ALBERT

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: 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.

Description: The boreal forest is the world’s largest terrestrial biome, covering all continents in the northern hemisphere. Much research has focused on the effects of forest management and climate change on biodiversity and ecosystem level processes of the boreal forest. However, even though climate change and the increasing rate of resource exploitation are likely to intensify the arrival and establishment of exotic species with the potential to become invasive, the boreal forest continues to be viewed as inhospitable to incoming species and we have little understanding of its invasive species status. We reviewed the literature and compiled information on the current status of invasive species across all taxa present in the North American boreal forest. We found that an increasing number of exotic plants, insects, earthworms, slugs and pathogens are establishing in the boreal forest. Research is scarce and their ecological effects are poorly understood. However, given that some of the reported species represent a major driver of change in many ecosystems globally, we expect that this review will provide direction for invasive species research as well as preventative measures aimed at better understanding and conserving Earth’s largest terrestrial biome.

Description: Early-successional forest habitat (ESFH), characterized by dense, short-statured woody vegetation, abundant and diverse herbaceous vegetation and high productivity-to-biomass ratios, supports diverse and productive terrestrial faunal communities. In upland forested areas, small watersheds, encompassing ecologically interconnected terrestrial and freshwater habitats, are fundamental units of the landscape for managing and protecting terrestrial and aquatic biodiversity. However, little is known about how the occurrence or abundance of upland ESFHs affects linkages between aquatic and terrestrial species and communities in these small watersheds. It is likely that the presence of ESFH in small watersheds affects the magnitude and direction of aquatic–terrestrial linkages, which may, in turn, affect overall biodiversity. We conducted a literature review of current information on aquatic and terrestrial biodiversity in small watersheds as related to forest age and structure. While the review identifies some fundamental uncertainties and information gaps, there is no evidence of negative effects of the creation and maintenance of upland ESFH on aquatic and riparian diversity. Increased aquatic production, due to higher light and nutrients, and increased primary and secondary production in ESFHs have the potential to increase watershed biodiversity. The review underscores the need for systematic evaluation of these potential outcomes to inform the management community.

Description: This study focuses on the usage of Doppler lidar to provide information about the turbulence structure above forest edges. Comparison with state-of-the-art laser Doppler anemometry measurements on a physical model in an atmospheric boundary layer wind tunnel shows that the lidar is able to resolve details of the wind field at a change of roughness in an appropriate order of magnitude. Measurements of real wind situations with moderate wind speed directed to and from the forest edge, as well as the investigation of a storm event with wind velocities of up to 45 m s –1 , reflect well-known characteristics of the isolines of mean wind speed and its standard deviation and reproduce quantitative values of the wind field found in previous studies. The wide measuring zone of the lidar indicates an extent of the perturbation generated by the change of roughness at the forest edge of more than 30 tree heights in the horizontal and up to 6 tree heights in the vertical. A significant decrease in the integral length scale and an increase in the slope of the velocity spectra above the tree tops reflect the generation of smaller eddies in this region.

Description: This study was carried out in three stands with fir and spruce ( Picea abies L. Karst.), pine ( Pinus sylvestris L.) and beech ( Fagus sylvatica L.). The objectives were to characterize the spatial pattern of topsoil variation; to determine the contribution of local stand density and local species composition to small-scale variation in topsoil morphology, pH and gravimetric water content during mild midsummer drought; and to compare the effect of spruce, pine and beech vs fir. Although local stand density was related to soil properties, only in the case of single soil characteristics could this variable explain more than 10 per cent of their variation. Compared with fir, increasing density of pine exerted a stronger effect on an increase in organic horizon thickness and a comparable effect on a decrease in pH, but a weaker effect on decrease in topsoil moisture. Irrespective of the soil characteristics, the effect of spruce was approximately twice as strong as that of fir. Beech, however, had a much weaker effect on a decrease in topsoil moisture than did fir and the influence of this species on topsoil pH was the opposite.

Description: Australian acacias are widely planted as exotics and in some cases as invasive. Impact may be reduced if sterile triploid planting stock can be developed. This article reports the first step in such a breeding programme, the production of a population of tetraploid lines for inter-breeding with diploids. Three methods of polyploid induction with colchicine were compared. A conversion rate of 8.9 per cent was obtained by applying 1.5 per cent colchicine to the shoot apical meristem of seedlings. A 7 per cent conversion rate was obtained by germination of scarified seed on filter paper saturated with 0.02 per cent colchicine for 16 h and this method is recommended on logistical and safety grounds. Poor results were obtained when scarified seed were submerged in aqueous solutions of colchicine. Flow cytometry is the preferred method for ploidy determination, sampling after vegetative phase change on a minimum of two opposing phyllodes per plant. Visual classification was inaccurate due to the confounding effects of growth-retarding properties of colchicine. Size and distribution of stomata can also be used but is more time consuming than flow cytometry. At 26 months, tetraploid plants had heavier, thicker, wider and more cupped shaped phyllodes than diploids and the bark: stem diameter ratio was greater.

Description: The native Eurasian red squirrel is considered endangered in the UK and under strict legal protection. Long-term habitat management is a key goal of the UK conservation strategy. Current selection criteria of reserves and subsequent management mainly consider species composition and food availability. However, there exists a critical gap in understanding and quantifying the relationship between squirrel abundance, their habitat use and forest structural factors. This is partly a result of limited availability of structural data along with cost-efficient data collection methods. We investigated the relationship between structural characteristics and squirrel feeding activity in Scots pine. Field data were collected from two study areas: Abernethy and Aberfoyle Forest. Canopy closure, diameter at breast height, tree height and number of trees were measured in 56 plots. Abundance of squirrel feeding signs was used as an index of habitat use. We used a generalized linear model to model the response of cones stripped by squirrel in relation to field-collected structural variables. Results show that forest structural characteristics are significant predictors of feeding sign presence; canopy closure and number of trees contribute to explain 43 per cent of the variation in stripped cones. Our findings critically highlight the need to consider stand structure in management for red squirrels.

Description: Harmonized forest area information provides an important basis for environmental modelling and policy-making at both national and international levels. Traditionally, this information has been provided by national forest inventory statistics but is now increasingly complemented with remote sensing tools. Reliability and harmonization of both sources are important aspects to ensure comparability and to enable the development of international forest scenarios. Initiatives with the purpose of harmonization of forest area for both sources are currently ongoing. Nevertheless, all forest area estimates contain uncertainties, which must be quantified and included in the error budget. This is a prerequisite for combining and comparing data. The purpose of this study is to compare, taking into account uncertainties, forest area estimates for year 2000 derived from four different harmonized satellite-based maps, covering Europe with recognized official forest statistics. It was found that the major cause of disagreements between official statistics and map-derived forest area originates from the general issue of accounting for land cover instead of land use. Consequently, CORINE land cover results had the best accordance with official statistics due to its focus on land use. The other maps overestimated the forest area in mountainous countries and showed underestimation in countries with large forest area or open forest formations.

Description: A sampling strategy to be used with multi-phase forest inventories is proposed for assessing scattered trees outside the forest on large territories. The first phase is carried out by means of a systematic search over the area to be inventoried. The area is partitioned into regular polygons of the same size and points are randomly located, one per polygon. Subsequently, in the second phase, the land cover class of the first-phase points is determined by very high-resolution remotely sensed imagery and a sample of points are selected from each land cover stratum. Then, the number of trees outside the forest lying within plots at the sampled points is recorded on the imagery. Finally, in the third phase, a subsample is selected from the second-phase samples of each stratum and the biophysical attributes of trees within plots are measured in the field. Approximately unbiased estimators of abundance and of totals and averages of biophysical attributes are achieved in the second and third phase, respectively, together with the estimators of the corresponding variances. A simulation study is performed in order to assess the accuracy of the strategy under random and aggregated distributions of trees. The sampling errors achieved in the second phase using sampling fractions of ~0.3 per cent of trees vary from 6 to 13 per cent, whereas the errors achieved in the third phase using sampling fractions of ~0.15 per cent vary from 15 to 31 per cent. The results obtained from three case studies carried out in Italy confirm the accuracy levels achieved in the simulation.

Description: A new model for computing the allowable cut for uneven-aged stands is described. The model is focused on the Gini index against basal area and the target structure of stand volume on diameter classes, assumed to be achieved by the end of transformation period from even-aged to the uneven-aged structure. The real structure of the stand is characterized by a given Gini index while the target structure is characterized by a benchmark Gini index. In order to determine the benchmark Gini index, the model allows the establishment of target structure of the stand based on a new idea: target structure of trees number in diameter classes for a particular stand corresponds to a certain target distribution of volumes on diameter classes. According to the difference between the two mentioned Gini indices, a certain period for directing the real structure to the target structure is further chosen while the computation of the allowable cut is based on the assumption of Gaussian distribution of volume against diameter classes. Eventually, the computation of allowable cut takes into account the stand growth, the differences between the real and the target growing stock, the adopted transformation period and the management goals.

Description: Harvesting models are needed within simulation studies to assess ‘business as usual’ scenarios in future stand development. Such models require data from repeated observations addressing the removals as they are based on specific silvicultural management regimes. The purpose of this paper was to develop and apply a harvesting model for uneven-aged single-tree forest management based on data from the forest company ‘Forstbetrieb Ligist, Souveräner Malteser Ritterorden’ in Austria. This company has been known for its transition from even-aged to uneven-aged forest management since the 1930s. Our harvesting model comprises two logistic functions to simulate a single-tree selection process: (1) predicting the probability of harvesting and (2) removal. The set of equations are tested and implemented in the tree growth model MOSES (MOdelling Stand rESponse). MOSES is used as a diagnostic tool to assess different forest management regimes. In this study, we are specifically interested in (1) evaluating the model by comparing predicted and observed removals and (2) predicting future stand development considering the current management practices—the business as usual as it can be derived from the harvesting model. The results suggest that in combination with MOSES, our model correctly mimics the growth development over time since no systematic trends between predicted and observed diameter growth at breast height classes are apparent. Furthermore, it is evident that by applying the current plenter harvesting strategy, a constant stand basal area of ~35 m 2 ha –1 will be achieved.

Description: The article summarizes results obtained from several field experiments, measured in uneven-aged forests during a long period; from the 1930s until the present. Experiments have been established in both Norway spruce- and Scots pine-dominated stands. The purpose is to evaluate the feasibility of uneven-aged forest management under Finnish conditions and compare uneven-aged management to the current even-aged forestry. The analysed datasets demonstrate relatively rich regeneration under many types of tree canopies. The number of stabilized (height 0.1–1.3 m) spruce seedlings does not always correlate with the stand density. The amount of small labile (height 〈 0.1 m) spruce seedlings may even increase with increasing stand volume. Contrary to spruce, the regeneration of birch and pine decreases with increasing stand volume. The yield comparisons show that uneven-aged stands have often grown faster than even-aged stands with the same post-cutting stand density. High thinnings have resulted in better volume increments than low thinnings. Recent studies show that uneven-aged management is more profitable than even-aged rotation forestry (RF), especially with high discount rates. Uneven-aged management seems to be superior to current even-aged RF also with respect to environmental and multifunctional aspects, such as carbon sequestration, bilberry yield, structural diversity and scenic values.

Description: The selection method applied in shade-intolerant pine stands in the southern United States has been shown to be an effective method of uneven-aged silviculture, but it is becoming less frequently practiced for a variety of reasons. Economically, the high value of standing timber puts fully stocked uneven-aged pine stands at risk of liquidation if the timberland is sold. This is increasingly common on private lands in the southern United States, where forest industry landowners have been selling timberlands over the past two decades to timber investment management organizations and real estate investment trusts. Ecologically, the benefits of open woodland habitat restoration in southern pines are being optimized by use of prescribed burning, which is much more adaptable to even-aged silvicultural systems such as the shelterwood method than it is to the selection method. But uneven-aged silviculture will be important in the twenty-first century; its values centre around the ability of uneven-aged stands to resist and especially to recover from exogenous disturbance events, as well as the opportunity for frequent establishment of new regeneration cohorts under changing climatic conditions.

Description: While sustainable forest management (SFM) policy processes are well developed, implementation on the ground remains a challenge. Given the diversity of biophysical conditions, economic histories and governance systems on the European continent, regionally and temporally adapted and adaptive solutions are needed for both social and ecological systems. To illustrate this, we apply (1) a biographic forest and woodland history approach to central Sweden’s Bergslagen region, where boreal sustained yield forestry was widely applied first and (2) a comparative case study approach using five European landscapes that represent different forest history phases in Scotland, Germany, Ukraine and Russia. Additionally, we illustrate the need to learn from reference landscapes for natural forest and cultural woodland systems such as in economically remote regions in Romania, Russia and on the Iberian Peninsula. We conclude that there is great opportunity for innovative knowledge production about both governance and management for different SFM dimensions based on comparisons among concrete landscapes. In addition, there is a need to develop local place-based social learning processes that are characterized by a focus on a geographical area, commitment to SFM policy visions and collaborative approaches to development that include both ecological and social systems.

Description: The relationships between climatic variables, soil parameters, tree nutrition and site index (SI) were examined in 30 chestnut coppice stands in Asturias, the region with the largest area of chestnut coppice in north-west Spain. SI was estimated from a top height projection equation for this species. A soil sample was obtained at 0- to 20-cm depth and several leaves were collected from the upper zone of the dominant trees in each plot for further analysis. Chi-square automatic interaction detection and parametric regression techniques were used to determine the key factors affecting SI. According to the regression tree and the parametric regression model for all variables, the extractable Mg in the soil and mean temperature of the warmest month were the most important variables explaining SI in the region. Elevation and foliar concentrations of phosphorus were not significant factors in the parametric regression analysis (although considered key factors when foliar nutrients and physiographical variables were analysed separately). The results show the importance, for chestnut growth, of site selection and balanced fertilizer treatment consistent with the soil requirements of the species.

Description: The identification of past insect outbreaks is often determined using a comparison of host/non-host tree ring growth chronologies. Yet this may be a problem when non-hosts are either affected by the outbreaking insect or when the growth of host and non-host trees does not respond similarly to the same climatic factors. We investigate the use of a blind source separation method to identify past outbreaks. This method, used in neurology and called independent components analysis (ICA), directly identifies disturbance patterns. We analysed the tree-ring data from papers dealing with insect outbreaks. These papers focus on western spruce budworm, pandora moth and Douglas-fir tussock moth outbreaks. We compared the results of the original analyses, conducted using the host/non-host approach, with results from ICA. We detected the outbreaks identified in the original papers. However, the start and end dates for the outbreaks were different in 75 per cent of the ICA analyses. On the other hand, we were able to detect growth reduction in non-host Ponderosa pine chronologies as well as increased growth during outbreak periods. Since conventional methods may be less robust when the growth of non-host trees is affected, the ICA may provide a powerful new method to identify outbreaks in such situation.

Description: To implement policies on sustainable forest management (SFM), there is a need to satisfy economical, ecological and socio-cultural sustainability objectives. Due to a long history of sustained yield wood production to satisfy the needs of the forest industry, clearfelling management systems are used in ~96 per cent of managed forests in Sweden. To satisfy the intentions of contemporary forest and land use policies, uneven-aged forest management systems as a complement are currently debated. We interviewed local forestry stakeholders in the Swedish boreal forest region’s north and south about their views on and attitudes towards different forest management systems’ contribution to SFM. Most stakeholders were generally negative to the use of uneven-aged system for sustained yield wood production but saw advantages for ecological and socio-cultural dimensions of SFM. To encourage the use of even-aged cohort and uneven-aged systems to satisfy all dimensions of SFM, there is a need for improved communication, education and public awareness. This could ultimately lead to a more constructive and less heated debate. In addition, there is a need of more empirically based knowledge about uneven-aged and cohort forest management systems’ pros and cons when it comes to satisfying economical, ecological and socio-cultural objectives.

Description: There is a need for a better understanding of the primary role of macronutrients in Aleppo pine stock quality and for producing larger nutrient-loaded stock, which may be challenging for inland nurseries. The influence of nursery location and fertilization on nursery culture, growth, allometry and seedling quality of Aleppo pine was studied in seedlings cultivated over the 2006 growing year. Fertilization treatments considered how a K enrichment performed over common programs currently being practiced and divided into three levels of K/N ratio: 0.63–0.89 (normal), 1.81–1.89 (high), and 2.25–2.53 (very high). Results showed that fertilization had a minor effect on seedling growth and allometry in comparison with location, which was the governing factor. However, fertilizing treatments significantly affected final seedling attributes, which has its origin on the early treatment differences that were kept up to the end of culture. Higher nutrient supply treatments produced the highest nutrient concentration in seedlings but they were associated with lower fertilization efficiencies. Fertilizer efficiency was approximately twofold in the coastal nursery for the three macronutrients, although concentration was higher in the inland nursery due to lower seedling growth. It is concluded that warmer regions are more suitable for producing large stock more efficiently.

Description: Based on a literature review and on a new bioeconomic modelling approach, we investigated whether or not clear-cutting and mono-species forests are the optimal silvicultural strategies under the presence of risk. The model reflects a risk-avoiding attitude and builds upon portfolio theory. The selected tree species and the timing of regeneration harvests constitute a total of 22 management alternatives. Optimal area fractions of the alternatives were combined at the stand level to find the maximum value at risk (VaR, annualized net present value exceeded with probability of 0.99). Relevant uncertainties were integrated via Monte Carlo Simulation and bootstrapping. The results showed a maximum VaR for a highly diversified treatment combining 42 per cent Norway spruce and 58 per cent European beech and included area fractions with regeneration harvests from age 50 to 120 years. This treatment avoids clear-cutting and a mono-species forest composition. It uses tree species diversification and extends the regeneration period over 70 years to diversify hazard and price risks. The resulting scenario may be called ‘near-natural’ and emerges as the optimal choice, particularly for cautious, and thus risk-avoiding forest owners who do not have the opportunity to diversify risks by means of large-scale forest properties.

Description: Studies of old-growth forests are becoming increasingly important for the improvement of silviculture and for understanding environmental changes. However, in Europe such forests are rare, fragmented and influenced by millennia of human activity. Comparative studies of old-growth forests across Europe are needed to improve knowledge on how direct and indirect anthropogenic factors influence their structure. We analysed structural dynamics in 15 silver fir-beech-Norway spruce old-growth forests in Slovenia, Croatia, Slovakia and Bosnia-Herzegovina. Changes in diameter distributions, stand parameters and regeneration were analysed at intervals of 6–116 years. Most diameter growth at breast height (d.b.h.) distributions approximated a rotated sigmoid shape, which could be explained by differences in growth and mortality rates with respect to d.b.h. class and by disturbance history. Our results suggest that different disturbance types are likely to cause different changes in d.b.h. distributions. For example, overbrowsing, canopy dieback of silver fir and windthrow decreased the density of small, intermediate and large-diameter silver fir, respectively. The slopes of the fitted diameter distribution curves were steeper for beech than for silver fir, which could be explained by their different life strategies. Despite disturbances, growing stocks remained stable over the long term. A synchronous silver fir decline was confirmed. It was more pronounced in Slovenia and Slovakia, both of which experienced more SO 2 pollution and had higher ungulate densities. The silver fir sapling stage was often totally absent in both countries. Our results suggest that anthropogenic disturbances, especially air pollution and overbrowsing (resulting from human-induced increases in deer density), significantly influenced the coexistence of silver fir and beech; asynchronous, patchy changes in species mixture have been replaced by large-scale synchronous changes.

Description: The development of uneven-aged forest management in the Dinaric region (north-west Balkans) is reviewed. Uneven-aged silviculture has been the major silvicultural system in the region since regular forest management began in the second half of the nineteenth century. Regular forest management in former virgin forest areas began as selection forest management mainly because of the awareness of the importance of multilayered continuous forest cover for preventing soil erosion on carbonate substrate. The observed period of more than 100 years has seen several changes to uneven-aged forest management ranging from the complete domination of rigid selection forest management to the gradual acceptance and eventual domination of the irregular shelterwood system and finally to the acceptance of freestyle forest management, which is presently practiced in the Slovenian part of the Dinaric region. Freestyle silviculture combines practices of different silvicultural systems. By using this system, consideration for site conditions and heterogeneous stand dynamics at small spatial scales is possible. In the observed period, some stand parameters of Dinaric forests have changed substantially. Growing stock has increased significantly, the number of large-diameter trees has increased and alternation of the main tree species (silver fir and European beech) has occurred. The development of uneven-aged forest management is described and its prospects are discussed.

Description: We estimate a suitable strip-gap arrangement in Japanese cedar ( Cryptomeria japonica ) plantations to promote the growth of beech ( Fagus crenata ) seedlings and control dwarf bamboo ( Sasa kurilensis ) in mountainous areas using a hemispherical model and United States Geological Survey Digital Elevation Model (DEM). Clarification was also sought on whether the gap arrangement should be altered with topography and original stand structure. Nine modelled plantations were established by combining tree inventory and DEM data from three C.japonica plantations. We simulated spatial and temporal variations in photosynthetic photon flux density in stands 5 years after strip-gap creation under six scenarios for each modelled stand and integrated the light responses of F. crenata seedlings and S. kurikensis into the model. Finer strip-gap mosaics with gap width narrower than half the tree height inhibit the growth of S. kurikensis and provide a wider area suitable for F. crenata growth. Our simulation indicated a suitable strip-gap arrangement should be based on the stand structure but not necessarily on topography. However, it indicated that the possible range of practical gap arrangements changed with topography. The decision-support model for gap arrangement used in this study combined with DEM data provides flexible gap creation options adaptable to specific plantations in mountainous areas.

Description: Almost all commercial forests of Finland are simultaneously used for timber production, outdoor recreation and biodiversity maintenance. For the past 60 years, the official line of silviculture has been even-aged management. However, uneven-aged management and other forms of continuous cover forestry are gradually gaining popularity and also official acceptance. This study analyzed variable density thinning (VDT) in the context of uneven-aged management of Norway spruce ( Picea abies L.Karsten) stands. The aim was to find economically profitable management systems, which would result in forests that are good for recreation and biodiversity maintenance. The stand compartment was divided into cutting segments and only one segment was harvested at a time. When economic profitability was maximized as the sole management objective, 15-year cutting cycle with uniform thinning (UT) was the optimal management system. All trees larger than 19 cm in diameter at breast height (all saw log-sized trees) were removed in the cutting. When a continuous presence of large trees was required, VDT was clearly more profitable than UT. In VDT, all large trees were removed from the thinned places but there were large trees in the segments that will be cut in the next logging operation. The optimal cutting cycle (interval between successive cuttings in the same place) of VDT was 20–30 years when large trees were required in the post-cutting forest. Several combinations of the length of cutting cycle and number of cutting segments were nearly equally profitable. Profitable options were, for instance, to divide the stand into four cutting segments each cut at 20-year interval or three segments each cut at 30-year interval.

Description: We aimed to assess the potential of the natural regeneration of broadleaved tree species in relatively dense and approximately 30-year-old hinoki cypress ( Chamaecyparis obtusa ) plantations on the Pacific side of Shikoku in south-western Japan. The composition and size structure of naturally established canopy and sub-canopy species were investigated in 18 plots at two hinoki cypress plantation sites, namely Okuono and Karakawa (OKU and KRK). Local variation in the density and species richness of naturally established stems were analysed in relation to overstorey stand structure, local topography, soil properties and understorey vegetation. OKU was noteworthy for its relatively high proportion of sub-canopy species and L-shaped height distribution of saplings (〉200 cm), while KRK was characterized by a wider range in the height distribution of saplings and a low density of seedlings (〈200 cm) despite the relatively higher dominance of canopy species. This was attributed to the differences in the characteristics of component species and the thinning history of the sites. The density and species richness of the saplings at both sites and the seedlings at OKU were higher in plots with lower mean heights of hinoki cypress and higher soil C/N ratios. These results suggest that variation in the growth of hinoki cypress, which is related to the soil nitrogen status, brings about local variation in the regeneration potential at these sites.

Description: Uneven-aged silver fir-European beech forests in Slovenia were studied to investigate the dynamics of their structure and composition in three different study areas over the last century, with a particular focus on silver fir dynamics. The study used current and archival data from forest inventories and historic forest management maps for a period of ~110 years. The dynamics of several structural and compositional parameters of the forest stands were also examined using a stand volume index, the Gini coefficient and a recruitment rate index. Substantial changes in diameter growth at breast height structure, stand volume, tree size diversity and tree species composition were documented during the observed period. Additionally, silver fir underwent large-scale changes. Significant differences, as well as some similarities, in forest stand dynamics were observed on a regional spatial scale. These dynamics are underpinned by a complex array of natural and anthropogenic factors; past forest use and the silvicultural systems applied, the impact of large ungulates and site characteristics seem to play important roles.

Description: The aim of this study was to assess the effect of cytokinins not commonly used for shoot induction from zygotic embryos of Pinus radiata D. Don. The influence of in vitro shoot and root induction treatments on the subsequent ex vitro development of the regenerated plants was also tested. Embryos were cultured with benzyladenine (BA), thidiazuron (T) and two cytokinins not previously assayed in radiata pine organogenesis ( meta -topolin (m-T) and zeatin (Z)) in a range of concentrations and induction periods. Shoot induction treatments were assayed in seeds from different geographical origins to obtain wider conclusions. We analysed the effect of these cytokinin treatments on in vitro rooting with different auxins ((indole-3-butyric acid (IBA) and 1-naphtalene acetic acid (NAA)) and the traditionally used mixture. After in vitro rooting, the plantlets were acclimatized and their ex vitro behaviour was evaluated. Shoot induction treatments with 1 μM BA for 2 weeks, 4.4 μM BA for 3 weeks or 1 μM Z for 3 weeks were more effective than the other treatments. An interaction between in vitro shoot and root induction treatments was observed. IBA was more efficient for plant production because the explants rooted in this auxin had better survival rates in the greenhouse.

Description: The well-being of people living in forest-dependent communities has been studied extensively, but little research has explored how this relationship has changed over time. Some theories suggest that regional differences in well-being should decrease, through the flow of capital and labour, while other work suggests that these inequalities will grow. Our research uses Census of Canada data at the census subdivision level at 5-year intervals between 1986 and 2001 to describe regional differentiation in the relationship between employment in forest sectors (logging, services, pulp and lumber) and unemployment and median family income as indicators of well-being. We found general declines, which varied somewhat by region, over time in forest dependence across the regions and changing composition of the forest industry across these sectors. The relationship between forest dependence and well-being over time varied by region, largely tied to intra-industry sector shifts.

Description: Continuous cover forestry (CCF) aims at enhancing stand structural diversity and favouring natural regeneration. To give guidance on how to manage a CCF stand to achieve seedling growth below canopy, an estimate of light transmittance is required. So far, in the UK, only stand-level parameters have been used by managers to predict the understorey light in CCF stands. We assessed a UK Sitka spruce stand undergoing transformation to CCF and measured canopy transmittance using hemispherical pictures. Stand-level characteristics were found to be highly stand specific and not appropriate to predict seedling growth in CCF stands. We parameterized a detailed light model (4C-A-RTM) and a simple one-layer turbid medium model (BL). A sensitivity analysis was performed to test the effect of key stand structural parameters on the modelled transmittance. Measured transmittance from hemispherical photographs was used to validate the models. Both models tended to underestimate canopy transmittance but were positively related to current-year growth of the below canopy seedlings ( R 2 = 0.92, P 〈 0.001). Comparison of the two models showed that the 4C-A-RTM provided a better estimation of light transmittance across observed canopy structural differences. Furthermore, the inclusion of stand characteristics in the 4C-A-RTM is likely to confer greater applicability across stands.

Description: Since the 1970s, a long-term research project has been conducted to monitor the changes in primary productivity of Chinese fir plantation at Huitong Ecosystem Research Station, Hunan, China. Standing biomass and net primary productivity (NPP) of the plantation were investigated at four times (7, 11, 14 and 18 years old) in two successive rotations on the same site. The mean individual tree biomass and stand biomass in the second rotation were reduced by ~18, 17, 7 and 3 per cent in 7-, 11-, 14- and 18-year-old stands, respectively, compared with the first rotation. In the first rotation, annual NPP was higher in the 7-, 11- and 14-year-old stands, but lower in the 18-year-old stands, compared with those in the second rotation. The proportion of biomass in stem, canopy (branch and leaf) and root was ~80, 13 and 7 per cent and 64, 20 and 16 per cent at the later stages of the stand development (≥14-year old) in the first and second rotations, respectively. The results suggests that relative large dry matter found in root systems in the second rotation increases the capacity of Chinese fir to exploit the soil for nutrient and water resources, which facilitates tree growth and productivity.

Description: Knowing the abundance of small trees is necessary for accurate calculation of gross production, total carbon and/or biomass of forest stands. The abundance of small trees can also be used to predict ingrowth into larger tree diameter classes. We present a method of predicting numbers of trees in small diameter classes using diameter distributions of larger trees in stands. A truncated two-parameter Weibull distribution was fit to large tree diameters (diameter at breast height (d.b.h.) ≥ 9.0 cm). These parameters were then used to predict the number of small trees in d.b.h. classes smaller than 9.0 cm. Three methods of predicting densities of small trees were used: (1) an extrapolation of the truncated Weibull to a full two-parameter Weibull distribution; (2) a modification of the Weibull using an empirical estimate and (3) a combined approach. While the full two-parameter Weibull distribution generally fitted the distribution of small trees, densities were typically under-predicted. The empirical method (i.e. method 2) produced the best predictions of small tree densities, with a root mean square error of 132 trees h –1 (28 per cent of mean small tree density). Overall, predicting the distribution of small trees using the distribution of large trees worked very well in this study.

Description: As a result of escalating demands for wood and parts of trees for use as biofuels and energy generation, there is growing interest in increasing forest biomass production. The objective of this study, therefore, was to investigate whether the physical properties and modulus of elasticity (MOE) of Scots pine ( Pinus sylvestris L.) juvenile clearwood change in response to different silvicultural treatments (pre-commercial thinning and fertilizer application) in 22- to 25-year-old trees. We achieved this by measuring short-term mechanical properties and using X-ray densitometry. The results show that the MOE and latewood density were not affected by any treatment. The earlywood density and the percentages of earlywood and latewood were affected by the treatments. Fertilization increased ring width and the percentage of earlywood but decreased the percentage of latewood. Pre-commercial thinning also increased ring width and the percentage of earlywood, and decreased the percentage of latewood, but did not affect earlywood density. Furthermore, our results suggest that the MOE of wood is not affected by the different treatments as long as the cambial age and ring width are the same and that fertilization should be considered as a factor that increases the site index where intra-ring properties are concerned.

Description: This paper quantified the soil organic carbon (SOC) concentration, bulk density, depth and carbon (C) stocks of 24 afforested peatlands. We found that the peat bulk density does not increase with depth, as has been previously noted in the literature. The depths of each different peat type were found to vary widely with means of 192 ± 100, 145 ± 130 and 127 ± 100 cm for raised bogs (RB), high-level blanket bog (HLB) and low-level blanket bog (LLB), respectively. Based on the full-surveyed depth, we estimated carbon densities of: 1160 ± 520 Mg C ha –1 for RB peat; 775 ± 590 Mg C ha –1 for HLB peat and 705 ± 420 Mg C ha –1 for LLB peat. We found peat depth and peat type to be significant predictors of peat carbon density and present pedo-transfer functions for carbon density based on these predictors that will help to improve future peat C stock estimates. We suggest that due to the similarities between the carbon densities of the HLB and LLB, they can be analysed as one group for accounting purposes and future C stock estimates.

Description: Recent studies have emphasized the nutritional interest of the fruits of strawberry tree ( Arbutus unedo L.), a species traditionally gathered in the Mediterranean region. Since fruit production in this species has been scarcely studied, we aimed to assess its local fruit supply in terms of fruit mass and fruit abundance. We carried out a 2-year study in two representative sites from continental and temperate regions of Central and Western Spain, respectively. Tree size, tree density and meteorological data were considered. The aged small population at Site 1 yielded 6.42 ± 1.19 kg per tree (46 ± 19 kg ha –1 ). The young large population from resprouts at Site 2, where forest management practices related to cork extraction have favoured shrubby growth forms, yielded 2.61 ± 0.42 kg per tree (539 ± 60 kg ha –1 ). Annual differences in fruit production per tree were recorded at Site 1, characterized by a Mediterranean climate with more severe continental traits than those at Site 2. This original data on wild fruit production may contribute to assessing the yield potential of this species for both sustainable use and cultivation purposes.

Description: This work investigates Aleppo pine performance under severe drought conditions according to seedling size and nutritional status, with special emphasis on potassium. The interaction of drought ameliorating measures such as hydrogels is also studied. Seven fertilization treatments applied in two nursery locations provided 14 stocklots, resulting in different seedling sizes for each nutrient concentration and vice versa. Stocklots were tested in a greenhouse experiment and a harsh site plantation experiment. In the greenhouse, seedlings given two hydrogel doses (0.01 and 0.1 per cent w/w) plus a control were allowed to dry and survival and soil moisture were measured. In parallel to this trial, the effects of hydrogel dosage, brand and soil texture on soil water properties were tested in a laboratory. Results show that large stock survived significantly better than conventionally sized stock in both experiments: 37 and 27 per cent more in the greenhouse and harsh site, respectively. Despite presenting wide variation, macronutrient concentration was not related to survival for a given size. Hydrogel effect on soil water was different according to factors, although in all cases, its effect diminished at suction tensions higher than 30 kPa. Results demonstrate the overriding effect of size over nutritional status on seedling survival in harsh environments.

Description: Balsam fir sawfly ( Neodiprion abietis (Harris)) has become a serious pest of young managed balsam fir ( Abies balsamea (L.) Mill.) stands in western Newfoundland, Canada. During 1991–2008, a total area of 561 000 hectares was moderate to severely defoliated. We quantified impacts (growth and survival) using data from permanent sample plots (PSPs) and dendrochronology and related these impacts to defoliation severity determined from aerial defoliation data, in order to provide input into a Decision Support System. We analyzed 67 Newfoundland Forest Service PSPs, selected based on severity of defoliation (classes 1–6), stand age and management interventions (pre-commercially thinned vs natural) and measured before and after defoliation (1996–2008). We used Bayesian statistics to combine information from different sources, each having their own limitations and associated uncertainty. No mortality was observed in immature plots 12 years after defoliation, but survival was 54 per cent lower in mature defoliated than in non-defoliated plots. Plots in defoliation class 1 (1 year of moderate, 30–70 per cent, defoliation) showed 22 per cent cumulative growth reduction and complete recovery to pre-defoliation growth increment after 5 years. Plots in defoliation classes 2–6 (one to three consecutive years of severe, 71–100 per cent, defoliation) had mean cumulative growth reductions of 26–40 per cent and did not recover to pre-defoliation levels even 9 years after defoliation ceased. Natural and thinned plots responded similarly to defoliation severity. These results suggest that proactive control measures need to be implemented since impacts are severe, even with only 1 year of severe defoliation.

Description: The significance of grey alder ( Alnus incana (L.) Moench.) as a fast-growing renewable source for energy and wood production has increased during the last decade. The aims of this study were to: (1) estimate the incidence of stem decay in A. incana stands, (2) measure the extent of decay within individual stems, (3) estimate the impact of decay on wood yield and (4) identify decay-causing fungi. In total, 4344 recently cut A. incana stumps were examined on 46 clearfelled areas in different regions of Latvia. The incidence of decayed stumps varied from 1 to 54 per cent. In addition, 175 living trees were cut to measure the extent of decay within the stems. The length of decay columns varied from 0.4 to 20.6 m and that of spongy rot from 0 to 18.0 m. In total, 354 isolates representing 70 fungal taxa and 1129 isolates representing 131 fungal taxa were obtained from decayed stumps and living stems, respectively. The present study shows that decay and associated fungi are important factors determining biomass production and quality in A. incana stands and that their impact should be seriously considered when cultivating this tree species in the future.

Description: Our study used ‘stand structures’ and ‘ecological indicators’ as inferences to managing dry Douglas-fir ( Pseudotsuga menziesii (Mirbel) Franco) forests for timber, biodiversity and range habitat attributes at 10–12 years after partial harvesting. Forest structures included densities and sizes of Douglas-fir and species and structural diversity of total conifers. Ecological indicators included cattle forage species in the understorey vegetation and three small mammal species: a closed-canopy specialist, the southern red-backed vole ( Myodes gapperi Vigors) and two early successional species, the long-tailed vole ( Microtus longicaudus Merriam) and heather vole ( Phenacomys intermedius Merriam). Harvesting treatments were across a gradient of historical cut, individual tree selection and patch cut sites in the upper Interior Douglas-fir (IDF dk ) biogeoclimatic zone near Summerland, British Columbia, Canada. Small mammal populations were sampled from 2006 to 2008. Closed-canopy forest structure seemed to maintain populations of red-backed voles in the harvested sites. Development of understorey vegetation in harvest-origin openings was similar across the levels of partial cutting and provided at least five plant species for cattle forage. Patches of grassland and shrubland in all treatment sites maintained viable populations of long-tailed voles and heather voles. These three small mammal indicators represent both late and early successional conditions in these IDF forests, which need to be managed for multiple objectives. Long-term monitoring of indicators will verify relationships with the components of biodiversity that they represent.

Description: Drought is a significant threat to forest health and the establishment of productive tree plantations. There is therefore great interest in understanding the mechanisms underpinning drought responses in forest trees. This review considers the means by which plants in general, and forest trees specifically, both detect and respond to water limitation. The review focuses on molecular-level responses to a drought stimulus, with an emphasis on responses that involve genome-wide reconfigurations in transcript abundance and protein complement in forest trees. A historical view of the molecular analysis of such responses shows a remarkable transition from understanding the impact of drought on individual genes to a more comprehensive picture of the suites of genes and proteins that constitute a drought response. Attention is paid to how this understanding might further the aims of preserving forest health and improve plantation productivity. The review suggests that genome-wide analysis of forest tree drought responses can be leveraged to provide new tools for conservation of adaptive variation and targets for selective breeding or directed modification of forest tree genotypes that can better contend with future drought scenarios.

Description: China’s collective forest tenure reform will have a profound impact on the livelihoods of rural people. For the equitable implementation of reform, rural smallholders need sufficient knowledge and understanding of the opportunities and limitations offered by reform. Here, we examine rural smallholder's awareness and attitude towards the reform, across the socio-economic range, in three villages of Zhang Guying Township, Hunan province. Income level and educational background played a consistent role in knowledge and understanding of the reform, as people with low income and no formal education were more likely to be unaware and have no clear understanding of the reform. Additionally, low-income rural smallholders were more likely to convert forest to cash crops, undercutting the central government's stated objectives for the forest reform to improve forest condition. Given our results, the government needs to ensure equitable distribution of information, specifically targeting low-income villagers without formal education. The strong disparity in knowledge and understanding between wealthy and poor creates a situation where the wealthy effectively benefit from the reform, while the poor miss its opportunity. This inequality has great potential for generating future unrest and conflict and for damaging forest condition due to unsustainable or uninformed practices.

Description: Long-term dynamics of selection (plenter) forests and corresponding virgin forests in NW Balkan countries (Slovenia, Croatia, Serbia, Bosnia and Herzegovina and Montenegro) were examined by assessing changes in diameter structure, stand volume and tree species composition. The parameters were aggregated at the landscape spatial scale, and the intensity of changes in diameter structure and tree species composition was measured by the index of dissimilarity. It was hypothesized that structure and composition of selection forests and virgin forests remained rather stable over several decades. Our study revealed pronounced dynamics in the observed parameters. However, these changes were divergent; in most study areas, increases of stand volume and large-diameter trees were observed, and in selection forests, the proportion of silver fir in the total stand volume decreased in three study areas and increased in two. Changes in diameter structure and tree species composition of the virgin forests were relatively less pronounced. In selection forests, an increasing proportion of mid-shade-tolerant Norway spruce and a constant proportion of light demanding sycamore, which is almost absent in virgin forests, were observed. The great capacity of the selection system to create stands of different structure and composition may be an important advantage in increasingly unpredictable economic, social and environmental conditions.

Description: We report a new silvicultural approach that is well suited for the management of uneven-aged forests in which timber production is an important objective. The approach recognizes two main components in the stand, i.e. a fiber production component, which provides veneer/sawlog quality products from the high-quality trees (HQT), and an ecological component, which contributes to the overall ecosystem functioning through the lower value stems. The objective of the study was to verify if it is possible to sustainably harvest only HQT in northern hardwood (NH) and thereby produce a viable alternative to high-grading the stands. To do so, a simple stand growth simulator, based on empirical growth rates of HQT in Sugar Maple/Yellow Birch stands in southwestern Quebec, was combined with an optimization tool. The optimization parameters aimed to identify possible tree marking regimes (TMRs) under 10-year rotation partial cutting, which would ensure that the basal area of HQT was maintained for 40 years. Results suggest that sustainability is achievable starting from very different initial stand structures and the application of a wide range of alternative TMRs. We argue that this new approach is one way to apply emerging concepts in forest management, such as ecological integrity, attempts to emulate natural disturbance regimes and provides new possibilities managing for resilience and for adaptation to climate change.

Description: In the framework of sustainable forest management, measuring site quality and predicting site productivity remain a major forestry topic. Over the past years, it has been fostered by a number of site-growth modelling studies seeking to establish quantitative relationships between site index and explicit biophysical indicators. In addition, comparative modelling studies of site index and site productivity have highlighted limited accordance of their environmental determinism, questioning site index as a reliable indicator of site quality. Lastly, process-based modelling approaches have recently arisen as a means to predict site productivity over large regions. All these investigations have however drawn limited attention in recent syntheses. In this review, we provide an overview of the literature on these site-growth studies. Concepts and vocabulary related to site productivity are introduced. Taking regional studies as a baseline, we first highlight recent progress regarding the geographic areas encompassed, and the major role played by NFI programmes and spatialized environmental information. A trade-off between model accuracy and geographic extent is suggested, pointing out potential deficiencies in the modelling of site-growth associations, insufficient accuracy or resolution in climatic data, or uncontrolled factors in site-growth models that emerge on a higher spatial scale. Inappropriate use of biophysical classifications where environmental factors remain implicit is also emphasized. In a next step, we discuss early and most recent indications on weaknesses of the site index concept when applied over large regions, including its differential response to climate relative to site productivity, regional variations in site index curves, site index dependence on stand density and subsequently on regional silvicultural practices. The role of genetic structure of tree populations and its integration into site-growth studies is also reviewed and discussed. The interests, limits and recent advances of process-based models as an alternative to evaluate site productivity are considered, as they may overcome some of the previous limitations. We last draw challenges and perspectives on the issue. We suggest that the accuracy – and the need – of site index as a founding concept of forestry science is questioned, by building direct productivity–environment relationships based on NFI databases as a realistic option at hand. We formulate perspectives regarding the accuracy, resolution and enlargement of environmental indicators currently used, the inclusion of information on genetic structure of tree populations in the context of adaptation to future climate change, as well as the use of site productivity models in forest management.

Description: It is necessary to evaluate how large seedling stock, used as an alternative to chemical herbicide for vegetation management, interacts with the timing of mechanical release (MR) and if use of such stock offers a broader window of intervention for release than conventional stock. Such a context is present in Quebec (Canada), where chemical herbicides were banned from use on public lands in 2001. We thus evaluated the impact of delaying MR on the performance of large spruce seedlings established in a gradient of vegetation zones and competition environments. Fourteen experiments were conducted in Picea glauca or P. mariana plantations in the temperate hardwood (TH), temperate mixedwood or boreal mixedwood vegetation zones. On each site, we established a completely randomized block design with 5–8 replicates, each divided into four plots: (1) control; (2) MR applied the year during which light availability to the planted seedlings averaged 60 per cent of full sunlight (EARLY); (3) MR at EARLY + 1 year (LATE1); and (4) MR at EARLY + 2 years (LATE2). Vegetation data collected in controls 8 years after MR was submitted to a correspondence analysis to group the sites according to their competing species dominance. Seedling responses to the timing of MR, 5–8 years after treatment, varied across competing vegetation dominance, vegetation zone or a combination of both. On sites where intolerant hardwoods were dominant, postponing MR 1 year after light availability had reached 60 per cent of full sunlight had a positive effect on seedling dimensions, especially in the TH zone. However, the LATE2 treatment resulted in significant stem volume losses on these sites. Whereas treatment effects were limited on ericaceous dominated sites, MR promoted seedling growth on sites dominated by shrub/herbaceous species, with no difference between EARLY, LATE1 and LATE2.

Description: Over the last 25 years, greater understanding of natural dynamics in the boreal forest has led to the integration of forest ecosystem management principles into forest policy of several Canadian provinces and, in turn, to greater interest in developing silvicultural treatments that are grounded in natural stand-level dynamics – often referred to as natural disturbance-based silviculture. As a result, alternative silvicultural practices including variants of partial cutting are increasingly being applied in the boreal forest as an approach to balancing economic and ecological management objectives. While the numerous benefits of partial cutting reported in the literature are acknowledged, the objective of this paper is to provide an overview of factors or constraints that potentially limit the application of these practices in boreal Canada in the context of forest ecosystem management and natural disturbance-based silviculture. Among constraining factors, numerous studies have reported elevated mortality rates of residual stems following partial cutting, initial growth stagnation of residual trees, problems related to recruitment of desirable species and, on certain flat or lowland sites, risks of long-term decline in site and stand productivity. A number of operational challenges to partial cutting in the boreal forest are also presented and several avenues of research are proposed.

Description: In 1898, François de Liocourt published a manuscript ‘The management of silver fir forests’, which is now considered a seminal paper on the subject of uneven-aged silviculture. The objective of this paper is to review de Liocourt's manuscript and examine its main findings and how they have subsequently been interpreted. De Liocourt's study examined data from seven stands dominated by European silver fir ( Abies alba Mill.) close to Gérardmer in northeast France managed using the selection system. He observed that the diameter frequency distributions from the stands all had a characteristic shape and were very similar. He also found that it was possible to derive a frequency distribution that closely resembled those found in the forests using the mathematics of number sequences. These findings were considered by de Liocourt to suggest more precise methods of managing these forests. Subsequently, the paper has been interpreted in a number of different ways, not all of which are accurate. These discrepancies are examined but all authorities who have referenced de Liocourt's paper should be congratulated for their desire to acknowledge the importance of this influential study.

Description: Management guides for uneven-aged forest stands periodically need to be revisited and updated based on new information and methods. The current silvicultural guide for uneven-aged spruce-fir management in Maine and the northeast (Frank, R.M. and Bjorkbom, J.C. 1973 A silvicultural guide for spruce-fir in the northeast. General Technical Report NE-6, Forest Service. U.S. Department of Agriculture) presents two options for each of three different cutting cycles, and all guides are based on a negative exponential distribution for the number of trees by diameter class. While this guide claims to be optimal, it will be demonstrated that it is not necessarily optimal in any commonly accepted sense and is overly restrictive in its adherence to the negative exponential model of stand structure. We review a methodology that allows the objective determination of optimal stocking guides for uneven-aged stands that can be tailored to the individual stand and provides consideration for a number of alternative objectives and cutting cycles. These guides do not necessarily conform to the strict negative exponential distribution. They also suggest residual basal areas somewhat lower than those recommended by the current spruce-fir silvicultural guide for the northeastern USA.

Description: Foresters influence short- and long-term development of plant neighbourhoods, stands and landscapes by their management practices. In the past, most of these practices have aimed to homogenize the composition and structure of stands for efficient wood production. This publication provides an overview of and guidance on how to recognize and efficiently utilize opportunities to modify silvicultural practices, with the goal of increasing species diversity and spatial variability within stands and landscapes at minimum cost. We suggest a procedure for selecting candidate treatments that might be used in this way. We further suggest that multi-scale evaluations (e.g. different objectives, such as economic vs ecological goals; different time frames from short-term to rotation lengths; and longer, different spatial scales from plant neighbourhoods to landscapes) can highlight opportunities to increase species diversity and spatial variability during implementations of ‘standard’ forest management practices. For example, opportunities may derive from situations where management practices did not achieve their intended goals or where natural disturbances can be viewed as stimuli that initiate opportunities to increase heterogeneity. With modifications, silvicultural responses to such conditions can provide efficient, low-cost (or even cost saving) means to increase species diversity and spatial variability. Using replanting, treatment of ‘minority’ species, variable spacing guidelines, and other examples, we show how varying the spatial and time scales of evaluations for such modified treatments can influence conclusions about costs and ecological impacts. Consequently, the choice of evaluation scales can be a deciding factor in whether treatment modifications are considered as economically justifiable ways to achieve a suite of diverse objectives.

Description: An uneven-aged silviculture experiment was established in second-growth peatland black spruce ( Picea mariana [Mill.] B.S.P.) stands in the boreal forest of northeastern Ontario, Canada in 1994. Three harvest treatments along with an unharvested control were applied in three replications. Fifteen-year results indicate that light- and medium-intensity harvest treatments maintain stand structure suitable for the continued application of uneven-aged silviculture treatments. Based on basal area growth trends and the development of stand structure, a cutting cycle of 20–25 years appears to be feasible for these treatments. Future harvests will likely yield a higher proportion of larger diameter trees with a greater value. The heavy harvest intensity treatment will result in a greater fluctuation of the growing stock and a longer cutting cycle. Without cutting treatments, the control treatment may eventually develop a stand structure that is unsuitable for the implementation of uneven-aged silviculture.

Description: Historically, tree biomass at large scales has been estimated by applying dimensional analysis techniques and field measurements such as diameter at breast height (dbh) in allometric regression equations. Equations often have been developed using differing methods and applied only to certain species or isolated areas. We previously had compiled and combined (in meta-analysis) available diameter-based allometric regression equations for estimating total aboveground and component dry-weight biomass for US trees. This had resulted in a set of 10 consistent, national-scale aboveground biomass regression equations for US species, as well as equations for predicting biomass of tree components as proportions of total aboveground biomass. In this update of our published equation database and refinement of our model, we developed equations based on allometric scaling theory, using taxonomic groupings and wood specific gravity as surrogates for scaling parameters that we could not estimate. The new approach resulted in 35 theoretically based generalized equations (13 conifer, 18 hardwood, 4 woodland), compared with the previous empirically grouped 10. For trees from USDA Forest Inventory and Analysis Program (FIA) plots, with forest types grouped into conifers and hardwoods, previous and updated equations produced nearly identical estimates that predicted ~20 per cent higher biomass than FIA estimates. Differences were observed between previous and updated equation estimates when comparisons were made using individual FIA forest types.

Description: For this study, 18 permanent research plots in Switzerland with an area between 0.5 and 2.5 ha that have been installed between 1905 and 1931 were analysed using annuities. The plots cover a wide range of uneven-aged forest-types from pure Norway spruce to classical single-tree selection (plenter) forests dominated by Silver fir in different elevations (575–1810 m a.s.l). The areas have been managed according to an uneven-aged silvicultural system and growth and yield characteristics have been assessed on a single-tree basis every 5–11 years. Net revenues of timber harvesting were computed as a time series from the installation of the plots until today and transformed into net present values and subsequently into annuities for each assessment interval. Three types of annuities: (1) for cutting cycles; (2) forward; (3) backward for the whole assessment period were calculated together with internal rates of return. The results display that annuities were usually positive with an interest of 2 per cent. High elevation (〉1400 m) Norway spruce dominated forests as well as heavily overstocked (〉900–1000 m 3 ha –1 ) plots showed the lowest or even negative annuities. The reduction of overstocks lead in the mid-term to an increase, but resulted in a short-term decrease of the annuities. For many of the research plots, especially those in higher elevations, there is a trend towards an increase of the annuities over time. The highest annuities were found in Silver fir dominated selection forests with a growing stock close to or slightly above an equilibrium structure. The backward calculation of the annuities improved for some plots the problem of the strong influence of the value of the initial growing stock. Implications for uneven-aged silviculture as well as for the analysis of the economic performance of uneven-aged and even-aged forests and the application of annuities are discussed in the paper.

Description: Concern exists among managers and researchers that sugar pine ( Pinus lambertiana ), a valuable, moderately shade-tolerant timber species, regeneration appears to be declining. Management and restoration require understanding factors leading to sustained sugar pine regeneration growth and overstorey recruitment. The primary research objective was to identify factors influencing sugar pine regeneration height growth. Data were collected on sugar pine regeneration, including height growth and stand characteristics across six managed and eight unmanaged stands in the Lake Tahoe Basin, CA and NV, USA. Individual tree- and stand-level analyses were conducted using non-parametric statistical comparisons and regression. Results indicated low mean height growth rates and no relationship between canopy closure and either height growth or management history. Individual sugar pine seedlings grew significantly taller under unmanaged stand conditions with higher canopy closures while sapling growth did not differ statistically by management history. Individual tree-level height growth models never explained more than 35 per cent of the variation. Stand-level models explained over 50 per cent of the variation with fewer variables than the individual tree-level models. More research should be conducted to determine whether the regeneration that is persisting in the understorey would respond positively to more aggressive uneven-aged silvicultural treatments designed for enhancing understorey pine growth.

Description: Height–diameter models are commonly used in forestry for the imputation of missing tree heights and as such underpin the calculation of many fundamental mensurational quantities needed to characterize forest growth and yield. Despite their importance, there are still no published height–diameter models for Britain. This paper reviews the uniform height curve methodology for modelling the height–diameter relationship in even-aged stands and proposes a way to adapt it for use in Britain. According to this methodology, a height–diameter model for individual trees in a stand can be fully characterized in terms of one global parameter uniquely defined for a given species and geographical region and one local parameter specific for each stand and measurement occasion, which can be easily estimated from knowledge of the characteristics of an average tree. The methodology was evaluated using permanent sample plot data for Sitka spruce ( Picea sitchensis (Bong.) Carr.) and proved able to describe the height–diameter relationship reliably and with good accuracy. The flexibility and ease of application of this approach are ideal in all those applications (e.g. within a growth simulator) where more precise statistical calibrations cannot be used.

Description: Selective browsing of saplings is an unavoidable consequence of high density of wild game and can lead to stand homogenization. To ameliorate the effects of economic risks associated with decrease in species diversification – for example, decreased flexibility in relation to the timber market or increased susceptibility to calamities – compensation payments can be helpful. The risk components in forest economics are now well described. However, even though soil and climate conditions are among the most important factors determining financial gain or loss from forest management, differences due to variations among forest sites are rarely considered in economic analyses. In order to consider the impact of site variation on the financial effects of game browsing, this study focused on financial results of forest stand models considered representative for average site conditions for each of the 15 growth regions in Bavaria, Germany. Using the Silva 2 growth model, the average growth of spruce ( Picea abies (L.) Karst.) and beech ( Fagus sylvatica L.) was simulated to consider return–risk ratios of mixed and homogenized stands – thus to compare target and deviating states. The investigation was divided into two parts: first, as many forest decisions are dependent on financial outcomes, the analysis of the financial impact of varying site conditions began by calculating the annuities. Second, it was important to see what influence site conditions might have on compensation payments. The results showed that fluctuations in spruce growth rates among 15 growth regions of Bavaria were much higher than those for beech. Because of the loss of beech, when calculating necessary risk compensation levels, the results were largely dependent on the variations in beech growth and the financial risk level of spruce – both due to differences in site quality.

Description: We examined the performance of older even-aged plantations to check the validity of three of the most fundamental tenets of forest site productivity: the height–age site index, Eichhorn's rule and the thinning response hypothesis. We assessed the condition of 〉14 000 trees in 60 randomly selected plantations to determine whether the stands were following site productivity expectations and growth and yield projections. We evaluated the health status of all the trees by height class (〈2, 2–4 and 〉4 m tall). We found strong evidence that older, managed plantations are subject to damage agents that are targeting dominant trees. We found natural ingress was not filling voids created by loss of planted trees. Our findings were clearly in conflict with the assumptions of low and stable levels of loss of dominant trees in aging plantations. The tendency of forest growth models to emphasize stability and predictability needs to be reconsidered. The assumptions driving the traditional forest growth models were developed largely in the absence of biotic and abiotic damage agents and certainly prior to the knowledge of climate change. The combined influence of these two drivers must be better accounted for in growth models through more intensive stand and forest level monitoring.

Description: The method of predicting an unknown target probability distribution via a Gram–Charlier A-series expansion (GCAE) of a user-defined base probability function and cumulants of a known distribution of an auxiliary variable is demonstrated in two applications. Both applications concern predictions of the distribution of tree stem diameters with cumulants of airborne laser scanning (ALS) canopy heights and an index of canopy density as predictors. All predictions were generated in a leave-one-out cross-validation scheme, and statistical inference was based on 100 stochastic predictions of the tree sizes in 308 plots of 400 m 2 . The mean and variance of GCAE-predicted distributions were rarely significantly different from actual values, yet between 19 and 32% of the predicted GCAE distributions were significantly different from the actual distribution. The rejection rate with predictions generated from a simpler DECILE method was, on average, 2.5% lower. GCAE is still recommended due to its potential usefulness. Cumulants of ALS canopy heights are independent of plot area and effective for area-based least-squares predictions of forest inventory variables.

Description: Observations in nature suggest a particularly high risk of wind-induced forest damage near stand edges. Unsteady processes caused by strong gusts from the atmospheric boundary layer are likely to play a major role. To gain more insight into the corresponding flow behaviour, wind-tunnel experiments were made with artificially generated 3D wind gusts, produced by short inductions of pressurized air, combined with time-resolved particle-image velocimetry measurements. In the near-edge region of the laboratory forest, the developing gust-induced disturbance at canopy, the top shows a wave-like shape in the measurement planes. The highest values of downward momentum flux above the canopy were measured 1.5 to 4 tree heights behind the leading edge. This was found to be caused by an edge-induced primary vortex, which formed behind the edge and directed high momentum fluid from the overflowing gust into the canopy.

Description: Programmes for forest habitat protection and some certification schemes restrict forest owners' choice of regeneration methods, even in continuous-cover systems such as the use of the shelterwood system in beech ( Fagus sylvatica L.) forests in Denmark. The aim of this study is to reduce environmental pressure on e.g. groundwater or to protect species dependent on deadwood or undisturbed soils, which is beneficial/important from a welfare economic perspective. Such restrictions come at a cost to both the forest owner and society. Using a case study approach, we investigate the possible financial losses from placing such restrictions on current shelterwood beech management practices. A part of the restrictions implies lower input, intensity and costs in regeneration activities, but this is outweighed by potential future losses arising from incomplete regeneration and prolonged regeneration phases. The cost in terms of present value reductions of a mature stand may be up to 10 per cent (with an interest rate of 3 per cent) but in many cases is much less. Another set of restrictions implies leaving single trees for natural aging and decay, and we estimate the costs of such measures too.

Description: Forest management practices in European temperate and Mediterranean regions have frequently exploited coppicing and pollarding – two silvicultural techniques that promote vegetative regeneration. These practices were historically very common with trees being cut at ground level or above the level of browsing to produce shoots, which were harvested for a variety of uses. Many habitats created from such traditional management are now recognized as areas of high conservation value, being rich in biodiversity. Yet their persistence has been under threat after these practices suffered a decline in the nineteenth century. The focus of this review is to synthesize information on coppicing and pollarding from the ecosystem to the molecular level and to highlight characteristics that may help or hinder climate adaptation. Understanding the benefits and hazards of exploiting vegetative regeneration is the first step in assessing whether promoting this means of reproduction could be exploited for conservation by increasing forest persistence in unfavourable future climate conditions. Practical management recommendations are given and suggestions are made for future research.

Description: Surveys of ash trees along the major motorway routes leading away from the city of Moscow during July 2013 indicated that emerald ash borer ( Agrilus planipennis ) was well established up to 235 km west of the city and 220 km to the south. Over the last 4 years, the beetle has spread in these directions at an average rate of 30–41 km year –1 , which cannot be explained by natural dispersal alone and implies that human-assisted transport is contributing significantly to the spread of the pest, probably via the hitchhiking of adult beetles on vehicles. The European common ash ( Fraxinus excelsior ) is uncommon in Moscow and in the boreal forests to the west and north, but those trees that are present suggest that this species is not killed as rapidly by A. planipennis as North American ash species and that it may need to suffer a degree of stress before it succumbs rapidly to infestation. Nevertheless, A. planipennis is a major threat to F. excelsior , and south of Moscow, where the beetle has become established in natural broadleaved woodlands in which F. excelsior is a major component, many of the ash trees are suffering severe dieback and mortality. The abundance and almost continuous distribution of F. excelsior in these woodlands means that A. planipennis now has the opportunity to spread unhindered on a broad front to other countries in Europe.

Description: The effects of tree species on soil properties have been attracted much attention, but the specific responses of labile soil organic carbon (SOC) and microbial activity to changes in tree species of subtropical forest ecosystems remain unknown. In this study, we investigated the labile fractions of SOC from three different single species plantations, namely Pinus massoniana (PM), Cinnamomum camphora (CC) and Schima superba (SS) in subtropical China. Specifically, we analysed the soil microbial biomass C (MBC), dissolved organic C (DOC) and permanganate-oxidizable C (POC), soil respiration, and activities of six enzymes in surface mineral soil (0–20 cm). The MBC, POC and soil respiration, as well as the activities of urease, acid phosphatase and polyphenol oxidase significantly differed among the three plantations in the study. In contrast, changes in the DOC as well as the activities of invertase, catalase and cellulase were not significant. The CC soil exhibited the highest POC, DOC and urease activity. PM soil had the highest MBC, soil respiration and polyphenol oxidase activity, but also had the lowest POC, q CO 2 , urease activity and acid phosphatase activity. DOC and MBC were significantly correlated with the soil respiration. Urease activity was significantly related to the SOC fractions, except for MBC. Invertase and polyphenol oxidase activities were correlated with MBC. The results suggested that the tree species had different effects on the labile SOC and microbial activity and the observed differences seemed not to be explained by the differences in the litter quality.

Description: In forest ecosystems, disturbance intensity affects the ability of species with varying shade tolerances to successfully recruit into the overstory. Small openings (e.g. single treefall) perpetuate shade-tolerant species while larger openings (e.g. those created under group selection and other higher severity disturbances) enhance the abundance of shade-mid-tolerant and -intolerant species. Forty-nine modified group-selection openings in three size classes established during the winter of 2003/04 and 20 single-tree selection sites were re-evaluated in 2012 in order to determine: (1) how the densities of seedlings and saplings changed over time, (2) whether species composition differed between treatments and (3) whether the group-selection openings enhanced recruitment of underrepresented species, especially the mid-tolerant yellow birch ( Betula alleghaniensis ). Sugar and red maple ( Acer saccharum and Acer rubrum ) regeneration dominated at all sites and occurred in greater densities in the group-selection openings as compared with the single-tree selection sites. While yellow birch densities increased with opening size, survival and growth were likely inhibited by the drought conditions that have occurred since 2004. Ironwood ( Ostrya virginiana) and black cherry ( Prunus serotina ) also benefited from opening creation. Consequently, while openings enhanced the representation of mid-tolerant species, they did not greatly alter the developmental trajectory of this forest type.

Description: Mountain pine beetle (MPB) outbreaks within the previous 10–15 years have affected millions of hectares of lodgepole pine forests in western North America. Concerns about the influence of recent tree mortality on changes in fire behaviour amongst firefighters and fire managers have led researchers to attempt to quantify the effects on crown fire potential. In this paper we provide an up-to-date review and critique of research that has endeavoured to quantify the effect of recent MPB-caused tree mortality, during the red stage, on crown fire potential based upon quantitative descriptions of important crown and canopy fuel characteristics and simulation-based assessments of crown fire initiation and spread using operational and physics-based models. While significant progress has been made in characterizing the important variables affecting crown fire potential in recently attacked forests, we suggest that many of the conclusions drawn from simulation-based studies conducted to-date are suspect given the use of inappropriate and/or un-validated models. A systematic program of experimental burning, the monitoring and documentation of wildfires and prescribed fires, and better models of fuel moisture and fuel structure are urgently needed in order to properly assess crown fire potential in lodgepole pine forests recently attacked by the MPB.

Description: Whole-tree volume equations are in great demand due to the need to quantify the distribution of wood volume within trees for estimating whole-tree utilization potential. While main stem volume has been extensively studied, related to computing the merchantable timber volume of trees, the relative volume of branches has received much less attention. It is particularly challenging to quantify branch volume in trees with deliquescent branching architecture (i.e. hardwoods) where branching is complex and not strongly controlled by a dominant stem. Here, new mixed-effects cumulative volume profiles are presented that allow for simultaneous volume estimation of the dominant stem and whole tree from ground to the top of the tree. Cumulative branch volume can be estimated at different relative heights from the whole-tree and dominant stem profiles by simple subtraction. The models were developed from destructive sampling of 32 trees from a temperate hardwood forest in Michigan, US. The species in the sample were primarily American beech ( Fagus grandifolia Ehrh.) and sugar maple ( Acer saccharum Marsh.). The results produce whole-tree cumulative volume models that include all branches in trees and demonstrates the value of studying the whole tree even when the dominant stem is the object of interest.

Description: In many countries, timber harvesting from natural forests is accompanied by social conflict that governments seek to mitigate, often through the introduction of policy changes that reduce the forest industry's access to natural forest wood. Forest policy changes often have important implications for businesses and workers dependent on forest resources; however, the social impacts of such changes remain relatively unexplored. We conducted an ex post facto assessment of social impacts experienced by members of the forest industry in the Australian state of Western Australia following the introduction of three forest policy changes between 1999 and 2004. Results indicate that the process by which forest policy decisions were made, the nature of the resulting policy changes, and the actions people took in response, together contributed to three key negative social impacts: uncertainty, a perception of injustice, and financial stress. These impacts in turn led to diminished perceptions of industry security, thus discouraging business owners from investing in the industry, rather than encouraging investment, which was a key goal of the forest policy changes. The results highlight the importance of recognizing, avoiding and mitigating negative social impacts associated with policy changes, as these impacts can hinder the realization of policy goals.