Light Detection and Ranging (LiDAR) has been successfully used to describe a wide range of forest metrics at local, regional and national scales. However, little research has used this technology in young Douglas-fir stands to describe key stand characteristics used as criterion for operational thinning. The objective of this research was to develop models of Douglas-fir mean top height, basal area, volume, mean diameter (at breast height), green crown height and stand density from LiDAR and stand information. Methods: Data for this study were obtained from four widely separated young (age range of 9 to 17 years) Douglas-fir plantations in the South Island, New Zealand. LiDAR was acquired for the entire area and stand metrics were measured within 122 plots established across the study area. Spatially synchronous stand and LiDAR metrics were extracted from the plots. Using this dataset, multiple regression models were developed for each of the six stand metrics. Results: The final models constructed for mean top height, green crown height, total stem volume, mean diameter, basal area, and stand density had R2 values of 0.85, 0.79, 0.86, 0.86, 0.84 and 0.55, respectively, with root mean square errors of 1.02 m, 0.427 m, 20.2 m3 ha-1, 13.9 mm, 3.81 m2 ha-1 and 355 stems ha-1, respectively. With the exception of stand density, all relationships were relatively unbiased. Variables with the greatest contribution (with the partial R2 in brackets) to models of mean top height, green crown height, volume, mean diameter and basal area included the 75th (0.85), 1st (0.76), 10th (0.83), 95th (0.74), and 10th (0.72) LiDAR height percentiles. The LiDAR height interquartile distance was the most important contributor (partial R2 = 0.33) to the model of stand density. Conclusion: With the exception of stand density, the final models for stand metrics were sufficiently precise to be used for scheduling thinning operations. This study demonstrates the utility of LiDAR to accurately estimate key structural attributes of young Douglas-fir and to assist with forest management over a widely dispersed resource.

This paper examines current herbicide use in New Zealand planted forests. Compliance of key herbicides with existing Forest Stewardship Council (FSC) standards, the key environmental certification body within New Zealand, is also reviewed. Methods: Information obtained from a survey of six forest companies operating in New Zealand was used to identify major herbicides used by the New Zealand planted forest industry, estimate quantity of herbicides used on an annual basis and also determine changes in weed management practices motivated by certification. Results: Glyphosate was the most widely used active ingredient in pre-plant weed control with terbuthylazine and hexazinone used most widely for post-plant weed control. Together these herbicides comprise 90% of the estimated 447 tonnes of active ingredient that is annually used. Average aerial application rates for these three active ingredients were estimated at 3.3 kg ha-1, 7.0 kg ha-1 and 1.8 kg ha-1, respectively. Use of terbuthylazine and hexazinone is restricted on FSC-certified forests subject to derogation. Environmental certification has resulted in a shift from broadcast application of terbuthylazine and hexazinone to greater use of spot weed control in the first year after tree planting. Spot weed control can reduce the amount of active ingredient used by up to 89%. Non-chemical weed control is not widely used by the forest industry as it is not as cost-effective as current herbicide regimes. A review of the literature indicated that, when used operationally and according to label registrations, these herbicides are unlikely to have any negative impacts on the planted forest environment. Although they have been detected in groundwater, under multiple land uses, concentrations were at levels below documented safe drinking standards. There are limited data for forest soil and no data on the effects of these herbicides on aquatic biota in New Zealand. Conclusions: At present time there is insufficient information to support or refute the prohibition of terbuthylazine and hexazinone in New Zealand's planted forests. This has highlighted a need to conduct field studies to determine the fate and behaviour of terbuthylazine and hexazinone in planted forests in New Zealand.

A survey was conducted to assess the uptake, and barriers to use, of geospatial tools and technologies amongst New Zealand's plantation forestry sector. Methods: Responses were received from 17 companies representing 63% of New Zealand's plantation forest by area. A wide range of company sizes were surveyed (net stocked areas ranged from 4,000 - 200,000 hectares), and 7 of the 17 have international operations. Results: Survey results suggest that freely available topography, climate, and soil datasets have limited utility, as forest management at the operational level requires higher resolution, remotely sensed data. The most common supplemental data are aerial photography or satellite imagery. High spatial resolution was more highly valued by respondents than spectral diversity (i.e. number of channels); only six companies regularly use imagery containing an infrared band. LiDAR data has been used regularly by only three New Zealand forestry companies, while another six have tried it, suggesting it is an emerging technology in New Zealand. The use of generic GIS software was common amongst all respondents (14 use the ESRI product ArcGIS, three use MapInfo produced by Pitney Bowes). The utility of ArcGIS, in particular, was enhanced by locally developed extensions designed to address specific operational tasks performed regularly by New Zealand's forestry companies. Conclusions: While it is clear that geospatial data and tools are generally adopted by New Zealand's forest industry, cost-related barriers prevent their widespread adoption. Interestingly, a lack of staff knowledge was also conceded an impediment to uptake, alluding to the importance of tertiary education in the geospatial sciences and continuing education for practitioners.

LiDAR is an established technology that is increasingly being used to characterise spatial variation in important forest metrics such as total stem volume. The cost of forest inventory and LiDAR acquisition are strongly related to the inventory plot size and the LiDAR pulse density, respectively. It would therefore be beneficial to understand how reductions in these variables influence the strength of relationships between LiDAR and stand metrics. Although relatively high pulse densities are required for creating Digital Terrain Models (DTMs), once a DTM has been developed there is scope for reducing pulse density on subsequent flights to estimate stand metrics from LiDAR. This study used an extensive national dataset (for which the DTM had been characterised) obtained within New Zealand's planted forests. Using this dataset, the objective of this research was to investigate how variation in both pulse density and plot size influence the precision of relationships between LiDAR metrics and total stem volume. Methods: LiDAR metrics were thinned to pulse densities ranging from 0.01 to 4 pulses m-2 across plot sizes ranging from 0.01 to 0.06 ha. For each pulse density/plot size combination regressions between LiDAR mean height and total stem volume were fitted using parameters fixed at values for the unthinned dataset or separately fitted for each pulse density/plot size combination. Results: Using the unthinned dataset (plot size = 0.06 ha; pulse density = 4 pulses m-2) the relationship between the mean LiDAR height and total stem volume had a coefficient of determination (R2) of 0.77. Thinning of the data had little effect on R2 above plot sizes of 0.03 ha and pulse densities of 0.1 pulses m-2. As pulse densities decreased below 0.1 pulses m-2 within plots of less than 0.025 ha, there was a sharp decline in R2 reaching values as low as 0.48 in plots of 0.01 ha with pulse densities of 0.01 pulses m-2. Simulations where parameters were fixed yielded almost identical R2 values to those where they were refitted for each plot size/pulse density combination. The number of pulses per plot integrates the effect of these two factors, with little change in the precision of the volume function until a threshold of 100 pulses per plot was reached. Conclusions: This study showed that the precision of LiDAR-volume equations was relatively insensitive to reductions in pulse density and plot size when an accurate DTM was available. Acquisition of LiDAR information at lower pulse densities is likely to markedly improve the cost efficacy of this information for inventory purposes.

Efforts to address erosion and land degradation in steeplands of many countries have largely relied on revegetation. The policy responses to this issue are many and varied as have been their successes. Revegetation efforts tend to occur when it is realised that deforestation, mountain land erosion, and flooding of rivers are linked. Methods: Using the Southern Prealps region in France and the East Coast North Island region of New Zealand as 'study sites', past and current revegetation efforts to address steepland degradation were compared. Results: Both areas have similarities in geology, geomorphology and types of erosion processes (shallow landsliding and gullying). Landscape responses to large-scale erosion and subsequent reforestation have been similar between France and New Zealand though major reforestation occurred in France more than a century before that in New Zealand. Attempts to control sediment production in headwater regions reinforces the view that conditions controlling the evolution of channel response (through time and space) to a change in sediment supply are complex. While there is a consistent sequence of responses in channels and on hillslopes to reforestation efforts and the direction of changes may be anticipated, the magnitude and timing of those responses are not. Conclusion: The key lesson for future management and policy development arising from these studies is that erosion-control efforts that are aimed at producing basin-scale impacts will require targeting of areas where the proposed land use change or intervention will have the most beneficial influence on reducing sediment supply to river channels.

Nectria flute canker is an important disease of Pinus radiata in the South Island of New Zealand. The causal agent of the disease, Neonectria fuckeliana, is a known wound invader of Picea abies in Europe. To test the hypothesis that pruning wounds are necessary for infection of Pinus radiata by N. fuckeliana, the presence of the fungus was assessed in pruned and unpruned trees. Methods: The presence of the fungus was investigated in a total of 180 trees (90 pruned and 90 unpruned) using both DNA and microbial culturing techniques over three consecutive years. The data was analysed using a logistic regression analysis. Results: It was found that there was no significant difference in the presence of the fungus in pruned and unpruned trees. Conclusions: These results indicate that pruning wounds are not the primary infection court for N. fuckeliana and that the fungus is able to enter the tree through an alternative infection point.

Spiral grain angle (SGA) is an important factor affecting the distortion and utilisation of solid timber. Little research has investigated how SGA varies at a fine scale within trees and whether this fine-scale three-dimensional variation is similar between genotypes. The objectives of this research were to (i) characterise three-dimensional variation in SGA within stems and clones, and (ii) understand how intra-stem variation in SGA varies between genotypes. Methods: Detailed measurements of SGA were taken from 12 radiata pine (Pinus radiata D. Don) clones. Analyses were undertaken to characterise variation in three dimensions and determine if this variation significantly differed between genotypes. Results: Spiral grain varied significantly with distance from the pith, showing a sharp initial increase with distance from the pith, followed by a gradual decline. Values of SGA increased significantly with height up the stem, reaching a maximum at ca. 5 m. Circumferential variation in SGA showed no significant trend. There was significant variation in mean SGA between clones; however, the within tree patterns in SGA did not significantly vary between clones. Conclusion: If further research confirms the uniformity of within tree patterns in SGA between clones this may greatly simplify efforts to model three-dimensional variation in SGA.

A number of data sources currently exist that can provide information on forest plantations at a range of scales over an entire rotation cycle. In particular, LiDAR is quickly becoming the technology of choice for harvest planning and providing local-scale estimates of forest structure. Its application is still limited as repeat annual acquisition at this scale is generally cost prohibitive. Development of temporally updateable models that can accurately project important metrics such as tree height between LiDAR acquisitions would be of considerable use to resource managers. The objective of this research was to develop models of Pinus radiata height using GIS spatial data supplemented with RapidEye satellite imagery. Methods: Multiple regression models were constructed to describe maximum canopy height (Hm) derived from LiDAR at two relatively distant study sites located in Kaingaroa and Tairua forests. A randomised selection of 300 m2 circular plots was made at both sites and average values of Hm within these plots were used for the modelling. Sources of information used for predicting Hm included stand age and spatial information describing environmental variables and stand productivity. This information was supplemented with spectra and vegetation ratios derived from high resolution RapidEye satellite imagery. Results: The most robust models of Hm that were developed for both sites included a combination of the crop age obtained from the stand GIS, Site Index (obtained from a GIS surface) and the red-edge vegetation ratio (REVI) The final models of Hm had respective R2 of 0.99 and 0.94 for the Kaingaroa and Tairua sites. At both sites, stand age was the strongest predictor of Hm. However, the inclusion of REVI from high resolution imagery did add an updatable temporal dimension to the model. Changes in REVI are sensitive to the impacts of abiotic and biotic factors that are not captured by stand age and Site Index. Conclusion: Applied operationally, this model can be used in a GIS environment to estimate tree height and identify areas of anomalous growth or disturbance caused by wind, snow, fire or disease.

Mechanical bending stress due to tree sway in strong winds and water stress during drought are thought to contribute to the formation of resin pockets, but it is unclear if these are linked and whether the initiation of resin pockets is influenced by the water status of the trees at the time of stem bending. Methods: The effect of stem bending on the formation of resin pockets was evaluated under various soil moisture conditions. The stems of 12-year-old radiata pine (Pinus radiata D.Don) trees were bent mechanically in spring or summer when the soil was water deficient, and in summer after rehydration. After the completion of the growth season, a selected sample of trees was felled and stem discs were assessed for the presence of resin pockets, using disc photos and image analysis. All stem bending treatments were compared with control trees. Results: Stem bending in spring or summer was found to increase the number of Type 1 resin pockets, but had no effect on the number of Type 2 resin pockets. The soil moisture conditions at the time of stem bending had no effect on the number of Type 1 or 2 resin pockets. Conclusions: The Type 1 resin pockets occurred in the inner part of the early wood, adjacent to the growth ring boundary. This suggests the Type 1 resin pockets were initiated in the mature wood, behind the cambium and zone of differentiation, and were not influenced by the water status of the tree stems at the time of stem bending.

Thinning and fertilisation are two silvicultural tools which can modify the growth of a stand. Thinning re-allocates the resources on a site to increase the growth of the trees remaining after the thinning but does not necessarily increase total stand volume as compared to an unthinned stand. Fertilisation is intended to increase the growth of all trees in a stand resulting in more volume. Understanding the response of fertilisation and thinning treatments is critical to making good silviculture prescriptions. To assist with making these prescriptions, yield models for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) on coastal sites of British Columbia, Canada were developed. Douglas-fir and western hemlock are the two most important species on these sites. Methods: The data for the modelling came from a large fertilisation and thinning trial (EP703). The model for total volume is based on the Chapman-Richards function. One parameter of the model was expressed as a function of a previous measurement and the other two parameters, which are in turn expressed as a linear function of site index and thinning and/or fertilisation intensity. Results: Independent models were fitted for both species in the study using maximum likelihood estimation. The models were programmed into a spreadsheet to evaluate the behaviour of the models and examine selected responses. Conclusion: These growth and yield models for Douglas-fir and western hemlock allow forest practitioners to evaluate the outcomes of proposed silviculture prescriptions.

Timber from old-growth stands of coast redwood (Sequoia sempervirens (D.Don) Endl.) is dimensionally stable, resistant to surface checking and splitting, and has been widely used for outdoor purposes such as decking and cladding. Restrictions on the supply of redwood timber from Californian stands have increased the focus on timber from plantations grown elsewhere in comparatively short rotations. Little is known about the quality of timber produced from plantations of redwood in New Zealand. Methods: In this study trees from a 38-year-old pruned stand in Mangatu Forest near Gisborne, New Zealand, selected to cover the range of stem diameters present, were cross-cut into logs. Each log was then sawn into boards and each board was graded according to a simplified United States redwood grading system. Results: Total timber volume (50 logs) was 16.2 m3, valued at USD 7,835 (2008 prices). This was less than might be expected in a well-managed stand. The 13 pruned logs accounted for 38% of the total volume recovered and 50% the total financial value of the timber. Pruned log quality assessed according to a pruned log index (PLI) was low, due to untimely pruning and the presence of epicormic shoots. Only 12% of the timber was graded clear and 32% of this came from pruned logs. Despite low PLI scores, the relationships between PLI, proportion of clear timber and pruned log value were reasonably strong. Conclusions: Recoveries from individual stems were variable. The most important determinants of log value were log size, which affected timber recovery; pruning quality, which governed the volume of clear wood; the proportion of heartwood, (valued for durability and appearance); and to a lesser extent, mid-stem branch vitality. High incidence of dead (bark-encased) knots in most of the unpruned logs contributed to the poor timber grade recovery results. Other defects (insect tunnels, rot and traumatic resin pockets) were associated with a 7% reduction in financial value. Accurate prediction of the pattern of distribution of heartwood inside a redwood log could play a major role in maximising the value of recovered timber.

Measurements of stress wave velocity were performed with the Fibre-gen Director ST300 on 146 hybrid poplar (Populus sp.) plantation trees from GreenWood Resources Inc. located near the city of Boardman, Oregon USA. A laser scanner (Faro Focus 3D) was used to measure the curvature of the trees. Combinations of two software tools (Treemetrics Autostem and Sweep Extractor) were used to calculate the curvature for two log lengths (3 and 6 m) from a height of 10 cm above the ground. The propagation velocities of the stress waves were measured twice; first at breast height on the convex side of the stem and then at 90 degrees clockwise around the stem from the first measurement. Results and Conclusions: Analysis of the data showed that there was no significant difference (p = 0.24) between propagation velocities when the probes were located on either the convex side or at 90 degrees to the convex side. However, the propagation velocity was significantly greater on trees with higher curvature, suggesting that the velocities measured with the ST300 can take into account the presence of reaction wood (tension wood) in the tree.

Trials to compare eucalypt species from the blue gum group, including Eucalyptus bicostata Maiden, Blakely & Simmons, E. globulus Labill., E. maidenii F. Muell., and E. pseudoglobulus Naudin ex Maiden were established in 1999 at three sites in the North Island of New Zealand (Northland, Bay of Plenty, and Hawke's Bay). Each species was planted out in replicated 49-tree plots consisting of seven individuals from seven provenances. Only two provenances of E. pseudoglobulus were available and these were outcompeted by inter-planted E. globulus so were not formally assessed. Measurements taken at age seven years indicate a strong species × site effect for foliage health, stem straightness and survival. Generally, growth and foliar health were best at the Hawke's Bay site. Provenance x site interaction was mostly absent for each of the blue gum species. However, there was a significant provenance variation for most traits within E. bicostata, and provenance x site interaction; both of which were largely driven by the performance of the northernmost Wollemi provenance. While some interactions occurred at the species × site level, E. maidenii performed consistently well in growth, stem straightness and health compared with the other taxa. Eucalyptus maidenii appears to be the fastest growing of the species tested within the broad region covered by the study sites, in the warmer coastal areas of New Zealand's North Island.

When aerial LiDAR data is used to construct Digital Elevation Models (DEMs) under vegetation, DEM quality will invariably suffer due to attenuation of the laser pulses by the land cover. Although the ratio of ground returns to outgoing pulses (GRper) is known to vary widely for forest applications, little research has quantified the influence of forest stand structure and site conditions on this ratio. An understanding of how these factors influence GRper is crucial for the development of accurate DEMs. Methods: Using an extensive national dataset obtained from New Zealand's plantation forests the objective of this research was to develop a multiple regression model of GRper that could be used to specify the necessary LiDAR pulse density for development of accurate DEMs. Results: Within the dataset GRper averaged 30.5% ranging from 0.73 to 92.2%. The final model of GRper included stand age, crop density, non-crop density and slope and accounted for 48% of the variance in GRper with root mean square error (RMSE) of 13.9%. The percentage of ground returns declined exponentially as stand age, crop and non-crop density increased and declined linearly with increases in slope. GRper was not substantially affected by either the pulse density, stand aspect or whether the stand comprised Pinus radiata or Pseudotsuga menziesii. Conclusion: The developed model highlights the sensitivity of GRper to stand and site conditions. This model is likely to be of considerable use in defining the optimal LiDAR pulse density across a range of forest environments.

Historically, a series of regional height-age functions have been used to predict height growth of Pinus radiata in New Zealand. However, for some regions there are no available models while other regions have more than one available model. Methods: To remedy this situation, a new system of height-age growth models for P. radiata in New Zealand was developed from a nationwide database using nonlinear mixed modelling techniques. Results: When tested by cross validation, a simple national model performed poorly compared to a series of models with different parameters for each region, demonstrating the existence of regional differences in the form of the height-age relationship. Examination of the regional behaviour suggested that the effect of temperature is best represented by a common-asymptote family of curves, while other factors such as water availability and nutrition appear to be better represented by anamorphic families of curves. A national height-age model reflecting this behaviour was developed. This model is a polymorphic form of the Bertalanffy-Richards function, with the slope parameter expressed as a linear function of latitude and elevation. Conclusions: This general model was found to perform better than a series of regional models, and is therefore recommended as a general purpose height-age model for P. radiata in New Zealand.

Standard protocols for extracting genomic DNA from Pinus radiata D. Don needles, such as CTAB-based methods, can yield large quantities of DNA. However, final DNA purity can be an issue due to carry over of contaminants that can impede accurate high throughput genotyping. This study evaluated eight DNA extraction and purification protocols to determine which method provided the greatest improvement in call rates and accuracy when using the Sequenom iPLEX® Gold MassARRAY® genotyping technology. Of the methods tested, genomic DNA extracted using the Machery-Nagel NucleoSpin®-96 Plant II kit performed the best overall, and was more efficiently and accurately genotyped than genomic DNA extracted using the standard CTAB method. This study also demonstrated that the quality and assay performance of CTAB-extracted genomic DNA is greatly improved by further purification with the Qiagen® QIAquick 96 PCR Purification kit. Using these improvements, the Sequenom iPLEX® Gold MassARRAY® genotyping technology is now a viable option for genotyping plant genomes such as Pinus radiata.

To improve production efficiency and harvesting economics some forest companies are looking at extended hours of use for forest machinery, which may include longer shift lengths, multiple shifts per day, and more harvesting days per week. A review of the literature provides mixed signals on the costs and benefits of extending work hours. Methods: A long-term data base, which contained over 30 000 machine day records and was maintained by a Chilean forest company, was used to evaluate the effects of three types of extended work schedules (beyond a 9 hour work day) on the productivity of two types of harvesting operations; mechanised processing of Pinus radiata D. Don (radiata pine) stems into logs and mechanised harvesting of eucalypt (Eucalyptus globulus Labill and E. nitens H. Deane and Maiden) trees. Results: Production increased as working hours increased. However, average hourly productivity fell by 9 to 30% as the working day length for equipment was extended from 9 to 18 hours. A range of factors, some interacting, were found to affect the level of decrease. These factors included type of work schedule, type of operation, season, tree species, and tree size. Conclusions: Extending working hours beyond 9 hours per day did not result in equivalent increases in production for mechanized harvesting operations in Chile. Further research is needed on the overall economics of working extended hours.

Light Detection and Ranging (LiDAR) is an established technology that has been shown to provide accurate information on individual-tree and stand-level forest structure. Although LiDAR has been widely used to describe stand structural dimensions the utility of this technology to predict spatial variation in wood quality traits is largely unexplored. This study used LiDAR metrics to predict spatial variation in total stem volume (TSV) and outerwood stress-wave velocity (V) in an even-aged mature forest (25 yrs) of moderate size (stocked area of 217.8 ha). Outerwood stress-wave velocity is a good predictor of modulus of elasticity which is a key performance criterion for structural timber. Methods: Linear and non-linear models were developed to predict TSV and V. Models of TSV were developed from the full dataset that included 163 plots while models of V were developed from a subset of 32 plots in which V had been measured. Results: The best statistical models that included only LiDAR data, explained 60% and 37% of the variation in TSV and V, respectively. Addition of measured stand density to both models significantly improved the R2 to, respectively, 0.76 and 0.70 for TSV and V. The root-mean square error for the final models of TSV and V were, respectively, 64.0 m3 ha-1 and 0.086 km s-1. Conclusion: At the forest level LiDAR metrics were found to be useful for predicting both V and TSV. Further research should examine the link between LiDAR metrics and V across broader ranges of V to confirm these findings.