Age,reproduction and biomass allocation in Rhopalostylis sapida(Nikau Palm)

Estimates of age, seed production and the pattern of biomass allocation are presented for New Zealand's only native palm species Rhopalostylis sapida. The age at which palms show above-ground stem development is uncertain, but appears to be in the vicinity of 40–50 years. Palms showing above-ground stems shed two fronds per year, on average. By counting the number of frond scars an approximate age can be determined. Seed production increases continuously with size (and age) for palms which exceed a maturity threshold determined by stem height. Although the percentage of total plant biomass represented by reproductive structures is low, seeds may account for over 50% of nikau palm net production in a year.     

Stemflow nutrient inputs to soil in a successional hardwood forest

Stemflow and throughfall from a regenerating (8-year-old) southern Appalachian hardwood forest were collected to examine the relative importance of tree bole nutrient leaching in response to acid deposition. Samples from nine (2 m²) stemflow collection plots were analyzed for four dormant season and 11 growing season rainstorm events. Results showed that, relative to throughfall fluxes, stemflow accounted, on average, for approximately 8.5% of total water reaching the forest floor during both dormant and growing season storms. Relative to foliar leaching, K-, SO₄-, and PO₄ ions appear to be the most easily leached ions from young tree stems. Proportional nitrate and base cation stemflow fluxes increased significantly (p<0.05) with growing-season storm-event duration, suggesting that the stemsurface nutrient pool is depleted by precipitation more slowly than the foliar pool. On average, proportional stemflow fluxes of SO₄ (12%) and K (14%) were consistently higher than reported maximum values for more mature forest stands, which indicates that small-scale stemflow inputs of ions such as these to the forest floor may be important in early successional ecosystems.     

Stratification in a New Zealand rain forest

An undisturbed podocarp-broadleaved rain forest was sampled in eight strata (synusiae): canopy, small tree, shrub, low shrub, herb, ground, epiphyte and liane. Independent classifications of the quadrats were performed using the eight strata, and the classifications were correlated. Relations between strata were significant, but weak. Using records of plants of all ages, the relations largely reflected the presence of seedlings of woody species in the ground and herb strata. Using only records of species present as adults, the relations were quite different, and at least some seemed to reflect sociological interactions. Relations between a tree and a herb stratum was lower than in McCune & Antos' (1981) investigation, probably because of the narrow ecological range of the present study area.     

Developing a forest biodiversity monitoring approach for New Zealand

There is a lack of comprehensive and consistent information to inform policy makers about the status of New Zealand’s forest biodiversity. Three reasons for collecting such information are: assessing the effectiveness of management, reporting on the status of biodiversity under national and international requirements, and improving our knowledge of ecosystem dynamics for designing effective management systems. The challenge is to design monitoring systems that address these multiple needs simultaneously, and at a range of spatial and temporal scales. This article first considers principles for designing enduring monitoring systems based on past experiences, assessing how effectively these principles were implemented in designing New Zealand’s Carbon Monitoring System (CMS), and finally, suggesting future directions for forest biodiversity monitoring in New Zealand. At a national scale we support an unbiased, systematic sample of forests as implemented in several countries (e.g. Austria and the U.S.A.). We consider it best practice to monitor shifts in the fundamental compositional, structural and functional characteristics of ecosystems and use these to derive indicators. We suggest forest biodiversity indicators should include forest area and spatial arrangement, tree mortality and recruitment, exotic weeds, introduced herbivore impacts, and woody debris. Principles discussed in this paper are relevant to biodiversity monitoring in a wider range of ecosystems than forests. Without spatially extensive, robustly designed, biodiversity monitoring systems, New Zealand will remain in a relatively weak position nationally, and internationally, to report on the effectiveness of biodiversity conservation.     

A vegetation switch as the cause of a forest/mire ecotone in New Zealand

Abstract. Vegetation switches are those processes in which there is positive-feedback between vegetation and environment, i.e. a vegetation state modifies its environment producing conditions more favourable to itself (Wilson & Agnew 1992). Switches can produce and maintain abrupt ecotones between plant communities. Such a sharp ecotone exists between beech-podocarp forest and mire vegetation, both on deep peat, in southwest New Zealand. One such site was examined. There was no apparent explanation for the ecotone in the present topography nor in the substrate. Levelled transects through the forest demonstrated that most seedling establishment occurred on dead fallen tree boles. These microsites were significantly richer in N, P and K than the wet sump microsites. We argue that this is a mechanism whereby trees can become established in the forest, but not in the open mire. In the forest, the presence of trees ensures the presence of dead-log microsites on the ground, permitting tree seedlings to grow. In the mire, there are no such micro-sites, and trees cannot establish. The ecotone may be sharpened because of the presence of an ecotonal band of the small tree Leptospermum sco-parium between forest and mire. This species can reproduce vegetatively by root suckers in the mire. Its boles are light, and even if they fall to the mire surface they are not thick enough to form a substrate for tree-seedling establishment. The larger tree species may be prevented from falling onto the mire by the wind-sheltering of the forest, and by the zone of Leptospermum. The postulated process would represent a new kind of water-/nutrient-mediated switch, of Type 1 (‘One-sided’). It may occur in many waterlogged forests worldwide.     

Changes in phosphorus availability and nutrient status of indigenous forest fragments in Pastoral New Zealand Hill country

Indigenous forest fragments in rural New Zealand are increasingly valued as reservoirs of native biodiversity. Most forest species are adapted to soils of low phosphorus (P) availability, but fragments are often intermingled with managed pastures and subjected to unintended P inputs from aerial topdressing, which may compromise their long-term sustainability. Phosphorus availability and other nutrients in forest fragments were compared with adjacent fertilised pasture and reference forest areas not receiving fertiliser additions. Inorganic (H₂SO₄ soluble) P and available (Olsen) P were approximately ten times greater in fragment forest soils than reference forest soils, while total P was two times greater. The strong linear relationship between total P and cadmium, an element contained in rock phosphate fertilisers, suggested that the increased P levels in fragment forests could be attributed to P from aerial topdressing. Comparison of foliar N:P ratios show that P is being conserved in reference forests but not in fragment forest. A 5-fold increase in P mineralisation rate in forest fragments high in available P and a significant relationship between total P in forests and soil respiration suggests P availability may be limiting microbial activity in these forest systems. Forest Fragments also had base saturation and Ca, Mg, and K levels twice that of reference forests. Increased nutrient levels have been shown to alter plant successional dynamics and community composition, and raise concerns over future successional patterns and long-term stability of these forest fragments.     

Secondary poisoning of mustelids in a New Zealand Nothofagus forest

Eleven radio-tagged stoats ( Mustela erminea ) and one weasel ( M. nivalis ) died of secondary poisoning following Talon 20 P^TM (20 ppm brodifacoum) poisoning operations which killed mice ( Mus musculus ), ship rats ( Rattus rattus ) and probably brushtail possums ( Trichosurus vulpecula ) in a New Zealand beech ( Nothofagus ) forest. This poisoning method could be an especially useful way of restoring New Zealand native bird populations because it kills several predator species in one operation. Potential unwanted side-effects must be researched before its routine use. This research also demonstrates the potential hazards of second-generation anticoagulant rodenticides to conservation of rodent predators in Europe.     

The macroinvertebrate fauna of a New Zealand forest stream

Abstract

The distribution, abundance, and life histories of benthic invertebrates were investigated in a small, Nothofagus forest stream in North Canterbury, South Island, New Zealand. The fauna was dominated by Trichoptera and Plecoptera; Mollusca and fish were absent. Large particle detritivores and scrapers were the predominant functional groups found. Larval Philopotamidae (Trichoptera) were the only abundant filter feeders. Nymphs of the stonefly Spaniocerca zelandica and of mayflies, Deleatidium spp., were the most abundant animals on plant detritus; Deleatidium spp. were abundant on stones also. The distribution of invertebrates in riffles, loose stones, pools, and plunge pools was examined using mesh colonisation trays lifted in September, November, February, and May after respectively 88, 69, 98, and 94 days in situ. Most species were widely distributed, and sample densities of the more abundant insect species showed weak positive correlations with the biomass of detritus present in trays in most months. The turbellarian Neppia montana was overrepresented in trays compared with stream samples, but the relative abundance of most other species appeared to be similar to that on the stream bed. A large amount of silt accumulated in trays during a heavy flood, and was colonised mainly by the oligochaete Eiseniella tetraedra. Information on the life histories of 15 species of Plecoptera, Trichoptera, Ephemeroptera, and Coleoptera was obtained from a 1-year monthly sampling programme, in which 36 taxa were distinguished, and from collections of adult insects made over a 3–4-year period. Most species had poorly synchronised life histories, in that a wide size range was apparent among individuals in most months. Eight species emerged in at least 4 months; S. zelandica and the philopotamid Hydrobiosella stenocerca were taken in 8 and 9 months respectively.     

Vertical gradients in leaf trait diversity in a New Zealand forest

Leaves come in a remarkable diversity of sizes and shapes. However, spatial patterns in leaf trait diversity are rarely investigated and poorly resolved. We used a hierarchical approach to evaluate vertical variability in leaf morphology (i.e., leaf trait diversity) in 16 common tree and shrub species inhabiting a New Zealand forest. Height-related heterogeneity in leaf area, specific leaf area, circularity and length to width ratio was analyzed at three scales: (1) among leaves within plants, (2) among plants within species and (3) among species within functional groups (i.e., trees vs. shrubs). Results were scale dependent. Among-leaf morphological diversity was unrelated to plant height. Among-individual morphological diversity increased with the average height of each species, indicating that taller plant species express a greater range of leaf traits than shorter species. Among-species morphological diversity was higher in shrubs than in trees. We hypothesize that scale-dependent patterns in leaf trait diversity result from scale-dependent adaptations to forest environmental conditions. As trees grow from the forest floor into the canopy, they are exposed to a range of environmental conditions, which may select for a range of leaf traits through ontogeny. Conversely, shrubs never reach the forest canopy and may instead be differentially adapted to suites of environmental conditions associated with different stages of forest recovery from tree-fall disturbances. Overall results indicate that vertical patterns in leaf trait diversity exist. However, their strength and directionality are strongly scale-dependent, suggesting that different processes govern leaf shape diversity at different levels of ecological organization.     

Evidence for extensive but variable nutrient limitation in New Zealand lakes

Nutrient limitation causes reduced growth of organisms, which can translate into far-reaching consequences for populations, communities, and ecosystems. Phosphorus (P) limitation, in particular, is associated with reductions in organismal growth because ribosomes, upon which growth depends, require abundant phosphorus to be produced. Chromosomes are also relatively rich in P, meaning that organisms with relatively high chromosome complements (e.g. polyploids) might be especially dependent on abundant environmental P. Here we address the likelihood of nutrient limitation in multiple populations of Potamopyrgus antipodarum, a New Zealand freshwater snail featuring wide ploidy variation. We found that some form of P limitation is very likely in many, but not all, populations of this snail that we surveyed. We also detected extensive across-population variation in P and nitrogen (N) content and N and P limitation and co-limitation in the algae that P. antipodarum eat. Accordingly, we then experimentally evaluated how P and N alone and together influenced growth rate in P. antipodarum. We found that response to nutrients differed by lineage and that dietary P content was more important than dietary N content as a determinant of growth rate, a trait closely tied to fitness in P. antipodarum. The widespread likelihood of (1) P limitation and (2) variation in dietary P availability across New Zealand lakes, along with (3), evidence for lineage-level variation in sensitivity to P limitation, sets the stage for the possibility that variation in nutrient availability contributes to the distribution and maintenance of ploidy variation in P. antipodarum.     

Litterfall dynamics in a mixed conifer-angiosperm forest in northern New Zealand

Litterfall in a mixed conifer-angiosperm temperate forest in northern New Zealand was traced for 5 years to determine the patterns of litter production and turnover for conifer and angiosperm components of the forest. Basal area and above-ground biomass was shared approximately equally between conifer (mostly Agathis australis; New Zealand kauri) and angiosperm species (plus tree ferns). The five-year mean annual litterfall, excluding macro-litter, was 7.76± 0.39(SEM) t ha^?1 and ranged from 6.77±0.70 t ha^?1 in 1983–4 to 8.79±1.00 t ha^?1 in 1987–8. Mean monthly litterfall showed a strong seasonal pattern with low rates in winter and early spring, increasing to a peak in early autumn. There were major differences in the nature and timing of litterfall between the conifer and angiosperm fractions. Angiosperm leaf litter reached a maximum in early summer, while conifer litterfall showed highest rates for leaves, twigs and cone scales in late summer-autumn. Conifer reproductive structures (strobili and cone scales) contributed from 13 to 21% of total litterfall, a value high relative to other temperate forests. However, conifer leaf turnover was low relative to that for the angiosperms. Size of the microlitter store was 16.16±1.97 t ha^?1 prior to conifer cone fall, and 18.70±2.02 t ha^?1 following it, and conifer litter made up 76–78% of the total litter store. The estimated mean annual decomposition constant, k, was 0.39 overall, 0.33 for conifer leaf litter and 0.71 for angiosperm leaf litter, values which agree well with previously published rates for decomposition in this forest stand. Differences in the costs of biomass production and rates of turnover, as measured by litterfall and decomposition, may help to explain the functional coexistence of conifers and angiosperms in mixed forests.     

Dispersal,feeding and parasitism of adult stoneflies (Plecoptera) at a New Zealand forest stream

The temporal occurrence and dispersal of stoneflies were investigated at a forest stream in the South Island, New Zealand. Although 12 species were taken in Malaise traps, only Spaniocerca zelandica and Cristaperla fimbria (Notonemouridae) were abundant. Adults of S. zelandica were present throughout the year and a wide range of different-sized nymphs, including very small individuals, was also found in all months. In contrast, the emergence period of C. fimbria was limited to about four months in summer and as nymphs are mainly hyporheic, few were taken in Surber samples. Malaise trapping on a 16 m long transect away from the stream and with more distantly located traps in forest and grassland resulted in a very high proportion of males and females of both species being caught within 1 m of the stream edge. Captured females of both species included immature, gravid, and spent individuals. Males and females of both species had almost identical diets dominated by sooty mould fungi, fungal spores, pollen and fine particulate organic matter. High proportions of them were also infected by the encysted larvae of a gordian worm (Nematomorpha) and may be important vectors in its life cycle.     

Mineral cycling in a tropical palm forest

Nutrient cycling and biomass characteristics of a tropical palm forest dominated byOrbignya cohune were found to be different from thsoe of hardwood dominated forests. The cohune palm forest had a high proportion of biomass in leaves (5%), a reduced sapling layer, a large amount of standing forest litter and an exceptionally low decomposition rate factor (0.1 year^–1). Mineral concentrations in palm leaves were generally lower than in hardwood species with the exception of Na, which was exceptionally high inOrbignya cohune. Biomass was estimated at 226 tons ha^–1 containing 1173 kg ha^–1 N; 126 kg ha^–1 P; 437 kg ha^–1 K; 1869 kg ha^–1 Mg; 125 kg ha^–1 Ca, and 2177 kg ha^–1 Na. Soils of cohune association did not differ significantly from those of neighbouring hardwood dominated associations with the exception of Na which occurred in higher concentration because of bioaccumulation in the dominant. The results suggest that the growth habits and physiology of a dominant can strongly influence some of the ecological parameters used to describe aforest association.     

Reducing predation of orb-web spiders by controlling common wasps (Vespula vulgaris) in a New Zealand beech forest

1. Introduced common wasps ( Vespula vulgaris ) reach high densities in the beech forests ( Nothofagus spp.) of the northern South Island, New Zealand, and may be having a severe impact on populations of native invertebrates. An experimental approach was used to test whether reducing the abundance of common wasps increases the probability of native invertebrates surviving. Garden orb-web spiders ( Eriophora pustulosa ) were used because they were easy to collect and could be trained to build webs on a standard frame. Thirty orb-web spiders were placed out on web-frames in each of four study sites in beech forest during periods of low, medium and high wasp abundance, and their rate of removal was measured over a 4-h period. Wasp numbers were reduced by poisoning in two study sites. Using wasp-abundance data from weekly Malaise trap samples in the poisoned and non-poisoned sites, the probability of spider survival over the entire wasp season was modelled and the level of wasp control necessary to protect natural populations of orb-web spiders was estimated.
2. Wasp abundance and the probability of spider survival were negatively correlated, and smaller spiders were likely to survive longer than larger spiders. At the peak of the wasp season, significantly more spiders survived in the poisoned areas than in the non-poisoned areas.
3. The probability of a spider surviving to the end of the wasp season was virtually nil in the non-poisoned sites (5.08 × 10^–18), but was also very unlikely in the poisoned areas (3.47 × 10^–5).
4. The survival model predicts that wasp abundance would need to be reduced by 80–89.5% over the entire wasp season to protect populations of orb-web spiders.
5. Extrapolation from the model predicts that the invertebrate taxa most vulnerable to wasp predation may have already been removed from the beech forest ecosystem during the 40 years of wasp occupation.     

Impacts of introduced common wasps (Vespula vulgaris) on experimentally placed mealworms in a New Zealand beech forest

An introduced social wasp Vespula vulgaris may compete with native birds for honeydew and invertebrates in New Zealand forests. Experimentally hidden mealworms (Tenebrio molitor) persisted longer at two sites following wasp poisoning that at two sites where wasps were not poisoned. Mealworms persisted longer in the morning than in the afternoon within all study sites. An unusually low mealworm removal rate during a morning trial before wasp poisoning heavily influences the results of this experiment but we have no ecological reason to ignore it. Wasps may therefore be having a heavy impact on invertebrate abundance on very short time scales (within a day following dawn emergence). They may also remove cached food items that would otherwise be retrieved by the South Island robin (Petroica australis australis) during cold or dark feeding conditions.     

Pristine New Zealand forest soil is a strong methane sink

Methanotrophic bacteria oxidize methane (CH₄) in forest soils that cover ～30% of Earth's land surface. The first measurements for a pristine Southern Hemisphere forest are reported here. Soil CH₄ oxidation rate averaged 10.5±0.6 kg CH₄ ha^?1 yr^?1, with the greatest rates in dry warm soil (up to 17 kg CH₄ ha^?1 yr^?1). Methanotrophic activity was concentrated beneath the organic horizon at 50–100 mm depth. Water content was the principal regulator of (r²=0.88) from the most common value of field capacity to less than half of this when the soil was driest. Multiple linear regression analysis showed that soil temperature was not very influential. However, inverse co‐variability confounded the separation of soil water and temperature effects in situ. Fick's law explained the role of water content in regulating gas diffusion and substrate supply to the methanotrophs and the importance of pore size distribution and tortuosity. This analysis also showed that the chambers used in the study did not affect the oxidation rate measurements. The soil was always a net sink for atmospheric CH₄ and no net CH₄ (or nitrous oxide, N₂O) emissions were measured over the 17‐month long study. For New Zealand, national‐scale extrapolation of our data suggested the potential to offset 13% of CH₄ emissions from ca. 90 M ruminant animals. Our average was about 6.5 times higher than rates reported for most Northern Hemisphere forest soils. This very high was attributed to the lack of anthropogenic disturbance for at least 3000–5000 years and the low rate of atmospheric nitrogen deposition. Our truly baseline data could represent a valid preagricultural, preindustrial estimate of the soil sink for temperate latitudes.     

Fishery by-product as a nutrient source for bacteria and archaea growth media

A highly soluble fish protein hydrolysates (FPH) with an 80% protein (peptide size between 1.5 and 20 kDa) and a low free amino acid content was obtained from hake (Merluccius hubssi) filleting waste [Lat. Am. Appl. Res. 30 (2000) 241]. Assays with Halobacterium salinarum, Escherichia coli, Bacillus subtilis and Staphylococcus epidermidis were performed in order to test that FPH as nutrient source for archaea and eubacteria culture media. Cell growth was evaluated by plate count, and by monitoring turbidity and nucleic acids content in liquid cultures. Neither cell growth nor generation times resulting from control and FPH cultures exhibited statistically significant differences at alpha: 0.05 suggesting that FPH can be used as an alternative substrate for microorganism cultural purposes.     

Home ranges of ship rats in a small New Zealand forest as revealed by trapping and tracking

Abstract

The home ranges of 5 ship rats (Rattus r. rattus L.) in a small forest area near Palmerston North were determined for 7 months by concurrent cage-trapping and smoked paper tracking. Baited tracking platforms were over 20 times as effective as cage-trapping in obtaining location data, and home ranges revealed by tracking were on average 5 times the area of trap-revealed home ranges. All the rats were to some extent cage-trap shy. However, although cage-traps could not supply useful information on range boundaries or swift acknowledgment of boundary changes, centres of activity calculated from trap data were comparable with those from tracking data. Tracking rates of individuals were variable; it would be risky to assume that they accurately reflected intensity of use of any area over short periods or when rats may have been competing for baits. The rats had stable home ranges; 3 females had ranges predominantly exclusive to each other. The progressive removal of individuals from the study area effected the prompt expansion of adjacent ranges to include vacated areas; that is, range size was inversely related to rat density.     

Biomass and nutrient allocation in a neotropical dioecious palm

Summary The sexes of Chamaedorea ernesti-augusti are largely undifferentiated in the distribution of biomass, nitrogen, phosphorus, potassium, and total non-structural carbohydrates, among leaves and stems. Males bear more inflorescences that are cheaper except in nitrogen, but most females bear greater annual energetic and nutritional burdens due to seed production. The ratio of vegetative to reproductive biomass is 3.5 for males but only 1.2 for females on a per module basis.