ALBERT

Description: Because of their rapid maneuverability, extended operational range, and improved personnel safety, unmanned aerial vehicles (UAVs) with vision-based systems have great potential for monitoring, detecting, and fighting forest fires. Over the last decade, UAV-based forest fire fighting technology has shown increasing promise. This paper presents a systematic overview of current progress in this field. First, a brief review of the development and system architecture of UAV systems for forest fire monitoring, detection, and fighting is provided. Next, technologies related to UAV forest fire monitoring, detection, and fighting are briefly reviewed, including those associated with fire detection, diagnosis, and prognosis, image vibration elimination, and cooperative control of UAVs. The final section outlines existing challenges and potential solutions in the application of UAVs to forest firefighting.

Description: Boreal peatlands in Canada comprise a substantial store of soil organic carbon (peat), and this peat is vulnerable to extensive burning during periods of extended drying. Increased frequency of extreme weather events in boreal regions is expected with future climate change, and the conditions that would support sustained smouldering peat combustion within peatlands may be more common. Organic soils tend to burn by smouldering combustion, a very slow-moving process in fuels such as those found in peatlands. Thus the most extreme conditions for carbon loss to the atmosphere due to the burning of peat likely occur when widespread propagation of flaming combustion leads to widespread initiation of smouldering. To investigate the potential for large-scale, high-intensity fire spread across forested bogs, we examined the fuel conditions in forested bogs necessary to support active crown fire. We measured surface and canopy fine fuels (those available to contribute to the propagating energy flux of the main flaming front) across a postfire chronosequence of forested boreal bog from central Alberta, Canada. We found that fuel load of fine surface material remained relatively constant across the chronosequence and at levels large enough to support crown fire initiation. Black spruce (Picea mariana (Mill.) B.S.P.) regeneration begins to fill in the crown space with increasing time since disturbance and achieves crown bulk densities similar to black spruce upland forests. We estimated that after about 80 years, the black spruce canopy has developed enough available fuel to support active crown fire on between 10% to 40% of days in a typical fire season in central Alberta, Canada. Broad-scale propagation of high-intensity fire across a peatland when coincident with drought-induced lower moisture in deep peatland layers has the potential to lead to a substantial release of stored terrestrial carbon.

Description: Resource development can have significant consequences for the distribution of vegetation cover and for species persistence. Modelling changes to anthropogenic disturbance regimes over time can provide profound insights into the mechanisms that drive land cover change. We analyzed the spatial patterns of anthropogenic disturbance before and after a period of significant oil and gas extraction in two boreal forest subregions in Alberta, Canada. A spatially explicit model was used to map levels of anthropogenic forest crown mortality across 700 000 ha of managed forest over a 60-year period. The anthropogenic disturbance regime varied both spatially and temporally and was outside the historical range of variability characterized by regional fire regimes. Levels of live forest crown within anthropogenic disturbances declined and edge density increased following oil and gas development, whereas patch size varied regionally. In some places, anthropogenic disturbance generated profoundly novel landscapes with spatial patterns that had no historical analogue in the boreal system. The results illustrate that a shift in one sector of the economy can have dramatic outcomes on landscape structure. The results also suggest that any efforts to better align cumulative anthropogenic disturbance patterns with the historic baseline will almost certainly require a concerted and collaborative effort from all of the major stakeholders.

Description: In many recent studies, the value of forest inventory information in harvest scheduling has been examined. In a previous paper, we demonstrated that making measurement decisions for stands for which the harvest decision is uncertain simultaneously with the harvest decisions may be highly profitable. In that study, the quality of additional measurements was not a decision variable, and the only options were between making no measurements or measuring perfect information. In this study, we introduce data quality into the decision problem, i.e., the decisionmaker can select between making imperfect or perfect measurements. The imperfect information is obtained with a specific scenario tree formulation. Our decision problem includes three types of decisions: harvest decisions, measurement decisions, and decisions about measurement quality. In addition, the timing of the harvests and measurements must be decided. These decisions are evaluated based on two objectives: discounted aggregate income for the planning periods and the end value of the forest at the end of the planning horizon. Solving the bi-objective optimization problem formed using the ε-constraint method showed that imperfect information was mostly sufficient for the harvest timing decisions during the planning horizon but perfect information was required to meet the end-value constraint. The relative importance of the two objectives affects the measurements indirectly by increasing or decreasing the number of certain decisions (i.e., situations in which the optimal decision is identical in all scenarios).

Description: The impact of root water uptake on duff (both fibric and humic horizons) moisture was investigated at deciduous, mixedwood, and conifer stands in Ontario, Canada. Roots were actively excluded from the duff layer using geotextiles inserted at the duff–mineral soil interface and along the plot edges; liquid and vapour water flow was otherwise not affected by the geotextiles. Root exclusion caused little difference in duff moisture content prior to early June, after which the root exclusion plots remained at 15%–20% volumetric water content, whereas root-intact plots declined to as low as 5% volumetric water content during rain-free periods. Only in the root-intact plots did the duff water content reach sufficiently low levels that duff evaporation was limited by low water content. The net effect of root exclusion was to reduce the cumulative growing season water loss in the duff by 19%–31%, depending on the stand type. Root exclusion also decreased the number of days with a high probability of duff smouldering from as many as 72 days·year−1 to as few as 0 days·year−1. This root exclusion experiment provides a model for short-term duff moisture transitions under thinned forests such as those forests under community wildfire protection.

Description: Trees form the terrestrial interface with the atmosphere in forested regions. The electrical properties of trees may influence their response to atmospheric conditions and potentially lethal phenomena (e.g., lightning). We review the literature describing electrical properties of trees and provide a tabular summary of the methods and goals of each study. We hypothesized that electrical resistivity varies consistently among species and between growth forms. We surveyed resistivity of eight tree and three vine species in Michigan and Kentucky, and we quantified resistivity over a moisture gradient for wood blocks of four tree species. Resistivity varied predictably with stem diameter and differed among species and growth forms. Specifically, resistivity of trees was approximately 200% higher than resistivity of vines, and resistivity of conifers was 135% higher than that of hardwoods. The regional comparison showed no difference in resistivity of red maple (Acer rubrum L.) and sugar maple (Acer saccharum Marsh.) between Michigan and Kentucky. These results, in combination with interspecific differences observed among wood blocks, suggest that there is a phylogenetic basis for variation in resistivity that reflects differences in anatomy and physiology. Our review and empirical survey provide a framework for studying the ecological effects of lightning in the context of the electrical properties of trees.

Description: The influence of forest ecology and strategic planning has increased in importance to support the management of mixed-species forests to enhance biodiversity. However, little is known about competitive and facilitative interactions between trees and species in mixed fir–beech–spruce forests, mostly because of a lack of long-term experimental research. In the 1960s, long-term sample plots were established in the Western Carpathians to develop region-specific yield models. Trees in the plots were measured at 5- to 16-year intervals from 1967(69). In 2010, the positions of standing trees in all plots were identified spatially. Stump positions were also identified to record the coordinates of trees that had been removed or had died. The objectives of this study were to evaluate the applicability of widely used competition indices for mature fir–beech–spruce mixed forests and to test whether the tree competition zone changes among species and forest stands of different stocking densities. Results showed that the best competition index was based on the comparison of the basal area of competitors and the subject tree in the radius, which was defined as a function of stand density and species. In addition, beech was found to be a strong self-competitor, which was not the case for silver fir (Abies alba Mill.). Results suggest that simpler competition indices are better suited for such diverse forests, as more complex indices do not describe the competition interactions sufficiently well.

Description: The parsimonious taper function proposed by Riemer et al. (1995. Allg. Forst.- Jagdztg. 166(7): 144–147) was fitted for radiata pine (Pinus radiata D. Don) stems in Spain by using a nonlinear mixed modelling approach. Eight candidate models (all possible expansion combinations of the three fixed parameters with random effects) were assessed, and the mixed model with three random effects performed the best according to the goodness-of-fit statistics. An evaluation data set was used to assess the performance of these models in predicting stem diameter along the bole, as well as total stem volume. Four prediction approaches were compared: one subject (tree) specific (SS) and three population specific (ordinary least squares (OLS), mean (M), and population averaged (PA)). The SS responses for a tree were estimated from a prior stem diameter measurement available for that tree, whereas OLS, M, and PA were obtained from the fixed-effects model, from the fixed parameters of mixed-effects models, and by computing mean predictions from the mixed-effects models over the distribution of random effects, respectively. Prediction errors were greater for the M and PA responses than for the OLS response, and therefore, from the prediction point of view, the use of the mixed-effects models is not recommended when an additional stem diameter measurement is not available. The mixed model with three random effects was also selected as the best model for SS estimations. Measurement of an additional stem diameter at a relative tree height of approximately 0.5 provided the best calibrations for stem diameters along the bole and total stem volume predictions. The SS approach increased the flexibility and efficiency of the selected mixed-effects model for localized predictions and thus improved the overall predictive capacity of the base model.

Description: Lightning strikes millions of trees worldwide each year, yet structured lightning damage surveys are relatively rare. Estimates drawn from the literature suggest that lightning directly or indirectly kills up to 4% of large canopy trees in a stand annually. Lightning is a major cause of death for pines in southeastern US forests and for large cacti in some deserts, but its landscape-level effects exclusive of fire at higher latitudes are poorly known. We quantified damage to trees from lightning and other sources in hemlock–hardwood forests of the Huron Mountain Region of Michigan, USA. This region receives ca. 100 cloud-to-ground lightning flashes per year, with most occurring in May to August. We recorded abiotic and biotic damage on 309 trees distributed among nine transects, each 〉2 km long. None of the transect trees had lightning scars, and we observed only 14 clear cases of lightning damage among thousands of trees examined during associated meander surveys (each ca. 0.5 ha). This damage was more commonly associated with emergent stature (50% of struck trees) and higher rates of biotic damage (50%) than we observed in the 309 transect trees (22% emergent status and 16% incidence of biotic damage). Nearly all (93%) of the lightning damaged trees were conifers, suggesting that either susceptibility to, or response to, lightning strikes has a phylogenetic basis. These preliminary results provide a foundation for comparative studies in other forests. Accurate quantification of lightning-induced tree mortality will improve forest turnover models and facilitate predictions of future forest structure under conditions of increased lightning frequency.

Description: Constraints of the physical environment affect forest growth and forest operations. At a local scale, these constraints are generally considered during forest operations. At regional or continental scales, they are often integrated to larger assessments of the potential for a given land unit to be managed. In this study, we propose an approach to analyze the integration of physical-environment constraints in forest management activities at the regional scale (482 000 km2). The land features that pose constraints to forest management (i.e., hydromorphic organic deposits, dead-ice moraines, washed till, glacial block fields, talus, and active aeolian deposits, slopes 〉 40%) were evaluated within 1114 land districts. To distinguish land districts that can be suitably managed from those where constraints are too important for sustainable timber production, we carried out a sensitivity analysis of physical constraints for the 1114 land districts. After analysis of two portions of the study area under management, a land district was considered suitable for management when more than 20% of its land area consists of features imposing few constraints or, for mountain-type relief districts, when more than 40% of the land area consists of features imposing few constraints. These cutoff values were defined by expert opinion, based on sensitivity analyses performed on the entire study area, on analyses of two different sectors with different types of constraints and on a strong understanding of the study area. Our results show that land districts where the physical environment posed significant constraints covered 7.5% of the study area (36 000 km2). This study shows that doing an a priori classification of land units based on permanent environmental features could facilitate the identification of areas that are not suitable for forest management activities.

Description: Over the period 1883–2013, recruitment of subalpine limber pine (Pinus flexilis E. James) and Great Basin bristlecone pine (Pinus longaeva D.K. Bailey) above the upper tree line, below the lower tree line, and across middle-elevation forest borders occurred at localized sites across four mountain ranges in the western Great Basin. A synchronous pulse at all ecotones occurred between 1963 and 2000 (limber pine) and between 1955 and 1978 (bristlecone pine) when pines expanded 225 m beyond forest borders. Little recruitment occurred before this interval or in the 21st century. No obvious environmental factors distinguished recruitment locations from nonrecruitment locations. Where their ranges overlap, limber pine has leapfrogged above bristlecone pine by 300 m. Limber pine tree-ring chronologies, developed to compare radial-growth responses with recruitment, showed dominant pulses of increased growth during the same interval as recruitment. Significant climate correlations of growth and recruitment indicated lead and lag effects as much as 6 years and complex relationships with climate variables, corroborating the importance of cumulative climate effects relative to any single year. Water relations were the most important drivers of growth and recruitment and interacted with growing-season minimum and maximum temperatures. These results underscore the importance of studying ecotones at all margins when evaluating conifer response to climate change.

Description: Most hypotheses about controls over high-altitude forests, including treeline, the elevation for upright woody plants, or timberline, the upper elevation for aggregated forest, suggest that low temperature drives forest dynamics, either through effects on cell division and tree growth or indirectly through frost damage or nutrient availability. However, abiotic factors other than temperature, including water availability, may serve as other important controls at high elevations, particularly for seedlings. To test the hypothesis that the timing and amount of precipitation exerts a strong control over the high-elevation forest boundary on the Wasatch Plateau in central Utah, USA, we conducted a field experiment that manipulated water availability and monitored photosynthesis, growth, and survivorship in Picea engelmannii Parry ex Engelm. seedlings. Survivorship increased from the driest to the wettest conditions, whereas the timing of precipitation did not explain differences in survival. However, we found that large, infrequent rain events increased maximum photosynthetic flux density compared with small, frequent rain events. Our results highlight the potential role of growing season water availability in limiting timberline expansion below the low-temperature thermal limits of P. engelmannii. As a consequence, the infilling of trees below the treeline in this region in response to climate change is likely to be episodic and driven by multiyear periods of high water availability and frequency that overcome drought limitations.

Description: European beech (Fagus sylvatica L.) is an economically and ecologically important forest tree species in Europe. Expected future temperature increases due to global climate change may significantly affect growth of beech trees and consequently influence carbon cycling in beech forests. We tested the hypothesis that soil temperature influences the growth of both belowground and aboveground parts of beech seedlings. One-year-old seedlings were transferred into rhizotrons and subjected to two different soil temperatures for 2 years while the soil moisture level was kept constant. The main effect of the soil temperature was a changed biomass of the woody part of the seedlings. Soil temperature significantly influenced the biomass of shoots and roots and diameter of the stem, which were the highest for the seedlings grown in conditions of soil temperatures maintained in the range of summer soil temperatures from the site of origin of the seedlings. Increased soil temperature also resulted in increased specific root length and specific root tip density. Root-to-shoot ratio and leaf parameters (leaf mass, number of leaves, and specific leaf area), except for leaf area ratio, were not influenced by soil temperature.

Description: Soil disturbance from organic matter loss and soil compaction can impair site productivity, but less is known about whether these disturbances also affect forest health (defined here as the presence and severity of damaging pests and diseases, mortality, and overall vigour). We used six long-term soil productivity (LTSP) sites in the interior of British Columbia, Canada to test the effects of organic-matter removal and soil compaction on forest health, and to explore the relationship between forest health response and potential indicators of site sensitivity: mineral soil pH, base saturation, carbon to nitrogen ratio (C:N), carbon to phosphorus ratio (C:P), and calcium to aluminum ratio (Ca:Al). Visual forest health surveys were conducted on 5400 15 and 20 year old lodgepole pine (Pinus contorta Dougl. ex Loud.) trees. Soil disturbance treatments significantly affected forest health metrics, but this response typically differed among sites. Principle component analyses indicated the response of healthy trees was negatively related to soil base saturation, the response of dead or dying trees related to soil C:P, and the response of tree disease related to soil Ca:Al, pH, base saturation, and C:N. We found forest health response to soil disturbance varied among sites with relationships between response and soil chemical properties, suggesting a greater vulnerability of pine stands to disease with increasing soil acidity.

Description: Individual tree heights are needed in many situations, including estimation of tree volume, dominant height, and simulation of tree growth. However, height measurements are tedious compared to tree diameter measurements, and therefore height–diameter (H–D) models are commonly used for prediction of tree height. Previous studies have fitted H–D models using approaches that include plot-specific predictors in the models and those that do not include them. In both these approaches, aggregation of the observations to sample plots has usually been taken into account through random effects, but this has not always been done. In this paper, we discuss four alternative model formulations and report an extensive comparison of 16 nonlinear functions in this context using a total of 28 datasets. The datasets represent a wide range of tree species, regions, and ecological zones, consisting of about 126 000 measured trees from 3717 sample plots. Specific R-functions for model fitting and prediction were developed to enable such an extensive model fitting and comparison. Suggestions on model selection, model fitting procedures, and prediction are given and interpretation of the predictions from different models are discussed. No uniformly best function, model formulation, or model fitting procedure was found. However, a 2-parameter Näslund and Curtis function provided satisfactory fit in most datasets for the plot-specific H–D relationship. Model fitting and height imputation procedures developed for this study are provided in an R-package for later use.

Description: A major challenge in studies estimating stand water use in mixed-species forests is how to effectively scale data from individual trees to the stand. This is the case for forest ecosystems in the northeastern USA where differences in water use among species and across different size classes have not been extensively studied, despite their relevance for a wide range of ecosystem services. Our objectives were to assess the importance of different sources of variability on transpiration upscaling and explore the potential impacts of future shifts in species composition on the forest water budget. We measured sap velocity in five tree species (Fagus grandifolia Ehrh., Acer rubrum L., Acer saccharum Marsh., Betula alleghaniensis Britton, and Betula papyrifera Marsh.) in a mature stand and a young stand in New Hampshire, USA. Our results showed that the greatest potential source of error was radial variability and that tree size was more important than species in determining sap velocity. Total sapwood area was demonstrated to exert a strong controlling influence on transpiration, varying depending on tree size and species. We conclude that the effect of potential species shifts on transpiration will depend on the sap velocity, determined not only by radial variation and tree size, but also by the sapwood area distribution in the stand.

Description: Alterations to forest canopy structure directly affect the hydrology and biogeochemistry of wooded ecosystems. Epiphytes alter canopy structure, thereby intercepting rainwater, reducing penetration of rain to the surface (as throughfall), modifying throughfall chemistry, and changing throughfall responses to storm conditions. These processes are well established for epiphyte presence versus absence; yet, it is unknown how epiphyte–throughfall interactions change across an epiphyte cover continuum (important information for prediction of ecological changes with epiphyte establishment or decline from disturbance). To fill this gap, we monitored throughfall water and dissolved ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl–, NO3–, PO43–, SO42–) beneath a common epiphyte (Tillandsia usneoides L.) across cover percentages (0%–20%, 21%–40%, 41%–60%, 61%–80%, 81%–100%) for 47 storms. Throughfall amount inversely responded to epiphyte cover while increasing salt wash-off and intracellular leaching. Greater epiphyte cover released NH4+ and decreased NO3– from throughfall. Storm conditions (high vapor pressure deficit, moderate wind speeds, and low intensity) strengthened throughfall responses as T. usneoides cover increased. Factorial MANOVA results revealed significant trends for throughfall ion enrichment or depletion via wash-off, leaching, and uptake. These data suggest that inclusion of epiphyte alterations to rainwater and solute inputs in ecosystem nutrient budgeting studies should consider the full continuum of epiphyte cover represented at that site.

Description: Deadwood in various stages of decomposition and diverse spatial arrangements provides habitat for numerous organisms. However, knowledge on the colonization of deadwood by vascular plants in mixed deciduous forests is insufficient. We carried out our study in an oak–lime–hornbeam forest in northeastern Poland. Downed logs were colonized by 49 vascular plant species, a number higher than reported from any other type of forest. Species richness and abundance of plants increased with log diameter and decomposition. The former was higher on broadleaf deadwood than on coniferous deadwood (46 vs. 38 species). The frequency and abundance on logs were higher for small-seeded plants (

Description: We report estimates of the amount, distribution, and uncertainty of aboveground biomass (AGB) of the different ecoregions and forest land cover classes within the North American boreal forest, analyze the factors driving the error estimates, and compare our estimates with other reported values. A three-phase sampling strategy was used (i) to tie ground plot AGB to airborne profiling lidar metrics and (ii) to link the airborne estimates of AGB to ICESat-GLAS lidar measurements such that (iii) GLAS could be used as a regional sampling tool. We estimated the AGB of the North American boreal forest at 21.8 Pg, with relative error of 1.9% based on 256 GLAS orbits (229 086 pulses). The distribution of AGB was 46.6% for western Canada, 43.7% for eastern Canada, and 9.7% for Alaska. With a single exception, relative errors were under 4% for the three regions and for the major cover types and under 10% at the ecoregion level. The uncertainties of the estimates were calculated using a variance estimator that accounted for only sampling error, i.e., the variability among GLAS orbital estimates, and airborne to spaceborne regression error, i.e., the uncertainty of the model coefficients. Work is ongoing to develop robust statistical techniques for integrating other sources of error such as ground to air regression error and allometric error. Small ecoregions with limited east–west extents tended to have fewer GLAS orbits and a greater percent sampling error. AGB densities derived from GLAS agreed closely with the estimates derived from both forest inventories (

Description: Vegetative propagation of conifers has found large-scale industrial application via somatic embryogenesis (SE), rooting of cuttings, and organogenesis. Genetic gain is achieved with all of these methods but is the highest with SE, primarily because SE cultures can be cryopreserved. This allows for plants derived from part of each cell line to be field tested over a long period while the rest of each cell line is kept in a juvenile state by cryopreservation for later use. This makes it possible to select the best performers within the best families. For rooting of cuttings and organogenesis, genetic gain is generally based on family average, which is less powerful. However, SE has its limitations, primarily because its initiation, maturation, or germination rates are too low to be effective for many species. Consequently, for many species, the preferred clonal propagation option is still rooting of cuttings or organogenesis. If better methods can be developed to keep ortets used for rooting of cuttings and organogenesis in a prolonged juvenile state, or if future developments in marker technology reach a point where within-family selection becomes possible without the aid of cryopreservation, rooting of cuttings and organogenesis will achieve the same genetic gain as SE.

Description: In the mid-1990s, a Spruce Bark Beetle (Ips typographus L.) outbreak affected the Norway spruce (Picea abies (L.) Karst.) forests in the higher elevations of the Bavarian Forest National Park in Germany. To monitor the effect of this large-scale disturbance on the understory vegetation, a series of permanent plots was established in 1998. Until 2000, most of the trees of the spruce-dominated forests at elevations 〉 1.100 m a.s.l. died. To explore the long-term vegetation development after the disturbance, we resurveyed these plots in 2010. We hypothesised that as a consequence of the stand-replacing disturbance, (i) species composition would change substantially, (ii) shade-tolerant forest species would be replaced by light-demanding species, and (iii) the expansion of the light-demanding species would homogenize species composition. Comparing the 1998 and 2010 situations, we found that species composition did not change substantially after the dieback of the tree layer, shade-tolerant species survived, light-demanding species increased only marginally, and vegetation heterogeneity did not change. The main reason is the missing forest floor disruption: there is no open space emerging for species to establish when trees die standing. As a consequence, a dramatic change in ecosystem structure (loss of the whole canopy layer) is not necessarily connected with a general change in species composition.

Description: It is acknowledged that natural forest fires cannot and even should not be eliminated from the North American boreal forest. Forest fires produce immediate losses of wood volume, disrupt the conversion of the actual forest age structure into a target structure, and prevent planned timber supply (PTS) levels from being achieved. In this paper, we explore the extent to which periodic shortfalls in available timber under various burn rates can be mitigated through salvage logging and the tolerance of forest managers to a given level of shortfall, both as a function of forest age class structure. Simulations are done using both a deterministic and a stochastic representation of burn rate over time. Results show that the frequency of shortfall events can be reduced by salvage logging and by the introduction of measures that generate a tolerance to shortfall and that this mitigation potential is influenced by initial forest age class structure and burn rate. Results also show that even a 100% rate of salvage logging cannot fully compensate for timber losses to fire and eliminate fire-induced timber shortfalls. Furthermore, interannual burn rate variability reduces the efficiency of both mitigation measures. As the PTS is never realized under fire risk, the real cost of opting for different PTS scenarios should be estimated not from the difference in PTS but rather from the more realistic difference in realized timber harvest.

Description: Harvest strategies that emulate natural disturbances are being promoted to restore multilayered forest heterogeneity, notably the harvest of largest trees. However, their use also increases management complexity, and more information on their practical feasibility and effects on forests is needed. Therefore, in this study, target diameter cutting treatments were applied to a heterogeneously structured stand in southern Sweden (exemplifying a conifer-dominated forest of the hemiboreal forest region in northern Europe) to assess their effects on gap dynamics, natural regeneration, and stand growth. The target diameter cutting resulted in an exponentially decreasing gap size distribution, with the largest canopy gaps measuring 0.1–0.2 ha. The gap closure rate was higher than reported rates for gaps in natural forests. After 5 years, sufficient numbers of seedlings had regenerated, but proportions of intermediate- and late-successional tree species were low. The observed stand growth exceeded rates simulated using the growth model Standwise in the Heureka forest planning software package. The findings from this case study are useful for refining the general concept of close-to-nature forestry, but they need to be complemented with the information available from other regeneration studies after partial harvest.

Description: We evaluated effects of topsoil scarification by heavy machinery on growth of two valuable, shade-intolerant tree species — Nothofagus dombeyi (Mirb.) Oerst. (evergreen and considered to be very plastic to different soil fertility levels) and Nothofagus alpina (Poepp. & Endl.) Oerst. (deciduous and considered to be sensitive to soil fertility) — seedlings that were underplanted in Nothofagus old-growth forests, which were subjected to shelterwood cuttings without the final cut in the Chilean Andes. We compared tree basal diameter growth as it responds to light availability and soil compaction (as measured by resistance to penetration) by fitting a growth model based on the Michaelis–Menten equation. Predicted growth of N. dombeyi was greater than N. alpina in high and low light levels; however, there were no significant differences between the species. Both species showed significant differences at high levels of penetration resistance (〉2000 kPa). Differences for N. dombeyi occurred above ∼40% in total light, and differences occurred for N. alpina above ∼20% in total light. However, they were not different when compared at low and intermediate levels of penetration resistance. The results suggest that partial shelterwood cuts may provide adequate light levels to achieve appropriate growth of underplanted Nothofagus seedlings. However, if regeneration of N. alpina is desired, scarification of topsoil needs to be implemented with more caution in canopy openings, as traffic and soil removal by heavy machinery can have detrimental effects on growth of this species and other species that are more sensitive to soil compaction.

Description: Forest management regimes increasingly focus on the emulation of natural disturbance events, e.g., fire or insect outbreaks, to help increase ecosystem sustainability. We determined the residual stand response to a variable retention harvest inspired by spruce budworm (Choristoneura fumiferana (Clemens)) outbreaks in New Brunswick, Canada. Our objectives were to analyze the differences between surviving residual trees and those that succumbed to windthrow and to quantify growth release. The treatment was based on harvesting the estimated spruce budworm outbreak mortality, i.e., 90% of mature balsam fir (Abies balsamea (L.) Mill., 60% of mature spruce (Picea spp.), and no hardwoods. Windthrow increased with the proportion of trees harvested and averaged 52% over 7–9 years in these stands with high balsam fir – spruce content. One-third of 42 harvested plots sustained 〉30% windthrow, whereas 73% of 11 similar unharvested plots had

Description: Accumulating evidence suggests that density dependence, whether at early or late life stages, is an important mechanism regulating plant population structure. However, the opposing effects of habitat heterogeneity and species-level variation might have confounded the prevalence of density dependence in natural forests. These compatible ideas were rarely considered simultaneously. In this study, we applied a spatial statistical technique to examine (i) the prevalence of density dependence at late life stages after controlling for habitat heterogeneity and (ii) the relationships between species traits and the strength of density dependence in a newly established, 25 ha subtropical mountain forest plot in central China. Of the 88 (75%) tree species analyzed, 66 were found to exhibit density dependence predominantly at very close distances among neighbors in the species-rich subtropical forest. In addition, the strength of density dependence was associated with species traits. Our findings identified strong density dependence among trees that had greater stature and were rarer. We concluded that density dependence was a prevalent mechanism for regulating the population structure of most tree species and both habitat heterogeneity and species-level variation played crucial roles in shaping the strength of density dependence in natural forests.

Description: Tree growth rate is frequently used to estimate mortality probability. Yet, growth metrics can vary in form, and the justification for using one over another is rarely clear. We tested whether a growth index (GI) that scales the realized diameter growth rate against the potential diameter growth rate (PDGR) would give better estimates of mortality probability than other measures. We also tested whether PDGR, being a function of tree size, might better correlate with the baseline mortality probability than direct measurements of size such as diameter or basal area. Using a long-term dataset from the Sierra Nevada, California, U.S.A., as well as existing species-specific estimates of PDGR, we developed growth–mortality models for four common species. For three of the four species, models that included GI, PDGR, or a combination of GI and PDGR were substantially better than models without them. For the fourth species, the models including GI and PDGR performed roughly as well as a model that included only the diameter growth rate. Our results suggest that using PDGR can improve our ability to estimate tree survival probability. However, in the absence of PDGR estimates, the diameter growth rate was the best empirical predictor of mortality, in contrast to assumptions often made in the literature.

Description: Salinity is a major environmental stress that is reducing crop yield, particularly in arid and semi-arid regions of the world. It is responsible for many physiological and biochemical disorders in plants. To investigate its effects on two acacia species, namely Acacia ampliceps Maslin and Acacia nilotica L., a solution-culture experiment was conducted in which both species were exposed to NaCl concentrations of 100 and 200 mmol·L–1. After four weeks of salinity stress, plants were harvested, and physical-growth data were recorded. The membrane stability index and activities of antioxidants enzymes such as superoxide dismutase, peroxidase, and catalase were determined using standard methods. Root exudates were collected for the analysis of organic acids, i.e., citric acid and tartaric acid. Root ash alkalinity was also measured. The results indicated that salinity stress caused a significant increase in the activities of antioxidant enzymes and in the release of organic acids in both species. Higher activities of antioxidant enzymes resulted in less damage to membranes and produced more shoot and root biomass in A. ampliceps than in A. nilotica. Likewise, having more rhizosphere acidification enabled A. ampliceps to respond in a better way to salinity stress than A. nilotica.

Description: On 11 December 2008, a severe ice storm affected large portions of southern New England. We report the results of a study investigating differential damage among tree species. Past studies surveying ice-damaged forests have relied heavily on ocular estimations of canopy damage. We compare this method with damage estimates based on the cross-sectional area of downed woody material and quantitative comparisons of tree height and canopy projection in damaged and undamaged stands. Ocular estimates and changes in canopy height and projection were unreliable. Estimates based on the amount of woody debris provide a more robust measure of storm damage. We assess damage in two forest tracts with a dominant red oak (Quercus rubra L.) canopy (42% of total basal area) and an American beech (Fagus grandifolia Ehrh.) dominated understory (50% of all stems 〉 1.3 m). Species’ standing basal area was well correlated with the amount of newly downed woody debris (r = 0.69, p 〈 0.001); accordingly, oak species constituted approximately 57% of all newly downed woody debris, and ANOVA showed that oak species were significantly more impacted by ice damage than other species present (p 〈 0.001). Our findings indicate that canopy species provide an “umbrella effect”, shielding less dominant lower strata trees from the worst effects of ice load. Oak was also the largest contributor to older downed woody debris, indicative of a recurrent historical pattern of differential canopy disturbance driven by strata and relative dominance. These findings suggest that periodic ice events play an important role in facilitating the advancement of shade-tolerant tree species into the canopy from lower strata.

Description: Phytolith-occluded organic carbon (PhytOC) is an important long-term (up to several thousand years) terrestrial carbon (C) fraction in forest ecosystems. The objectives of this study were to (i) investigate the spatial distribution of PhytOC in Lei bamboo (Phyllostachys praecox C.D. Chu & C.S. Chao.) forests under intensive management (mulching and fertilization) and (ii) assess the role of PhytOC in C sequestration in a Lei bamboo stand and across subtropical China. Phytolith concentrations in Lei bamboo plant components were (P 〈 0.05) in the following order: rhizome ≈ stump 〉 leaf ≈ branch 〉 culm. The distribution of PhytOC in bamboo leaves, branches, culms, rhizomes, and stumps was 22.2%, 12.1%, 16.1%, 15.9%, and 33.7%, respectively. The PhytOC stock was in the following order (P 〈 0.05): soil (9361 kg C·ha−1) 〉 mulching materials (197.5 kg C·ha−1) 〉 belowground plant parts (13.0 kg C·ha−1) ≈ aboveground plant parts (12.8 kg C·ha−1) ≈ litterfall (11.3 kg C·ha−1). The PhytOC accretion rate in the vegetation in the Lei bamboo stand was 19.4 kg C·ha−1·year−1, equivalent to 71 kg CO2-eq·ha−1·year−1. The soil PhytOC stock decreased markedly with depth and had an accretion rate of 325 kg C·ha−1·year−1 for the 0–60 cm soil layer. Based on a PhytOC accretion rate of 0.795 Mg CO2-eq·ha−1·year−1, PhytOC accretion rate in the 2.62 × 106 ha of Lei bamboo stands in southern China is estimated to be 2.08 × 106 Mg CO2-eq·year−1. In conclusion, intensively managed Lei bamboo stands have a large potential in long-term C sequestration in the form of PhytOC, and the PhytOC stock belowground should not be ignored due to its contribution to the ecosystem level PhytOC stock.

Description: Because many currently protected forests are former timber production areas, restoration activities are often used to re-establish their natural structures. In this experimental study, we monitored the establishment of tree seedlings in previously managed but currently protected Scots pine (Pinus sylvestris L.) dominated stands in boreal forests 5 years after restoration measures. The study included eight study areas (115 sample plots) in southern Finland. We compared seedling abundance between five study groups: untreated control forest, unburned canopy gap, burned full-canopy forest, burned canopy gap, and thinned and burned forest. Density of tree seedlings was highest in burned canopy gaps (mean 25.4 seedlings/100 m2 compared with 6.0 seedlings/100 m2 in control sites). In particular, birch (Betula spp.) and Scots pine were significantly more abundant within burned canopy gaps than in unburned gaps. We conclude that opening within-stand canopy gaps, especially in combination with prescribed burning, can be useful in forest restoration as the gaps diversify age-class structure and tree species composition of single-cohort pine stands.

Description: We examined the relationship between thinning intensity and volume increment predicted by four commonly used individual-tree growth models in Central Europe (i.e., BWIN, Moses, Prognaus, and Silva). We replicated conditions of older growth and yield experiments by selecting 34 young, dense plots of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and European beech (Fagus sylvatica L.). At these plots, we simulated growth, with mortality only, to obtain the maximum basal area. Maximum basal area was then decreased by 5% or 10% steps using thinning from below. Maximum density varied considerably between simulators; it was mostly in a reasonable range but partly exceeded the maximum basal area observed by the Austrian National Forest Inventory or the self-thinning line. In almost all cases, simulated volume increment was highest at maximum basal area and then decreased with decreasing basal area. Critical basal area, at which 95% of maximum volume increment can be achieved, ranged from 0.46 to 0.96. For all simulators, critical basal area was lower for the more shade-tolerant species. It increased with age, except for Norway spruce, when simulated with the BWIN model. Age, where mean annual increment culminated, compared well with yield tables.

Description: Teak (Tectona grandis L. f.) clonal forestry has lately become a reality thanks to the development of efficient techniques for mass clonally propagating true-to-type teak trees of various ages. Field trials were set up to assess the influence of teak genotypes of different ages and three clonal propagation techniques on field growth performances of teak clones. Significant differences (P 〈 0.0001) in height (H, from 11.9 to 17.5 m), diameter at breast height (D, from 11.8 to 18.9 cm), and volume (V, from 67.9 to 194.7 dm3) were observed 5 years after planting for clones produced by microcuttings from 6-month-old to 70-year-old teak ortets, regardless of their age. After 6.5 years of testing, H, D, and V performances of clones produced by rooted cuttings and microcuttings from 7-year-old teak trees were similar, notwithstanding clone × propagation method interactions. Five years after planting, clones produced by meristem culture from 7-year-old ortets had larger diameters and volumes than clones produced by microcuttings, whereas H varied according to clone × propagation method interaction. The various propagation methods used had no significant effect on mortality (

Description: Natural disturbances are among the most important factors that shape forest dynamics and forest landscapes. However, the natural disturbance regime of Norway spruce (Picea abies (L.) Karst.) forests in Europe is not well understood. We studied the disturbance regimes in three forest reserves in Bulgaria (Parangalitsa, Bistrishko branishte, and Beglika), which are representative of the range of conditions typical for P. abies ecosystems in central and southern Europe. Our data indicated that large-scale disturbances were most numerous in forests that were between 120 and 160 years old, those with unimodal diameter at breast height (DBH) distributions, and especially those located in vulnerable topographic settings. Wind disturbances ranged up to 60 ha, followed in one case by a 200 ha Ips typographus (Linnaeus, 1758) outbreak. Older forests and those with more complex structures (i.e., reverse-J DBH) were characterized by numerous small gaps but were also affected by a few larger disturbances. In some old-growth forests at highly productive sites, gaps could be so numerous that the long-term existence of old trees may become an exception. Over the past centuries, the natural range of variability of these Norway spruce forests in Bulgaria appears to have been shaped mostly by wind and bark beetle disturbances of various sizes.

Description: Exponential fertilization has been shown to be a useful technique for improving seedling quality during nursery production. In this study, we evaluated (i) the impact of exponential vs. conventional fertilization on trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) seedlings during nursery production and (ii) the growth performance and nitrogen (N) utilization of those seedlings in response to foxtail barley (Hordeum jubatum L.) competition after the transplantation of seedlings in a greenhouse experiment. Exponential fertilization with an application rate higher than the conventional fertilization increased the internal N reserve in trembling aspen and white spruce seedlings during nursery production and also increased new leaf, new stem, and old stem biomass and N retranslocation rates in trembling aspen seedlings but not in white spruce seedlings after transplantation. Foxtail barley competition decreased N concentrations in seedlings and soil N uptake by the seedlings; however, increased N retranslocation rates with foxtail barley competition were observed in white spruce seedlings but not in trembling aspen seedlings. Our results suggest that the growth performance of seedlings was improved by N loading, whereas the impact of vegetation management was species specific.

Description: Typical use of diversity indices in forest stands does not reflect within-stand variation in species and structure. Despite numerous efforts to design stand diversity indices that capture spatial variation in two- or three-dimensional space, the application of these indices is limited due to their complexity or lack of ecological relevance. In this research note, we illustrate the application of diversity indices at the neighbourhood scale using stem mapping data from a boreal mixedwood stand in northeastern Ontario, which was assessed before and after partial harvesting. Among the three diversity indices (Shannon species diversity, Shannon structural diversity by height class distribution, and structural diversity by height variation), neighbourhood structural diversity by height variation was less dependent on neighbourhood size (between 4 and 12 trees) and more sensitive to stand structural change than Shannon structural diversity by height class distribution. Despite general increases in Shannon species diversity and structural diversity by height variation at both stand and neighbourhood scales after the harvest — an indication of higher diversity — within-stand variation (coefficients of variation) in neighbourhood diversity values decreased, suggesting that residual stands were spatially more uniform after the harvest. Therefore, the neighbourhood diversity indices are useful for capturing spatial variation in species and structural diversity, especially in managed stands in which spatial distributions and patterns can be significantly modified by management interventions.

Description: Boreal forests in northern Alberta have a growing anthropogenic footprint due to a rapidly growing oil sands mining industry. Although land reclamation is a necessary aspect of responsible industrial development, these activities nearly always affect higher order landscape components such as the broader landform, and its hydrology and biogeochemistry. Recent anthropogenic impacts are then believed to result in new environmental conditions and obstacles under which the boreal forest is developing, potentially leading to irreversibly different environments that could be characterized as novel ecosystems. Reflecting an emerging trend across the field of restoration ecology, these novel ecosystems are not necessarily undesirable. Instead, they are an unavoidable consequence of pervading anthropogenic effects on natural ecosystems. It is our view that successful reclamation outcomes can still be derived so long as policy and regulatory requirements are afforded the necessary scope and economic flexibility to account for the development of hybrid and novel ecosystems among highly disturbed mine sites. Hence, this analysis seeks to situate current and anticipated challenges affecting the reclamation of boreal forest following oil sands mining by describing (i) how regulatory criteria shape reclamation practices and targeted end goals and (ii) how these approaches embody latest trends and priorities in the area of restoration ecology.

Description: When a company is integrated vertically, it can manage and plan its overall value chain in one direct and integrated approach. However in many cases, companies follow a decoupled approach where forests and production plants optimize separately their processes in a supply-driven strategy. In Chile, the two largest forest companies are vertically integrated (i.e., they own forest and mills that produce logs, lumber, plywood, pulp, paper, and bioenergy, etc.). Historically, they have coordinated their value chains using a make-to-stock strategy, for which the forest is the main driver of the value chain activities. In this paper, we propose an integrated planning approach to show the impacts of a demand-driven integration of the value chain in the forest industry. To compare this strategy with the decoupled strategy, we propose a mixed integer programming (MIP) model for the integrated strategy. To illustrate our proposal, we use forest and production information from a Chilean forest company. The decoupled strategy, where the forest and industry planning are planned separately, uses two models. The first model deals with the forest management and harvesting decisions and maximizes the expected net present value (NPV) of logs. In this model, the planning horizon covers one full forest rotation, which in Chile corresponds to about 25 years. The second model maximizes the NPV of the downstream operations for a shorter business planning horizon (five years) constrained by the availability of the logs from the first model. In the integrated approach, all parts of the value chain (forest, transportation, and mills) are driven by final product demand and where the objective is to maximize the profit of the company (NPV of the entire value chain). The demand is only given for the shorter business planning horizon. The two strategies are evaluated using the MIP model, and NPV is used to determine the best practice. According to the results, the NPV can increase up to 5.0% when the proposed integrated strategy is implemented compared to a decoupled strategy. Moreover, the profit for the business period increases up to 8.5%.

Description: Understanding how forests respond to multiple disturbances is becoming increasingly important under global change. We examined the simultaneous influence of canopy decline and deer browsing on regeneration in an old-growth reserve and surrounding managed forest dominated by Fagus sylvatica L. and Abies alba Mill. in Slovenia. We quantified both disturbance processes by measuring characteristics of canopy gaps and reconstructing historical deer densities. Forest response was assessed with repeated measurements of tree regeneration and regeneration patterns within deer exclosures. Most gaps were formed by mortality of A. alba (71%), and gapmaker characteristics suggest that gaps formed slowly and often expanded, resulting in a mosaic of openings covering 17% of the old-growth reserve. Fagus sylvatica dominated the regeneration layer throughout the reserve and recruited to taller height classes over the past 26 years. The recruitment failure of preferred browse species (A. alba and Acer pseudoplatanus L.) in the reserve and the successful recruitment of these species within exclosures indicate that selective browsing by deer has altered the successional response to A. alba decline, facilitating the dominance of F. sylvatica. Given that global change may increase forest decline worldwide and the ubiquitous nature of deer browsing in many temperate forests, understanding their combined effects on forests will become increasingly important.

Description: As fire is a major disturbance in boreal forests, it is now recognized that it has to be taken into account in forest management planning. Moreover, as the time of exposure to fire is related to stand productivity, combining information on productivity and fire should help in assessing the potential to sustainably manage forests. We present a method to assess potential vulnerability to the risk of fire and illustrate it in the boreal coniferous forest of Quebec. This method takes into account some sources of uncertainty related to the estimation of productivity and fire risk. Spatialization of stand productivity from growth and yield curves allowed us to compute the area comprised of productive stands of each district with or without considering fire risk. Results showed that productive area is generally decreasing with decreasing degree-days, increasing elevation, or in relation to surficial geology. Furthermore, districts with moderate to good productivity were found to be vulnerable to fire when burn rates were greater than 0.333%·year–1. Our innovative approach allowed us to assess the vulnerability of the districts to fire and could be helpful in many regions in the context of a projected increase in future area burned under climate change.

Description: Leaf area relationships are important physiologically and ecologically but are not well studied in baldcypress (Taxodium distichum (L.) Rich. var. distichum). Tree leaf area (LA) and leaf area index (LAI) were measured in a wetland in southern Louisiana by dissecting crowns of felled trees and by scaling stand-level measurements with allometry. Branchlet morphology ranged from flat and open with high specific leaf area (87.2 ± 30.7 cm2·g−1; mean ± SD) to scaled with appressed leaves and low specific leaf area (22.1 ± 11.6 cm2·g−1). Leaves were more appressed higher in the canopy. Tree LA was strongly related to sapwood basal area (SBA), and SBA was related to diameter; these allometric relationships enabled estimating LA from diameters. At the plot level, LAI estimated by allometric relationship (ranging from 1.8 to 10.2) was not linearly related to output from an optical canopy analyzer measuring light extinction; ratios of allometric to optical methods were 0.8 for the sparsest plot and 2.4 for the densest plot. LAI was less in deeper flooded plots (3.6 ± 0.6) than in transiently flooded plots (8.4 ± 0.6), but it is unclear whether this represents a difference in maximum LAI or delayed attainment of maximum LAI in lower areas.

Description: In this study, we investigate the use of model-based inference in forest surveys in which auxiliary data are available as a probability sample. We evaluate the effects of model form and sample size on estimators of growing stock volume, based on different types of remotely sensed auxiliary data. The study was performed through Monte Carlo sampling simulation using a two-phase sampling design within a simulated study area resembling the conditions in mid-western Finland. We show that the choice of model has a minor to moderate effect on the precision of model-based estimators. Similarly, the choice of estimator of the variance–covariance matrix of model parameter estimates, which is at the core of uncertainty assessment in model-based inference, was also found to have a minor to moderate effect on the precision of model-based estimators. Regarding sample sizes, the model error contribution to the total variance remains the same regardless of the sample size of the first phase (i.e., the size of the sample of auxiliary data); to reduce the model-error contribution, there is a need to increase the sample size of the second phase (i.e., the size of the sample of field plots for developing regression models). As a baseline for comparisons, model-assisted estimators were applied and found to be about equally precise as the model-based estimators, in accordance with the theory for the case when models are estimated from the sample data.

Description: In this study, we explored the consequences of using leaf-on and leaf-off airborne laser scanning (ALS) data on area-based model outcomes in a lodgepole pine (Pinus contorta var. latifolia Engelm.) dominated forest in the foothills of the Rocky Mountains in Alberta, Canada. We considered eight forest attributes: top height, mean height, Lorey’s mean height, basal area, quadratic mean diameter, merchantable volume, total volume, and total aboveground biomass. We used 787 ground plots for model development, stratified by ALS acquisition conditions (leaf-on or leaf-off) and dominant forest type (coniferous or deciduous). We also generated pooled models that combined leaf-on and leaf-off ALS data and generic models that combined plot data for all forest types. We evaluated differences in ALS metrics and leaf-on and leaf-off model outcomes, as well as the impacts of pooling leaf-on and leaf-off ALS data, creating generic models, and of applying leaf-on models to leaf-off data (and vice versa). In general, leaf-off and leaf-on ALS metrics were not significantly different (p 〈 0.05), except for the 5th percentile of height (coniferous) and canopy density metrics (deciduous). Overall, coniferous leaf-on and leaf-off models were comparable, with differences in relative root mean square error (RMSE) and bias of

Description: Increasing wild ungulate populations in the northern hemisphere led to extensive research on their influence on forest regeneration. According to the results of different studies, high ungulate densities may alter forest structure and composition, as well as inhibit forest regeneration. However, little is known about the long-term impact of large herbivores on forest dynamics at the landscape scale. Therefore, we studied forest regeneration in conifer forests of the highly protected Swiss National Park. We assessed sapling densities and apical shoot loss by repeated systematic sampling in 2003 and in 2011–2012 in two valleys featuring exceptionally high densities of wild ungulates of up to 86 individuals per vegetation-covered square kilometre during summer and 28 individuals per vegetation-covered square kilometre during winter. Mean apical shoot loss ranged between 2.9% and 10.6% depending on study site and assessment year. In addition to the increasing sapling densities, these results suggest that ungulates had little impact on tree establishment in the studied subalpine conifer forests. Additionally, sapling diversity was higher on plots repeatedly influenced by ungulates (apical shoot loss), suggesting rather positive effects of ungulates on sapling diversity. Habitat containing a mixture of forest and grassland without livestock or human disturbance provides a high-quality environment for ungulates, which likely explains the low impact of ungulates on forest regeneration in our study area.

Description: Forest mechanistic wind risk models are widely applied on heterogeneous landscapes, whereas their wind load parameterizations are often derived either from homogeneous stand conditions or from simple forest edge conditions. To evaluate the impact of improving the wind flow representation of the mechanistic wind risk model HWIND on tree damage predictions when applied on heterogeneous environments, we coupled HWIND with the airflow model Aquilon. Aquilon provides to HWIND the velocity profiles and the gust factor (deduced from an approach based on the probability distribution of the wind velocity and on the turbulent kinetic energy). HWIND–Aquilon is compared with HWIND alone on different stand configurations of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) comprising newly clearcuts or shelter stands. Although both models showed the same pattern of differences in edge-tree critical wind speeds with differences in clear-cut length and shelter stand height, the model comparison reveals significant differences in the magnitude of critical wind speeds between them. This discrepancy is explained by the wind velocity and gust factor parameterizations used in HWIND alone, as in other wind risk models that exhibit weaknesses in heterogeneous configurations. This result confirms the need for improving the wind flow representation in mechanistic wind risk models when applied to heterogeneous landscapes.

Description: Deficiency in availability of phosphorus (P) in forest soils of southern China, where Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) stands have been established, greatly affects Chinese fir productivity. Deploying clones with high P-use efficiency could be a more attractive option than P fertilization to enhance the commercial productivity of Chinese fir. Thus, an understanding of the adaptive responses of roots to spatiotemporal variability of P, which is often ignored in previous studies, is essential. In this study, we report the root responses of a Chinese fir clone with high P-use efficiency to the spatially heterogeneous P availability in soil during various periods of time when P availability was controlled. The results showed significantly (p 〈 0.05) more root proliferation in the form of root length, root surface area, root volume, and root dry matter accumulation in P-replete than in P-poor patches when the patch persisted for a short period of time (50 days). As the patches persisted longer (100–200 days), root proliferation in P-replete patches appeared to decline. P-replete patches that persisted for short (50 days) and long (200 days) periods resulted in high root P accumulation, whereas P-replete patches that persisted for 100–150 days resulted in lower root P accumulation than other patches. It seems that the observed responses in the roots of the Chinese fir clone to heterogeneous P availability might include a comprehensive adjustment of root growth and intraroot P translocation in patches so as to maintain internal P homeostasis, as well as a trade-off between energy cost and production of new roots when the patch persists longer.

Description: Management of many dry conifer forests in western North America is focused on promoting resilience to future wildfires, climate change, and land use impacts through restoration of historical patterns of forest structure and disturbance processes. Historical structural data provide models for past resilient conditions that inform the design of silvicultural treatments and help to assess the success of treatments at achieving desired conditions. We used dendrochronological data to reconstruct nonspatial and spatial forest structure at 1860 in fourteen 0.5 ha plots in lower elevation (∼1900–2100 m) ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) forests across two study areas in northern Colorado. Fires recorded by trees in two or more plots from 1667 to 1859 occurred, on average, every 8–15 years depending on scale of analysis. The last fire recorded in two or more plots occurred in 1859. Reconstructed 1860 stand structures were very diverse, with tree densities ranging from 0 to 320 trees·ha−1, basal areas ranging from 0.0 to 17.1 m2·ha−1, and quadratic mean diameters ranging from 0.0 to 57.5 cm. All trees in 1860 were ponderosa pine. Trees were significantly aggregated in 62% of plots in which spatial patterns could be estimated, with 10% to 90% of trees mainly occurring in groups of two to eight (maximum, 26). Current stands based on living trees with a diameter at breast height of ≥4 cm are more dense (range, 175–1010 trees·ha−1) with generally increased basal areas (4.4 to 23.1 m2·ha−1) and smaller trees (quadratic mean diameters ranging from 15.7 to 28.2 cm) and contain greater proportions of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and Rocky Mountain juniper (Juniperus scopulorum Sarg.). This is the first study to provide detailed quantitative metrics to guide restoration prescription development, implementation, and evaluation in these and similar ponderosa pine forests in northern Colorado.

Description: Rothermel’s wildland surface fire spread model is widely used in North America. The model outputs depend on a number of input parameters, which can be broadly categorized as fuel model, fuel moisture, terrain, and wind parameters. Due to the inevitable presence of uncertainty in the input parameters, knowing the sensitivity of the model output to a given input parameter can be very useful for understanding and controlling the sources of parametric uncertainty. Instead of obtaining the local sensitivity indices, we perform a global sensitivity analysis that considers the synchronous changes of parameters in their respective ranges. The global sensitivity indices corresponding to different parameter groups are computed by constructing the truncated ANOVA – high dimensional model representation for the model outputs with a polynomial expansion approach. We apply global sensitivity analysis to six standard fuel models, namely short grass, tall grass, chaparral, hardwood litter, timber, and light logging slash. Our sensitivity results show similarities, as well as differences, between fuel models. For example, the sensitivities of the input parameters, i.e., fuel depth, low heat content, and wind, are large in all fuel models and as high as 85% of the total model variance in the fuel model light logging slash. On the other hand, the fuel depth explains around 40% of the total variance in the fuel model light logging slash but only 12% of the total variance in the fuel model short grass. The quantification of the importance of parameters across fuel models helps identify the parameters for which additional resources should be used to lower their uncertainty, leading to effective fire management.

Description: Improved knowledge of the time scales at which drought stress mostly influences tree growth is crucial for the early detection of forest dieback. This study aimed to evaluate the impact of climate (temperature and precipitation) on vegetation activity (normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI)) of Pinus halepensis Mill. and Pinus pinea L. mixed forest located in western Albania and to assess the drought impact (standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI)) calculated at different time scales (1–12 months) on radial growth (earlywood width, latewood width, and tree-ring width) and vegetation activity of these species. Both vegetation indices showed a negative response to August temperatures, and the EVI responded positively to September precipitation. NDVI and EVI were significantly affected by the SPI in spring and late summer. All tree-ring features in P. halepensis were positively related with EVI in August, whereas P. pinea latewood width showed a significant and positive relationship with NDVI in September. Radial growth of P. halepensis responded significantly to both drought indices in late summer and early autumn, particularly the latewood width. Contrastingly, in P. pinea, only earlywood width showed vulnerability, mostly to the summer SPEI drought indices. These results are relevant to understand the impacts of increased drought intensity and frequency on tree radial growth and vegetation activity in a region that is vulnerable to climate variability.

Description: Fire is a significant agent for the development of boreal and hemiboreal forests, altering soil and light conditions, affecting seedbanks, and removing seed trees. Burned areas should be managed with care, as inappropriate techniques prolong the regeneration period and reduce the diversity and resilience of stands to disturbances. To study the effects of fire and postfire management on the successional changes in regeneration abundance, species composition and tree height sample plots were established in sandy pine forests in northwestern Estonia on areas burned 2 or 22 years ago. Five types of sample plots were established: (i) areas without fire damage, (ii) burned uncleared areas, (iii) burned forest areas cleared after forest fire, (iv) burned uncleared areas with live trees, and (v) burned uncleared areas with dead trees. Three main tree species common to hemiboreal forests were analyzed: Betula spp., Pinus sylvestris L., and Populus tremula L. Results showed that clearing burned areas after wildfire significantly reduced the abundance of regeneration compared with burned uncleared areas but favored height growth of P. sylvestris in later development. To regenerate and maintain mixed stands after wildfire, retaining some residual trees can facilitate regeneration compared with complete clearing, although a dense stand with live trees or a large amount of deadwood can hinder regeneration.

Description: To examine the efficiency of early selection for wood quality traits in the Scots pine (Pinus sylvestris L.) breeding program in Sweden, a total of 778 wood increment cores were sampled from 179 full-sib families in a single progeny trial at 40 years of age. Age trend of inheritance, age–age genetic correlation, and early selection efficiency for eight wood traits including annual ring width, wood density, microfibril angle (MFA), modulus of elasticity (i.e., wood stiffness; MOE), and fibre dimensions were studied. Heritabilities for the eight wood traits reached a plateau between age 5 years and age 15 years, with the highest heritability for radial fibre width and fibre coarseness (∼0.6) and the lowest heritability for ring width (∼0.2). Heritability reached about 0.4 for both wood density and MFA but only reached about 0.3 for MOE. Genetic correlation from early to reference age 30 years reached a very high level (〉0.8) for all eight wood traits at age 5 years. Early selection was effective for wood quality traits in Scots pine, and selection at age 8 years is recommended for MOE in Scots pine.

Description: The potential of Fourier transform near-infrared (FT-NIR) spectroscopy to predict hydraulic traits in Norway spruce (Picea abies (L.) Karst.) sapwood was evaluated. Hydraulic traits tested were P50 (applied air pressure causing 50% loss of hydraulic conductivity) and RWL50 (applied air pressure causing 50% relative water loss). Samples came from 24-year-old spruce clones. FT-NIR spectra were collected from the axial (transverse) and radial surface of each solid wood sample for the prediction of P50 and RWL50. Partial least squares regression (PLS-R) models with cross validation were used to establish relationships between the FT-NIR spectra and the reference data from hydraulic properties analysis. The impact of the wavenumber range and the pretreatment during the PLS-R model development and the differences between the axial and radial surfaces were shown. Based on the values of the coefficient of determination (r2) and the root mean square error of cross validation, predicted results were evaluated as acceptable. The models from the axial surface gave better results than the models from the radial surface for P50 (r2 = 0.65), as well as for RWL50 (r2 = 0.77). The first approach to predict hydraulic properties such as P50 and RWL50 by FT-NIR spectroscopy can be regarded as successful. We conclude that the method has high potential to be put into practice as a rapid, reliable, and nondestructive method to determine P50 and RWL50.

Description: Studies have reported divergent results on the effect of soil fertility and canopy opening on understory density and growth of sugar maple (AS; Acer saccharum Marsh.) and American beech (FG; Fagus grandifolia Ehrh.). The main objective of this study was to evaluate the effect of a gradient of canopy opening and soil fertility on the density and growth of AS and FG saplings in southwestern Quebec, Canada. We investigated 56 stands containing both AS and FG that were subjected to different disturbance history types (DHTs) (UF, unmanaged forest; PC, partial cut; and CC, clearcut) on various soil types. AS and FG absolute and relative sapling density varied greatly among the 56 stands; however, no significant effects of DHT, soil nutrient availability, or their interaction were found. Both species responded positively in terms of radial growth to canopy openings, with FG growth being slightly better than AS growth in PC stands compared with other canopy treatments. Contrary to our hypothesis, AS did not show significantly higher growth than FG following clear-cutting. These results do not support the idea that AS abundance and growth could be promoted by increasing the intensity of the canopy opening during harvest, at least on the generally acidic and base-poor soils that were investigated.

Description: This paper develops a simulation-based optimization supply chain model for supplying sawlogs to a sawmill from a forest management unit. The simulation model integrates the two-way flow of information and materials under the stochastic demand of the sawmill production unit. The dynamic optimization model finds the optimum inventory policy (s, S) that minimizes the total inventory cost for the three supply chain agents — sawmill storage, merchandizing yard, and forest management unit. The model is used to analyze a real sawmill case study in northwestern Ontario, Canada. It was found that the merchandizing yard absorbs shocks of uncertain demand from the sawmill production unit and reduces idle time, but it increases the total cost of the supply chain by $11 802 (about 42%). The optimized model predicts that only 3.5 days of inventory is required at the sawmill storage. The simulation-based optimization supplier model will help in decision-making at the tactical and operational level in the forest products industry supply chain through a two-way flow of information and materials.

Description: The frequency of forest fires is predicted to increase in Canada, which may affect the availability of timber for industrial purposes. We therefore carried out an evaluation of the timber supply vulnerability to current and future fire risk through simplified calculations involving historical forest growth and harvest rates and current and projected forest burn rates. Calculations were performed at the level of forest management areas (FMAs) across the boreal and montane ecozones of Canada. For some FMAs, the vulnerability of timber supply to fire was estimated to be high to extreme by the middle of the century. For those FMAs, the increases in tree growth necessary to negate these risks were generally unrealistic. A modest simulated decrease in tree growth over time, however, was sufficient to raise the vulnerability of many other FMAs from low to moderate. Known biases in the analysis suggest that our assessment might underestimate the level of vulnerability in all FMAs. Other natural disturbances are not included in the analysis but their impact on timber supply may be additive to that of fire. Some adaptation measures to face these increasing risks are discussed.

Description: This paper compares design-based properties of the classical two-phase regression estimator with several nonparametric kernel-based estimators of which k nearest neighbors (kNN) is a special case. Metrics are based on the Euclidean distance applied to either a multidimensional space of explanatory variables or to a one-dimensional space of predictions obtained from a linear model. The main concepts of kernel-based regression estimators are reformulated in the design-based Monte Carlo approach to forest inventory. The results, based on a case study of a forest inventory in Switzerland and extensive simulations, suggest that the commonly used analytical external variance formula may systematically underestimate the true variance for a variety of kernel-based estimators including kNN but that it is still adequate for the classical regression estimator. Although using a bootstrap variance can help to correct this underestimation, it was also found that the bootstrap variance estimates could be unstable if the optimal bandwidth is recalculated in each bootstrap sample. These findings suggest that if the model captures the main features of the underlying process, then it is advisable to use the classical regression estimator, because it performs at least as well as the other techniques and is by far simpler to implement.

Description: Light-emitting diode (LED) technology shows promise for supplementing photosynthetically active radiation (PAR) in forest nurseries because of the potential reduction in energy consumption and an ability to supply discrete wavelengths to optimize seedling growth. Our objective was to examine the effects of light spectra supplied by LED and traditional high-pressure sodium (HPS) lamps on growth and physiology of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and Engelmann spruce (Picea engelmannii Parry ex Engelm.) seedlings. We used three latitudinal sources for each species: British Columbia (BC), Idaho (ID), and New Mexico (NM). Container seedlings were grown for 17 weeks in the greenhouse under an 18 h photoperiod of ambient solar light supplemented with light delivered from HPS or LED. In general, seedlings grown under LED had significantly greater growth, gas exchange rates, and chlorophyll contents than those seedlings grown under HPS. The growth and physiological responses to supplemental lighting varied greatly among species and seed sources. Generally, LED-grown seedlings from BC had the greatest growth and tissue dry mass followed by ID and NM populations. Compared with HPS, the significant increase in seedling growth and concomitant energy savings with LED (29% energy consumption relative to HPS) demonstrates the promise of using LED as PAR supplemental lighting for container seedling production.

Description: Convergence of species composition in regenerating harvested areas and naturally disturbed forest is a critical component of forest management modeled after natural disturbances. We assessed convergence of birds, plants, and habitat structures in aspen (Populus tremuloides) stands harvested with structural retention by Alberta-Pacific Forest Industries Inc. (Al-Pac) 15 years ago with similar aged fire area, and examined a chronosequence of younger and older burned aspen stands from Alberta Biodiversity Monitoring Institute (ABMI) sites. Most habitat structures and many bird and plant species in the 15 year harvest areas were at levels similar to 20–40 year or 〉40 year fire areas. Snags, moss, and lichen cover, and a few groups of species were at lower levels in the harvest areas than comparable aged fire areas or older stands. Agglomerative clustering showed the plant community to be most similar to 〉40 year burned stands, with the bird community intermediate between 〉20 year and

Description: The aim of this study is to analyze the relationships between black spruce (Picea mariana (Mill.) B.S.P.) growth and climate at a large spatial scale in North America’s northeastern boreal forest. The study area (approximately 700 000 km2) is located in the taiga zone of the Quebec – Labrador Peninsula. A network of tree-ring chronologies from 93 black spruce populations was developed. A hierarchical cluster analysis was conducted to analyze tree-ring series affinities, and response functions were calculated to analyze relationships between tree rings and climate. The cluster analysis results showed well-marked spatial affinities among the tree-ring series. These affinities were strongly linked with the spatial variability of the relationships between tree rings and climate. The interannual growth variations were governed mainly by the temperature variables that preceded the growing season (November (negative influence), December–January (positive influence), and April (positive influence)). The growing-season temperature (July temperature) mainly influenced the northernmost populations. Relationships between tree rings and climate in the northeastern boreal forest varied at a large spatial scale. This variability was expressed by a north–south contrast, which appears to be related to a temperature gradient, and an east–west contrast linked to a humidity gradient, which favors winter snow cover.

Description: As concerns rise over potential effects of greenhouse gas related climate change on terrestrial ecosystems, forest managers require growth and yield modeling capabilities responsive to changing climate conditions. Our goal was to develop prediction models of site index for eastern US forest tree species with climate and soil properties as predictors for use in predicting potential responses of forest productivity to climate change. Species-specific site index data from the USDA Forest Service Forest Inventory and Analysis (FIA) program were linked to contemporary climate data and soil properties mapped in the USDA Soil Survey Geographic (SSURGO) database. Random forest regression tree based ensemble prediction models of site index were constructed based on 37 climate-related and 15 soil attributes. In addition to a species-specific site index, aggregate models were developed for species grouped into two broad categories: conifer (softwood) and hardwood (broadleaved) species groups. Species-specific models based on climate and soil predictors explained the most variation in site index of any models tested (R2= 62.5%, RMSE = 3.2 m). Comparable results were found when grouping species into conifer and hardwood groups (R2= 63.9%, RMSE = 4.6 m for conifers; R2= 35.9%, RMSE = 4.2 m for hardwoods). Model predictions based on multiple global circulation models (GCMs) and Intergovernmental Panel on Climate Change (IPCC) development scenarios were tested for statistical significance using bootstrap resampling methods. Results showed significant increases over the 21st century in mean site index for conifers between +0.5 and +2.4 m. Over the same time period, mean hardwood site index showed decreases of as much as −1.7 m for the scenarios tested. The results demonstrate the utility of using climate and soils data in predicting site index across a large geographic region, and the potential of climate change to alter forest productivity in the eastern US. Additional investigation is needed to interpret spatial patterns and ecological relationships related to predictions from this type of model.

Description: The European ash (Fraxinus excelsior L.) dieback is an acute forest pathology problem caused by the invasive ascomycete Hymenoscyphus fraxineus (T. Kowalski) Baral, Queloz, Hosoya. There are no practical solutions yet, but selection for resistant genotypes and intensive care have been highlighted as options. Our aim was to assess the disease mitigation potential of silvicultural harvests, which influence stress levels in retained trees. We annually monitored 577 retention trees on Estonian cut areas for 13 years, including 9 years impacted by the dieback. Sixty-five percent of the trees survived and 15% retained healthy crown, despite all sampled trees being infected. The damage was smallest in the trees retained near precut edges. Former forest-interior trees that were left in central parts of the cut areas suffered high initial damage but smaller disease progression than trees near postcut edges. Tree size and secondary infection by Armillaria spp. were not related to disease progression, but rapid decline was observed in the region with the highest density of ash trees retained. Our results indicate a significant silvicultural potential for tree resistance. Ash trees tend to be healthiest in open conditions, which probably inhibit the pathogen and provide better resources for the tree. Location near precut edges is an important tree retention criterion, which can mitigate initial harvest-induced stress.

Description: Long-term exploitation of boreal ecosystems often results in a reduced range of ecological conditions that threatens several species. In most boreal jurisdictions, the northern extent of commercial forestry corresponds to economical rather than ecological considerations. Our general objective is to offer guidance for sustainable boreal forest management by using a biodiversity criterion based on three indicators. The first two indicators are part of a coarse filter referring to the proportion and fragmentation of tall, dense forest habitats, whereas a third one uses a fine filter for specific requirements of boreal caribou. We applied the methodology with and without anthropogenic disturbances on 1114 land districts to contrast the preindustrial potential and current capacity of Quebec’s boreal forest to support forest management. Originally, 826 districts (74%) were above the 20% cutoff value for the minimum proportion of tall, dense forest habitats. Among the 567 districts currently under forest management, 45 did not reach this value because of past anthropogenic disturbances. Originally, 88% of the districts had sufficient undisturbed habitats to maintain caribou populations, but anthropogenic disturbances reduced this proportion to 51%. The proposed methodology could contribute to delineating areas where sustainable forest management can be implemented. Our results also clearly show that management targets of the last decades were insufficient to prevent loss of habitats below strict minimum ecological thresholds. Our approach offers a general framework that could be adapted to other forested regions to attain similar biodiversity conservation objectives.

Description: The boreal forest ecosystem is one of the largest frontier forests of the world, providing many ecological services to society. Boreal forests are also economically important, but forest harvesting and management become increasingly difficult when one moves from south to north in boreal environments. An approach was thus developed to assess the suitability of land units for timber production in a sustainable forest management (SFM) context in the northern boreal forest of Quebec (Canada). This area includes all of Quebec’s spruce – feather moss bioclimatic domain (closed forest), as well as the southern portion of the spruce–lichen bioclimatic domain (open woodland). Four criteria specific to the biophysical aspects of SFM were evaluated in 1114 land districts: physical environment, timber production capacity, forest vulnerability to fire (e.g., probability that it reaches maturity), and conservation of biodiversity. Indicators and acceptability cutoff values were determined for each selected criterion, and a sequential analysis was developed to evaluate if a land district has the potential to be sustainably managed. This analytical process led to the classification of land districts into three categories: slightly sensitive (SFM possible); moderately sensitive (SFM possible under certain conditions); and highly sensitive (SFM not possible). The results show that 354 land districts were highly sensitive, 62 due to physical constraints (7.5% of the area), 130 due to insufficient potential productivity (15.4% of the area), 92 due to insufficient potential productivity to account for the fire risk (13.8% of the area), and 70 due to an insufficient proportion of tall and dense forest habitats (7.7% of the area — biodiversity criterion). This work provides scientific background to proposing a northern limit for forest management activities in Quebec. The developed approach could be useful in other jurisdictions to address similar issues.

Description: A stationary response of tree radial growth to climatic variables is assumed as a basis for climatic reconstructions and future growth projections in response to climate change. Mountain hemlock (Tsuga mertensiana (Bong.) Carrière) trees on the western slopes of the North Cascade Range (Washington, USA) were examined for stability in growth response to climatic influences at a small spatial scale. Moving correlation functions demonstrate that climate–growth interactions are nonstationary over time, alternating between periods of significant and nonsignificant responses. Correlations between growth and winter precipitation have weakened, becoming statistically insignificant in the last decade, but correlations with spring temperature and previous-year summer temperature have strengthened, becoming statistically significant. The Pacific Decadal Oscillation influences patterns in climate–growth correlations but does not seem to account for the most recent changes in correlation strength. At an interannual scale, growth differs between El Niño Southern Oscillation phases, specifically between El Niño and La Niña years and between La Niña and neutral phase years. The variability in growth response to climate at interannual and interdecadal time frames, especially with the climate changes emerging in recent decades, will challenge the reliability and accuracy of reconstruction and predictive models.

Description: This study characterized associations between climate variables and radial growth of four oak species at sites distributed across central and eastern North America. Tree-ring data were obtained from 24, 29, 33, and 55 sites for Quercus prinus L., Quercus velutina Lam., Quercus macrocarpa Michx., and Quercus stellate Wangenh., respectively. Pearson’s correlation coefficients were computed between radial growth and monthly and seasonal temperature and precipitation. Growth was most strongly and consistently correlated with precipitation and temperature during the early growing season (May to July). Coincident positive correlations with precipitation and negative correlations with temperature indicate that this relationship is mediated by site water balance. The combination of this plausible cause–effect mechanism and extensive spatial replication of these correlations suggest that they reflect cause–effect relationships. Growth of Q. stellata was correlated with precipitation during the dormant season, suggesting that stored soil water is important for growth of this species in the southern Great Plains. Despite substantial spatial variation in temperature and growing-season initiation between sites in Texas and Manitoba, Canada, there was little variation in the phenology of growth–climate associations; growth–climate correlations were strongest during the same May–July period at all sites. Results of this study support the hypothesis that temperate zone ring-porous oak species have similar phenology of growth–climate correlations and can be treated as a biologically meaningful functional group in forest simulation models.

Description: Wildfires play a major role in driving vegetation changes and can cause important environmental and economic losses in Mediterranean forests, especially where the dominant species lacks efficient postfire regeneration mechanisms. In these areas, postdisturbance vegetation management strategies need to be based on detailed, spatially continuous inventories of the burned area. Here, we present a methodology in which we combine airborne LiDAR and multispectral imagery to assess postfire regeneration types in a spatially continuous way, using a Mediterranean black pine (Pinus nigra Arn ssp. salzmannii) forest that burned in 1998 as a case study. Five postfire regeneration types were obtained by clustering field-plot data using Ward’s method. Two of the five regeneration types presented high tree cover (one clearly dominated by hardwoods and the other dominated by pines), a third type presented low to moderate tree cover, being dominated by hardwoods, and the remaining two types matched to areas dominated by soil–herbaceous or shrub layers with very low or no tree cover (i.e., very low to no tree species regeneration). These five types of regeneration were used to conduct a supervised classification of remote sensing data using a nonparametric supervised classification technique. Compared with independent field validation points, the remote sensing based assessment method resulted in a global classification accuracy of 82.7%. Proportions of regeneration types in the study area indicated a general shift from the former pine-dominated forest toward hardwood dominance and showed no serious problems of regeneration failure. Our methodological approach appears to be appropriate for informing postdisturbance vegetation management strategies over large areas.

Description: Mechanisation is increasingly used in European forest management, but so far, few studies have investigated the combined effects of stand attributes and skid trails on stand-scale ground flora diversity. Our study assessed the effects of stand attributes (age, stand type, basal area) and skid trail area on ground flora diversity in 400 m2 plots in oak forest stands in the northern half of France. We calculated the richness and abundance of ecological groups based on successional status and light preference. We developed and compared generalized linear models and assessed the magnitude of the effects of each variable. At the ecological group level, floristic variations among plots were mostly associated with stand attributes (stand type or basal area). Although we found non-negligible effects of skid trails on all herbaceous groups, these effects disappeared when tree stand attribute effects were incorporated into the statistical models. At the species level, when incorporating stand attribute effects into the models, skid trail area had weak or inconclusive effects on species (occurrence 〉 25%) abundance. Because mechanisation is a recent practice in European forests, stronger effects might be expected in the long term.

Description: Two ends of the fire regime spectrum are a frequent low-intensity fire regime and an infrequent high-intensity fire regime, but intermediate fire regimes combine high- and low-severity fire over space and time. We used fire-scar and tree-age data to reconstruct fire regime attributes of mixed-conifer and aspen forests in the North Rim area of Grand Canyon National Park, with a goal of estimating patch sizes of historical high-severity fire and comparing them with modern patch sizes. We used three methods based on (i) aspen groves, (ii) even-aged stands, and (iii) inverse distance weighting, to estimate occurrence and patch sizes of historical high-severity fire. Evidence of high-severity fire was common in the 1800s, and high-severity fire years were associated with drought. High-severity fire patch sizes likely ranged from 10−1 to 102 ha. However, the forest is quite young, and we cannot rule out a historical large high-severity fire that could have reinitiated much of the 1400 ha study area. Fire scars, which are indicative of low-severity fire, were also common. Historical fire was likely heterogeneous across the landscape. Maintaining heterogeneity of fire severity, size, and frequency would promote heterogeneity of forest structure and composition and resilience to future disturbances.

Description: We analysed climate–growth relationships for two ring-porous oak species (Quercus robur L. and Q. pyrenaica Willd.) at one site in northwestern Spain. Increment cores from 12 living trees per species were taken for ring and earlywood vessel measurements, considering three width variables (for earlywood, latewood, and the whole ring) and six anatomical variables (based on vessel area distribution, number of vessels, and conductivity) in the earlywood. We used standard dendrochronological procedures and compared each mean series with meteorological records of temperature, precipitation, and estimates of soil water content. Earlywood width was negatively related to precipitation in the previous late season for Q. robur, but it was controlled by the previous spring temperature for Q. pyrenaica. These responses were highly dependent on vessel number and probably related to carbohydrate storage dynamics but differed between species. Vessel size showed a stronger relationship to climate and was mainly coupled to water excess during the winter for Q. robur but dependent on quiescence temperature for Q. pyrenaica; also, climatic signal in vessel size was maximized by the largest vessels for Q. pyrenaica but only increased slightly for Q. robur. Consequently, vessel parameters showed a much stronger climate signal than ring width and were successful at highlighting the differences between both oak species.

Description: Nitrogen (N) deposition has been shown to affect soil carbon (C) and N cycling in subtropical forests; however, the underlying microbial mechanisms are poorly understood. We used patterns of community-level physiological profiles and enzyme activities to assess the relative effects of the addition of four N levels (0, 50, 100, and 150 kg·ha−1·year−1) on the soil microbial community in three forest stands (pine, mixed, and broadleaf forests) in southern China, where the forests have been experimentally manipulated for over 8 years. In pine forests, N50 addition significantly increased microbial biomass carbon (MBC) concentration but decreased soil pH levels. N100 addition significantly increased soil peroxidase activity but decreased soil β-1,4-glucosidase activity. In broadleaf forests, N addition increased soil dissolved organic carbon (DOC) concentration and polyphenol oxidase activity but decreased soil MBC concentration and soil pH levels. N addition also significantly increased soil microbial metabolism activity (expressed as average well color development) in pine forest and broadleaf forest soils. However, the mixed forests responded slowly to N additions and exhibited no significant response of C-utilization profiles and soil enzyme activities. Principal component analysis of C-utilization data separated microbial communities with respect to N addition and forest successional stage. In addition, microbial C utilization was driven by soil pH levels. Although enzyme activities were correlated with soil MBC and microbial biomass nitrogen concentrations, stepwise regression results indicated that soil total carbon contents that were integrated with soil pH levels were key integrators of soil enzyme activities. Our results suggest that soil acidification due to N addition increased soil bacterial C utilization and enzyme activities.

Description: The United States (US) Lacey Act 2008 amendment (LAA) is a timber legality regulation that requires US importers to monitor and minimize the risk of illegally harvested wood products within their supply chains. This paper empirically examines the effect of the LAA on Chinese companies’ export costs to the US. The study uses 138 responses from two surveys in Shanghai, China, in 2013, i.e., 5 years after the LAA was implemented. Given the high proportion of zero export increase indicated by the Chinese companies, a zero-inflated ordered probit model was used to model Chinese companies’ export cost increases to the US. The research results demonstrate that pre-LAA raw material sourcing patterns are primary indicators of the respondents’ export cost increase to the US as a result of the LAA. From the results, it can be inferred that log and lumber importers from suspect regions are taking additional measures, by changing their procurement practices, to ensure the legality of their raw material, which is adding to their cost structure. The results also indicate that smaller companies, given their flexibility with raw material procurement, were less likely to experience a post-LAA cost increase relative to their larger counterparts.

Description: Urban forests, which are highly valuable for the urban environment, include trees from city streets that might be susceptible to wood-decay fungi. Fungal endophytes can colonize healthy plant tissues without causing external disease symptoms in standing trees. In this study, the diversity of endophytes isolated from wood of Platanus acerifolia (Aiton) Willd. from Buenos Aires, Argentina, is described and related to different levels of urban disturbance, tree age, and presence of wood-decay basidiomycetes. Samples were obtained from 28 asymptomatic trees (1643 wood core fragments) and 75 symptomatic trees (1516 wood sample fragments) from four sites with different levels of human disturbance. Fungal isolates were morphologically identified, and potential wood-decay isolates were phylogenetically analyzed. Twenty-seven endophytic taxa, including five basidiomycetes, were identified. The multivariate analysis suggested that the endophyte community of wood is highly influenced by the level of urban disturbance, followed by tree age and presence of potential pathogenic basidiomycetes.

Description: Silvicultural treatments recommended to reduce damage by spruce budworm (SBW; Choristoneura fumiferana Clemens) include reducing balsam fir (Abies balsamea (L.) Mill.) abundance and age and increasing spruce (Picea spp.) and hardwood content. To evaluate the effect of these measures on forest timber supply, we assessed stand characteristics, disturbance history, and timber supply for an intensively managed eastern Quebec forest from 1985 to 2004, encompassing a major SBW outbreak. During this time, mean stand age declined from 55 to 51 years, and proportions of areas in balsam fir stands declined (42% to 27%), spruce–fir stabilized (12% to 11%), and mixedwoods increased (32% to 52%). We estimated forest vulnerability using softwood volume reductions following simulated outbreak scenarios of different severity (low, moderate, and high) and different effects of hardwood content in reducing spruce–fir defoliation. Volume reductions for outbreaks simulated to begin in either 1985 or 2004 were similar, ranging from 15%–46% (no hardwood effect in reducing defoliation) to 13%–39% (given a maximum hardwood content effect) for light and severe outbreaks, respectively. Considering the net detrimental effect of increased hardwood content on softwood timber supply, we question the dividends of promoting hardwoods and recommend increasing the combined use of plantations and weeding treatments to increase spruce content.

Description: We analyzed a series of increment cores collected from 260 adult dominant or co-dominant quaking aspen (Populus tremuloides Michx.) trees from national forests across Colorado and southern Wyoming in 2009 and 2010. Half of the cores were collected from trees in stands with a high amount of crown dieback, and half were from lightly damaged stands. We define the level of stand damage based on stand survey data in which lightly damaged stands had average crown dieback of 16% and heavily damaged stands averaged 41%. Upon analysis, two-thirds of the cores collected did not exhibit radial growth correlated with region-wide patterns (e.g., climate) and were classified as having a low cohesive response. The site variable most predictive of whether a stand exhibited high cohesive response or low cohesive response was site elevation, followed by aspect, slope, and canopy closure. Sites with high cohesive response stands were more likely to have aspen bark beetle damage, white rot, and Cryptosphaeria canker. We did not detect relationships between tree growth and summer precipitation from 1900–2008, but there was a relationship between growth and annual precipitation. A growth model included maximum May and July temperatures, as well as the current and previous year’s annual precipitation.

Description: LiDAR-based techniques to estimate forest variables at the stand level require accurate calibration through ground truth data. One purpose of this study was to verify whether angle count samples can be used as suitable ground truth to calibrate LiDAR-based models for timber volume estimation. Volume data were acquired on the ground for 79 plots in the Latemar forest (province of Bolzano, Italian Alps). A simple linear regression model, using the sum of all of the tree canopy heights in the plot as the explanatory variable, was adopted. As angle count samples have no fixed area, three different methods to approximate their size were compared. The angle count sample area can be properly approximated by visual assessment of the tree size classes and by callipering the largest tree in the plot. The results show that angle count sampling can be an efficient solution to calibrate LiDAR-based models: they produced fair estimates at the plot level (relative root mean square error (RMSE), 26.6%) that were better than fixed-radius plot estimates with full callipering (RMSE, 29.7%). Estimate uncertainty at increasingly large forest stand areas was also calculated by means of a simulation procedure. It showed that low uncertainty (standard error of estimate = approximately 2%) could be reached at a forest compartment level (19 ha on average).

Description: Protected forest areas (PFAs) are key features of biodiversity conservation, and knowledge about long-term development is crucial in evaluating their efficiency and management needs. Longitudinal data on forest structure in PFAs is uncommon and often from small areas. Here we use data from the Swedish National Forest Inventory to study changes in more than 750 000 ha of PFAs over 60 years. Structures important for biodiversity, e.g., number of large trees and the volume of hard deadwood, including both standing and down wood, have more than doubled. The initial volume of deadwood, however, was very low. The overall tree species composition was stable over time, and only among the largest trees were there indications of a shift towards the late successional Norway spruce (Picea abies (L.) Karst.). Deadwood increased independent of species, size of wood, and site characteristics. This increase was positively related to the volume of living trees and forest age. We conclude that Swedish PFAs, in the absence of active management and under fire suppression at the landscape scale, develop structural components that are crucial for conservation of biodiversity. However, although tree species composition appears stable, present disturbance regimes in the PFAs are considerably different from those in naturally dynamic forests, which may have implications for long-term biodiversity maintenance.

Description: Boreal ecosystem functioning is largely controlled by disturbance dynamics. There have been efforts at adapting forest management approaches to emulate natural disturbance effects, as this is expected to maintain ecosystem resilience. In many instances, this involves resorting to partial cutting strategies that are likely to increase windthrow losses. The objective of this study was to determine the effects of alternative silvicultural practices on windthrow damage and how these effects vary with the scale of treatment. The study was conducted in the Quebec North Shore region (Canada), an area dominated by balsam fir (Abies balsamea (L.) Mill.) and accompanied by black spruce (Picea mariana (Mill) B.S.P.). Four different silvicultural treatments (overstory removal, heavy partial cutting, and two patterns of selection cutting) and control areas were implemented in 2004 and 2005. The experiment used a nested approach where treatment at the plot level was independent and yet nested within the block-level treatment. At the block level, treatments were applied over 10–20 ha units, leaving a small portion of the block for a smaller application of each treatment (plot scale, 2500 m2). Inventory was carried out before harvesting and monitoring was done yearly after harvesting, with the aim to better understand the plot- and block-level factors that drive windthrow damage levels and the effects of alternative silvicultural treatments. Results after 6–7 years show that basal area proportion windthrown differs substantially between treatments, as well as between treated sites and control sites. Windthrow levels were higher under heavy cuts relative to selection cuts and also increased with balsam fir proportion. Windthrow proportions were better correlated to block-level treatment than plot-level treatment, showing that the environment surrounding the treated plot can have an important effect on windthrow losses. Overall, the selection cutting system, particularly SC2, retains the most green-tree basal area and thus best meets the management objective of retaining old-growth attributes. A simple empirical model was calibrated that could aid in hazard rating.

Description: Climate change may inhibit tree regeneration following disturbances such as wildfire, altering post-disturbance vegetation trajectories. We implemented a field experiment to examine the effects of manipulations of temperature and water on ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings planted in a low-elevation, recently disturbed setting of the Colorado Front Range. We implemented four treatments: warmed only (Wm), watered only (Wt), warmed and watered (WmWt), and control (Co). We found that measures of growth and survival varied significantly by treatment type. Average growth and survival was highest in the Wt plots, followed by the Co, WmWt, and Wm plots, respectively. This general trend was observed for both conifer species, although average growth and survival was generally higher in ponderosa pine than in Douglas-fir. Our findings suggest that warming temperatures and associated drought are likely to inhibit post-disturbance regeneration of ponderosa pine and Douglas-fir in low-elevation forests of the Colorado Front Range and that future vegetation composition and structure may differ notably from historic patterns in some areas. Our findings are relevant to other forested ecosystems in which a warming climate may similarly inhibit regeneration by dominant tree species.

Description: Biomass combustion is considered to be carbon neutral, but intensive biomass harvesting may negatively impact carbon stocks in forest soil and vegetation, which can offset the benefits of substituting fossil fuels with biomass. Here we evaluated conventional stem-only harvesting, whole-tree harvesting (WTH), and WTH excluding needles in terms of timber yield, biomass harvests, and forest carbon sequestration. We simulated harvest scenarios in current and changed climates with a process-based growth model (PipeQual) that was integrated with models describing soil decomposition (ROMUL) and soil water dynamics. Furthermore, we compared gains and losses of forest carbon with reductions in fossil-fuel emissions that result from using harvested biomass for energy production. WTH negatively affected stand growth, biomass, and soil carbon stock; negative effects on growth and biomass can be reduced by leaving nitrogen-rich needles behind during WTH. In a changed climate, organic-matter decomposition and nitrogen mineralization accelerated and tree growth was enhanced, increasing the carbon stock of trees and slightly decreasing the soil carbon stock. In the changed climate, WTH had less influence on forest growth and a similar influence on soil carbon sequestration than in the current climate. In the current climate, the WTH decreased the forest carbon stock by, on average, 26.8 Mg C·ha−1 over the rotation period. If harvested forest residues are used for energy production instead of fossil fuels, emissions decline by 19 Mg C·ha−1 (when WTH is applied over a rotation period). Thus, our analysis suggests that using forest residues for energy production leads to a net increase in carbon emissions.

Description: Quantifying variation in the wood chemical traits of trees is critical for parameterizing forest biogeochemical budgets and models. Available data on wood chemical traits are based largely on samples taken from main stems; few studies have evaluated how wood chemical traits vary among major woody tissue types. We examined variation in wood carbon (C) and nitrogen (N) concentrations in 17 temperate tree species across five woody tissue types: sapwood, heartwood, small branches, coarse roots, and bark; analyses were corrected for losses of volatile C. Both C and N varied significantly among tissue types, but differences were driven mainly by high C and N in bark, a pattern observed for nearly all species. Among nonbark tissue types, bivariate correlations among sapwood, heartwood, small branches, and coarse roots were highly significant and positive for wood C (r = 0.88–0.98) and N (r = 0.66–0.95) concentrations. We suggest that intraspecific variation in C across tissue types is less important than interspecific variation for assessment and modeling of forest-level C dynamics. In contrast, differences in N among tissue types were larger and appeared to be more important to incorporate into forest-level nutrient assessments and models. Our results suggest that, with the exception of bark, wood chemical trait values derived from stemwood can be used to accurately represent whole-tree trait values in models of forest C and N stocks and fluxes, at least for temperate species.

Description: Tree growth at the treeline ecotone is known to be sensitive to climate variability and is thus considered to be a worldwide biomonitor of climate change. However, our understanding of within-region variation in growth responses through space and time is limited. A dry south-facing slope dominated by Pinus wallichiana A.B. Jacks. and a wet north-facing slope dominated by Abies spectabilis (D. Don) Spach in Nepal, central Himalaya, were used to analyze the intersite (i.e., dry vs. wet sites) and intrasite (i.e., treeline vs. forest line elevations) tree-growth relationships, as well as response to monthly and seasonal temperature and precipitation at annual and bidecadal time scales. At both study sites and at two elevations within each site, growth can be strongly affected by growing-season and nongrowing-season factors; however, there are inconsistencies in terms of the climate–growth relationship across space and over time. At the dry site, only a weak positive growth response to summer temperature is observed. At both sites, there is a negative growth response to winter precipitation at both high and low elevations, and this response is markedly independent of the summer and winter temperature trends of the respective site. At the wet site, growth at the higher elevation is negatively correlated to the early summer temperature, whereas a positive growth response to spring precipitation is observed at the lower elevation, indicating a possible drought effect. The results illustrate how different climatic drivers may govern tree-growth responses both between sites with contrasting climates within a region and along elevational gradients within the treeline ecotone. This underlines the need for multiscale studies and a focus on multiple climate variables when analyzing treeline ecotone responses to climate change.

Description: Numerous factors contribute to the variability in treeline change; however, the potential role of insect predation in limiting seed productivity is not well documented. Conditions for seed germination, establishment, and survival are not limiting at the Mealy Mountains treeline (Labrador, Canada), but seedlings are rarely encountered, suggesting a seed-related bottleneck to recruitment. Mature cones were collected in 2008 from four tree species (black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.), balsam fir (Abies balsamea (L.) Mill.), eastern larch (Larix laricina (Du Roi) K. Koch), and white spruce (Picea glauca (Moench) Voss)) across three treeline zones (forest, transition, and krummholz) to assess potential seed limitation. During that year, an unexpectedly high diversity of insect larvae caused extensive reproductive loss and damaged the cones of ∼85% of trees sampled, confirming that treeline change models should include seed predation. Seed germination was low and variable in all treeline zones, although significantly higher in black spruce and eastern larch. Most reproductive quality measures decreased significantly with elevation, although no differences among zones or tree species in the percentages of seeds damaged by insects were found (mean ± standard deviation: 31% ± 23%). Based on tree density and seed production, black spruce is predicted to lead the treeline expansion in the Mealy Mountains. Although climate warming may create conditions conducive for increased seed production, predispersal seed predation may limit future treeline expansion.

Description: Tree mortality is a vital component of forest management in the context of prescribed fires; however, few studies have examined the effect of prefire tree health on postfire mortality. This is especially relevant for sugar pine (Pinus lambertiana Douglas), a species experiencing population declines due to a suite of anthropogenic factors. Using data from an old-growth mixed-conifer forest in Sequoia National Park, we evaluated the effects of fire, tree size, prefire radial growth, and crown condition on postfire mortality. Models based only on tree size and measures of fire damage were compared with models that included tree size, fire damage, and prefire tree health (e.g., measures of prefire tree radial growth or crown condition). Immediately following the fire, the inclusion of different metrics of prefire tree health produced variable improvements over the models that included only tree size and measures of fire damage, as models that included measures of crown condition performed better than fire-only models, but models that included measures of prefire radial growth did not perform better. However, 5 years following the fire, sugar pine mortality was best predicted by models that included measures of both fire damage and prefire tree health, specifically, diameter at breast height (DBH, 1.37 m), crown scorch, 30-year mean growth, and the number of sharp declines in growth over a 30-year period. This suggests that factors that influence prefire tree health (e.g., drought, competition, pathogens, etc.) may partially determine postfire mortality, especially when accounting for delayed mortality following fire.

Description: Empirical knowledge of long-term ecosystem response to single and compound disturbances is essential for predicting disturbance effects and identifying management practices to maintain productive capacity of managed and restored landscapes. We report on soil, foliar nutrition, and regeneration growth response to wildfire, clearcut harvesting, and postfire salvage logging, as well as undisturbed control stands within the first year following disturbance and 10–11 years after disturbance in trembling aspen – white spruce mixedwood forests near Lesser Slave Lake, north-central Alberta, Canada. The compound disturbance of salvage logging resulted in greater long-term impacts on forest floor properties than either wildfire or harvesting alone. Changes in forest floor properties such as carbon and nitrogen pools and cation exchange capacity under salvage logging have persisted for 10 years and exhibit a different recovery trajectory than fire or harvesting. Forest floor properties under harvesting, including depth, carbon content, pH, extractable ammonium, and extractable sulphur, were not different from the control condition 10 years after harvest. Effects on soil and foliar nutrition were not reflected in productivity (height and diameter) of regenerating vegetation. Our results show differences between short- and long-term responses to disturbance, among single natural and anthropogenic disturbances, and among single and compound disturbances.

Description: Forest growth and yield models that incorporate common silvicultural practices are essential for practicing intensive forest management. We present models for growth response to a wide range of silvicultural treatments in loblolly pine (Pinus taeda L.) plantations. Baseline models for basal area, dominant height, and survival were fitted using data from across the southeastern United States. Growth models for treated stands were developed by multiplying baseline models with modifier response functions accounting for effects of thinning, fertilization, and control of competing vegetation. Response to early control of competing vegetation was incorporated into baseline models through multiplier factors that were calculated from growth differences between treated and untreated stands. The thinning response function included duration and rate parameters and was sensitive to stand age at the time of thinning, time since thinning, and intensity of thinning. Fertilization response functions were based on the Weibull distribution; the magnitude of responses varies with time since application of fertilizers, type of fertilizer, and rate of application. A difference function, derived from a differential equation with age, initial stand density, and site index as predictors, served as the baseline survival model. The survival model was adjusted for thinning treatment by including an additional independent variable that represents thinning intensity. The resulting models were able to predict growth response when single, as well as multiple, treatments were applied.

Description: Carbon emission from hardwood lumber processing in different-sized sawmills under varying energy sources, management strategies, and potential carbon offsetting capacity through useful life (service life) of lumber in the northeastern United States was analyzed using analytical statistics such as analysis of variance (ANOVA), mixed-effect model, principal component analysis, and Monte Carlo simulation. Data obtained from a regional sawmill survey (Pennsylvania, New York, Ohio, and West Virginia), energy audit of sawmills, public databases, and relevant literature were analyzed for the gate-to-gate life cycle inventory framework. Results showed that mean carbon emission (megagrams (Mg) per thousand cubic metres (TCM)) for lumber processing significantly differs among sawmill sizes. The total carbon emission from electricity consumption and wood residue of lumber processing was approximately 62.5%, 80.3%, and 66.2% of carbon stored in lumber processed for small, medium, and large sawmills, respectively. Efficient management and potential opportunities of improvement in sawmills can significantly reduce carbon emission (10.96% ± 1.57%) from hardwood lumber processing. Carbon stock from lumber production could be enhanced by either reducing carbon emission from energy consumption or decreasing lumber export quantity. The carbon emission–loss ratio (CELR) suggested that after 100 years, nearly 50% of carbon stored in lumber would be still available for carbon accountability. Electricity generation from either a single resource (natural gas) or mixed resources as is the case in RFC EAST (eGrid subregion) would be beneficial in lowering carbon emission from sawmill processing.

Description: In northern hardwood forests, treemarkers are responsible for selecting the trees to be harvested during commercial logging operations. They often select trees based on the presence and severity of defects, information that is used to assign trees to two or more vigour classes (reflecting the risk of dying or declining in growth) and two or more quality classes (reflecting the potential for recovering valuable sawlogs). Using these classes can simplify the tree selection process, but some classification systems may include superfluous classes beyond what is required to explain the variation in tree value. In this paper, we present a parsimonious classification system for sugar maple (Acer saccharum Marsh.) trees using formal classification analyses of empirical product recovery data. We also calculated the net value of trees in each class and assessed which defects affect tree value. Our results show that relatively few defects affect tree value, indicating that treemarkers should use a simpler classification system to describe the vigour and quality of trees. Specifically, we found that the best system contains just three classes: high vigour-high quality, low vigour-high quality, and low vigour-low quality. The use of this simple, easily implemented system would improve the ability of treemarkers to recognize the value of sugar maple trees when selecting the trees to be harvested during commercial logging operations.

Description: Incident management teams (IMTs) are responsible for managing the response to wildfires. One of the objectives of IMTs is the protection of assets and infrastructure. In this paper, we develop a mathematical model to assist IMTs in assigning resources to asset protection activities during wildfires. We present a mixed integer programming model for resource allocation with the aim of protecting the maximum possible total value of assets. The model allows for mixed vehicle types with interchangeable capabilities and with travel times determined by vehicle-specific speed and road network information. We define location-specific protection requirements in terms of vehicle capabilities. The formulated model extends classic variants of the team orienteering problem with time windows. The model capabilities are demonstrated using a hypothetical fire scenario impacting South Hobart, Tasmania, Australia. Computational testing shows that realistically sized problems can be solved within a reasonable time.

Description: Undetected trees and inaccuracies in the predicted allometric relationships of tree stem attributes seriously constrain single-tree remote sensing of seminatural forests. A new approach to compensate for these error sources was developed by applying a histogram matching technique to map the transformation between the cumulative distribution functions of crown radii extracted from airborne laser scanning (ALS) data and field-measured stem diameters (dbh, outside bark measured at 1.3 m aboveground). The ALS-based crown data were corrected for the censoring effect caused by overlapping tree crowns, assuming that the forest is an outcome of a homogeneous, marked Poisson process with independent marks of the crown radii. The transformation between the cumulative distribution functions was described by a polynomial regression model. The approach was tested for the prediction of plot-level stem number (N), quadratic mean diameter (DQM), and basal area (G) in a managed boreal forest. Of the 40 plots studied, a total of 18 plots met the assumptions of the Poisson process and independent marks. In these plots, the predicted N, DQM, and G had best-case root mean squared errors of 299 stems·ha−1 (27.6%), 2.1 cm (13.1%), and 2.9 m2·ha−1 (13.0%), respectively, and the null hypothesis that the mean difference between the measured and predicted values was 0 was not rejected (p 〉 0.05). Considerably less accurate results were obtained for the plots that did not meet the assumptions. However, the goodness-of-fit of the predicted diameter distribution was especially improved compared with the single-tree remote sensing prediction, and observations realistically obtainable with ALS data showed potential to further localize the predictions. Remarkably, predictions of N showing no evidence against zero bias were derived solely based on the ALS data for the plots meeting the assumptions made, and limited training data are proposed to be adequate for predicting the stem diameter distribution, DQM, and G. Although this study was based on ALS data, we discuss the possibility of using other remotely sensed data as well. Taken together with the low requirements for field reference data, the presented approach provides interesting practical possibilities that are not typically proposed in the forest remote sensing literature.

Description: Fraxinus nigra Marsh. (black ash) wetland forests in northern Minnesota, USA, are threatened by the invasive insect, emerald ash borer (Agrilus planipennis Fairmaire (EAB)). A potential management option is promoting regeneration of tree species that are not EAB hosts to maintain ecosystem functions. Using an operational-scale field experiment, we examined the survival of 12 alternative tree species in response to different canopy treatments. We planted the seedlings in 1.6 ha plots assigned to four replicated canopy treatments: untreated control, group selection (0.04 ha gaps, 20% of stand), black ash girdling to emulate EAB-induced mortality, and clearcut. Fall and spring plantings were used to compare the effects of spring ponding. Control (32.9%), group selection (34.5%), and girdling (33.3%) treatments had comparable overall seedling survival. Survival in the clear-cut treatments was significantly lower (22%). Species selection, overstory treatment, and season of planting together resulted in survival rates ranging from 0.08% to 94.1%. Conifer species had low overall rates of survival (10.7%), whereas some species with native ranges not presently overlapping with northern F. nigra forests, e.g., Quercus bicolor Willd. (75.5%), had high survival rates. If growth is light-limited, group selection may be effective in promoting recruitment and supporting a larger variety of species.

Description: Natural regeneration comprises different subprocesses, each of them driven by specific climatic and stand-related factors, which determine the success of natural regeneration. The objective of this study was to investigate the seed availability of maritime pine (Pinus pinaster Aiton). To meet this objective, seed rain was monitored for four different levels of stand density at the experimental site of Cuéllar, Spain, during a 10-year period. A generalized linear mixed-effects model was fitted to test the effects of climatic variables and stand density on the annual seed production and seed rain. The climatic covariates were chosen among those that are thought to affect the key physiological phases governing these subprocesses: minimum temperature in October 2 years before dispersal (cone growing), April precipitation 1 year before dispersal (cone growing), and October–November precipitation 1 year before dispersal (cone maturation). No climate variable related to flowering or seed rain process was significant. Moreover, stand density was considered through a spatially explicit index called the seed-source index. Primary cone growth was limited by extreme cold events. Absence of precipitation limits secondary growth and hinders final cone ripening. It turns out that seed production and seed rain may be a bottleneck for natural regeneration of P. pinaster under low stand densities, especially under extreme climatic scenarios.

Description: Du, Y., Huffman, T., Daneshfar, B., Green, M., Feng, F., Liu, J., Liu, T. and Liu, H. 2015. Improving the spatial resolution and ecostratification of crop yield estimates in Canada. Can. J. Soil Sci. 95: 287–297. Canada's terrestrial ecostratification framework provides nested spatial units for organizing national data related to soils, landforms and land use. In the agricultural domain, the lack of national, uniform crop yield data on the ecostratification framework severely hinders our ability to evaluate the biophysical data with respect to economic and climatic conditions. We developed a national crop yield database at the regional (ecodistrict) level by aggregating individual records of an existing but very broad-level sample-derived yield database according to the ecostratification hierarchy. Issues related to the different sampling frameworks and the need for confidentiality of individual records were resolved in order to generate an ecostratified crop yield dataset at a reasonably detailed spatial scale. Sixty crops were first statistically arranged into 37 agronomically similar crop groups in order to increase class size, and these crop groups were aggregated into increasingly large spatial units until confidentiality was assured. The methodology maintained data quality and confidentiality while producing crop yield estimates at the ecodistrict level. Comparison to independent crop insurance data confirmed that the resulting crop yield data are valid where estimates were derived from data released at the level of an ecodistrict or an ecoregion, but not at the ecoprovince level. Our crop yield estimates offer a reasonably high level of spatial precision while remaining within standard confidentiality constraints.

Description: Rees, H. W., Chow, T. L., Xing, Z., Li, S., Monteith, J. O. and Stevens, L. 2015. Depth to compact subsoil effects on soil properties and barley–potato yields on a loamy soil in New Brunswick. Can. J. Soil Sci. 95: 203–218. An experiment was established to investigate the implications of thickness of soil over compact subsoil on plow layer soil thermal and water regimes and ultimately the yield of potato (Solanum tuberosum L.) and barley (Hordeum vulgare L.). Three depths were considered, 24 cm (shallow), 36 cm (medium) and 60 cm (deep). Results on soil temperature impacts were inconclusive. The shallow treatment water content was most greatly affected by precipitation and had the greatest potential to become saturated then drying out more than the other treatments. The deep treatment did not improve soil temperature and water regimes enough to increase crop yield. The medium depth, which most closely approximated existing local solum development, proved superior to the shallow treatment in terms of crop yield and reduced soil moisture variation, while the deep treatment did not warrant the effort required to create under field conditions. Barley and potato yields from the medium depth were greatest with 20% (significant) and 8% (not significant) more yield, respectively, than from the shallow treatment. The eroded soil profiles common to the New Brunswick potato belt exacerbate soil erosion since an eroded soil has less volume to accept water from a rainfall event, making the soil more prone to erosion, especially if it is true that our weather is changing, with the amplitude of weather shifts becoming greater. Incorporation of subsoil materials into the plow layer of eroded soils due to soil loss may result in further reduction in crop yield.

Description: Keys, K., Sterling, S. M. and Guan, Y. 2015. Using historic soil survey data to map water erosion hazard for land-use planning in Nova Scotia. Can. J. Soil Sci. 95: 299–304. A fine-scale digital soil map layer for Nova Scotia was combined with historic soil survey information and digital elevation (DEM) data to generate a new water erosion hazard map based on inherent soil erodibility and slope class. Results showed approximately 62% of Nova Scotia has low erosion hazard, 33% has moderate hazard, and 5% has high hazard. The erosion hazard map was subsequently used in a provincial watershed assessment program (NSWAP) to map potential water quality stressors related to land-use patterns on erodible soils. This work is an example of how historic soil survey data can be utilized to create new information for land-use planning and environmental assessment.