Boreal Forest Species Research Articles

Moose\u2013tree interactions: rebrowsing is common across tree species

BackgroundPlant strategies to resist herbivory include tolerance and avoidance. Tolerance strategies, such as rapid regrowth which increases the palatability of new shoots, can lead to positive feedback loops between plants and herbivores. An example of such a positive feedback occurs when moose (Alces alces) browse trees in boreal forests. We described the degree of change in tree morphology that accumulated over time in response to repeated browsing by moose, using an index of accumulated browsing. We evaluated whether accumulated browsing could predict the probability and extent of current browsing across woody species in a Norwegian boreal forest, and how our accumulated browsing index related to changes in tree height, shoot availability and shoot size.ResultsThe probability and extent of current browsing increased with the degree of accumulated browsing in all tree species. Plants highly modified by previous browsing were the most attractive, with no indication of decreased preference with repeated browsing over time. The preference for previously browsed trees is most likely driven by increased relative availability of shoots within browsing height and maybe increased palatability. This response to previous browsing was general for both preferred and avoided forage species, in both conifers and deciduous trees.ConclusionsOur results suggest that the adaptation for rapid regrowth after browsing does not reduce herbivory on trees. Rather, our results indicate that plant responses to browsing increase the probability of future herbivory. This response could potentially lead to higher plant mortality where cervid populations are maintained at stable high densities and has implications for plant population dynamics and forestry practices.

Environmental conditions regulate the impact of plants on cloud formation

The terrestrial vegetation emits large amounts of volatile organic compounds (VOC) into the atmosphere, which on oxidation produce secondary organic aerosol (SOA). By acting as cloud condensation nuclei (CCN), SOA influences cloud formation and climate. In a warming climate, changes in environmental factors can cause stresses to plants, inducing changes of the emitted VOC. These can modify particle size and composition. Here we report how induced emissions eventually affect CCN activity of SOA, a key parameter in cloud formation. For boreal forest tree species, insect infestation by aphids causes additional VOC emissions which modifies SOA composition thus hygroscopicity and CCN activity. Moderate heat increases the total amount of constitutive VOC, which has a minor effect on hygroscopicity, but affects CCN activity by increasing the particles’ size. The coupling of plant stresses, VOC composition and CCN activity points to an important impact of induced plant emissions on cloud formation and climate.

Impact of high daytime air humidity on nutrient uptake and night-time water flux in silver birch, a boreal forest tree species

At northern latitudes, a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We investigated the impact of high (H) and moderate (M) daytime air relative humidity (RH) on water relation parameters and foliar nutrient status in saplings of silver birch, to elucidate the interactions between water and nutrient uptake. A ~40% lower daytime vapour pressure difference between the leaf interior and atmosphere caused significantly (P 0.05) between the treatments. Our results suggest that the 32.3% higher total foliar P in the H treatment could be partly induced by 28.2% greater transpiration-driven mass flow of water-soluble P and/or by 25.4% higher number of absorptive root tips. Our results confirm that elevated daytime atmospheric humidity increases the potential for night-time water flux and might also facilitate the uptake of mineral nutrients in silver birch, a dominating deciduous tree species in boreal forests.

Lecidea coriaceasp. nov., a Lichen Species from Oldgrowth Boreal and Montane Forests in Europe and North America

Holien, H., Palice, Z., Björk, C. R., Goward, T. & Spribille, T. 2016. Lecidea coriacea sp. nov., a lichen species from oldgrowth boreal and montane forests in Europe and North America. — Herzogia 29: 412–420.Lecidea coriacea is described as new to science from the boreal forests of Europe and montane conifer forests of northwestern North America. It is probably related to some of the species currently assigned to the genus Puttea, but is included in Lecidea awaiting a more thorough revision of this group. The species is characterized by pale to dark brown apothecia, plusiosporic asci and by the production of secalonic acid A in the hypothecium causing a golden yellow reaction with KOH. Lecidea coriacea seems to be a species of oldgrowth forests and is threatened by forestry. It often grows on old trees of Betula, Picea and Salix or on old conifer snags. Notes on similar species and other plusiosporic epiphytic and lignicolous species in boreal forests are given.

Food supplementation and predation risk in harsh climate: interactive effects on abundance and body condition of tit species

Food availability and predation risk can have drastic impacts on animal behaviour and populations. The tradeoff between foraging and predator avoidance is crucial for animal survival and will strongly affect individual body mass, since large fat reserves are beneficial to reduce starvation but may increase predation risk. However, two-factor experiments simultaneously investigating the interactive effects of food and predation risk, are still rare. We studied the effects of food supplementation and natural predation risk imposed by pygmy owls Glaucidium passerinum on the abundance and fat reserves of tit species in boreal forests of north Europe, from January to March in 2012 and in 2013. Food supplementation increased the number of individuals present in a given forest patch, whereas the level of predation risk had no clear impact on the abundance of tit species. The stronger impact of food supply respect to predation risk could be the consequence of the harsh winter conditions in north Europe, with constant below-zero temperatures and only few (5-7 h) daylight hours available for foraging. Predation risk did not have obvious effects on tit abundance but influenced food consumption and, together with food supplementation, affected the deposition of subcutaneous fat in great tits Parus major. High owl predation risk had detrimental effects on body fat reserves, which may reduce over-winter survival, but the costs imposed by pygmy owl risk were compensated when food was supplemented. The starvation–predation tradeoff faced by great tits in winter may thus be mediated through variation in body fat reserves. In small species living in harsh environment, this tradeoff appeared thus to be biased towards avoidance of starvation, at the cost of increasing predation risk. This article is protected by copyright. All rights reserved.

Wood ant colouration as an ecological indicator for the level of disturbance in managed coniferous forests

The search for ecological indicators of population well-being in natural and managed ecosystems is a crucial aspect of effective biomonitoring, conservation and nature protection. In long-term monitoring programs environmental stress has a measurable effect on naturally selected traits, such as body shape or size. However, changes in colouration provide information about early warning responses. The red wood ant Formica aquilonia is ecologically and territorially dominant among wood ant species in European boreal coniferous forest, and possesses variable red-brownish melanin-based cuticular colouration. F. aquilonia gynes, which are unfertilized queens, exhibit colour variability on the head, propodeum and abdomen, yet only head colour features allow setting clearly visible and symmetrical (left/right) classes of morphs. We studied phenotypic colour variability, melanisation and fluctuating asymmetry of colour patterns in faces of F. aquilonia gynes from natural (forest interiors) and disturbed (clear-cut zones and forest edges) habitats in Finland. We defined five variable, clearly visible and symmetrical (left/right) colour morphs of gynes' faces. Individuals of totally dark morph were present only in disturbed habitats. General analyses of melanisation degree showed, that gynes from disturbed habitats were significantly darker compared to those from forest interiors. Individuals from the same nest tend to have a similar degree of melanisation. The mean darkness of face was highest among individuals from forest-edge nests and the lowest from forest interior nests. In all habitat types the darkness of face increased with an increase in head width. Increase of cuticular melanisation in F. aquilonia gynes in disturbed habitats could be explained with the theory of thermal melanism and stress-induced immune defence. Although some amount of fluctuating asymmetry among left/right symmetrical colour variations on faces of F. aquilonia gynes was found, it was affected neither by habitat type nor by head width. Melanisation degree of red wood ants have a potency to be used as ecological indicator for the level of disturbance in managed coniferous forests and fluctuating asymmetry of colour variations in ants might be studied furtherly in cases of more severe environmental concerns.

Influence of Field-Based Species Composition and Understory Descriptions on Spectral Mixture Analysis of Tree Species in the Northwest Territories, Canada

Tree species information is a fundamental component of forest inventories that is challenging to obtain in northern boreal forests because inherently open stands with individual trees might be clumped or widely distributed and contain multiple tree species. These challenges result in a mixed pixel problem that was investigated using Multiple Endmember Spectral Mixture Analysis (MESMA), a technique for identifying the type and proportions of forest components (e.g., sunlit canopy, background vegetation, shadow) in remotely sensed imagery at the subpixel scale. This was tested using Landsat Thematic Mapper (TM) imagery from a study area in the Northwest Territories (NWT), Canada. How the dominant tree species was described in the field, and how the spectral properties of understory vegetation was measured, were both important factors that affected species discrimination. Landsat TM was most sensitive to dominant species defined by the fraction of total basal area of the dominant and codominant trees. Classification accuracies of 90% and 63% for very open and medium density forest stands, respectively, were achieved when understory diversity and abundance information was incorporated into the definition of the background component. It was concluded that this approach warrants further investigation for northern boreal forest species classification.

Tree species traits are the predominant control on the decomposition rate of tree log bark in a mesic old-growth boreal forest

Decomposition of coarse woody debris (CWD) bark is characterized by complex and poorly understood dynamics with unclear implications for carbon and nutrient cycling and biodiversity. We examined changes in cover and physical parameters through decomposition of bark attached to logs of the main tree species in an old-growth middle boreal forest. In a 66yrs long chronosequence after tree death and fall, we analyzed changes in the following parameters of log bark: cover, moisture, area-specific mass, total mass, dry bulk density, thickness and proportion of phloem. The percent of bark left on the sampled stems decreased with time since tree death and averaged 38%, 61% and 86% for Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and silver and downy birch (Betula pubescens and Betula pendula)=aspen (Populus tremula), respectively. Bark moisture increased along with succession of epixylic vegetation on logs that progressed similarly for all studied tree species. On average, no vegetation was recorded on logs 3yrs after tree death. In 9yrs, logs were characterized by the first stage of sparse vegetation cover. The closed groups of the second stage, with cover of not less than 70%, consisted mainly of non-epigeous species, and developed an average of 19yrs after tree death. The third stage was dominated by ground cryptogam species without a significant contribution of vascular plants, and the fourth stage, when the wood was completely overgrown by the establishment and spread of vascular plants, was observed and average of 30yrs after tree death. The exponential rate of total mass loss of bark increased at rates of 0.068, 0.110, 0.197 and 0.312yr−1 for birch, aspen, spruce, and pine, respectively. The highest rate of bulk density loss was recorded for aspen (0.024yr−1) and did not differ for birch, pine and spruce (0.009yr−1). The decomposition rate was expressed as a rate of bark mass loss divided by initial volume (integrating losses due to bark mineralization, peeling, consumption by insects and sloughing from logs). It averaged 0.147yr−1 for birch, aspen and spruce and 0.291yr−1 for pine, independent of stem section, log diameter and decay class. In old-growth forests, where CWD volumes may reach hundreds of cubic meters, the accurate portrayal of bark decomposition patterns is crucial for estimating the role of CWD in carbon and nutrient cycles and the diversity of CWD-dependent organisms with different habitat requirements.

Responses and influencing factors of foliar photosynthetic characteristics of <italic>Larix gmelinii </italic>to changing environments

Investigating tree photosynthetic capacity is important for understanding the carbon cycles of terrestrial ecosystems and their responses and adaptation to climatic change. Dahurian Larch ( Larix gmelinii ) is one of the dominant tree species in Chinese boreal forests with a broad bio-geographic range under divergent habitats, and thus an ideal tree species for exploring tree adaptation to environment. In this study, we measured the foliar photosynthesis and associated physiological parameters of 30-year-old Dahurian larch trees from six provenances in a common garden at the Maoershan Forest Ecosystem Research Station in Northeast China for three years (2009–2011). The six provenances were located across the natural distribution range of the larch, spanning approximately 4° in latitude (48°–52°N), 5°C in mean annual temperature ( - 2.3–2.6°C), and 200 mm in mean annual precipitation (425–622 mm). To access the top canopy of the sampled trees, we constructed 15-m-high wooden scaffolds at the site. Three representative trees from each provenance were selected for the measurements per month from mid May to mid September. We measured three fully expanded sunlit fascicles on young short shoots at the top of the canopy of each tree in situ with an infrared gas analyzer. On non-rainy days, light and CO2 response curves were measured between 06:30 and 12:00 hours under optimal conditions. Our goal was to explore impacts of environmental changes on foliar photosynthetic characteristics of the larch and their driving factors. The main results were summarized as follows: (ⅰ) The leaf-area-based maximum net photosynthetic rate ( P max-a), dark respiratory rate ( R a), apparent quantum yield (AQY), maximum rate of carboxylation ( V max), maximum electron transport rate ( J max) and triose phosphate utilization rate (TPU) all increased significantly ( P T s) and aridity index (AI) of the seed-source original sites, while the light compensation point (LCP) and photorespiratory rate ( R p) showed an opposite trend. This suggests that the leaf photosynthetic characteristics genetically adapt to the original site conditions of the tree seed-sources, among which the temperature and precipitation are the major driving factors. (ⅱ) P max-a was positively correlated with AQY, V max, J max, TPU, and leaf nitrogen concentration, but negatively with LCP and R p ( P T s habitats had higher sensitivity of P max-a associated with other characteristics. (ⅲ) P max-a was significantly and positively correlated with 3-day mean temperature, mean monthly temperature, mean growing season temperature, 3-day mean relative humidity, and mean monthly precipitation of the common garden, while the R a showed opposite trends with the environmental factors except for the mean growing season temperature. This indicates that the leaf photosynthetic characteristics acclimate to the environmental conditions of the common garden. However, the trees from higher T s habitats had lower intercepts of the regression equations of P max-a associated with the environmental factors, and had the opposite trends for R a except for the mean growing season temperature. The results suggest that the relationships between foliar photosynthetic characteristics and environment are jointly controlled by both phenotypic acclimation to current site conditions and genotypic adaptation to the original environment of the seed-source. These findings provide insights on understanding the survival, reproduction and distribution of Dahurian larch to changing environments.

Spatial ecology and resource selection of a high-elevation American marten (Martes americana) population in the northeastern United States

High-elevation forests that contain mature, closed canopy stands are considered important habitat for American martens (Martes americana (Turton, 1806)) in the northeastern United States. To investigate this hypothesis, we monitored 15 radio-collared martens over a 2-year period and measured spatial use, as well as second- and third-order resource selection, from 33 seasonal home ranges and 889 telemetry locations. The population was composed primarily of adults that had small home-range size with average seasonal fidelity. During leaf-off seasons, martens selected against regenerating forest at both scales and selected for mixedwood and softwood forests and areas with rugged terrain within home ranges. Second-order selection was less pronounced during leaf-on seasons, yet martens exhibited greater selection for hardwood forest and areas with rugged terrain within home ranges. Home-range size was correlated positively with the amount of regenerating forest and body-condition index scores were lower during winter, indicating that these spatial and temporal attributes were influential. Although martens utilized low-elevation forest with extensive timber harvesting, contiguous, mature, and rugged high-elevation forest was used preferentially during winter. Land managers should minimize disturbance of montane ecosystems to ensure population viability for martens and other boreal forest species along distributional edges.

Characterizing Zinc Speciation in Soils from a Smelter-Affected Boreal Forest Ecosystem.

HudBay Minerals, Inc., has mined and/or processed Zn and Cu ore in Flin Flon, MB, Canada, since the 1930s. The boreal forest ecosystem and soil surrounding these facilities have been severely impacted by mixed metal contamination and HSO deposition. Zinc is one of the most prevalent smelter-derived contaminants and has been identified as a key factor that may be limiting revegetation. Metal toxicity is related to both total concentrations and speciation; therefore, X-ray absorption spectroscopy and X-ray fluorescence mapping were used to characterize Zn speciation in soils throughout the most heavily contaminated areas of the landscape. Zinc speciation was linked to two distinct soil types. Group I soils consist of exposed soils in weathered positions of bedrock outcrops with Zn present primarily as franklinite, a (ZnFeO) spinel mineral. Group II soils are stabilized by an invasive metal-tolerant grass species, with Zn found as a mixture of octahedral (Fe oxides) and tetrahedral Mn oxides) adsorption complexes with a franklinite component. Soil erosion influences Zn speciation through the redistribution of Zn and soil particulates from Group I landscape positions to Group II soils. Despite Group II soils having the highest concentrations of CaCl-extractable Zn, they support metal-tolerant plant growth. The metal-tolerant plants are probably preferentially colonizing these areas due to better soil and nutrient conditions as a result of soil deposition from upslope Group I areas. Zinc concentration and speciation appears to not influence the colonization by metal-tolerant grasses, but the overall soil properties and erosion effects prevent the revegetation by native boreal forest species.

Exploring Factors Influencing Species Natural Regeneration Response Following Harvesting in the Acadian Forests of New Brunswick

In the Acadian Forest Region of northeastern North America, forest managers are under increasing public pressure to restore the forest to a more historic, natural condition by reducing in clearcutting and promoting partial-cut treatments that more closely emulate historic, local natural disturbance regimes. However, although numerous studies on the effects of partial-cutting on forest regeneration response have been conducted in surrounding temperate and boreal forest ecosystems, there are few studies that directly explore responses to various forms of harvesting within the Acadian Forest ecosystem, with its unique mixture of northern hardwoods and boreal forest species. Here, we conducted one of the first retrospective studies on forest regeneration following a variety of harvesting methods in the Acadian Forest using univariate and multivariate regression trees to assess regeneration response in 50 naturally-regenerating, harvested forest sites in New Brunswick, Canada. Our study shows that regeneration was highly influenced by harvest type, overstory composition, and environmental conditions as reflected by ecoregion classification. Canopy opening size (as controlled by harvest method) significantly influenced the dominance of regenerating species. The presence of conspecific overstory trees increased the likelihood of their regeneration following disturbance, supporting the direct-regeneration hypothesis, especially for species with limited seed dispersal (e.g., sugar maple (Acer saccharum Marsh.) and American beech (Fagus grandifolia Ehrh.). Despite reported problems elsewhere in eastern North America, neither American beech nor balsam fir (Abies balsamea (L.) Mill.) constituted significant competition for the desired species on a broad scale, but the presence of beech was a significant deterrent for yellow birch (Betula alleghaniensis Britt.).

Tree Species Establishment in Urban Forest in Relation to Vegetation Composition, Tree Canopy Gap Area and Soil Factors

The study of density and growth of pine, birch and oak seedlings and saplings in canopy gaps in the urban boreal forest in Riga, Latvia, indicates that natural regeneration can increase diversity in small gaps caused by tree mortality, and can ensure conversion from even-aged pine forest. Abundant regeneration in small gaps showed that light (gap area) was only one of the factors affecting tree regeneration in the gaps. The depth of the O layer and pH were suggested to be important factors for the establishment and growth of pine and birch. For oak, the main factors for establishment and growth were favorable moisture, higher pH and N concentration. Knowledge of ecological factors affecting the establishment of seedlings and growth of saplings of the most common trees species in the urban boreal forest is needed to predict successional trajectories and to aid management.

Changes in hormone flux and signaling in white spruce (Picea glauca) seeds during the transition from dormancy to germination in response to temperature cues.

BackgroundSeeds use environmental cues such as temperature to coordinate the timing of their germination, allowing plants to synchronize their life history with the seasons. Winter chilling is of central importance to alleviate seed dormancy, but very little is known of how chilling responses are regulated in conifer seeds. White spruce (Picea glauca) is an important conifer species of boreal forests in the North American taiga. The recent sequencing and assembly of the white spruce genome allows for comparative gene expression studies toward elucidating the molecular mechanisms governing dormancy alleviation by moist chilling. Here we focused on hormone metabolite profiling and analyses of genes encoding components of hormone signal transduction pathways, to elucidate changes during dormancy alleviation and to help address how germination cues such as temperature and light trigger radicle emergence.ResultsABA, GA, and auxin underwent considerable changes as seeds underwent moist chilling and during subsequent germination; likewise, transcripts encoding hormone-signaling components (e.g. ABI3, ARF4 and Aux/IAA) were differentially regulated during these critical stages. During moist chilling, active IAA was maintained at constant levels, but IAA conjugates (IAA-Asp and IAA-Glu) were substantially accumulated. ABA concentrations decreased during germination of previously moist-chilled seeds, while the precursor of bioactive GA1 (GA53) accumulated. We contend that seed dormancy and germination may be partly mediated through the changing hormone concentrations and a modulation of interactions between central auxin-signaling pathway components (TIR1/AFB, Aux/IAA and ARF4). In response to germination cues, namely exposure to light and to increased temperature: the transfer of seeds from moist-chilling to 30 °C, significant changes in gene transcripts and protein expression occurred during the first six hours, substantiating a very swift reaction to germination-promoting conditions after seeds had received sufficient exposure to the chilling stimulus.ConclusionsThe dormancy to germination transition in white spruce seeds was correlated with changes in auxin conjugation, auxin signaling components, and potential interactions between auxin-ABA signaling cascades (e.g. the transcription factor ARF4 and ABI3). Auxin flux adds a new dimension to the ABA:GA balance mechanism that underlies both dormancy alleviation by chilling, and subsequent radicle emergence to complete germination by warm temperature and light stimuli.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0638-7) contains supplementary material, which is available to authorized users.

Negative impacts of high temperatures on growth of black spruce forests intensify with the anticipated climate warming.

An increasing number of studies conclude that water limitations and heat stress may hinder the capacity of black spruce (Picea mariana (Mill.) B.S.P.) trees, a dominant species of Canada's boreal forests, to grow and assimilate atmospheric carbon. However, there is currently no scientific consensus on the future of these forests over the next century in the context of widespread climate warming. The large spatial extent of black spruce forests across the Canadian boreal forest and associated variability in climate, demography, and site conditions pose challenges for projecting future climate change responses. Here we provide an evaluation of the impacts of climate warming and drying, as well as increasing [CO2 ], on the aboveground productivity of black spruce forests across Canada south of 60°N for the period 1971 to 2100. We use a new extensive network of tree-ring data obtained from Canada's National Forest Inventory, spatially explicit simulations of net primary productivity (NPP) and its drivers, and multivariate statistical modeling. We found that soil water availability is a significant driver of black spruce interannual variability in productivity across broad areas of the western to eastern Canadian boreal forest. Interannual variability in productivity was also found to be driven by autotrophic respiration in the warmest regions. In most regions, the impacts of soil water availability and respiration on interannual variability in productivity occurred during the phase of carbohydrate accumulation the year preceding tree-ring formation. Results from projections suggest an increase in the importance of soil water availability and respiration as limiting factors on NPP over the next century due to warming, but this response may vary to the extent that other factors such as carbon dioxide fertilization, and respiration acclimation to high temperature, contribute to dampening these limitations.

Genotypic Tannin Levels in Populus tremula Impact the Way Nitrogen Enrichment Affects Growth and Allocation Responses for Some Traits and Not for Others.

Plant intraspecific variability has been proposed as a key mechanism by which plants adapt to environmental change. In boreal forests where nitrogen availability is strongly limited, nitrogen addition happens indirectly through atmospheric N deposition and directly through industrial forest fertilization. These anthropogenic inputs of N have numerous environmental consequences, including shifts in plant species composition and reductions in plant species diversity. However, we know less about how genetic differences within plant populations determine how species respond to eutrophication in boreal forests. According to plant defense theories, nitrogen addition will cause plants to shift carbon allocation more towards growth and less to chemical defense, potentially enhancing vulnerability to antagonists. Aspens are keystone species in boreal forests that produce condensed tannins to serve as chemical defense. We conducted an experiment using ten Populus tremula genotypes from the Swedish Aspen Collection that express extreme levels of baseline investment into foliar condensed tannins. We investigated whether investment into growth and phenolic defense compounds in young plants varied in response to two nitrogen addition levels, corresponding to atmospheric N deposition and industrial forest fertilization. Nitrogen addition generally caused growth to increase, and tannin levels to decrease; however, individualistic responses among genotypes were found for height growth, biomass of specific tissues, root:shoot ratios, and tissue lignin and N concentrations. A genotype’s baseline ability to produce and store condensed tannins also influenced plant responses to N, although this effect was relatively minor. High-tannin genotypes tended to grow less biomass under low nitrogen levels and more at the highest fertilization level. Thus, the ability in aspen to produce foliar tannins is likely associated with a steeper reaction norm of growth responses, which suggests a higher plasticity to nitrogen addition, and potentially an advantage when adapting to higher concentrations of soil nitrogen.

Erroneous conclusions about current geographical distribution and future expansion of forest insects in Northern Sweden: comments on Hof and Svahlin (2015)

ABSTRACTWe question the validity of the results and the conclusions from a study entitled “The potential effect of climate change on the geographical distribution of insect pest species in the Swedish boreal forest” that was recently published in Scandinavian Journal of Forest Research. The main problem is that for several of the species the current geographical distributions presented in the paper (based on modeling of a limited set of occurrence data) are vastly underestimated compared with distribution maps in standard reference literature and other available occurrence data. As a consequence of that the predicted major future range expansions of these important pest species are also erroneous.

Not erroneous but cautious conclusions about the potential effect of climate change on the geographical distribution of insect pest species in the Swedish boreal forest. Response to Björklund et al. (2015)

ABSTRACTWe argue that the conclusions drawn from the paper “The potential effect of climate change on the geographical distribution of insect pest species in the Swedish boreal forest”, published in the Scandinavian Journal of Forest Research were not erroneous as stated by a letter published in the same journal by Björklund et al. (2015. Erroneous conclusions about current geographical distribution and future expansion of forest insects in Northern Sweden: Comments on Hof and Svahlin (2015). Scand. J. Forest Res)”, but cautious. We regret possible underestimations caused by lack of occurrence records for some species for some areas. However, basing predictions of the impact of future climate change on the distribution of species on current range maps likely leads to grave overestimations of future range predictions since current range maps assume species are homogenously distributed throughout the landscape, which is often not the case. We argue that underestimating the distribution range of pest species rather than overestimating their distribution pinpoints areas that may need extra attention in future better, and therefore chose to be cautious rather than bold. We further like to stress that one should always be aware of possible insect outbreaks throughout the region, not only because predictions may underestimate the future distribution of species but also since the location and likelihood of insect pest outbreaks is not only determined by climatic factors.

Field emergence of native boreal forest species on reclaimed sites in northeastern Alberta

Direct sowing is an underutilized technique for establishing native species on reclaimed land in the mineable oil sands region of northeastern Alberta. This study evaluated the effect of sowing season (spring versus fall) and propagule type (clean seeds versus whole fruit) on emergence of 41 species. Species were sown on 3 disparate sites, each prepared in the standard method for that operation and time and having differing slopes and aspects. Of 41 species, 27 emerged at some level, and of these, 9 species established and were reproducing by seeds, tillers, or rhizomes. These 9 species were smooth blue aster ( Symphyotrichum laeve (L.) A. Love & D. Love [Asteraceae]); shrubby cinquefoil ( Dasiphora fruticosa (L.) Rydb. [Rosaceae]) and wild strawberry ( Fragaria virginiana Duchesne [Rosaceae]), which emerged best from fall-sown seeds; fringed brome ( Bromus ciliatus L. [Poaceae]); Canadian needle grass ( Hesperostipa curtiseta (Hitchc.) Barkworth [Poaceae]); Canada goldenrod ( Solidago canadensis L. [Asteraceae]); Raup’s Indian paintbrush ( Castilleja raupii Pennell [Orobanchaceae]) and prickly rose ( Rosa acicularis Lindl. [Rosaceae]), which emerged equally well from seed broadcast during the fall as during the spring; and Mt Albert goldenrod ( Solidago simplex Kunth [Asteraceae]), which emerged best from seed broadcast in the spring.

The potential effect of climate change on the geographical distribution of insect pest species in the Swedish boreal forest

ABSTRACTWith the expected rising temperatures, outbreaks of insect pests may be more frequent, which can have large consequences on forest ecosystems and may therefore negatively affect the forestry sector. In order to be better able to predict where, but not if, outbreaks may occur in future we investigated the potential future (2070) geographical distribution of 30 prospective insect pest species (Coleoptera and Lepidoptera) by applying species distribution modelling. We also assessed the geographical extent to which the boreal forest in Sweden may be affected. We found that numerous species may experience large increases in their potential distribution in future, which may result in outbreaks in “new” areas. It is therefore likely that more trees will be infested by pests in future, which may have large implications for the Swedish forestry sector.