ALBERT

Beschreibung: A synthesis was carried out to examine Alaska’s boreal forest fire regime. During the 2000s, an average of 767 000 ha·year–1 burned, 50% higher than in any previous decade since the 1940s. Over the past 60 years, there was a decrease in the number of lightning-ignited fires, an increase in extreme lightning-ignited fire events, an increase in human-ignited fires, and a decrease in the number of extreme human-ignited fire events. The fraction of area burned from human-ignited fires fell from 26% for the 1950s and 1960s to 5% for the 1990s and 2000s, a result from the change in fire policy that gave the highest suppression priorities to fire events that occurred near human settlements. The amount of area burned during late-season fires increased over the past two decades. Deeper burning of surface organic layers in black spruce ( Picea mariana (Mill.) BSP) forests occurred during late-growing-season fires and on more well-drained sites. These trends all point to black spruce forests becoming increasingly vulnerable to the combined changes of key characteristics of Alaska’s fire regime, except on poorly drained sites, which are resistant to deep burning. The implications of these fire regime changes to the vulnerability and resilience of Alaska’s boreal forests and land and fire management are discussed.

Beschreibung: Genetic variation and population structure in biomass yield and coppice growth traits were assessed in seven native North American willow species (Salix amygdaloides (AMY), Salix bebbiana (BEB), Salix discolor (DIS), Salix eriocephala (ERI), Salix humilis (HUM), Salix interior (INT), and Salix nigra (NIG)) established together in common-garden field tests on two sites. Differences in biomass yield, coppice stem number, and average single-stem mass were significant at the site, species, population, and genotype (clonal) levels. There were also species × site interactions. Analyses of variance components for these traits showed that only 3%–5% of the total variation in these traits was due to site differences, whereas genetic variation at the species, population, and genotype levels accounted for approximately 10%–39%, 5%–13%, and 12%–23%, respectively. Populations were a significant source of variation in some willow species (e.g., AMY, DIS, ERI, and INT) but not in other species. Tree willows were less prolific in stem sprout production than shrub willows, and ERI coppices produced by far the highest number of stem sprouts per coppice. This multispecies investigation demonstrated strong species and clonal differences, but variation among populations within a species, although significant, was relatively small, indicating that major growth and yield gains can be made through proper species selection and clonal selection within local populations.

Beschreibung: This study investigates geographic patterns of genetic variation in aspen (Populus tremuloides Michaux.) spring phenology with the aim of understanding adaptation of populations to climatic risk environments and the practical application of guiding seed transfer. We use a classical common garden experiment to reveal genetic differences among populations from western Canada and Minnesota, and we present a novel method to seamlessly map heat-sum requirements from remotely sensed green-up dates. Both approaches reveal similar geographic patterns: we find low heat-sum requirements in northern and high-elevation aspen populations, allowing them to take full advantage of a short growing season. High heat-sum requirements were found in populations from the central boreal plains of Saskatchewan and Alberta, and populations from Minnesota exhibit moderately low heat-sum requirements for budbreak. Analysis of corresponding climate normal data shows that late budbreak is strongly associated with the driest winter and spring environments, which suggests selection pressures for late budbreak due to both frost and drought risks in early spring. We therefore caution against long-distance seed transfer of Minnesota provenances to the boreal plains of Alberta and Saskatchewan. Although such transfers have been shown to increase tree growth in short-term field tests, this planting material may be susceptible to exceptional spring droughts.

Beschreibung: There is increasing recognition that forestry provides a low cost and robust means of climate change abatement through carbon sequestration and substitution. However, current understanding of forest ecosystem carbon exchange and forest–atmosphere interactions are often inadequately characterized by existing empirical growth models with resulting poor representation for regional extrapolations. In this paper, we describe the parameterisation and independent validation, against both eddy covariance and forest growth experimental data, of a process-oriented model 3PGN to provide assessments of carbon sequestration of Sitka spruce (Picea sitchensis (Bong.) Carrière) plantations across Scotland. In comparison with eddy covariance measurements, the model predicted all of the major annual carbon fluxes, i.e., gross primary production (PG), net ecosystem production (PE), and ecosystem respiration (RE), with biases lower than 10%. At a monthly time step, only PG and PE were accurately estimated, whereas RE was not. At longer time scales (i.e., several decades), the model reliably represented the major patterns of the carbon balance. Soil type was identified as the important factor influencing site productivity; fertilization practices did not alter long-term site nutritional status. The analyses also highlighted the potential impact of carbon loss from carbon-rich soils, which can result in differences between optimal rotation length for carbon sequestration and for timber production.

Beschreibung: Understanding of the natural factors that lead to complex changes in forest ecosystems is limited. Worldwide, there are only a few forests as pristine and isolated as the Sierra de La Laguna in the southernmost range of the arid Baja California, Mexico. Its outstanding trait as a model system is that anthropogenic stressors are notably absent, which facilitates the study of natural ecological processes of the forest because separating human-induced ecological changes from natural ones is not a simple matter. In this study, we sampled sites and defined vegetation units on the basis of dominance of the canopy by the main tree species. We identified three forest types: the pine and encino forests that occupy the higher areas and the roble forest at lower elevations. For each living tree in the sampling plots, we measured height, canopy coverage per tree, diameter at breast height, as well as the amount of deadwood, leaf litter, and abundance of young trees. A succesional competition occurs between Pinus and Quercus sensu lato; we conclude that the encino forest represents a climax condition, the pine type represents an early succesional stage, and the roble forest type is a simple climax community.

Beschreibung: Forest structure, as measured by the physical arrangement of trees and their crowns, is a fundamental attribute of forest ecosystems that changes as forests progress through suc;cessional stages. We examined whether LiDAR data could be used to directly assess the successional stage of forests by determining the degree to which the LiDAR data would show the same relative ranking of structural development among sites as would traditional field measurements. We sampled 94 primary and secondary sites (19–93, 223–350, and 600 years old) from three conifer forest zones in western Washington state, USA, in the field and with small-footprint, discrete return LiDAR. Seven sets of LiDAR metrics were tested to measure canopy structure. Ordinations using the of LiDAR 95th percentile height, rumple, and canopy density metrics had the strongest correlations with ordinations using two sets of field metrics (Procrustes R = 0.72 and 0.78) and a combined set of LiDAR and field metrics (Procrustes R = 0.95). These results suggest that LiDAR can accurately characterize forest successional stage where field measurements are not available. This has important implications for enabling basic and applied studies of forest structure at stand to landscape scales.

Beschreibung: Sustainable forest management requires timely, detailed forest inventory data across large areas, which is difficult to obtain via traditional forest inventory techniques. This study evaluated k-nearest neighbor imputation models incorporating LiDAR data to predict tree-level inventory data (individual tree height, diameter at breast height, and species) across a 12 100 ha study area in northeastern Oregon, USA. The primary objective was to provide spatially explicit data to parameterize the Forest Vegetation Simulator, a tree-level forest growth model. The final imputation model utilized LiDAR-derived height measurements and topographic variables to spatially predict tree-level forest inventory data. When compared with an independent data set, the accuracy of forest inventory metrics was high; the root mean square difference of imputed basal area and stem volume estimates were 5 m2·ha–1 and 16 m3·ha–1, respectively. However, the error of imputed forest inventory metrics incorporating small trees (e.g., quadratic mean diameter, tree density) was considerably higher. Forest Vegetation Simulator growth projections based upon imputed forest inventory data follow trends similar to growth projections based upon independent inventory data. This study represents a significant improvement in our capabilities to predict detailed, tree-level forest inventory data across large areas, which could ultimately lead to more informed forest management practices and policies.

Beschreibung: Conifer winter damage results primarily from loss of cold hardiness during unseasonably warm days in late winter and early spring, and such damage may increase in frequency and severity under a warming climate. In this study, the dehardening dynamics of lodgepole pine (Pinus contorta Dougl. ex. Loud), jack pine (Pinus banksiana Lamb.), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Mill.) B.S.P.) were examined in relation to thermal accumulation during artificial dehardening in winter (December) and spring (March) using relative electrolyte leakage and visual assessment of pine needles and spruce shoots. Results indicated that all four species dehardened at a similar rate and to a similar extent, despite considerably different thermal accumulation requirements. Spring dehardening was comparatively faster, with black spruce slightly hardier than the other conifers at the late stage of spring dehardening. The difference, however, was relatively small and did not afford black spruce significant protection during seedling freezing tests prior to budbreak in late March and early May. The dehardening curves and models developed in this study may serve as a tool to predict cold hardiness by temperature and to understand the potential risks of conifer cold injury during warming–freezing events prior to budbreak.

Beschreibung: Over the last decades, continuous signs of sugar maple ( Acer saccharum Marsh.) dieback in stands of northeastern North America have promoted the experimentation of corrective measures to restore sugar maple vitality. To verify the hypothesis that K–Mg antagonism may have limited the full response of sugar maple to dolomitic lime application in a previous experiment (CaMg(CO3)2, 12% Mg), two Ca fertilizers (CaCO3 and CaSO4·2H2O), having negligible Mg content, were applied at rates of 1, 2, and 4 t Ca·ha–1 on sugar maple trees adjacent to the limed area. After 3 years, most of the foliar nutrient concentrations of treated trees were improved, particularly Ca, for both Ca fertilizers, in line with published ranges for healthy sugar maple trees, except for Mg. Moreover, no persistent nutrient antagonism was observed. The crown dieback rate of treated sugar maple was ≤5.8% after 3 years, while it reached 12% for the controls. Also, relative basal area growth showed that both Ca sources can improve growth rate. Growth response following Ca treatments was, however, lower than for the former lime experiment after the same period of time. In this context, our results suggest that Mg nutrition could be more important for sugar maple in this ecosystem than initially thought.

Beschreibung: The ability to rapidly estimate wind speed beneath a forest canopy or near the ground surface in any vegetation is critical to practical wildland fire behavior models. The common metric of this wind speed is the “mid-flame” wind speed, UMF. However, the existing approach for estimating UMF has some significant shortcomings. These include the assumptions that both the within-canopy wind speed and the canopy structure are uniform with depth (z) throughout the canopy and that the canopy roughness length (z0) and displacement height (d) are the same regardless of canopy structure and foliage density. The purpose of this study is to develop and assess a model of canopy wind and Reynolds stress that eliminates these shortcomings and thereby provide a more physically realistic method for calculating UMF. The present model can be used for canopies of arbitrary plant surface distribution and leaf area, and the single function that describes the within-canopy wind speed is shown to reproduce observed canopy wind speed profiles across a wide variety of canopies. An equally simple analytical expression for the within-canopy Reynolds stress, [Formula: see text], also provides a reasonable description of the observed vertical profiles of Reynolds stress. In turn, [Formula: see text] is used to calculate z0 and d. Tests of operational performance are also discussed.

Beschreibung: Soil compaction often limits conifer regeneration on sites degraded by landings and roads, but inadequate understanding of the relationship between compaction and tree growth could lead to inappropriate soil conservation and rehabilitation efforts. We tested liquid and plastic limits, oxidizable organic matter, total carbon, particle size distribution, and iron and aluminum oxides on soil samples collected from five forest experiments in interior British Columbia. These data were used to estimate soil maximum bulk density (MBD) and relative bulk density (RBD); our objective was to relate RBD to tree growth. Height of interior Douglas-fir ( Pseudotsuga menziesii var. glauca (Bessin) Franco) was limited when RBD was 〉0.72. For lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) and hybrid white spruce ( Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.), RBDs of 0.60–0.68 corresponded to maximum height, whereas RBDs of 0.78–0.87 appeared to limit height growth. The presence of surface organic material mitigated compaction and was often associated with lower RBD. Our results illustrate the usefulness of RBD to assess compaction and suggest that soil rehabilitation should be considered on disturbed sites where soil RBD is 〉0.80.

Beschreibung: Canada’s National Forest Carbon Monitoring Accounting and Reporting System (NFCMARS) quantifies the carbon (C) dynamics and greenhouse gas (GHG) emissions and removals of Canada’s managed forest to fulfill reporting obligations under international climate conventions. Countries are also requested to assess the uncertainty associated with these estimates, which we report here. We used Monte Carlo simulation to quantify uncertainty of carbon stock and flux estimates from the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3), the core ecosystem model of the NFCMARS. We evaluated the impacts of model algorithms, parameters, and the input data used to describe forest characteristics and disturbance rates. Under our assumptions, 95% confidence interval widths averaged 16.2 Pg C (+8.3 and –7.9 Pg C, or ±15%) for total ecosystem C stock and 32.2 Tg C·year−1 (+16.6 and –15.6 Tg C·year−1) for net biome production relative to an overall simulation median of –0.8 Tg C·year−1 from 1990 to 2014. The largest sources of uncertainty were related to factors determining biomass increment and the parameters used to model soil and dead organic matter C dynamics. Opportunities to reduce uncertainty and associated research challenges were identified.

Beschreibung: Understanding how climate affects tree growth is essential for assessing climate change impacts on forests but can be confounded by effects of competition, which strongly influences tree responses to climate. We characterized the joint influences of tree size, competition, and climate on diameter growth using hierarchical Bayesian methods applied to permanent sample plot data from the montane forests of Mount Rainier National Park, Washington State, USA, which are mostly comprised of Abies amabilis Douglas ex Forbes, Tsuga heterophylla (Raf.) Sarg., Pseudotsuga menziesii (Mirb.) Franco, and Thuja plicata Donn ex D. Don. Individual growth was sensitive to climate under low but not high competition, likely because tree ability to increase growth under more favorable climates (generally greater energy availability) was constrained by competition, with important variation among species. Thus, climate change will likely increase individual growth most in uncrowded stands with lower competition. However, crowded stands have more and (or) larger trees, conferring greater capacity for aggregate absolute growth increases. Due to these contrasting effects, our models predicted that climate change will lead to greater stand-scale growth increases in stands with medium compared with low crowding but similar increases in stands with medium and high crowding. Thus, competition will mediate the impacts of climate change on individual- and stand-scale growth in important but complex ways.

Beschreibung: Beech bark disease (BBD) has demonstrable ecosystem consequences for eastern US forests stemming from American beech (Fagus grandifolia Ehrh.) mortality, often leading to increased dominance by its competitor, sugar maple (Acer saccharum Marsh.). We hypothesized that this BBD-induced shift in tree species composition leads to changes in soil acid–base chemistry, mediated through differences in leaf litter chemistry of the two species. Using a sequence of plots representing the progression of the disease in the Catskill Mountains, NY, USA, we examined the influence of tree species composition shift on soil chemistry. The BBD impact on tree species composition was confounded by variability in substrate (or nonexchangeable soil) calcium (Ca). While substrate Ca explained much of the variation in acid–base chemistry, increasing BBD was associated with increasing forest floor exchangeable Ca, sum of base cations, base saturation, cation-exchange capacity, and decreasing hydrogen. An apparent threshold effect of substrate Ca on sugar maple litter Ca concentration suggests that underlying soil Ca availability may contribute to the spatial extent and timeframe of BBD-induced shifts in species composition. The species compositional shift is a mechanism contributing to a vegetation effect on soil acid–base status and may partially counteract soil acidification in this acid deposition impacted region.

Beschreibung: We employed simulations by forest ecosystem (SIMA) and mechanistic wind damage (HWIND) models in upland boreal forests throughout Finland to study regional risks of wind damage under changing management preferences and climates (current and RCP4.5 and RCP8.5 scenarios) over 2010–2099. We used a critical wind speed for the uprooting of trees as a measure of vulnerability, which together with the probability of such wind speed defined a level of risk. Based on that, we also predicted the stem volume of growing stock at risk and the amount of damage. In this work, medium fertility sites were planted to one of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), or silver birch (Betula pendula Roth) or to the tree species that was dominant before the final clear-felling. The vulnerability to wind damage, the volume of growing stock at risk, and the amount of damage all increased, increasing the most in the south when the proportion of Norway spruce (with shallow rooting) of the growing stock increased. Under a severe climate warming, the proportion of Norway spruce decreased the most in the south, opposite to that of birch. This decreased the risk of damage in autumn (when birch is leafless), unlike in summer. The low risk of damage in the north was due to the large proportion of Scots pine.

Beschreibung: A novel “varying-centroid” method is presented for predicting whole-tree, aboveground stem volume (i.e., bole plus branch volume) to bole volume ratios from changes in the centroid of tree bole volume associated with branching of the bole. The method was derived from a simple fractal-like tree model based on a conceptualization of tree branching architecture by Leonardo da Vinci. The method recognizes that the centroid of bole volume (the point at which one half of bole volume is above and one half is below) is always lower than the centroid of whole-tree volume and that shifts in the centroid of bole volume should be predictably related to the size of a tree’s crown. The method assumes that branch-displaced bole volume profiles can be compared with reference bole profiles that are not significantly influenced by branching, at the centroid of bole volume, and that the magnitude of bole centroid displacement predicts the branch volume necessary to cause it. When the method was applied to hardwood trees representing diverse species, sizes, and stand conditions across Michigan, the centroid of bole volume was found to vary predictably with measurable tree crown attributes and bole plus branch wood to bole wood volume ratios were generally predicted within 10% of the true value using the new method.

Beschreibung: Because of the importance of seed surface area, volume, and fill to hydraulic and thermal exchanges with the soil, mechanistic simulation of seed physiological processes associated with tree migration dynamics and the spread of invasive species require accurate equations to model seed shape. Seed dimensions have previously been described with measurements of the three principal axes, assuming an implied single ellipsoid. However, conifer seeds often exhibit anisotropy that results from bilaterally symmetric pairing on cone scales. We developed a method for measuring and modeling conifer seed shape as a sum of 2jpartial ellipsoids fused at their equators, where j = 0, …, 3. We demonstrate the use of the methods in the study of shape characteristics of ponderosa pine (Pinus ponderosa P.& C. Lawson) seeds from four families in Montana and among commercial lots of ponderosa pine, lodgepole pine (Pinus contorta Dougl. ex Loud.), and Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco). The shapes of 92%, 73%, and 47% of seeds in commercial lots studied had eight unique ellipsoids when classified with 1%, 5%, and 10% difference classification rules, respectively. Ponderosa pine seeds with longer minor axes were less well filled with storage reserves. Three-dimensional surface areas of lodgepole and ponderosa pine were approximately 2 and 3.4 times larger, respectively, than previously reported one-sided surface areas.

Beschreibung: Small-scale disturbance is a significant process in all major forest biomes. Some silvicultural practices, particularly group selection harvesting, intend to emulate natural small-scale disturbance by harvesting small clearcuts in the continuous forest. We conducted a meta-analysis on the effects of small-scale harvesting on North American breeding forest birds. We extracted species richness and relative abundance of several functional bird groups and guilds from published studies and compared them between gap-dominated and unlogged forest as a function of forest type and the size and age of the gap. The abundance of many bird groups was higher in the gap-dominated than in the continuous forest. Species preferring interior parts of the forest had the most negative association with the presence of gaps but this relationship was not statistically significant. Abundances of many bird groups increased with increasing gap size, while its effect on abundance of some bird groups disappeared quickly. Our review suggests that silvicultural practices that bring about small gaps do not negatively affect the abundances of most forest birds and often even enhance it. However, more studies are needed to examine optimal size and abundance of gaps in a forest and whether emulated small-scale disturbance effectively mimics natural processes.

Beschreibung: The ability to distinguish peatland types at the landscape scale has implications for inventory, conservation, estimation of carbon storage, fuel loading, and postfire carbon emissions, among others. This paper presents a multisensor, multiseason remote sensing approach to delineate boreal peatland types (wooded bog, open fen, shrubby fen, treed fen) using a combination of multiple dates of L-band (24 cm) synthetic aperture radar (SAR) from ALOS PALSAR, C-band (∼5.6 cm) from ERS-1 or ERS-2, and Landsat 5 TM optical remote sensing data. Imagery was first evaluated over a small test area of boreal Alberta, Canada, to determine the feasibility of using multisensor SAR and optical data to discriminate peatland types. Then object-based and (or) machine-learning classification algorithms were applied to 3.4 million ha of peatland-rich subregions of Alberta, Canada, and the 4.24 million ha region of Michigan’s Upper Peninsula where peatlands are less dominant. Accuracy assessments based on field-sampled sites show high overall map accuracies (93%–94% for Alberta and Michigan), which exceed those of previous mapping efforts.

Beschreibung: Cloud cover regulates the gross primary productivity (GPP) of forest ecosystems by changing the radiation component and other environmental factors. In this study, we used an open-path eddy covariance system and microclimate sensors installed over a poplar plantation in northern China to measure the carbon exchange and climate variables during the mid-growing seasons (June to August) in 2014 and 2015. The results indicated that the GPP of the plantation peaked when the clearness index (CI) was between 0.45 and 0.65, at which point diffuse photosynthetically active radiation (PARdif) had reached its maximum. Cloudy skies increased the maximum ecosystem photosynthetic capacity (Pmax) by 28% compared with clear skies. PARdif and soil moisture were the most and the least crucial drivers for photosynthetic productivity of the plantation under cloudy skies, respectively. The ecosystem photosynthetic potential was higher under lower vapor pressure deficit (VPD 〈 1.5 kPa), lower air temperature (Ta 〈 30 °C), and nonstressed conditions (REW 〉 0.4) for cloudy skies due to effects of Ta and VPD on stoma. Overall, our research highlighted the importance of cloud-induced radiation component change and environmental variation in quantifying the GPP of forest ecosystems.

Beschreibung: Mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins) has recently expanded its range into the lodgepole pine forests in Alberta, Canada. However, it is unknown whether semiochemical tools developed in the beetle’s historical range are suitable for monitoring MPB in the new environment. Thus, we conducted a 3-year study to test new MPB monitoring tools in Alberta. A field trial selected a combination of MPB pheromones and two host volatiles. Using this combination, we baited different numbers of trees in triangular, square, or rectangular formations (spatial arrangements of trees) to determine how the densities of baited trees affect MPB attraction. Three plots, each made up of three formations, were arranged in a linear transect at various distances between formation boundaries. The proportion of baited trees mass-attacked was highest in the square formation. However, the proportion of spillover trees mass-attacked (attacks on non-baited trees) was lower when formations were 1 km apart compared with 4 or 8 km apart. In a follow-up test of the square formation alone, there was no difference in trap tree effectiveness between distances of 8 and 12 km. We suggest that four baited trees spaced 50 m apart in a square formation at a 12 km distance can be used in the field.

Beschreibung: A system of equations for compatible prediction of total and merchantable volumes that allows for different definitions of tree volume was developed in this study. The use of the developed system will allow the conversion and subsequent comparison of results from forest inventories using different definitions of tree volume (e.g., including or not the top material of the tree and (or) the stump, inside or outside bark). The compatibility between taper, total volume, and volume ratio equations is ensured by properly integrating the taper equation. The diameter under the bark at any height is modeled with the Demaerschalk taper equation, and the corresponding diameter over the bark is obtained by assuming that bark thickness is also modeled with Demaerschalk’s function. The set of equations that has contemporaneous cross-equation error correlation (known as nonlinear seemingly unrelated regression equations) was fit using nonlinear joint generalized least squares regression. The predictive ability was evaluated using an independent data set. The system is consistent and performs well when applied to maritime pine ( Pinus pinaster Ait.) trees in Portugal, showing better performance than do other total volume equations for maritime pine used in the latest Portuguese national forest inventories.

Beschreibung: Understanding forest structural changes resulting from postdisturbance management practices such as salvage logging is critical for predicting forest recovery and developing appropriate management strategies. In 2013, a tornado and subsequent salvage operations in northern Maine, USA, created three conditions (i.e., treatments) with contrasting forest structure: blowdown, blowdown + salvage, and control (undisturbed). We sampled forest structure in five stands representing each of these three treatments. Our results document obvious and predictable changes to forest structure caused by the blowdown and salvage operations; however, they also include unexpected findings: downed coarse woody debris volume remained quite high in the salvaged areas, although its vertical distribution was markedly reduced; salvage operations did not reduce fine woody debris volume; and the salvage operation itself reduced the abundance of upturned root masses. Our study contributes to a growing body of literature highlighting the fact that outcomes of salvage operations vary considerably from situation to situation. Nevertheless, they suggest that salvage logging has important implications for residual stand structure and regeneration potential and that these implications should be considered carefully when weighing postdisturbance management options.

Beschreibung: Loblolly pine (Pinus taeda L.) is a major plantation species grown in the southern United States, producing wood having a multitude of uses including pulp and lumber production. Specific gravity (SG) is an important property used to measure the quality of wood produced, and it varies regionally and within the tree with height and radius. SG at different height levels was measured from 407 trees representing 135 plantations across the natural range of loblolly pine. A three-segment quadratic model and a semiparametric model were proposed to explain the vertical and regional variations in SG. Both models were in agreement that a stem can be divided into three segments based on the vertical variation in SG. Based on the fitted models, the mean trend in SG of trees from the southern Atlantic Coastal Plain and Gulf Coastal Plain was observed to be higher than in other physiographical regions (Upper Coastal Plain, Hilly Coastal Plain, northern Atlantic Coastal Plain, and Piedmont). Maps showing the regional variation in disk SG at a specified height were also developed. Maps indicated that the stands in the southern Atlantic Coastal Plain and Gulf Coastal Plain have the highest SG at a given height level.

Beschreibung: Subsistence harvesting and wild food production by Athabascan peoples is part of an integrated social–ecological system of interior Alaska. We describe effects of recent trends and future climate change projections on the boreal ecosystem of interior Alaska and relate changes in ecosystem services to Athabascan subsistence. We focus primarily on moose, a keystone terrestrial subsistence resource of villages in that region. Although recent climate change has affected the boreal forest, moose, and Athabascan moose harvesting, a high dependence by village households on moose persists. An historical account of 20th century socioeconomic changes demonstrates that the vulnerability of Athabascan subsistence systems to climatic change has in some respects increased while at the same time has improved aspects of village resilience. In the face of future climate and socioeconomic changes, communities have limited but potentially effective mitigation and adaptation opportunities. The extent to which residents can realize those opportunities depends on the responsiveness of formal and informal institutions to local needs. For example, increases in Alaska’s urban population coupled with climate-induced habitat shifts may increase hunting conflicts in low-moose years. This problem could be mitigated through adaptive co-management strategies that project future moose densities and redirect urban hunters to areas of lower conflict.

Beschreibung: Forest management planners usually treat potential fire loss estimates as exogenous parameters in their timber production planning processes. When they do so, they do not account for the fact that forest access road construction, timber harvesting, and silvicultural activities can alter a landscape’s vegetation or fuel composition, and they ignore the possibility that such activities may influence future fire losses. We develop an integrated fire and forest management planning methodology that accounts for and exploits such interactions. Our methodology is based on fire occurrence, suppression, and spread models, a fire protection value model that identifies crucial stands, the harvesting of which can have a significant influence on the spread of fires across the landscape, and a spatially explicit timber harvest scheduling model. We illustrate its use by applying it to a forest management unit in the boreal forest region of the province of Alberta in western Canada. We found that for our study area, integrated fire – forest management planning based on our methodology could result in an 8.1% increase in net present value when compared with traditional planning in which fire loss is treated as an exogenous factor.

Beschreibung: White poplar ( Populus alba L.) is a native species in Europe, but its growth potential is largely unknown. The general objectives of our study were to determine the impact of contrasted environments across Europe and the influence of parental characteristics on the growth potential of an intraspecific F1 white poplar family originating from a cross between parents native from the south and the north of Italy. The growth of the family was monitored at three sites located in the north of Italy, in central France, and in the southern United Kingdom. The family showed a highly superior productivity in Italy. A pronounced plasticity among sites was found for the male parent only. Indeed, for this parent, the highest growth was observed in northern Italy, its area of origin. A positive heterosis was observed mainly in France and in the United Kingdom. Broad-sense heritability values were moderate in most cases. However, the growth of the family was in some cases superior to the one of several other interspecific hybrid families growing under the same conditions, underlying the poorly known growth potential of such intraspecific hybrids for biomass production under European conditions.

Beschreibung: Declines of whitebark pine ( Pinus albicaulis Engelm.) have occurred across much of the species’ range over the last 40 years due to mountain pine beetle outbreaks and white pine blister rust infection. Management efforts to stem these declines are increasing, yet the long-term success of whitebark pine depends on the species itself adapting to the modern environment. Natural regeneration will be a critical part of this process. We examined patterns in natural whitebark pine regeneration as related to the biophysical environment in sixty 0.1 ha plots in Montana, Idaho, and Oregon. Whitebark pine regeneration was present in 97% of our plots and varied widely in density from 0 to 17 000 seedlings/ha and 0 to 2680 saplings/ha. Using nonparametric correlation analysis and ordination techniques, we found whitebark pine regeneration abundance was unrelated to stand age but significantly related to several biophysical site characteristics, including positive relationships with elevation and canopy tree mortality caused by mountain pine beetle and negative relationships with moisture availability, temperature, and subalpine fir importance. Our findings indicate that whitebark pine is regenerating in many areas and that the widespread mortality from recent mountain pine beetle outbreaks may provide suitable settings for whitebark pine regeneration given sufficient seed sources.

Beschreibung: We evaluated spruce budworm ( Choristoneura fumiferana (Clem.)) outbreak effects in nine study areas (60–86 ha each) located in the boreal forest of eastern Quebec (Canada). In each area, spruce budworm outbreak effects were measured from vegetation plots, dominant canopy and understory tree age structures, retrospective analysis of aerial photographs, defoliation records, and host tree growth reductions (dendrochronology). Large-scale synchronous outbreaks were detected across the region around the years 1880, 1915, 1950, and 1980. Overall, contrarily to what was expected for a region where host species (balsam fir ( Abies balsamea (L.) Mill.), Picea spp.) content is relatively high, these spruce budworm outbreaks seemed to have a relatively minor influence on stand dynamics, with the exception of the most recent outbreak (1980). This outbreak resulted in major stand mortality in the southern part of the region and favored the establishment of extensive tracts of young even-aged stands with few residual mature trees. This very abrupt increase in outbreak severity compared with earlier outbreaks, perhaps due to climatic or random factors, suggests that historical trends in successive outbreak severity should be extrapolated very cautiously and that the study of several outbreak cycles is needed to establish a range of natural variability that can be used to develop an ecosystem forest management strategy.

Beschreibung: Acacia koa A. Gray, an economically important timber-wood tree growing in the Hawaiian Islands, is affected by many environmental stresses, including drought, strong wind, heavy rain, and infection by fungal pathogens. Previous studies have shown that some morphological and biochemical changes that take place as a result of environmental stresses in plants can be also induced by mechanical stresses such as touching and bending. We studied morphological and biochemical changes and levels of gene transcription in A. koa plants due to mechanical stress. For a mechanical stress treatment, A. koa seedlings were gently bent in four cardinal directions daily for 2–6 months, after which morphological and biochemical changes were quantified. The stressed A. koa had significantly increased stem diameter, number of xylem cells, and anthocyanin and lignin contents and significantly reduced stem length. The gene expression analyses showed that 53 genes, including the genes for calcium signaling, ethylene biosynthesis, abscisic acid degradation, stress-related transcriptional regulation, and disease resistance, were induced more than twofold within 10–60 min following mechanical stress. The observation that the genes for disease resistance such as NBS-LRR can be induced by mechanical stress suggests that strong wind and rain in the natural forest may also induce disease resistance in trees.

Beschreibung: Forest managers are seeking strategies to create stands that can adapt to new climatic conditions and simultaneously help mitigate increases in atmospheric CO2. Adaptation strategies often focus on enhancing resilience by maximizing forest complexity in terms of species composition and size structure, while mitigation involves sustaining carbon storage and sequestration. Altered stand age is a fundamental consequence of forest management, and stand age is a powerful predictor of ecosystem structure and function in even-aged stands. However, the relationship between stand age and either complexity or carbon storage and sequestration, especially trade-offs between the two, are not well characterized. We quantified these relationships in clearcut-origin, unmanaged pine and aspen chronosequences ranging from 130 years in northern Minnesota. Complexity generally increased with age, although compositional complexity changed more over time in aspen forests and structural complexity changed more over time in pine stands. Although individual carbon pools displayed various relationships with stand age, total carbon storage increased with age, whereas carbon sequestration, inferred from changes in storage, decreased sharply with age. These results illustrate the carbon and complexity consequences of varying forest harvest rotation length to favor younger or older forests and provide insight into trade-offs between these potentially conflicting management objectives.

Beschreibung: In the last few decades, the number of people living in fire-prone ecosystems has increased, placing more people and private property at risk to future fire events. Substantial research has demonstrated consistent public support for the use of prescribed fires in fuel-reduction efforts; however, continuing public concern regarding smoke emissions and negative air quality impacts exists. To date, limited research has specifically examined public attitudes toward smoke emissions. In this study, we use a mail-back or internet survey to assess citizen information seeking behaviors regarding smoke emissions in four communities in high fire risk areas. Path analysis was used to apply the risk information seeking and processing (RISP) model to examine factors that motivate people to seek information relevant to smoke emissions. We find that residents were concerned about smoke emissions and believed that they needed more information. Residents’ intentions to seek information were influenced by information (in)sufficiency, the number of sources used, and smoke acceptability, among other factors. Findings suggest that currently available information resources on smoke may not be sufficient to meet residents’ information needs, particularly for those most motivated to learn more about emissions.

Beschreibung: Technological development has enabled the production of new value-added products from lignocellulosic residues such as lignin. This has allowed the forest industry to diversify its product portfolio and maximize the economic returns from feedstock, while simultaneously working towards sustainable alternatives to petroleum-based products. Although previous research has explored industrial-scale production opportunities, many challenges persist, including the cost of woody biomass and its supply chain reliability. While numerous studies have addressed these issues, their emphasis has traditionally been on bioenergy, with little focus on biochemical, biomaterials, and bioproducts. This review seeks to address this gap through a systematic study of the work recently reported by researchers. A lot of work has been published from United States and Canada with an emphasis on bioenergy production (84.8%), 4.6% of the work is focused on biomass to materials and chemicals, and 10.6% addressed both. Between 2012 and 2015, the majority of published research focused on biomass to materials and chemicals and both biomass to energy and biomass to materials and chemicals. This fact highlights recent interests in diversified biorefinery portfolios. However, further work concerning forest biomass supply chain optimization and new high-value bio-based materials and chemicals is necessary.

Beschreibung: In the subalpine forest ecosystems of the French Alps, European larch trees (Larix decidua Mill.) are periodically affected by outbreaks of a defoliating insect, the larch budmoth (Zeiraphera griseana (Hübner, 1799); LBM). To assess the long-term dynamics of LBM populations, we propose a spatiotemporal analysis of a long outbreak chronology reconstruction for the entire French Alps covering the period 1414–2009. This chronology was obtained by analyzing tree ring width (TRW) chronologies collected from 44 larch populations. The evidence of a latitudinal gradient in LBM is an original result that we have related to the “travelling waves” and “epicenter” theory. Wavelet analyses revealed a strong explicit continuous signal for periodicities of 4, 8, and 16 years throughout the entire 1500–2003 time series, except for a loss of power from 1690 to 1790 and since the early 1980s. We hypothesize that these abrupt changes could reflect a physiological response of LBM to past climatic variations. The spatial and temporal variability of LBM outbreaks and the propagation phenomenon in the French Alps highlighted by this study raises questions regarding its future dynamics in response to the expected climate change.

Beschreibung: We tested the response of species composition of three dominant litter-dwelling arthropod taxa (carabid beetles, spiders, and rove beetles) to wildfire and harvest. This study was conducted in north-central Ontario (47°42′N, 83°36′W) in jack pine (Pinus banksiana Lamb.) dominated stands in 2013 using pitfall trapping. Using 222 species (12 015 individuals), we compared the effects of disturbance using recently burned (3 years since fire) and clearcut sites (3 years since harvest; tree length, full tree, stump removal, and blading), as well as older, closed-canopy stands that have regenerated following clearcutting (51 years since harvest) and fire (92 years since fire), with multivariate regression trees. Taxa were more similar in the three controls (including recent fire) than between controls and harvest treatments, with increased forest floor disturbance in harvested plots being a likely explanation. In addition, taxa were different in the younger (51 years) harvest-origin plots than in the older (92 years) fire-origin plots, suggesting that communities had not yet recovered from the harvest disturbance possibly due to insufficient coarse woody debris in the younger stand. These results indicate that forest management practices that match natural forest floor disturbance could ameliorate short-term effects, whereas the maintenance of more coarse woody debris could reduce the recovery time of epigaeic communities.

Beschreibung: Intensified biomass harvesting in northern forests could potentially negatively impact soils. This study measured microbial community structure and function to assess the impacts of intensified biomass removal on soil from a managed northern jack pine (Pinus banksiana Lamb.) forest in Ontario, Canada. Four clear-cut harvesting removal intensities were compared with uncut controls and mature, fire-regenerated forest reference plots: stem-only removal, full-tree biomass removal, full-tree biomass with stump removal, and full-tree biomass with stump removal and soil blading that eliminated all aboveground and much belowground organic matter. A nearby recently burned forest site, representing common natural disturbance in the region, was also studied. Within the first two years after harvesting, there were significant differences in community structure and degradation of various C compounds among all harvested and unharvested sites, but little difference in communities across the different harvest intensities. Communities within the fire site were not comparable with those of harvested treatments, indicating that clear-cut logging may not initially produce an ecologically comparable disturbance with that of fire, although this conclusion is based on only one fire disturbance site. In the two years after harvesting, an important time for seedling establishment in managed forest systems, it appears that intensification of harvesting does not further disrupt microbial community structure and functioning beyond impacts from current harvest practices.

Beschreibung: An integrated forest management optimization model was developed to calculate potential spruce budworm ( Choristoneura fumiferana Clemens) effects on forest and wood product carbon (C) from 2007 to 2057 and to evaluate potential C sequestration benefits of alternative management strategies (salvage, biological insecticide application). The model was tested using simulated spruce budworm outbreaks on a 210 000 ha intensively managed forest in northwestern New Brunswick, Canada. Under a severe spruce budworm outbreak scenario from 2007 to 2020, harvest volume and forest and wood product C storage in 2027 were projected to be reduced by 1.34 Mm3, 1.48 Mt, and 0.26 Mt, respectively, compared with the levels under no defoliation. Under the same severe outbreak scenario, implementation of salvage and harvest replanning plus a biological insecticide applied aerially to 40% of susceptible forest area, reduced harvest, forest C, and wood product C impacts by 73%, 41%, and 56%, respectively. Extrapolation of these results to all of New Brunswick suggests that a future severe spruce budworm outbreak could effectively increase total provincial annual C emissions (all sources) by up to 40%, on average, over the next 20 years. This modeling approach can be used to identify to what extent insecticide application, as a forest-C-offset project, could result in additional C storage than without forest and pest management.

Beschreibung: Detecting forest disturbances is an important task in formulating mitigation strategies for deforestation and forest degradation in the tropics. Our study investigated the use of Landsat time series imagery combined with a trajectory-based analysis for detecting forest disturbances resulting exclusively from selective logging in Myanmar. Selective logging was the only forest disturbance and degradation indicator used in this study as a causative force, and the results showed that the overall accuracy for forest disturbance detection based on selective logging was 83.0% in the study area. The areas affected by selective logging and other factors accounted for 4.7% and 5.4%, respectively, of the study area from 2000 to 2014. The detected disturbance areas were underestimated according to error assessments; however, a significant correlation between areas of disturbance and numbers of harvested trees during the logging year was observed, indicating the utility of a trajectory-based, annual Landsat imagery time series analysis for selective logging detection in the tropics. A major constraint of this study was the lack of available data for disturbances other than selective logging. Further studies should focus on identifying other types of disturbances and their impacts on future forest conditions.

Beschreibung: Managed coniferous forest dominates much of the black-backed woodpecker’s ( Picoides arcticus Swainson) breeding range. Despite this, little is known about the fine-scale foraging behaviour of this focal species in unburned managed forest stands in the absence of insect outbreaks. To investigate the foraging substrates used in such a habitat, we employed radio-telemetry to track a total of 27 black-backed woodpeckers. During two successive summers (2005–2006), 279 foraging observations were recorded, most of which were on dying trees, snags, and downed woody debris. Individuals frequently foraged by excavation, suggesting that in the absence of insect outbreaks the black-backed woodpecker forages mainly by drilling. The majority of foraging events occurred on recently dead snags with a mean dbh (±SE) of 18.3 ± 0.4 cm. Our results suggest that in unburned boreal forest stands, substrate diameter and decay class are important predictors of suitable foraging substrates for black-backed woodpeckers. We suggest that conservation efforts aimed at maintaining this dead-wood dependent cavity nesting species within the landscape, should endeavour to maintain 100 ha patches of old-growth coniferous forest. This would ensure the continuous production of a sufficient quantity of recently dead or dying trees to meet the foraging needs of this species.

Beschreibung: Survey sampling with model-assisted estimation has recently gained popularity in forest inventory. Another option for utilizing the auxiliary information is to use poststratification, which is a special case of model-assisted estimation with class variables as explanatory variables. In this study, we compared the efficiency of poststratification with an increasing number of strata with model-assisted estimation. We carried out a study based on a simulated population. We considered four different types of poststratifications, namely (i) stratification based on predictions of a linear model, (ii) stratification based on a regression tree model, (iii) stratification based on the first principal component of the explanatory variables, and (iv) stratification based on the regression tree model with the first principal component as the only explanatory variable. Furthermore, we examined both the traditional poststratification mean and variance estimators and the difference estimator and its variance estimator for poststratification. Within the recommended range of number of strata, the model-assisted approach was more efficient than poststratification. With a large number of strata, poststratification produced smaller standard error of estimates, but problems such as empty strata were encountered with small sample sizes. Using the first principal component directly for stratification or as an explanatory variable was the most efficient approach.

Beschreibung: Structural complexity in long-lived forests where stand-replacing disturbances are rare is thought to emerge from chronic small-scale disturbances and competitive interactions between trees. We analyzed tree size distributions, tree spatial patterns, and canopy gap attributes in ten 1.42 ha stem mapped plots in old-growth Sitka spruce (Picea sitchensis (Bong.) Carrière) – western hemlock (Tsuga heterophylla (Raf.) Sarg.) forests in southeast Alaska. Most plots had rotated sigmoid or reverse-J-shaped diameter distributions. Overstory tree patterns were uniform at short distance (5 m); understory trees were spatially random or aggregated at most scales. Tree patterns were highly variable across plots. Overstory and understory tree populations were spatially independent in most medium canopy cover (40%–70%) plots but spatially repelled in most high canopy cover (〉70%) plots. Canopy gap delineation using a traditional geometric approach identified more gaps and greater forest area in gaps compared to a new method based on canopy tree shadow lengths. We recommend defining the lower limit of canopy gap size using overstory tree crown diameter; gap delineation based on overstory tree shadow length is overly conservative at higher latitude sites. Our analyses show that, despite their low species richness, the temperate rainforests of southeast Alaska are highly structurally diverse.

Beschreibung: We utilized an ecosystem model and life cycle assessment tool for studying carbon flows between the ecosystem, technosystem, and atmosphere for scenarios utilizing forest biomass (biosystem) against fossil fuel intensive materials (fossil system). The net climate impacts were studied for a Norway spruce (Picea abies (L.) Karst.) stand over two consecutive rotation periods (2 × 80 years) in the boreal conditions in central Finland (62°N, 29°E). The effects of alternative forest management on the carbon dynamics in the biosystem were studied in comparison with the fossil system by using an unmanaged and baseline thinning regime. The results showed that the biosystem produced carbon benefits compared with the similar system with the use of fossil fuel intensive materials and energy. The unmanaged stand stored the highest amount of carbon and retained carbon the longest when solely the ecosystem was considered. Studying the ecosystem and the technosystem together, the biosystem was found effective in storing and increasing the residence of carbon with or without changing the life span of biomass-based products. We found that the increase of the life span of biomass-based products could reduce emissions up to 0.28 t CO2·ha−1·year−1 depending on the management regimes over the study period. The increased stocking regimes could increase negative net climate impact by 47% over the study period compared with the use of baseline thinning in the biosystem. The proper climate mitigation strategies should consider the benefits from forest management and forest biomass in storing carbon into both the ecosystem and technosystem.

Beschreibung: New sensor-based approaches for assessing the quantity, quality, and value of timber are being developed with the goals of improving the accuracy and economics of forest measurements. One new approach is based on terrestrial laser scanning (TLS). Thirty-three plots in six radiata pine (Pinus radiata D. Don) stands were scanned using TLS. Tree locations were automatically detected. Stem profiles were measured using three methods: (i) TLS scans, (ii) Atlas Cruiser inventory procedures, and (iii) manual measurement after harvesting. Stems were optimally bucked based on log specifications and prices for Australian markets. Tree values and log product yields were estimated for the TLS data and compared with estimates based on Cruiser and actual manual measurements of stem profiles. TLS volume and value recovery were within 8% and 7%, respectively, of actual harvester recovery for five of the six stands in which it was used. Cruiser volume and value estimates were both within 4% of actual harvester recovery. Plot preparation procedures, tree characteristics, and taper equations used to model diameters on hidden stem sections affected the accuracy of automated stem detection and profile measurements for the TLS system. Improvements in data capture and analytical procedures should improve the accuracy of TLS-based volume and value estimates.

Beschreibung: Declining biodiversity is a critical component of global change owing to its influence on ecosystem functioning. Decomposition rate frequently increases with fungal species number, but the responses of extracellular enzymes to fungal species number have not been tested. To test the effect of biodiversity on decomposition and enzyme activities, quaking aspen ( Populus tremuloides Michx.) litter was inoculated with mixtures of one, two, four, or eight fungi from a pool of 16 fungi that had been isolated from a boreal forest in Alaska. Total CO2 release and the activities of β-glucosidase, which targets cellulose, and polyphenol oxidase, which targets lignin and other recalcitrant phenolic compounds, were observed across the range of species numbers in the mixtures. Total CO2 release and β-glucosidase activity increased with number of species but were only weakly correlated with each other; polyphenol oxidase activity had no correlation with number of species or CO2 release. The results indicate that, over 4 months, decomposition of labile carbon is positively correlated with number of species.

Beschreibung: In recent years, the annual imports of wooden bedroom furniture by the United States have been over five billion dollars, with more than two billion dollars of that coming from China. This trend led to an antidumping action against China in October 2003. Since January 2005, antidumping duties of 0.83% to 198.08% have been imposed on individual Chinese firms. To assess the impact of this antidumping action, intervention analysis was employed to examine the import values of four furniture commodities and the prices of two of them over 1997–2008. China and six other major competing countries were included in the analysis. With regard to import values from China, significant trade investigation effects were identified: the petition announcement generated a positive impact in March 2004; the preliminary less-than-fair-value (LTFV) determination had a negative impact from July to December 2004. However, the final implementation did not show any expected trade duty effect. The aggregate impact of the antidumping action on import values from China over 2003–2008 was approximately equivalent to a 1-month import reduction. The impact on the unit prices for China was insignificant. For the six competing countries, intervention analyses revealed that the antidumping action generated a positive trade diversion effect, with the magnitude smaller than the trade depression effect on China.

Beschreibung: The comparative analysis of a large set of long-term fertilization and thinning studies in the major forest types of interior Alaska is summarized. Results indicate that nutrient limitations may only occur during the early spring growth period, after which moisture availability is the primary control of tree growth on warm sites. The temperature dynamics of both air and soil set seasonal bounds on the nutrient and moisture dynamics for all forest types. Air and soil temperature limitations are the primary control of intraseasonal growth in the colder topographic locations in interior Alaska. These locations are usually dominated by black spruce (Picea mariana (Mill.) Britton, Sterns, Poggenb.) vegetation types. The seasonal progression of factors controlling growth is strongly tied to the state factor structure of the landscape.

Beschreibung: Restoration by imitating natural disturbances is widely practised in boreal forests to increase the availability of habitats for specialized species. We studied the abundance and species richness of saproxylic beetles on different types of created dead wood during 2 years after restoration. The study was conducted on areas of a large-scale experiment in which Norway spruce ( Picea abies (L.) Karst.) forests were restored by controlled burning and partial harvesting with down wood retention in southern Finland. More beetle species were attracted to spruces than to birches and more species were attracted to burnt trees than to unburnt trees killed by girdling. Birch-living species consistently benefited from fire, but on spruce, the abundance of cambium consumers and their associates was negatively affected by fire. Trees at harvested sites attracted more beetles in the first year, but the volume of down wood retention had only minor effects. Beetle assemblages were strongly altered by burning and harvesting. We conclude that burning and harvesting are efficient tools to promote species richness within a short time period, but there is a risk that the dead wood resource may be rapidly exhausted. Moreover, many saproxylic species of spruce forests may not be adapted to open habitats formed by stand-replacing disturbances.

Beschreibung: The current mountain pine beetle infestation in British Columbia’s lodgepole pine forests has raised concerns about potential impacts on water resources. Changes in forest structure resulting from defoliation, windthrow, and salvage harvesting may increase snow accumulation and ablation (i.e., spring runoff and flooding risk) below the forest canopy because of reduced snow interception and higher levels of radiation reaching the surface. Quantifying these effects requires a better understanding of the link between forest structure and snow processes. Light detection and ranging (lidar) is an innovative technology capable of estimating forest structure metrics in a detailed, three-dimensional approach not easily obtained from manual measurements. While a number of previous studies have shown that increased snow accumulation and ablation occur as forest cover decreases, the potential improvement of these relationships based on lidar metrics has not been quantified. We investigated the correlation between lidar-derived and ground-based traditional canopy metrics with snow accumulation and ablation indicators, demonstrating that a lidar-derived forest cover parameter was the strongest predictor of peak snow accumulation (r2 = 0.70, p 〈 0.001) and maximum snow ablation rate (r2 = 0.59, p 〈 0.01). Improving our ability to quantify changes in forest structure in extensive areas will assist in developing more robust models of watershed processes.

Beschreibung: Mast seeding is the synchronous production of large seed crops in plant populations and for many tree species is known to be determined by the interaction between weather cues and internal plant resources. We use a 24-year record of seedfall for sugar maple (Acer saccharum Marsh.) and American beech (Fagus grandifolia Ehrh.) across a northern hardwood forest landscape to quantify their masting patterns and explore the relationship between mast years, resources, and weather cues, particularly the difference between summer temperatures in the two years prior to the seedfall year (ΔT). We found clear evidence of masting in these species, and mast years were often coincident in the two species; masting was best predicted by ΔT or ΔT plus previous-year seedfall. We saw no evidence for correspondence of masting in these trees to precipitation cues. A soil calcium addition modified elevation effects on seed production. Clarification of the controls on mast seeding for these important tree species will aid in predicting such resources as mast for wildlife and maple sugar production in northern hardwood forests.

Beschreibung: We present a forest harvest scheduling model that meets timber harvest targets while maximizing a proxy measure of woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) habitat based on the configuration of preferred habitat on the landscape. Woodland caribou within the boreal forest region in Canada tend to prefer mature jack pine forest stands, which tend to be rich in their preferred resource, lichen, and also reduce predation pressure. This can create conflict with industrial wood supply needs. We designed a model that can be used to identify good harvest scheduling plans given these competing objectives. Our approach is to use a series of sequential linear programming models that are solved within a replanning framework. Specifically, each individual linear programming model seeks to produce a solution that will meet timber harvest targets while minimizing the harvest of high-quality woodland caribou habitat stands. Stands are assessed with respect to their suitability as woodland caribou habitat based on their contribution to the overall landscape equivalent connected area (ECA), a combined spatial measure of preferred habitat amount and its connectivity. We used our model for a case study of the Trout Lake Forest in northwestern Ontario, Canada, and found that our model creates approximately 10% more caribou habitat than an earlier heuristic procedure and 30% more caribou habitat than the prevailing woodland caribou habitat forest management plan in the Trout Lake Forest while meeting the same timber harvest targets.

Beschreibung: Bryophytes are dominant components of boreal forest understories and play a large role in regulating soil microclimate and nutrient cycling. Therefore, shifts in bryophyte communities have the potential to affect boreal forests’ ecosystem processes. We investigated how bryophyte communities varied in 83 forest stands in interior Alaska that ranged in age (since fire) from 8 to 163 years and had canopies dominated by deciduous broadleaf (Populus tremuloides Michx. or Betula neoalaskana Sarg.) or coniferous trees (Picea mariana Mill B.S.P.). In each stand, we measured bryophyte community composition, along with environmental variables (e.g., organic layer depth, leaf litter cover, moisture). Bryophyte communities were initially similar in deciduous vs. coniferous forests but diverged in older stands in association with changes in organic layer depth and leaf litter cover. Our data suggest two tipping points in bryophyte succession: one at the disappearance of early colonizing taxa 20 years after fire and another at 40 years after fire, which corresponds to canopy closure and differential leaf litter inputs in mature deciduous and coniferous canopies. Our results enhance understanding of the processes that shape compositional patterns and ecosystem services of bryophytes in relation to stand age, canopy composition, and changing disturbances such as fire that may trigger changes in canopy composition.

Beschreibung: Potential improvement of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) solid-wood properties was examined by estimating age trends of inheritance, age–age genetic correlations, and the efficiency of early selection using 823 increment cores sampled from 207 half-sib families at two independent progeny trials, aged 34–35 years, located in northern Sweden. High-resolution radial variation of annual ring width, wood density, microfibril angle (MFA), and modulus of elasticity (clearwood stiffness; MOES) was measured using SilviScan. The dynamic stiffness (MOEtof) of standing trees was also obtained using Hitman ST300. Heritabilities ranged from 0.10 to 0.64 for growth and earlywood, transition-wood, and latewood proportions, from 0.29 to 0.77 for density traits, and from 0.13 to 0.33 for MFA and stiffness traits. Genetic correlations between early age and the reference age (26 years) suggested that early selection is efficient at age 4 years for MFA and between ages 5 to 8 years for density and MOES. Unfavorable diameter–stiffness genetic correlations and correlated responses indicate that breeding for a 1% increase in diameter would confer 5.5% and 2.3% decreases in lodgepole pine MOES and MOEtof, respectively. Index selection with appropriate economical weights for growth and wood stiffness is highly recommended for selective breeding.

Beschreibung: Uncertainty in forest information typically results in economic and ecological losses as a consequence of suboptimal management decisions. Several techniques have been proposed to handle such uncertainties. However, these techniques are often complex and costly. Data assimilation (DA) has recently been advocated as a tool that may reduce the uncertainty, thereby improving the quality of forest planning results. It offers an opportunity to make use of all new sources of information in a systematic way and thus provides more accurate and up-to-date information to forest planning. In this study, we refer to literature on handling uncertainties in forest planning, as well as related literature from other scientific fields, to assess the potential benefits of using DA in forest planning. We identify five major potential benefits: (i) the accuracy of the information will be improved; (ii) the information will be kept up to date; (iii) the DA process will provide information with estimated accuracy; (iv) stochastic decision making can be applied whereby the accuracy of the information can be utilized in the decision making process; and (v) DA data allows for the analysis of optimal data acquisition decisions.

Beschreibung: Spatial interpolation of fire weather variables from station data allow fire danger indices to be mapped continuously across the landscape. This information is crucial to fire management agencies, particularly in areas where weather data are sparse. We compare the performance of several standard interpolation methods (inverse distance weighting, spline, and geostatistical interpolation methods) for estimating output from the Canadian Fire Weather Index (FWI) system at unmonitored locations. We find that geostatistical methods (kriging) generally outperform the other methods, particularly when elevation is used as a covariate. We also find that interpolation of the input meteorological variables and the previous day’s moisture codes to unmonitored locations followed by calculation of the FWI output variables is preferable to first calculating the FWI output variables and then interpolating, in contrast to previous studies. Alternatively, when the previous day’s moisture codes are estimated from interpolated weather, rather than directly interpolated, errors can accumulate and become large. This effect is particularly evident for the duff moisture code and drought moisture code due to their significant autocorrelation.

Beschreibung: Automated individual tree detection and delineation from high spatial resolution imagery provides good opportunities for forest inventory at a large scale. However, the accuracy of delineated crown size compared with ground measurements may not be sufficient. Thus, ordinary least squares (OLS) regression is no longer an appropriate approach to estimating and predicting variables from the delineated tree crown because both response variable and regressor are subject to measurement errors. In this study, we describe the functional and structural relationships between field-measured tree variables (i.e., tree diameter and crown width) and delineated tree crown width from remotely sensed imagery. We investigated the performance of OLS and three error-in-variable regression techniques including maximum likelihood estimator (MLE), major axis (MA) regression, and reduced major axis (RMA) regression using field-measured data and simulated data under different conditions. Our results indicated that MLE was desirable for estimating unbiased model coefficients. However, the adjustment assumption of the MLE model should be checked for predicting tree variables from remotely sensed imagery. When the assumption holds, the MLE model performed better for predicting the response variables than did the OLS model. Otherwise, the MLE model produced biased predictions for the response variables.

Beschreibung: Thinning forest stands changes biotic and abiotic conditions, subsequently altering understory communities including their photosynthetic characteristics. We investigated the effects of thinning (25% basal area decrease) in a subtropical Pinus massoniana Lamb. plantation at two post-thinning times: 0.5 years (PT0.5) and 2.5 years (PT2.5). Thinning (PT0.5 and PT2.5) significantly increased understory density (+104.9% and +142.4%, respectively), aboveground biomass (+191.1% and +239.2%, respectively), the Shannon–Wiener index, and the Pielou index and decreased the Simpson index (p 〈 0.05). Species richness significantly increased at PT0.5 and decreased at PT2.5 (p 〈 0.05). Photosynthetic characteristics of new and old leaves of three dominant species (Woodwardia japonica (Linn. f.) Sm., Dryopteris championii (Benth.) C. Chr., and Dicranopteris dichotoma (Thunb.) Bernh.) showed different variations at 0.5 and 2.5 years after thinning, depending on their various adaptive strategies. Generally, thinning improved leaf carbon fixation capacity of these dominant plants (except W. japonica old leaves). Leaf photosynthetic characteristics of these species exhibited some common changes with respect to leaf morphological attributes and chlorophyll content. Thinning increased new-leaf length (or width) and reduced old-leaf chlorophyll b concentration at PT0.5 but reduced new-leaf length, specific leaf area, and all-leaf chlorophyll concentration at PT2.5. In conclusion, thinning is a useful tool for increasing understory abundance and carbon fixation capacity of some fern species.

Beschreibung: It is widely accepted that N limits primary production in temperate forests, although colimitation by N and P has also been suggested, and on some soils, Ca and base cations are in short supply. I conducted a meta-analysis to assess the strength of existing experimental evidence for limitation of primary production by N, P, and Ca in hardwood forests of the northeastern United States and southeastern Canada using data from 35 fertilization experiments in deciduous forests on glaciated soils across the region. There is strong evidence for N limitation (formal meta-analysis weighted mean response ratio = 1.51, p 〈 0.01; simple mean = 1.42, p 〈 0.001). Forest productivity also tended to increase with additions of P (simple mean = 1.15, p = 0.05) and Ca (simple mean = 1.36, p 〈 0.001). Across all treatments, 85% of response ratios were positive. Multiple-element additions had larger effects than single elements, but factorial experiments showed little evidence of synergistic effects between nutrient additions. Production responses correlated positively with the rate of N fertilization, but this effect was reduced at high rates of ambient N deposition.

Beschreibung: The resilience and vulnerability of permafrost to climate change depends on complex interactions among topography, water, soil, vegetation, and snow, which allow permafrost to persist at mean annual air temperatures (MAATs) as high as +2 °C and degrade at MAATs as low as –20 °C. To assess these interactions, we compiled existing data and tested effects of varying conditions on mean annual surface temperatures (MASTs) and 2 m deep temperatures (MADTs) through modeling. Surface water had the largest effect, with water sediment temperatures being ~10 °C above MAAT. A 50% reduction in snow depth reduces MADT by 2 °C. Elevation changes between 200 and 800 m increases MAAT by up to 2.3 °C and snow depths by ~40%. Aspect caused only a ~1 °C difference in MAST. Covarying vegetation structure, organic matter thickness, soil moisture, and snow depth of terrestrial ecosystems, ranging from barren silt to white spruce ( Picea glauca (Moench) Voss) forest to tussock shrub, affect MASTs by ~6 °C and MADTs by ~7 °C. Groundwater at 2–7 °C greatly affects lateral and internal permafrost thawing. Analyses show that vegetation succession provides strong negative feedbacks that make permafrost resilient to even large increases in air temperatures. Surface water, which is affected by topography and ground ice, provides even stronger negative feedbacks that make permafrost vulnerable to thawing even under cold temperatures.

Beschreibung: This paper assesses the resilience of Alaska’s boreal forest system to rapid climatic change. Recent warming is associated with reduced growth of dominant tree species, plant disease and insect outbreaks, warming and thawing of permafrost, drying of lakes, increased wildfire extent, increased postfire recruitment of deciduous trees, and reduced safety of hunters traveling on river ice. These changes have modified key structural features, feedbacks, and interactions in the boreal forest, including reduced effects of upland permafrost on regional hydrology, expansion of boreal forest into tundra, and amplification of climate warming because of reduced albedo (shorter winter season) and carbon release from wildfires. Other temperature-sensitive processes for which no trends have been detected include composition of plant and microbial communities, long-term landscape-scale change in carbon stocks, stream discharge, mammalian population dynamics, and river access and subsistence opportunities for rural indigenous communities. Projections of continued warming suggest that Alaska’s boreal forest will undergo significant functional and structural changes within the next few decades that are unprecedented in the last 6000 years. The impact of these social–ecological changes will depend in part on the extent of landscape reorganization between uplands and lowlands and on policies regulating subsistence opportunities for rural communities.

Beschreibung: Multiple-use forestry requires comprehensive planning to maximize the utilization and sustainability of many forest resources whose growth and productivity are interconnected. Forest fungi represent an economically important nonwood forest resource that provides food, medicine, and recreation worldwide. A vast majority of edible and marketed forest mushrooms belong to fungi that grow symbiotically with forest trees. To respond to the need for planning tools for multiple-use forestry, we developed empirical models for predicting the production of wild mushrooms in pine forests in the South-Central Pyrenees using forest stand and site characteristics as predictors. Mushroom production and species richness data from 45 plots were used. A mixed modelling technique was used to account for between-plot and between-year variation in the mushroom production data. The most significant stand structure variable for predicting mushroom yield was stand basal area. The stand basal area associated with maximum mushroom productivity (15–20 m2·ha–1) coincides with the peak of annual basal area increment in these pine forests. Other important predictors were slope, elevation, aspect, and autumn rainfall. The models are aimed at supporting forest management decisions and forecasting mushroom yields in forest planning.

Beschreibung: Exotic Pinus taeda L. plantations may be more productive than native ones. Several hypotheses may explain this difference; however, process models with a light-interception-driving variable cannot test these hypotheses without foliage display first being quantified in native and exotic trees. We quantified leaf area duration in North Carolina, USA (natural), and Gobernador Virasoro, Argentina (exotic), with no additional nutrients and optimum fertilizer treatments. More (60%–100%) foliage was displayed but for a shorter (∼86 fewer days) time per fascicle in the exotics than in the naturals. Study inference was limited, with only one native and one exotic site. However, while the sites were markedly different in soils, climate, resource availability, and genetics, and we observed significant differences in fascicle display and longevity, most fascicles at both sites survived two growing seasons: the one in which they were produced and the subsequent one. This robust finding indicates it would be reasonable to use two growing seasons for fascicle longevity in process modeling to test hypotheses explaining growth differences in native and exotic loblolly. Fertilization had no effect on any exotic tree parameter, but it increased natural tree fascicle number (24%) and length (30%).

Beschreibung: What is the minimum age for clear-cutting native species with energetic potential in the Brazilian semi-arid region? This was the central question of this study, which aimed at estimating the minimum cutting cycle for native woody species from an area covered by a sustainable forest management plan. Individuals (n = 240) of 12 species native to the semi-arid region were measured, and wood discs were taken from them to collect data relative to (i) volume, by an industrial 3D scanner, (ii) density, using a high-frequency densitometer, (iii) age, by a growth ring measuring device, and (iv) the lower heating value, by an oxygen bomb calorimeter and an elemental analyzer. Data were fitted to mathematical models by regression analysis to determine the relationship and significance between the variables analyzed. The estimated minimum age for the harvesting of native woody species was 47 years, determined by the age at which there was stabilization of volume growth curves over time and an increase in density and heating power (wood retraction).

Beschreibung: Supply chain management problems are widespread across all economic activities. We analyze here how to address these in the case of the forest industry, which in emerging economies such as Argentina is subject to high logistic costs and faces problems of biological and economic sustainability. In this work, we analyze a management model covering from the schedule of harvesting activities and the transportation of raw materials to the final transformation at several industrial plants. Since this involves more than one objective, single-criterion mathematical programming methods are not appropriate. Here, instead, we introduce an extended goal programming formulation of the problem, able to yield good solutions in a computationally efficient way. We consider four goals: the maximization of the net present value of the production, the minimization of interannual variations in harvests, the maximization of carbon capture in the form of forest biomass, and the minimization of variations in the mean annual distance covered in transportation to the industrial plants. We apply this theoretical model to derive solutions for an actual Argentinean company. We show that the model reaches the target levels of the different goals, except for carbon balance, which is negative in all of the scenarios under evaluation.

Beschreibung: We studied the effect of water availability on basal area growth and wood properties of 11-year-old loblolly pine ( Pinus taeda L.) trees from contrasting Florida (FL) (a mix of half-sib families) and South Carolina coastal plain (SC) (a single, half-sib family) genetic material. Increasing soil water availability via irrigation increased average whole-core specific gravity (SG) and latewood percentage (LW%) by 0.036 and 6.93%, respectively. Irrigation did not affect latewood SG or wood stiffness, but irrigated FL and SC trees had more latewood due to a 29 day longer growing season. Irrigation did not affect the length of corewood production, but irrigated trees had earlier transition ages, producing outerwood ~3 years before rainfed trees. The increase in whole-core SG and LW% was moderate because irrigation promoted earlywood growth in corewood formed before canopy closure, but after year 7, rain-fed and irrigated trees had similar earlywood growth but irrigated trees had more latewood growth, increasing ring SG and LW%. The SC half-sib family had higher SG and greater LW% than trees from FL independent of irrigation due to greater yearly latewood growth. Thus, absence of soil water stress extended seasonal diameter cessation date but did not change latewood SG or wood stiffness.

Beschreibung: Wildfire risk assessment research has made considerable progress towards estimating the probability of wildfires but comparatively little progress towards estimating the expected consequences of potential fires. One challenge with estimating wildfire consequences has been to identify a common metric that can be applied to consequences measured in different units. In this paper, we use the preferences of representatives of local fire management agencies as the common consequences metric and apply it to a case study in the southern Gulf Islands, British Columbia, Canada. The method uses an expert survey and a maximum-difference conjoint analysis to establish the relative importance of specific fire consequences. A fire with a major potential for loss of life was considered to be about three times worse than major damage to houses and 4.5 times worse than loss of a rare species. Risk ratings were very sensitive to changes in fire consequences ratings. As the complexity of values at risk and number of stakeholders increase, the most efficient allocation of wildfire prevention, protection, and suppression resources becomes increasingly challenging to determine. Thus, as the complexity of stakeholder representation and values at risk increases, we need to pay increasing attention to quantitative methods for measuring wildfire consequences.

Beschreibung: In their recent review of arrested succession, Royo and Carson ( A.A. Royo and W.P. Carson. 2006. Can. J. For. Res. 36: 1345–1362 ) demonstrate that “recalcitrant understory layers” are widespread and pervasive modifiers of ecosystems and disruptors of forest regeneration. They rightly point out that many plant species associated with arrested succession are characterized by rapid vegetative spread. Extending their review, we point out that most of such species are clonal or thicket-forming and suggest that an additional reason why these plants so effectively suppress succession for extended periods is their long life-spans.

Beschreibung: This study presents a new method for considering the risk of wind damage in forest planning and for predicting the amount of damage and its effects on timber production, economic profitability and carbon balance of forestry. The effects of wind damage on the optimal management of boreal forests under current and changing climatic conditions were analyzed by comparing four forest management plans. A reference plan maximized net present value (NPV) with even-flow harvesting constraints. The second plan minimized height differences between adjacent stands, the third minimized height differences while simultaneously maximizing NPV, and the fourth maximized height differences between adjacent stands. To obtain damage-adjusted results, schedules that belonged to the optimal management plans were simulated with wind damage, taking into account the shelter provided by adjacent stands. Maximizing NPV and simultaneously minimizing height differences resulted in the highest damage-adjusted NPV. Increasing wind damage increased carbon balance of forest soil but decreased the total carbon balance of forestry as it decreased the carbon balances of living forest biomass and wood-based products. Climate change slightly improved the total carbon balance of forestry. If wind damage was ignored in calculations, NPV, total carbon balance of forestry, and timber production were overestimated.

Beschreibung: Although considerable research has focused on the influences of logging debris treatments on soil and forest regeneration responses, few studies have identified whether debris effects are mediated by associated changes in competing vegetation abundance. At sites near Matlock, Washington, and Molalla, Oregon, studies were initiated after timber harvest to quantify the effects of three logging debris treatments (dispersed, piled, or removed) on the development of competing vegetation and planted Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii ). Each debris treatment was replicated with initial and annual vegetation control treatments, resulting in high and low vegetation abundances, respectively. This experimental design enabled debris effects on regeneration to be separated into effects mediated by vegetation abundance and those independent of vegetation abundance. Two to three years after treatment, covers of Scotch broom ( Cytisus scoparius (L.) Link) at Matlock and trailing blackberry ( Rubus ursinus Cham. & Schltdl.) at Molalla were over 20% greater where debris was piled than where it was dispersed. Debris effects on vegetation abundance were associated with 30% reductions in the survival of Douglas-fir at Matlock (r2 = 0.62) and the stem diameter at Molalla (r2 = 0.39). Douglas-fir survival and growth did not differ among debris treatments when effects were evaluated independent of vegetation abundance (i.e., with annual vegetation control), suggesting negligible short-term effects of debris manipulation on soil productivity.

Beschreibung: For the prairie–forest ecotone of central North America, research of the effects of climate and fire on the annual growth of nonwoody plant types is currently needed to compliment dendrochronological research used for predicting the stability of this ecotone in the future. Using cores of Quercus stellata Wangenh. and collars of taproots of Asclepias viridis Walter from central Oklahoma, as well as cores from Quercus macrocarpa Michx. and Lespedeza capitata Michx. collars in central Minnesota, we aimed to distinguish the response towards annual precipitation and temperature, as well as fire regime, between these co-existing plant types through patterns in annual ring growth. The effect of spring fire on the annual growth increment was only consistently significant for one of the forbs, with a positive relationship. The strong negative effect of summer temperature was consistent between forbs and Q. stellata, while the positive effect of either growing season precipitation was consistent between plant types. Furthermore, we found stronger patch-specific annual ring patterns in forbs in comparison with trees when patches are separated based on unique fire histories. Overall, such efforts could be used in further studies to better predict growth rates of dominant plant types in landscapes susceptible to significant environmental change.

Beschreibung: Disturbance–succession models describe the relationship between the disturbance regime and the dominant tree species of a forest type. Such models are useful tools in ecosystem management and restoration, provided they are accurate. We tested a disturbance–succession model for the oak–pine ( Quercus spp. – Pinus spp.) forests of the Appalachian Mountains region using dendrochronological techniques. In this model, fire promotes pines, while fire suppression, bark beetle outbreaks, and ice storms encourage oaks. We analyzed nine Appalachian oak–pine stands for species establishment dates and the occurrence of fires and canopy disturbances. We found no evidence that fire preferentially promoted the establishment of pine more than oak, nor did we find any evidence that canopy disturbances or periods of no disturbance facilitated the establishment of oak more than pine. Rather, we found that both species groups originated primarily after combined canopy and fire disturbances, and reduction of fire frequency and scope coincided with the cessation of successful oak and pine regeneration. Currently, heath shrubs are slowly dominating these stands, so we present a revised disturbance–succession model for land managers struggling to manage or restore oak–pine forests containing a dense ericaceous understory.

Beschreibung: Based on individual tree damage data dating back to the gale “Lothar” (winter 1999) in Baden-Württemberg, Germany, a statistical model was developed to estimate the risk of storm damage for individual trees. The data were compiled from the National German Forest Inventory. The model attempts to separate the effects of tree-specific variables, topography, site conditions and flow field related effects on damage probability. The crucial problem of missing information on the actual flow field parameters was solved by applying a generalized additive model that enables the simultaneous fit of a spatial trend function. The geographical location of risk hotspots as predicted by the model correspond well to the actual distribution pattern of storm damage as assessed by the forest service. Tree height proved to be one of the most important factors affecting the level of damage, while height to diameter at breast height ratio influences damage probability to a much lesser extent. The Norway spruce ( Picea abies (L.) Karst.) group has the highest potential to be damaged followed by the silver fir ( Abies alba Miller) – Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) group and the Scots pine ( Pinus sylvestris L.) – larches ( Larix spp.) group. Predicted probabilities for deciduous trees are generally lower than those of conifers. West- to south-exposed locations bear a considerably higher damage risk and waterlogged soils show an increased predicted probability compared with slightly or not waterlogged soils.

Beschreibung: Fire suppression has facilitated the spread of red maple ( Acer rubrum L.), a fire-sensitive, yet highly adaptable species, in historically oak-dominated forests of the eastern United States. Here, we address whether a shift from upland oaks to red maple could influence forest hydrology and nutrient availability because of species-specific effects on precipitation distribution and inorganic nitrogen (N) cycling. In eastern Kentucky, we measured seasonal variations in red maple, chestnut oak ( Quercus montana Willd.), and scarlet oak ( Quercus coccinea Münchh.) throughfall and stemflow quantity and quality following discrete precipitation events, and we assessed net N mineralization rates in underlying soils over a 2-year period (2006–2008). Throughfall was 3%–9% lower underneath red maple than both oaks, but red maple generated 2–3× more stemflow. Consequently, NH4+ throughfall deposition was less under red maple than chestnut oak, whereas stemflow-derived nutrient inputs were substantially larger for red maple than both oaks. Soils underlying red maple had 5–13× greater winter net nitrification rates than soils under both oaks and 20%–30% greater rates of seasonal net ammonification than soils under chestnut oak. These findings suggest a spatial redistribution of water and nutrients via precipitation as red maple dominance increases and point to stemflow as an important mechanism that may foster red maple competitive success, further bolstering the mesophication process in the United States.

Beschreibung: The effects of precommercial thinning on the understory vegetative cover of 16- to 18-year-old spruce–hemlock ( Picea sitchensis (Bong.) Carrière – Tsuga heterophylla (Raf.) Sarg.) stands were studied in seven replicate areas over seven growing seasons postthinning. Vegetative cover was analyzed at the class level, but species-specific effects were examined in relation to their value as food for Sitka black-tailed deer ( Odocoileus hemionus sitkensis Cowan). When compared with unthinned controls, thinned stands (3.6–6.3 m spacing) had significantly greater understory cover. However, all thinned spacings led to similar understory cover. Conifer cover recovered to about two-thirds of its prethinning level within seven growing seasons posttreatment. Understory nonconiferous cover increased during the first 2–4 years postthinning but began to decline with increasing conifer cover during the next 3 years, nearly reaching pretreatment levels by year 7. In unthinned understories, vegetative cover had declined and was significantly lower than that beneath thinned stands. Summer food resource values for deer were increased by thinning. Winter food resource values were increased by thinning for snow-free conditions but were unaffected for conditions when herb-layer forbs were buried by snow.

Beschreibung: Ecological land classification (ELC) is central to forestry and environmental management. Few methods exist for the statistical confirmation of the distinctness and continued integrity of the ecological character of ELC regions. Consequently, forest managers lack the tools to measure the impact of ecosystem stressors such as harvest practices and climate change. We develop a framework for tracking the distinctness and modification of vegetative communities of ELC natural regions. We base the framework on principles of numerical taxonomy using the Kolmogorov–Smirnov measure of distributional difference. We demonstrate the utility of the framework using data from a 1986 Forest Development Survey of tree species abundances on 13 508 sample plots from natural regions of the New Brunswick, Canada, ELC. Using the framework, we found vegetative communities of the ELC statistically distinct in the 1986 sampling. We also investigated the impacts of plantations on forest composition using vegetation profiles from a 1999 Forest Development Survey of planted stands. Simulated planting to 20% levels suggests that past and projected planting practices will modify the vegetative character of several natural regions on a scale comparable with interregion variation. The results demonstrate the potential of the framework to track changes to a variety of biotic communities impacted by natural and anthropogenic disturbance.

Beschreibung: La coupe avec protection des petites tiges marchandes est un type de coupe partielle qui consiste généralement à récolter toutes les tiges d’un diamètre à hauteur de poitrine (dhp) supérieur à 15,0 cm, tout en conservant les tiges de plus petites dimensions. Le succès du traitement, appliqué à des forêts résineuses mûres dominées par le sapin baumier ( Abies balsamea (L.) Mill.) ou l’épinette noire ( Picea mariana (Mill.) Britton, Sterns & Poggenb.), repose en partie sur la capacité des tiges protégées à survivre. Un modèle logistique mixte a été calibré à partir de 27 blocs expérimentaux établis au Québec. Ce modèle identifie les variables qui conditionnent les probabilités de pertes des tiges individuelles protégées de 5,1 cm et plus de dhp, par mortalité sur pied ou par chablis, 5 ans après des coupes avec protection des petites tiges marchandes. Les résultats indiquent que les probabilités de pertes après traitement sont largement tributaires des caractéristiques du peuplement avant coupe (surface terrière marchande, densité de gaules, proportion de pin gris ( Pinus banksiana Lamb.)), de la qualité des opérations (procédé de récolte, taux de protection des petites tiges marchandes) et des caractéristiques des tiges protégées au moment de la coupe (inclinaison, dhp, essence). Les variables associées à l’exposition aux vents et à l’écologie des stations n’ont pas permis d’améliorer le modèle. Afin d’éviter des pertes trop élevées, il importe de bien cibler les peuplements à traiter et de réaliser un suivi rigoureux des opérations de récolte.

Beschreibung: A beech bark disease infested American beech tree ( Fagus grandifolia Ehrh.) and two uninfested trees were selected in a mature natural stand in Michigan, USA, and mated to form two full-sib families for evaluating the inheritance of resistance to beech scale ( Cryptococcus fagisuga Lind.), the insect element of beech bark disease. Four half-sib families from both infested and uninfested trees were also evaluated for resistance. Using an artificial infestation technique, adult and egg count data were collected over 2 years and analyzed with generalized linear mixed methods to account for nonnormal distributions of the response variables. A significant effect for family was found for each variable. Family least squares means were computed as a measure of resistance and repeatabilities were calculated to provide an upper limit estimate of broad-sense heritability. The two families that ranked highest for resistance were the full-sib family from two uninfested parents and the half-sib family from a stand where all diseased trees had been removed. Together, the results suggest that selection and breeding may be an effective means to improve populations for artificial regeneration, and silvicultural treatments may provide an effective management option for mitigating beech bark disease through managing the genetic composition of natural regeneration.

Beschreibung: Shrubland biomass is important for fire management programmes and for carbon estimates. Aboveground biomass and the combustible portion of biomass, the fuel load, in the past have been measured using destructive techniques. These techniques are detailed, highly labour intensive, and costly; hence, an alternative approach was sought. The new approach used linear mixed-effects models to estimate biomass and fuel loads from easily measured field variables: shrub overstorey height and cover, and understorey height and cover. Site was regarded as a random effect. Sampling sites were located throughout New Zealand and included a range of shrubland vegetation types: manuka ( Leptospermum scoparium J.R. Forst. et G. Forst.) and kanuka ( Kunzea ericoides (A. Rich.) J. Thomps.) scrub and heath, pakihi (mixed low heath, fern, and rushes), and gorse ( Ulex europaeus L.). The approach was extended and confidence intervals were constructed for the regression models. Statistical analysis showed that understorey height and overstorey cover were significant (at the 5% level) in some cases. Overstorey height was highly significant in all cases (p 〈 0.0001), allowing development of models useful to the operational user. The models allow rapid estimation of average fuel loads or biomass on new sites, and double sampling theory can be applied to calculate the error in the resultant biomass estimate.

Beschreibung: Knowledge of past forest fire regimes is important for developing management plans for conservation areas and for predicting the probable effects of forest management and climate change on the structure and dynamics of forests. In this study, fire scars on living and dead trees were systematically sampled on 256 study plots in three landscapes in northeastern Finland dominated by Scots pine ( Pinus sylvestris L.). A total of 1030 disks or partial cross sections from different trees, including scars from 98 distinct forest fires, were dendrochronologically dated with an accuracy of 1 year or better. The extraordinarily well-preserved old Pinus snags and stumps allowed us to reconstruct annual tree-ring and fire chronologies beginning from the year AD 653. The fire cycles in the studied landscapes were exceptionally long for a boreal region dominated by Pinus, on average 350 years during the last millennium. This demonstrates that the fire regimes of poorly studied remote regions cannot be extrapolated from fire regimes of sites examined in more detail. Based on statistics on lightning-ignition densities, we suggest that most of the fires detected in this study were ignited by humans. The reconstructed past fire cycles were probably shortened by human influence.

Beschreibung: This study compares different index construction methods of timberland investment returns and evaluates the resulting indices by various asset pricing models. In addition to various NCRIEF indices, I include a de-smoothed index that attempts to restore property market values, a transaction-based index that tracks ex post transaction prices, and a pure-play index that is based on unleveraged returns of public timber firms and only has exposures to the timber segment. The findings are that the appraisal-based timberland index has higher mean and lower volatility compared with the transaction-based timberland index, separate accounts outperform comingled funds in the private timberland market, the pure-play timberland index exhibits higher return and lower risk than the corresponding portfolio of public timber firms, and abnormal performance of timberland asset becomes less significant after controlling for the appraisal smoothing or by using real transaction data. These results can help timberland investors better benchmark their financial performance.

Beschreibung: The historic abundance of salmonids returning to natal streams of the inland Pacific Northwest, USA, may have constituted a major nutrient influx into these commonly oligotrophic ecosystems. Inland ecosystems tend to be warmer and dryer and more nutrient limited than coastal ecosystems; therefore, understanding how these inland conditions influence the soil biogeochemical responses to salmon carcass deposition in riparian forests is a vital step in appropriately mitigating for the loss of this nutrient subsidy. Deposition of salmon carcasses in central Idaho riparian forests resulted in a 480-fold increase in soil nitrogen (N), a sevenfold increase in dissolved organic carbon (C), and a fourfold increase in soil respired CO2, with significant biogeochemical responses persisting at one year after amendment. Despite these large increases in soil N and C, estimates of soil N and C loading only accounted for 31% and 16% of the fish carcass N and C, respectively. However, the magnitude and persistence of soil biogeochemical responses to the deposition of anadromous fish carcasses in central Idaho attests to the importance of this nutrient subsidy to inland riparian ecosystems of the Pacific Northwest.

Beschreibung: Precommercial thinning (PCT) is used to increase tree size and shorten harvest rotation time. Short-term results from PCT studies often show a trade-off between individual-tree growth and net stand yield, while longer-term effects of PCT on tree growth and stand yield are less well documented. We used a 54-year-old PCT study to test long-term effects of forest density and thinning schedules on stand yield and tree-level characteristics in even-aged western larch (Larix occidentalis Nutt.) stands. The study has three target densities (494, 890, and 1680 trees·ha−1) crossed with three thinning schedules (target density achieved through one, two, or four entries). Analysis of variance (ANOVA) and linear contrasts were used to test the effects of density and number of entries on tree- and stand-level attributes. Thinning before stand age 10 years leads to long-term constant yield (219.0–269.5 m3·ha−1; P 〉 0.05) across the tested densities. We also found constant volume growth across stand densities during the most recent measurement interval (5.42–6.41 m3·ha−1·year−1; P 〉 0.05). Number of entries did not affect any tree- or stand-level attribute. The primary effect of early PCT is to control whether wood volume and growth are concentrated on few large, stable trees or spread over many small, unstable trees.

Beschreibung: Oaks (Quercus spp.) are becoming increasingly important for future forest management as the climate in central Europe warms. Owing to the high costs of conventional row planting, artificial oak stand establishment in the form of “clusters” became popular in central Europe beginning in the 1970s. In cluster plantings, oaks are planted either in groups of ca. 20–25 at 1 m spacing between trees (i.e., group planting) or in denser groups with 20–30 oaks·m−2 (i.e., nest planting). In both cases, the clusters are spaced apart at a distance that represents the target density of future crop trees. A comprehensive review of the history, growth, tree quality development, and economic aspects of oak cluster plantings suggests that initial growing space was the most important factor influencing development of oaks in clusters. Consequently, survival, growth, quality, and biomass production were comparable in group and row plantings but lower in nest plantings. In addition, group plantings resulted in greater stand-level tree species diversity than nest or row plantings. We conclude that oak group planting is a comparatively inexpensive option for the artificial regeneration of oak-dominated broadleaved forests for a range of situations such as reforestation of disturbed areas or the afforestation of abandoned agricultural land. Future research needs regarding development and tending of forests established by oak group planting are highlighted.

Beschreibung: To understand the contemporary and anticipated future (future 30–50 years) distribution of Chinese wild yellowhorn (Xanthoceras sorbifolium Bunge) and to improve the species’ in situ conservation strategy within the network of China’s National Nature Reserves (NNR), we used BiodiversityR to predict the species’ distribution utilizing the “always-suitable” map concept. We then delineated the always-suitable distributions with the existing NNRs to identify potential conservation areas using an approach that concurrently considered spatial distribution, gap analysis, the role of climate change, and economic analyses. Seven bioclimatic variable predictors and 12 environmental niche modelling submodels successfully contributed to the final model assembly (AUC = 0.916, κ = 0.398). The species range delineation indicated that 71 of the 427 NNRs were included in the always-suitable area, accounting for 26 007 km2 (1.58%) of the species total distribution. This mapping endeavour highlighted the negative impact of climate change with a projected 15%–20% habitat decline and expected species’ distribution centers shifting from the country’s northwest to the southeast. Our results predict the continuous deterioration of X. sorbifolium because of its existing utilization as an oil source and its increased bioenergy potential. The adoption of a flexible management strategy embracing acceptable trade-offs between conservation and utilization within China’s NNRs could effectively alleviate the expected species decline.

Beschreibung: Anthropogenic influences have altered most fire regimes. Fire management programs often try to mimic natural fire regimes to maintain fuels and sustain native fire-dependent species. Lightning is the natural ignition source in Florida, substantiating the need for understanding lightning fire incidence. Sixteen years of lightning data (1986–2003, excluding 1987 and 2002 due to missing data) from the NASA Cloud to Ground Lightning Surveillance System and fire ignition records were used to quantify the relationship between lightning incidence and ignitions on Kennedy Space Center, Merritt Island National Wildlife Refuge, and Cape Canaveral Air Force Station. There were 230 lightning fires with an average of 14 ignitions per year, primarily in July, and only one winter ignition. Precipitation influenced the efficiency of lightning ignitions, particularly July precipitation. We found that negative polarity strikes caused the majority of ignitions. Pine flatwoods was ignited more frequently than expected given equal chance of ignition among landcover types. About half (51%) of detected fires were instantaneous ignitions and the other 49% were delayed an average of 2 days. This information is useful for paramaterizing fire regime models and for mimicking the natural fire regime through fire prescriptions on these properties and throughout the southeastern United States. These methods may be useful in fire-maintained systems globally.

Beschreibung: The invasive emerald ash borer (EAB) (Agrilus planipennis Fairmaire (Coleoptera: Buprestidae)) is a significant threat to biodiversity and ecosystem processes in North American forests. Of particular concern is the fate of Fraxinus nigra (black ash), which is frequently a dominant canopy species across much of its range. To investigate the potential vegetation response to the loss of this foundation species, EAB-induced mortality was simulated in F. nigra dominated wetlands of Upper Michigan, USA. No growth response of residual overstory species occurred over the course of three growing seasons, which may in part be attributed to negative effects of post-treatment growing conditions, including prolonged inundation. A significant increase in non-Fraxinus sapling growth rate was observed, however. Mortality of F. nigra did not impact overall stem recruitment or regeneration, although species composition is shifting towards Acer rubrum (red maple) and Betula alleghaniensis (yellow birch) in the seedling layer. The herbaceous community exhibited the greatest response, nearly doubling in areal cover by the end of the study. Importantly, this expanded cover was not associated with decreased establishment of new woody seedlings, suggesting that increased competition between these functional groups has not yet impacted the potential for future recovery of woody vegetation in these forests.

Beschreibung: In trees, the change from juvenile to adult vegetative phase can last for years. In Populus tremula L., this phase change is characterized by a morphological change in leaf shape, as leaves in the seedling phase typically are sharp-tipped, while saplings and trees have round-tipped leaves. In an open-field experiment, we studied the separate and combined effects of enhanced temperature and UVB radiation on 2-year-old P. tremula plantlets undergoing phase change. The concentration of salicylates was higher in the seedling-phase plants than in tree-type plants. In contrast, the concentration of condensed tannins was higher in the tree-type plants but only under ambient temperature. Enhanced temperature increased growth of the plants and the concentration of some salicylate compounds, and it decreased concentrations of flavonoids, phenolic acids, and condensed tannins. In addition, in the seedling-phase plants, the severity of rust infections decreased and herbivore damage increased under warming. The effects of enhanced UVB radiation were weaker, as concentrations of only two flavonoid compounds increased under enhanced UVB radiation. Based on our results, climate change may have a moderate delaying effect on the physiological development of both sexes of P. tremula, which may lead to lowered performance in their normal habitat in the future.