Boreal Forest Landscape Research Articles

Nutrient uptake along a fire gradient in boreal streams of Central Siberia

AbstractFire can transform the boreal forest landscape, thereby leading to potential changes in the loading of organic matter and nutrients to receiving streams and in the retention or transformation of these inputs within the drainage network. We used the Tracer Additions for Spiraling Curve Characterization (TASCC) method to conduct 17 nutrient-addition experiments (9 single additions of NO3– and 8 combined additions of NH4+ and PO43–) in 5 boreal headwater streams underlain by continuous permafrost and draining watersheds with a range of burn histories (4–>100 y since last burn) in the Nizhnyaya Tunguska River watershed in Central Siberia. Hydrology, ambient nutrient concentration, and the ratio of dissolved organic C (DOC) to nutrients drove rates of nutrient uptake in the streams. Nutrients were taken up with greater efficiency and magnitude under conditions with high flow and reduced diffusive boundary layer (DBL), regardless of watershed burn history. Ambient molar ratio of DOC∶PO43– explained some...

Scale-specific responses of saproxylic beetles: combining dead wood surveys with data from satellite imagery

We investigate relevant scales and cost-efficient methods for measurements of habitat for saproxylic, aspen-associated beetles, in two boreal forest landscapes in south-eastern Norway. We sampled saproxylic beetles with window traps on fresh aspen dead wood and conducted field surveys of dead wood in the surroundings (1, 2 and 3 km radius). In addition, we used maps derived from satellite imagery to extract data on forest age and volume for the same surroundings. We found that species richness of saproxylic beetles was related to dead wood volume estimated by field survey within 1 or 2 km radius from the trapping points. However, the map-derived variable describing area of forest with high levels of deciduous wood volume was the overall best predictor of species richness. The scale of response to this variable differed; species richness of all saproxylic beetles was best predicted by estimates for the 2 km radius whereas richness of species more strongly associated with aspen was best predicted by estimates for the 3 km radius. This might indicate that aspen-associated beetles disperse over larger distances than many other beetles; possibly an adaptation to the scattered distribution and ephemeral nature of aspen dead wood in boreal forests. Our results show that substrate variables must be measured at the scale that is ecologically relevant for the study organism to elicit a response. We also show that remote sensing data -often easy to obtain for large scales—can be used to complement studies of scale-specific responses and thus improve conservation measures for saproxylic beetle species.

Relationships Between Plant Assemblages and Water Flow Across a Boreal Forest Landscape: A Comparison of Liverworts, Mosses, and Vascular Plants

The distribution of water across landscapes affects the diversity and composition of ecological communities, as demonstrated by studies on variation in vascular plant communities along river networks and in relation to groundwater. However, non-vascular plants have been neglected in this regard. Bryophytes are dominant components of boreal flora, performing many ecosystem functions and affecting ecosystem processes, but how their diversity and species composition vary across catchments is poorly known. We asked how terrestrial assemblages of mosses and liverworts respond to variation in (i) catchment size, going from upland-forest to riparian settings along increasingly large streams and (ii) groundwater discharge conditions. We compared the patterns found for liverworts and mosses to vascular plants in the same set of study plots. Species richness of vascular plants and mosses increased with catchment size, whereas liverworts peaked along streams of intermediate size. All three taxonomic groups responded to groundwater discharge in riparian zones by maintaining high species richness further from the stream channel. Groundwater discharge thus provided riparian-like habitat further away from the streams and also in upland-forest sites compared to the non-discharge counterparts. In addition, soil chemistry (C:N ratio, pH) and light availability were important predictors of vascular plant species richness. Mosses and liverworts responded to the availability of specific substrates (stones and topographic hollows), but were also affected by soil C:N. Overall, assemblages of mosses and vascular plants exhibited many similarities in how they responded to hydrological gradients, whereas the patterns of liverworts differed from the other two groups.

Long-term effects of clear-cutting on epigaeic beetle assemblages in boreal forests

Management of boreal forests for timber production has caused changes in forest structures and disturbance regimes, which have influenced a wide range of organisms. The aim of this study was to evaluate how composition of epigaeic (ground-living) beetle assemblages is influenced by stand age and management history in a heavily managed boreal forest landscape. We compared the epigaeic assemblages among stands of three ages: (1) young (8–25years) and (2) middle-aged (40–58years) stands regrown after clear-cutting, and mature stands (80–130years) that had been selectively cut historically but never clear felled. We sampled epigaeic beetles in each of 42 stands, using 10 pitfall traps during seven summer weeks. More than 9000 specimens were collected and identified. The assemblages in young stands differed from those in middle-aged and mature stands, both for the Staphylinidae (rove beetles) and all beetle families combined. Carabidae (ground beetles) composition differed between young and middle aged stands only, and assemblages of Curculionidae (weevils, bark beetles and allies) differed between young and mature stands only. Assemblages of Leiodidae (round fungus beetles) had similar composition in all three stand types. Considering all families, young stands generally harbored fewer species and lower abundances compared with middle aged and mature stands. However, the Leiodidae had similar species richness in all three stand types. The lack of differences in assemblage composition, species richness and abundance between middle aged and mature stands suggests that epigaeic beetle assemblages recolonize following clear-felling. However, our collections included large numbers of unique and usually rare species in mature stands, indicating that old forest is important for the conservation of epigaeic beetles. Furthermore, the lower abundance of these beetles in young stands indicates that an increasing proportion of young stands on managed landscapes will reduce the overall abundances of epigaeic beetle species, with potentially negative impacts on recolonization.

Contribution of unburned boreal forests to the population of black-backed woodpecker in eastern Canada

ABSTRACTBlack-backed woodpecker is known to be a disturbance-associated species, being more abundant in disturbed forest stands than in undisturbed habitats, but its demography and population dynamic still need to be clarified. The present study was conducted in central Quebec within coniferous forests shaped largely by timber harvest and wildfire. The objectives were to compare the age composition of breeding black-backed woodpeckers, nest survival rate and productivity in both disturbed and undisturbed habitats (respectively recently burned and unburned habitats). In addition, we evaluated the general productivity of both habitat types in a simulated boreal landscape. There was a positive relationship between nest age and daily survival rates. Older woodpeckers were the most abundant breeders in unburned habitats and younger birds in one-year-old burns. Although nests in recently burned forests produced more nestlings per successful nest, our simulation of a boreal forest landscape showed that unburned habitat produced about two-thirds more fledglings per year than burned habitat. Globally, unburned habitat may provide woodpeckers more temporally stable resources. Population dynamics of the black-backed woodpecker, at least in our study area, may be explained by resource pulse interactions where populations benefit opportunistically from short-term high-quality habitat, and rely on unburned habitats for long-term persistence.

Can Airborne Laser Scanning (ALS) and Forest Estimates Derived from Satellite Images Be Used to Predict Abundance and Species Richness of Birds and Beetles in Boreal Forest?

In managed landscapes, conservation planning requires effective methods to identify high-biodiversity areas. The objective of this study was to evaluate the potential of airborne laser scanning (ALS) and forest estimates derived from satellite images extracted at two spatial scales for predicting the stand-scale abundance and species richness of birds and beetles in a managed boreal forest landscape. Multiple regression models based on forest data from a 50-m radius (i.e., corresponding to a homogenous forest stand) had better explanatory power than those based on a 200-m radius (i.e., including also parts of adjacent stands). Bird abundance and species richness were best explained by the ALS variables “maximum vegetation height” and “vegetation cover between 0.5 and 3 m” (both positive). Flying beetle abundance and species richness, as well as epigaeic (i.e., ground-living) beetle richness were best explained by a model including the ALS variable “maximum vegetation height” (positive) and the satellite-derived variable “proportion of pine” (negative). Epigaeic beetle abundance was best explained by “maximum vegetation height” at 50 m (positive) and “stem volume” at 200 m (positive). Our results show that forest estimates derived from satellite images and ALS data provide complementary information for explaining forest biodiversity patterns. We conclude that these types of remote sensing data may provide an efficient tool for conservation planning in managed boreal landscapes.

Managing a boreal forest landscape for providing timber, storing and sequestering carbon

Human well-being highly depends on ecosystem services and this dependence is expected to increase in the future with increasing population and economic growth. Studies that investigate trade-offs between ecosystem services are urgently needed for informing policy-makers. We examine the trade-offs between a provisioning (revenues from timber selling) and regulating (carbon storage and sequestration) ecosystem services among seven alternative forest management regimes in a large boreal forest production landscape. First, we estimate the potential of the landscape to produce harvest revenues and store/sequester carbon across a 50-year time period. Then, we identify conflicts between harvest revenues and carbon storage and sequestration. Finally, we apply multiobjective optimization to find optimal combinations of forest management regimes that maximize harvest revenues and carbon storage/sequestration. Our results show that no management regime alone is able to either maximize harvest revenues or carbon services and that a combination of different regimes is needed. We also show that with a relatively little economic investment (5% decrease in harvest revenues), a substantial increase in carbon services could be attained (9% for carbon storage; 15–23% for carbon sequestration). We conclude that it is possible to achieve win–win situations applying diversified forest management planning at a landscape level.

How important is dead wood for woodpeckers foraging in eastern North American boreal forests?

Dead and decaying trees may be a limited resource for woodpeckers in managed forests, especially for species that rely on dead wood for nesting and foraging. Whereas recent nest web studies greatly increased our understanding of nest tree use by woodpeckers, knowledge on woodpeckers foraging requirements is much less developed. We quantified and compared tree selection patterns and foraging behavior of six bark-foraging woodpeckers – downy woodpecker (Picoides pubescens), hairy woodpecker (Picoides villosus), American three-toed woodpecker (Picoides dorsalis), black-backed woodpecker (Picoides arcticus), yellow-bellied sapsucker (Sphyropicus varius) and pileated woodpecker (Dryocopus pileatus) – that co-occur in eastern boreal forests of North America. A total of 271 observation bouts and more than 600 foraging trees were recorded at three study sites characterized as mixedwood, conifer, and burn. Our results show that dead wood represents an important foraging substrate for most bark-foraging woodpeckers in Canadian eastern boreal forests. However, significant differences in individual species were found with regard to substrate use patterns, foraging behavior and associated prey. Woodpeckers were categorized according to their selection for specific stages of tree degradation, with the yellow-bellied sapsucker and the pileated woodpecker representing opposite ends of this gradient. The black-backed woodpecker showed the highest use of dead wood and was very specific in its tree selection by using mostly recently dead trees. We emphasize that providing foraging substrates for most woodpecker species not only requires maintaining dead wood but also paying heed to the underlying dynamics of dead wood (e.g. recruitment and degradation) in managed boreal forest landscapes.

Defining fire environment zones in the boreal forests of northeastern China

Fire activity in boreal forests will substantially increase with prolonged growing seasons under a warming climate. This trend poses challenges to managing fires in boreal forest landscapes. A fire environment zone map offers a basis for evaluating these fire-related problems and designing more effective fire management plans to improve the allocation of management resources across a landscape. Toward that goal, we identified three fire environment zones across boreal forest landscapes in northeastern China using analytical methods to identify spatial clustering of the environmental variables of climate, vegetation, topography, and human activity. The three fire environment zones were found to be in strong agreement with the spatial distributions of the historical fire data (occurrence, size, and frequency) for 1966–2005. This paper discusses how the resulting fire environment zone map can be used to guide forest fire management and fire regime prediction.

Production and retention of methylmercury in inundated boreal forest soils.

The Flooded Uplands Dynamics Experiment (FLUDEX) was an ecosystem-scale study examining the production of methylmercury (MeHg) and greenhouse gases from reservoirs constructed on an upland boreal forest landscape in order to quantify their dependence upon carbon stores. We detail the within-reservoir production and storage of MeHg before, during, and nine years after the experiment. The reservoirs were net MeHg producers during the first two years of flooding, and net demethylating systems afterward. During years 1-3, a rapid pulse of MeHg and total Hg was observed in floodwater, followed by substantial increases in MeHg in seston and sediment. Resampling of the dry reservoirs nine years after the experiment ended indicated that organic soil MeHg was still 8 to 52-fold higher than preflood conditions, and averaged 86% of the levels recorded at the end of the third flooding year. Both total Hg and MeHg retention in soil were a strong function of organic carbon content. The time scale of soil MeHg retention may help explain the decadal time lag frequently observed for the decrease of piscivorous fish Hg concentrations in new reservoirs. Predicted extreme precipitation events associated with climate change may serve to make landscapes more susceptible to this process.

Quantifying influences and relative importance of fire weather, topography, and vegetation on fire size and fire severity in a Chinese boreal forest landscape

Fire size and fire severity are two crucial parameters for describing fire regimes that reflect spatial heterogeneities of fire spread behavior and its interaction with the environment. Determining how environmental controls regulate these two metrics of the fire regime is of critical importance for predicting response of fire to climate change and designing strategic fire management plans. Here, we evaluated influences and relative contributions of fire weather, topography, and vegetation on fire size and fire severity in a Chinese boreal forest ecosystem. We also compared how relative contributions vary along a continuous gradient of spatial scales using a moving-window resampling approach. Results showed fire weather was the dominant driving factor for fire size, while vegetation and topography exerted stronger influences on fire severity. Such relative influences on fire size and fire severity possessed different scale dependence. For fire size, small burns (<130ha) were mainly constrained by vegetation as it accounted for nearly 43% relative importance, but larger burns (>200ha) were more strongly influenced by extreme fire weather conditions, which accounted for more than 50% relative importance. In contrast, the relative importance of fire weather on fire severity was always less than 20% across the entire range of spatial scales, while relative contributions of vegetation were relatively stable and always greater than 45%. Our study suggests that fuel treatments may have little effect on reducing fire size in boreal forests, but may function to mitigate the severity of future fires. Vegetation type and terrain conditions are important factors to consider for improving efficiency of fuel management.

Diversity patterns of wild bees and wasps in managed boreal forests: Effects of spatial structure, local habitat and surrounding landscape

Understanding patterns of species diversity at different spatial scales is important for adapting management and conservation efforts. We have therefore studied wild bee and wasp (Hymenoptera: Aculeata) diversity structure in forest landscapes and evaluated the importance of conservation management at the local and landscape levels. Surveys were conducted at 32 clearcuts in eight landscapes in a managed boreal forest region. We assessed the influence of local habitat and landscape composition on species richness patterns and the effect of prescribed burning and landscape affinity on species composition for all bees and wasps as well as ecological and functional groups. The relative contribution of alpha and beta diversity on the regional level was assessed by diversity partitioning and the beta diversity between landscapes further partitioned into components of species turnover and nestedness. Bee and wasp species richness increased with high flower richness and clearcut size, and species composition differed between burned and unburned sites. Thus, flower-rich early-successional sites in boreal forest landscapes are important habitats for wild bees and wasps. To support this fauna, openness should be maintained for extended periods by delaying or avoiding tree plantation at flower-rich spots on clear-cuts. Beta diversity between landscapes accounted for the greatest proportion of the total regional gamma diversity, and over 70% of this diversity was due to species turnover. This implies that in order to maintain regional diversity, conservation efforts should be spatially dispersed, i.e. applied to every landscape of a few hundred square kilometers and adapted to the local species assemblages.

Carbon storage and stand conversion in a pine-dominated boreal forest landscape

Although climate change is expected to have wide-ranging effects on the distribution and character of forest biomes, major changes to forest cover are enacted as part of normal forest management. In this paper, I compared ecosystem carbon storage in a chronosequence of forest stands dominated by two common pine species – jack pine (Pinus banksiana Lamb.) and red pine (Pinus resinosa Ait.) growing on homogeneous beach ridge sands in Sandilands Provincial Forest (SPF), Manitoba. In SPF, there has been a history of converting stands formerly dominated by jack pine to regularly spaced red pine plantations. Ecosystem carbon (C) storage was dominated by soil and live tree ecosystem components. However, while there were no interspecific differences in soil storage, the red pine stored a larger proportion of ecosystem C in live trees than jack pine, a difference that appeared to grow greater with age. Differences in C storage appeared to be driven by divergent patterns of longevity and vulnerability to senescence and disturbance (e.g. windthrow) in jack pine and red pine. These differences in life history traits also appeared to be responsible for contrasting accumulation patterns of woody debris and litter with stand age. Consistently higher canopy cover in red pine stands may also have been responsible for age-related reductions in C storage in the herbs and short shrubs (those <1.5m tall) in red pine. These results indicate that changing the character of forest cover, even when closely related species are substituted for each other, can produce large differences in overall C storage, as well as in the distribution of C among ecosystem compartments.

Estimating bee and wasp (Hymenoptera: Aculeata) diversity on clear‐cuts in forest landscapes – an evaluation of sampling methods

Abstract To assess species diversity efficiently and adequately, it is important to understand how species diversity assessments are affected by sampling effort and methodology. We evaluated methods for sampling bees and wasps on clear‐cuts in managed boreal forest landscapes to assess the effects of trap type, sampling effort and time within season on observed species diversity. We found that pan traps and window traps captured similar numbers of species, whereas a much lower number was captured by trap‐nests. The efficiency of the trap types varied between species groups, with pollen‐collecting bees being most effectively sampled by pan traps and dead wood‐nesting bees and wasps by window traps. Species turnover over time was moderate, and consequently the sampling period could be reduced to 5–6 weeks in boreal forests and similar habitat types without a major decrease in the number of species collected. We recommend using window traps for bees and wasps in forest habitats. Combining trap types is recommended if the aim is to collect broad species assemblages, while single types are most useful for the efficient collection of specific species groups.

Performance of forest bryophytes with different geographical distributions transplanted across a topographically heterogeneous landscape.

Most species distribution models assume a close link between climatic conditions and species distributions. Yet, we know little about the link between species' geographical distributions and the sensitivity of performance to local environmental factors. We studied the performance of three bryophyte species transplanted at south- and north-facing slopes in a boreal forest landscape in Sweden. At the same sites, we measured both air and ground temperature. We hypothesized that the two southerly distributed species Eurhynchium angustirete and Herzogiella seligeri perform better on south-facing slopes and in warm conditions, and that the northerly distributed species Barbilophozia lycopodioides perform better on north-facing slopes and in relatively cool conditions. The northern, but not the two southern species, showed the predicted relationship with slope aspect. However, the performance of one of the two southern species was still enhanced by warm temperatures. An important reason for the inconsistent results can be that microclimatic gradients across landscapes are complex and influenced by many climate-forcing factors. Therefore, comparing only north- and south-facing slopes might not capture the complexity of microclimatic gradients. Population growth rates and potential distributions are the integrated results of all vital rates. Still, the study of selected vital rates constitutes an important first step to understand the relationship between population growth rates and geographical distributions and is essential to better predict how climate change influences species distributions.

A note on suitable viewing configuration for retrieval of forest understory reflectance from multi-angle remote sensing data

The contribution of understory vegetation especially to the reflectance of boreal forest landscapes cannot be ignored. In this letter, we identify the most suitable angular configuration for accurate retrieval of the understory signal. We use a new high angular resolution bidirectional reflectance factor data set with accompanying in situ measurements of understory reflectance in two RAdiation transfer Model Intercomparison (RAMI) mature stands in Järvselja, Estonia. Our results are pertinent towards the ultimate goal of achieving more reliable estimates of biophysical properties of the tree layer through separating the effect of understory on forest reflectance.

Proportions of saproxylic beetle populations that utilise clear-cut stumps in a boreal landscape – Biodiversity implications for stump harvest

Many saproxylic insects (insects dependent on deadwood) are threatened because the amounts of suitable substrate, coarse woody debris (CWD), are low in managed forests. Harvesting clear-cut stumps for bioenergy will decrease these amounts further and may therefore contribute to loss of biodiversity. Earlier studies have demonstrated that many saproxylic beetle species utilise clear-cut stumps. However, the importance of stumps compared with other kinds of deadwood remains unknown. In particular, some species adapted to sun-exposed deadwood created by disturbances might, in managed forest landscapes, be dependent on stumps in clear-cuts. In the present study we quantify the proportions of landscape-wide populations of saproxylic beetles that are recruited from clear-cut stumps in a managed boreal forest landscape. The amount of bark on clear-cut stumps and population densities (beetles per m2 bark) were estimated for a 24,499ha landscape in Sweden. Our data were pooled with estimates from a similar study in the same landscape, including all other types of CWD and beetle densities. The clear-cut stumps were estimated to contribute 15.5% of total bark to CWD in the landscape. For spruce, clear-cut stumps contributed 37.9% of the total bark. Of 39 analysed beetle species, 13 were estimated to have more than 10% of their populations in clear-cut stumps, 9 more than 50%, and 5 more than 80%. Clear-Cut stumps are thus an important breeding substrate for many beetle species and consequently, intensive stump harvest risks decreasing biodiversity.

Breeding in the stable boreal landscape: lake habitat variability drives brood production in the teal (Anas crecca)

Summary Boreal forest lakes are normally considered stable environments, but from a duck's point of view, both resource abundance and habitat quality in the lakes may differ from 1 year to another. Duck species differ in their flexibility to respond to variation in environmental factors, such as habitat quality, habitat variability and weather. Anas crecca, the common teal, has been suggested to be a species that can readily colonise newly formed habitat. We studied the effect of habitat quality (invertebrate food resources, amount of spring flood, beaver flood abundance, predation pressure), weather (temperature, precipitation, timing of ice break‐up) and pair abundance on breeding success of teal at the landscape scale in Southern Finland. We used 20 years of data (1989–2008) from a study area consisting of 50 lakes. This is typical boreal breeding area for the teal, whose population size is markedly variable. We express breeding success as number of broods in two different age classes. The number of broods in both age classes was explained well by habitat quality, but different variables seem to operate during different phases of the breeding season. Increases in abundance of breeding pairs and of food led to increased production of younger broods. Habitat factors including food and flood abundance were the most important predictors for older broods, which are the more influential in terms of recruitment. These factors manifested in an age‐specific manner, highlighting the importance of comprehensive breeding time surveys of boreal breeding ducks to understand variation in their recruitment. Our research underlines the importance of high‐quality habitats for breeding teal populations in the boreal forest landscape. The existence of these habitats depends substantially on human actions, such as managing beaver populations and preserving seasonal pond habitats.

Do conservation measures in forest work? A comparison of three area-based conservation tools for wood-living species in boreal forests

Loss of natural forests and decline in forest biodiversity has led to several policy initiatives in recent years. Despite this, the importance of smaller set-asides vs forest reserves for conservation measures is poorly understood. We aimed to evaluate the importance of three different area-based conservation measures commonly used in north-European forests; retention patches, woodland key habitats and forest nature reserves. We did this for two contrasting ecological systems; fungi in late-decay spruce logs and beetles in early-decay aspen snags.Eight replicated sites for each of the three conservation measures were investigated in a total of four boreal forest landscapes in south-Norway. Fungi were surveyed on existent late-decay spruce logs in two landscapes, and beetles trapped on experimentally added aspen dead-wood units in three landscapes. Richness and species composition were analyzed separately for specialist and generalist species.We found larger differences in species composition between conservation measures for old-growth fungi specialists than generalists, although species richness patterns were less clear. The main contrast was found between nature reserves and retention patches. On the other hand, specialist beetles associated with early-decay aspen showed no difference between set-asides. The assemblage of aspen generalist beetles tended to be richest in the woodland key habitats and showed clear differences between the conservation measures. There was considerable variation in response to conservation measures between landscapes, related to quality of the set-asides.Species specialized to an ephemeral, early-decay system were able to utilize such substrates in all of the conservation measures, while the smaller and more modified set-asides could not cater for the specialists dependent on stable, late-decay systems. Species with broader habitat demands in general responded to all conservation measures. We conclude that retention patches, woodland key habitats and forest reserves fill complementary functions for wood-living species in boreal forest and should all be part of future forest conservation strategies.

Relative effects of climatic and local factors on fire occurrence in boreal forest landscapes of northeastern China

Fire significantly affects species composition, structure, and ecosystem processes in boreal forests. Our study objective was to identify the relative effects of climate, vegetation, topography, and human activity on fire occurrence in Chinese boreal forest landscapes. We used historical fire ignition for 1966–2005 and the statistical method of Kernel Density Estimation to derive fire-occurrence density (number of fires/km2). The Random Forest models were used to quantify the relative effects of climate, vegetation, topography, and human activity on fire-occurrence density. Our results showed that fire-occurrence density tended to be spatially clustered. Human-caused fire occurrence was highly clustered at the southern part of the region, where human population density is high (comprising about 75% of the area's population). In the north-central areas where elevations are the highest in the region and less densely populated, lightning-caused fires were clustered. Climate factors (e.g., fine fuel and duff moisture content) were important at both regional and landscape scales. Human activity factors (e.g., distance to nearest settlement and road) were secondary to climate as the primary fire occurrence factors. Predictions of fire regimes often assume a strong linkage between climate and fire but usually with less emphasis placed on the effects of local factors such as human activity. We therefore suggest that accurate forecasting of fire regime should include human influences such as those measured by forest proximity to roads and human settlements.