Showing papers on "Pinus radiata published in 2017"

Differences in constitutive and inducible defences in pine species determining susceptibility to pinewood nematode

Abstract: The pinewood nematode, Bursaphelenchus xylophilus, originating from North America (NA), is a major invasive pine pest in Eurasia. It was first detected in Portugal in 1999 associated with maritime pine, Pinus pinaster, and has been differently affecting the main local pine species, P. pinaster and P. pinea. Field studies and direct inoculation experiments in Pinus spp. seedlings, under controlled conditions, were performed to assess whether the differences in constitutive and inducible defences are determining the different susceptibility of pine host species to B. xylophilus. Host co-evolution with the pathogen was also assessed, including the NA P. radiata, widely used in forestry in the northeast of the Iberian peninsula. Pine mortality in the field was positively related with the abundance of B. xylophilus, and concentration of phenolics and condensed tannins in pines. In the greenhouse assay, seedling tissues were analysed for constitutive investment in defences, as well as the potential inducibility of those defences as driven by B. xylophilus inoculation. Slower growing P. pinea presented higher levels of constitutive defences than faster growing P. pinaster, with only P. pinaster being affected by B. xylophilus. Furthermore, co-evolution with the pathogen is important, with the fast-growing NA P. radiata presenting an inducible and effective response to B. xylophilus. Results point to the importance of integrating data on pine life history traits, including growth rate, and production of constitutive and inducible defences, into predictive models for this invasive forest pest.

Kinetics of pyrolysis of litter materials from pine and eucalyptus forests

Abstract: Wildfires are an integral feature of the Australian continent. To estimate the rate of spread of wildfires using computational models it is important to know the kinetic parameters of the materials that constitute the fuel load in forests. These kinetic parameters are utilised in pyrolysis and combustion sub-models of a computational model. In the present work, the kinetics of pyrolysis of timber and litter materials (consisting of bark, twigs, and leaves) from Pinus radiata and Eucalyptus obliqua subsp. messmate forests were estimated under nitrogen. The activation energy for the pyrolysis of timber was found to be independent of conversion, whereas it varied for the litter materials in the range of the pyrolysis temperatures employed. Furthermore, the parameters pertaining to a single equivalent reaction model were also identified. For the samples studied, the most suitable reaction model was identified as the Johnson–Mehl–Avrami model. The activation energy measurements reported here are consistent with measurements previously reported for other species within the Pinus and Eucalyptus genera.

The effect of surface fire on tree ring growth of Pinus radiata trees

Abstract: Pinus radiata trees showed significantly reduced basal area increments and increased latewood/earlywood ratios, when their stem was charred by surface fires even if no needle damage occurred. An interaction of fire damage and precipitation on growth was observed. Heat from forest fires is able to penetrate beyond the bark layer and damage or completely kill a tree’s cambium. Short-term growth reductions following surface fires have been reported for some species. However, most studies have in common that they describe a compound effect of stem and foliage damage. This study investigated the impact of surface fires on the radial growth of Pinus radiata, where only the stem of trees was charred, while no needle damage was recorded. Tree ring measurements were performed on cores obtained at breast height. Analysis of variance and tests, based on annual basal area increment values were calculated to quantify pre- and post-fire growth differences of tree ring width and latewood/earlywood ratios. The analysis revealed significant growth reductions following a surface fire on P. radiata in the year on which the fire occurred as well as in the following year. As a consequence of the fire, basal area increment and latewood/earlywood ratios were significantly reduced. An interaction of fire damage and precipitation on growth was observed. The obtained results show how fires without crown damage can affect growth and tree ring structure of P. radiata trees and indicate that stem char could be associated with a significant decrease in ring width and latewood/earlywood ratio.

Chemical control of two Phytophthora species infecting the canopy of Monterey pine (Pinus radiata)

Abstract: Summary Twelve active ingredients were screened for their ability to control foliage disease caused by Phytophthora kernoviae and Phytophthora pluvialis. Inhibition of mycelial growth and sporangial production of both pathogens were assessed in in vitro assays after exposure to three concentrations of each active ingredient. While most of these active ingredients inhibited mycelial growth in vitro, due to their widespread use, phosphite, copper oxychloride and metalaxyl-M were selected for further study. Four rates of each active ingredient were applied to two Pinus radiata genotypes, and detached needle assays at 6 and 90 days post-treatment were used to determine treatment efficacy and persistence. Untreated needles showed significantly larger lesions than all fungicide-treated needles after exposure to P. pluvialis or P. kernoviae on both sampling dates. Efficacy and persistence of the three active ingredients did not increase with increase in concentration. Larger lesions were formed on more susceptible genotype after inoculation with both Phytophthora species, even when higher rates of active ingredients were applied. Phosphite, copper oxychloride and metalaxyl-M have potential to protect commercially planted P. radiata from these two Phytophthora species.

Topochemical analyses of furfuryl alcohol-modified radiata pine (Pinus radiata) by UMSP, light microscopy and SEM

Abstract: Furfurylation is one of the wood modification techniques via catalytic polymerization of the monomeric furfuryl alcohol (FA) in the impregnated cell wall. Little is known about the topochemistry of this process. Brown rot degradation begins with lignin modification and therefore, the reactions between FA and lignin was one focus of this research. Furfurylated radiata pine (Pinus radiata) with three different weight percent gains (WPGs of 57%, 60% and 70%) after FA uptake was observed by cellular ultraviolet microspectrophotometry (UMSP) to analyze chemical alterations of the individual cell wall layers. Moreover, light microscopy (LM) and scanning electron microscopy (SEM) analyses were performed. The ultraviolet (UV) absorbance of the modified samples increased significantly compared to the untreated controls, indicating a strong polymerization of the aromatic compounds. Highest UV absorbances were found in areas with the highest lignin concentration. The UMSP images of individual cell wall layers support the hypothesis concerning condensation reactions between lignin and FA.

Biocontrol of Fusarium circinatum Infection of Young Pinus radiata Trees

Abstract: Pitch canker, caused by the fungus Fusarium circinatum, is a major disease of Pinus radiata currently controlled to some extent in nurseries by good hygiene and application of synthetic fungicides. The aim of this study was to evaluate alternative strategies to control fungal infections in nurseries and young pine plantations. The antagonistic effects of biocontrol bacteria and essential oils against F. circinatum in vitro and in young P. radiata trees were assessed. Pseudomonas fluorescens, Erwinia billingiae, and Bacillus simplex reduced the growth of the fungus in vitro by 17%–29%, and decreased the density of the mycelial mat. In young P. radiata trees, the length of F. circinatum lesions was reduced by 22%–25% by the same bacterial strains. Direct application of cinnamon and/or clove essential oils to wounds in stems of two-year-old P. radiata trees also limited the damage caused by F. circinatum. Lesion length was reduced by 51% following treatment with cinnamon oil (10% v/v), and by 45% following treatment with clove oil (15% v/v) or a combination of both oils. However, the oils were toxic to younger trees. The biocontrol bacteria and essential oils show promise as prophylactic treatments to reduce the devastating effects of F. circinatum on P. radiata.

Biogenic Formaldehyde: Content and Heat Generation in the Wood of Three Tree Species

Abstract: Global trends in allowable formaldehyde (CH2O) emissions from nonstructural wood-based composites require a renewed consideration of biogenic CH2O from wood. Increment cores from living Virginia pine (Pinus virginiana), yellow-poplar (Liriodendron tulipifera), and radiata pine (P. radiata) trees were used to measure CH2O and CH2O generation due to heating (200 °C, 10 min). Significant variations within and between trees of the same species were observed. Tissue types (juvenile/mature, heartwood/sapwood) sometimes correlated to higher CH2O contents and greater heat-generation potential; however, this did not always depend upon species. Heating increased CH2O levels 3–60-fold. Heating with high moisture levels generated more CH2O than that generated from dry specimens. Radiata pine generated extraordinarily high CH2O levels when heated, far exceeding the other species. It was suggested that pine extractives might catalyze CH2O generation, perhaps in lignin. Regarding wood-based composites, findings suggeste...

Detecting the spread of invasive species in central Chile with a Sentinel-2 time-series

Abstract: The presented work evaluates the potential of a Sentinel-2 time-series to detect Pinus radiata (Monterey Pine) invasions in endemic Nothofagus (Southern Beeches) forests in the Maule region, central Chile. Suitable cloud free images of the phenological cycle were selected from six Sentinel-2 scenes available for the years 2016. The scenes were unmixed using a non-negative least square (nnls) algorithm for different landcover components per pixel. The results were validated with a SVM classification of UAV-based hyperspectral mosaics acquired in March 2016. The results show that it is possible to map the coverage of the Pinus radiata class up to an accuracy of R2 ∼ 0.6 and RMSE of ∼ 10 %. Generally, a higher number of Sentinel-2 images increased the performance of the model, while there was no significant dependency on a specific acquisition date. However, the variability of the results is high, which indicates that a careful selection of multi-temporal endmembers is crucial to a successful unmixing of Pinus radiata.

Exposure to a pine pathogen enhances growth and disease resistance in Pinus radiata seedlings

Abstract: Summary Most studies of Fusarium circinatum, the cause of pitch canker in pines, have focused on its activity as a pathogen. However, recent findings indicate that this fungus can colonize roots of Pinus radiata without inducing symptoms. Contrary to expectations, this study revealed that seedlings grown in infested sand grew more rapidly than seedlings not exposed to F. circinatum, based on root and shoot biomass, with modifications to root system architecture, including increased mycorrhizal root development. These effects were dependent on inoculum density and duration following growth in infested rooting medium. Plants exposed to F. circinatum expressed elevated resistance to stem infections, which significantly decreased the incidence of mortality; as above, effects were dependent on inoculum density. Resistance to stem infections was also enhanced in seedlings that emerged through infested litter, as occurs in native stands. Beneficial to neutral interactions of F. circinatum with its host suggest that the life history of this fungus may be more complex than previously recognized, with activities similar to non-pathogenic endophytes. The potential for non-lethal infections by F. circinatum to induce resistance in seedlings may influence dynamics of stand establishment. Overall, these results indicate that pathogenic organisms with asymptomatic states may have cryptic ecological functions that extend beyond the impacts of disease.

Effects of thinning and pruning on stem and crown characteristics of radiata pine (Pinus radiata D. Don)

Abstract: Simultaneous applications of thinning and pruning are common silvicultural practices in radiata pine (Pinus radiata) forest plantations. Their separate effects on tree growth and wood quality have been well studied, but their combined effect is not clear yet. The aim of this study is to identify how thinning and pruning together affect the stem structure and properties of the pruned but also the unpruned section of the trees (the portions formed immediately after the application of these management efforts). The effects of pruning and thinning on the number of growth units per year, internode length, number of branches, and branch diameters was analyzed in managed and unmanaged stands of radiata pine grown in Chile. When used jointly, these practices generated larger individual tree volumes (135% more) and clear wood in the pruned logs; however, they also reduced the sawn wood quality of the unpruned stem section for some years after the silvicultural interventions. The managed trees showed more growth units per annual shoot and shorter internodes, thus generating more knotty wood. Moreover, managed trees showed more taper. As trees of the managed stand restore the foliar biomass lost due to pruning, managed and unmanaged stands approach the same level of canopy closure, and differences minimize.

Effect of temperature on electrical conductivity of green sapwood of Pinus radiata (radiata pine)

Abstract: Joule heating of green Pinus radiata, if controlled in a range 60–90 °C, has the potential to be used for veneer cutting, improving the peeling process and the quality of veneer. This research attempts to study the wood’s electrical conductivity, one of the key variables in controlling the Joule heating effect. Electrical conductivity of green New Zealand grown radiata pine sapwood was studied over a 20–90 °C temperature range. The sapwood studied had moisture content in the range of 100–200%. The effects of wood parameters such as grain orientation, moisture content, and basic density were evaluated. The effects of temperature and grain orientation on the conductivity were found to be much greater than those of moisture content and basic density. At 23 °C, conductivity in the longitudinal direction was around 20 times higher than in the tangential and 10 times higher than in the radial direction. Between 23 and 90 °C the longitudinal conductivity increased threefold, near linearly with temperature, whereas the tangential and radial conductivities increased nonlinearly by factors of 6 and 4, respectively. A statistical model based on the experimental results has been developed using the linear mixed effect model.

Nurse tissue for embryo rescue: testing new conifer somatic embryogenesis methods in a F1 hybrid pine

Abstract: This is the first report of (1) somatic embryogenesis in the hybrids of Pinus attenuata with Pinus radiata var. cedrosensis and (2) use of Pinus radiata somatic embryogenic tissue as nurse tissue to facilitate initiation from immature hybrid pine zygotic embryos. Embryogenic cell lines were successfully initiated from first generation reciprocal hybrids of Pinus radiata var. cedrosensis and Pinus attenuata, using P. radiata protocols. This is also the first report of P. radiata somatic embryogenic tissue used as a nurse to facilitate initiation from excised zygotic embryos. Two media formulations were tested, Glitz and Glitz2. Both media are based on a modified Litvay medium. The medium Glitz differs from Glitz2 in absence of casein, an increase in l-glutamine concentration and addition of asparagine. Overall analyses of treatment effects showed the excised zygotic embryo treatments, with or without the nurse on Glitz medium, were significantly better for cell line establishment (47 and 45 %, respectively) than either of the megametophyte treatments or the Glitz2 excised embryo treatment (p ≤ 0.05). Total cell line establishment irrespective of hybrid cross combination, collection time and cultural treatment was 32 %. Establishment percentages within each of the reciprocal hybrids, five crosses of each, across all four collections and cultural treatments, were not significantly different despite significant differences in zygotic embryo development (p ≤ 0.05). From response to the initiation treatments tested in this research, P. attenuata appears to be a much better mother than P. radiata var. cedrosensis with 39 % of cell lines established compared to only 23 % from P. radiata var. cedrosensis. However, analyses of variance results did not indicate that this difference between the two hybrid types was significant, probably due to the large amount of variation among the individual crosses within each of the hybrid types.

Conversion of Pinus radiata plantations to native forest after harvest operations: a north Iberian Peninsula case study

Abstract: There is broad consensus on restoration of native woodlands in places where intensive forestry is nowadays not profitable. However, this consensus is lost when stakeholders need to implement forest management practices as restoration tool, especially because there is a substantial lack of empirical evidence about its feasibility. In this context, we assess the impact of two different harvest treatments on understorey plant species composition of Pinus radiata plantations as tools to recover native woodland vegetation in northern Iberian Peninsula. Here, common clear-cut treatment and restoration-clear-cut where only pine trees were removed (i.e. reducing the disturbance effect over understorey vegetation) were compared against understorey plant species composition of young and old plantations and restored tracks. The aim was to identify which treatment is more suitable to recover native woodland vegetation. The results reveal that both clear-cuts maintained species composition plus important understorey native species, some of them being restoration targets. However, both clear-cuts showed diversity reductions compared with old plantations, although there were not apparent retention effects on compositional change towards native communities at least two years after harvest. It seems that the remaining vegetation established by natural succession after both clear-cut treatments could be used to achieve initial restoration objectives for some native tree and understorey plant species at relatively low costs. In any case, it would be interesting to implement supplementary management measures to accelerate this conversion, such as invasive species elimination or target species seeding, to maintain local biodiversity and introduce native woodland species not present in the area.

Accompanying vegetation in young Pinus radiata plantations enhances recolonization by Ceroglossus chilensis (Coleoptera: Carabidae) after clearcutting

Abstract: The replacement of native forests by Pinus radiata plantations modifies habitat availability and quality for wildlife, constituting a threat to species survival. However, the presence of understory in mature pine plantations minimizes the negative impacts of native forest replacement, rendering a secondary habitat for wildlife. Whether forest-dwelling species recolonize clear-felled areas pending on the spontaneous development of accompanying vegetation growing after harvesting is yet to be assessed. In this context, we analyze the abundance, movement and habitat selection of the endemic ground beetle Ceroglossus chilensis (Coleoptera: Carabidae) in an anthropic forest landscape consisting of native forest remnants, adult pine plantations (> 20 years) with a well-developed understory, and young (1–2 years) pine plantations with varying degrees of accompanying vegetation development. Particularly, we analyze the likelihood that C. chilensis would recolonize young pine plantations depending on the presence (> 70% cover) or the absence (< 20% cover) of this accompanying vegetation. C. chilensis shows a greater probability of selecting habitats with understory (pine plantations and native forest) and young plantations with accompanying vegetation (future understory) than habitats without such vegetation. Movement of C. chilensis also favors their permanence in habitats with understory vegetation, coinciding with higher abundances than in young pine plantations devoid of accompanying vegetation. Hence, the effect of clearcutting could be mitigated by allowing the development of accompanying vegetation into a future understory, which facilitates the recolonization of pine plantations and its use as secondary habitat for wildlife.

Small, fragmented native oak forests have better preserved epiphytic lichen communities than tree plantations in a temperate sub-oceanic Mediterranean climate region

Abstract: In increasingly fragmented landscapes tree plantations are thought to help maintain forest continuity among native patches. Epiphytic lichens are one of the most sensitive groups to change in forest conditions, but the effects of this management practice are still poorly studied in temperate regions. In this study we compared epiphytic lichen diversity among small patches of old, native oaks (Quercus pyrenaica) and young, planted chestnuts (Castanea sativa) and Monterey pines (Pinus radiata) in a major forestry area in northwestern Spain. Our results showed that the richness of epiphytic lichens was higher in C. sativa than Q. pyrenaica, but that the latter had more lichen species typical of mature forests, including macrocyanolichens. Overall, C. sativa plantations had more species typical of well-lit, dry environments than Q. pyrenaica or P. radiata, which is likely caused by the natural architecture of each tree species, and to differences in forest age and management. At the tree level, Q. py...

Alternative pine hybrids and species to Pinus patula and P. radiata in South Africa and Swaziland

Abstract: Through the collaborative efforts of companies affiliated with the International Program for Tree Improvement and Conservation (Camcore), a number of pine hybrids have been produced over the last decade. Many of these have been planted in trials across southern Africa that broadly represent winter and summer rainfall areas, with the latter ranging from warm to cold temperate sites. The five-year survival and growth of the hybrids and other pines in 12 of these trials were compared with Pinus radiata in the winter rainfall, and P. patula in the summer rainfall, regions where these species have been planted extensively. Except for the highest altitude site, where freezing conditions are common, the survival of most hybrids and tropical pines was better than P. patula or P. radiata . This was, in part, attributed to their improved tolerance to the pitch canker fungus, Fusarium circinatum , which was present in the nursery at the time of planting. In the winter rainfall area, the P. elliottii × P. caribaea hybrid, P. maximinoi and, surprisingly, the P. patula hybrids performed well. In the summer rainfall regions, hybrids with tropical parents such as P. caribaea , P. oocarpa and P. tecunumanii were more productive in the subtropical/warm temperate zone and, with increasing elevation, those hybrids crossed with P. patula performed relatively better. The P. patula × P. tecunumanii hybrid, particularly when crossed with low-elevation P. tecunumanii , performed exceptionally across most sites. Keywords: productivity, survival, tolerance

Biochemical responses associated with induced resistance to Colletotrichum acutatum in Pinus radiata seedlings treated with methyl jasmonate and Trichoderma spp.

Abstract: Summary The effect of Trichoderma (T. atrobrunneumFCC320 and T. atrovirideLU633) and/or methyl jasmonate (MJ) on resistance to terminal crook (Colletotrichum acutatum) and on seedling biochemistry was investigated in radiata pine (Pinus radiata) seedlings. Seedlings were germinated and grown in Trichoderma-amended or non-amended media for 3 months and then sprayed with 2.25 mM MJ 1 week before inoculation with C. acutatum. The incidence and severity of terminal crook in the seedlings treated with MJ and Trichoderma+MJ were lower than in Trichoderma-treated and Trichoderma-untreated seedlings. The MJ-induced resistance response was concomitant with an increase in the concentrations of the monoterpenes α-pinene, β-pinene, β-phellandrene, camphene and myrcene in needles, and also α-pinene, β-pinene and camphene in stems. The concentrations of α-pinene, β-pinene and camphene were elevated from at least 1 week until 4 weeks after MJ application, compared with those in non-MJ counterparts. Trichoderma alone did not affect monoterpenes, but the concentrations of α-pinene, β-pinene and camphene were greater in needles of Trichoderma+MJ than in MJ-treated seedlings after 28 days. Total phenolic concentration in needles and peroxidase activity in stems were twofold greater in MJ-treated seedlings than in non-MJ seedlings over the same period. None of the treatments affected the activity of peroxidase in needles. It is proposed that the accumulation of monoterpene and phenolics and the induction of peroxidases contribute, in part, to MJ-induced resistance to terminal crook in radiata pine seedlings.

Effect of Proanthocyanidin-rich Extracts from Pinus radiata Bark on Termite Feeding Deterrence

Abstract: Antioxidants are known to affect the feeding habits of termites and a good source is pine bark which contains high levels of antioxidants which can be extracted with neutral solvents. In this study procyanidins (PCs)-rich MeOH-extract and a hot-water extract (HWE) were prepared from Pinus radiata bark. HWE was further separated into crude PCs (CPCs), polymeric PCs (PPCs), and low-molecular-weight PCs (LMWPCs) fractions. The MeOH extract and these fractions were examined for termite (Reticulitermes flavipes Kollar) antifeedant activities using a no-choice test. Catechin was used as a positive control. The LMWPCs was found to be the most effective deterrent to termite feeding. The comparative efficiency of the compounds tested were LMWPCs > PPCs > CPCs > MeOH extract, with the latter being more dependent on molecular weight than on its antioxidant activity.

The effect of native forest replacement by Pinus radiata plantations on riparian plant communities in Chile

Abstract: Background: As riparian habitats are legally protected, they have been maintained even in areas where extensive reforestation by exotic species occurred in areas surrounding riparian environments. However, the extent to which the riparian plant communities have been affected by the replacement of native forest on slopes has rarely been investigated.Aims: In this study, we evaluated the effects of replacement of native forest by Pinus radiata plantations, on the diversity and structure of plant communities of remnant forests preserved in riparian habitats.Methods: We selected five watersheds with native forest and five watersheds where the native forest had been replaced by pine plantations preserving riparian forests and compared composition, diversity and structure of riparian vegetation.Results: In watersheds with pine plantation, riparian forests had lower adult tree density, tree cover, diversity and regeneration and higher shrub cover, diversity of herb species and diversity and richness of exotic sp...

Seasonal Terpene Variation in Needles of Pinus radiata (Pinales: Pinaceae) Trees Attacked by Tomicus piniperda (Coleoptera: Scolytinae) and the Effect of Limonene on Beetle Aggregation.

Abstract: Concentrations of four monoterpenes were determined in needles of Pinus radiata (D.Don) (Pinales: Pinaceae) trees that were attacked or nonattacked by Tomicus piniperda (L.) (Coleoptera: Scolytinae). Compounds were identified and quantified by gas chromatography-mass spectrometry. The mean ambient temperature was obtained using climate-recording data loggers. The effect of limonene on field aggregation was also evaluated at three limonene release rates using Lindgren attractant-baited traps and trap logs. Attacked trees produced less α-pinene in March, July, and November than nonattacked trees, less β-pinene in July and November, and less limonene from May to November. Limonene reduced the attraction of T. piniperda to attractant-baited traps and trap logs. Results were linked to better responses to high temperatures, with respect to terpene contents, by the nonattacked trees after the spring attack.

Effect of harvesting season, system and equipment on in-forest Pinus radiata bark removal in Australia and New Zealand

Abstract: Depending on the point of view of the participants in the forest-to-customer supply chain, the presence of bark can be considered as either a benefit or a cost. Understanding which factors affect bark removal should help with managing bark quantities, and the design of harvesting systems and equipment. Over 4000 stems and logs in 11 studies were measured in Australia and New Zealand using digital photos and a line intercept method to determine the amount of bark removed during normal operations. Among other things, we have been able to show that bark removal is greater in spring than winter, with tree-length systems than cut-to-length systems, and with mechanized processing rather than manual processing systems. We were also able to show that the greatest portion of bark removal occurs during felling and extraction with tree-length operations, with a small proportion occurring during delimbing and bucking. There was limited and weak evidence that bark removal may differ with location on pine stems...

Herbicide options for managing competitive vegetation during the establishment of Pinus radiata and Pseudotsuga menziesii var. menziesii in Southland, New Zealand

Abstract: Control of weeds is important for survival, growth and uniformity of planted conifers, such as Pinus radiata D.Don and Pseudotsuga mensiesii var. menziesii (Mirb.) Franco. Despite pressure to find environmentally benign herbicides for these species, little research has identified non-residual herbicides that are cost-effective and result in minimal growth loss compared to those used operationally. The objective of this study was to compare efficacy and cost of current operational practice to a range of alternative herbicide treatments for the establishment of these two species using data from two trials located at the same site. Treatments for each species were applied in both the first and second year following planting and included weed-free controls, operational practice using terbuthylazine and hexazinone (applied as both spot treatment and broadcast application) and a range of treatments consisting of combinations of clopyralid, triclopyr and haloxyfop (CTH), applied with or without oversowing with less competitive grasses and annual herbaceous species. Application of glyphosate during winter was included within the Pseudotsuga mensiesii trial as a first year treatment only and as a second year treatment following spot application of CTH in the first year. For the Pinus radiata trial, broadcast application of CTH in spring of years 1 and 2 was most effective, with mean stand volume (m3 ha−1), at 2.5 years, exceeding the weed-free control and operational treatment by 8 and 11%, respectively, although these differences were not statistically significant at the 5% level. Use of the operational treatment as a spot in the first year, followed by broadcast application of CTH in the second year, was moderately effective when used with or without oversowing. For the Pseudotsuga mensiesii trial, the four most effective treatments were the operational treatment, broadcast application of CTH during year 1 (CTH-Dec), broadcast application of CTH during spring of years 1 and 2, and broadcast application of glyphosate during winter (winter glyphosate). Although not significantly different, at 2.5 years mean stand volumes in these treatments were on average 24, 29, 33 and 35% lower than the weed-free control, respectively. Both CTH-Dec and winter glyphosate were less expensive than the operational treatment. These results highlight potential treatments to either replace terbuthylazine and hexazinone, or reduce their use during establishment weed control for Pinus radiata and Pseudotsuga menziesii, notably for sites dominated by Cytisus scoparius L. (Scotch broom).

Microcomputer tomography (microCT) as a tool in Pinus tree breeding: pilot studies

Abstract: Pinus breeding programmes yield high numbers of seeds, but a non-destructive method to determine seed viability is still lacking. With the long reproductive cycle (up to 28 months) of Pinus species, determining when fertilisation occurs can assist when applying tissue culture methods like somatic embryogenesis (SE). For SE, pre-cotyledonary zygotic embryos are ideal for culture initiation (some weeks after fertilisation), while mature zygotic embryos are extracted and used for in vitro amplification during organogenesis. Achieving automated viability assays in extracted seeds would also be helpful, as would being able to find numbers and condition of seeds in immature or unopened cones. For such applications, microcomputer tomography (microCT) was a candidate technology. MicroCT was used to scan immature cones of Pinus radiata D.Don at four-weekly intervals after pollination to determine time of fertilisation. After harvesting of mature cones, a sample of 30 seeds of each of three Pinus species (P. radiata, P. patula Schiede ex Schltdl. & Cham. and P. pinaster Aiton) were scanned together in one microCT scan, and the same seed was allowed to germinate on moist filter paper after scanning. In addition, a mature unopened cone of P. radiata was also microCT-scanned to determine the potential for determining seed viability in situ, and the seed was subsequently extracted for examination. Fertilisation evidently occurred between weeks 64 and 68 after pollination in P. radiata. The microCT data for extracted seeds of the three species identified some seeds with large voids, which suggest non-viability (low to zero germination potential), and that was confirmed by the germination test. In addition to demonstrating in situ seed viability in the unopened P. radiata cone, the seed extraction revealed that some non-viable seeds remained trapped in the basal part of the dried cone. This case study demonstrates the feasibility of using microCT scans as a partially non-destructive method in Pinus tree breeding programmes to confirm fertilisation and determine seed viability. However, scanning the seed after extraction from mature cones can help to determine viability which is often hard to gauge from seeds’ external appearance. Future studies need to narrow the time window of fertilisation by scanning a wider variety of genotypes between weeks 64 and 68 after pollination.