ALBERT

Description: There is a strong policy move in Britain to improve forest resilience to climate change by increasing stand structural and species diversity. Although currently little used in Britain, the technique of underplanting allows regeneration and diversification of stands while avoiding some of the disadvantages of clearfelling. Two experiments were examined: (1) the growth and survival of five underplanted conifer species of differing shade tolerance in a shelterwood and (2) compared performance of underplanted and open-grown Douglas-fir seedlings on restocking sites. Underplanted Sitka spruce, Norway spruce, noble fir, European silver fir and Douglas-fir were all able to survive and grow. However increased exposure following overstorey removal resulted in some damage and ‘socketing’, especially to taller seedlings, particularly Douglas-fir. This may be linked to poor root development when growing under an overstorey. Microclimate conditions on some underplanted sites were more sheltered from extreme climatic conditions, and in some cases this improved survival of Douglas-fir seedlings. However, seedling growth rates were reduced compared with those on open sites probably due to lower light levels. Underplanting may help to improve establishment success of some species, particularly in exposed areas. However, the shelter benefits of underplanting must be carefully balanced against the trade-off with lower light, and underplanting is likely to be more successful where low canopy density is maintained.

Description: The recent emergence of Olive Quick Decline Syndrome in Italy, caused by Xylella fastidiosa, has drawn attention to the risks posed by this vector-borne bacterium to important crops in Europe (especially fruit trees and grapevine). Comparatively very little is known on actual and potential impacts of this pathogen in forests, in the native (North American) and introduced (European) regions, respectively. The present review aims to address important questions related to the threat posed by X. fastidiosa to European forests, such as the following: What are the symptoms, hosts and impact of bacterial leaf scorch caused by X. fastidiosa on trees in North America? Which forest tree species have been found infected in the introduction area in Europe? How does X. fastidiosa cause disease in susceptible hosts? Are there any X. fastidiosa genotypes (subspecies and sequence types) specifically associated with forest trees? How is X. fastidiosa transmitted? What are the known and potential vectors for forest trees? How does vector ecology affect disease? Is the distribution of X. fastidiosa, especially the strains associated with trees, restricted by climatic factors? Is disease risk for trees different in forest ecosystems as compared with urban settings? We conclude by pointing to important knowledge gaps related to all these questions and strongly advocate for more research about the Xylella-forest pathosystems, in both North America and Europe.

Description: Wood removed in Southwestern US forest restoration treatments currently has limited markets and thus low value. One important property of wood in structural products is its stiffness (measured as modulus of elasticity), which is known to vary systematically within trees. Directly measuring wood stiffness is expensive, time consuming and destructive. Therefore, we tested samples of ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) from northern Arizona destructively in bending and also non-destructively using acoustic velocity (AV) methods. In total, we tested multiple pith-to-bark small clear (2.54 × 2.54 × 40.64 cm) samples from up to four heights in 103 trees. We first measured the standing-tree AV of sample trees, then the AV of small clear samples, and finally measured wood stiffness using three point static bending tests. We found that a Michaelis–Menten curve was a good fit to the radial profile of wood stiffness, with a steep increase outward from the pith that approached an asymptote. The AV of small clear samples, coupled with measured volumetric density values, approximated the static modulus of elasticity values with high accuracy (r2 = 0.86). At the stand level, a model predicting standing tree AV from tree morphology fit the data well (r2 = 0.77). Results indicate that southwestern ponderosa pine contains outerwood with relatively high stiffness that could be suitable for structural products. However, when assessed using wood stiffness, the trees take a long time to reach maturity (~50 years) and thus the corewood proportion is large. AV measurements are a good way to assess variability within and among stands and thus could be employed to segregate the resource by expected stiffness values. Segregation could help identify stands not suitable for structural uses and direct them toward more appropriate products.

Description: With a total area of several million hectares, mountain forests of Norway spruce ( Picea abies (L.) Karst.), silver fir ( Abies alba Mill.) and European beech ( Fagus sylvatica L.) connect the beech-covered lowlands and spruce-dominated alpine regions and still represent the most natural though managed forests in Europe. For sustaining their unique functions and services, their natural gap dynamics are emulated by the combined shelterwood–femel-coupe system. In the 1970s, 22 long-term experimental plots were established in the Bavarian Alps in order to substantiate the formerly mainly experience-based silvicultural prescriptions. After more than 40 years of successive surveys including the integrated evaluation of the old stands and the measurement of natural regeneration, analyses reveal: (1) The reduction of overstorey density is generally associated with a proportional reduction of the overstorey stand growth. So, the recommended 20–40 per cent density reduction of a combined shelterwood–femel coupe may reduce the mean annual increment also by ~20–40 per cent, but part of this loss is compensated by the additional growth of the regeneration. (2) Over time, the natural regeneration is continuously augmented by new recruitment of seedlings and saplings. (3) However, even 40 years after initiating regeneration, spruce is rare in the regeneration compared with fir, beech and other broadleaved species. Further observation will show whether spruce will catch up with the other species or whether it requires either larger disturbances than gap and femel coupes, or possibly planting. Based on these findings, a refined shelterwood–femel-coupe system is proposed and its advantages and disadvantages are discussed.

Description: Partial cutting practices are increasingly used in boreal forests for two major reasons: (1) maintaining age structure and tree diameter distribution according to the principles of ecosystem-based management and (2) increasing tree growth by decreasing competition. This study evaluated the effects of three different partial cutting treatments applied to even- and uneven-aged black spruce ( Picea mariana (Mill.) B.S.P.) stands in north-eastern Quebec, Canada. The effect of partial cutting was assessed by comparing treated and control plots in terms of age structure, diameter and spatial distribution, amount of deadwood and tree radial growth. Age structure and diameter distribution were not different from control plots after partial cuttings applied in both uneven-aged and even-aged stands, but lower deadwood basal area was observed. Tree radial growth generally increased in uneven-aged stands but can be limited by tree age and inter-tree competition. In even-aged stands, tree removal was more uniformly distributed and the overall reduction in inter-tree competition resulted in an increased tree radial growth. Overall, these results suggest that the studied partial cuttings were adequate for maintaining structural attributes and increasing tree growth, but adjustments should be made to treatments to increase the amount of deadwood to a level observed in natural forests and to lower inter-tree competition.

Description: The general belief that intense regeneration measures are financially viable and essential for high sustained yields of commercial forest products has been inadequately tested. This field experiment evaluates effects of three different regeneration intensities 24–27 years after clear-cutting of 14 sites across Sweden. The treatments, designated high (HI), normal (NI) and low (LI), respectively, consisted of: mechanical site preparation and planting of large seedlings at 2 x 2 m spacing, with supplemental planting and pre-commercial thinning (PCT) when deemed necessary; standard local practices; and natural regeneration with no site preparation, artificial regeneration or PCT. Average crop seedling densities were highest and lowest (3359 and 1662 ha –1 ) under the HI and LI treatments, respectively, 4–8 growing seasons after planting. After 24–27 years, HI also resulted in higher mean stem volume (90 m 3 ha –1 ) than LI (36 m 3 ha –1 ) but was not significantly different from NI (65 m 3 ha –1 ) and increasing the regeneration intensity was not consistently positive. In some cases, high planted seedling mortality and generally abundant natural regeneration resulted in minor (or no) differences between the treatments. The results illustrate that current Swedish regeneration standards may need revision in order to reflect contemporary societal and commercial demands.

Description: A healthy, productive and resilient workforce is important to any industry, and supporting the wellbeing of workers is a key factor in achieving this. Worldwide, the forest industry is amongst the most physically dangerous industries to work in. Workplace health and safety strategies have traditionally focused on improving the physical safety of forestry workplaces. It is equally important to consider the broader wellbeing of workers, not only to ensure their quality of life, but also to support a healthy and sustainable workforce with low turnover. To do this, it is critical to understand the work-related factors that affect worker wellbeing. We examine this via a survey of workers in the Australian forest industry. We find that work-related factors known to influence wellbeing in other industries, such as income, job security and workplace culture, are strongly correlated with forest worker wellbeing, that negative perceptions of the forest industry by those outside it are associated with lower levels of worker wellbeing and that the extent to which a forest industry worker has a strong work-related social identity is associated with their wellbeing. Our findings highlight the importance of implementing workplace strategies that consider wellbeing in broader terms than the traditional focus on physical safety.

Description: Botryosphaeria canker is likely the most injurious disease for cork production in the Mediterranean Basin. The exclusion of Benomyl, the standard commercial product used to prevent Botryosphaeria canker, from the EU Pesticide Database in 2003 necessitates the search for new alternatives to prevent cork oak cankering. In vitro experiments showed that every fungicide tested at 10 3 mg l –1 active ingredient was effective in reducing mycelial growth of Diplodia corticola . An initial field experiment showed that cork oak trunks sprayed with Thiophanate-methyl, Carbendazim, Difenoconazole, Pyraclostrobin or Copper-Calcium Sulphate under low-humidity environmental conditions exhibited significant decreases in the number and length of trunk lesions, 3 years post-treatment, compared with untreated trees. A second field experiment conducted under extremely wet conditions showed that only Thiophanate-methyl was effective, 2.5 years after treatments, when sprayed just after peeling. Finally, in a third field experiment, under wet conditions, the preventive effectiveness of Thiophanate-methyl, Copper-Calcium Sulphate and a mix of both fungicides was confirmed, although no synergistic effect of the mixture was measured. Copper-Calcium Sulphate or Thiophanate-methyl, when applied immediately after trunk peeling, is effective for preventive control of Botryosphaeria canker on cork oak and may be considered as an effective replacement for Benomyl.

Description: Forests and trees throughout the world are increasingly affected by factors related to global change. Expanding international trade has facilitated invasions of numerous insects and pathogens into new regions. Many of these invasions have caused substantial forest damage, economic impacts and losses of ecosystem goods and services provided by trees. Climate change is already affecting the geographic distribution of host trees and their associated insects and pathogens, with anticipated increases in pest impacts by both native and invasive pests. Although climate change will benefit many forest insects, changes in thermal conditions may disrupt evolved life history traits and cause phenological mismatches. Individually, the threats posed to forest ecosystems by invasive pests and climate change are serious. Although interactions between these two drivers and their outcomes are poorly understood and hence difficult to predict, it is clear that the cumulative impacts on forest ecosystems will be exacerbated. Here we introduce and synthesize the information in this special issue of Forestry with articles that illustrate the impacts of invasions of insects and pathogens, climate change, forest management and their interactions, as well as methods to predict, assess and mitigate these impacts. Most of these contributions were presented at the XXIV IUFRO World Congress in 2014.

Description: Puccinia psidii is a major threat to members of the Myrtaceae worldwide. New Zealand is still free of P. psidii but possesses significant Eucalyptus plantations as well as valuable native tree species such as Metrosideros excelsa and Leptospermum scoparium that could be at risk in the event of an incursion. As part of preparing for a potential incursion, we generated a barcode reference library for 〉100 diverse species of Myrtaceae occurring in New Zealand by sequencing internal transcribed spacer (ITS), external transcribed spacer (ETS) and maturase K ( matK ), or by obtaining relevant sequences from GenBank. The Myrtaceae DNA barcoding database will enable rapid identification of large numbers of host species in the event of a myrtle rust incursion. We undertook a comparative analysis of the ability for the three mentioned loci to discriminate species. Interspecific divergence was assessed by mean interspecific distance, prime and minimum interspecific distance; intraspecific variation was evaluated by mean intraspecific difference, and coalescent depth. Overall identification efficiency of the three loci sequenced was determined using BLAST1 and Near Distance methods. Barcoding gaps between inter- and intraspecific divergences were also analysed. ITS and ETS share similar mean interspecific distance, prime and minimum interspecific distance values – both higher than obtained for matK . In contrast, in terms of intraspecific variation, matK had higher values than ITS and ETS in all three metrics analysed. ITS had the highest identification success rate for species followed by matK and ETS, respectively, as measured by BLAST1 and Near Distance methods. Overall identification success rate increases when a combination of ITS and matK in particular is used. The sequence data are not only a valuable reference collection for a myrtle rust response but also a national botanical resource.

Description: Future forests are being shaped by changing climate and disturbances. Climate change is causing large-scale forest declines globally, in addition to distributional shifts of many tree species. Because environmental cues dictate insect seasonality and population success, climate change is also influencing tree-killing bark beetles. The mountain pine beetle, Dendroctonus ponderosae , is a major disturbance in Pinus forests of the western US. Using a mechanistic, phenology-based demographic model driven by downscaled daily temperature data, we describe recent and future spatial and temporal thermal suitability for mountain pine beetle population growth in a topographically complex region. Trends in model-predicted growth rates among Global Climate Models were similar and suggest that, relative to future trends, mountain pine beetle population growth within the past 60 years was most optimal at middle elevations and least optimal at the lowest and highest elevations. This trend aligns with observed mountain pine beetle-caused tree mortality that was greatest at middle elevations between 1997 and 2013, as estimated from Aerial Detection Surveys. However, thermal suitability for optimal phenological synchrony was predicted to shift in recent years, and by the end of the century, the best thermal habitats for mountain pine beetle will be at the lowest and highest elevations. Mechanistic demographic models are valuable tools for modelling future thermal regimes that may be both beneficial and maladaptive for mountain pine beetle population growth and subsequent tree mortality.

Description: Forest degradation is a major issue for policy-makers that is exacerbated by no clear and globally accepted definition of the term. For forest managers, a loss of forest productive capacity is one form of forest degradation. We present a quantitative method to assess forest degradation from a productivity perspective. Our method uses a standard stocking chart and calculation methods based on standard forest inventory data, to derive a clear threshold value for stocking, below which a forest should be considered degraded. The method is illustrated using the example of a self-regenerating Nothofagus production forest type from Chile. For that forest type, we determined that harvesting trees to below a specific basal area relative to site type, resulted in a loss of resilience, an unpredictable shift in ecosystem state, and a degraded condition. Our method illustrates how over-harvesting can degrade the long-term productivity of a stand and forest resilience. Nevertheless, it is important to consider that forests can also be degraded from other perspectives, such as loss of biodiversity, carbon, or protective functions as a result of excessive disturbances. Ecosystem management requires that managers consider degradation from a range of perspectives. We see the quantified approach used here as a way to provide practitioners with, in part, a transition from sustained yield to ecosystem management with an ultimate objective of providing a pathway towards adaptive management of complex systems and avoiding degradation.

Description: The Asian longhorned beetle (ALB), Anoplophora glabripennis (Coleoptera: Cerambycidae), is one of the most harmful invasive species in Europe and North America, causing enormous economic damage to broadleaved trees growing in urban parks and gardens. As a quarantine species, everywhere it has been introduced ALB has led to the application of expensive eradication programmes often associated with additional indirect costs due to the loss of ornamental value connected with the presence of trees in urban areas. The aims of this article are to quantify the impact of ALB in terms of tree mortality and their ornamental value during the first year eradication of an infestation in Northern Italy, and to perform an economic assessment of the eradication programme vs inaction. During the first year of eradication 367 ALB infested trees were removed from the infestation area at a total cost of about 48 000, comprising scientific advice (21 per cent), tree survey (38 per cent) and plant removal (41 per cent). The ornamental value of the infested trees was assessed at about 850 per tree. The ALB eradication programme allowed a reduction of 52 per cent of the damage expected in the following year, corresponding to an ornamental value of about 300 000. The ornamental value of the saved trees was ~6 times higher than the costs for their protection.

Description: In this paper, we demonstrate the effectiveness of digital stereo images and canopy height models (CHMs) derived from them for forest height change assessment. Top heights were derived for 199 terrestrial inventory plots from forest inventories conducted in 2008 and 2013 in a forest near Traunstein, Germany. Semi-Global Matching was applied to two sets of aerial stereo images, acquired in 2009 and 2012, respectively, to compute CHMs. Subsequently, several height percentiles were calculated from the areas in the CHMs that lay within the inventory plot locations. The maximum CHM value ( h max ) had the highest correlation with the field-based canopy top heights and was selected for use in all further analysis. Periodic annual increments (PAIs) of forest height were calculated from both the remote sensing and the field data at the inventory plot locations. Scatterplots of the PAIs over top height revealed similar patterns in the results derived from the two data sets. The inventory plots were assigned to three height classes representing various forest successional stages – youth , full vigour and old age . The PAI distributions within the three height classes were significantly different from one another. Our findings suggest that CHMs derived from repeat aerial image surveys can be a viable tool to measure canopy heights and to assess forest height changes over time, even for a highly structured, mixed forest in central Europe.

Description: Growth models continue to be of importance in modern multi-functional forestry to provide forecasts. Bayesian calibrations allow both model structure and parameters to be assessed simultaneously in a probabilistic framework, providing a model with which forecasts and their uncertainty can be better understood and quantified using posterior probability distributions. A Bayesian calibration of a stand-level dynamic growth (SLeDG) model is carried out for both Sitka spruce and Scots pine in the UK for the first time. The calibration used the differential evolution Markov-Chain method to reduce the required number of iterations for inference. Two different model structures were considered for estimating local stand productivity: one using the measured height–age relationship, and one using estimated site yield class. The height–age relationship was shown to be more probable for both species in a Bayesian model comparison (total model probability $=$ 0.64 and 0.58 for Sitka spruce and Scots pine, respectively), although metrics of model performance were similar for both model structures ( $R^2 \geq 0.88$ in all variables). A complete calibration (using all data) of the more probable model structure was then completed, and excellent model fit was observed ( $R^2 〉 0.95$ for all variables in both species). Example forecasts using the output from the calibration were demonstrated, and are compatible with existing yield tables for both species. This method could be applied to other species or other model structures in the future.

Description: A UK field trial compared the efficacy of a range of synthetic herbicides and the fungal biocontrol agent Chondrostereum purpureum (Pers.) Pouzar at preventing resprouting of Rhododendron ponticum L. following cutting, and hence countering infection with Phytophthora ramorum Werres or P. kernoviae Brasier. Treatments were applied to cut rhododendron stumps in the summer and winter, and regrowth was evaluated 25 months after application. All chemical herbicide treatments significantly reduced regrowth, and would therefore help to lower reinfection by P. ramorum or P. kernoviae . Timing of applications (summer or winter) did not affect efficacy. Picloram was the least effective of the chemical herbicide treatments. A 20 per cent solution of Roundup Pro Biactive ® (360 g l –1 glyphosate; Monsanto) applied to stumps immediately after cutting was an effective, low-toxicity and inexpensive means of preventing regrowth, although some follow-up treatment was necessary. If approvals for glyphosate formulations were lost in the future, products based on triclopyr or picloram could be potential substitutes. Use of the wood-rotting basidiomycete C. purpureum as a biocontrol agent did not have a statistically significant effect in this study, although the possibility of a synergistic effect with glyphosate has not been ruled out. It is possible that any impact of the biological agent becomes apparent only over a longer time frame and thus extended assessment periods would be required. Refinement of the application technique and/or the formulation method as well as a more comprehensive strain selection might result in improved efficacy of the biocontrol treatment.

Description: Timber production and prices are determined by the global demand for forest products, and the capability of producers from many countries to grow and harvest trees, transform them into products and export. The Global Forest Products Model (GFPM) simulates how this global demand and supply of multiple products among many countries determines prices and attendant consumption, production and trade. This paper documents the methods, data and computer software of the GFPM model, followed by examples of applications to forecasting, and for policy analysis of the consequences of offset payments for carbon sequestration in forests.

Description: The properties of wood and wood tracheids from trees growing in peatland stands are still insufficiently known. The long-term effects of thinning on wood and tracheid properties of Scots pine ( Pinus sylvestris L.) were investigated in two thinning experiments on peatland sites in central Finland. The two sites were ditched for the first time in 1958 and 1973, and thinning experiments were established in 1987 and 1993, respectively. Thinning increased the basal area increment of the remaining trees by 20 per cent. No differences between the trees that were growing on the thinned plots and those that were growing on the unthinned control plots were found in the latewood proportion, wood density, tracheid diameter, cell wall thickness and tracheid length. Moreover, the wood and tracheid properties did not differ markedly from those of corresponding material originating from mineral soil sites. The results confirm the previous results on mineral soils, which showed that an increasing availability of resources primarily increases the rate of tracheid production but has no major effects on wood and tracheid properties.

Description: The removal of forest logging residues for bioenergy production is projected to increase by several orders of magnitudes in the near future. Little is known about the environmental consequences of this practice, however, especially in freshwater ecosystems. Using data from 18 headwater streams in central Finland, we assessed the responses of four lotic (diatoms, bryophytes, dipterans and benthic macroinvertebrates) and two riparian (bryophytes and vascular plants) organism groups to logging residue removal (LRR). The streams were divided in three groups: unharvested, conventional logging (no LRR) or LRR (both conventional logging and LRR). We hypothesized that conventional logging would result in intermediate biodiversity and environmental responses, with LRR showing the strongest effects. Contrary to our expectation, conventional logging elicited the strongest responses, whereas LRR had little additional impact when compared with conventional logging. This likely reflects a stricter adherence by the LRR operators to forest management guidelines. Our approach of comparing both conventional logging and LRR to unharvested sites yielded important insights that would have been missed otherwise. Rigorous monitoring using multiple taxonomic groups of both terrestrial and freshwater origin is needed to detect the long-term effects of LRR activities.

Description: Single-species planting of lodgepole pine ( Pinus contorta var. latifolia ) following clear-cut logging or wildfire has been common throughout interior British Columbia, Canada, but health problems with the species have been documented as it grows beyond the juvenile stage. We examined damage and stocking in twenty-seven 15- to 30-year-old lodgepole pine plantations that were previously declared free growing in the highly productive cedar–hemlock forests in southeastern British Columbia, where lodgepole pine is absent from many primary forests. In order to be free growing, stands must meet minimum tree density, height, damage and brush competition criteria as legislated by the Provincial government. Overall, 44 per cent of lodgepole pine trees had unacceptable damage (causing them to be rejected as crop trees), and as a direct result, one-third of the plantations were no longer defined as free growing because there were insufficient crop trees remaining. Natural regeneration of other tree species partially compensated for the unhealthy pine. Logistic regression and odds ratio analysis associated increasing risk of damage from western gall rust with increasing soil moisture, more northerly aspects and mechanical site preparation, and decreasing risk with pre-commercial thinning treatment. Risk of damage from snow and ice was associated with increasing mean annual precipitation, decreasing longitude and broadcast burning. Risk of bear damage was associated with increasing soil moisture, pre-commercial thinning treatment and broadcast burning. Based on our results, we recommend that single-species planting of lodgepole pine be curtailed in the Interior Cedar–Hemlock zone in southeastern British Columbia.

Description: Trees killed by natural disturbances have been recognized by the International Panel on Climate Change (IPCC) as a promising resource for bioenergy at the global scale. In the eastern boreal forest of Canada, there are two major types of natural disturbances that can generate large amounts of biomass for the production of bioenergy: wildfire and spruce budworm outbreak. For example, the mean burned area between 1970 and 2010 was estimated at 2900 km 2 per year. Following such disturbances, typically only trees and stands with a merchantable value, i.e., of acceptable quality for traditional forest products (lumber and pulp) are salvaged. However, adding bioenergy to the potential basket of products may both divert trees of marginal quality and profitability away from traditional products and to bioenergy facilities and lengthen the window of opportunity during which salvage operations can occur. This review shows how the dynamics of wood characteristics of trees affected by natural disturbances can be used to predict through time the basket of wood products that can be taken out of a salvaged stand and ensure the best fit between sources of fibre and types of processing facilities. The most important factors influencing fibre quality include degradation caused by fungi and insects. The most suitable time to salvage trees for the production of lumber in stands killed by either spruce budworm or fire is generally limited to 1–2 years after death. For the production of pulp and paper, trees can usually be salvaged for as long as the wood moisture content remains above the fibre saturation point, but usually is not recommended after 3 or 4 years following death. Thus, past this period, salvaged trees may yield better opportunities for the bioenergy sector. Information on wood as bioenergy feedstock (wood chips, wood pellets and liquid biofuel) highlights the importance of wood chemical components in the chemical reactivity of biofuel. This study offers background knowledge and a framework of analysis that highlights the potential of dead wood from natural disturbances for the production of forest and bioenergy products, which can be further adapted to other regions of the world, building on the Canadian experience of adapting practices to natural disturbances.

Description: We examined the effects of partial harvesting on the successional and structural development of forest stands relative to an unmanaged relict stand in Quercus -dominated forests in Indiana, USA over an 84-year period. Despite abundant ingrowth of shade-tolerant Acer and Ulmus species into the understorey of all stands, the double-harvest stand exhibited greater increases in richness, diversity and species mingling among strata relative to the relict stand. The release of mid-tolerant genera, Carya and Fraxinus , through overstorey disturbance, resulted in species composition more akin to earlier stages of stand development. Within the relict forest individuals from mid-tolerant species became more aggregated over time, but in the double-harvest stand they became less aggregated. Differences between stands were related to the degree of overstorey disturbance; from the relict, to the double-harvest stand, we observed consistent patterns among multiple measures. Retrogression of stand succession was evident based on stand structure over time and functional resilience to overstorey disturbance was reflected in mid-seral, mast-producing species composition. This study highlights the long-term influence of understorey vegetation on stand compositional and structural development, and the potential to achieve greater diversity in forest composition and structure in forest ecosystems prone to species homogenization due to lack of disturbance.

Description: Forest inventories (FIs) are increasingly supported by auxiliary variables ( X ) with a formulated link to a target variable ( Y ). The tenet forwarded here is that with simple single-stage sampling designs and a census of X , an analyst can choose between a model-assisted and a model-dependent finite population prediction approach to inference without the risk of important numerical differences in resulting estimates of interest. A small simulation study largely confirmed the tenet. A suite of FI-related issues regarding the two paradigms and their application in FIs are brought to the attention and discussed, hopefully triggering a more balanced reflections on the choice of inferential paradigm.

Description: The extent to which the presence of wood decay fungi in standing trees is underestimated when diagnosis is based on the visual inspection of trees was studied and whether the rate of underestimation may vary depending on the environmental context (urban vs. forest sites) and the fungal species was tested. A total of 903 broadleaf and conifer standing trees were inspected for the presence of fruiting bodies or other signs and sampled through a drill-based technique. Multiplex PCRs were used to analyse wood samples. Trees with emerging fruiting bodies ranged from 0 to 11.6 per cent depending on site. However, when analysed through molecular methods, the rate of infected trees was much higher, from 15.7 to 58.0 per cent. On average, visual inspection of trees underestimated 〉90 per cent of infected trees compared with molecular methods in both environmental contexts. Higher rates of underestimation were observed for Armillaria spp., Heterobasidion spp. and Phaeolus schweinitzii , whereas lower rates (〈80 per cent) for Ganoderma spp. and Perenniporia fraxinea . The range of variation of the underestimation rate was limited; therefore, a 90 per cent underestimate is a useful guide for judging the number of trees actually infected by wood decay fungi based on observations of the frequency of fruiting bodies and other signs.

Description: Results of nine replicated provenance trials of silver birch ( Betula pendula Roth) growing in Great Britain and Ireland are described. Five of the trials compare provenances from Scotland and the north of England measured after 10 or 11 years of growth; the remaining four trials compare provenances from across Great Britain, Ireland and the near-continent measured after 8 years of growth. In total, 64 provenances were tested. Survival was generally high across all sites with a mean of 79 per cent for the first five trials, and 89 per cent for the remaining four. The study found significant differences in mean height growth between trial sites and between provenances within each trial site. Although there was statistically significant site by provenance interaction, the better and poorer provenances were consistent across the range of sites tested. Mean height growth of the provenances under test was inversely correlated with latitude of origins, southern origins generally performing better. There was some evidence that further variation can be explained by incorporating details of longitude, accumulated temperature and potential moisture deficit for the origin. Elevation had little impact on explaining provenance performance. There was no evidence for the superior performance of provenances originating close to the trial site, other than for the southern-most trials. The relatively poor height growth of provenances from upland Scotland at even local trial sites suggests excessively conservative adaptation. The data suggest northern movement of provenances by at least 2 degrees latitude or 200 km would bring the benefits of improved height growth and yet carry little risk of poorer survival under current climate conditions and could perhaps be extended further according to predictions of future climate warming.

Description: Assessing forest cover change is a key issue for any national forest inventory. This was tested in two study areas in Switzerland on the basis of stereo airborne digital sensor (ADS) images and advanced digital surface model (DSM) generation techniques based on image point clouds. In the present study, an adaptive multi-scale approach to detect forest cover change with high spatial and temporal resolution was applied to two study areas in Switzerland. The challenge of this approach is to minimize DSM height uncertainties that may affect the accuracy of the forest cover change results. The approach consisted of two steps. In the first step, a ‘change index’ parameter indicated the overall change status at a coarser scale. The tendency towards change was indicated by derivative analysis of the normalized histograms of the difference between the two canopy height models (DCHMs) in different years. In the second step, detection of forest cover change at a refined scale was based on an automatic threshold and a moving window technique. Promising results were obtained and reveal that real forest cover changes can be distinguished from non-changes with a high degree of accuracy in managed mixed forests. Results had a lower accuracy for forests located on steep alpine terrain. A major benefit of the proposed method is that the magnitude of forest cover change of any specific region can be made available within a short time as often required by forest managers or policy-makers, especially after unexpected natural disturbances.

Description: Changes in climate trends and extreme climatic events are increasingly impacting on forests around the world. In order to better understand how and where major ecological and climatic changes will affect our forested ecosystems, tools based on landscape sensitivity analysis need to be developed to help inform sustainable forest management. This study was undertaken in the Northern Jarrah Forest (NJF) region in the Mediterranean climate of southwest Western Australia. Extreme drought and multiple heatwaves in 2010/2011 resulted in large-scale tree canopy dieback in the NJF. In this study, we used Landsat satellite imagery to (1) accurately map the damaged areas, (2) produce a damage probability model and (3) compare the model with a probability model derived from data collected through an airborne flight survey. We found that the Landsat-derived Normalized Difference Vegetation Index was a good indicator of drought/heat induced damage in the NJF region. Both probability models identified the same set of topography and climate-related factors for determining the probability of drought/heat damage within the landscape. Extrapolation of the Landsat satellite method-based model, however, produced a more deterministic and useful drought/heat damage sensitivity map for the NJF region. The techniques and tools developed, and applied, in this study can readily be transferred to other regions around the world and can assist in the sustainable management and timely climate adaptation efforts to accommodate our future forests.

Description: Taiwan incense-cedar ( Calocedrus formosana (Florin) Florin) and taiwania ( Taiwania cryptomerioides Hayata) are coniferous species growing in Taiwan, Republic of China. Both species are red listed, and hence, their management and conservation are important. The objective of this research was to determine the effect of climate on the height growth of Taiwan incense-cedar and taiwania. Height growth data for Taiwan incense-cedar came from stem analysis data and the data for taiwania were from three sets of experimental plots. Climate data were obtained from nearby climate stations. Dynamic height growth models having parameters that were functions of climate variables were fit to the height data. A Chapman–Richards function formed the basis for Taiwan incense-cedar model, and a linear model was fit to the taiwania data. Mean summer temperature and precipitation were predictor variables for Taiwan incense-cedar height growth. These variables, along with growing degree-days, were predictor variables for taiwania. Several scenarios were devised to show the effect of climate on height growth. Under the A1B climate change scenario, the height growth of taiwania is expected to increase, but the height growth of Taiwan incense-cedar will decrease slightly. The climate/height growth relationships can assist in the conservation and stewardship of these species.

Description: Large-scale transfer of reproductive material is a common phenomenon in forestry and is not only limited to recent history. Here we review the historical transfer of forest reproductive material (FRM) in Fennoscandia, the directions, their drivers, and the reported consequences for adaptation and gene pools of key forest tree species. We find that large imports of non-native FRM occurred from the 19th century onwards, partly due to prior deforestations directly associated with charcoal production for mining, extraction of timber and production of tar and pitch which have historically been important export commodities for Sweden, Norway, and Finland. In Denmark, conversion to agricultural land and the use of forests for livestock feeding was similarly important. During the subsequent reforestation efforts in Denmark, the introduction and use of non-autochthonous FRM of beech, oak and Scots pine became prevalent. Norway spruce FRM was extensively introduced to Sweden and Norway, and Scots pine FRM was imported to Sweden. Finland, in contrast, has limited records of FRM introductions. The importation of conifer seed to Norway and Sweden was initially driven by demand for large quantities of seed associated with the practice of direct seeding which prevailed until the mid-20th century. Large-scale changes to land ownership appear to have facilitated the logging of forests and subsequent seed imports for regeneration. Awareness of provenance variation in adaptive traits emerged gradually from the 19th century and led to more targeted imports of FRM to specifically improve climatic adaptation, trait qualities and growth, from the early 20th century. This, in turn, triggered the development of national regulations and guidelines from the 1930s to control the use of FRM, and marked a shift in forest legislation that had historically only been designed to control harvesting. Due to the geographical scales involved, transfers of FRM have unquestionably affected native gene pools, especially for species such as Norway spruce, Scots pine, beech, sessile and pedunculate oak, although relatively few examples of adaptive failures due to transfer have been reported.

Description: We demonstrate the efficacy of using close-range photogrammetry from a consumer grade camera as a tool in generating high-resolution, three-dimensional coloured point clouds for detailed analysis or monitoring of wheel ruts. Ground-based timber harvesting results in vehicle traffic on 12–70 per cent of the site, depending on the system used, with a variable probability of causing detrimental soil disturbance depending on climatic, hydrological and soil conditions at the time of harvest. Applying the technique described in this article can reduce the workload associated with the conventional manual measurement of wheel ruts, while providing a greatly enhanced source of information that can be used in analysing both physical and biological impact, or stored in a repository for later operation management or monitoring. Approaches for deriving and quantifying properties such as rut depths and soil displacement volumes are also presented. In evaluating the potential for widespread adoption of the method among forest or environmental managers, the study also presents the workflow and provides a comparison of the ease of use and quality of the results obtained from one commercial and two open source image processing software packages. Results from a case study showed no significant difference between packages on point cloud quality in terms of model distortion. Comparison of photogrammetric profiles against profiles measured manually resulted in root mean square errors of between 2.07 and 3.84 cm for five selected road profiles. Maximal wheel rut depth for three different models were 1.15, 0.99 and 1.01 m, and estimated rut volumes were 9.84, 9.10 and 9.09 m 3 , respectively, for 22.5 m long sections.

Description: To enhance the vigour and quality of high-graded hardwood stands, the removal of low-vigour trees is often prioritized during harvesting operations. However, northern red oak ( Quercus rubra L.) is rarely affected by defects that are indicative of imminent decline and, therefore, are less likely to be marked for harvesting. Consequently, the red oak volumes harvested during recent years were considerably lower than the estimated annual allowable cut in the public forests of Quebec, Canada. We used data from Quebec's forest inventory to identify variables associated with low-vigour red oak trees. Three groups of explanatory variables were formed to take into account tree size descriptors, inter-tree competition and stand descriptors. Logistic regression revealed that the probability of occurrence of northern red oak of low vigour increased with increasing tree diameter at breast height and dominance. Also, low-vigour oak trees were more likely to be found in stands in which total red oak basal area was low. A cut-point analysis indicated that the maximum diameter threshold for harvesting red oak ranged between 34 and 46 cm. These criteria could help forest managers formulate species-specific tree-marking rules that integrate the need to increase the red oak component in the harvested volume to a level that is closer to the annual allowable cut volume while maintaining stand vigour.

Description: Chronic browsing and inappropriate stand management are often discussed as causes for recruitment failure of tree species in temperate mixed uneven-aged forests. Continuous cover forestry is thought to produce conditions that are conducive to the recruitment of native shade-tolerant and browse-sensitive tree species such as silver fir ( Abies alba Mill.). This study used density-dependent matrix population models parameterized for three main types of fir forests in Europe (53 048 measured trees from 3183 permanent sample plots) to project the effects of Business-As-Usual uneven-aged management (BAU) and three alternative management scenarios (Non-Intervention (NON), Profit Maximization (MAX) and stand management optimized for increasing recruitment (CONS)) on fir population dynamics over 100 years. BAU, MAX and, particularly, CONS improved the population parameters if natural recruitment was sufficient regardless of site, current and historical logging and transient and equilibrium growth rates under NON. In chronically browsed and recruitment-limited fir populations with transient and equilibrium growth rates 〈1 under NON, the demographic ageing of fir can only be halted temporarily if silviculture is optimized for conservation, but none of the scenarios can prevent fir from decline. Our results suggest that a number of uneven-aged silvicultural systems, including more profit-oriented, can improve the demography of fir in central European mountain forests. However, they are not a pragmatic method to conserve fir when a population suffers from limited recruitment that causes an unmanaged population to decline.

Description: Tropical forests in Africa store large amounts of carbon and there is an urgent need for accurate methods to estimate this important carbon stock. One method to achieve this is by allometric equations but in many forest ecosystems in Africa these have not been developed. This study combined biomass data of 896 trees from five tropical countries in Africa and eight different sources to develop mixed-species regression equations for estimation of total biomass and height in Dry, Moist and Wet forest types. For estimation of total biomass, allometric equations combining diameter, height and wood density provided the best estimators in the three forest types. Because adding wood density to diameter improved height estimation, we recommend using allometric equations that combine diameter and wood density for height estimations in mixed and diverse tropical forests. Comparing ecosystem-specific (Dry, Moist and Wet) allometric equations to general allometric equations developed with combined data, and also to pan-tropical equations, showed that ecosystem-specific equations provided better estimators. The results highlight the importance of considering wood density in tree allometry for biomass as well as for tree height estimations. Although general allometric equations can be useful, this study recommends when they are available, the use of existing site-specific or ecosystem-specific allometric equations which provide better estimates.

Description: Little research has focussed on the use of low point density airborne laser scanning (ALS) technology in Mediterranean Aleppo pine ( Pinus halepensis Mill.) forest to derive key stand characteristics for forestry. The objective of this research was to develop models of Aleppo pine structural variables from ALS point clouds with a point density of 1 point m –2 and field information, in an area located in north-eastern Spain. Field stand metrics were obtained within 45 plots, 30 m in diameter. A multiple regression analysis was performed in order to develop the models for mean height, squared mean diameter, basal area, timber volume, stand density and crown ratio, which led to the following R 2 values: 0.87, 0.84, 0.89, 0.89, 0.48 and 0.69, respectively. ALS-derived metrics included in the models were maximum height, the 99th, 95th and 50th canopy height percentiles, the skewness, the kurtosis, the standard deviation, the coefficient of variation and the percentages of all and first returns from above 1 m of the ground surface. With the exception of stand density, the final models are appropriate to be used in forest management operations in Mediterranean Aleppo pine forest. This study demonstrates the usefulness of low point density ALS data to accurately estimate key structural parameters of Aleppo pine forest using an area-based approach.

Description: Compared with traditional inventory methods based on field plot sampling, airborne laser scanning (ALS) has the potential to assess forest structural properties with greater detail over space and time and at lower cost. Many national ALS survey programmes covering entire countries for topographic mapping are currently in progress and some have provided data that are in the public domain. Although the point density of these datasets is relatively low, there is an interest in developing methods that employ these types of data for categorizing different approaches to forest management. Using Finnish national ALS data with a point density of 0.91 pulses per square metre, we carried out a classification of 252 000 ha of boreal forests into silvicultural development classes (DC) used in practical forest management. Taking into account all eight DCs, the overall accuracy was 74.1 per cent and = 0.70. We conclude that the dataset is adequate for discriminating multilayered forests from even-aged ones. This result was compared with a method based on mathematical rules, which succeeded in discriminating multilayered stands with regeneration of shade-intolerant species without the need of field data for training. However, the low point density may hamper the detection of shade-tolerant understories in mature high forests with closed canopies. We, therefore, recommend the use of this supervised classification in the presence of shade-tolerant species.

Description: Improving management practices in industrial forest plantations may increase production efficiencies, thereby reducing pressures on native tropical forests for meeting global pulp needs. This study aims to predict stem volume ( V ) in plantations of fast-growing Eucalyptus hybrid clones located in southeast Brazil using field plot and airborne Light Detection and Ranging (LiDAR) data. Forest inventory attributes and LiDAR-derived metrics were calculated at 108 sample plots. The best LiDAR-based predictors of V were identified based on loadings calculated from a principal component analysis (PCA). After selecting these best predictors using PCA, we developed multiple regression models predicting V from selected LiDAR metrics. Metrics related to tree height and canopy depth were most effective for V prediction, with an overall model coefficient of determination (adj. R 2 ) of 0.87, and a root mean squared error (RMSE) of 27.60 m 3 ha –1 (i.e. relative RMSE = 9.99 per cent). We used this model to map stem V of Eucalyptus hybrid clones across the full LiDAR data extent. The accuracy and precision of our results show that LiDAR-derived V is appropriate for updating Eucalyptus forest base maps and registries in the paper and pulp supply chain. However, further studies are necessary to evaluate and compare the cost of acquisition and processing of LiDAR data against conventional V inventory in this system.

Description: We review the use of leaf area metrics (LAM) for assessing and managing dryland forests. We propose a framework integrating individual tree to whole-ecosystem metrics representing a variety of forest features and review theory, empirical evidence and knowledge gaps. Four basic concepts underlie the LAM framework: (1) Max-LAI – an ecosystem can be characterized by an upper potential leaf area index (LAI) dictated mainly by water availability, (2) Leaf area distribution – the distribution of leaf area is proportional to the distribution of resources among vegetation components, (3) Safe-LAI – maintaining Ecosystem-LAI below Max-LAI is a way to reduce drought stress and (4) tree leaf area ( TLA ) – the leaf area of an individual tree as a proportion of its potential TLA, represents its vigour. Implementation of the LAM strategy requires the following: (1) better understanding how edaphic conditions and vegetation characteristics interact with climate in determining Max-LAI , (2) better understanding how leaf area is related to water use across species, vegetation strata and light regimes, (3) better understanding the interaction between LAI development and stand dynamics, (4) better capability of measuring or estimating individual tree leaf area and (5) development of species-specific references for tree vigour based on leaf area. The LAM strategy is promising for managing dryland forests under increasing drought stress.

Description: To account for ecological objectives in forest management planning, potential habitats need to be mapped, characterized and evaluated for utility in alternative management practices. Airborne laser scanning (ALS) is increasingly used to derive predictive maps of habitat quality. Unlike ecologically driven approaches that require spatially and temporally co-located training data of the specific species, we tested whether indicative information on the habitat potential could be obtained by means of an unsupervised classification of ALS data. Based on a literature review, altogether five ALS features quantifying vegetation height, cover and diversity were expected to capture the essential variation in the habitat requirements of western capercaillie ( Tetrao urogallus L.) and hazel grouse ( Tetrastes bonasia L.), which are the most important game birds occurring in the studied area. The features were extracted from sparse density, leaf-off ALS data at a resolution of 256 m 2 and partitioned using an unsupervised k -means algorithm. By analysing the persistence of the cluster ensemble formed by the partitioning, altogether 158 plots in 16 structural classes were assigned for field measurements to determine which real-world forest phenomena affected the clustering. The clustering was found to stratify the area mainly in terms of size-related attributes such as timber volume and basal area. The understorey, shrub and herb layers had less correspondence with the clustering, indicating that an unsupervised classification is not directly suitable for habitat mapping. The result was improved using empirical threshold values for the ALS features determined according to the plots labelled as the most potential habitats in the field measurements. This semi-supervised classification of the data indicated 4 per cent of the total forest area as suitable for the specific species, which appears a reasonable estimate of the core area of the habitats considered. Overall, the partitioning formed aggregated, stand-like spatial patterns, even though the neighbourhoods of the individual 256 m 2 cells were not considered at all. The result could be further refined by spatial optimization to produce indicative maps for forest management planning with ALS as the sole data source.

Description: The oak wilt fungus, Ceratocystis fagacearum, is native to North America, and is a threat to oaks in Europe. Therefore, the European Union has regulated the importation of oak wood from the US into Europe. We developed a pathway model to calculate the exposure of oak trees in Europe to the fungus under different regulatory scenarios and thus evaluate the effectiveness of the measures. The model describes the import, inspection and treatments of wood, as well as the trade among European countries and processing to sawn wood, final product and residues. The model quantifies the frequency of escape of the fungus from wood with a vector, and the transfer to host trees. Existing regulations reduce exposure by a factor 〉30 000 compared with a scenario without regulation. Exposure is highest around European ports and during transportation of wood across Europe. Wood treatments and shipment to a restricted set of ports are effective measures, each reducing exposure by more than 90%. Pathway modelling is a promising tool to study entry pathways of alien tree pests and evaluate risk reduction options: it provides a systematic and transparent approach but is limited by availability of biological data.

Description: Alternative methods have been used for developing tree basic and generalized height–diameter models, including non-linear least-squares regression, non-linear mixed-effects method, quantile regression (QR) and a generalized additive model (GAM). However, these approaches have not been thoroughly compared. The purpose of this study was to compare these methods applied to tree height–diameter models for larch plantations in northern and northeastern China. The data were obtained from an extensive database curated by the China National Forest Inventory (NFI) that covers a wide distribution and range of stand conditions, including 5684 paired heights and diameters in 342 plots. Random effects at the Province, species and plot levels, and a combination of Province and species into the basic and generalized H – D models were incorporated. This study demonstrated that the mixed-effects basic model provided the best performance for model fitting and validation; QR could represent variable H–D relationships at different quantiles and the GAM was a suitable alternative for flexible modelling of the H–D relationship, especially for generalized H–D model. This finding indicates that the mixed-effects basic model does not require additional variables and is an adequate tool for generating missing height measurements for larch plantations in northern and northeastern China.

Description: Longitudinal or hierarchical data are often observed in forestry, which can pose both challenges and opportunities when performing statistical analyses. The current standard approach for analysing these types of data is mixed-effects models under the frequentist paradigm. Bayesian techniques have several advantages when compared with traditional approaches, but their use in forestry has been relatively limited. In this paper, we propose a Bayesian solution to non-linear mixed-effects models for longitudinal data in forestry. We demonstrate the Bayesian modelling process using individual tree height–age data for balsam fir ( Abies balsamea (L.)) collected from eastern Maine. Due to its frequent utilization in modelling dominant tree height growth over time, we choose to examine models based on the Chapman–Richards function. We established four different model formulations, each having varying subject-specific parameters, which we estimated using both frequentist and Bayesian approaches. We found the estimation results to be quite close between the two methods. In addition, an important feature of the Bayesian method is the unified manner in which estimation and prediction are handled. Specifically, local parameters can be predicted for a new dataset after setting the posterior distributions from the estimation stage as new priors in the prediction phase.

Description: This study compares the financial return of converting old-growth boreal stands into even-aged stands to that of two approaches of selection cutting in Quebec (Canada). In this region, old-growth stands are usually harvested by completely removing the canopy while protecting the abundant advance regeneration, an approach known as careful logging around advance growth (CLAAG). These approaches were compared using a time frame of over 200 years. Consideration is given to the majority of the operating costs leading to end products. The financial analysis integrates Monte Carlo simulations, making it possible to consider the uncertainty associated with variables. The net present values (NPVs) are then associated with a distribution of probabilities. The results show that the probabilities of obtaining positive NPVs are high for all treatments, suggesting that selection cutting approaches can be appropriate alternatives to CLAAG for some stands. Depending on the criteria used, the CLAAG cut or one of the selection cuts show the best performances. In fact, the results of the financial study show that in the future, selection cutting approaches will be more profitable than CLAAG but still less than present CLAAG operations. This occurs because, according to the current yield curves and rotation ages, future stands managed with CLAAG will have smaller and less valuable trees than in the primary forest and in stands managed with the selection system.

Description: There is a growing interest in the feasibility of establishing ‘Carbon’ forests where carbon sinks are created by maintaining forest stands out to considerable ages. In New Zealand, Pinus radiata (D. Don) is usually grown over 25- to 30-year rotations; the main aim of this paper is to examine the potential to maintain stands to 60 years or more. There were over 140 permanent sample plots in New Zealand that were maintained for at least 50 years. These data were examined to verify that growth can be sustained over this period. Net basal area per hectare and mean-top-height are graphically demonstrated to follow expected growth paths with no signs of senescence occurring. Stems per hectare loss is shown to be sometimes high, especially with dense stockings, but virtually all dying trees are small suppressed stems, so the impact on basal area yield at maturity is minimal. It is concluded that growing radiata pine on a rotation of 60 years is feasible, and it may be possible to use much longer rotations.

Description: The effects of site preparation practices (drainage, mounding and fertilization) on the fluxes from the soil surface of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) were studied on an organic-rich peaty gley soil at Harwood Forest, north-east England. Drained plots had significantly higher CO 2 fluxes but significantly lower CH 4 fluxes compared with undrained plots, while N 2 O emissions were not affected by drainage. Mounding caused significantly higher CH 4 emissions, while it significantly reduced N 2 O emissions. Fertilization caused significant increases in emissions of CO 2 , CH 4 and N 2 O. In terms of overall greenhouse warming potential, drainage and fertilization increased CO 2 -equivalent emissions by ~18–29 and 7–23 per cent, respectively, while mounding reduced CO 2 -equivalent emissions by ~8 per cent in year 1, but had no effect on emissions in year 2 of study. Soil temperature was the main environmental variable controlling CO 2 emissions, while CH 4 was controlled primarily by water table depth. Nitrous oxide emissions responded to changes in soil temperature and water table depth. In the short term, drainage and fertilization contributed to accelerating greenhouse gas emissions significantly, although their long-term effects are likely moderated by accelerating carbon accumulation in the tree biomass. Long-term studies are required to assess the cumulative impacts of site preparation practices during the whole rotation cycle.

Description: As signatories to the United Nation Framework Convention on Climate Change, the US has been estimating standing dead tree (SDT) carbon (C) stocks using a model based on live tree attributes. The USDA Forest Service began sampling SDTs nationwide in 1999. With comprehensive field data now available, the objective of this study was to compare field- and model-based estimates of SDT C stocks across the US to evaluate potential directions for improving National Greenhouse Gas Inventory (NGHGI) reporting and C dynamics research. Field inventory data indicated that most forests have relatively little SDT C stocks (〈1 Mg/ha), whereas large SDT C stocks (〉25 Mg/ha) are infrequent. Models used for past NGHGIs to predict SDT C stocks do not accurately reflect what was observed in inventory plots, resulting in an overestimation (~100 per cent) of SDT C stocks at the national scale. These results indicate that the current estimate of the Nation’s total forest C stock is overestimated by ~4.2 per cent due to overestimation of SDT C stocks that are a relatively small component of the total forest C stock. A field-based approach is suggested for use in future C reporting efforts to reduce estimation bias.

Description: Airborne laser scanning data and corresponding field data were acquired from boreal forests in Norway and Sweden, coniferous and broadleaved forests in Germany and tropical pulpwood plantations in Brazil. Treetop positions were extracted using six different algorithms developed in Finland, Germany, Norway and Sweden, and the accuracy of tree detection and height estimation was assessed. Furthermore, the weaknesses and strengths of the methods under different types of forest were analyzed. The results showed that forest structure strongly affected the performance of all algorithms. Particularly, the success of tree detection was found to be dependent on tree density and clustering. The differences in performance between methods were more pronounced for tree detection than for height estimation. The algorithms showed a slightly better performance in the conditions for which they were developed, while some could be adapted by different parameterization according to training with local data. The results of this study may help guiding the choice of method under different forest types and may be of great value for future refinement of the single-tree detection algorithms.

Description: Silvicultural systems which retain canopy cover during the regeneration phase have become an increasingly important form of management, but their effectiveness in controlling weed species has not been extensively studied. The development of bramble, which is a widespread competitive weed species, was observed within a c . 35-year-old Corsican pine stand thinned to remove 10, 20, 40 and 80 per cent of basal area. Cover, height and numbers of inflorescences and berries were recorded in each of the 3 years following thinning and were generally ranked according to intensity of thinning, but there were no significant differences between treatments. Shoot length, estimated using a grid-intersection method, was significantly lower in the 10 per cent compared with the 40 and 80 per cent thinning treatments. The initial length of bramble shoot present, and basal area and number of trees remaining could be used in various combinations to predict cover, height and shoot length. Although the bramble thicket was generally less well developed in the less-intense thinning treatments, these did not appear to enhance the establishment of trees. Seedlings grew best in the 80 per cent treatment and overall their mean heights were generally lower than that of bramble. Retention of overstorey cover in order to suppress bramble growth and promote tree seedling establishment during forest regeneration may not succeed.

Description: Three experiments were established in the 1990s to examine the impact of complete residue (brash) and above-ground biomass removal (i.e. ‘whole-tree harvesting’, WTH) at clearfelling on the subsequent growth and yield of replanted Sitka spruce ( Picea sitchensis ). The sites were of varying fertility; two would now be considered to be of ‘medium’ risk for brash removal, while one would be a ‘high’-risk site. The interactions between brash removal and regular remedial fertilizer applications and weed control regimes were also investigated at each site. After 10 years, trees had been successfully established at all sites, and in most cases, the treatments were close to canopy closure. The main effects observed at all sites were due to brash retention and fertilizer application. The benefits from the former were not evident until the last stages of the establishment period, whereas benefits from fertilizer application were evident once the trees had reached 5–6 years of age. The impacts of weed control were inconsistent, providing temporary benefits on the more fertile sites, and having a negative effect on the poorest site, primarily because the herbicide regime favoured the development of ericaceous vegetation which competed with the planted trees for nutrients. After 10 years at the two medium-risk sites, the difference in growth between plots with brash retained and those where brash was removed was 5–9 per cent for height growth and 5–7 per cent for diameter. However, at the poorest site, the equivalent differences were ~9 per cent and 19 per cent. The results show that the impact of brash removal due to WTH are significantly affected by site type and soil fertility and also that it may take nearly a decade before the impacts of such practices are evident.

Description: Policy makers, scientists and civil society are involved in the development of criteria and indicators for sustainable forest management (SFM), reflecting the growing worldwide demand for addressing sustainable development and environmental governance management goals. Such frameworks have been largely derived from expert-led or community-based approaches. This article details the identification process of criteria and indicators (C & I) based on the international principles of SFM through the analysis of a hybrid approach that uses both a top-down (TD) and a bottom-up (BU) approach. The aim of this article is to discuss how the two approaches have worked to incorporate the different views, opinions and experiences of experts and stakeholders. National-level C & I are then compared with those at the local level, making specific reference to sustainable community forest (CF) management. For the TD approach, a Delphi survey was conducted where 121 experts shared their knowledge, experience and judgements in assessing a set of 72 indicators with regard to the applicability, practicality and importance of national, regional and CF management in Nepal. For the BU approach, C & I for CF management were developed with the direct involvement of various stakeholders. It was shown that such a hybrid approach is feasible from a methodological point of view, but a framework is needed by the government to more fully utilize the opportunities of the C & I development process in the SFM context. The results of this study also help to bridge the gap between the ad hoc planning of decision makers and the requirement for a holistic management system, which includes participatory processes. Based on the conclusions of this study, general recommendations for the methodological design of C & I development in similar studies are given.

Description: Drought acclimation in woody plants tends to be associated with the development of denser vascular tissue. As wood density may be correlated with the mechanical properties of the tissue, we hypothesized that seedlings subjected to drought would develop stems that had a higher density as well as stiffer and stronger tissue. We tested our hypothesis on establishing trees of the species Betula pendula , Acacia karroo and Ochoma pyramidale . The seedlings were grown for 1 year under well-watered as compared with cyclically droughted conditions. The modulus of elasticity in bending, yield stress, density and pith- and bark fractions of the stems at different heights were measured. In all three species, individuals grown under drought conditions had on average stiffer and stronger stems than the well-watered individuals, though non-significantly so in A. karroo . These differences were associated with a higher density in O. Pyramidale but not in the other species. In B. pendula , the differences in mechanical properties appear to be associated with other factors, e.g. modifications of the micro fibril angle in the S2 cell wall layer. Our results indicate that drought acclimation in seedlings affects the mechanical properties of the stem but that the causal acclimational processes may vary between species.

Description: Multi-aged stands in a mixed conifer forest of California were treated to mitigate harvest-related increases in surface fuels and to prepare sites for natural regeneration of Pinus species. The study was designed to (1) assess effectiveness of small gap fuel treatments (piling and burning in 0.04 ha gaps) on surface fuel and modelled fire behaviour; (2) test the effect of substrate quality on germination of Pinus species; (3) measure the influence of gap creation on light availability and stand-level light heterogeneity. While the fuel treatment only covered 10 per cent of stand area, it was effective in avoiding increases in stand-level surface fuel following harvests. Fire behaviour was predicted to be moderate following the treatments. The harvest coupled with the gap surface fuel treatments did not change predicted fire behaviour compared with the pretreatment stands. There was a significant but variable increase in germination of Pinus ponderosa seed when sowed on ash substrates compared with bare soil. No substrate effect was detected for Pinus lambertiana . The 0.04-ha gaps created distinct pockets of light and greatly increased stand-level light heterogeneity. This gap-based approach to regenerating multi-aged stands coupled with small-scale fuel treatments is promising for reducing fire hazard and regenerating shade-intolerant species.

Description: A broad-scale analysis of the structure and understory composition of Pyrenean mountain pine ( Pinus uncinata Ram.) stands was performed using data from the Spanish National Forest Inventory. Twelve structure-based forest typologies were defined from variables related to tree size, stand density, vertical structure and standing deadwood, using cluster analysis techniques. These typologies were adequately classified (accuracy 〉75 per cent) by a dichotomous key obtained from classification and regression trees. Multiple regression models were then used to analyse relationships between the main stand structural variables and a set of climatic and physiographic factors. The models showed significant correlations between winter temperature, slope and continentality (among other variables) and the current structure of mountain pine stands. The relationships between the understory composition of mountain pine forests and different environmental and structural overstory factors were found to be driven by an elevation-pH gradient and a stand density-soil stoniness gradient. The results of this study can be directly used for forest planning at different scales and could help forest managers to establish strategies designed to facilitate a given habitat for species of conservation interest.

Description: Increasing accumulation of CO 2 in the atmosphere has led to calls for terrestrial mechanisms for CO 2 abatement and given that soils represent the largest terrestrial body of C on Earth, there is a great deal of interest in soils as a sink for atmospheric C. This emphasis on sequestration in boreal forest soils is understandable given the sheer mass of this C reservoir (~1700 Pg of C) but diverts our attention from the importance of soil C in soil physical, chemical and biotic functions, and importantly, it ignores the possibility that soils may also represent a source of C. In this review, we address these issues through a discussion of the size and character of boreal forest soil C pool, its role in ecosystem function, the potential impacts of climate change on soil C, efforts to model these processes and the role of soil C in boreal resilience to the impacts of climate change. Soil C is fundamental to ecosystem function in terms of improving soil physical properties, increasing soil biotic activity and enhancing insulation all of which improve site productivity. Managing upland soils for C sequesteration will achieve little in terms of offsetting fossil fuel emissions but would likely improve soil quality. Most of the C stored in the boreal biome is found in permafrost and wetland soils and events related to climatic change could shift these soils from C sink to C source. Melting of permafrost soils with predicted warming trends within the circumpolar region could result in the release of 30–60 Pg C by the year 2040. Such predictions, however, are limited by uncertainty in both climatic changes and soil response to these changes. Prediction of shifts in soil C dynamics with climate change relies on our ability to link C transformations to N dynamics and climatic variables. Improvement in ecosystem models will advance our ability to assess the resilience of the boreal biome under future climatic conditions.

Description: Bioclimate models incorporating topographic predictors as surrogates for microclimate effects are developed for Populus tremuloides and Picea engelmannii to provide the fine-grained specificity to local terrain required for adapting management of three Colorado (USA) national forests (1.28 million ha) and their periphery to climate change. Models were built with the Random Forests classification tree using presence–absence observations obtained by overlaying species distribution maps on data points gridded at ~225 m within the forests and from ground plot observations from adjacent areas. Topographic effects derived from 90-m elevation grids were expressed by weighting aspect by slope angle. Climate estimates were obtained from spline surfaces. Out-of-bag errors were ~17 per cent, and classification errors for an independent sample from within the forest were ~13 per cent. Topographic variables were second in importance to climate variables for predicting species distributions; their inclusion captured well-known topographic effects on vegetation in mountainous terrain. Predictions made for future climates described by three General Circulation Models and three emissions scenarios were used to map on 90-m grids the habitat expected to be lost, threatened, persistent or emergent. The habitat categories are used to identify those areas where treatments should have highest likelihood of success.

Description: The high richness of epiphytes in moist tropical montane forests is continuously decreasing due to deforestation and habitat loss. Lichens and bryophytes are important components of epiphyte diversity on trunk bases and play an important role in the water balance and nutrient cycling of tropical montane forests. As lichens and bryophytes are very sensitive to microclimatic changes, we hypothesized that their species richness and composition would change with forest alteration. We also expected their response patterns to be different given the capability of lichens to photosynthesize using water vapour. In this study, we assessed the richness and composition of epiphytes (lichens and bryophytes) on the trunk bases of 240 trees in primary and secondary forests of southern Ecuador. We found that diversity was higher in primary forests and lower in monospecific secondary forest stands. Total diversity was negatively affected by habitat loss and by the reduction of canopy cover for bryophytes. Shade epiphytes were replaced by sun epiphytes in open secondary forests. We conclude that lichen and bryophyte diversity of tropical montane forests are negatively affected by the removal of large trees and canopy disruption. The different species compositions of primary and secondary forests and the high number of species exclusive to primary forests indicate that secondary forests are of limited importance in compensating for the loss of non-vascular epiphyte species associated with primary forests.

Description: Research on the early stages of stand dynamics in uneven-aged forests often favours regeneration over recruitment of trees into forest stands. We contrasted both regeneration (i.e. seedlings and saplings existing in a stand) and recruitment (i.e. the number of trees annually crossing the threshold of 10 cm dbh) in two main stand types of uneven-aged forests (plenter and group selection). Data from 1710 permanent plots across the Dinaric Mountains in Slovenia were used to study recruitment; on 165 plots, regeneration was additionally analysed. The zero-inflated negative binomial modelling procedure was applied to identify factors influencing regeneration and recruitment. Total regeneration (30 212 ha –1 ) and that of light-demanding species (14 879 ha –1 ) were abundant. The latter regenerated more successfully in group selection stands compared with plenter stands. A large reduction in regeneration density was determined during its growth, which was more dramatic for light-demanding species (e.g. Acer pseudoplatanus ) than for shade-tolerant species (e.g. Fagus sylvatica , Abies alba ). The number of recruited trees (5.83 ha –1 y –1 ) seemed to be sufficient to maintain the uneven structure but was less promising for light-demanding species (0.13 ha –1 y –1 ). However, light-demanding species have the potential to establish and recruit into uneven-aged stands with a limited target proportion in the growing stock. Both indicators—regeneration and recruitment—are indispensable for understanding patterns of stand dynamics in uneven-aged forests.

Description: In this work, it was studied the need to adapt the choice of main Finnish boreal tree species in forest regeneration under the projected climate change. The forest ecosystem model (SIMA) was used to simulate the volume growth of young Norway spruce, Scots pine and silver birch stands under the current and gradually changing climate throughout Finland on sites with fertility varying from low to high. Compared with the current climate, the growth of Scots pine and silver birch increased under the changing climate throughout Finland. The increase was the highest on fertile sites under the SRES A2 climate change scenario. The growth of Norway spruce decreased in southern and central Finland under the SRES A1B and A2 climate change scenarios compared with the current climate, and especially on sites with low fertility. In northern Finland, the growth of Norway spruce was clearly higher under the changing climate similar to Scots pine and silver birch, regardless of site fertility and time span. Overall, the growth responses of different tree species differed from each other largely depending on the geographical location and climate change scenario applied. Based on this work, we may need to adapt the choice of main Finnish boreal tree species in forest regeneration under the changing climate, to consider the uncertainties related to the projected climate change in different time spans.

Description: In felled-tree studies, ratio and regression estimators are commonly used to convert more readily measured branch characteristics to dry crown mass estimates. In some cases, data from multiple trees are pooled to form these estimates. This research evaluates the utility of both tactics in the estimation of crown biomass following randomized branch sampling (RBS). Synthetic generalized regression (GREG) estimators are developed, and their properties examined against standard estimators. It is shown that synthetic GREG estimators with zero or low design-bias can be obtained, and that the variance of a design-unbiased class of GREG estimators can be unbiasedly estimated. Simulated sampling from 20 censused crowns of two Rocky Mountain species indicated that improvements in accuracy can be obtained through GREG estimation following RBS. Simulations also showed that synthetic GREG estimators that pool data from multiple trees can stabilize coefficients of multivariate regression models to provide improved accuracy over direct GREG estimators. However, for the univariate regression models that proved most adept for the censused crowns, direct GREG estimation provided the lowest average root mean squared error (RMSE) for RBS. Simulations also showed that model-based branch aggregation estimators have generally low RMSE but can be heavily design-biased. For the crown forms studied, use of branch auxiliary information at both the design and estimation stages through RBS and GREG estimation appears to be more efficient than using the information only at the estimation stage following simple or stratified random sampling.

Description: Differences between intra- and inter-specific competition strategies in mixed stands account for higher productivity. The mechanisms of competition as they relate to stand structure remain poorly explored. Climatic effects have also been overlooked in most approaches aimed at studying tree growth. These effects were investigated through the case study of beech-oak mixtures in France. A single-tree diameter-increment mixed model was fitted to data gathered from the Laboratoire d'Etude des Ressources Forêt-Bois (LERFoB) network of permanent plots. In order to take stand structure into account, the model was able to distinguish between inter- and intra-specific competition at tree level. Differences in intra- and inter-specific competition are mainly detected in the understorey of oak-dominated stands, where suppressed beech trees performed better than suppressed oak trees. From a climatic point of view, diameter increment was sensitive to the mean temperature of the vegetative period. Concerning competition, our results demonstrate that optimal growth induced by mixtures is not only a matter of species proportion but also depends on stand structure. Regarding climatic effects, they need to be considered in growth predictions, especially given the future climatic conditions predicted for continental Europe. These findings could serve as guidelines for designing strategies to alleviate stress in oak-beech stands.

Description: The genus Bursaphelenchus contains more than 100 species of nematodes. Knowledge of the occurrence of nematodes belonging to this genus is a prerequisite for monitoring issues and control measures to prevent the introduction and establishment of pathogenic species such as Bursaphelenchus xylophilus into forest ecosystems. According to data collected from the published literature and databases such as Web of Science, FSTA, CAB Abstracts, Biological Abstracts and the EPPO Reporting Service, 22 Bursaphelenchus species have been recorded to be present in the Mediterranean region. These species are classified into nine morphological groups sensu Braasch, H., Burgermeister, W. and Gu, J. 2009 Revised intra-generic grouping of Bursaphelenchus Fuchs, 1937 (Nematoda: Aphelenchoididae). J. Nematode Morphol. Syst . 12, 65–88): abietinus , eggersi , eremus , fungivorus , hofmanni , kevini, leoni , sexdentati and xylophilus , although two species are currently not assigned to a specific group . Movement of insect vectors in international trade of wood and host plants into and within Mediterranean areas is considered the main pathway for Bursaphelenchus species dispersal. Many of the species represent a significant risk for pine and possibly other forest types, an annotated check-list of Bursaphelenchus species in the Mediterranean area, their main features, pathogenicity, host plants and insect vectors is presented.

Description: To meet the demand for timber consumption, large areas of broadleaved secondary forests have been replaced by larch ( Larix spp.) plantations in Northeast China. However, larch plantations face some serious problems, including soil fertility decline, acidification of surface runoff and low levels of biodiversity. Converting pure larch plantations into mixed larch-broadleaved forests would offer a potential solution to some of these issues. Two dominant broadleaved tree species of secondary forests (i.e. Juglans mandshurica and Fraxinus mandshurica ), which have been successfully mixed with larch previously, were seeded in thinned pure larch stands to confirm the feasibility of converting even-aged pure larch plantation stands into uneven-aged mixed larch-broadleaved forests. Larch stands were treated with 100, 50 and 25 per cent thinning intensities to evaluate the effects of thinning on the persistence of seeds in two burial positions (under litter and in soil) and at two burial times (6 and 12 months), and on the seed germination at five burial positions (on top of litter, on top of soil, between litter and soil, in soil and in soil with litter coverage). We found that after 1-year burial, J. mandshurica and F. mandshurica seeds had a viability rate of 82 and 10 per cent, respectively. Most seeds remained viable at 25 per cent (91 per cent for J. mandshurica , 27 per cent for F. mandshurica ) and 50 per cent (90 per cent for J. mandshurica , 23 per cent for F. mandshurica ) thinning treatments. Seeds of J. mandshurica and F. mandshurica buried in soil with litter cover (21, 38 per cent) and in 50 per cent thinning treatments (16, 35 per cent) of larch plantation forests had significantly higher seed germination/seedling survival rate, compared with other burial positions and thinning treatments. Regeneration results (seed persistence, seed germination and seedling survival) suggest that artificially converting larch plantations into larch-broadleaved mixed forests by thinning and adding seed sources of native broadleaved species is a potentially feasible practice. These results also provide new insights into the tending measures used in pure plantation management.

Description: Microsatellite markers were used to describe the genetic structure of a natural wild cherry ( Prunus avium L.) stand in Slovenia. Based on eight analyzed loci, only 67 different multilocus genotypes (MLGs) were identified among 217 trees, indicating a significant amount of clonal reproduction in the stand. Low spatial genetic structure (SGS) was observed in the stand when only sexually derived genets were considered ( Sp = 0.011), and the kinship coefficient was only significant in the first distance class (〈40 m). When both the generative and vegetative origin of trees were included, the intensity of the SGS in the stand increased ( Sp = 0.149). Forest paths, streams and ditches, which represent obstacles to root growth and consequently obstruct vegetative propagation via root suckers, also affected the spatial grouping of clones in the stand. A relatively high number of somatic mutations within clonal groups were observed, which further increased the complexity of the genetic structure in the stand.

Description: The causes of the decline of silver fir across Europe in the 1960s and 1970s and its subsequent recovery remain open to debate. We studied the radial growth of silver fir and possible influential factors on growth decline in uneven-aged silver fir–Norway spruce–European beech forests in the Dinaric Mountains of Croatia (180 000 ha) since 1900 using dendrochronological methods. Data on the radial growth of large firs (diameter at breast height 〉 50 cm) sampled in 2002 across the region (151 plots, 491 m 2 each), regional climatic data (temperature, precipitation and drought) and SO 2 emissions were used in both statistical and dynamic factor analyses. Two main growth patterns of fir trees were identified: the first features a sharp decline in radial growth in the period 1966–1983, followed by a dramatic recovery, while the second is characterized by a relatively constant increase in radial growth. The most influential climatic factors were mean monthly temperatures in February, July and August; mean precipitation in May and September; and summer drought. However, SO 2 emissions explained a larger part of the total variability of radial growth than climatic factors (46–60 per cent and 0–42 per cent, respectively). The growth recovery of silver fir supports further application of uneven-aged silviculture in the region.

Description: Model-based prediction of annual ring density (RD) is necessary to manage forests for wood quality objectives. However, annual RD in lodgepole pine ( Pinus contorta Dougl. ex Loud.) exhibits a high degree of variability making it a challenge to model. We compared two methods of predicting annual RD including (1) a ring component approach and (2) a direct approach. The former approach uses model-based estimates of earlywood density (EWD), latewood density (LWD) and latewood proportion (LWP) to calculate annual RD. The latter approach uses a single model with annual RD as the dependent variable. The two approaches were tested using a dataset which included sites on the western and eastern slopes of the Rocky Mountains, within the provinces of British Columbia and Alberta, Canada. The best models for EWD, LWD and LWP included ring number and ring width, while site-specific parameters indicated that sites on the western slopes differed from those on the eastern slopes. Component-based estimates of annual RD using only fixed effects explained 25 per cent of the variability, increasing to 63 per cent with random effects. The best model for a direct estimate of annual RD explained only 5 per cent of the variability using fixed effects, increasing to 55 per cent with random effects.

Description: There is little information about the impacts of past Sitka spruce ( Picea sitchensis [Bong.] Carr.) tree breeding on wood properties because the emphasis has traditionally been on improving stem form and growth rates. This study used both SilviScan and mechanical testing to investigate the radial variations in wood stiffness, bending strength, density and microfibril angle in defect-free samples taken from the first United Kingdom progeny trial to reach merchantable size. We tested for differences in these radial patterns of variation in half-sibling progeny of three plus trees originally selected for superior growth rate and stem form against a non-selected control. Large differences in all of the properties were observed with radial position, with properties generally being less desirable in the corewood. Significant undesirable differences between the improved families and the control were found for stiffness, strength and microfibril angle. There was no significant relationship between wood density and stiffness in samples taken from the inner part of the tree, where stiffness was more closely associated with microfibril angle. Overall, previous selections for growth rate and/or stem form have compromised timber properties. It is recommended that current breeding programmes focus on corewood stiffness to prevent further degradation in the wood properties of the future timber supply.

Description: To predict the value of trade between countries, a differential gravity model of bilateral trade flows was formulated and estimated with panel data from 2005 to 2014 for each of the commodity groups HS44 (wood and articles of wood), HS47 (pulp of wood, fibrous cellulosic material) and HS48 (paper and paperboard). The parameters were estimated with a large database by ordinary least squares, fixed-effects and random-effects methods. For the three commodity groups, the results were stable across methods. For HS44, exports were inelastic (0.33 ± 0.19) with respect to the gross domestic product (GDP) of exporters and elastic (1.95 ± 0.15) with the GDP of importers. For HS47, exports were elastic with respect to the exporters GDP (1.67 ± 0.55) and importers GDP (1.10 ± 0.36). Exports of HS48 were inelastic with the exporters GDP (0.81 ± 0.21) and elastic with respect to the importers (1.00 ± 0.14). For all three products, there were marked decreases in exports in 2009 and 2012 independent of GDP. The estimated elasticities were used to predict the growth rate of trade flows from 2015 to 2020 based on exogenous GDP projections of the International Monetary Fund. Another application investigated the effects of the Trans-Pacific Partnership agreement on the trade of forest products between the 12 member countries.

Description: National forest inventories (NFIs) have to be properly designed in order to yield statistically representative data and make best use of limited resources. A key element to accomplish this is the knowledge of the local variability in the sampled forest stand features. In this study, we estimated the variability of tree taxonomic richness and carbon (C) stock in logged-over and unlogged lowland tropical forests of Papua New Guinea, to define the optimal plot and sample size needed to estimate these characteristics in the context of the forthcoming implementation of the new NFI. We used data from 133 one-hectare permanent sample plots to calculate the coefficient of variation (CV) of C stock and taxonomic richness at different simulated plot sizes. CV was seen to rapidly decrease with increasing plot size up to 0.2–0.3 ha for both features following an inverse-exponential trend. Optimum plot size ranged between 0.08 and 0.32 ha, with 75–164 plots needed to achieve an estimation within 5 per cent of the true mean (95 per cent confidence), depending on the stand feature and the previous silvicultural treatment. We concluded that the establishment of a network of 319 permanent sample plots between 0.2 and 0.3 ha in size would represent an efficient sampling scheme in lowland forests for the new NFI.

Description: The objective of this study was to compare the utility of combinations of data from airborne laser scanning (ALS), RapidEye satellite imagery and auxiliary environmental data to predict stand structure in a plantation forest. Both parametric and non-parametric modelling techniques that could simultaneously predict a multivariate response were employed and found to produce predictions with similar levels of accuracy. Response variables were derived from 463 field measurement plots that were used during model development; a further 60 randomly selected plots were set aside for validation of model performance. Candidate predictor variables were extracted from the ALS data, satellite data and auxiliary environmental data, and the variables with the greatest explanatory power were used to create six separate models based on combinations of the data sources. Model validation showed that models using RapidEye data only were the least precise and that adding auxiliary environmental data only led to a moderate improvement in model precision. The model precision observed was similar to those reported previously from studies using satellite data to predict stand structure. Models developed using data from ALS were by far the most precise and adding information from satellite data or auxiliary environmental data led to negligible improvement in the prediction of stand structure. Although the outputs of both model types were similar, the practical efficiencies of using the non-parametric approach make it appealing to meet the demands of managers of industrial plantation forest managers.

Description: The inclusion of quadratic mean diameter (QMD) and relative spacing index (RSI) substantially improved the predictive capacity of height–diameter at breast height (d.b.h.) and crown ratio models (CR), respectively. Data were obtained from 208 permanent plots established in western Arkansas and eastern Oklahoma during 1985–1987 and remeasured for the sixth time (2012–2014). Existing height–d.b.h. and CR estimation models for naturally occurring shortleaf pine forests ( Pinus echinata Mill.) were updated and modified for improved performance. Additionally, eight height–d.b.h. relationship models that use only d.b.h. (fundamental local models) were modified using covariates. The model performance was evaluated using fit statistics [root mean square error (RMSE), Fit index and Akaike information criteria (AIC)]. The results showed that the best model form which was an extended non-linear model with autoregressive first order AR (1) structure and power variance function performed better than extended mixed-effects models and predicted well as an ordinary least squares non-linear model. The autocorrelation within individual trees was larger for the height–d.b.h. relationship than for CR estimation. The addition of QMD to mean dominant height ( H D ) greatly improved height–d.b.h. relationship with a reduction of 8 per cent in RMSE, compared with the use of basal area per hectare . Similarly, multiplying a fundamental local model by using QMD raised to a parametric power reduced RMSE by 16 per cent, improved Fit index by 12 per cent and decreased the AIC value by 7 per cent. D.b.h., H D and RSI best explained the crown ratio relationship with an improved Fit index by 6.7 per cent compared with alternative non-linear models without RSI. The logistic model for CR also provided prediction accuracy similar to that of a commonly used non-linear model. A non-linear model with an application of remedial measures to enhance adherence to modelling assumptions can provide better parameter estimates than mixed-effects modelling approach.

Description: Dendrolimus pini L. is a common and widespread moth in Europe, where severe outbreaks can defoliate Pinus sylvestris L. stands. Outbreaks are thought to be climate driven and may become more frequent and widespread with climate warming. The recent discovery of breeding populations of the moth in P. sylvestris plantations in Scotland has highlighted the importance of predicting outbreaks both within the core areas and at the margins of its current range. In this investigation, we used published data of damaging outbreaks plus historical climate data from Germany to build a relationship between climate conditions and outbreaks, and to develop a prediction model. Our analytical approach used principal component analysis and decision-tree data mining. German historical outbreaks showed relationships with climate variables, and provided evidence for a new damaging outbreak prediction model. The model uses the Seljaninov hydrothermal coefficient and decision-tree models on climate observations to predict where and when outbreaks may occur. The model was applied to European observed climate data and two climate projections using a GIS. In Europe, the model predicted future outbreaks in the Baltic States, Scandinavia, Russia and Scotland. In Scotland, more detailed analysis with probabilistic climate change projections showed an increasing risk of outbreaks through the twenty-first century.

Description: Norway spruce ( Picea abies (L.) Karst.) understory seedlings, growing in partially harvested plots with different canopy cover in a boreal spruce stand, were spot fertilized (Hydro 15-4-12) 9 years after planting. The principal aim was to test the hypothesis that nitrogen (N) availability influences growth of understory seedlings at intermediate but not at low levels of irradiance. In addition, we tested the combined influences of N and light availability on selected morphological and phenological traits, covering a 2-year period after treatment. Diffuse radiation (DIFR) at the seedling level was estimated from hemispherical photographs and ranged from 19 to 46 per cent of DIFR in open conditions. Fertilizer application was associated with a marked increase in foliar N concentration. The fertilized seedlings grew better in height and root collar diameter compared with unfertilized controls. While the absolute growth in both diameter and height increased with increasing DIFR, seedlings also responded to improved nutrient availability across the range of light conditions studied. Fertilizer treatment did not affect the number of nodal buds, but we observed a higher apical dominance ratio and advanced bud burst in fertilized seedlings. In conclusion, nutrient availability influenced growth and bud phenology of understory Norway spruce seedlings at least down to 20 per cent DIFR.

Description: The structural attributes of an old-growth forest remnant of Pinus nigra subsp. salzmannii located in southern Spain and those from nearby managed forests were compared. Data on environmental and structural variables were collected in 74 forest inventory plots. Significant differences were tested by means of the Mann–Whitney U -test. A partial redundancy analysis was conducted to assess the relative contribution of both environmental and management variables in explaining differences in the current structure of old-growth and managed stands. Additionally, 25 trees of different size (range 25.4–98 cm) and age (67–803 years) were cored and dendrochronological methods and bootstrap linear regression were used to study the effects of size and age on tree growth. The old-growth stand exhibited a higher density of large trees (diameter at breast height 〉50 cm) and greater variability in tree size than managed stands, but lower tree density and, consequently, similar values of stand basal area and volume. Environmental variables accounted for 5.7 per cent of the total variance observed in structural attributes, while the contrasting silvicultural condition (old-growth vs managed) accounted for 10.2 per cent. Growth, measured in units of stand basal area, increased continuously with tree size.

Description: While there is considerable interest in transforming even-aged stands into species-diverse, irregular structures, the rarity of stands close to the end of the transformation process has resulted in a lack of knowledge on optimum target structures that are considered sustainable. This study examined this problem in a mixed-species selection stand that has undergone transformation for over 60 years. Complete inventories of a one-hectare permanent sample plot were carried out in 2015 and previously in 2009, 2003 and 1997. The diameter distribution remained relatively static with the q factor remaining at 1.4 since the 2009 inventory. An improvement in the number of regenerating seedlings and saplings available for recruitment from previous inventories suggests that the current structure is relatively stable although shade-tolerating conifers are gradually dominating the stand. Not all the sustainability criteria were met; however, the stand could be described as having reached a balanced condition. It is recommended that the current stocking density and basal area (~350 stems ha –1 and 26–27 m 2 ha –1 , respectively) should be maintained and that future harvesting interventions should aim to reduce the number of large diameter stems (〉55 cm DBH), which represent 14 per cent of the stocking but 48 per cent of the stand basal area.

Description: Sustainable methods are required to protect newly planted tree seedlings from insect herbivore attack. To this end, here Norway spruce ( Picea abies (L.) Karst.) seeds were treated with 2.5 mM nicotinamide (NIC), 2.5 mM nicotinic acid (NIA), 3 mM jasmonic acid (JA) or 0.2 mM 5-azacytidine (5-Aza), and 6-month-old seedlings grown from these seeds were planted at a reforestation area in central Sweden. Attack by pine weevils ( Hylobius abietis ) was reduced by 50 per cent by NIC treatment, 62.5 per cent by JA treatment and 25 per cent by 5-Aza treatment, when compared with seedlings grown from untreated seeds. Watering 18-month-old spruce seedlings with 2 mM NIC or 2 mM NIA did reduce attack during the first season in the field by 40 and 53 per cent, respectively, compared with untreated plants. Girdling was also reduced by the different treatments. Analysis of conifer seedlings treated with 5-Aza points at a possible involvement of epigenetic mechanisms in this defensive capacity. This is supported by a reduced level of DNA methylation in the needles of young spruce seedlings grown in a greenhouse from NIC-treated seeds. Seed treatment for seedling defense potentiation is simple, inexpensive and also a new approach for forestry with many potential applications.

Description: Megaplatypus mutatus (syn. Platypus sulcatus ) is an ambrosia beetle native to South America, which represents the main forest pest in Argentina of Poplar plantations and is also an emerging pest in Europe, representing a potential risk to forest and fruit plantations globally due to its low specificity. Knowledge of the interactions this insect has with microbes will be important in understanding its impacts and management. In this study, we characterized the fungal diversity associated with M. mutatus in Populus trees in Argentina. The fungal community of 28 attacked trees was studied by evaluating 1104 gallery fragments and 110 fragments of insects. Fungal isolates were identified using morphology and phylogenetic analysis of the internal transcribed spacer region of nDNA. Nineteen taxa were identified, the most relevant Fusarium solani species complex, three species of Raffaelea and Graphium basitruncatum . Despite the lower frequency occurred by Raffaelea spp. and G. basitruncatum , we detected a specificity between male/female and location in the gallery. Additionally, the topology of the galleries is described based on analyses with computed tomography and nuclear magnetic resonance. Enhancing these techniques, an image combining both data was produced, suggesting that the water circulation across outer sections might be involved in the modulation of the gallery topology.

Description: We studied biophysical (biotic and abiotic) factors correlating with dominant height and basal area (BA) development within 110 ha of evergreen mixed conifer forest dominated by coast redwood ( Sequoia sempervirens (D. Don) Endl.) in north coastal California. Various descriptors of species composition, topography, soil properties and moisture, light and harvest disturbance were assessed in a grid of 234 permanent sample plots. Within the study area characterized by heterogeneous topography and variable species composition, site descriptors alone were poor predictors of stand volume production in multiple linear regressions. Multivariate canonical correlation analysis revealed that redwood height growth was related to a different suite of biophysical variables than BA growth. Greater stand volume production was measured in areas with less hardwood, more Douglas-fir ( Pseudotsuga menziesii var. menziesii (Mirbel) Franco), higher soil pH and at lower slope positions. Sheltered lower slopes were more amenable to redwood height growth. Exposed upper slopes and ridges receiving more light favoured BA over height growth in redwood. Our analysis provides a framework for refining estimates of forest growth, yield and carbon stocks in natural forests in accordance with divergent dimensions of productivity and allied biophysical gradients.

Description: This study analyzed differences between actual and modelled fire predictions for two recent fires that affected the Golestan National Park in northeastern Iran. FARSITE and FlamMap minimum travel time (MTT) fire modelling systems were used to compare spatial differences in burned area between observed and modelled fires. Then, the spatial variability in fire spread and behaviour related to differences in fuel types and topography was analyzed. Comparison between the observed and simulated fire perimeters showed a relatively good agreement. For both case studies, the simulations performed with the MTT algorithm presented slightly higher accuracy than the FARSITE ones. Although we found spatial differences in fire intensity and rate of spread modelling outputs, the average values in burned areas provided by FARSITE and FlamMap MTT simulations were very similar. The comparison of fire spread models provided a better understanding of their potential limits and differences in fire growth and behaviour predictions over heterogeneous-fuel landscapes, complex topography and changing weather conditions.

Description: Silviculture is a means to meet objectives ranging from timber production to wildlife habitat to naturalness. A common global trend in forestry is development of new silvicultural approaches as alternatives to plantation forestry that bear names that include the words ‘nature’, ‘ecological’ or some other positive expression regarding their intent or effects. Some approaches are attempting to emulate natural processes and others to minimize disturbance effects in an attempt to be more natural. In any case, the effects of climate changes, non-native plants, insects, pathogens and animals, and other anthropogenic effects are creating novel forest ecosystems where the silviculture of the past may not be appropriate. It should be recognized that forestry has always attempted to manage stands to meet objectives in ways that would not be similarly met without management. Rather than acquiescing to pressures to follow a nature-based model based on the past, we need to recognize that our forest ecosystems are changing and the rate of change may accelerate in the future. Natural processes and stand structures are important information about natural systems, but not necessarily for the management of these changing systems. Management of these novel ecosystems to meet societal needs will have to be novel. Rather than striving to be close to a nature that is under constant change, silviculture should strive to be better than nature. ‘Close-to-nature’ is flawed in both its intent to emulate nature and as a means to meet shifting ecological conditions and societal needs.

Description: This study employs a recursive dynamic spatial partial equilibrium model to investigate the trade flow trends in the global softwood log market. A baseline forecast from 2012 to 2021 is first projected and then compared with three alternative scenarios: (1) Russia reduces its ad valorem softwood log export tax to 8 per cent to comply with its World Trade Organization accession agreements; (2) New Zealand experiences no expansion at all of its plantation forest log production due to social and environmental considerations (i.e. increased Māori ownership of forest land and the implementation of emissions trading schemes); and (3) a combination of the proposed policies in Russia and New Zealand mentioned above. The results of the baseline projection demonstrate that softwood log prices will increase in every region globally and that China will continue to be the world's largest softwood log importer. However, softwood log exports from Russia, the US and Canada are expected to drop significantly as a result of current Russian export restrictions, the recovery of the US housing market and mountain pine beetle infestations in western Canada. A comparison of the simulated scenarios with the baseline projection reveals that reducing the Russian softwood log export tax will have a greater impact on softwood log prices and total world trade than restricting log production in New Zealand due to the comparatively large log production capacity in Russia. In any scenario, significant trade flow changes (i.e. trade-offs) in response to the proposed policy changes are observed in China and the major export regions. The results of this study offer insights for forest managers and policy makers to examine the global impacts of potential changes in trade policies and supply constraints in these two important softwood log supply regions in addition to highlighting China's role in the world softwood log market.

Description: The mountain pine beetle (MPB) epidemic in British Columbia (BC) peaked in 2004 and 2005, and by 2012, 〉53 per cent of the merchantable pine had been attacked. The annual kill has declined steadily since 2005 and is projected to continue to do so. However, given the significant amount of beetle killed wood, the timber supply is expected to fall dramatically in the coming decades. This study estimates the future provincial economic impacts of the MPB infestation in a dynamic computable general equilibrium (CGE) model, by examining the effects of the reduction in timber supply from BC forests over the 2009–2054 period. Results suggest that there will be a cumulative present value loss of $57.37 billion (or 1.34 per cent) in GDP and a $90 billion decline in welfare (compensating variation) from 2009 to 2054 in BC. These estimates emphasize the significance of negative economic impacts that may be in store for the economy in this, and potentially other provinces, and can be used to help policy-makers better understand the net benefits of adaptation options geared towards reducing the spread of such pests.

Description: Maputaland’s woodlands are under utilization pressure inside and outside conserved areas due to mounting densities of mammals in the former and increasing human utilization of vegetation in the latter. Conservation of this biodiversity hotspot requires a better understanding of vegetation dynamics. To this purpose, woodland vegetation structure was evaluated at three sites through size class distribution analysis and grain determination, a forestry concept here applied to woodlands. The three sites represented animal disturbance/utilization, human disturbance/utilization and no disturbance/utilization regimes for comparable periods. Common species occurrence patterns differed between sites. The woodlands of all three sites were mostly fine-grained forest-like vegetation units and followed fine-grained forest dynamics closely. The grain model performed successfully for the region’s woodlands and proved a good tool to improve vegetation dynamics understanding. In general, people and herbivores led to local extirpation of species and threatened both ecological structure and function of Maputaland’s woodlands. However, the fine grain status was considered positive, as it facilitated future management options by reducing time frames and scale of management actions to be applied.

Description: We examined the sensitivity of social benefits to the amount (scope) of protected natural areas (PNAs) in the Eastern Canadian province of New Brunswick using the contingent valuation method. Household willingness-to-pay responses were elicited under three valuation scenarios: (1) maintaining the existing amount of PNAs at 2 per cent of the provincial land base; (2) increasing the PNAs to 8 per cent of the provincial land base; (3) increasing the PNAs to 14 per cent of the provincial land base. Under these scenarios, mean willingness-to-pay values were estimated at $58.63, $66.57 and $71.29 (CDN) per household per year, respectively. While these mean values initially indicated that social benefits were sensitive to scope, analysis of values within the 95% confidence interval revealed scope insensitivity. The possible sources and implications of these findings are discussed in the context of future benefit–cost analyses associated with PNA policies in the province.

Description: Although partial harvesting has been proposed as a measure for maintaining compositional and structural characteristics of natural old-growth stands, it has not been rigorously evaluated. The first objective of this study was to compare forest composition and structural characteristics after killing a portion of canopy trees and after partial cuts in boreal mixedwoods of eastern Canada by natural disturbances. The second objective was to evaluate the effectiveness of the partial harvest treatments in meeting the silvicultural objectives of increased growth of residual stems and advances in regeneration. Higher densities of shade-intolerant species were found after partial cuts when comparedwith naturally disturbed stands. Similar diameter distributions of residual living trees and densities of shade-tolerant species were found following all disturbances. Increase in growth was similar for all height classes (〈1 m, 1–2 m, 2–4 mand 〉 4 m) of balsam fir ( Abies balsamea ) advance regeneration in naturally disturbed and partially cut stands. In the overstory, trembling aspen ( Populus tremuloides ), white birch ( Betula papyrifera ), white spruce ( Picea glauca ) and balsam fir had growth increases after partial cuts, whereas black spruce ( Picea mariana ) did not. This study provides evidence that partial cutting in these mixedwood stands may emulate the effects of natural mortality resulting from natural partial disturbances by retaining key compositional and structural attributes and inducing increased growth rates in residual trees.

Description: Although widely considered to be a core aspect of quality assurance of climate change mitigation activities, additionality remains a source of much controversy in relation to carbon accounting and carbon markets. This article illuminates the multi-faceted nature of the concept and develops a taxonomy of different forms. It provides an overview of how additionality is currently applied in relation to both compliance and voluntary carbon markets, including tests used and underlying evidence base requirements. This draws upon and updates an earlier review commissioned to help inform development of a Woodland Carbon Code designed to underpin climate change mitigation activities in the UK by the forest sector. Sources of uncertainty and trade-offs in practical application of the concept are highlighted, and potential perverse incentives explored.

Description: Forest management involves considerable amounts of uncertainty related to future timber prices and tree growth. A new element in forest-management planning is climate-induced change in tree growth. This study used stochastic adaptive optimization to derive optimal adaptive rules for the management of a mixed stand of Norway spruce, Scots pine and birch, when (1) both price and growth were stochastic and (2) there was a climate-induced growth trend. Optimized reservation-price function was used as the adaptive rule for final felling. The optimal times of thinning treatments were described by rules that related the thinning year to the growth rate of the stand. The results suggest that an improving growth trend slightly shortens optimal rotation lengths. On the other hand, risk related to timber price and growth tended to increase the rotation length. Increasing timber-price volatility increased the reservation price and rotation length. When risk and risk-aversion increased, maintaining a more diverse stand structure was profitable.

Description: Dominant understorey shrubs can interfere with tree recruitment and affect forest succession. In boreal forests of eastern Canada, Kalmia angustifolia grows vigorously dominating post-harvest black spruce ( Picea mariana (Mill.) BSP) forests and interferes with tree regeneration. Kalmia is a dominant understorey in all stages of forest development, but its response to canopy light level is unknown. We studied the morphological and physiological responses of Kalmia in open sun (control) and experimentally low, medium and high shades allowing 100, 60, 32 and 19 per cent of full sunlight representing 0, 40, 68, and 81 per cent shade, respectively. We tested the hypothesis that Kalmia responds positively to moderate shade by adapting morphologically with larger leaf area and fewer flowering shoots and physiologically by increased stomatal conductance, photosynthesis and foliar nitrogen than low or high shade. We found significantly increased leaf area, specific leaf area and decreased flowering shoots with increasing shade. Kalmia aboveground biomass was 31 per cent higher in low shade and 22 per cent lower in high shade compared with control. The highest maximum photosynthetic capacity ( A max ) of Kalmia (9 µmol CO 2 m –2 s –1 ) was found in control (full sunlight) and the lowest (5 µmol CO 2 m –2 s –1 ) in the medium-shade treatment. We concluded that Kalmia adapts to moderate shade by morphological plasticity, reproductive trade-off (avoiding sexual reproduction) and physiological acclimation to low light.

Description: The world-renowned Bialowieza National Park (BNP) in Poland has long been the object of research that provides information on the status and development of the entire, relatively large area of well-preserved lowland forest. For that reason, the aim of the work presented here was to characterize the current structure and dynamics of natural forests in Strict Reserve of BNP (SR-BNP), which covers 4584 ha. The research material encompassed the results of measurements on 460 temporary and 160 permanent sample plots. Results revealed an increase in the level of regeneration, whereas the standing volume is seen to have decreased slightly. Changes occurred in volume of certain tree species, as well as in proportions in given size classes they accounted for. The most marked increase was noted for Carpinus betulus , followed by Alnus glutinosa , Tilia cordata , Betula spp., Acer platanoides and Pinus sylvestris . Only in the case of Picea abies was a significant decrease noted. A decline of P. abies , mainly due to Ips typographus infestation, was revealed. Currently, only 6 of the 17 species of trees growing in the SR-BNP included specimens that were growing from the regeneration layer into the overstorey in more significant numbers. Due to a reduction of species diversity in ingrowth, a gradual depletion of species richness in the SR-BNP stands should be anticipated.

Description: In this study, a dynamic chamber method was used to measure respiration rates ( R CWD ) of logs in five decay classes (DCs) (ranging from freshly felled logs in DC 0 to highly decomposed logs in DC 4) in a Sitka spruce ( Picea sitchensis (Bong) Carr.) forest stand. The effects of change in temperature ( T c ) and log moisture content (MC t ) on R CWD were determined and annual decay rates estimated. The decay rates were used to estimate annual carbon (C) flux from logs resident in six managed Sitka spruce forest stands of different ages (23–45 years). The highest mean R CWD was recorded for DC 3 logs (40.43 mg CO 2 kg –1 h –1 ) and the lowest for freshly felled DC 0 logs (10.16 mg CO 2 kg –1 h –1 ). T c accounted for 62–85 per cent of the variation in R CWD from logs in different DCs, whereas MC t accounted for 0.07–74 per cent. Together, T c and MC t accounted for 78–87 per cent of the variation in R CWD . Decay rates for all DCs ranged from 0.007 to 0.063 year –1 , and the C flux ranged from 0.011 to 0.504 Mg C ha –1 year –1 and was not dependent on forest age or the number of thinnings. Knowledge of the contribution of coarse woody debris (CWD) fluxes to total forest ecosystem respiration will improve the accuracy of forest C accounting and assist in CWD management.

Description: Wildlife studies to determine preferred habitat often involve sampling used sites and making comparisons with unused background sites. We apply these data to a somewhat different purpose, which is to assess the spatial distribution of important habitat variables relative to spotted owl nest sites. It is necessary to compare habitat characteristics of used and unused sites to understand habitat preferences. However, ecological literature provides little guidance for selection of appropriate background sites necessary for such an analysis. We apply propensity score matching to telemetry gathered samples of spotted owl habitat for the purpose of weighting the selected background sites. This helps to ensure that important covariates have similar distributions in the used and unused habitat samples. We propose a two-stage process where propensity score matching of used and unused sites results in weights that are applied in the second stage modelling process. The objective is to quantify how wildlife responses to important variables change with distance from a nest, den site or other central location. The expectation is that this will strengthen guidance to managers who wish to protect or to improve wildlife habitat on their forest land. Example applications using spotted owl telemetry data demonstrate how to apply the methods and show the potential to elucidate habitat characteristics.

Description: Forest site productivity maps can be of great help for sustainable forest management. Site productivity maps, commonly representing the site index (SI) of a specific tree species, allow foresters to forecast wood production over the entire area of interest and hence select the most appropriate location for establishing a particular tree species mix. In many situations, forest SI cannot be directly measured from the dominant height and age of a stand and must therefore be directly estimated from relevant local site factors related to climate, topography and/or soil (attribute-based approach). Alternatively, estimations can also be made based on site information available for nearby locations (location-based approach). Also both approaches can be combined (hybrid approach). Since there is no straightforward procedure for selecting the most appropriate approach, the performance of five regionalization techniques was compared for predictive mapping of the SI of two important tree species in the temperate lowland region of Flanders (Belgium): one location-based technique (ordinary kriging), one attribute-based technique (regression) and three hybrid techniques (geomatching, ordinary co-kriging and regression kriging). From the findings of this case study, it cannot be concluded that one technique outperforms the others under all circumstances, but it was possible to build a decision tree providing guidance in selecting an appropriate SI mapping technique depending on the availability and characteristics of the data.

Description: Oak-hickory forests in the Ozark and Ouachita Mountains of Arkansas recently experienced an episode of oak mortality in concert with an outbreak of the red oak borer ( Enaphalodes rufulus (Haldeman) (Coleoptera: Cerambycidae)). We utilized data from the Forest Inventory and Analysis (FIA) program of the USDA Forest Service to explore changes in percent red oak ( Quercus subgenus Erythrobalanus ) mortality as a function of standing trees, basal area and stem density during and after the recent borer outbreak throughout the state of Arkansas. Mean red oak mortality levels in Arkansas FIA oak-hickory plots that were sampled both during and after the borer outbreak increased from 19 ± 3 to 34 ± 4 per cent of standing red oaks, resulting in significantly reduced red oak basal area and stem density in these stands. Mean size of red oaks did not change significantly during this time period, implying that all size classes experienced mortality. After red oak borer populations subsided, oak-hickory survey plots experienced increases in red oak mortality levels during a drought year (2006) and after an ice storm (2009), which suggests that these stress events, in addition to prior red oak borer infestation, could have had some influence on tree mortality.

Description: Since the height horizon remains undetected in the vast majority of height series sampled in forest stands, even of notable ages, the realism of the traditional asymptotic-size modelling assumption is questioned. The aims of the study were to present an original non-asymptotic growth model and to test its accuracy against asymptotic-size equations. The equation proposed is a first-order four-parameter autonomous differential equation. The related sigmoid size curve has a parabolic branch of time. It was tested on 349 old growth series of top height (1047 stem analyses) selected to explore the maximum observed ranges of age and site conditions in seven temperate tree species growing in pure and even-aged stands. The fitting accuracy of this equation and three classical asymptotic-size growth equations (Richards, Hossfeld IV and Korf equations) were compared, with parameterizations of increasing flexibility. For the different parameterizations, the proposed growth equation showed higher performances than asymptotic growth equations, attributed to its non-asymptotic property and to the mathematical independence between parameters related to the inflection point and late growth. Top height growth was therefore accurately modelled by a sigmoid curve not based on the asymptotic-size assumption. This equation may be of general relevance to tree growth modelling.

Description: ‘Los Alcornocales’ Natural Park (southwest Spain), one of the most important Mediterranean cork oak ( Quercus suber ) forests in Europe, has experienced a substantial tree dieback in the past decades. We hypothesize that areas experiencing high eutrophication should exhibit higher leaf nitrogen (N) concentrations and lower N resorption efficiency and proficiency indices than areas under lower environmental stress, and this could be related with forest functioning and tree mortality rates. To test this hypothesis, we collected leaf and soil samples from four plots in the southern part of the park, near a polluted industrial area, and four plots in the northern part of the park, far from this pollution source. N and phosphorus (P) in green and senescent leaves and soil NH 4 + -N, NO 3 – -N and PO 4 3– -P were analysed. Foliar N and the leaf N:P ratio were significantly higher in the southern plots (high-mortality plots) than in the northern plots. The resorption efficiency was significantly higher for P than for N in all southern and northern plots. The values of resorption proficiency indicated incomplete resorption for N and complete resorption for P in all plots. Our results suggest that oak populations showing high-mortality rates may be associated with tree N and P imbalance.

Description: Equations that relate individual tree diameter at breast height (d.b.h.) and total height (HT) are important because HT is not widely measured and is often needed to estimate stem volume or predict HT growth. The primary goal of the study was to construct a regional HT to d.b.h. equation (H-D) for 15 tree species of the Acadian Region. Specific objectives were to (1) evaluate performance of the Forest Vegetation Simulator Northeast Variant (FVS-NE) equations, (2) explore suitable model forms and compare the influence of various tree- and stand-level variables on HT prediction and (3) develop species-specific equations that are unbiased across a broad geographic region. Data were available from an extensive database covering Maine, three provinces of the Canadian Maritimes and southern Québec. The study showed that the widely used FVS-NE model had significant prediction biases for all species in the region. The best model form among those evaluated was the von Bertalanffy–Richards (vB-R; commonly referred to as the Chapman–Richards), with added covariates that included crown competition factor, basal area in trees larger than subject tree and a climate-derived site index.

Description: The transitioning of land from forest to other uses is of increasing interest as urban areas expand and the world's population continues to grow. Also of interest, but less recognized, is the transitioning of land from other uses into forest. In this paper, we show how rates of conversion from forest to non-forest and non-forest to forest can be estimated in the US from a continuously improving publicly available annual forest inventory database, under varying definitions of conversion. Two estimation approaches are considered and contrasted. The approaches are a simple ratio estimator and the weighted maximum likelihood estimator. The latter involves a statistical procedure that incorporates the binomial nature of the indicator variables, the transition of mapped plot conditions and an intuitively appealing way to combine data from varying remeasurement periods for a temporally dependent variable.