the sapling layer at most sites. However, recruitment of this species into larger size classes did not occur uniformly across all sites and the species was comparatively uncommon at one site. Overall, our results suggest that old-growth remnants, even within a single state, cannot be viewed as equivalent units with regard to research or management. Stochastic disturbance events and surrounding land use may have amplified effects on small scattered remnants. Therefore, continued monitoring of these rare, but biologically important forests is critical to their long-term management and protection.     

Range reshuffling: Climate change,invasive species,and the case of Nothofagus forests in Aotearoa New Zealand

Aim

The impact of climate change on forest biodiversity and ecosystem services will be partly determined by the relative fortunes of invasive and native forest trees under future conditions. Aotearoa New Zealand has high conservation value native forests and one of the world's worst invasive tree problems. We assess the relative effects of habitat redistribution on native Nothofagus and invasive conifer (Pinaceae) species in New Zealand as a case study on the compounding impacts of climate change and tree invasions.

Location

Aotearoa New Zealand.

Methods

We use species distribution models (SDMs) to predict the current and future distribution of habitat for five native Nothofagus species and 13 invasive conifer species under two 2070 climate scenarios. We calculate habitat loss/gain for all species and examine overlap between the invasive and native species now and in future.

Results

Most species will lose habitat overall. The native species saw large changes in the distribution of habitat with extensive losses in North Island and gains mostly in South Island. Concerningly, we found that most new habitat for Nothofagus was also suitable for at least one invasive species. However, there were refugia for the native species in the wetter parts of the climate space.

Main Conclusion

If the predicted changes in habitat distribution translate to shifts in forest distribution, it would cause widespread ecological disruption. We discuss how acclimation, adaptation and biotic interactions may prevent/delay some changes. But we also highlight that the poor establishment capacity of Nothofagus, and the contrasting ability of the conifers to invade, will present persistent conservation challenges in areas of both new habitat and forest retreat. Pinaceae are problematic invaders globally, and our results highlight that control of invasions and active native forest restoration will likely be key to managing forest biodiversity under future climates.     

The late Quaternary vegetation history of the south‐central highlands of Victoria,Australia. II. Sites below 900 m

The late Quaternary vegetation communities of the south‐central highlands of Victoria are constructed from analyses of pollen and charcoal, and macroscopic plant remains preserved in Sphagnum bogs. The sites, located in eucalypt forest or woodland, form an altitudinal sequence with the component Eucalyptus species varying with altitude and with small pockets of Nothofagus cunninghamii (Hook.) Oerst. in close proximity to the higher sites. The record from the sites above 900 m covers the last 32 000 years, and the record from the lower sites extends from at least 12 000 BP . Around 32 000 BP the region was predominantly covered by a mosaic of alpine feldmark and herbfield, with small patches of Eucalyptus and Nothofagus woodland close to sea level when summer temperatures were probably 5°C lower than present. Lowest values, probably 7°–8°C below present, occurred between 19 800 and 16 900 BP , when alpine communities were most widespread and much of the Central Highlands was treeless. Around 12 000 BP alpine taxa disappeared or were greatly reduced, first at the lower sites. There was an associated rise in the treeline with the movement upslope of Nothofagus and eucalypt forest as a result of a general increase in temperature and probably effective precipitation. By 6000 BP wet eucalypt forest and Nothofagus reached their maximum postglacial extent at all sites, possibly related to a further increase in temperature, at least 2°C lower than present, and higher effective precipitation. A continuing increase in temperature, or an increase in continentality, and a decrease in effective precipitation led to increased fire hazard and retraction of rainforest and wet sclerophyll or tall open forest toward present‐day values. Nothofagus disappeared from the sites below 900 m. The activities of humans pose further threats to remaining forest communities. The record of vegetation and environmental change derived from the local and regional picture from eight sites reinforces and complements that from the individual sites. For example, combining the records overcomes to some extent taphonomic problems such as the effect of streams that flow close to all sites, and other limitations including problems of dating, poor preservation and variable sedimentation rates.     

Spatial pattern of trees in kerangas forest,Sarawak

The 64 most abundant species (10 cm dbh) in a 400×480 m plot of predominantly kerangas forest in Sarawak were individually investigated for two-dimensional pattern by spectral analysis using the basal areas of trees in 20×20 m contiguous quadrats. All species had individuals in the upper canopy.30 species showed pattern with clumps. The most frequent scales of clump size were between 35 and 55 m across. Patterned species were less abundant in the plot, had a greater proportion of smaller (10–20 cm dbh) trees and had a lower ratio of upper to lower canopy trees than species without pattern.Trend across the plot between dipterocarp and kerangas forest types matched the change in soil from red-yellow podzol (oxisol and ultisol) to medium gleyic and bleached sand podzols (spodosol). However, soil differences and small scale (ca. 50 m) changes in topography did not account for patterns.The scale of pattern matches the size of gaps produced by windthrow. It is suggested that patterned species are light-demanding and grow from seeds in gaps, whereas non-patterned species are shade tolerant, growing within closed forest to sapling size and eventually maturing by filling smaller single tree gaps.D. McC. N. thanks the Deutsche Akademische Austauschdienst for a scholarship and the British Council for travel funds to work at Hamburg. We are grateful to A. Weiscke for entry of the 1963 field records on the computer, T. W. Schneider for helpful discussions and T. C. Whitmore for commenting on earlier drafts.Nomenclature for three species follows Whitmore (1972, 1973), Ng (1978) and Ashton (1982).     

Alsodes Australis,A New Species of Leptodactylid Frog from the Temperate Nothofagus Forest of Southern Chile and Argentina

A new species of frog, Alsodes australis, is described from the temperate Nothofagus forest of southern Chile and Argentina, based on adults and tadpoles. Up to now, no sympatric occurrence of another congeneric species is known from the type locality. The genus comprises three species groups. From a karyological point of view this species is included in the monticola group, whose species have 26 chromosomes.