ALBERT

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.

Description: Six experiments, initially established to investigate the effects of weed control on establishment of Sitka spruce ( Picea sitchensis (Bong) Carr.) were revisited 15–25 years after planting, and 6–22 years after weed control ceased. At three of the six experiments weed control resulted in initial benefits to growth and in some cases survival at Age 3, while no effect was evident at the other three sites. At mid-rotation, 15–25 years after planting, although there were no persistent effects of weed control on height or diameter growth, at three of the experiments there was a positive effect on survival. Projection of these mid-rotation survival effects to full rotation using a growth and yield model indicated that weed control may have the potential to increase final yield and carbon storage at some of these sites in the longer term. The existence and magnitude of benefits from weed control were highly site dependent. This study demonstrates that there is clear potential for early weed control to increase the cost-effective carbon storage and hence the climate change mitigation potential of some British Sitka spruce forests, particularly on nutrient rich sites and with stands that are subsequently thinned. The development of dedicated long-term weeding trials in the UK, including thinned stands where cumulative volume removed in thinning is recorded, is required to confirm this.

Description: Provenance trials provide an opportunity to develop transfer functions that can be used to assess the effects of climate change on tree growth. A transfer function is available for lodgepole pine ( Pinus contorta var. latifolia ) in British Columbia, Canada, that predicts relative height (site height of a population divided by the site height of the local population) as a function of mean annual temperature transfer distance and mean annual temperature of the provenance. This model is modified to improve its fit and address some deficiencies. A dataset consisting of 2276 height observations from 136 populations planted at 40 test sites was fitted to a two-variable power/exponential function. Mean coldest month temperature and mean summer precipitation transfer distances were the predictor variables, and relative height at the age of 35 was the response variable. The transfer function was linked to a lodgepole pine height-age model to create a dynamic system that can be used to evaluate the effect of climate change on site height growth. The system can then be used to mitigate the effect of climate change on lodgepole pine site height growth by determining the expected height of seed from various provenances at the end of the rotation and selecting the optimal seed source. For an example stand, climate change is expected to reduce site height by ~0.77 m over an 80-year rotation. However, this reduction can be fully mitigated by planting the optimal seed source.

Description: We used mapping-grade global positioning system (GPS) receivers to examine post-processed horizontal measurement accuracies during nine separate visits to six sites that each contained 10 test points within a second-growth Douglas-fir forest. Our primary objective was to compare GPS accuracies resulting from two different receiver configurations that vary in productivity and accuracy. A secondary objective was to determine how accuracies would change with recording interval (whether we averaged 1, 5, 10, 30 or 60 positions). We also examined which environment- and GPS-related factors most influenced GPS accuracy. Root mean square error (RMSE) at the 95 per cent confidence level (RMSE 95 ) using the ‘default’ GPS setting (position dilution of precision (PDOP): 6; SNR 39; minimum elevation 15°) was 6.0 m, while RMSE 95 using ‘maximum’ settings (PDOP: 20; SNR 33; minimum elevation: 5°) was 8.0 m across all sites and recording intervals. Using default settings, RMSE 95 decreased from 7.3 m when averaging one position to 4.4 m when averaging 60. For maximum settings, RMSE 95 decreased from 9.1 to 6.5 m. Our best models selected basal area, dilution of precision and weather, but not terrain. When using default settings the average wait time was 55 sec when collecting one position and 236 sec when averaging 60. Using maximum settings, average wait time was 8 sec when collecting one position, and 74 sec when averaging 60 positions. The errors that we report are acceptable for many forestry applications. These results should help users to balance productivity with accuracy when using mapping-grade GPS receivers in second-growth Douglas-fir forests.

Description: Weeds are an important limiting factor in the development of pedunculate oak seedlings. Weed control is very important on regeneration areas, particularly in the initial stages of young growth development, when the adverse effects of weeds on oak are greatest. Effective weed control should be based on the combination of several different measures. However, because of manpower shortage, high labour costs and large areas, forest managers frequently decide to use herbicides to control weeds. On oak regeneration areas, a major problem is often broadleaved weeds that grow vigorously. Post-emergence herbicides nicosulfuron, bentazon, imazamox and tribenuron-methyl were monitored in broadleaf weed suppression in pedunculate oak stands during the regeneration process. Field studies were performed at two sites during three growing seasons, i.e. herbicide selectivity was examined on 1-, 2- and 3-year-old seedlings. The study results show that the number and fresh and dry weights of weeds were significantly reduced by tested herbicides in treated sample plots when compared with control plots. The herbicides tribenuron-methyl and bentazon had phytotoxic effects on oak seedlings. In contrast, nicosulfuron and imazamox did not show phytotoxic activity against the seedlings and can be applied in weed control in regenerated pedunculate oak forests.

Description: In Finland, pruning of Norway spruce has recently gained increasing interest, in spite of the past negative results associated with fungal infections. The aim of the study was to compare the growth of pruned and unpruned Norway spruce and to determine the effects of pruning on the defects in wood and visual grade distribution of the sawn boards. The material consisted of 60 pruned and 20 unpruned trees. The pruning occurred 20 years before the felling. Approximately 25 per cent of the living crown was removed, but the pruning did not reduce either the diameter or the height growth of the trees. The pruning decreased the number of knots on a board surface by 10 knots per board, i.e. 2–3 knots per metre of length of the board. In the outermost boards, the pruned trees had 67–75 per cent fewer knots. Discoloration or decay occurred in 12–17 per cent of the boards, but pruning did not increase the frequency of defects. Due to the presence of fewer and smaller knots, the quality distribution of the boards from the pruned trees was shifted towards the better quality classes. The results demonstrated that pruning will provide butt logs with a smaller knotty core and boards with higher value than logs from unpruned trees.

Description: The aim of this study was to compare the effects of fertilization and thinning on the growth rate and wood and tracheid properties of Scots pine ( Pinus sylvestris L.) in southern Finland. The study was based on two long-term experiments with two fertilization treatments (unfertilized and 150 kg N ha –1 every 5 years) and two thinning levels (delayed and intensive first commercial thinning) in a randomized block design. A total of 80 trees were sampled ~30 years after the onset of the treatments. Intensive thinning enhanced the radial growth of the remaining trees by 52 per cent compared with the delayed first thinning. Accordingly, the fertilization increased the radial growth by 37 per cent compared with the unfertilized trees. However, only small differences were found between the treatments in the earlywood/latewood ratio (3–9 per cent), wood density (2–8 per cent), tracheid diameter (2–5 per cent), cell wall thickness (0–10 per cent) and tracheid length (4–5 per cent). The results demonstrated that the prevailing fertilization and thinning treatments of Scots pine stands considerably enhance the growth rate but do not cause major detrimental changes in the wood and tracheid properties.

Description: Because wood density is an important indicator of the end-use mechanical properties of sawn timber, detailed knowledge of its variation is important for optimizing value in processing. The aim of this study was to develop a model for predicting wood density variation in plantation-grown Scots pine ( Pinus sylvestris L.) using position in the stem and radial growth increment as independent variables. Seventy trees, ranging in age at 1.3 m from 9 to 99 years, were sampled from 12 even-aged Scots pine stands in Scotland, UK. Pith-to-bark density profiles were obtained on 193 radial samples using scanning X-ray densitometry. We developed a mixed-effects model of average ring density (expressed as basic specific gravity) based on an exponential function of cambial age, height along the stem and annual ring width. Basic specific gravity ranged from 0.274 to 0.697, with a mean of 0.423, and increased rapidly from the pith until approximately rings 20–30, before stabilizing. In addition, there was a weak negative relationship between basic specific gravity and annual ring width, and for a given cambial age, basic specific gravity decreased with sampling height. The fixed effects of the final model were able to explain ~57 per cent of the within-stem variation in wood density (78 per cent if random effects were included). The final model is intended for integration into a growth, yield and wood quality simulation system.

Description: Crown dynamics affect tree cross-sectional growth by responding to individual traits and stand history and features, i.e. species, stocking, thinning, site quality or climatic conditions. Under this assumption we analysed two simple models that relate cross-sectional growth to the growth of stem length above the cross section in four species of Mediterranean pines. Cross-sectional growth was measured at breast height. The first model (Model 0) has no parameters, and specifies an isometric relationship between cross-sectional area and stem length. The second model (Model α), which was formulated to analyse Model 0, has one parameter. Neither of the two simple models requires knowledge of crown length, though Model 0 derives – under an assumption of constant crown length – from a more general model that relates cross-sectional growth to crown length dynamics. A mixed-effects modelling strategy was selected to fit Model α in order to incorporate fixed effects of species, and random effects to account for factors like ontogeny (tree effect), stand history (plot effect) and climatic conditions (growth period). Results indicate that Model α predicts better than Model 0 when the single parameter is expanded to take into account all these effects and indicate that the constant ratio between cross-sectional area and the length of stem predicted by Model 0 is one possible value within a ratio that changes over time as function of ontogeny, stand history and climatic conditions. On average the ratio is positive, indicating greater cross-sectional growth than height growth showing greater variation in stem formation. Inter-specific analysis indicated a less asymmetric behaviour in competition for pine species growing in water-stress environment

Description: Management targeting increased structural complexity requires not only targets but also mechanisms by which to create those target structures. We identified the most influential structural attributes and spatially explicit metrics for small-scale structural complexity using multiple linear regression at the beginning, end and over a 15-year period in two Norway spruce-dominated stands in southern Finland. Both stands had plots that exhibited an even-sized (ES) structure created through low thinnings and plots that exhibited an uneven-sized (UES) structure perpetuated through single-tree selection harvests. For both structure types, best models for structural complexity used a combination of non-spatial structural and/or compositional attributes and spatially explicit metrics that included the variation in tree size, tree size differentiation, tree density, stand basal area and spatial aggregation. Structural complexity in the ES structure type was mostly a function of tree size differentiation, whereas stand basal area and tree size differentiation were the most influential in the UES structure type. A conceptual model is presented to illustrate how spatial heterogeneity relates differently to small-scale structural complexity, which could be enhanced in ES structure types by increasing variation in size differentiation and in UES structure types by increasing variation in tree abundance.

Description: Carbon sequestration and wood volume production will be major objectives of future forestry projects. Optimization of these two objectives will require a better understanding of how management regimes affect stand average wood density and carbon fraction. Two contrasting coast redwood ( Sequoia sempervirens ) sites were chosen for analysis of volume growth rates and tree stem carbon sequestration rates under two management systems—even-aged and multiaged—each with various treatments. A young plantation showed high volume increment and stem carbon sequestration rates in all treatments with the highest in the control plots. Control plots in the plantation had peak periodic volume increment of 75.6 m 3 ha –1 year –1 and a maximum stem carbon sequestration rate of 16.08 tonnes C ha –1 year –1 . The multiaged stand in contrast had the lowest volume and carbon increment in the control plots at 11.97 m 3 ha –1 year –1 and 2.40 tonnes C ha –1 year –1 , respectively. In both the management systems, significant differences were observed in the carbon fraction (mass carbon per unit mass dry wood) of heartwood (HW) and sapwood (SW) at 0.5385 and 0.5293, respectively, implying that increasing the ratio of HW to SW will result in higher average carbon fractions. Carbon density varied between management regimes with the highest values occurring in the multiaged stand indicating the potential for enhancement of carbon sequestration through silvicultural prescriptions. Utilization of standard carbon accounting practices resulted in a systematic underestimate of stand-level carbon stocks for both systems studied of 26 per cent in the even-aged stand and 27 per cent in the multiaged stand.

Description: This paper reports an approach for estimating thinning-induced changes in N and P budgets in jarrah ( Eucalyptus marginata ) forest in the Wungong catchment of Western Australia. Two thinning strategies, herbicide injection and selective removal, were tested and nutrient budgets were constructed for soil, litter and tree biomass. The effects of thinning were evaluated based on pre-thinning biomass allocation and on reductions in biomass after thinning. Tree above ground biomass was 399 ton ha -1 , from which the selective logging removed 18.7 ton ha -1 or 5 per cent of the N and 4 per cent of the P. Thinning residues from stem injection of herbicide contained fivefold more nutrients than the ground litter. Top soil was the primary nutrient store but only 1–2 per cent of total N and P were in available forms. In contrast, fine litter materials in thinned sites may release 4.8–5.7 kg P ha –1 via leaching over the rainy months. Cut branches and dead stems stored 176 kg N ha –1 and 7.0 kg P ha –1 but would decompose over many decades. Our results indicate that both thinning strategies would increase nutrient cycling in the forest, while the implications of thinning-induced nutrient supply for the growth of remaining vegetation, understorey competition and ecosystem health need further examination.

Description: Attack by the white pine weevil has notably reduced Sitka spruce productivity in British Columbia (BC) (Canada) and western US. By the 1970s, the BC Ministry of Forests established provenance trials of Sitka spruce with the objective of detecting usable genetic resistance to weevil. These early trials reported significant weevil resistance and allowed the production of the first (F1) controlled-cross progeny generation with demonstrable weevil resistance (R) or susceptibility (S). This study reports results of the screening for weevil resistance and the levels of constitutive defenses of this F1 Sitka spruce progeny. Progeny from resistant parents (R x R progeny) sustained significantly fewer weevil attacks than progeny from susceptible parents (S x S progeny) or progeny with one resistant and one susceptible parent (R x S progeny). Individual and family heritability estimates of the weevil resistance were 0.5 and 0.9, respectively. Constitutive defenses, measured by resin canal and sclereid cell density in the cortex, were significantly higher in R x R progeny than in R x S or S x S progeny. We observed a negative correlation between the percentage of trees attacked in each cross and the average density of the resin canals or sclereid cells for each cross.

Description: Genetic research on the interactions of temperate tree hosts with pests and pathogens, and breeding for resistance or low susceptibility, are hindered by the long generation time and large size of tree species. Foresters need to be quick to exploit new technologies that may accelerate research and breeding programmes, and opportunistic in gaining maximum use from existing experimental tree plots. A fruitful approach may be to apply new genomic methods to the analysis of established provenance and progeny trials, seed orchards and clonal archives, where screening for pests and pathogens may occur. An important test case of this approach is underway in Britain with respect to ash ( Fraxinus excelsior L.) and the search for resistance to the dieback caused by Hymenoscyphus fraxineus (T. Kowalski) Baral, Queloz, Hosoya, comb. nov. This review examines: (1) the use of field trials for pathogen and pest resistance in forest trees, (2) how field trials may support the application of genomic technologies to tree health issues, (3) the extent of the field trial resource in Britain, (4) issues that constrain the use and maintenance of field trials, (5) an outline of possible experimental designs, (6) the use of natural systems and (7) funding of long-term trials. Application of the latest technologies may be critically dependent on the availability of well-designed and maintained, long-term, field trials that produce invaluable resources and results for decades.

Description: Both natural and managed forests are currently suffering from increases in damage by pathogens. Here, an evolutionary ecology approach is adopted to analyse the factors that influence the levels of pathogen damage experienced by forest tree populations and consider the conditions under which stable co-existence of trees and pathogens occurs in natural populations. The demographic and genetic responses of tree–pathogen systems to anthropogenic perturbations are explored to identify where the greatest threats to resilience lie. Problems caused by native pathogens are likely to arise as a consequence both of rapid climate change and of forest management practices that lead to increases in species density, drastic reductions in genetic diversity and planting outside the native range. The most serious threats to forest trees are posed by introduction of exotic pathogens derived from related exotic tree species. Recovery following spread of exotic pathogens is likely to be both slow and uncertain and may not be possible without intensive programmes involving rapid selection and widespread dissemination of genotypes resistant to the exotic pathogen.

Description: Our natural and commercially planted forests are currently facing an unprecedented threat from pests and pathogens. On the principle that ‘prevention is better than cure’, the policies and practices that influence forest management must aim to prevent epidemics rather than to fight them once they are established. Vigilance and strict security at national borders aim to prevent entry of pests and pathogens but experience shows us that this does not achieve total exclusion. Consequently, to improve the long-term resistance and resilience of tree populations to infection or herbivory, a more realistic and scientific approach may be to understand and use the resistance mechanisms that are naturally present in trees. Resistance trait variation may be genetically controlled and heritable. Populations therefore have the potential to respond to the selective pressure imposed by attack and, if the management and environmental conditions are right, adapt. This review outlines the mechanisms that trees use to defend themselves, the genetic and environmental control of these mechanisms, the subsequent phenotypic variation that we observe and how best to measure and use this to develop and maintain resilient tree populations. In order to ensure a more sustainable and stable future for commercial and native tree species there is a need to incorporate these approaches into forest management globally through collaboration between foresters and scientists and increased investment in relevant research trials.

Description: Agrilus biguttatus Fab. (Coleoptera: Buprestidae) is a European bark-boring beetle whose larvae feed in the vascular tissue of oak trees. Until recently, it was considered rare in Britain, but sightings have become more frequent and it is often found on weakened trees suffering from Acute Oak Decline (AOD). This rapidly acting syndrome is characterized by patches of dark sticky fluid exuding from cracks on the trunk, with areas of necrotic tissue beneath, probably caused by a pathogenic bacterial component. However, the frequent association of AOD with the larval galleries and distinctive adult exit holes of A. biguttatus has raised concerns that the beetle may be contributing to the AOD syndrome or hastening the mortality of affected trees. This review evaluates the potential role of A. biguttatus in the AOD complex. Information on the beetle's life cycle and ecology is assessed along with the apparent increase in its abundance and distribution in the UK, and likely mechanisms of host selection. Oak tree defences against the beetle are discussed, as well as risk factors influencing susceptibility. Research on related Agrilus species is reviewed so that insights into the relationship between the beetle, the bacteria and the host tree can be made through comparisons with more extensively studied species. Possible management options in an AOD context are considered, and priority areas for future research are identified.

Description: Forest management plans in Bavaria are generally updated only once every 10 years. However, the increasingly dynamic forest structure due to climatic changes requires more frequent data collection in order to maintain up-to-date information. This study explored the use of RapidEye satellite data to provide more frequent updates to the information database. Forest structural information such as quadratic mean diameter (dq), basal area (BA), stem number (SN) and volume (V) were estimated using multi-seasonal analysis of three RapidEye datasets from 2009. Spectral indices and textural metrics provided additional image feature layers. Forest inventory plots were stratified based on the forest type. A correlation analysis was conducted between terrestrial inventory data and that derived from RapidEye data. A cross-validated stepwise forward regression analysis was performed for each forest type. The coefficient of determination and relative root mean square error (rRMSE) showed that stratification improved the regression models, which obtained determination measures ranging from 0.37 to 0.63 and rRMSE ranging from 25 to 131 per cent. Biases of the regression estimates were small, hence the results obtained from applying the models were of an acceptable level of accuracy. The analysis confirmed the potential of RapidEye data to support forest management.

Description: Over the last 60 years, multiple studies have attributed sugar maple ( Acer saccharum Marsh.) dieback and decline to nutrient status, interaction and tree stress. Site differences in deficient, toxic or antagonistic levels of soil calcium, magnesium, phosphorus, potassium, manganese and aluminium are correlated with mortality and dieback in many studies. In general, a single nutrient is rarely determined to be responsible for poor sugar maple health. Other factors such as defoliation, management, climate fluctuations and soil biota can play key roles in dieback. Nutrient stresses can greatly increase the risk of injury and mortality from other biotic or abiotic stresses. Anthropogenic inputs and climate change may also cause perturbation of nutrient or pH thresholds for sugar maple. Therefore, historical sugar maple sites may no longer be suitable to support a healthy sugar maple forest under current management regimes. The following is a review of locations, symptoms and studies of the relationship of mineral stress to sugar maple health, which will be useful information for forest resource managers to consider when faced with maple health issues. Conclusions developed from this review are as follows: (1) land managers should consider soil nutrition in decision-making concerning sugar maple, (2) standardization of evaluation methods for tree nutrition is somewhat lacking and (3) additional multidisciplinary research is needed to clarify the interacting factors affecting sugar maple health and nutrition.

Description: Deer exclosures are often used to encourage woodland regeneration in the Scottish Highlands. However, dense sapling growth, in the absence of red deer ( Cervus elaphus ), within exclosures could pose a threat to internationally important lichen communities on mature oaks in open woodland. Cryptogam communities associated with the lower trunks of oak trees ( Quercus x rosacea Bechst.) were compared from several blocks, inside and outside three exclosures, in Atlantic oak woodland north of Loch Maree, Wester Ross, Scotland. Epiphyte data were collected from three different height zones on both the north and south aspects of oak trees. Terrestrial cryptogam communities, sapling density, shrub cover and height were also compared. Data were analysed using linear mixed effects models. Mean Lobarion lichen cover and species richness was significantly lower on both aspects of oak trees within exclosures in quadrats from more than one zone. Sapling density, dwarf-shrub height and cover were significantly greater within exclosures. Terrestrial cryptogam diversity and species richness were significantly lower inside exclosures. The data suggest that increased shading by saplings around mature oaks in open woodland has had a detrimental effect on Lobarion lichens after 17–22 years of exclosure. Alternative strategies for encouraging woodland regeneration without harming the Lobarion lichen community are discussed.

Description: Growth and yield simulators are often used to assess the long-term sustainability of selection cuttings in northern hardwood stands. Because residual tree growth is affected by tree removal, growth simulators must be coupled with a harvest model to adequately predict future stand development. Harvest models may consider variables such as species, diameter at breast height (DBH), spatial coordinates of the trees and indicators of stem quality and vigour. Through the development of a harvest model applicable to selection cuttings in northern hardwood stands, we aimed to quantify the loss of accuracy caused by the omission of either tree spatial coordinates or tree quality/vigour descriptors from the predictor variables. Spatial correlations were handled using both generalized linear mixed-effect models and a copula approach. Tree vigour and quality were assessed using three different classification systems used in practice. The inclusion of tree vigour and spatial correlations through the copula approach led to a 12 per cent improvement in maximum log-likelihood. However, the inclusion of the spatial coordinates of each tree only accounted for one quarter of this 12 per cent. In cases where a growth simulator uses tree vigour class as input, we recommend the inclusion of this variable in the associated harvest sub-model.

Description: The contribution of understorey vegetation (UVEG) to forest ecosystem biomass and carbon (C) across diverse forest types has, to date, eluded quantification at regional and national scales. Efforts to quantify UVEG C have been limited to field-intensive studies or broad-scale modelling approaches lacking field measurements. Although large-scale inventories of UVEG C are not common, species- and community-level inventories of vegetation structure are available and may prove useful in quantifying UVEG C stocks. This analysis developed a general framework for estimating UVEG C stocks by employing per cent cover estimates of UVEG from a region-wide forest inventory coupled with an estimate of maximum UVEG C across the US Lake States (i.e. Michigan, Minnesota and Wisconsin). Estimates of UVEG C stocks from this approach reasonably align with expected C stocks in the study region, ranging from 0.86 ± 0.06 Mg ha –1 in red pine-dominated to 1.59 ± 0.06 Mg ha –1 for aspen/birch-dominated forest types. Although the data employed here were originally collected to assess broad-scale forest structure and diversity, this study proposes a framework for using UVEG inventories as a foundation for estimating C stocks in an often overlooked, yet important ecosystem C pool.

Description: Five cross validation methods, the k -fold, leave one plot out (LOP), leave one tree per plot out (LOT), 0.632 and 0.632+ bootstrap methods, were examined in this study for their suitability for performance evaluation of seven nonlinear mixed models based on a height–diameter relationship. The k -fold, LOP, 0.632 and 0.632+ methods used plot as the basic unit for data resampling, and applies to situations where predictions are needed for all trees in a new plot not used for model development. All four methods were suitable for evaluating the predictive performance of the selected model(s), and the 0.632 and 0.632+ methods were better than the k -fold and LOP methods. The LOT method used tree as the basic unit for data resampling, and applies to situations where predictions are needed for a portion of trees in a plot not used for model development, while the remaining trees of the plot are used for model development. The LOT method was not suitable for performance evaluation of the selected model(s).

Description: Mixed species stands might contribute to important goals of sustainable forest management, such as higher biological diversity, more resistance and resilience to disturbances and higher carbon storage. Knowledge of stakeholders' perceptions of such ecosystem services in mixed species stands is required for effective policy development. We showed that practitioners' and scientists' perceptions of ecosystem services in mixed species stands in Belgium differed from formal scientific knowledge derived from a synthesis of published studies. The positive perception of supporting, regulating and cultural services in mixed species stands contrasted with less conclusive results from the literature, where positive, negative and neutral effects were reported. Many respondents also signified a lack of information about regulating services. Furthermore, provisioning services were perceived as equal in mixed species stands and monocultures, in contrast to higher productivity demonstrated in mixed species stands in the literature. The regional (Flanders and Wallonia) ecological and socio-economic context influenced both the perception of ecosystem services and of the importance of management objectives. Our results highlighted the need to address the lack of scientific data, to adapt communication to the ecological and socio-economic context, as well as to improve information flow on regulating services and productivity.

Description: Carbon storage estimation for fast-growing bamboos remains limited because of its wide distribution and spatial variation. This study estimates biomass production and carbon storage of a moso bamboo ( Phyllostachys pubescens Mazel ex Houz.) forest in southern China. A diameter–age bivariate distribution model based on the Weibull distribution function and a single bamboo biomass estimation model based on diameter and age were used to predict the biomass and carbon storage. The parameters of the two models were obtained on the basis of the observation data. Results showed that moso bamboo biomass varied with age and diameter at breast height (DBH). The corresponding estimated biomass and carbon storage in the study area were 88.23 and 40.45 Mg ha –1 , respectively. One-sixth of older culms from the entire stand were removed by selective cutting, and the annual yields of biomass and carbon were 14.07 and 6.74 Mg ha –1 , respectively. The moso bamboo forest has higher carbon sequestration capacity than Chinese fir ( Cunninghamia lanceolata (Lamb.) Hook.) forest, tropical mountain rain forest, loblolly pine ( Pinus taeda L.) forest and oriental oak ( Quercus variabilis Bl.). The present model could be used well to estimate accurately the biomass carbon of moso bamboo at regional scale in southern China.

Description: Western hemlock ( Tsuga heterophylla (Raf.) Sarg.) is a major commercial tree species in western Oregon and Washington and is often associated with coast Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var menziesii ) and other species in coniferous forests of the Coast Ranges and Cascade Mountains. Growth of Douglas-fir in many coastal forests has been negatively affected by Swiss needle cast (SNC), a foliar disease caused by the ascomycete Phaeocryptopus gaeumannii (T. Rohde) Petr. and characterized by premature foliage loss on severely infected Douglas-fir trees. The effect of SNC on stand dynamics in mixed Douglas-fir-western hemlock stands was tested by constructing a diameter increment model for western hemlock that quantified its growth response to varying SNC severity in Douglas-fir. Diameter increment of western hemlock in any given growth period increased with increasing initial SNC severity as measured by Douglas-fir foliage retention (FR), here defined as the number of annual needle cohorts held by the tree. Furthermore, a decline in Douglas-fir FR during the growth period was associated with an additional increase in diameter increment of western hemlock trees. Assuming no change in FR over the growth period, western hemlock trees in stands with severely impacted Douglas-fir (initial FR ≤1.5 years) averaged 79 per cent greater diameter growth than that in relatively healthy stands (initial Douglas-fir FR ≥3.5 years). The implied annual diameter growth response of a western hemlock with initial diameter at breast height of 10, 20, 30 or 40 cm was 0.29, 0.52, 0.65 and 0.68 cm year –1 , respectively. Compensatory growth by western hemlock in mixed-species stands alters stand dynamics by allowing this species to surpass the growth of Douglas-fir experiencing severe SNC.

Description: We aggregate and summarize published equation forms for predicting diameter at breast height (d.b.h.) from stump diameters, which have rarely been compared within and between regions. Equations differ by the number and type of predictors and forms of conditioning such that predictions match expectations as stump height approaches breast height. We select four equation forms published for species common to North American cool-temperate tolerant hardwood forests and test them, using published and localized coefficients with a large independent dataset. We compare the predictive strengths of different forms using regression-based equivalence testing and the financial ramifications of selecting one form over another. Predictions of d.b.h., volume and value are made for four harvested stands using each equation with published and localized coefficients. We find that most equations that predict d.b.h. from stump diameter do so quite accurately. However, equations that include stump height as a predictor are superior. There are significant financial differences between valuation of predictions of removals made with different equation forms and predictions made with published and localized coefficients. Further gains in predicting breast height from stump dimensions may come through application of a neiloid form and a whole-tree taper equation.

Description: Changes in the woody composition of Wytham Woods since 1974 are described, related to national trends in broadleaved woodland, and used to suggest the impact of future changes such as from ash dieback disease ( Chalara fraxinea ). Data on the tree and shrub layer from 164 permanent 10 x 10 m plots distributed in a grid across the Woods are presented from 1974, 1991, 1999 and 2012, on species occurrence, regeneration, contribution to the canopy and basal area. Variations in the current and past composition and structure of the Woods are related to past forestry management and natural succession/disturbance processes. These largely mirror changes shown by other surveys at a national level. Fraxinus excelsior has been increasing in prominence across the Woods since 1974, but its future is uncertain because of disease. The species most likely to increase if there is a severe decline in F. excelsior at Wytham appear to be Acer pseudoplatanus, Corylus avellana and Quercus robur . There are benefits from linking long-term studies at one site to wider less detailed surveys in order to explore the general applicability of the results.

Description: The restoration of microbial communities may be central to the re-establishment of plant–soil interactions and renovation of function in degraded woodland systems. However, there is currently little knowledge of the extent to which the soil microbial communities associated with past vegetation persist in such systems. This study used fungal-specific internal transcribed spacer (ITS) ribosomal DNA environmental clone libraries to compare fungal communities in four ancient semi-natural woodland sites in the UK with adjacent non-native conifer plantations, and with adjacent grassland. In total, we recovered 190 distinct ITS sequence types (ITS types), of which the greatest diversity occurred in ancient semi-natural woodland. Although ancient semi-natural woodland and adjacent conifer plantations shared 27 ITS types, none were shared between woodland and grassland sites. A total of 16 ectomycorrhizal genera were subsequently identified using BLASTn searches, of which nine were recovered from both woodland types and none were shared between woodland and grassland sites. Only eight of these genera had previously been identified from sporophores during 50 years of surveying carried out at the same woodland sites. We conclude that fungal communities associated with ancient semi-natural woodland also exist on sites converted to non-native conifer plantations. In consequence, attempts to restore native, semi-natural woodland may have an increased chance of success when focussed on restoration of plantations, rather than the creation of new woodland on ex-agricultural land.

Description: The taper equations used by the Ministry of Forests, Lands and Natural Resource Operations in British Columbia (BC), Canada, date back to the mid-1950s. Very little work has been done on examining the effect of climate on taper, particularly for BC but elsewhere as well. The objective of our research was to determine whether climate has an effect on tree taper for lodgepole pine ( Pinus contorta Dougl. ex Loud.) in BC. The data for this project consisted of multiple diameter inside bark measurements along the stems of 270 trees across eight biogeoclimatic zones. In addition, 20 climate variables for the sample sites were predicted from the ClimateWNA model. Kozak's variable-exponent taper model was refitted with the climate variables in the exponent of the model. The single temperature- and precipitation-related variables that provided the best fit were incorporated into the final taper model. The model was analysed as a mixed-effects model, with spatial correlation and heteroscedastic errors being explicitly modelled. Mean annual precipitation and the Julian date of the first frost after the summer growing period were the best predictors of taper. Further work is required to understand why these variables are important predictors of taper, but a possible linkage is through the tree's crown.

Description: The relationships between above-ground stem, branch, leaf masses and stand density index (SDI) were analysed in Populus x euramericana (Dode) Guinier stands in Jiangsu Province, China. The allometric equations developed in this study accurately estimated masses of above-ground and specific above-ground tree components in stands with different SDIs. The relationship between the mean above-ground mass w and the ratio of stem to the above-ground ( w S / w ) was examined. With increasing w , the stem mass ratio w S / w increased. Mean masses of above-ground and tree components decreased significantly with increasing SDI at age 9 years, indicating the presence of competition-induced limitations to growth. The mean above-ground mass–SDI and mean component mass–SDI were strongly correlated with above-ground mass-SDI and tree component mass–SDI, respectively. An equation describing the relationship between the mean leaf area u and SDI was developed, which fitted well for the u -SDI data. Stem mass increment exponentially increased with increasing leaf area index.

Description: Individual tree growth models are often constructed with much more complexity than is required for many of the tasks to which they might be applied. In many cases, they also have detailed requirements for describing initial conditions, which may necessitate costly data collection. In cases where a large number of model predictions are required for which there is a mismatch between available data and model requirements, an abstracted low-dimension predictive model (LDPM) that uses alternate input variables and that accurately mimics the outcomes of the more complex model for the specified problem may be an attractive option. In this simulation study, several sets of LDPMs are developed as possible replacements for individual tree models in assessing regeneration stocking implications for mixtures of white spruce ( Picea glauca ) and trembling aspen ( Populus tremuloides ). These models can accurately mimic a selected set of outcomes of the parent model, but add a small degree of uncertainty in the process. Limitations introduced by the abstraction process include an overall loss of information and a large reduction in the variability of conditions to which the model can be applied. Benefits introduced by the process include a much better efficiency of data collection and model application efforts towards a specific management problem.