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Ecologically and economically harmful wood borers and bark beetles, which have the capacity to expand geographically through the international log trade, require mitigations to prevent their spread. Detailed phenological knowledge of these pests across the wood-product supply chain can support systems approaches to phytosanitary risk management. Forest insect activity from 3.5 years of monthly, fortnightly, and daily sampling in recent clearfells from eight Pinus radiata plantation regions throughout New Zealand is presented. Phenology varied regionally with some species absent from specific regions. Insect activity declined with postharvest duration to a hypothesised background activity level that may be determined by landscape dispersal processes. Maximum temperature was the strongest predictor of flight activity with a 15 °C threshold that increased the probability of flight. Probability of a flight event was calculated for each species at monthly, fortnightly, and daily periods. Although wintertime activity was low, operationally effective temporal periods of low pest prevalence could not be defined on a monthly basis. Assurance of temporal periods of low pest prevalence as part of a systems approach will require additional supporting evidence of the relationship between forecast weather on short temporal scales (days), the probability of flight, and the relationship between low-level flight activity and the risk of wood product infestation by dispersing insects.

Large areas of New Zealand are being aerially sprayed with herbicides to manage ‘wilding’ conifer spread. The purpose of the study was to obtain and analyse droplet spectra produced by nozzles commonly used for wilding conifer spraying to determine whether or not operational recommendations for a target droplet size class (~350 µm) are being met. Droplet spectra were measured in a wind tunnel for 27 nozzle x 3 operating condition (nozzle angle, air speed and pressure) combinations tested for each of three spray mixes. AGDISP, an aerial spray application simulation model, was used to quantify the field performance implications of changes to droplet spectra parameters. Only one nozzle, the CP-09, 0.078, 30°, met the target droplet size specification when used at 45° but not at 0°. However, under these conditions, this nozzle produced a large driftable fraction. All but one of the other scenarios tested produced much larger droplet sizes. Operational spray mixes tended to slightly increase the potential for spray drift compared with the water control. The CP-09, 0.078, 30° nozzle used at 45° met the operational droplet size specification but is more sensitive to changes to nozzle angle (0° versus 45°) than the other nozzles tested. None of the three Accu-FloTM nozzles tested met the target droplet size specification. However, the Accu-FloTM nozzles produced very few fine droplets making them good choices for reducing spray drift potential.

HighlightsSpot spraying is a method for applying pesticides to individual tree crowns.A new method is presented to quantify and analyze the two-dimensional spot spray deposit pattern produced by a UAV.A bivariate normal distribution provided a good fit to the observed deposition data for all treatments.Model parameters effectively described the shape of the ground deposits.Abstract. The purpose of this study was to develop a method for quantifying and analyzing the two-dimensional spray deposit pattern produced from a UAV spot spraying system for applying pesticides to individual plants with crown diameters in the range of 1 to 2 m. An XAG P20 UAV was flown over the center of a sampling grid, and spray deposits from three droplet size treatments, with nominal volume median diameters (VMDs) of 335, 430, and 1150 µm, were measured using horizontal steel plate collectors placed on blocks on the ground. A colorimetric tracer in the spray mix was used to quantify spray deposition. The positioning accuracy of the UAV was excellent, but the droplet sizes produced were much larger than expected. A bivariate normal distribution provided a good fit to the observed deposition data for all treatments. Model parameters effectively described the shape of the ground deposits. Displacement of the deposit distribution center was in a downwind direction. While there were no statistically significant effects of wind speed on the shape or degree of displacement of the center of mass of the observed ground deposit pattern, this was probably a result of the low wind speeds during the study, which were often close to or below the lower sensitivity threshold of the anemometer used. The actual spray coverage on a 2 m tall artificial tree target of 1 or 2 m diameter placed in the center of the plot was consistent across the range of droplet sizes and operating conditions tested. Nevertheless, it is hypothesized that targeting could be further improved if the UAV was slightly offset in an upwind direction and, conceptually, the degree of this displacement would increase as wind speed increased. A sampling grid spacing of 1.0 m would have produced results similar to the 0.5 m spacing actually used. Keywords: Aerial spraying, Pesticides, Spot spraying, Spray deposition, UAV, Unmanned aerial vehicle.

Background Although unmanned aerial vehicles (UAVs) are increasingly used to deliver small-scale aerial pesticide applications, there remains uncertainty over their efficiency in terms of uniformity of spray deposition and their application efficiency. Consequently, a field study was designed to quantify factors influencing the uniformity of spray deposition from a multi-rotor UAV that is operated commercially in New Zealand. Two sampling systems for measuring spray deposition, a continuous horizontal string and steel plates placed on the ground were compared. Results The spray deposit distribution characteristics and calculated lane separation values (distance between flight lines that produces a maximum coefficient of variation of 30% for spray deposits) were strongly influenced by wind speed, nozzle position, release height, ground speed and droplet size. Lane separation values ranged from 1 to > 5 m. Swath distribution parameters (spread and position of peak deposition) derived from plates were not significantly different from those derived from string. However, total deposition on strings relative to plates increased with small droplets. Reducing plate sampling intensity from 0.25 m intervals to 0.5 m and even 1.0 m had only a minor effect on estimates of swath parameter values. Conclusions The potential for precision spraying from UAV platforms has yet to be achieved with improvements required in hardware and software. Further, mechanistic models are needed to quantify how complex interactions among multiple operating and meteorological variables influence spray deposition. © 2019 Society of Chemical Industry.

Spot spraying, in which only the area around individual trees is treated, is an important method of herbicide application during establishment of Pinus radiata D. Don (radiata pine) in New Zealand. Minimising the spot size reduces costs and has possible environmental benefits from reduced overall herbicide use. An analysis of six experiments at five separate sites tested the growth response of P. radiata to spot weed control on sites dominated by herbaceous vegetation, usually as a result of oversowing with a mixture of grasses and legumes. The analysis showed that, on sites dominated by herbaceous weeds, the reduction in rotation length achieved by applying total weed control compared with no postplant weed control ranged from 0.4 to 1.6 years and averaged 0.9 years. A spot diameter of 1 m maintained for 1 year achieved 28% of the benefit of total weed control, whereas a spot diameter of 2 m maintained for 1 year achieved 66% of the benefit. Generally, there was little benefit in maintaining spots beyond 1 year. An economic analysis indicated that weed control of any kind was generally unprofitable when the time-shift gain from weed control was 0.4 years or less but highly profitable for sites with a time shift of 1.6 years or more.

Removing lumen water using supercritical CO2 pressure cycling has been shown to eliminate meniscus-driven collapse during subsequent moisture conditioning of wood. A computational fluid dynamics dewatering model of a simple capillary tube was used to predict and optimise the dewatering of a porous ceramic and softwood. The empirical dewatering results were best described using a modified Chapman-Richards growth curve, with both wood and ceramic behaving in a similar manner. Pressure was found to have the greatest effect on dewatering compared to initial-pressure-hold-time, pressure-release-time or temperature. The fundamental capillary tube model adequately predicted dewatering provided empirical tortuosity and porosity information was incorporated into the diffusion coefficient as a lumped parameter. The findings provide a predictive dewatering model that is applicable to porous materials in general, and provides insight into the removal of water from ceramics and wood at a fundamental level.

Decomposition rates of above-ground coarse woody debris (CWD) (>10 cm diameter) were determined for nine common New Zealand indigenous tree species, and of below-ground CWD for two species. CWD samples were obtained from fallen trees originating from known windfall events which had been decaying for 10–29 years on the forest floor. Species-specific decay rates were estimated from the density (dry mass divided by original volume) of CWD samples relative to the density of samples from live and freshly fallen trees. The estimated half-life (t1/2) or time to lose 50% mass for above-ground CWD across all species was 25.7 years but varied between species and increased with increasing stem diameter. Adjusted to a common diameter at breast height of 60 cm and mean annual temperature of 10 °C, Prumnopitys taxifolia and Fuscospora cliffortioides were the slowest to decay with a t1/2 of about 40 years, Fuscospora fusca, Weinmannia racemosa, Beilschmiedia tawa, Lophozonia menziesii and Prumnopitys ferruginea the next slowest with a t1/2 of 27–34 years, while the remaining species (Dacrydium cupressinum and Dacrycarpus dacrydioides) decaying more rapidly with a t1/2 of less than 20 years. A model was derived for predicting the exponential decay constant for the above-ground CWD of individual stems as a function of diameter at breast height and mean annual temperature adjusted for species. This model can be used to predict above-ground CWD carbon stock changes in New Zealand’s natural forests following tree mortality. Below-ground CWD decay rates did not differ significantly from those of above-ground CWD for D. cupressinum, but were significantly faster for L. menziesii.

Natural forest comprises approximately 78% of New Zealand’s total forest area and their dead wood carbon pools contribute to the national carbon balance reported under the United Nations Framework Convention on Climate Change. We investigate the accuracy of coarse woody debris (CWD) carbon stock estimates obtained from periodic inventories of New Zealand’s natural forest. Dimensions and decay classes of standing-dead spars, fallen logs and stumps over 10 cm diameter were assessed in permanent plots during two inventory cycles (2002–07 and 2009–14). Carbon in CWD was estimated by multiplying CWD volume with species-specific mean wood and bark density, a density modifier based on decay class, and the carbon fraction. The measured change in CWD between inventories was obtained by subtracting 2002–07 from 2009–14 mean CWD carbon stocks. This measured change in CWD carbon stocks was compared with the modelled change derived by applying a decay model to 2002–07 stocks to determine the losses from decay and adding inputs from the tree mortality recorded between the two measurement cycles. Estimates of CWD carbon stocks from field measurements were 19.9 and 19.5 tC ha−1 in 2002–07 and 2009–14 respectively, with a statistically non-significant change of −0.4 ± 0.6 tC ha−1 (95% C.I.) over the period between measurements implying that CWD carbon is in a steady state. However, the modelling approach gave a significant increase of 2.5 ± 0.7 tC ha−1, implying that CWD stocks are increasing. It appears likely that the primary reason for the discrepancy between the direct measurement and modelling approaches is that CWD carbon stocks are substantially underestimated using current measurement protocols used in the inventory of New Zealand’s natural forest. If CWD carbon stocks in New Zealand’s natural forests are approximately in balance as implied by the direct measurement of CWD stocks, CWD inputs from mortality would have to be balanced by losses from decay. For this to be true, the CWD pool would have to approximate 35.4 tC ha−1 which is 78% higher than its measured value.

HighlightsThe swath pattern was measured from an Agras MG-1 UAV spraying fine and extra-coarse droplet spectra.The recommended lane separation of 3.6 m did not differ for the two droplet size classes tested in this study.The applied spray deposited within the swath was higher with extra-coarse (>90%) than with fine (73%) droplets.There was potential for substantial downwind drift with fine droplets, even when flying close to the ground at low speed.Abstract. While there is increasing interest in the use of small, multi-rotor UAVs for application of agrichemicals, there is also uncertainty about their performance. Consequently, the purpose of this study was to quantify the performance of an Agras MG-1 with modified nozzle positions that, at the time of writing, was being used for commercial spraying in New Zealand. The approach was to release spray from the UAV along a single 50 m line. Spray deposits were measured using horizontal collectors placed on the ground in three 15 m transects centered on, and perpendicular to, the flight line. Airborne deposits were measured with a 10 m mast that supported spherical samplers at 1 m vertical intervals. Analysis of deposition data was undertaken to quantify factors influencing overall swath pattern variability, lane separation associated with a coefficient of variation (CV) of deposition of 30%, and spray application efficiency, which is the proportion of applied spray deposited within the swath. For two droplet size classes (extra-coarse and fine), the lane separation associated with a CV of 30% was about 3.6 m, with no significant effect of droplet size. This is a surprising result and may reflect the relatively small range of environmental conditions experienced during the field tests, including wind speed, which was relatively low for all tests. We speculate that this result may also be a consequence of the strong downwash. The swath width was positively correlated with wind speed. Spray efficiency was shown to be high (>90%) for the extra-coarse droplets but dropped significantly (73%) with the fine droplet spectrum. Combining in-swath deposition with the amount of airborne spray sampled in a 10 m vertical profile close to the edge of the swath accounted for 98.0% of the spray released with the extra-coarse spectrum but only 88.6% of the spray with the fine droplet spectrum. These results highlight that even with UAVs flying relatively close to the ground at a low forward speed, there is potential for substantial drift downwind of the swath when using smaller droplet size classes. Overall, the swath pattern was reasonably consistent across the two droplet size classes and for the narrow range of operational and meteorological conditions tested. Keywords: Aerial spraying, Pesticides, Spray application efficiency, Spray deposition, Swath pattern, UAV, Unmanned aerial vehicle.

Coast redwood (Sequoia sempervirens) is a productive conifer that has considerable potential as a plantation species within New Zealand where radiata pine (Pinus radiata) comprises 90% of plantations. However, little research has compared volume productivity on the same basis between radiata pine and promising species such as redwood. Radiata pine volume productivity can be described by 300 Index, which quantifies its mean annual increment at age 30 for a stand density of 300 stems ha−1. Using New Zealand redwood growth data from 130 plots, the objectives of this study were to (i) develop a model of redwood 300 Index productivity, (ii) compare fine scale (25 m) spatial predictions of 300 Index from this model with previous national predictions of 300 Index for radiata pine and (iii) undertake species comparisons of volume productivity across a broader age range for contrasting stand densities and values of 300 Index. Measurements made within the plot dataset demonstrated the high productivity of New Zealand grown redwood with maximum mean top height and volume reaching, respectively, 59.1 m and 4,293 m3 ha−1 for an 84 year old stand. Redwood 300 Index ranged 15-fold within the dataset from 4.36 – 64.8 m3 ha−1 yr−1 (mean = 22.8 m3 ha−1 yr−1; SD = 11.7 m3 ha−1 yr−1). The multiple regression model that was developed to predict 300 Index from environmental and stand variables fitted the data well (R2 = 0.66, RMSD = 6.80 m3 ha−1 yr−1). The 300 Index surfaces show that redwood volume productivity was on average 8% higher than radiata pine within the North Island, but on average 33% lower than radiata pine in the South Island. Species comparisons of volume over time, for three contrasting site qualities (300 Indices), showed that redwood markedly outperformed radiata pine, at ages older than 30 years for final crop stand densities of 300 stems ha−1 and this species divergence in volume increased at 600 stems ha−1. The developed surfaces highlight the potential of redwood for further afforestation within New Zealand.

Final crop stand density is an important determinant of plantation value. A relatively simple model, based on productivity indices, has recently been developed that can spatially optimise final crop stand density S opt , of the widely planted plantation species Pinus radiata D. Don for stands grown for structural grade timber. When applied to New Zealand this model shows S opt to be ca . 100 stems ha −1 higher than the current final stand densities. Using a comprehensive set of model simulations, the objectives of this research were to (i) examine the accuracy of predictions of S opt from the simple model and (ii) determine the potential economic gain of thinning structural grade regimes to optimal stand densities. Simulations included 15 combinations of the metrics Site Index and 300 Index that cover the productivity envelope occupied by New Zealand plantations and assumed a rotation age of 28 years. For each combination of Site Index and 300 Index, simulations included S opt and eight stand densities that were 200, 150, 100 and 50 stems ha −1 lower and higher than S opt . Composite financial metrics, weighted by the proportion of the plantation estate in each productivity class, showed marked increases from stand densities 200 stems ha −1 lower than S opt to S opt which levelled off above S opt . This levelling off after S opt suggests that the simple model provides an accurate estimate of S opt . Gains in gross value, net value, internal rate of return and net present value that could be realised through increasing stand density by 100 stems ha −1 were, respectively, $5183 ha −1 ($77,891–$83,074 ha −1 ), $2319 ha −1 ($28,740–$31,059 ha −1 ), 0.44% (8.05–8.49%) and $294 ha −1 ($108–$402 ha −1 ). When scaled up to the plantation estate potential gains in net and gross value that could be realised through thinning to S opt were respectively, $1.7 and $3.8B, which when discounted back to the current time equate to respective gains of $156 and $349 M.

The productivity of planted forests depends upon the maintenance of soil fertility and an understanding of the relationships between site fertility and stand productivity. The effects of harvest residue and forest floor management, and fertiliser additions on ecosystem biomass, carbon and nutrient accumulation were evaluated 5 years after establishment of Pinus radiata stands growing on four contrasting soil types at Woodhill, Tarawera, Kinleith, and Golden Downs forest in New Zealand. The harvest residue removal treatments were stem only harvest, whole tree harvest, and whole tree harvest combined with forest floor removal, all with and without mostly urea-nitrogen fertiliser additions (cumulative range across the four sites 400–1150 kg N ha−1). Woodhill forest biomass and nutrient stock results at age 5 years have been previously reported and were added to with new carbon and nitrogen analysis. The results showed for all sites except on recent sands at Woodhill, where soil nutrients were very low, that harvest residue and forest floor removal had limited impact on 5 year old P. radiata productivity, above ground live biomass and nutrient accumulation, and mineral soil nutrient concentrations. Across all sites the whole tree harvest combined with forest floor removal negatively impacted the 5 year old forest floor biomass and nutrient stocks, with variable impact due to whole tree only removal. The addition of large experimental amounts of mineral nitrogen fertiliser increased tree productivity across sites, which was reflected in tree biomass for all sites except Tarawera. Based on these relatively short-term findings, when P. radiata forests in New Zealand are experiencing a peak nutrient demand (highest nutrient demand amount per year), there were limited negative impacts of harvest residue and forest floor removal on forest productivity, tree biomass and nutrient accumulation, and mineral soil nutrient concentrations. The exception was for a sand dune derived soil that had very low soil nutrients resulting in a greater proportion of the forest ecosystem nutrient pool to be held within the tree and forest floor biomass, emphasising the importance of harvest residue and forest floor retention at low nutrient sites.

Tree nutrient concentrations, root biomass, soil nitrogen (N) and phosphorus (P) contents, and enzyme activities were determined in a radiata pine plantation (Pinus radiata D. Don) on a sandy loam soil receiving 19 years of repeated biosolids applications, and the composition of soil microbial groups was assessed using phospholipid fatty acid analysis. Biosolids application significantly increased soil organic N, available P and foliar N concentration, but had no significant impact on foliar P concentration over the long term. Biosolids application improved aboveground tree growth but reduced fine-root biomass. Repeated biosolids applications also altered the composition of soil microbial community and increased the potential activities of N-acetyl-β-glucosaminidase and acid phosphomonoesterase. Changes in soil N and P availability were better explained by variations in the composition of bacterial groups than those of fungal groups. The fungi-to-bacteria ratios were not changed, but arbuscular mycorrhizal fungi were suppressed possibly due to elevated soil P caused by biosolids application. The ratios of Gram-positive to Gram-negative bacteria were significantly increased by biosolids application and were linked to increased N mineralisation rates. In addition, it is evident that variations in soil P availability and the composition of soil microbial groups following biosolids application were not significantly related to foliar P status. These findings contribute to a better understanding of the effects of biosolids application on microbial-mediated soil N and P processes.

Surfaces that describe spatial variation in optimal stand density following final thining (Sopt) are likely to be of considerable use to forest managers. Using a comprehensive series of growth model simulations, the aim of this research was to (i) develop a model of Sopt that maximises volume of large-diameter, small-branched sawlogs (S27) for unpruned New Zealand radiata pine (Pinus radiata D. Don) stands, (ii) use this model to examine how site productivity and tree morphology influence Sopt, and (iii) generate a map of Sopt for New Zealand. A model predicting Sopt from clearfell age and two productivity indices, Site Index (SI) and 300 Index (I300), was found to predict optimal stand density with a high degree of accuracy. Optimal stand density was found to increase with I300 and clearfell age but decrease with SI. Within New Zealand plantations, the mean predicted Sopt for clearfell age 28 years was 614 stems·ha−1. The proportion of plantations predicted to have Sopt greater than 400, 500, and 600 stems·ha−1 was 0.99, 0.88, and 0.61, respectively. The predicted Sopt was found to exceed the actual mean final crop stand density in stands managed under unpruned sawlog regimes of ca. 500 stems·ha−1 within most plantation areas in New Zealand. This disparity highlights the potential of this approach for increasing crop value in New Zealand P. radiata plantations.

Summary Predicting how increasing rates of global trade will result in new establishments of potentially damaging invasive species is a question of critical importance to the development of national and international policies aimed at minimizing future invasions. Centuries of historical movement and establishment of invading species may have depleted the supply of species available for future invasions, and it has been suggested that the problem of invasions will diminish as a result of this. However, the extent to which source pool depletion affects future invasions remains unclear. Here we describe a mechanistic model that captures the simultaneous effects of depletion of source species pools along with increases in pathway rates (e.g. imports) to predict future numbers of new invasions. We assume that the distribution of species abundance within invasion pathways is positively skewed, which is modelled using a log-normal distribution. Given their high propagule pressure, the most abundant species are likely to invade first, while the many rare species are likely to invade only under high pathway volumes. We apply this model to the case study of bark beetle, Scolytinae, invasions in the USA. Source species pools in Europe and Asia (225 and 655 species of Scolytinae, respectively) are much larger than numbers that have historically established (16 and 32). Parameterization of the model indicates a highly skewed species abundance distribution in the pathway and this is confirmed by species frequencies in port inspection records, thus explaining why only a small fraction of species has historically invaded. Forecasts from the model indicate that with increasing rates of imports, more species from these regions are likely to invade in the future despite the depletion of the most abundant species from source species pools. Previous statistical models tend to underestimate future establishments in the presence of increasing import rates due to their failure to account for key underlying mechanisms. Policy implications. The mechanistic model developed here is widely applicable for predicting future invasions of all taxa and provides insights into how increases in rates of imports counteract the species pool depletion effect, resulting in the continued establishment of new species.

An experiment was undertaken to test the hypothesis that AGDISP, a mechanistic model that simulates the landing position of droplets aerially released for pesticide application, overestimates downwind airborne spray concentrations by not accounting for the turbulence generated within the canopy sublayer. AGDISP is used by pesticide regulators in many parts of the world to quantify exposure from aerial pesticide spraying as part of an assessment of risks to public health and the environment. Using a novel design, airborne spray drift was measured in a 3.2 m high radiata pine plantation, 65 m downwind from the aerial spray flight line, using a small circular sampling array. The spray sampling array consisted of a central 10 m high mast plus a set of 16 secondary masts distributed evenly around a circle with a radius of 5 m from the central mast. All spray applications were made with a Bell Jet Ranger using a spray mix of water plus a fluorescent tracer and a droplet spectrum with a volume median diameter of 101 µm. A single treatment comprised six passes along the flight line, and there were 28 replications. Airborne spray was sampled with both rotorods and artificial foliage placed at four heights on the central mast, ranging from approximately half canopy height to 3 times canopy height. The secondary towers sampled airborne spray using the same collectors placed at just above canopy height and at half canopy height. Other measurements included leaf area distribution, prevailing meteorological conditions, and turbulence using sonic anemometers. Backscatter LiDAR was used in an attempt to quantify the height and density of the spray cloud in the vicinity of the central mast. Rotorod and artificial foliage deposition values were highly correlated, giving confidence in the sampling approach. Neither wind speed nor release height had a significant effect on airborne spray flux in the 0 to 10 m zone, but results were complicated by a spurious negative correlation between wind speed and spray release height. The lack of dependence of deposition on wind speed in this experiment is surprising but is explained both by the variance in the data as well as the physics of small droplet movement in the atmosphere. At the individual sample level, measurements of airborne spray using either rotorods or artificial foliage were poorly correlated with AGDISP predictions. However, when data were averaged across replications, there was a very strong correlation between measurements and AGDISP data, even though in absolute terms, and as hypothesized, AGDISP significantly overpredicted the quantity of airborne spray. As indicated from a comparison with measured deposition, the backscatter LiDAR appeared effective in describing the spray cloud profile, and it suggested a total spray cloud profile that was more complex than the AGDISP model prediction. Keywords: Aerial application, AGDISP, Canopy deposition, Pesticides, Spray drift.

Background New Zealand’s planted forest area is dominated by radiata pine (90%), but also includes Douglas-fir (6%), and a range of minor species including eucalypts and cypress. Carbon sequestration in planted forest is currently estimated using yield tables from the Forest Carbon Predictor (FCP), which was designed to estimate dry matter in live biomass and dead organic matter pools in radiata pine stands. Stand variables required as model inputs include basal area, mean top height, stocking, and tending regime. In addition, wood density needs to be measured or estimated. When the FCP is applied to plantation species other than radiata pine, dry matter estimates may need to be adjusted to remove bias. Methods To test for and remove bias, existing biomass studies were compiled and additional biomass data collected to fill gaps. Measured dry matter stock estimates were compared with predictions from the FCP model. Species assessed included Pseudotsuga menziesii (10 stands), Cupressus lusitanica (2), Eucalyptus regnans (7), E. nitens (5), E. saligna (7), E. botryoides (2), E. fastigata (2), and Acacia dealbata (2). Results Stem bark and crown components were higher in Douglas-fir than predicted by the FCP, whereas crown components were appreciably lower in hardwood species than predicted. Root biomass estimates in Douglas-fir and hardwood species were similar to predictions from the FCP. Dead organic matter stock estimates were similar in Douglas-fir to predictions from the FCP. Dry matter predictions from the model were adjusted by species or species group, to help reduce model prediction error when the FCP is applied to these species. Model bias for Douglas-fir averaged 4.1% for aboveground live biomass, with a root mean square error of 12.9%. Model bias for hardwood species averaged − 0.11% for aboveground live biomass, with a root mean square error of 16.1%. Owing to data limitations, model bias was poorly estimated for dead organic matter pools. Conclusions This study has shown that forest carbon models that have been developed for well-studied plantation species can be adapted with some degree of certainty and applied to other species with suitable, albeit limited, biomass data in order to improve the accuracy of predictions of stand biomass and carbon sequestration.

The purpose of this study was to better understand how both the content and flux of soil carbon respond to forest succession and anthropogenic management practices in forests in subtropical China. We assembled from the literature information on soil organic carbon (SOC) and soil respiration (Rs) covering the forest successional chronosequence from pioneer masson pine (Pinus massoniana) forest (MPF) to medium broadleaf and needleleaf mixed forest (BNMF) and the climax evergreen broadleaf forest (EBF), along with the two major forest plantation types found in subtropical China, Chinese fir (Cunninghamia lanceolata) forest (CFF) and Moso bamboo (Phyllostachys pubescens) forest (MBF). Both SOC and Rs increased along the forest successional gradient with the climax EBF having both the highest SOC content of 33.1 ± 4.9 g C kg−1(mean ± standard error) and the highest Rs rate of 46.8 ± 3.0 t CO2 ha−1 year−1. It can be inferred that when EBF is converted to any of the other forest types, especially to MPF or CFF, both SOC content and Rs are likely to decline. Stand age did not significantly impact the SOC content or Rs rate in either types of plantation. Forest succession generally increases SOC content and Rs, and the conversion of natural forests to plantations decreases SOC content and Rs in subtropical China.

Realised genetic gain for radiata pine (Pinus radiata D. Don) was estimated using data from 46 installations of three series of block-plot trials spanning a wide range of site types throughout New Zealand. These trials contained 63 unique seedlots with different levels of genetic improvement. Realised genetic gain was quantified using two measures of productivity: site index and 300 Index (a measure of volume productivity). The level of genetic improvement of each seedlot was determined by its GF Plus rating, a genetic rating system based on breeding values used for New Zealand radiata pine. There was a positive relationship between GF Plus rating and both productivity measures. Differences of 25% in total standing volume at age 30 years and of 5.6% in site index were found between unimproved (GF Plus 9.9) and highly improved (GF Plus 25) seedlots. Each unit increase in GF Plus rating was associated with a 1.51% increase in volume growth rate. In absolute terms, the magnitude of the increase was greater on more productive sites compared with less productive sites, although in percentage terms, it varied little between sites or regions. Quantification of genetic gain in this manner enables it to be easily incorporated into existing growth and yield simulators.

Background Douglas-fir comprises 6% of New Zealand’s planted forest area and contributes to the national carbon sequestration estimate. Carbon stock changes in Douglas-fir stem wood can be calculated by multiplying the increment in stem volume under bark by the density of the growth sheath and the carbon fraction. This paper describes a new model developed to predict variation in wood density of Douglas-fir growth sheaths from known wood density drivers. Methods Datasets used to parameterise the wood density model contained: (1) mean breast height (1.4 m above ground) outerwood (based on 50 mm long cores) density of 30 trees per stand from 32 semi-mature and mature stands with soil and climate data, for predicting wood basic density from environmental factors; (2) basic density of wood samples taken at breast height and at regular height intervals along the stem of 75 trees from 10 stands, for predicting the weighted mean wood basic density of pre-defined growth sheaths; and (3) breast height pith-to-bark radial density profiles based on 500 trees from 47 stands, for predicting wood density of individual annual growth rings at breast height. Linear and non-linear mixed models were developed using these data to explain the variation in wood density of growth sheaths. Results Breast height outerwood density was positively related to mean annual air temperature and negatively related to soil nitrogen fertility. This environmental model jointly explaining 83% of the variation in wood basic density at breast height of ring 30 from the pith. The radial pattern of wood density variation of annual growth rings at breast height was calibrated to a site using predictions from the environmental model. The ratio of growth sheath density to breast height ring density was applied to the predicted density of annual growth rings at breast height. This ratio decreased from 1.05 close to the pith to 0.95 in outerwood rings of mature trees, with ring number from pith explaining 49% of the variation in this ratio. Conclusions A wood density model that incorporates the important drivers of variation in density of stem wood growth sheaths in New Zealand-grown Douglas-fir will improve the accuracy of carbon stock and stock change estimates in NZ’s planted forest estate. The new wood density model has been linked to the Forest Carbon Predictor which predicts carbon stocks in live and dead biomass pools from inventory plot measurements, site mean annual temperature, and soil nitrogen fertility information.

International audience; This paper focuses on an analysis of planted forests data from the 2015 Forests Resources Assessment of the U.N. Food and Agriculture Organisation (FRA 2015). It forms one of a series of papers in the FRA 2015 special issue of this journal. While total forest area decreased from 4.28 billion hectares to 3.99 billion hectares from 1990 to 2015, with percent global forest cover dropping from 31.85% to 30.85%, the area of planted forests increased from 167.5 to 277.9 million hectares or 4.06% to 6.95% of total forest area. Increase was most rapid in the temperate zone, and regionally in East Asia, followed by Europe, North America, and Southern and Southeast Asia. However the annualised rate of increase in area of planted forests slowed in the 2010-2015 period to 1.2%, below the 2.4% rate suggested is needed to supply all of the world's timber and fibre needs. The majority of planted forests comprised native species with only 18-19% of the total area being of introduced species. Introduced species were dominant in the southern hemisphere countries of South America, Oceania and Eastern and Southern Africa where industrial forestry is dominant. Twenty countries accounted for 85% of planted forest area and a different 20 countries for 87% of planted forest roundwood supply. As with forest area, roundwood supply from planted forests also showed an increasing trend although this was based on minimal data. There was a mismatch in composition and rankings of the top 20 countries with top forest area and roundwood production suggesting that there are substantial opportunities to increase roundwood production in the future, especially in China which has the largest area but is currently ranked 3rd in roundwood production. Outlook statements were developed for the FAO sub regions based on past changes in planted forest area, population growth, and climate and forest health risks to identify key issues for the future. The overall view from this study suggests that climate impacts, especially from extreme climatic events will affect planted forests in the future and that forest health impacts can also be expected to increase. Outlooks vary regionally. Europe and North America are likely to be most concerned with climate and health risks; Asia will experience population pressure that will impact on land availability for new forests and risks from extreme weather events, and will need to make the most of its existing forests; Africa will need to increase planted forest area to offset continuing deforestation and rapid population growth; and Oceania, the Caribbean, Central and South America are likely to be most concerned with climate impacts. To ensure the continued contribution of planted forests, a number of responses will be required to both maintain existing and also to develop new forests. Intensification of production in existing forests will lessen the need for greater forest areas and offset any land use conflicts related to food security; climate adaptation strategies will need to be developed as a matter of urgency, and forest health focus must remain a priority for research. Establishment of new forests will be eased through greater community and stakeholder engagement. Application of models such as WWF's New Generation Plantations, which recognises the importance of society and the need to consider the full range of forest products and services within the wider landscape and spectrum of land uses, will be important. We recommend that to enable deeper analysis related to planted forests future FRA Assessments consider ways to better gather data specific to planted forests such as productivity so that this important component of global forests can be better understood.

The development of robust and accurate methods for counting trees from remotely sensed data could provide substantial cost savings in forest inventory. A new methodology that provides a framework for calibrating tree detection algorithms to obtain accurate tree counts for even-aged stands is described. The methodology was evaluated using two tree detection algorithms and two operators using airborne laser scanning ALS and orthophotograph images for four Pinus radiata D.Don stands ranging in age between 5 and 32 years with stand densities ranging between 204 and 826 stems ha−1. For application of the methodology to ALS images the error of estimate on the total count was 4.7% when calibration counts from actual ground plots were used and 10.5% when calibration counts from virtual plots on the image were used. For orthophotographs, the error of estimate was 6.1% using ground calibration plots and 24.3% using calibration counts from virtual plots. The described methodology was shown to be robust to variations in the process from the two operators and two algorithms evaluated. The measure of accuracy determined using the methodology can be used to provide an objective basis for evaluating a wide range of tree counting and detection processes in future research.

Summary Understanding the effects of interspecific competition on long-term growth of plantation forestry crops is critical to forest management decisions around methods used for weed control. A series of permanent sample plots (31) incorporating trees maintained either weedy or weed-free until canopy closure were established across New Zealand between 2000 and 2002. We used the age shift method to characterise growth responses of Pinus radiata, in New Zealand, to interspecific competition over the first third of a typical rotation. Eight years after planting, age shifts between treatments ranged between � 0.60 years and +3.07 years. On average, the age shift due to weed control increased from 0.62 to 0.96 years between 4 and 8 years of age. This was due to divergent tree growth between weedy and weed-free plots at 55% of the sites, while at 32% and 13% of sites, respectively, differences between treatments remained constant or decreased beyond age 4 years. The magnitude of the age shift was found to be related to the type of weed dominating early interspecific competition, with woody weeds associated with significantly greater age shifts. Continued divergence in tree growth between weedy and weed-free treatments up to 8 years after planting at the majority of sites was an unexpected result and contrasts with previous literature. In situations where growth divergence continues beyond 2 years, managers should consider continued treatment of weeds to mitigate the detrimental impacts of on-going

Summary Conifer species, which have formed the foundation of commercial forestry industry in many countries, are known to be invasive in natural ecosystems, especially in the Southern Hemisphere. Controlling isolated invasive conifers before they reach reproductive maturity is an essential element of any strategy that aims to reduce spread rate of these species. Using a novel helicopter-mounted spot-application gun, which delivers a precise dosage to the crown of each tree, the objective of this research was to test the efficacy of three triclopyr-based treatments against the four most vigorous wilding conifer species (Pinus contorta, Pinus nigra, Pinus sylvestris and Pseudotsuga menziesii) under New Zealand field conditions. Herbicides tested were triclopyr at two different rates and a combination of triclopyr and picloram. Treated trees covered a wide range of heights (c. 0.5–16 m), and measurements of mortality taken two years post-herbicide application were used to examine variation in efficacy of the herbicides. Successful treatment was defined by a mortality rate of 85% or higher. A logistic regression model was fitted to the mortality data and used to derive threshold tree heights at which 85% mortality occurred, H85. For all four species, the most effective treatment was application of 1000 ml of herbicide mixture per tree that contained 120 and 20 g, respectively, of the active ingredients triclopyr and picloram. There was a significant decline in efficacy of this treatment with increases in tree size for all four species. Values of H85 for this treatment were 7.4 m for P. nigra, 8.3 m for P. menziesii, 9.7 m for P. contorta and >10 m for P. sylvestris. The methods developed here could be used to effectively manage emerging conifer infestations before they become problematic.

Summary Two studies were undertaken in a young New Zealand Pinus radiata stand to find a biological control agent for armillaria root disease caused by Armillaria novae-zelandiae. Fresh thinning stumps were inoculated with saprophytic basidiomycete species as wooden dowel cultures or as homogenized aqueous mycelial suspensions, while all stumps were also inoculated with dowel cultures of A. novae-zelandiae. After a period of between one and two years, no differences were found among test fungi in the percentage of Armillaria species isolated from stumps. However, inoculation of Stereum sanguinolentum as homogenate, and of Phlebiopsis gigantea, Sistotrema brinkmannii, Hypholoma acutum and Rigidoporus concrescens as dowel cultures, significantly increased their isolation incidence in comparison with stumps not treated by these species. Phlebiopsis gigantea, Resinicium bicolor and R. concrescens were also isolated with greater frequency nearer to their dowel inoculation points. Results suggest that P. gigantea and S. sanguinolentum should be included in further testing. However, a future trial is likely to be more effective if evaluation is directed towards the portion of the stump below the soil surface, particularly the root system.

BACKGROUND The objective of the present study was to determine the contribution of the active ingredient (AI) and surfactant, and their concentrations, to the foliar uptake of agrichemicals, and to examine the physical properties that would need to be included in a model for foliar uptake. RESULTS All spray formulation component variables significantly affected uptake, explaining 73% of the deviance. The deviance explained by each factor ranged from 43% (AI concentration nested within AI) to 5.6% (surfactant). The only significant interaction was between AI and surfactant, explaining 15.8% of the deviance. Overall, 90% of the deviance could be explained by the variables and their first-order interactions. CONCLUSIONS Uptake increased with increasing lipophilicity of the AI at concentrations below those causing precipitation on the leaf surface. AI concentration had a far greater (negative) effect on the uptake of the lipophilic molecule epoxiconazole. The uptake of 2-deoxy-D-glucose (DOG) and 2,4-dichlorophenoxyacetic acid (2,4-D) increased with increasing hydrophile–lipophile balance (HLB) of the surfactant, the effect of HLB being far greater on the hydrophilic molecule DOG. However, the differences observed in epoxiconazole uptake owing to the surfactant were strongly positively related to the spread area of the formulation on the leaf surface. For all AIs, uptake increased in a similar manner with increasing molar surfactant concentration. © 2014 Society of Chemical Industry

Climate is an important driver of the establishment and impact of invasive alien species. Species transported to new regions can only invade those with a climate that meets their thermal requirements, but climate change is likely to alter the invasibility of recipient environments. Likewise, species are unlikely to reach pest status where climatic conditions are suboptimal. Here our objectives were to determine the relationship between climatic conditions and flight activity of two alien pine bark beetles (Hylastes ater and Hylurgus ligniperda) and to anticipate how climate change may affect the future distribution of these species. We used elevational gradients and slope aspect (north versus south-facing slopes), which are known to affect microclimates, to assess the effects on beetle flight across 18 locations in pine forests in the South Island, New Zealand. Using panel traps baited with alpha-pinene and ethanol we caught a total of 45,363 H. ligniperda and 6676 H. ater. Catches of both species decreased significantly and substantially with increasing elevation. Significantly more beetles were caught at north-facing than at south-facing sites towards the end of the flight season in autumn, leading to an extended flight period at northerly aspects. These results are important for pest management and the identification of ‘areas of low pest prevalence’ as a measure to reduce post-harvest infestations of logs destined for export. For example, during risk periods, logs could be harvested preferentially from stands with reduced flight activity (i.e., southerly aspects and higher elevations). Furthermore, such sites could be chosen to reduce post-harvest infestation risks during periods of temporary log storage at skid sites in the forest. Our findings are also important because climate change can be an important factor contributing to population expansion of bark beetles, and warmer temperatures could lead to increased flight activity and abundance, as well as enhanced suitability of sites that are currently less favourable.

Soil fertility is one of a number of environmental and biotic drivers of Pinus radiata (D. Don) productivity in New Zealand’s planted forest estate. However, its importance as a driver of productivity at a national scale is uncertain. This paper uses New Zealand’s planted forest inventory plot network, which encompasses a wide range of planted forest environments in New Zealand, to quantify climatic, soil, and biotic drivers of P. radiata productivity. The P. radiata index of site productivity used in this study, the 300 Index, is defined as the mean annual increment in stem volume under bark at age 30 years, of stands growing at a final crop stocking of 300 trees per hectare, and thinned and pruned following a standardised regime. This site productivity index was found to be significantly related to climate (30 year normalised average temperature and rainfall), solar radiation (corrected for slope, horizon and aspect using a digital terrain model), tree health, and soil fertility variables. After adjusting for the effects of solar radiation, temperature and rainfall, site productivity across the New Zealand planted estate was found to be negatively related to the soil C/N ratio and positively related to the size of the soil organic matter pool. The size of the organic matter pool could be represented in the regression model by either the total carbon, total nitrogen, or organic phosphorus concentration of the topsoil. Of these three soil variables, soil total nitrogen was statistically the most significant variable in the model, when analysed in conjunction with the soil C/N ratio. Afforested pastoral farmland previously treated with phosphatic fertilisers to stimulate nitrogen-fixation by leguminous species had soils with a lower C/N ratio and a higher organic matter content. This contributed to an 18% gain in P. radiata productivity compared to land without an agricultural land use history. Having established a relationship between the P. radiata productivity index and climate and soil fertility key drivers, we also consider methods for improving regression model accuracy.

To evaluate the effects of debris dams on aquatic invertebrate communities, we sampled benthic invertebrates in debris dams and riffles in three forested headwater streams in New Zealand. As part of a large-scale field experiment, debris dams were subsequently removed from three treatment sections in each of the streams to assess effects on invertebrate communities. Prior to debris dam removal, total invertebrate densities in debris dams were not significantly different from those in riffles. However, densities of Ephemeroptera, Plecoptera and Trichoptera taxa were significantly higher in debris dams than in riffles. Debris dams contained a higher number of less common taxa (defined as

Wood density is considered a primary property because of its strong correlation with stem stiffness, and also because it is central to the accounting of carbon sequestration in plantations. Using an extensive dataset (n = 1214) of Pinus radiata outerwood density, the objectives of this research were to (i) develop a model of outerwood density, (ii) characterise the functional form of the relationships found between independent variables and outerwood density, (iii) from the final model develop a P. radiata outerwood density map for New Zealand, and (iv) investigate the influence of spatial scale on the accuracy of model predictions. Validation data (n = 200) found the final model accounted for 70% of the variance in outerwood density. The model included three significant (P

Historic deforestation has deprived many river systems of their natural wood loadings. To study the effects of the loss of wood from waterways, a field trial was conducted in three small forested streams in New Zealand. The objectives were to (i) examine differences in fish assemblages among wooded pools (where wood provided cover), open pools and riffles and (ii) measure the effects of wood removal on channel morphology and fish assemblages. In the first part of the study, no significant differences were found in total fish density among the three habitats. However, total fish biomass was significantly higher in wooded pools (64% of total fish biomass) compared with open pools and riffles. Mean density and biomass of banded kokopu (Galaxias fasciatus) and mean biomass of longfin eel (Anguilla dieffenbachii) were highest in wooded pools, whereas the density and biomass of bluegill bully (Gobiomorphus hubbsi) and torrentfish (Cheimarrichthys fosteri) were highest in riffles. In the second part of the study, wood was removed from a 200-m section (treatment) in each stream, significantly reducing pool area and increasing the proportion of channel area and length in riffles. At the habitat scale, banded kokopu and large longfin eel were the two species mostly affected by wood removal. At the reach scale, banded kokopu biomass was significantly lower in the treatment sections. Although wooded pools were a small portion of total habitat, they provided important habitat for two of New Zealand's larger native fish taxa.

Chinese Fir and Moso bamboo are the two most important forest plantation species in subtropical China. However, information on greenhouse gas emissions from these forests is still scarce. A field study was carried out to compare soil CO2 flux dynamics in Chinese Fir and Moso bamboo forests over a 12-month period using the LI-8100 Soil CO2 Flux System. The soil CO2 flux in both forest types showed similar daily and seasonal dynamic patterns with the highest soil CO2 efflux at 14:00–16:00 in summer and the lowest in winter. Moso bamboo forest showed significant higher (P