Prumnopitys Ferruginea Research Articles

Developing tree ring chronologies from New Zealand matai (Prumnopitys taxifolia (D.Don) Laub.) for archaeological dating: Stable isotope dendrochronology

Aotearoa New Zealand has a rich cultural heritage but dating wooden objects using classic dendrochronology is challenging due to a paucity of master tree-ring width chronologies for species commonly identified in the archaeological record. This paper explores the potential for using a stable isotopic approach to dendrochronology for matai (Prumnopitys taxifolia (D.Don) Laub.). A total of six annual stable oxygen isotope (δ18O) series for matai growing in the Pureora Forest Reserve, were analysed and their oxygen isotopes found to exhibit a level of coherence that enabled cross-dating. A provisional chronology covering the period 1930–2018 CE was developed and tested against a sample of matai from the Kauaeranga Valley (200 km to the north of Pureora) and a sample of miro (Prumnopitys ferruginea (D.Don) Laub.). Miro is another species common in the cultural archive, but also difficult to date using ring-width dendrochronology. Both the Kaueranga matai and Pureora miro samples cross matched against the site chronology at the correct position, but with weaker dating statistics (Student’s t: 4.26 and 4.11 respectively) compared to the results obtained for two (non-2019) sampled Pureora matai analysed in this study (Student's t: 6.80 and 5.66). These results nevertheless demonstrate the presence of a regional-scale dating signal which may be developed for future use as a precision dating tool.

Developing tree-ring chronologies from New Zealand matai (Prumnopitys taxifolia) and miro (Prumnopitys ferruginea) for archaeological dating: Progress and problems

This paper describes attempts to develop tree-ring chronologies from New Zealand matai (Prumnopitys taxifolia) and miro (Prumnopitys ferruginea). These tree species have been recovered from Māori archaeological contexts, including as objects such as canoes and palisade posts. Dendrochronology offers the potential to establish accurate and precise calendar dates for wooden objects but relies on cultural use of species that are also suitable for tree-ring analysis, and the availability of calendar-dated reference chronologies for crossdating wood of unknown age. We used archived cross-section and core samples from seven sites in central North Island, and nineteen core samples collected in 2019 from matai and miro trees at Pureora Forest Park for our analysis. Some of these samples came from long lived trees, with ring counts indicating ages up to 800 years old. We found that both matai and miro exhibit considerable variability in ring clarity and ring width. They also have ring anomalies affecting the reliability of ring-width series. Miro was very challenging, and no tree sequences were built for this species. Tree-ring sequences were built for several matai samples but no secure inter-tree matches were identified. Further analysis of matai samples is required to establish reliable tree ring patterns for inter-tree and inter-site crossmatching.

Species-specific basic stem-wood densities for twelve indigenous forest and shrubland species of known age, New Zealand

Background: Tree carbon estimates for New Zealand indigenous tree and shrub species are largely based on mean basic stem-wood densities derived from a limited number of trees, often of unspecified age and from a limited number of sites throughout New Zealand. Yet stem-wood density values feed directly into New Zealand’s international and national greenhouse gas accounting. We augment existing published basic stem-wood density data with new age-specific values for 12 indigenous forest and shrubland species, including rarely obtained values for trees <6-years old, across 21 widely-distributed sites between latitudes 35° and 46° S, and explore relationships commonly used to estimate carbon stocks. Methods: The volume of 478 whole stem-wood discs collected at breast height (BH) was determined by water displacement, oven dried, and weighed. Regression analyses were used to determine possible relationships between basic stem-wood density, and tree height, root collar diameter (RCD), and diameter at breast height (DBH). Unbalanced ANOVA was used to determine inter-species differences in basic stem-wood density in 5-yearly age groups (i.e. 0–5 years, 6–10 years etc.) (P<0.05). As specific taxa of Kunzea ericoides (Myrtaceae) has only been identified at some study sites we combine the data from each site, and use the term Kunzea spp. We compare our age- and species-specific results with existing published data where age is specified versus non-age-specific values. Results: Kunzea spp. and Leptospermum scoparium exhibited positive correlations between basic stem-wood density and tree height, RCD, and DBH. No relationships were established for Melicytus ramiflorus, Coprosma grandiflora, Weinmannia racemosa ?6-years old, or for Podocarpus totara, Agathis australis, Vitex lucens, and Alectryon excelsus <6-years old. Dacrydium cupressinum and Prumnopitys ferruginea <6-years old exhibited a significant positive relationship with DBH only, while for Dacrycarpus dacrydioides, each correlation was negative. Irrespective of age, basic stem-wood density is not different between the hardwood species L. scoparium and Kunzea spp. but is significantly greater (P=0.001) than that of the remaining, and predominantly softwood species of equivalent age. For Kunzea spp., L. scoparium, Coprosma grandiflora, Weinmannia racemosa, and Melicytus ramiflorus ?6-years old there was no evidence that basic stem-wood density increased with tree age, and values were within the range of published and unpublished data. For naturally reverting stands of Kunzea spp. located between latitudes 35° to 46° S, basic stem-wood density values tended to increase with decreased elevation and increased temperature. Conclusions: Increasing basic wood density values in Kunzea spp. with decreased elevation and increased temperature suggest that where local data are available its use would improve the accuracy of biomass estimates both locally and nationally. Furthermore, refining biomass estimates for existing communities of mixed softwood species, stands of regenerating shrubland, and new plantings of indigenous species will require additional basic stem-wood density values for scaling from stem wood volume to total stand biomass.

Biomass and root attributes of eight of New Zealand\u2019s most common indigenous evergreen conifer and broadleaved forest species during the first 5\xa0years of establishment

BackgroundTree allometric equations are critical tools for determining tree volume, biomass and carbon stocks. However, there is a lack of species-specific biomass equations for juvenile trees of many of New Zealand’s indigenous species. The aim of this study was to provide allometric equations for total above- and below-ground biomass and total root biomass and length for eight common evergreen conifer and broadleaved species.MethodsIn a plot-based field trial, growth metrics of conifers Prumnopitys taxifolia (matai), Agathis australis (kauri), Prumnopitys ferruginea (miro), Podocarpus totara (totara), Dacrycarpus dacrydioides (kahikatea) and Dacrydium cupressinum (rimu) and broadleaved species Alectryon excelsus (titoki) and Vitex lucens (puriri) were measured annually. These species were selected based on their potential role as a long-term solution for mitigating erosion in areas of marginal land proposed for new afforestation/reforestation and as an important carbon (C) sink.ResultsRoot collar diameter (RCD) provided the best fit for tree height, total above-ground biomass (AGB) and total below-ground biomass (BGB), and all regressions were highly significant (P = 0.001). Most species showed significant increases in annual growth and, by year 5, the BGB ranged between 21 and 42% of total biomass and decreased with increasing plant age. Of the conifers, Podocarpus totara had the greatest mean maximum root spread (2.2 m) exceeded only by the broadleaved Vitex lucens (2.5 m). For all species, and in each year of the trial, 100% of the BGB remained confined to within 0.5 m of the ground surface. With the exception of Vitex lucens and Podocarpus totara, > 90% of the total root length remained within a 0.5-m radius of the root bole. The species-specific mean tree biomass of 5-year-old plants ranged from 0.32 to 4.28 kg plant−1. A mixed-species forest established at 1000 stems per hectare (spha), consisting of 200 of each of the best performed of the trialled species, would amass ~ 2.3 t ha−1 of biomass and a forest carbon stock of 3.8 t CO2 ha−1 within 5 years.ConclusionsInter-species differences in the allocation of BGB and AGB appeared to be age dependent. The root-growth metrics of these common indigenous forest species, as candidates for erosion control, have improved our understanding of their potential usefulness for stabilising marginal land. Whole-plant biomass of juvenile trees will greatly improve the accuracy of current estimates of forest carbon stocks for proposed new areas of indigenous afforestation/reforestation.

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.

Size-based fruit selection by a keystone avian frugivore and effects on seed viability

ABSTRACTThe non-random selection of fruits by frugivores can affect plant demography by changing the probability of seedling recruitment. We investigated whether the New Zealand pigeon (Hemiphaga novaeseelandiae) exhibits size-based preference of fruit in two indigenous tree species, Vitex lucens and Prumnopitys ferruginea, that have large fleshy diaspores containing single seeds. We also assessed if there was an advantage for seeds that were actively dispersed since birds may select fruits that have viable seeds (although the cue for such selection remains unclear) and whether a combined scarification–deinhibition advantage was conferred on germination due to seed passage through the gut. Using seed length as a proxy for fruit size, we compared the length of passively dispersed fruits in traps with the estimated fruit length of actively dispersed seeds in six trees of each species across three areas in one fruiting season. For both species, actively dispersed seeds were significantly longer than seeds from passively dispersed fruit, suggesting frugivore preference for larger fruit. Seeds from passively dispersed P. ferruginea fruit had significantly higher viability than actively dispersed seeds and there was no measurable scarification–deinhibition effect. For V. lucens, there was no significant difference in viability between actively and passively dispersed seeds and there was a total lack of seed germination in our trial. Our results show a significant preference by H. novaeseelandiae for larger fruit in both tree species, which was possibly associated with annual fruit production since P. ferruginea trees that had more fruit produced larger fruit on average. That H. novaeseelandiae selected longer fruit in our study is consistent with the prediction that birds will prefer larger fruit when beak gape limitation is absent. However, active dispersal of larger seeds may not always be advantageous since passively dispersed intact fruit germinated equally well and may even have had a viability advantage.

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.

A new species of Hierodoris Meyrick (Lepidoptera: Oecophoridae) with a telescopic ovipositor, from granite sand plains in Fiordland

A new species, Hierodoris extensilis Hoare (Lepidoptera: Oecophoridae), is described from Fiordland, New Zealand. Adults fly by day in February and appear to be restricted to granite sand and gravel fields from 1,150 to 1,500 m above sea level on Mts Titiroa and Burns. The female has an exceptionally long telescopic ovipositor, which suggests that eggs may be laid beneath the surface of the sand in proximity to plant stems or roots. The species is assigned to the H. iophanes Meyrick group of Hoare (2005), and brings the total number of species in this endemic New Zealand genus to 19. New information on the life history of H. iophanes, a miner in cicada-damaged twigs of miro (Prumnopitys ferruginea), is given.

Diversity and distribution of fungal foliar endophytes in New Zealand Podocarpaceae

The diversity and distribution of fungal endophytes in the leaves of four podocarps ( Dacrydium cupressinum, Prumnopitys ferruginea, Dacrycarpus dacrydioides, and Podocarpus totara, all Podocarpaceae) and an angiosperm ( Kunzea ericoides, Myrtaceae) occurring in close stands were studied. The effects of host species, locality, and season on endophyte assemblages were investigated. Host species was the major factor shaping endophyte assemblages. The spatial separation of sites and seasonal differences played significant but lesser roles. The mycobiota of each host species included both generalist and largely host-specialised fungi. The host-specialists were often observed at low frequencies on some of the other hosts. There was no clear evidence for family-level specialisation across the Podocarpaceae. Of the 17 species found at similar frequencies on several of the podocarp species, 15 were found also on Kunzea. Many of the endophytes isolated appear to represent species of fungi not previously recognised from New Zealand.

Coarse woody debris decay rates for seven indigenous tree species in the central North Island of New Zealand

The decomposition rate of stem and branch coarse woody debris (CWD, >10 cm in diameter) was assessed in natural forests located in the central North Island of New Zealand. CWD samples had originated from windfalls associated with cyclone Bernie, and had been decaying for approximately 20 years on the forest floor. Species-specific decay rates were estimated from the density of CWD samples relative to the density of live tree samples from the same stands. Decay rates were determined for rimu ( Dacrydium cupressinum), matai ( Prumnopitys taxifolia), tawa ( Beilschmiedia tawa), miro ( Prumnopitys ferruginea) and kahikatea ( Dacrycarpus dacrydioides) in podocarp forest at Whirinaki, and red ( Nothofagus fusca) and silver beech ( Nothofagus menziesii) in beech forest at Kaimanawa. The average decay rate for these seven species, expressed as the time taken to lose 50% mass ( t 1/2), was 30 years. Larger trees (90 cm diameter at breast height, dbh) decayed more slowly ( t 1/2 = 38 years) than smaller trees (30 cm dbh; t 1/2 = 21 years). After adjustment for dbh, P. taxifolia ( t 1/2 = 39 years), N. fusca ( t 1/2 = 38 years), N. menziesii ( t 1/2 = 31 years) and B. tawa ( t 1/2 = 26 years) decayed significantly more slowly than D. cupressinum ( t 1/2 = 18 years). D. cupressinum decayed more slowly than P. ferruginea ( t 1/2 = 16 years) and D. dacrydioides ( t 1/2 = 14 years), although these differences were not statistically significant because the CWD sample size was small for the latter two species. An attempt to expand the range of species studied using data from in-ground durability tests was not successful as species decay rankings from these tests were inconsistent with natural forest CWD rankings. Stems heavily colonized by the common decay fungus Ganoderma cf. applanatum decayed more rapidly ( t 1/2 = 20 years) than those which were occupied only by other decay fungi ( t 1/2 = 40 years). A tree species and dbh-dependent decay constant, λ, was derived for estimating carbon loss from CWD due to fungal decay and insect activity in indigenous forests. Future research will aim to improve these decay equations by investigating the decomposition processes associated with tree species and basidiomycete populations present at other sites in New Zealand.

Where do conifers regenerate after selective harvest?: A case study from a New Zealand conifer–angiosperm forest

Ensuring the regeneration of selectively harvested canopy tree species remains challenging in mixed forests where species have different requirements for successful recruitment. Mature conifer trees (Podocarpaceae) have been selectively harvested from parts of New Zealand's North Island conifer–angiosperm forests. Forest managers require guidance on podocarp restoration, given current dominance by the shade-tolerant angiosperm Beilschmiedia tawa. We surveyed seedling densities of podocarps and B. tawa ca. 40 years after harvesting and found that B. tawa seedlings outnumbered the combined total of podocarp seedlings by approximately 3:1. There were significant, positive associations between seedlings of most species suggesting that safe sites for establishment were similar, in part, for the suite of study species. These sites are the same as those where adult podocarp trees are reported to occur. We developed and tested candidate models predicting the influence of environmental factors on seedling regeneration; these focused on the roles of soil nutrients, landform, canopy openness, tree fern cover, ground cover by ferns and disturbance. We found the most support for models that used a combination of soil nutrients, canopy composition, landform index and disturbance type to predict seedling occurrence. A positive relationship was found between soil nitrogen (N) and seedling occurrence of all species surveyed, and this relationship alone had most support in explaining the occurrence of Prumnopitys taxifolia and Dacrycarpus dacrydioides seedlings. We found little difference in the current sites of young Prumnopitys ferruginea and B. tawa; both species occur in dense stands of adult B. tawa, although in contrast to B tawa, P. ferruginea seedling occurrence declined with increasing soil phosphorus (P). Dacrydium cupressinum also declined with increasing soil P. Given that the studied forest fits the apparent global trend for angiosperm ascendancy we suggest that manipulations will be required to restore podocarps. Possible interventions are planting seedlings and/or removing some of the B. tawa canopy. Given that podocarp seedlings were found on soils with low soil P, but high soil N concentrations, soil nutrient status should be taken into account during management.

Neighbourhood analyses of tree seed predation by introduced rodents in a New Zealand temperate rainforest

House mice Mus musculus and other introduced rodents represent a novel source of predation on tree seeds in New Zealand forests. In the northern temperate forests where these rodents are native, spatial and temporal variation in tree seed production can result in dramatic fluctuations in the distribution and abundance of seed predators, with subsequent feedbacks on the distribution and abundance of seedlings. We use neighbourhood models to examine variation in rodent predation on seeds of 4 tree species of the temperate rainforests of New Zealand as a function of 1) spatial variation in local canopy composition and 2) spatial and temporal variation in mouse activity. We placed seeds throughout mapped stands of mixed forests in alluvial valley bottoms and on elevated marine terraces in the Waitutu Forest, South Island. The risk of predation on seeds of 2 dominant canopy trees – rimu Dacrydium cupressinum and mountain beech Nothofagus solandri var. cliffortioides– peaked in neighbourhoods dominated by those species and by silver beech N. menziesii, particularly in a year of plentiful seed rain from these species. The risk of predation on rimu and beech seed was also related to measures of local mouse activity. These relationships suggest that the highest local abundance of mice was concentrated in rimu and beech neighbourhoods because of the food provided by seed rain from those trees. Predation on seed of miro Prumnopitys ferruginea, which is eaten by rats but not mice, was low in rimu neighbourhoods and where mouse activity was high. These patterns may reflect spatial segregation in the activity of rats versus mice within stands. Our results suggest that the spatial distribution of canopy trees translates into predictable patterns of variation in mouse activity and seed predation. Heterogeneity in rodent activity and seed predation within stands may have important implications for tree population dynamics.

Plasticity in photosynthetic response to nutrient supply of seedlings from a mixed conifer‐angiosperm forest

Abstract We measured the plasticity of the response of photosynthesis to nutrient supply in seedlings of the dominant four conifer and broadleaved angiosperm tree species from an indigenous forest in South‐westland, New Zealand. We hypothesized that the response of conifers to differing nutrient supply would be less than the response for the angiosperms because of greater adaptation to low fertility conditions. In Prumnopitys ferruginea (D. Don) de Laub. the maximum velocity of electron transport, Jmax, doubled with a 10‐fold increase in concentration of nitrogen supply. In Dacrydium cupressinum Lamb. the maximum velocity of carboxylation, Vcmax, doubled with a 10‐fold increase in phosphorus supply. In contrast, photosynthetic capacity for the angiosperm species Weinmannia racemosa L.f. was affected only by the interaction of nitrogen and phosphorus and photosynthetic capacity of Metrosideros umbellata Cav. was not affected by nutrient supply. The response of the conifers to increasing availability of nutrient suggests greater plasticity in photosynthetic capacity, a characteristic not generally associated with adaptation to soil infertility, thus invalidating our hypothesis. Our data suggest that photosynthetic response to nutrient supply cannot be broadly generalized between the two functional groups.

Corrigendum to: The relative limitation of photosynthesis by mesophyll conductance in co-occurring species in a temperate rainforest dominated by the conifer Dacrydium cupressinum

The capacity to conduct CO2 from the intercellar spaces in leaves to the site of fixation (mesophyll conductance, gm) may pose a significant limitation to photosynthesis. Dacrydium cupressinum Sol. ex Lamb. (rimu), a native conifer of New Zealand, and other members of the Podocarpaceae evolved during the Jurassic when the partial pressure of CO2 exceeded 200 Pa. This species has low rates of photosynthesis and high levels of leaf nitrogen, which have led to the hypothesis that low gm restricts photosynthesis. Mesophyll conductance was estimated from gas-exchange and fluorescence measurements for this and other co-occurring tree species [Prumnopitys ferruginea D.Don (miro), Weinmannia racemosa L.f. (kāmahi), Meterosideros umbellata Cav. (rata)]. Pinus radiata D. Don (radiata pine) and Phaseolus vulgaris L. (bean) were included to provide comparisons with a rapidly growing tree and herbaceous plant with relatively high photosynthetic rates. Mesophyll conductance was not statistically different among indigenous tree species but was lowest for D. cupressinum. This species also had the lowest ratio of mesophyll to stomatal conductance, gm / gst and was the only species where the decline in partial pressure of CO2 was greater from the intercellular air space to the site of fixation (16.3 Pa) than between the bulk air and the intercellular spaces (8.8 Pa), providing support for the hypotheses that low gm limits photosynthesis in this species. As a group, conifers had marginally lower gm and gm / gst ratio than angiosperms, but this difference was strongly influenced by the high values for Phaseolus vulgaris. That co-occurring members of the Podocarpaceae operated differently suggests that low gm may reflect a response to evolutionary pressures other than high atmospheric CO2 partial pressure.

Influence of nitrogen and phosphorus supply on foliage growth and internal recycling of nitrogen in conifer seedlings (Prumnopitys ferruginea).

The dynamics of internal cycling of nitrogen were studied in the southern hemisphere conifer miro [Prumnopitys ferruginea (G. Benn. ex D. Don) de Laub.], which has an indeterminate growth habit. In a 2-year experiment, P. ferruginea seedlings were supplied with nutrient solutions consisting of two different concentrations of nitrogen (5 and 0.5 mM) and phosphorus (1.33 and 0.133 mM) in the first year, and two concentrations (5 and 0.5mM) of a 15N-labelled nitrogen solution in the second year. Growth and nitrogen content of new foliage were shown to be largely dependent on seedling nitrogen status at the end of the first year, and only weakly dependent on nutrient supply in the second. An average of 70% of total nitrogen in new foliage was remobilised from storage in the first 63 d after flushing began. The remainder of new-foliage nitrogen was derived by root uptake from the nutrient supply in the second year. There was some response of nitrogen uptake to high nitrogen supply in the second year where seedlings had been nitrogen deficient at the end of the first year. However, it was concluded that the indeterminate growth habit of P. ferruginea did not distinguish its pattern of nitrogen storage and remobilisation from that of determinate conifers.

The relative limitation of photosynthesis by mesophyll conductance in co-occurring species in a temperate rainforest dominated by the conifer Dacrydium cupressinum.

The capacity to conduct CO2 from the intercellar spaces in leaves to the site of fixation (mesophyll conductance, gm) may pose a significant limitation to photosynthesis. Dacrydium cupressinum Sol. ex Lamb. (rimu), a native conifer of New Zealand, and other members of the Podocarpaceae evolved during the Jurassic when the partial pressure of CO2 exceeded 200 Pa. This species has low rates of photosynthesis and high levels of leaf nitrogen, which have led to the hypothesis that low gm restricts photosynthesis. Mesophyll conductance was estimated from gas-exchange and fluorescence measurements for this and other co-occurring tree species [Prumnopitys ferruginea D.Don (miro), Weinmannia racemosa L.f. (kāmahi), Meterosideros umbellata Cav. (rata)]. Pinus radiata D. Don (radiata pine) and Phaseolus vulgaris L. (bean) were included to provide comparisons with a rapidly growing tree and herbaceous plant with relatively high photosynthetic rates. Mesophyll conductance was not statistically different among indigenous tree species but was lowest for D. cupressinum. This species also had the lowest ratio of mesophyll to stomatal conductance, gm / gst and was the only species where the decline in partial pressure of CO2 was greater from the intercellular air space to the site of fixation (16.3 Pa) than between the bulk air and the intercellular spaces (8.8 Pa), providing support for the hypotheses that low gm limits photosynthesis in this species. As a group, conifers had marginally lower gm and gm / gst ratio than angiosperms, but this difference was strongly influenced by the high values for Phaseolus vulgaris. That co-occurring members of the Podocarpaceae operated differently suggests that low gm may reflect a response to evolutionary pressures other than high atmospheric CO2 partial pressure.

Response of forest tree seedlings to simulated litterfall damage.

Litterfall is an important cause of seedling mortality in many forests ranging from wet tropical to boreal. However, there is a lack of studies that investigate differences between species in seedling resilience to litterfall damage. We selected seedling pairs of seven tree species and simulated litterfall damage by pinning one of each pair to the ground. The mortality and growth rates varied significantly between species for pinned individuals, but were similar for unpinned seedlings. The mortality of pinned Nestegis cunninghamii and Prumnopitys ferruginea was significantly greater than that of unpinned individuals (P < 0.05). However, contrary to expectations, the growth rates of pinned Hedycarya arborea and Nothofagus menziesii were much greater than for those left unpinned (P < 0.05). In general, seedling resilience to the bending damage differed substantially between species. N. cunninghamii and P. ferruginea suffered high mortalities and did not increase growth rates in response to damage, whereas, H. arborea and N. menziesii suffered few mortalities and regained height quickly. Other study species demonstrated intermediate resilience. This study demonstrates that some species are more likely to survive in high-risk litterfall regimes than are others. Given that litterfall risk can vary greatly between microsites, these results suggest that litterfall can contribute to regeneration niche differentiation.

NMR imaging as a tool for noninvasive taxonomy: comparison of female cones of two Podocarpaceae

Summary • Nuclear magnetic resonance (NMR) imaging was investigated as a tool for the detailed morphological comparison of two species of Podocarpaceae of taxonomic interest; these were difficult to investigate by conventional methods. • Two- and three-dimensional NMR images of female cones of Afrocarpus falcatus and Prumnopitys ferruginea were acquired using a range of protocols. Conventional sectioning and microscopic techniques and low-temperature scanning electron microscopy were used where possible, to corroborate the assignments of the NMR images. • A three-dimensional network of resin canals in Prumnopitys ferruginea was revealed and the presence of resin confirmed by chemical shift imaging. Similar canals in cones of Afrocarpus falcatus did not contain resin but the presence of spoke-like vascular traces passing through the sclerotesta was demonstrated. Marked differences in the structure of the sarcotesta of the two species were readily discernible. • NMR imaging allowed noninvasive retrieval of both internal morphological and histochemical information from single specimens in their natural state in a much shorter time than conventional methods would allow and provides useful data for taxonomic purposes in the Podocarpaceae.

Small mammals as potential seed dispersers in New Zealand

AbstractWeed invasion success is strongly influenced by availability of seed dispersal vectors, which may include animals. We examined the potential of several small introduced mammals (mice, kiore, ship rats and possums) to disperse germinable seeds in New Zealand. Captive animals were fed fleshy fruit of weeds (Berberis glaucocarpa, Cotoneaster spp., Crataegus monogyna, Ilex aquifolium, Leycesteria formosa, Ligustrum sinense, Lonicera japonica, Passiflora mollissima, Pyracantha angustifolia, Sorbus hupehensis) and native species (Coprosma spp., Prumnopitys ferruginea and Solanum aviculare). We recorded the percentage of fruit consumed, seed ingested and gut passage time. Faeces were collected and the seeds extracted and tested for germination potential in an unheated glasshouse (two weed species) or under controlled conditions (11 species). The smallest rodents (mice and kiore) generally destroyed all seeds eaten. Large numbers of viable seeds of the small‐seeded (&lt;1 mg) species, L. formosa and S. aviculare, passed through ship rats. Possums consumed the seeds of all adventive and native fruits except P. ferruginea. The proportion of seeds recovered intact from possum faeces varied with plant species and ranged from 6 to 83%. The time required for 50% of all seeds to be passed by possums ranged from 2.5 to 5.5 days with an average of 3.7 days, and was generally unrelated to simple fruit parameters such as percentage pulp and moisture content. For seeds where germination also occurred in the uneaten controls, the germination of seed from possums ranged from 3 to 78%. Germination was mostly lower in seeds from possums than in the controls, where differences were significant. Possums have major potential to disperse a wide range of fleshy fruit‐producing native and introduced plant species. Ship rats have the potential to disperse those with very small seeds.

Post‐dispersal seed predation on eleven large‐seeded species from the New Zealand flora: A preliminary study in secondary forest

Seed predation trials were conducted for 11 large‐seeded species native to New Zealand in secondary forest. The species used were: Alectryon excelsus, Beilschmiedia tawa, Coprosma grandifolia, Corynocarpus laevigatus, Hedycarya arborea, Myoporum laetum, Nestegis cunninghamii, Prumnopitys ferruginea, Prumnopitys taxifolia, Rhopalostylis sapida, and Ripogonum scandens. Seed removal was monitored for 15 days for 160 seeds of each species, placed in piles of 5 seeds in each of 4 treatments at each of 8 sites in the Karori Wildlife Sanctuary, Wellington, in 1998. Removal of depulped seeds from treatments to which all species had access ranged from 3.8% to 23.8%, with a mean of 9.8%. No seeds were removed from the treatment that excluded all vertebrates. Presence of flesh on the seeds significantly increased seed removal rates in the three species tested with and without flesh. No relationship was found between seed removal and seed size, seed mass, or the proportion of the seed mass that was contributed by the seed coat. The seed removal rates reported here are exceptionally low, and suggest that the potential for post‐dispersal seed predation to limit regeneration of native forest in New Zealand may have been overestimated, at least in the forest type studied.