The ability to grow xylogenic Pinus radiata D.Don in a liquid medium rather than on a solid one would produce a more homogeneous culture, and this in turn would improve cell and gene studies. We report the development of a liquid culture system for two xylogenic P. radiata cell lines and compare the subsequent formation of tracheary elements induced on the conventional solid media. Findings: The cell viability (fluorescein diacetate staining) in liquid cultures and subsequent tracheary element (TE) differentiation was as high as, or higher than, that observed with conventional callus cultures on solid media. The growth of cells in liquid culture was confirmed by comparing organic carbon consumption and dry weight increase. Conditions for optimal growth were determined by measuring substrate consumption and cell dry weight with two different cell lines, flask volumes, and starting inoculum densities. Changes to flask volume and cell line were observed to modify substrate carbon consumption within the cell culture, whilst having no significant impact on overall cellular yield. Inoculum density and cell line were the most significant factors affecting the percentage of TE produced. Conclusion: Overall, these preliminary findings confirm that P. radiata xylogenic cells were able to be grown in liquid cultures and did produce TE when induced on solid medium. Therefore, liquid culture has the potential to replace the current standard solid medium system for xylogenic culture of P. radiata.

Needle fungi in conifers have been extensively studied to explore their diversity, but environmental factors influencing the composition of fungal communities in Pinus radiata D.Don needles have received little attention. This study was conducted to examine the influence of the environment as defined by rainfall, elevation and temperature on the composition of fungal communities in pine needles at an age prior to that at which spring needle cast (SNC) is generally observed. Elucidating the entire fungal community in the needles is a first step towards understanding the cause of the disease. Methods: Needle samples were collected from 5-year-old P. radiata trees, their age predating the onset of SNC, from 12 plantations in Tasmania. Interpolated data for the climate variables, including seasonal components for rainfall and temperature, were obtained from an enhanced climate data bank. Pooled needle samples were examined for the fungi they contained using DNA sequencing of cloned polymerase chain reaction (PCR) products. Clones were grouped into operational taxonomic units (OTUs) and identified to their lowest possible taxonomic level by comparison with reference isolates and public DNA databases. Results: DNA sequencing revealed that needle fungal communities differed greatly, depending upon the total annual rainfall and needle age. Needle fungi that have been previously associated with pathogenic behaviour, such as Cyclaneusma minus, Dothistroma septosporum, Lophodermium pinastri, Strasseria geniculata and Sydowia polyspora, were all found in the needles in this study. Also, of 70 ascomycetous OTUs that were discriminated by their DNA sequences, 21 were identified as belonging to the Teratosphaeriaceae. Conclusions: An overview of the endophytic fungi present in the needles of P. radiata has been obtained from trees whose age precedes the onset of SNC. All of the previously known pathogenic species for needle cast diseases were present, in addition to a range of unidentified OTUs belonging to the Teratosphaeriaceae.

New Zealand-grown cypresses are typically harvested at 35–40 years of age; however, shorter rotations have been proposed. The objective of this study was to evaluate the feasibility of producing structural products from shorter rotations through examination of wood properties of younger cypress trees. A detailed examination of radial wood property trends was necessary, and the first ring-level models for three cypress taxa were developed because there were no predictive wood property models available. Methods: Radial trends in wood density, microfibril angle (MFA) and modulus of elasticity (MOE) were examined for 55 trees of three taxa (Cupressus lusitanica Mill, C. macrocarpa Gordon and Chamaecyparis nootkatensis (D.Don) Spach x Cupressus macrocarpa). The trees, planted in row-plots, were harvested at age 21 years at which time breast-height increment cores were extracted to determine wood properties. Rings 1 through 18 were examined in detail and used as the basis for developing mixed-effects ring-level models. Results: Taxon, cambial age, ring width and aspect were highly significant as explanatory variables in wood-density models. Trees with a northern aspect (the warmest side with most sunlight) had greater density than those at the south of the plot. Trees with a southern aspect (least sunlight) had significantly lower MOE, which was about 1–2 GPa below the average of 11–13 GPa at age 18 years. Aspect, however, was not significant in models for MFA. Microfibril angle of the cupressus hybrid declined from about 30° at the pith to 13° near the bark, whereas for Cupressus lusitanica, the range was about 36–16° and about 31–16° for Cupressus macrocarpa. Conclusions: The results of this study provide a basis for determining management strategies appropriate to structural timber production from cypress stands. Overall, forecasted ages for production of strength-grade timber were least for the cupressus hybrid. In an application of the models, products of 6 GPa could be obtained from the outer zones of trees of the hybrid from age 22 years and at older ages for the other taxa. Shorter rotations would, therefore, be feasible for the hybrid taxon.

The oomycete Phytophthora kernoviae is known from the United Kingdom and the Republic of Ireland, where it is considered to be a recent invader, from Chile where it was only discovered in 2014, and New Zealand where records date back to 1953. As there is little information in New Zealand linking P. kernoviae with plant disease, it may have been present for much longer and may be indigenous. Seasonal activity of P. kernoviae in a site known to have infested soil was tested by isolation from soil and foliage of existing shrubs and the use of indicator plants. In greenhouse studies, the susceptibility of a range of indigenous plants to P. kernoviae was tested via stem and foliar inoculation. Methods: Soil, litter and understorey vegetation samples were collected for isolation of P. kernoviae at monthly intervals for a year. Plants of Rhododendron catawbiense, which is known to be susceptible to foliar and shoot infection, were placed in the stand as indicator species. In laboratory and greenhouse studies, stem and foliar inoculations of a selection of arborescent plants representing major groups within the New Zealand flora were carried out and compared with three exotic plants of known susceptibility. Results: Phytophthora kernoviae was not isolated from foliage of understorey plants at the study site, but it was recovered from soil and litter from April to November (autumn through spring) inclusive. Little disease developed on the Rhododendron catawbiense indicator plants. All of the exotic, and most of the indigenous, species developed a lesion in response to stem inoculation. Stem lesions were more developed on exotic species than on indigenous hosts. In contrast, few species formed foliar symptoms. Phytophthora kernoviae was recovered from asymptomatic tissue, stems and foliage, of a number of species. Conclusions: Based on the results of the inoculations and the lack of historical records of disease of indigenous plants associated with P. kernoviae, this oomycete does not appear to be a damaging pathogen of New Zealand’s indigenous flora. Although presence in the soil or litter was demonstrated at the study site, little disease developed on the indicator plants suggesting that at least part of the New Zealand population is of low pathogenicity to R. catawbiense.

Density is an important wood property due to its correlation with other wood properties such as stiffness and pulp yield, as well as being central to the accounting of carbon sequestration in forests. It is influenced by site, silviculture, and genetics, and models that predict the variation in wood density within and among trees are required by forest managers so that they can develop strategies to achieve certain wood density targets. The aim of the study presented here was to develop a wood density model for radiata pine (Pinus radiata D. Don) growing in New Zealand. Methods: The model was developed using an extensive historical dataset containing wood density values from increment cores and stem discs that were obtained from almost 10,000 trees at over 300 sites. The model consists of two sub-models: (1) a sub-model for predicting the radial variation in breast-height wood density and (2) a sub-model for predicting the distribution of density vertically within the stem. Results: The radial variation in breast-height wood density was predicted as a function of either ring number or both ring number and ring width, with the latter model better accounting for the effects of stand spacing. Additional model components were also developed in order to convert from annual ring density values to a whole-disc density, predict log density from disc densities, and account for the variation in wood density among individual trees within in a stand. The model can be used to predict the density of discs or logs cut from any position within a tree and can utilise measured outerwood density values to predict the density by log height for a particular stand. It can be used in conjunction with outerwood density to predict wood density distributions by logs for stands of any specified geographic location and management regime and is designed to be able to incorporate genetic adjustments at a later stage. Conclusions: The analysis has confirmed and quantified much of the previous knowledge on the factors that affect the variation in wood density in radiata pine, particularly the influences of site factors and silviculture. It has also quantified the extent and patterns of variation in wood density within and among trees.

A review of the international Montréal Process Criteria and Indicators (MP C&I) sustainable forests reporting framework required member countries to benchmark the Indicators against locally held forest values. Children constitute an important subgroup of the local stakeholders in forests: they may respond to forested environments in different ways and may hold values which are unique to their age group. This study reports on the values school children attributed to their local forests, across three New Zealand regions, and details the agreement of these values to the Montréal Process C&I, a values framework developed by international forestry experts. Methods: Workshops were held with local school children at three locations neighbouring a forested area (Tapawera, Nelson, South Island; Hunua and Kaiata, Auckland, North Island; and Lynmore, Rotorua, Bay of Plenty, North Island). Workshops were conducted using a similar facilitated structure, tailored to the age group of the children. The workshops used both interactive drawings and dialogue exercises to elicit the features of importance and cultural values the students held for their local forests. Following the workshops, these values were mapped to seven broad categories, and analysed for agreement with the MP C&I. Results: Children aged 9–15 years valued forest access and experiences created by visits to their local forest. The children demonstrated an active relationship with their local forest environment, being aware of its landmarks and facilities. Deeper awareness extended across only quite a small geographical area of their forest. They had personal tacit knowledge of the usefulness of the forested environment, as opposed to abstract, generalised ideas, but only indirect allusion was made to legal, institutional and economic topics. Living organisms were by far the most frequently mentioned forest feature. Landscape amenity, also attachment to and identity with their local forest appear to be important to school children. Although the values held by children living close to forests in New Zealand differed across the three regions, they all fell within the purview of the Montréal Process C&I. Conversely, Criteria 5 (Carbon) and 7 (Legal and institutional) were only tenuously held values. Conclusions: School children’s views and understanding of forests in New Zealand offer an insight into the integration of local communities with forests and forestry, forestry activities and forest amenities. Taking children’s values into consideration has broadened our understanding of the comprehensiveness of the Montréal Process C&I. Results from our workshops provided input for New Zealand’s contribution to a revision of the Montréal Process C&I because delegates could cross-reference the proposed alterations to the Indicators against the nationally derived values, which included those of school children.

Logging damage to residual trees during selection cutting may lead to serious economic losses in terms of both timber quality and diameter growth reduction. In this study, we investigated the effect of logging operations on residual tree damage and the consequence of injuries on diameter growth in an uneven-aged mixed forest dominated by beech (Fagus orientalis Lipsky). Methods: The diameter growth of 56 wounded and 56 unwounded beech trees were compared 12 years after selected logging of other trees had taken place in an Iranian Caspian forest. Results: Of total logging wounds, 25.0 % (14 wounds) were caused by felling operations and 75.0 % (42 wounds) were caused by winching operations. The reduction in diameter growth of wounded beech trees was only observed in the breast height DBH range below 55 cm. The diameter growth of wounded trees was 8.1 % lower than in unwounded trees. The vertical distance from the ground of wounding was a significant factor in diameter growth. Wounds that were larger than 200 cm2 in area significantly reduced diameter growth of beech trees. Whether wounds were closed or open wounds had no significant effect on diameter growth but decayed wounds reduced diameter growth by 15.3 %. Conclusions: This study suggested that intensive logging wounds reduce diameter growth, especially in young beech trees. In addition to the intensity, size and position of wounds and tree age, the reduction of diameter growth was related to the ratio of wound size to stem area.

Many studies have been carried out to quantify the wood properties of radiata pine, but few have explicitly looked at quantifying radiata pine bark. Bark is of increasing interest for many reasons, e.g. energy source, potential source of bioproducts, log handling methods and costs, and phytosanitary methods. Methods: Over-bark and under-bark diameter measurements recorded from over 1000 discs taken from fixed heights in 150 trees were used to estimate bark volume percentages. The mature trees were from a single seed source and had been planted at 17 sites throughout New Zealand. Bark volume percentages were converted to bark weight percentages using data from 390 trees from the central North Island of New Zealand. Results and conclusions: This study confirmed earlier research that bark accounts for 12 to 13 % of over-bark volume and 7 to 8 % of over-bark green weight for mature radiata pine boles prior to felling and log handling. It also showed that bark volume percent varied with location in a stem, tree size, and site (mean annual temperature).

Water accounts for around half of the total mass in living trees, and therefore large savings can be achieved if logs are dried before transporting or burning. Methods: An air-drying model for piled logs of Eucalyptus globulus Labill. and Eucalyptus nitens H.Deane & Maiden was developed. Daily moisture content (MC) loss was modelled based on meteorological variables and pile characteristics. The trial had a factorial design with two species, two debarking treatments (with or without bark) and two log lengths (244 and 350 cm). Independent trials started in July 2007 (winter), October 2007 (spring) and January 2008 (summer). There were five replicate piles per season and treatment. Wood pile masses were weighted weekly or twice weekly using a crane, a 10,000 kg balance and chains to hold the piles. Results: The main and interactive effects of seasons and treatments on daily MC loss were highly significant. However, the effect of season (climate) was far greater than the main effects of treatments or the season × treatment interaction. Overall, E. globulus dried 20 % faster than E. nitens, debarked logs dried 8 % faster than barked logs and 244 cm logs dried 3 % faster than 350 cm logs. Daily MC loss for the current day was better explained by a power function of MC at the start of the day, daily air relative humidity, daily air temperature and the number of logs per square metre of pile cross-section (or an equivalent average log diameter). Conclusions: The air-drying model for piled logs can be used to predict drying times (days) to achieve a given target moisture content, providing a new tool for decision-making in forest transport and industrial planning.

Investment in emerging technologies may contribute to a reduction in the suppression costs of wildfires, and is thus worth careful consideration and trialling by researchers and managers. This investigation looked at the potential incorporation of a newly emerging remote sensing technology, remotely piloted aircraft and forward-looking infrared investigated using a cost-benefit analysis approach. Methods: An online survey-based approach targeting subject matter experts in wildland fire management and unmanned aircraft was used to evaluate the percentage change in the effectiveness of five different management scenarios using remotely piloted aircraft and forward-looking infrared. The most commonly accepted economic model in wildland fire management was adapted to determine the net value change between the five scenarios. Results: The benefits of incorporated unmanned aerial vehicles (UAV) or remotely piloted aircraft and forward-looking infrared were measured as the reduction in cost-opportunity of helicopter use, and were estimated as an average of $548 per fire (where the average cost of fires was $1767) or a 31 % cost saving on total suppression costs. The return on investment of such technology was estimated at 24 fires, whereas the return of investment of the existing thermal camera/helicopter use occurred after 160 fires. Conclusions: The incorporation of remotely piloted aircraft and forward-looking infrared if implemented and managed appropriately, could well improve the cost effectiveness of the current forest, rural and wildland fire fighting efforts. The inherent uncertainty on such unevaluated technology (the combination of remotely piloted aircraft and forward-looking infrared) was addressed by adding stochastic variability and a triangular probability distribution approximation. Key management issues and recommendations are identified such as; greater use of current thermal camera equipment where possible, taking a project management based approach for further testing of remotely piloted aircraft and other emerging technologies, and the improved financial recording and reporting of fire management efforts.

Spiral grain angle (SGA) is a wood property that has a strong influence on end-product quality, particularly for solid timber, and most commercial log and timber grading rules restrict the amount of visible surface sloping grain. The aim of this study was to develop parametric models that can be used to predict the intra- and inter-stem variation in SGA in radiata pine (Pinus radiata D.Don) trees growing in New Zealand. Methods: Empirical models were developed using a dataset that contained records from over 1,100 trees that had SGA measured in both the radial direction and at different heights up the stem. Linear and nonlinear model forms were evaluated for their ability to predict the radial variation in SGA. Results: Most values of spiral grain angle were between −5° and +10°, with a few extreme values (up to 20°) observed. A simple linear model based on cambial age was able to account for the radial variation in SGA outside of the innermost growth rings, but only explained 26 % of the overall variation in SGA. Including a relative height term in this linear model increased the proportion of variation in SGA explained to 30 %. A variance components analysis showed that 78 % of the variation in SGA occurred within individual stems, with only 7 % of the variation due to differences between sites. Conclusions: Our results confirmed that SGA decreased from the inner growth rings to the bark and increased with height up the stem, with low values of SGA only found in the lower peripheral part of the stem. Given that the data came from a wide range of sites, the relatively small amount of inter-site variation was unexpected. The models developed here can be incorporated into a growth and yield simulation system to enable forest managers to compare the potential impacts of different factors on the size of the corewood zone in a tree containing wood with high SGA.

Branches support the foliage needed for tree growth, but if the branch diameter is too large it may constitute a defect when the tree is assessed for timber quality and when the tree is processed into boards. Consequently branch diameter is an important consideration when developing a silvicultural regime. The objectives of this study were: (a) to develop site-specific models to predict branch diameter variation with position on the stem; and (b) to use the models to evaluate the influence of initial and post-thinning stand density on branch diameter in unpruned stands of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) at two sites in New Zealand. Methods: Branch diameters were measured using a photogrammetric technique, TreeD, on pre-selected sample trees from unpruned treatments in two silviculture experiments, one in the North Island and one in the South Island of New Zealand. The data were used to develop site-specific models to predict branch diameter along the stem. The models were then used to interpret response to a thinning at a stand age of approximately 10 years when the base of the green crown was still close to ground-level, and to make comparisons with a branch diameter limit of 40 mm. Results: The models developed indicated that previously formed branches were influenced by the increased growing space created by thinning. At all three post-thinning stand densities (250, 500 and 750 stems ha−1), the diameter of some branches on the mean tree within a stand were likely to exceed 40 mm. In unthinned treatments, the model indicated that an initial stand density of at least 1333 stems ha−1 would be needed to keep branch diameters on the mean tree below 40 mm along the whole stem at age 29 years. Conclusions: This study indicates the importance of considering initial stand density, post-thinning stand density and timing of thinning when designing a silviculture regime that aims to control branch diameter.

Forests and wide-spaced trees are used widely in New Zealand to control erosion from shallow landslides. Species that offer similar or better levels of protection to those currently used are sought to meet future needs. Determining what plants to use and when they become effective is important for developing guidelines and policy for land management. This study aimed to obtain data on above- and below-ground plant growth for young exotic tree species considered potential candidates for future ‘erosion control forests’. Methods: The above- and below-ground growth of nine exotic tree species was assessed annually for 3 years from planting in a randomised block field trial. Whole trees were excavated and destructively sampled and several below-ground metrics (total root length of all roots > 1 mm in diameter, lateral root spread, total root biomass) assessed. Results: Differences between species for most metrics at the time of planting carried through to Year 3. The best performing species across most metrics was alder, followed by blackwood, cherry, and cypress. Allometric models relating total root length and below-ground biomass to root collar diameter were established. Conclusion: Top performers with regard to root metrics were alder, cherry, and cypress followed by blackwood, radiata, and redwood. Root information contributes to improving our understanding of how and when, and at what planting density, plants become effective for controlling erosion in New Zealand.

Radiata pine (Pinus radiata D.Don) log exports are a growing and important trade for New Zealand. Oxygen (O2) depletion and carbon dioxide (CO2) accumulation in ship holds caused by log respiration may affect the efficacy of fumigation treatments and safety to people working around the holds. Currently very little is known about changes in respiration rates of harvested logs. This study examined the respiration rate of harvested logs after temperature equalisation overnight to a range of temperatures and when stored at typical indoor or outdoor conditions to identify key factors affecting log respiration rate. Results: The results indicate that the respiration rate of logs increased as a function of temperature following Arrhenius' equation, with activation energy (Ea) value of 27708 J mol−1. The respiration rate at a reference temperature of 20 °C decreased from 25.1 mg CO2 kg DW−1 h−1 one week after harvest to 16.2 and 11.5 mg CO2 kg DW−1 h−1 three and six weeks after harvest, respectively. The dominant respiration tissue shifted from cambial and parenchymatous tissues in ‘fresh’ logs towards the internal sapwood over a six-week period. This shift may be attributed to severe dehydration of the outer layers. Microbial activity also contributed to the respiration of logs when stored at humid conditions. Conclusion: Irrespective of storage conditions, the rates of respiratory CO2 release of log sections remained high during the first two weeks post harvest and declined rapidly within the next a few weeks as logs become dehydrated. Respiration rates at a given storage time increased nearly 50 % for every 10 °C increase in temperature from 10 to 40 °C. Drying logs for 4–6 weeks before fumigation treatment at moderate temperature may help to achieve consistent fumigation results, prevent life-threatening conditions and to reduce transportation cost.

Tissue culture has been viewed as a relatively safe method of transporting conifer germplasm as the risk of pathogens associated with tissue cultured material has been assumed to be low. Despite these assumptions, it is unknown whether tissue cultured propagation material contains microorganisms or whether such microorganisms could grow out onto the media used. Methods: To determine whether asymptomatic tissue culture material contains fungal microorganisms, 30 different Pinus radiata D.Don genotypes from four different types of tissue culture material were analysed for the presence of fungal DNA or mycelium. In addition, thirteen fungal and oomycete isolates were cultured on standard tissue propagation media. Results: Fungal DNA was detected in all samples tested. No fungal or bacterial microorganisms were able to be grown from any of the tissue culture material tested. However, confocal microscopy showed the presence of filaments that could have been fungal mycelium. Growth of thirteen fungal and oomycete isolates on standard tissue propagation media indicated these media can severely limit the growth of some of these microorganisms. Conclusion: The results from this study show that tissue culture material does contain asymptomatic fungal microorganisms but the exact risk from these microorganisms is unclear.

Part of the Coromandel region (North Island, New Zealand) was subjected to a severe storm in March 1995. Analysis of relevant data provides a valuable opportunity to assess the type, extent, distribution and sediment generation rates by slope failures associated with steep-land forests and harvest practice. Methods: Slope failures were mapped at 1:10 000 scale for stands of planted exotic forest, areas of exotic forest cutover, indigenous forest, indigenous secondary regrowth, and pasture. Slope failure dimensions and bulk density were used to calculate catchment-based sediment mass and generation rates by: (i) failure type, (ii) vegetation type, (iii) slope group, (iv) Land Use Capability unit (LUC), and by (v) catchment. The proportion of the total storm sediment load discharged as yield was estimated from records of flow and depth-integrated sediment samples. Results: Storm-initiated slope failures generated ~0.5 Mt of sediment, predominantly by debris avalanche. Most were located within indigenous forest and secondary regrowth and generated ~78% of the total sediment mass. Few slope failures occurred within standing exotic forest and inclusive of areas disturbed by harvesting operations (cutover) generated ~21% of the mass and, 1% was derived from pastoral hill country. Sediment generation rates were greater from areas of exotic forest clearfelled three years before the storm and these were 2.5 times greater than from cutover clearfelled just before the storm. This result is explained by the progressive loss of strength from decaying tree roots that had not yet been countered by an effective root system under a new tree crop. Furthermore, rates were highest for slopes between 26 and 35° and, of the 11 LUC units, were highest for units VIe11 and VIIe2. For the combined Opitonui and Awaroa catchments, ~24% of the storm sediment load was discharged as yield with ~76% remaining as in-channel storage. Conclusions: The erosion response was primarily controlled by rainfall variation and slope, which overrode the influence of vegetation cover. Time since clear-felling had a secondary influence. A re-evaluation of erosion susceptibility in steep-land terrain and a return to the identification, mapping and geomorphic interpretation of site-specific hazards, particularly from an operational perspective—in advance of harvesting—is recommended.

Precision in describing plantation attributes is a key requirement for forestry managers and inventory surveys aim to extract the most precise information possible using the smallest number of plots. This paper quantifies the potential efficiencies to be gained by using Light Detection and Ranging (LiDAR) data as an aid to estimation of standing timber volume in softwood plantations. A range of inventory design and estimation methods were investigated in terms of their overall predictive efficiency. Methods: Field measurements representing four different populations from two Pinus radiata D. Don plantations in New South Wales, Australia, were used to inform statistical models which were then employed to simulate populations of inventory plots. These plots were then “surveyed” using a variety of simulated sampling strategies to quantify the benefits from using LiDAR data as auxiliary information. Model-based and design-based methods were both investigated. Survey design options included stratification and plot selection strategies; estimation options included ratio estimation and regression modelling. Results were compared in terms of the relative bias and root mean squared error of the estimates. Results: The study suggests that relative efficiencies of two-fold or better, are possible with either model-based or model-assisted estimators compared to traditional inventory surveys which use grid samples and simple design-based estimators. This would enable a halving in the required sample size for the same precision for field inventories in these plantations. Conclusion: The use of LiDAR data as an aid to survey design produces marked efficiency gains compared to traditional inventory methods.

Simulation is an established tool for examining the efficacy of forestry sampling designs yet there is little empirical information on the effect that spatial layout of a sample has on stand-level inventory of managed, even-aged stands. This simulation study examines the performance of nine different sampling methods in terms of bias and reliability. Methods: Data sets, derived from five stands of radiata pine, consisted of census lists of every stem, including the location of each stem, breast-height diameter over-bark (DBH), height and derived volume. In four small stands, stems had been geo-located using ground-based methods, whereas the data for a larger stand were derived from an Airborne Laser Scanning data set. Nine sampling methods (random, stand-boundary, quasi-random, Zigzag transects, grid-based plots of four sizes and single-point) were simulated and applied repeatedly to each stand, and the bias and reliability of the estimate of mean stem volume calculated. Results: Sampling the stand boundary produced a biased estimate, averaging a 12% over-estimate for the four stands aged 22 years or more. The other sampling methods generally showed little bias with most estimates within ±0.5% of the population mean, although the Single-point method was considerably less accurate. The Stand-boundary, Grid-plot (>0.02 ha), and Single-point methods produced unreliable confidence intervals. Conclusions: Most sampling methods showed little bias and good reliability when analysed as simple random samples. Sampling plots in the range of 0.02 to 0.04 ha, located systematically on a grid with random orientation and origin, produced some of the most unbiased and reliable estimates. However, the Zigzag method may be appropriate in small stands as it produces little bias, good reliability and is likely to be operationally efficient.

This paper reviewed the key physical, chemical and biological water quality attributes of surface waters in New Zealand’s planted forests. The purpose was to: a) assess the changes in water quality throughout the planted forestry cycle from afforestation through to harvesting; b) compare water quality from planted forests with other land uses in New Zealand; and c) identify knowledge gaps and opportunities for future research. Afforestation of pasture land significantly improved a wide range of water quality attributes such as stream temperature, nutrient and sediment concentrations and microbial contamination within 4-6 years of planting. Water quality in mid-rotation to mature forests, a large proportion of the forestry cycle, was highly variable but characterised by cool water temperatures, low concentrations of sediment and nutrients, with aquatic invertebrate communities indicative of high water quality. Impacts of timber harvesting on water quality attributes were greatest when clear-cut harvesting up to the stream edge. Harvest impacts were mediated by the retention of intact riparian buffers and to a lesser extent by retention of moderate quantities of logging slash across small stream channels. Temporal and spatial factors influenced the magnitude of response to harvesting activities and duration of the recovery period. Land-use comparisons generally showed improving water quality from pasture to planted forest to indigenous forest. Continued research to identify management systems that mitigate impacts on water quality, particularly during harvesting, remains a priority. Consistent approaches to water quality monitoring will improve the ability to report on water quality in planted forests. Future water quality research in New Zealand’s planted forests needs to encompass emerging contaminants of national and international concern such as pesticides and pharmaceuticals. As New Zealand moves toward increasing productivity from planted forests, use of potential interventions such as intensified herbicide and fertiliser use, will need to be within sustainable freshwater limits. A future challenge is to quantify the economic value of freshwater ecosystems services provided by New Zealand’s planted forests. This review showed that with continued prudent stewardship and ongoing improvements in management practices, particularly during harvesting, New Zealand’s planted forests can provide a sustainable source of well-maintained and high quality water resources.

Many of the herbicides used in site preparation of forests and during initial selective weed management can persist in the soil for several months, killing or stunting seedlings of broom (Cytisus scoparius (L.) Link) as they establish. The objective of this research was to determine the relative persistence and effect over time of the herbicides most widely applied within radiata pine (Pinus radiata D.Don) plantations in New Zealand on broom survival and growth. Methods: Eleven herbicide treatments were applied in early summer to a Tokomaru silt loam soil. Soil samples were collected from each treatment at fortnightly intervals for up to a year. The samples were placed into pots and immediately sown with scarified viable broom seeds in a heated glasshouse. Relative growth and biomass of seedlings were determined as the ratio of growth and survival in each treatment relative to growth and survival in an untreated control. Logistic curves were fitted to recorded values of relative growth and survival over time and the time to reach 50 and 95% of the vigour of the plants in the untreated control was determined. Results: The treatments can be approximately ranked in the following order from most to least persistent: triclopyr/picloram > high rate of clopyralid > high rate of hexazinone > terbuthylazine/hexazinone > low rate of hexazinone > low rate of clopyralid > high rate of terbuthylazine > triclopyr > high rate of metsulfuron-methyl > low rate of terbuthylazine > low rate of metsulfuron-methyl. Conclusion: As the rate of triclopyr/picloram used in this work is too phytotoxic to be used selectively over newly planted radiata pines, this treatment would only be suitable prior to tree planting so residual activity would control seedlings that develop after scrub clearance. For post-plant weed management operations, results show hexazinone and high rates of clopyralid to be useful for long-term management of broom as both these herbicides have low phytotoxicity to radiata pine. When combined with low rates of triclopyr and picloram, clopyralid could provide an effective treatment that could be used in combination with oversown or naturally occurring grasses to manage broom.

In order to understand how the seed rain differs among Amazonian forests, I sampled the seed rain in six different forest types across the Amazonian landscape. Methods: I set up seed traps and took seed samples in three unflooded forests (terra firme, white sand-varillal, palm) and three white-water flooded forests (high restinga, low restinga, tahaumpa) in Peru over a period of one year. Results: I found (1) all forest types had dispersed seed of many unique species, with a few species in common, (2) total seed load peaked in the early part of the year – near the end of the rainy season – and then decreased monotonically over the remainder of the year for all forest types, (3) species richness was greater in unflooded forests compared to flooded forests and the largest number of species were found in terra firme, (4) seeds were more evenly distributed among species in the unflooded forests compared to the flooded forests, and (5) Fisher’s α diversity of seeds was greater in high and low restinga compared to tahaumpa. Conclusions: I conclude for the unflooded forests that seed species number and richness increased with soil fertility but for the flooded forests seed species number and richness decreased with months under water. Furthermore, when taken together, results suggest that for forests across the Amazonian landscape differences in flooding regime may have a greater effect on both seed rain load and seed species richness than differences in availability of soil nutrients.

Manipulation of stand density and choice of genetic material are two key mechanisms through which forest managers can influence tree growth and wood properties. Past silvicultural practices in New Zealand have been characterised by early thinning to relatively wide spacing, while tree improvement programmes have primarily focussed on growth and form. The aim of this study was to quantify the impacts of stand density and past genetic selections on the wood properties of radiata pine (Pinus radiata D. Don). Methods: Stress-wave velocity, wood density, microfibril angle (MFA) and modulus of elasticity (MOE) were measured on trees and wood samples taken from a 15-year-old silvicultural and tree breeds trial located in Canterbury, New Zealand. The focus of this study was comparison of seedlots with genetic ratings of GF6 and GF25. Data from pruned stands with final densities of 100, 200 and 400 stems ha−1 were compared as were data from unpruned stands with stand densities of 200, 400, 600 and 1000 stems ha−1. Results: Stress-wave velocity of trees was affected by final stand density, with the lowest values recorded from trees in the 100 and 200 stems ha−1 treatments. Values for wood MFA and MOE both showed the greatest amount of change when final stand density was less than 400 stems ha−1. Trees from the GF25-rated seedlot had wood density that was approximately 34 kg m−3 lower than trees from the GF6-rated seedlot. Conclusion: Very high stand densities are not required in order to influence wood properties, but early thinning to low stand densities should be avoided. Such results are of practical importance to forestry managers.

As the frequency and severity of drought events are expected to increase globally, drought-induced reductions in plantation productivity are likely to become more important. Such reductions will be of concern to forest managers looking to improve forest productivity during the establishment and initial growth phases of plantation-grown Pinus radiata D. Don. The objective of this research was to assess how growth, biomass, leaf area and water-use efficiency in juvenile Pinus radiata responded to the timing and duration of water deficits.Methods: Two-year-old Pinus radiata seedlings (cultivated in a polyhouse) were subjected to various water deficit treatments. Needle water potential, tree growth, biomass partitioning, leaf characteristics and water-use efficiency were measured to assess the impact that the timing and duration of water deficits had on productivity.Results: Cyclical re-watering of the early- and late-season drought treatments led to large fluctuations in needle water potential. The summer drought treatment resulted in a sustained low needle water potential over the summer months. Total water stress integral (Sψ) was 41.4, 66.8, 55.2 and 97.6 MPa-days for the well-watered, early-season cyclical drought, late-season cyclical drought and summer drought treatments, respectively. In general, water deficits decreased tree growth, reduced crown size, reduced biomass accumulation and leaf area, and resulted in more enriched values of δ13C, all of which were significantly (P < 0.05) affected by treatment. Summer drought reduced height, diameter and basal area by 24.7%, 33.1% and 52.3%, respectively. Total biomass was reduced by 64.7% and total leaf area by 40.0%, compared with the well-watered treatment. The reduction in stem diameter growth was larger for the late-season treatment than the early-season treatment when compared with the well-watered trees suggesting that late-season drought is more detrimental than early-season drought to tree growth.Conclusion: The results provide insight for forest managers of Pinus radiata into the importance of managing water deficits in order to maximise forest production of juvenile trees. Results suggest that late-season drought is more detrimental to absolute growth and biomass accumulation than early-season drought.

Wilding conifers are a major threat to large areas of land throughout New Zealand where they compete with native vegetation, modify ecosystems, reduce available grazing land, limit future land-use options and visually change landscapes. Wilding conifers can also enhance damaging fires and in water limited catchments can affect surface flows and aquifer recharge.A range of herbicide treatments was aerially applied by boom to a field trial established within a wilding Pinus contorta (Dougl.) (height range 1.5 – 12 m) infestation. Measurements of mortality taken two years post herbicide application were used to examine variation in efficacy of these herbicides using a mixed-effects model that tested the main and interactive effects of tree height and herbicide treatment on mortality. For a treatment to be considered effective, a mortality rate of over 85% should be achieved.Findings: Herbicide treatment was found to significantly affect mortality. Application of herbicides that included triclopyr (18 kg a.i. ha−1) and dicamba (5 kg a.i. ha−1) applied in combination or these active ingredients applied with picloram (2 kg a.i. ha−1) were found to effectively control P. contorta across the treated height range inducing respective mortality rates of 88 and 89%. Tree mortality rates for these two herbicides were significantly greater than for two treatments with only triclopyr (37%) or triclopyr and picloram (66%) used at the previously stated rates. Neither height nor the interaction of height and treatment affected mortality over the tested range of heights.Conclusions: This research has shown that dense infestations of P. contorta can be successfully controlled using aerial broadcast application of triclopyr-based herbicides applied in a high volume (400 L ha−1) mixture, with extremely large droplets (400 – 500 μm). The Department of Conservation has adopted the most effective formulation for operational use.