Diversity of polyporous fungi (Polyporaceae) in northern boreal forests: effects of forest site type and logging intensity

The effects of forest site type and logging intensity on polyporous fungi were studied in subxeric, mesic and herb-rich forests and spruce mires in northern Finland. The species richness of polypores did not follow the fertility gradient of the site types, but was connected with the amount and diversity of coarse woody debris (CWD). The total number of species, and the numbers of indicator and threatened species were equal in subxeric pine forests and in more fertile spruce-dominated stands. The species composition of pine-dominated forests differed conspicuously from that of spruce-dominated site types. The total number of species was not affected by logging intensity, but no virgin forest species or threatened species were found on the sites where the number of cut stumps exceeded 150 stumps ha^?1. Increasing logging intensity decreased the number of polypore observations, indicating reduced substrate availability. The results stress the importance of protecting not only fertile spruce-dominated stands, but also poorer, pine-dominated forests, and sites with high and diverse CWD content.     

Change detection using bi-temporal aerial photographs and registration at the stand level

There is a trend to continuously update forest data in forest management planning systems. Thus, changes in forest stands caused by, e.g. operations and storm damages should be detected in order to ensure the accuracy of forest data and beneficial decisions related to the treatments of the stands. This justifies the application of aerial photographs in change detection as being reasonable because they are already used in forest management planning. This study presents a semi-automatic method based on bi-temporal aerial photographs and registration at the stand and segment levels for the detection of changes in boreal forests. Linear stepwise discriminant analysis and the non-linear k-nearest neighbour (k-NN) method were tested and statistically compared in classification. The classification results at the stand level were found to be better than at the segment level. Compared to previous studies, the results of this study demonstrate remarkable improvement in the classification accuracy of moderate changes. The results showed that change detection substantially improved when the registration at the stand level was used, especially in the detection of thinned stands. To some extent, the method can be already applied operationally.     

Stand structure of hemiboreal old-growth forests: Characteristic features,variation among site types,and a comparison with FSC-certified mature stands in Estonia

To improve the silvicultural targets for ecologically sustainable forestry, we quantified functionally important structural features for the first time in a representative set of old-growth forests in hemiboreal Europe. Altogether, 23 old-growth stands of four site-type groups were compared with mature commercial stands nearby in the Estonian state forests that hold the Forest Stewardship Council (FSC) certificate of sustainable forestry. These two treatments did not differ significantly in terms of tree-species diversity, volumes of woody debris of <20 cm diameter (including fine woody debris) and its decay-stage composition. However, mature stands had many more early-successional trees and lacked late-successional deciduous species; they also had a higher overall density and volume of live trees, due to abundant individuals of 10–39 cm diameter at breast height. Old-growth stands had at least twice as many live trees ≥40 cm, standing dead trees ≥30 cm and lying wood ≥20 cm in diameter, any freshly fallen debris, and regeneration. For lying wood ≥20 cm in diameter, the treatment effect depended on site type: both treatments of Vaccinium-type dry boreal forests were remarkably deadwood-poor (indicating historical management of the old-growth stands), while mature eutrophic stands of Aegopodium-type were most impoverished relative to old-growth levels. We conclude that many functional characteristics of old growth were present in the FSC-certified, mostly naturally regenerated, commercial stands. The main problem is the lack of very large trees, particularly of late-successional deciduous species, which should be addressed by their well-planned retention in cut areas and reconsideration of salvage logging strategies. A dense regeneration in old-growth stands also indicated the potential of selection cuttings. The study highlighted the need for region- and site-type specific numerical targets for sustainable forest management, which in the hemiboreal region should address the characteristic occurrence of late-successional deciduous trees on fertile soils and higher natural deadwood volumes than in typical boreal forests. For certification, the issues of structural impoverishment revealed both the inadequacy of some silvicultural practices and some indicators set by the national FSC-standard in Estonia.     

Long-term influence of fire and harvesting on boreal forest age structure and forest composition in eastern Québec

In boreal forests, historical variations in the area disturbed by natural disturbances or harvesting have rarely been compared. We measured temporal and spatial variations in areas affected by severe fires and clearcutting throughout the 20th century in a 57, 332 km² section of the eastern Canadian boreal forest. We examined the effects of these disturbances on spatio-temporal variations in the abundance of forests >60 years. Natural variability for the abundance of forests >60 years was estimated from simulations of natural disturbance regimes. We also measured compositional and structural differences between three categories of stands originating from relatively recent disturbances (∼50 years; clearcutting, fires, and clearcutting followed by fires), and one category of stands that were undisturbed for at least 200 years. At the regional level, we observed that forests >60 years gradually became scarcer throughout the 20th century due to a gradual expansion of harvested areas, an effect most pronounced in the southern part of the region, where mature and old forest abundance was clearly outside the range of natural variability at the end of the studied period. At the stand level, forest composition and structure differed between stand-origin categories: clearcutting-origin stands contained more balsam fir (Abies balsamea), fire-origin stands more black spruce (Picea mariana), and fire/clearcutting-origin stands more hardwoods (Betula papyrifera and Populus tremuloides). Overall, we estimate that strict forest management targets based on natural disturbance regimes will be difficult to achieve in eastern North-American boreal forests, most notably because contemporary disturbance rates, including both clearcutting and fire, have gradually become higher than the fire rates observed during the preindustrial period.     

Availability of standing trees for large cavity-nesting birds in the eastern boreal forest of Québec,Canada

Large cavity-nesting birds depend on large-diameter trees for suitable nest sites. The increased spatial extent of commercial timber harvesting is modifying forest structure across the land base and may thus compromise the availability of large trees at the landscape scale. In this study, our objectives were to (1) characterize the availability of large living and dead trees in old-growth stands dominated by different tree species and surficial deposits that encompass the range of natural cover types of eastern Québec's boreal forest; (2) analyze the distribution of trees among decay-classes; and (3) compare the availability of large trees in unharvested, remnant, and harvested stands for the entire range of decay-classes. A total of 116 line transects were distributed across unharvested forests, remnant linear forests, and cutblocks in cutover areas. Unharvested forest stands (black spruce [Picea mariana], balsam fir [Abies balsamea]–black spruce, balsam fir–white spruce [Picea glauca] and balsam fir) reflected a gradient of balsam fir dominance. The remnant forests selected were isolated for 5–15 years. Analyses were performed at two diameter cut-off values. Trees with DBH ≥20 cm were considered for availability of total trees whereas trees with DBH ≥30 cm were considered for availability of large trees. Forest stands comprised high proportions of standing dead trees (33% of all stems, 8% were large dead stems). Availability of total and large standing trees increased with the dominance of balsam fir in stands. Forest stands located on thick surficial deposits showed higher densities of large dead trees for every stand type suggesting a higher productivity on those sites. Availability of stems according to decay-classes showed a dome-shaped distribution with higher densities of snags in intermediate decay stages. However, for large stems, black spruce stands showed a significantly lower availability that was consistent across all decay-classes. In linear remnant forests, pure balsam fir stands were absent. Remnant stands thus showed a much lower availability in large trees when compared with unharvested balsam fir stands. Clearcuts had the lowest densities of dead trees across sampled stands. Current even-aged management practices clearly affect availability and recruitment of large trees, therefore forest-dwelling wildlife relying on these structures for breeding is likely to be affected by large-scale harvesting in coniferous boreal forests.     

Epiphytic lichen diversity in old-growth and managed Picea abies stands in Alpine spruce forests

In the last decades, a large body of literature has grown to evaluate the impact of forest management on epiphytic lichens in boreal coniferous forests. However, information is still lacking on coniferous forests of the Alps. This study compares lichen diversity between spruce forest stands of four successional stages: (1) young, (2) intermediate, (3) mature forests managed for timber production with a rotation cycle of 120–180 years, and (4) old-growth protected forests. The emphasis was placed on the occurrence of nationally rare and calicioid species (lichens and fungi traditionally referred to as Caliciales, known to be indicative of forest age and continuity). For each forest successional stage, four plots were selected. In each plot, 7 spruce individuals were surveyed for epiphytic lichens according to a standardised sampling method. Species richness increased from young to mature stands, while no difference was detected between mature and old-growth stands. This pattern was also confirmed for rare and calicioid species which are, however, more frequent in old-growth stands. Differences in species composition were also found between the different forest successional stages. Mature and old-growth plots slightly overlap, indicating that to some extent comparable lichen assemblages could be found in these stands. A nested pattern of species assemblages was found, old-growth stands hosting most of the species which were also found in stands belonging to the previous forest successional stages. Our results support the hypothesis that the management regime applied to spruce forests of the Italian Alps renders mature stands managed for timber production somewhat similar to old-growth stands as lichen habitat. However, we found a higher complexity in old-growth forests, and many species of conservation concern clearly preferred old-growth stands. In this perspective, a further prolongation of the normal cycle it is likely to be a most favourable conservation-oriented management to be recommended at least within protected areas and Natura 2000 sites, where conservation purposes should receive a high priority.     

Patterns of field layer invertebrates in successional stages of managed boreal forest: Implications for the declining Capercaillie Tetrao urogallus L. population

Capercaillie (Tetrao urogallus L.) populations in Finland have decreased markedly during past decades. One of the assumed reasons is the decreased quality of brood feeding grounds since current forest management transfers mature forests to younger successional stages. We studied how different types of managed Finnish forests offer resources for capercaillie broods by comparing the vegetation and invertebrate fauna of four successional stages in the two most common forest types in Finland, spruce dominated Vaccinium myrtillus (MT) and pine dominated Vaccinium vitis-idaea (VT) type. Forest age class had a significant effect on the cover of bilberry. There was a positive correlation between bilberry cover and the biomass of larvae and of all invertebrates (including all developmental stages) both at the stand and the sample level. Both forest type and age class significantly affected the biomass of larvae. Mature stands and young stands had the highest biomass of larvae in both MT and VT. In both forest site types the sapling stands hosted the smallest biomass of larvae. The results suggest that successional stages that follow clear cutting seriously lowers the food availability for capercaillie chicks and also reduces the shelter that field layer might provide. However, already the young stages that follow sapling phases seem to provide both bilberries and invertebrates so it is quite unlikely that the bilberry abundance alone could explain the dramatic decline of the capercaillie.     

Temperature sensitivity and recruitment dynamics of Siberian larch (Larix sibirica) and Siberian spruce (Picea obovata) in northern Mongolia’s boreal forest

This study sought to clarify the recruitment dynamics and growth of Siberian larch (Larix sibirica) and Siberian spruce (Picea obovata) in relation to changing temperatures in northern Mongolia. These tree species are the primary forest species found in the closed-canopy boreal forest of north-central Mongolia. Mongolia’s boreal forests exist along the southern terminus of the Siberian boreal system in both pure and mixed species stands. I collected tree cores and cross-sections as well as site and tree stature parameters from 118 forest plots in the Darhad valley of north-central Mongolia. Principle components analysis of 130 L. sibirica tree ring series informed the construction of two composite chronologies for this species. A chronology for P. obovata was developed using 24 tree ring series. Correlation analysis between tree ring indices and temperature data showed two distinct growth signals: a positive response to growing season temperatures was exhibited by one L. sibirica chronology and a negative response to spring temperatures was exhibited by a second L. sibirica chronology. The P. obovata chronology exhibited strong negative correlations with mean monthly and mean maximum monthly growing season temperatures. Multiple analyses of variance (MANOVA) indicated that tree stature (dbh, height) and site parameters (latitude, longitude, slope, aspect, elevation) did not significantly predict growth response or species. Forest recruitment events appear episodic for both species. Synchronous establishment of saplings, based on approximate root collar age, suggests an initial floristic model for mixed composition stands likely due to supra-annual variations of fire, land-use and climate. Forest management activities in the region should consider the diverging growth response to temperature shown here by prioritizing protection forests and the various ecosystem services provided by forests in arid ecosystems. In addition, promoting selection harvests over clear-felling would maximize future alternatives under conditions of rapidly changing climate. Care should be taken in new forest management planning activities until adequate information exists on the likely trajectory of this system due to climate-induced forest change.     

Spatiotemporal dynamic of European beech (Fagus sylvatica L.) in Slovenia, 1970–2005

Based on data acquired from the spatial information system Silva-SI, the majority of the entire forest area in Slovenia (22,220 forest compartments with a total area of 7446 km², classified into eight forest categories) was analysed for changes in the distribution of European beech (Fagus sylvatica L.) in the period 1975–2005 using a binary logistic regression model in terms of selected site, stand and management variables. Additionally, changes in the abundance of beech in forest stands in which beech was present at the beginning and the end of the analysed period were analysed. Beech expanded its area by more than 1200 ha per year on average, i.e. the annual expansion rate amounted to 0.24%. Among the 18 studied variables, three site, four stand and no management variables were included in the binary logistic regression model of beech expansion. Beech expansion was more pronounced at lower altitudes, on sites with steep topography, and on sites with a higher proportion of beech in potential natural vegetation. The probability of beech expansion reduced by a factor of 0.54 when the distance to the nearest compartment with beech increased by 1 km. Among other stand variables, the proportion of early successional phases and the proportion of silver fir (Abies alba Mill.) and Norway spruce (Picea abies (L.) Karst.) also influenced the expansion of beech. During the observed period the growing stock of beech almost doubled, its proportion in total growing stock increasing from 27% to 32%. Significant differences were found in changes of beech proportion in the total growing stock among different forest categories; a decrease in the beech proportion was registered in alpine coniferous forests and thermophilous deciduous forests, while in other forest categories the proportion of beech increased. The recent development of forest stands and their current structure indicate a further expansion of beech and an increase in the proportion of beech in forest stands.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Predicting stand-thinning maturity from airborne laser scanning data

Abstract

Airborne laser scanning (ALS) has been used in recent years to acquire accurate remote-sensing material for carrying out practical forest inventories. Still, much of the information needed in forest management planning must be collected in the field. For example, forest management proposals are often determined in the field by an expert. In the present study, statistical features extracted from ALS data were used in logistic regression models and in nonparametric k-MSN estimation to predict the thinning maturity of stands. The research material consisted of 381 treewise measured circular plots in young and advanced thinning stands from the vicinity of Evo, in southern Finland. Timing of thinning was determined in the field by an expert and coded as a binary variable. Models were developed (1) to locate stands that will reach thinning maturity within the next 10-year period and (2) for stands in which thinning should be done immediately. For comparison purposes, logistic regression models were formulated from accurately field-measured stand characteristics. Logistic regression models based on ALS features predicted the thinning maturity with a classification accuracy of 79% (1) and 83% (2). The respective percentages were 66% and 83% with models based on field-measured stand characteristics and 70% and 86% with k-MSN. The study showed that ALS data can be used to predict stand-thinning maturity in a practical way.     

Habitat selection by forest-dwelling caribou in managed boreal forest of eastern Canada: Evidence of a landscape configuration effect

Habitat alteration caused by forest harvesting seems to contribute to the decline of forest-dwelling caribou, an ecotype of woodland caribou (Rangifer tarandus caribou) inhabiting the boreal ecosystem. To serve as basework to the establishment of conservation measures for the species, we have studied the hierarchical habitat selection of forest-dwelling caribou in a boreal landscape of Québec strongly impacted by logging. Fifteen females were surveyed by GPS telemetry between April 2004 and March 2006. Home ranges showed a high proportion of 90–120 year-old forests, a low proportion of regenerating forests (20–40 years old) and a tendency to include a greater proportion of 6–20 year-old clearcuts in relation to their availability in the study area. At the home range scale, selection patterns differed between periods, possibly reflecting specific requirements linked to caribou life cycle. Caribou selected open lichen woodlands throughout the year while mature closed forests (≥50 years) were selected uniquely during summer. The 6–20 year-old clearcuts were avoided during calving, in summer and during the rutting period but were selected during spring. Our results indicate that mature forest and open lichen woodlands are highly selected forest cover types by caribou at both spatial scales. Although clearcuts were generally avoided at the home range scale, such avoidance was not observed at the larger scale, the search for 90–120 year-old forests being hampered by a uniform distribution of clearcuts. An a posteriori landscape analysis highlighted the spatial association between 6–20 year-old clearcuts and 90–120 year-old forests, an association that can be explained by the current regulations used in Québec. Our results underline the importance of pursuing research concerning the impact of such an exploitation regime on the long-term maintenance of the forest caribou in the boreal landscape.     

Effects of Forest Management on Field Layer Vegetation: A Comparison Between Finnish and Russian Karelia

The effects of forest management on the field layer vegetation were compared between Finnish and Russian Karelia in a total of 46 mature stands representing pine, spruce and deciduous forests. In Finland, the number of species was slightly higher in each forest type. Many grassland species, such as Galium boreale , Lathyrus pratensis , and Veronica officinalis , were more abundant in Finnish deciduous stands (14.4 species, mean cover 15.8%) than in Russian stands (9.6 species, mean cover 11.5%). Dwarf shrubs, such as Calluna vulgaris (mean cover: Fin 3.3%, Rus 7.7%) and Vaccinium vitis-idaea (Fin 25.0%, Rus 26.9%) in pine stands, and Vaccinium myrtillus (Fin 22.9%, Rus 31.5%) in spruce stands, were more abundant in Russia. Ferns and graminoids exhibited no differences between the two countries. The observed differences were likely to result from the lower tree stand density, more extensive fragmentation and fertilisation of forests in Finland, the higher frequency of forest fires and more intensive grazing in Russian forests, and from differences in natural conditions between Finnish and Russian Karelia.     

Lichen communities on treefall mounds depend more on root-plate than stand characteristics

Large uprooted trees are typical old-forest structures that provide distinct microsites for sessile organisms. While the habitat value of treefall pits for plants is relatively well known, the characteristic exposed root-plates of treefall mounds, which may require different management, have received less attention. The aim of the current study was to explore key factors of lichen incidence and their community characteristics on root-plates. We mapped and described treefall mounds in 24 stands (2 ha each) in a balanced design representing mixed stands of two site types (mesotrophic; drained swamp) and two management types (old growth, mature commercial forest) in hemiboreal Estonia. First, the occurrence of any lichens and of a specialized pin lichen, Chaenotheca furfuracea, was recorded on all 1207 mounds found. According to multi-level logistic regression models, their incidence depended on every mound-scale variable tested: there were independent positive effects of root-plate area and treefall age, spruce treefall, and the absence of exposed pit. In contrast, weak stand-scale effects only appeared when their interactions with mound-scale variables were included or some main effects were eliminated. C. furfuracea also occurred more frequently where other inhabited root-plates were nearby, and such dispersal limitation interacted with habitat quality. Secondly, full lichen communities were described in detail on a subsample of 84 root-plates of Norway spruce (Picea abies). Altogether 48 lichen species were recorded, including eight red-listed or nationally rare species. The communities on large fresh root-plates and in mature drained stands had distinct species composition, while communities of older mounds and in old-growth stands converged in species composition. We conclude that lichen incidence on root-plates is mostly determined by colonization probability, and commercial forests can support a diverse lichen biota when large treefall mounds, particularly of P. abies and of >10 years age are provided. However, given some differences of lichen communities in old growth, and because treefall issues conflict with other management objectives in commercial forests, optimised management of treefall areas there should be complemented by their strict protection in reserves.     

Natural stand structures, disturbance regimes and successional dynamics in the Eurasian boreal forests: a review with special reference to Russian studies

? This review summarizes early stand-scale studies of pristine forest structures, disturbance regimes and successional patterns carried out in boreal Eurasia. We attempt to reveal, characterize and classify stand dynamic types that can be used as templates for nature-based forest management.

? The studies reviewed demonstrate multiple successional pathways in stand development in all types of pristine forests. All-aged stands driven by small-scale disturbances are formed over successional development of several hundreds of years. This endogenous development can be interrupted by stand-replacing or partial disturbances leading to successions with even-aged or cohort-structured stands, respectively. In Western Europe, the most common disturbances are windthrows, surface fires and fluctuations in moisture regime; in Eastern Europe and Siberia, the most common disturbances are crown and surface fires and insect outbreaks. Type, return interval and severity of disturbances are strongly influenced by the site conditions and successional stage of a stand.

? Based on characteristics of forest stands and disturbance regime, four main types of pristine boreal forest stand dynamics can be distinguished: (1) even-aged, compositional change dynamics, (2) even-aged, mono-dominant dynamics, (3) cohort dynamics and (4) fine-scale gap dynamics. These types can be mimicked in developing scenarios of ecological sustainable forest management in Eurasian boreal forests.

     

Effect of thinning on LAI variance in heterogeneous forests

Leaf Area Index (LAI) is a main variable controlling carbon and water fluxes. This paper estimated the effect of thinning on the spatial distribution of leaf area in French forests. While many studies have focused on average LAI, we estimated clumping and measured both average LAI and the variation around it. LAI was derived from digital hemispherical photos at three sites: an unmanaged Fagus sylvatica forest in temperate area (control site), a mixed Mediterranean forest of Quercus ilex and Pinus halepensis, and regeneration of F. sylvatica under a mature stand of Pinus nigra in mountainous area. LAI measurements were also made with LAI 2000 devices over 5 years (from 1994 to 1998) within forest stands dominated by either beech (F. sylvatica L.), by oaks (Quercus petraea (Matus) Liebl., Quercus robur (Matus) Liebl.), or by Scots Pine (Pinus sylvestris L.). Thinning led to a variable decrease in LAI. The coefficient of variation of LAI (CV_LAI) provided a useful ecological index of the level and type of thinning. For undisturbed stands, CV_LAI varied from 10% to 20%, corresponding to the higher average LAI values. Disturbances created by thinning increase LAI spatial variability, resulting in larger CV_LAI values for all stands considered. Possible explanations of these results and use in remote sensing were discussed.     

Effects of artificial afforestation and successional stage on a lowland forest bird community in southern China

To examine the relationship between forest succession after severe logging forestry practices and the composition of avian communities, we investigated how forest bird composition and guild structure change as a function of structural properties along a successional gradient, including a climax mature forest (>400 years), a rehabilitated mixed forest (50-70 years), and a disturbed Masson pine forest (70 years) of the Dinghushan Nature Reserve, Guangdong Province, China. Of a total of 51 resident species recorded, mixed forests hosted the highest numbers of individuals and species, reflecting the high species richness of both forest and non-forest species. For forest-dependent species, however, mature stands had the highest observed and estimated species richness. Of 6 habitat-use guilds identified, vertical-profile generalists and understory-birds formed the two dominant guilds, accounting for 54.0% and 38.7% of all individuals respectively. The results of canonical correspondence analysis (CCA) clearly showed that most forest-dependent species were associated with high proportions of native canopy cover and the mean density of dead trees and large trees, which are characteristic of old-growth mature forests (horizontal heterogeneity) at stand level. Accordingly, conservation efforts should focus on the specialized requirements of the most habitat-restricted species in the future, especially for understory insectivores (Babblers) and large-tree users in mature subtropical monsoon forests of southern China. Moreover, since regenerating mixed forests are very similar to mature forests in both vegetation structure and bird community composition, we recommend that logging cycles (>50 years) be increased to a minimum of 50 years in southern China, so that a balance between economic and ecological interest can be reestablished.     

Tree microhabitat structures as indicators of biodiversity in Douglas-fir forests of different stand ages and management histories in the Pacific Northwest,U.S.A.

The importance of structural complexity in forest ecosystems for ecosystem diversity has been widely acknowledged. Tree microhabitat structures as indicators of biodiversity, however, have only seldom been the focus of diversity research although their occurrence is highly correlated with the abundance of forest species and ecosystem functions. In this study, microhabitat structures in Douglas-fir (Pseudotsuga menziesii) forests were defined and their frequency and abundance in natural stands and stands of varying active management histories and stand ages was compared. Indicator microhabitat structures for natural forests were determined and the relationship of the abundance of microhabitat structures with tree diameter of Douglas-fir trees was analysed.     

Bird communities in hemiboreal old-growth forests: The roles of food supply, stand structure, and site type

Key factors causing the difference of wildlife populations in natural and managed forests are an important field of ecosystem and biodiversity research. To explore the factors contributing to bird-community features in the poorly studied European natural hemiboreal forests, we carried out a comparative study in old-growth and mature stands of five site types in Estonia. The mature stands were of clear-cut origin and managed for timber production. Old-growth hosted both more diverse and more abundant bird communities than mature stands, which does not support the putative ‘old-growth syndrome’ (high diversity at a low density) described previously in temperate Europe. Site-type specificity of bird communities was also more pronounced in old-growth, indicating a timber-harvesting induced process of biotic homogenization. In particular, natural swamp forests had characteristic bird species and those communities may be additionally sensitive to artificial drainage. In terms of invertebrate food supply, the availability of snails, rather than of insects, was related to bird-community characteristics; however, the influence of snails was due to one snail-poor forest type (Vaccinium type pine stands), not management. The abundance of coarse woody debris was the main structural feature affecting bird communities; tree-size variation was additionally important for species richness. A significant unexplained ‘old-growth’ effect remained even after the variables describing food supply and stand structure were taken into account. Our results imply the distinct importance of old-growth of different site types for hemiboreal bird communities. However, we did not obtain any evidence of different key factors structuring the bird communities in old-growth and mature stands.     

Stand carbon stocks and soil carbon and nitrogen storage for riparian and upland forests of boreal lakes in northeastern Ontario

The establishment of shoreline reserves (buffer strips) has guided riparian forest management in Ontario for many years. A riparian area is defined as the transitional zone between the aquatic and terrestrial environments and therefore is also known as the aquatic/terrestrial ecotone. While many functions of riparian forests have been recognized and well studied, less is known about their potential to sequester C and whether this potential differs from other areas in the boreal forest landscape. Increased harvesting pressure due to decreased wood supply in Ontario and debate about the effectiveness of the current reserve guidelines has resulted in a renewed interest in harvesting riparian forests. In this study riparian and upslope forest C and soil C and N storage were quantified for 21 lakes shorelines at the Esker Lakes Research Area, a boreal forest ecosystem in northeastern Ontario, Canada. Objectives were to compare the C and N storage potential of riparian forests with those of adjacent upland forests, and to examine the potential impacts of harvesting on C stocks in riparian zones of the boreal forest.Riparian forests did not differ from upslope stands in terms of total aboveground overstory C storage although there were significant differences in stocking density and species composition. However, a greater proportion of total site C in riparian areas was stored in the overstory tree layer (>5 cm dbh) compared to upslope areas. Forest floor layers were deeper and stored more C and N in riparian forest stands in comparison to upslope stands. In contrast, mineral soil in upslope stands had greater C and N storage than mineral soil horizons within the riparian forest. As a result, the riparian organic horizons comprise a larger percentage of the overall soil storage of C and N than upslope layers. Currently practiced full-tree harvesting would result in a removal of approximately 76% of total aboveground C (17% of the ecosystem C) in upslope stands compared to 98% of total aboveground C (35% of the ecosystem C) in riparian forests. Selective or modified harvesting in riparian zones could decrease C removal to levels equal to that obtained by full-tree harvesting in upslope areas.