Elaeocarpus Dentatus Research Articles

Canopy structure and understorey light availability in Nothofagus and podocarp-broadleaf stands in a New Zealand forest

ABSTRACT The ability of some ectomycorrhizal fungi to access organic sources of nitrogen is known to influence decomposition, nitrogen mineralisation and soil carbon storage. The consequences for aboveground ecosystem structure and processes are less well-documented. We used the LAI-2200C Plant Canopy Analyzer to compare leaf area index and understorey light availability of ectomycorrhizal Nothofagus stands and arbuscular mycorrhizal podocarp-broadleaf stands growing on similar soils at a dry forest site in the Wairarapa district of New Zealand’s North Island. N. solandri was the sole overstorey tree in the three Nothofagus stands, and the ericaceous shrub Leucopogon fasciculatus was prominent in the understorey. The three podocarp-broadleaf stands were more diverse and more varied, the major contributors to basal area being Elaeocarpus dentatus, Hedycarya arborea, Cyathea dealbata, Carpodetus serratus and Dacrydium cupressinum. Leaf area index of Nothofagus stands averaged one unit lower (4.04) than that of neighbouring podocarp-broadleaf stands (5.11). Average light availability under Nothofagus stands (3.6–4.9%) was twice that beneath podocarp-broadleaf stands (1.6–2.1%). The lower leaf area index, greater light transmittance, and monodominance of Nothofagus stands probably reflects suppression of arbuscular mycorrhizal species by ectomycorrhizal short-circuiting of the nitrogen cycle. This study expands the evidence of positive feedback mechanisms stabilising ectomycorrhizal dominance in some forests.

Introduction of mammalian seed predators and the loss of an endemic flightless bird impair seed dispersal of the New Zealand tree Elaeocarpus dentatus.

Understanding the mutualistic services provided by species is critical when considering both the consequences of their loss or the benefits of their reintroduction. Like many other Pacific islands, New Zealand seed dispersal networks have been changed by both significant losses of large frugivorous birds and the introduction of invasive mammals. These changes are particularly concerning when important dispersers remain unidentified. We tested the impact of frugivore declines and invasive seed predators on seed dispersal for an endemic tree, hinau Elaeocarpus dentatus, by comparing seed dispersal and predation rates on the mainland of New Zealand with offshore sanctuary islands with higher bird and lower mammal numbers. We used cameras and seed traps to measure predation and dispersal from the ground and canopy, respectively. We found that canopy fruit handling rates (an index of dispersal quantity) were poor even on island sanctuaries (only 14% of seeds captured below parent trees on islands had passed through a bird), which suggests that hinau may be adapted for ground‐based dispersal by flightless birds. Ground‐based dispersal of hinau was low on the New Zealand mainland compared to sanctuary islands (4% of seeds dispersed on the mainland vs. 76% dispersed on islands), due to low frugivore numbers. A flightless endemic rail (Gallirallus australis) conducted the majority of ground‐based fruit removal on islands. Despite being threatened, this rail is controversial in restoration projects because of its predatory impacts on native fauna. Our study demonstrates the importance of testing which species perform important mutualistic services, rather than simply relying on logical assumptions.

An avian seed dispersal paradox: New Zealand's extinct megafaunal birds did not disperse large seeds.

Often the mutualistic roles of extinct species are inferred based on plausible assumptions, but sometimes palaeoecological evidence can overturn such inferences. We present an example from New Zealand, where it has been widely assumed that some of the largest-seeded plants were dispersed by the giant extinct herbivorous moa (Dinornithiformes). The presence of large seeds in preserved moa gizzard contents supported this hypothesis, and five slow-germinating plant species (Elaeocarpus dentatus, E. hookerianus, Prumnopitys ferruginea, P. taxifolia, Vitex lucens) with thick seedcoats prompted speculation about whether these plants were adapted for moa dispersal. However, we demonstrate that all these assumptions are incorrect. While large seeds were present in 48% of moa gizzards analysed, analysis of 152 moa coprolites (subfossil faeces) revealed a very fine-grained consistency unparalleled in extant herbivores, with no intact seeds larger than 3.3 mm diameter. Secondly, prolonged experimental mechanical scarification of E. dentatus and P. ferruginea seeds did not reduce time to germination, providing no experimental support for the hypothesis that present-day slow germination results from the loss of scarification in moa guts. Paradoxically, although moa were New Zealand's largest native herbivores, the only seeds to survive moa gut passage intact were those of small-seeded herbs and shrubs.

Post-volcanic forest succession on New Zealand's North Island: an appraisal from long-term plot data

ABSTRACTLong-term (c. 40 years) tree population and soil data from conifer/angiosperm forests that have developed since the last major volcanic eruption (ad 232) in the central North Island of New Zealand were used to test the hypothesis that the shift from conifer to angiosperm dominance away from the eruption centre represents a chronosequence. The proportion of stand basal area comprised by conifers (12% to 98%) was negatively correlated with distance from eruption centre and available soil phosphorus. The tree recruitment rate of angiosperms (1.41%) was significantly higher than that of conifers (0.14%). Conifer tree density and basal area decreased and angiosperm tree density increased in most plots. Tree mortality rates exceeded recruitment rates in all conifers except Prumnopitys ferruginea; tree recruitment rates exceeded mortality rates in the angiosperms Beilschmiedia tawa and Elaeocarpus dentatus but not Weinmannia racemosa. Although net recruitment rates of major canopy tree species agreed broadly with the predicted species succession, there was little evidence of the predicted community succession occurring and that the plots represent a chronosequence. A wider variety of successional trajectories than originally envisaged are operating, and some appear to be truncated at intermediate stages of the postulated sere. Despite ordination of plot composition showing no compositional convergence over time, most successional trajectories are towards increasing dominance by angiosperms. The actual or potential presence of B. tawa appears to be a critical factor in determining future successions on Taupo Tephra.

Testing Broadcast Seeding Methods to Restore Urban Forests in the Presence of Seed Predators

AbstractForest restoration in urban areas often occurs in isolation from remnant forest, limiting the chances for recolonization by native species. Plants with bird‐dispersed seeds can be particularly vulnerable to dispersal limitation and regeneration can be further impeded by non‐native seed predators. We used a factorial experiment to investigate broadcast seeding as a method to reintroduce trees with large seeds and fleshy fruits into early successional forests. We assessed rates of seed and fruit loss, germination and seedling establishment in three seed treatments: (1) caging to exclude introduced mammalian seed predators; (2) removal of fleshy fruit pericarp; and (3) placing seeds in nutritionally enriched clay balls. Across all species (Beilschmiedia tawa, Elaeocarpus dentatus, and Litsea calicaris) seeds and fruits accessible to mammalian predators suffered significantly greater loss (58%) than those protected by cages (4%). However, seed and fruit loss in the presence of predators was reduced to only 35% across all species by the treatment combining the removal of fruit flesh and clay ball application to seeds. Establishment of B. tawa seedlings after 1 year was significantly enhanced by the clay ball treatment (12% of seeds sown vs. 6% without clay balls). Very low establishment rates were recorded for E. dentatus and L. calicaris. Broadcast seeding was found to be a viable method of improving regeneration of large‐seeded late successional trees and may be a cost‐effective alternative to planting saplings. Seedling establishment can be improved with fruit flesh removal and clay ball treatments, especially in the presence of mammalian seed predators.

High-throughput culturing of fungi from plant litter by a dilution-to-extinction technique

High-throughput bacterial cultivation has improved the recovery of slow-growing and previously uncultured bacteria. The most robust high-throughput methods are based on techniques of 'dilution to extinction' or 'extinction culturing'. The low-density partitioning of CFUs in tubes or microwells exploits the fact that the number of culturable species typically increases as inoculum density decreases. Bacterial high-throughput culturing methods were adapted to fungi to generate large numbers of fungal extinction cultures. The efficiency of extinction culturing was assessed by comparing it with particle filtration and automated plate-streaking. Equal volumes of particle suspension from five litter collections of the New Zealand forest tree Elaeocarpus dentatus were compared. Dilute particle suspensions of litter were pipetted into 48-well tissue culture plates containing 1 mL of agar medium per well. Particle volumes from the same samples were applied to continuous agar surfaces in Omnitray plates by automated streaking, and fungal diversity and richness were measured. The spectrum of isolates was assessed by microscopy and sequencing of the ITS or 28S region of the rRNA gene. Estimates of species diversity between the two methods were comparable, but extinction culturing increased species richness. Compared with plating methods using continuous surfaces, extinction culturing distributes fungal propagules over partitioned surfaces. Intercolony interactions are reduced, permitting longer incubation times, and colony initiation and recovery improved. Effort to evaluate and recover colonies from fungal isolation plates was substantially reduced.

Population dynamics of the ship rat Rattus rattus L. in the Orongorongo Valley, New Zealand

The population dynamics of ship rats (Rattus rattus L.) were studied in podocarp/hard‐wood and hard beech (Nothofagus truncata) forest in the Orongorongo Valley, near Wellington, from 1971 to 1998. Rat density (indexed by captures in 116 snap traps over 3 nights per quarter) varied up to five‐fold between consecutive years. Fruiting of hinau (Elaeocarpus dentatus) and hard beech did not drive the fluctuations as had been suggested. Average density increased over the first 15 years of the study (from 2.3 ± 0.3 to 7.5 ± 0.8 per 100 trap‐nights (mean ± SE)), and then declined; this mirrored a trend in cat density driven by external factors. Breeding was largely restricted to spring (November) and summer (February). Breeding rate (proportion pregnant or lactating) was density‐dependent, particularly in older rats. Litter size (based on live embryos and new uterine scars) increased between spring (4.4 ± 0.4) and summer (5.5 ± 0.3) (mean ± SE), but did not vary with density or age. Winter breeding was rare (2% pregnant or lactating in August). Hinau fruitfall did not predict the proportion breeding in autumn (May), or survival in winter‐spring (i.e., population change between August and November). Varying predation intensity was the most likely explanation for the population trend. We review other New Zealand studies and question the assumption that ship rat populations are “eruptive”, except possibly when predation is eliminated.

Phylogenetic Relationships of Cryphonectria and Endothia Species, Based on DNA Sequence Data and Morphology

The fungal genera Endothia and Cryphonectria include some of the most important pathogens of forest trees. Despite available new technology, no comprehensive comparative study based on DNA sequence data and morphology has been done on the available isolates representing these two genera. The main objectives of this study were to assess the phylogenetic relationships among species of Cryphonectria and Endothia, for which cultures are available, and to establish a taxonomic framework based on DNA sequence and morphological data, which will aid future studies and identification of species in these and related genera. Comparisons were based on sequence variation found in the ITS region of the ribosomal RNA operon and two regions of the β-tu-bulin gene. In addition, the morphology of these species was examined. The phylogenetic data indicated that Endothia and Cryphonectria reside in two distinct phylogenetic clades. Cryphonectria parasitica, C. macrospora, C. nitschkei, C. eucalypti and C. radicalis represented the Cryphonectria clade. Endothia gyrosa and E. singularis were included in the Endothia clade. An isolate representing E. viridistroma grouped outside the Endothia clade and separately from other groups. Other clades outside the one encompassing Cryphonectria were those represented by the C. cubensis isolates and fungi isolated from Elaeocarpus dentatus originating from New Zealand. These clades could be distinguished from Endothia and Cryphonectria, based on anamorph morphology, stromatal structure and ascospore septation. Cryphonectria and Endothia, therefore, appear to be paraphyletic and taxonomic relationships for these fungi need to be revised.

Phylogenetic relationships of Cryphonectria and Endothia species, based on DNA sequence data and morphology

The fungal genera Endothia and Cryphonectria include some of the most important pathogens of forest trees. Despite available new technology, no comprehensive comparative study based on DNA sequence data and morphology has been done on the available isolates representing these two genera. The main objectives of this study were to assess the phylogenetic relationships among species of Cryphonectria and Endothia, for which cultures are available, and to establish a taxonomic framework based on DNA sequence and morphological data, which will aid future studies and identification of species in these and related genera. Comparisons were based on sequence variation found in the ITS region of the ribosomal RNA operon and two regions of the β-tu-bulin gene. In addition, the morphology of these species was examined. The phylogenetic data indicated that Endothia and Cryphonectria reside in two distinct phylogenetic clades. Cryphonectria parasitica, C. macrospora, C. nitschkei, C. eucalypti and C. radicalis represented the Cryphonectria clade. Endothia gyrosa and E. singularis were included in the Endothia clade. An isolate representing E. viridistroma grouped outside the Endothia clade and separately from other groups. Other clades outside the one encompassing Cryphonectria were those represented by the C. cubensis isolates and fungi isolated from Elaeocarpus dentatus originating from New Zealand. These clades could be distinguished from Endothia and Cryphonectria, based on anamorph morphology, stromatal structure and ascospore septation. Cryphonectria and Endothia, therefore, appear to be paraphyletic and taxonomic relationships for these fungi need to be revised.

Factors influencing annual variation in breeding by common brushtail possums (Trichosurus vulpecula) in New Zealand

We assembled data on annual variation in breeding rates of brushtail possums from four long-term studies in the lower North Island of New Zealand, three of which spanned more than 20 years. In each study, more than 80% of adult females bred in most years. The major exception was in 1996, when breeding failed synchronously at sites separated by up to 122 km. The overall breeding rate in 1996 at these sites was 28% (n = 201). Other instances of low breeding rate (<70%) occurred asynchronously at particular sites. We analysed variation in breeding rates to determine the contributions to annual variation of individual condition (body weight), population density, food resources and other environmental predictors. The probability of breeding declined rapidly as body condition fell below average. An index of fruitfall of hinau (Elaeocarpus dentatus), a highly nutritious food used by possums, and population density in the previous year were the most important predictors of possum condition and breeding rate. High density in the previous year coupled with low hinau fruitfall in the current year predicted below-average body condition and reduced breeding rate. Although the magnitude of these effects were only significant in ‘extreme’ years, they are consistant with delayed density-dependent effects on fecundity in brushtail possums.

An interglacial macrofossil flora from Schulz Creek, north Westland, New Zealand

On a raised shoreline assumed to be of early Kaihinu Interglacial age (more than 100 kyr ago), in north Westland, well-preserved plant fossils are exposed in sediments in a road-cutting. They were probably deposited in a small freshwater lagoon behind a beach ridge, on a prograded shore. The fossils are robust (wood, coriaceous leaves, tough fruit, or seeds); almost certainly they represent only a proportion of the flora in Schulz Creek catchment at the time. The species composition (including Dacrydium cupressinum, Podocarpus hallii, Prumnopitys ferruginea, small conifers, Nothofagus spp., Metrosideros robusta, Elaeocarpus dentatus) suggests that the climate when the deposit was laid down was probably as mild as it is now. Most of the plant species of the fossil flora occur today in Schulz Creek catchment and the remainder live nearby.

Age Structure and Dynamics of a Podocarp--Broadleaf Forest in Tongariro National Park, New Zealand

Regeneration patterns of three emergent conifers (Dacrydium cupressinum, Prumnopitys ferruginea and P. taxifolia) and three broadleaved canopy species (Elaeocarpus dentatus, Nestegis cunninghamii and Weinmannia racemosa) were inferred from population age structures and spatial patterns in podocarp-broadleaf forest in Tongariro National Park, North Island, New Zealand. Age data were obtained from three clear-felled plots. All three podocarp species had highly discontinuous age-distributions, with different age ranges reflecting differing light requirements and longevities of the three species (...)

Litterfall under hinau,Elaeocarpus dentatus, in lowland podocarp/ mixed hardwood forest, and the impact of brushtail possums,Trichosurus vulpecula

Abstract Litterfall was collected monthly for five years under the endemic hardwood tree Elaeocarpus dentatus (hinau) on two study areas about 3 km apart in podocarp/mixed hardwood forest of the Orongorongo Valley, near Wellington, New Zealand. At high stem densities (42 stems > 8 cm dbh ha-1) total annual hinau litterfall was 504 g m-2, with litter from other associated species contributing a further 119 g m-2. At low stem densities (4 stems > 8 cm dbh ha-1) the values were 293.4 and 163 g m-2, respectively. Except for twigs, the amounts of the various components of litterfall showed marked seasonal and annual variations, and consistent differences between individual trees. At both sites, litter fell throughout the year, with most flowers falling in spring, leaves in summer, and fruits in autumn. The annual cycle of monthly dry weight of leaf-fall, the major component of the litterfall, was highly correlated with the annual cycle of mean monthly temperature, but not with that of rainfall or windrun. Eradication of introduced herbivorous brushtail possums, Trichosurus vulpecula, from one of the study areas was followed by a marked increase the following year in the amounts of hinau flowers and fruits in the litterfall.

Fruits, seeds, and flowers in the diet of brushtail possums,Trichosurus vulpecula, in lowland podocarp/mixed hardwood forest, Orongorongo Valley, New Zealand

Abstract Seasonal and annual variations in fruits, seeds, and flowers eaten by possums in lowland podocarp/mixed hardwood forest, as revealed by faecal analysis, were recorded for 6 years (1978–84). Possums ate fleshy fruits of almost all such species available on the study area. Fruits of Corynocarpus laevigatus, Elaeocarpus dentatus, Knightia excelsa, Macropiper excelsum, Melicytus ramiflorus, Pennantia corymbosa, and Urtica ferox were eaten each year, and those of Carpodetus serratus, Collospermum hastatum, and Passiflora tetranda whenever they were available. Flowers of Knightia excelsa and the introduced gorse, Ulex europaeus, also contributed substantially to their diet. Many other fruits, seeds, and flowers were eaten in small amounts. Consumption of various fruit species was generally dependent on their availability in the forest, but a few species were preferentially browsed or avoided. Fluctuations in timing and intensity of flowering and fruiting were reflected in the amounts and seasonal occur...

Suppression of fruit production of the endemic forest tree,Elaeocarpus dentatus, by introduced marsupial brushtail possums,Trichosurus vulpecula

Abstract Fruit production by the endemic hardwood tree Elaeocarpus dentatus (hinau) was measured during 1981–88 on two study areas about 3 km apart in the Orongorongo Valley, Wellington, using collecting funnels and trays placed under the crowns of the trees. Fruit production differed significantly between study areas, years and individual trees. Buds, flowers, and fruits of hinau were browsed by the introduced marsupial brushtail possum, Trichosurus vulpecula. When possums were eradicated from one of the study areas hinau fruit production increased significantly. As possums recolonised the study area over the next 2–3 years, fruit production declined to former levels. Such effects of possums on fruit production of native trees and shrubs are likely to have serious consequences for native bird populations, and forest dynamics.

Changes in structure and composition over fifteen years in a secondary kauri (Agathis australis)-tanekaha (Phyllocladus trichomanoides) forest stand, Coromandel Peninsula, New Zealand

Abstract Changes in structure and composition were assessed after an interval of 15 years in an old secondary Agathis australis (kauri) — Phyllocladus trichomanoides (tanekaha) stand on Coromandel Peninsula, North Island, New Zealand. Stand structure was intermediate between previously described young and mature A. australis stands. Agathis australis, mostly 100–200 years old, had fastest diameter increment (4.3 mm yr−1 in trees ≥25 cm d.b.h.) and contributed almost all the stand basal area increment; its seedling population contracted and larger trees were developing mature crowns. Phyllocladus trichomanoides, also mostly 100–200 years old, had slower diameter increment (2.2 mm yr−1) and contributed most of the remaining stand basal area increment; its seedling population also contracted. Weinmannia silvicola (towai), probably of similar age, incurred mortality at all sizes while Kunzea ericoides var. ericoides (kanuka), 40–80 years old, incurred most mortality in large saplings and small trees. Stand basal area increased rapidly (0.6 m2ha−1 yr−1) and total density decreased slightly. Spatial patterns of stems over 5cm d.b.h.largely reflected topographic variation, with A. australis, smaller P. trichomanoides and K. ericoides tending to occur on ridges and upper slopes, and Cyathea dealbata (ponga, silver fern), the main understorey plant, and smaller W. silvicola tending to occur on lower slopes. Larger P. trichomanoides and W. silvicola were randomly distributed. Several successional pathways (replacement patterns) are evident, with P. trichomanoides replacing K. ericoides, and A. australis replacing W. silvicola and likely to replace P. trichomanoides in the future. Agathis australis thus appears set to become dominant over most of the stand, largely at the expense of the sizeable suppressed component of its own population, temporarily prominent P. trichomanoides, Knightia excelsa (rewarewa) and W. silvicola, and ephemeral K. ericoides. Canopy diversity is likely to be enriched slightly by a few podocarps (Dacrydium cupressinum (rimu), Podocarpus hallii (thin-barked totara), Prumnopitys ferruginea (miro)) and hardwoods (Elaeocarpus dentatus (hinau), Dysoxylum spectabile (kohekohe)) with moderately shade-tolerant seedlings which have probably been present for at least 100 years.

Wood anatomy of the dicotyledons indigenous to New Zealand 18. Elaeocarpaceae

Abstract The wood anatomy of Elaeocarpus dentatus (J.R. et G. Forst.) Vahl, E. hookerianus Raoul, Aristotelia serrata (J.R. et G. Forst.) W.R.B. Oliver, and A. fruticosa Hook. f. is described. Anatomical differences between Elaeocarpus and Aristotelia, and between species within each genus are discussed.

Denning Habits of Common Brushtail Possums, Trichosurus Vulpecula, in New Zealand Lowland Forest.

Fifty-five T. vulpecula were radio-tracked to 182 den sites on 1987 occasions in the podocarp and mixed hardwood forest of the Orongorongo Valley, near Wellington. Most dens (92%) were above ground in trees, particularly in large trees with many clumps of perching epiphytes; the remainder were under fallen logs or trees or in dense tangles of gorse. Melicytus ramiflorus was the most commonly used living tree species. Others used commonly were Knightia excelsa, Elaeocarpus dentatus, Laurelia novaezealandiae [L. novae-zelandiae] and Podocarpus totara. Use was not dictated solely by availability. Trees without perching epiphytes were hardly ever used. Each possum used 11-15 den trees/yr, most only occasionally; the 3 most commonly used den trees accounted for 60-75% of observations. Males used more dens than females, and the sexes differed in their frequencies of the use of the various tree species, though not in the species used. Possums changed dens frequently, on average 2 nights in 3. Den sharing was uncommon, but many dens, including those on the ground, were used sequentially by several (up to 9) different possums. Dens on the ground were used mostly in autumn and winter, by possums in poor condition or after prolonged heavy rain. The implications of den site choice and use by possums are discussed, particularly in relation to den sites as a limiting resource, and the role of dens in the transmission of bovine tuberculosis. There was about a 50% chance that a den would be occupied by different possums within the probable survival period of deposited tuberculosis bacilli.