Boreal lichen woodlands: A possible negative feedback to climate change in eastern North America

Because of successive forest fires, closed-canopy black spruce forests are susceptible to a shift towards open lichen-spruce woodlands in parts of the boreal forest of eastern North America. The shift from dark black spruce canopies to pale lichen ground cover offers a dramatic contrast in reflectance that may compensate for the CO₂ emissions from forest fires in terms of radiative forcing. We have therefore looked at the climate change feedback that would result from the generation of lichen woodlands through changes in albedo and in stored carbon. Using albedo estimates based on MODIS imagery and incoming solar radiation for the period between 2000 and 2008 along with forest biomass estimates for eastern Canada, we have estimated that net radiative forcing for the conversion from closed-canopy coniferous forests to open lichen woodlands would be about −0.12 nW m⁻² ha⁻¹, and would therefore generate a cooling effect in the atmosphere. Based on current estimates of area in open lichen woodlands within the closed-canopy black spruce-moss forests of eastern Canada, we estimate that a current net forcing of −0.094 mW m⁻² has already arisen from such conversions. As projections of future climate have been linked to increased probability of forest fires, the generation of open lichen woodlands provides a possible negative feedback to climate change. Results also suggest that carbon sequestration through the afforestation of boreal lichen woodlands may not provide a climate change mitigation benefit.     

Regional diversity of mycetophilids (Diptera: Sciaroidea) in Scandinavian oak-dominated forests

Mycetophilids is a species-rich insect group for which the ecological requirements in temperate forests are poorly understood. This study of mycetophilids was based on trap samples from 15 oak-dominated sites in the boreonemoral zone of southern Sweden. Species richness and composition were analysed in relation to environmental variables at a local and at larger scales (multiple regression), and compared to results from similar studies in spruce-dominated sites in the boreal zone of Norway (PCA and two-sample t tests). Regressions showing a dominance of regional factors over local in-site variables agree with species-richness models assuming that local communities most often are unsaturated. Precipitation (inter-correlated with elevation) was the strongest factor for explaining the variation in species-richness, which is consistent with previous results indicating that mycetophilids are disfavoured by drought. In addition to precipitation, the area of mixed forest with high biodiversity values (woodland key habitats and protected areas) was a positive factor for species-richness, probably because such habitats combine elements of both coniferous and deciduous forests. PCA ordination revealed a clear separation of the species composition between boreal and boreonemoral forests. Species-richness in boreal forest was significantly higher than in boreonemoral forest, indicating a preference for boreal habitats in many of the species. For mycetophilids and other drought-sensitive insects, it is suggested that (partial) cutting in some dense successional oak stands should be avoided, and that some invading spruces should be tolerated.     

Interannual variation in net ecosystem productivity of Canadian forests as affected by regional weather patterns – A Fluxnet-Canada synthesis

Large-scale weather events such as the El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and droughts are known to cause substantial interannual variation in the net ecosystem productivity (NEP) of tropical, temperate and boreal forests. Hypotheses for the impacts on NEP of changes in air temperature (T_a) and precipitation associated with these events were tested at diurnal, seasonal and annual time scales using the terrestrial ecosystem model ecosys with measurements of CO₂ and energy exchange from 1998 to 2006 at eddy covariance (EC) flux towers along a transcontinental transect of forest stands in the Fluxnet-Canada Research Network (FCRN).¹ These tests were supported at seasonal time scales by remotely-sensed vegetation indices, and at decadal time scales by wood growth increments from tree-ring and inventory studies. Collectively, results from this testing indicate that large-scale weather events during the study period caused spatially coherent changes in NEP, although these changes may vary with climate zone, species and topography. High T_a episodes, such as occurred with greater frequency during ENSO/PDO events, adversely affected diurnal CO₂ exchange of temperate and boreal conifers, but had little effect on that of a boreal deciduous forest. These contrasting responses of CO₂ exchange to T_a were attributed in the model to greater xylem resistance to water uptake in coniferous vs. deciduous trees. Sustained warming such as occurred during ENSO/PDO events extended the period of net C uptake and thus raised annual NEP at boreal coniferous and deciduous sites, but did not do so at a temperate coniferous site where annual NEP was reduced. However the rise in NEP of boreal conifers with warming was partially offset by the adverse effects of high T_a on diurnal CO₂ exchange, so that the rise in NEP with warming remained smaller than that at a boreal deciduous site. A 3-year drought during the study period adversely affected annual NEP of well-drained boreal deciduous forests but did not affect that of poorly-drained boreal conifers. This lack of effect was attributed in the model to low coniferous evapotranspiration rates and to subsurface water recharge. Drought effects on NEP were therefore largely determined by topography. These contrasting responses of different forest stands to warming and drought indicate divergent changes in forest growth with interannual changes in weather. Such divergent changes are consistent with the complex changes in forest NDVI and net C uptake observed over time in several large-scale remote-sensing studies.     

Diversity and abundance of earthworms across an agricultural land-use intensity gradient

Understanding how communities of important soil invertebrates vary with land use may lead to the development of more sustainable land-use strategies. We assessed the abundance and species composition of earthworm communities across six replicated long-term experimental ecosystems that span a gradient in agricultural land-use intensity. The experimental systems include a conventional row-crop agricultural system, two lower-intensity row-crop systems (no-till and tilled organic input), an early successional old-field system, a 40–60 years old coniferous forest plantation, and an old-growth deciduous forest system. Earthworm populations varied among systems; they were lowest in the most intensively managed row-crop system (107 m⁻²) and coniferous forest (160 m⁻²); intermediate in the old-field (273 m⁻²), no-till (328 m⁻²) and tilled organic (344 m⁻²) cropping systems; and highest in the old-growth deciduous forest system (701 m⁻²). Juvenile Aporrectodea species were the most common earthworms encountered in intensively managed systems; other species made up a larger proportion of the community in less intensively managed systems. Earthworm community biomass and species richness also varied and were lowest in the conventional row-crop system and greatest in the old-growth forest system. These results suggest that both land-use intensity and land-use type are strong drivers of the abundance and composition of earthworm communities in agricultural ecosystems.     

Forest health monitoring in Canada: How healthy is the boreal forest?

The Canadian boreal forest covers 299.2 Mha which is two-thirds of Canada's forest and runs in a continuous belt from Newfoundland north and west to the Yukon. The major species are spruce, pines, balsam fir, white birch and trembling aspen often occurring in extensive monocultures. Wildfire is the driving successional force in the boreal forest and has remained so despite fire suppression activities and extensive harvesting. Insects and diseases also cause extensive damage. In order to ensure the sustainability of forests, it is necessary for the forest manager to know the condition of the health of these forests. The CFS established in 1984 the Acid Rain National Early Warning System in order to monitor the health of the forests. National results show that mortality is generally in the normal range of 1–3% and is caused by known stresses; insects, diseases and abiotic damage. No signs of pollution damage have been yet been detected in boreal forests by the system. An early warning system to detect and monitor conditions remains an essential part of our commitment to the sustainability of Canada's forests.     

Decreases in soil moisture and organic matter quality suppress microbial decomposition following a boreal forest fire

Climate warming is projected to increase the frequency and severity of wildfires in boreal forests, and increased wildfire activity may alter the large soil carbon (C) stocks in boreal forests. Changes in boreal soil C stocks that result from increased wildfire activity will be regulated in part by the response of microbial decomposition to fire, but post-fire changes in microbial decomposition are poorly understood. Here, we investigate the response of microbial decomposition to a boreal forest fire in interior Alaska and test the mechanisms that control post-fire changes in microbial decomposition. We used a reciprocal transplant between a recently burned boreal forest stand and a late successional boreal forest stand to test how post-fire changes in abiotic conditions, soil organic matter (SOM) composition, and soil microbial communities influence microbial decomposition. We found that SOM decomposing at the burned site lost 30.9% less mass over two years than SOM decomposing at the unburned site, indicating that post-fire changes in abiotic conditions suppress microbial decomposition. Our results suggest that moisture availability is one abiotic factor that constrains microbial decomposition in recently burned forests. In addition, we observed that burned SOM decomposed more slowly than unburned SOM, but the exact nature of SOM changes in the recently burned stand are unclear. Finally, we found no evidence that post-fire changes in soil microbial community composition significantly affect decomposition. Taken together, our study has demonstrated that boreal forest fires can suppress microbial decomposition due to post-fire changes in abiotic factors and the composition of SOM. Models that predict the consequences of increased wildfires for C storage in boreal forests may increase their predictive power by incorporating the observed negative response of microbial decomposition to boreal wildfires.     

Dissecting habitat loss and fragmentation effects following logging in boreal forest: Conservation perspectives from landscape simulations

Habitat loss and fragmentation are recognized as major threats to biodiversity. Their respective effects, however, are sometimes not well distinguished, even though habitat loss is recognized as the most important source of variation affecting species abundance and richness at the landscape scale. As ‘habitat’ is a species-specific concept (based on species perception of its environment), habitat loss and fragmentation studies should be conducted on a species-specific basis. We here assessed the influence of habitat loss and fragmentation in the context of a boreal forest considering forest clearcutting as an anthropogenic disturbance inducing mature forest loss and fragmentation that has a potential impact on wildlife. Using 16 simulated patterns of mature forest loss and fragmentation and three natural landscapes as replicates, we assessed the respective influence of forest loss and fragmentation on the abundance of 10 bird species common in the boreal forest of eastern Canada. Species–habitat relationships were modeled through habitat use models that were utilized to predict abundance of the 10 species within each combination of loss and fragmentation patterns (3 landscapes × 16 patterns). We used three-way ANOVAs to assess the effects of mature forest loss, fragmentation and replicates (random effect) on species abundance. Our results indicated that: (1) variation in species abundance mostly depended on mature forest loss, followed by static landscape attributes other than cutovers (e.g. streams, lakes, roads) and finally by fragmentation and (2) responses to mature forest loss and fragmentation differed among species, not necessary in relation to the successional status but in relation to their perception of their environment. Decreasing detrimental effects of mature forest loss through conservation of large continuous patches of forest may be suitable to maintain abundances of mature forest bird species. Our results highlight that studies aiming to quantify effects of habitat loss and fragmentation on wildlife should be conducted on a species-specific basis and use several landscape replicates to avoid potentially biased results.     

Indicator species among resident forest birds - A cross-regional evaluation in northern Europe

In European forests, plants, fungi and invertebrates have been proposed as indicator species for assessing conservation value at the stand scale. To cover larger spatial scales, wide-ranging vertebrates could be added to that set of species. For resident forest birds, we (1) explored whether the occurrence of some species could be used to indicate high species richness and abundances, and (2) compared the results among four regions in the Baltic Sea drainage basin with a common species pool but different forest management intensities and varying proportions of deciduous and coniferous trees (south-central and southern Sweden, south-central Lithuania and northeastern Poland). Assemblages of deciduous forest birds in 100-ha landscape units were generally nested, suggesting that species richness within that group may be predicted based on the presence of a few species. Birds of coniferous forests, however, showed poorer conformity to nestedness in Sweden. Specialised species such as the middle spotted (Dendrocopos medius) and lesser spotted woodpeckers (D. minor) in deciduous forest and the three-toed woodpecker (Picoides tridactylus) in coniferous forest generally figured among the best indicators. In deciduous forest, there was high cross-regional consistency in the identity of the best indicators. Moreover, the sites where the best indicator was present also harboured higher relative abundances of most background species. For coniferous forest, however, such a relationship was not found. We conclude that an indicator species approach may be useful for resident birds of deciduous forests in hemiboreal Europe, emphasising that it should constitute one of many complementary tools for conservation management.     

Persistent effects of fire-induced vegetation change on energy partitioning and evapotranspiration in ponderosa pine forests

We compared energy fluxes between a site converted from ponderosa pine (Pinus ponderosa) forest to sparse grassland by a severe wildfire 10 years ago and a nearby, unburned forest. We used eddy covariance and associated instruments to measure total radiation, net radiation, albedo, and fluxes of energy into latent heat, sensible heat, and the soil. Total radiation, vapor pressure deficit, and air temperature were similar for each site. Compared to the unburned site, net radiation efficiency (net radiation/total radiation) was 30% lower and albedo 30% higher at the burned site. The magnitude of sensible and latent heats varied seasonally at both sites. Sensible heat was the major component of the energy balance in cold or dry seasons, whereas latent heat was the major component in the warm and wet season. Soil heat flux was the smallest in magnitude of the measured energy fluxes. Compared with the unburned forest, the burn-created grassland generally had lower sensible and latent heats, but greater soil heat flux for both soil cooling in winter and warming in summer. The grassland had similar maximum air temperature as the forest, and warmer surface soil temperature during the summer. Thus, the lower albedo and greater sensible heat of the forest did not produce a warmer site compared with the grassland, apparently because of the cooling effect of greater latent heat in the forest. Our results suggest only small changes in site air temperature, but larger changes in site surface soil temperature by shifts from forest to grassland caused by severe fire in northern Arizona ponderosa pine forests.     

Above-Ground Sulfur Cycling in Adjacent Coniferous and Deciduous Forests and Watershed Sulfur Retention in the Georgia Piedmont,U.S.A.

Atmospheric deposition and above-ground cycling of sulfur (S) were evaluated in adjacent deciduous and coniferous forests at the Panola Mountain Research Watershed (PMRW), Georgia, U.S.A. Total atmospheric S deposition (wet plus dry) was 12.9 and 12.7 kg ha-¹ yr-¹ for the deciduous and coniferous forests, respectively, from October 1987 through November 1989. Dry deposition contributes more than 40% to the total atmospheric S deposition, and SO₂ is the major source (～55%) of total dry S deposition. Dry deposition to these canopies is similar to regional estimates suggesting that 60-km proximity to emission sources does not noticeably impact dry deposition at PMRW. Below-canopy S fluxes (throughfall plus stemflow) in each forest are 37% higher annually in the deciduous forest than in the coniferous forest. An excess in below-canopy S flux in the deciduous forest is attributed to leaching and higher dry deposition than in the coniferous forest. Total S deposition to the forest floor by throughfall, stemflow and litterfall was 2.4 and 2.8 times higher in the deciduous and coniferous forests, respectively, than annual S growth requirement for foliage and wood. Although S deposition exceeds growth requirement, more than 95% of the total atmospheric S deposition was retained by the watershed in 1988 and 1989. The S retention at PMRW is primarily due to SO₄ ²- adsorption by iron oxides and hydroxides in watershed soils. The S content in white oak and loblolly pine boles have increased more than 200% in the last 20 yr, possibly reflecting increases in emissions.     

A simple retrieval of ground albedo and vegetation absorptance from MODIS satellite data for parameterisation of global Land-Surface Models

The task of parameterising global Land-Surface Models (LSMs) is rendered difficult by both the limited number of parameters that can be retrieved from eddy-covariance fluxes and the requirement for some physical processes to be modelled in a spatially explicit manner. Fortunately, some of the important biophysical parameters influencing energy exchange can be usefully constrained by satellite measurements of surface reflectance. In this study, we retrieve ground (soil) albedo and vegetation absorptance from the Moderate Resolution Imaging Spectroradiometer (MODIS) 1-arcdegree albedo product. This information is used to parameterise a revised global simulation of carbon, water and energy exchange at the land-surface. The new biophysical parameters produce significant modifications (5–30%) to predicted net radiation and sensible heat exchange, particularly for the northern sub-tropics and the boreal and northern tundra zones. We infer systematic differences in vegetation absorptance between 5 plant functional types (broadleaf forest, needleleaf forest, C₃ grass, C₄ grass and shrubland). The dispersion in values is fairly moderate within any given plant functional type (PFT), suggesting that a small number of PFTs is sufficient for setting albedo parameters within a global LSM.     

The relationships among microbial parameters and the rate of organic matter mineralization in forest soils,as influenced by forest type

Vegetation type influences the rate of accumulation and mineralization of organic matter in forest soil, mainly through its effect on soil microorganisms. We investigated the relationships among forest types and microbial biomass C (MBC), basal respiration (R_B), substrate-induced respiration (R_S), N mineralization (N_min), specific growth rate μ, microbial eco-physiology and activities of seven hydrolytic enzymes, in samples taken from 25 stands on acidic soils and one stand on limestone, covering typical types of coniferous and deciduous forests in Central Europe. Soils under deciduous trees were less acidic than soils of coniferous forests, which led to increased mineralizing activities R_B and N_min, and a higher proportion of active microbial biomass (R_S/MBC) in the Of horizon. This resulted in more extractable organic C (0.5 M K₂SO₄) in soils of deciduous forests and a higher accumulation of soil organic matter (SOM) in coniferous forest soil. No effect of forest type on the microbial properties was detected in the Oh horizon and in the 0–10 cm layer. The microbial quotient (MBC/C_org), reflecting the quality of organic matter used for microbial growth, was higher in deciduous forests in all three layers. The metabolic quotient qCO₂ (R_B/MBC) and the specific growth rate μ, estimated using respiration growth curves, did not differ in soils of both forest types. Our results showed that the quality of SOM in coniferous forests supported microorganisms with higher activities of β-glucosidase, cellobiosidase and β-xylosidase, which suggested the key importance of fungi in these soils. Processes mediated by bacteria were probably more important in deciduous forest soils with higher activities of arylsulphatase and urease. The results from the stand on limestone showed that pH had a positive effect on microbial biomass and SOM mineralization.     

龙门山断裂带主要森林类型凋落物累积量及其持水特性

采用野外实地调查与室内控制浸提相结合的方法,对龙门山断裂带常绿阔叶林、落叶阔叶林、针阔混交林、常绿针叶林4种森林类型的凋落物储量、持水量、吸水速率进行了研究。结果发现,不同森林类型凋落物总储量大小顺序为:常绿针叶林(8.26t/hm2)落叶阔叶林(6.80t/hm2)针阔混交林(5.52t/hm2)常绿阔叶林(4.61t/hm2),且未分解层累积量所占比例均小于半分解层。不同森林类型不同分解程度凋落物的持水量和持水率与浸泡时间均呈对数关系,其吸水速率与浸泡时间呈幂函数关系。研究区4种森林类型半分解层凋落物的持水能力均强于分解层,而落叶阔叶林和针阔混交林持水能力较强,其次是常绿针叶林,常绿阔叶林最低。研究表明,在该区森林植被恢复和重建过程中,应充分考虑半分解层凋落物对水土保持的作用,且宜优选落叶阔叶林和针阔混交林模式进行森林植被恢复。     

Nematode assemblages indicate soil restoration on colliery spoils afforested by planting different tree species and by natural succession

Soil nematodes were studied in 28 afforested sites on clay colliery spoil from opencast mining in the Czech Republic. The afforestations had four replicate sites and were represented by 20–33-year-old plantations of oak, alder, linden, spruce, larch, pine, and sites left to natural succession. The total abundance of nematodes in deciduous plantations plus natural successions was 1156 × 10³ ind/m² and in coniferous plantations 1236 × 10³ ind/m². The abundance of plant parasites and omnivores was significantly greater in deciduous than in coniferous plantations. The abundance of root–fungal feeders dominated by Filenchus was greater in spruce and pine plantations than in deciduous plantations. Bacterivorous Plectus predominated in larch plantations. Nematode assemblages in deciduous plantations had significantly greater numbers of species and genera, H’gen, MI, ΣMI, EI and SI values, and greater proportions of omnivores plus predators to other trophic groups than the assemblages in coniferous plantations. The nematode fauna indicated most advanced soil restoration on spoils under oak and alder plantations, intermediate under linden and spruce, and least under pine and larch. Nevertheless, some nematodes typical for developed forests were either found in low population densities (e.g. Teratocephalus) or were missing (e.g. Malenchus).     

Mid-infrared spectroscopy for topsoil layer identification according to litter type and decompositional stage demonstrated on a large sample set of Austrian forest soils

When forest soils are investigated, the identification of litter and soil layers is a key step. Mid-infrared spectroscopy seems to be promising for this due to its capability to provide fingerprint information. In this study, a large data set of mid-infrared spectra of different forest soils (L, FH and Ah horizons of coniferous, mixed and deciduous forests) was available together with general analyses data (among others organic carbon, total nitrogen and carbonate contents). This set was used for devising models for the identification of different soil layers and to follow the characteristics of different forest types in the different layers. Canonical discriminant functions were calculated using nine mid-infrared bands occurring in both organic layers and mineral soil layers. The discriminant analysis of the topsoil layers showed that aliphatic mid-infrared bands dominated the first function and yielded a clear separation of mineral and organic layers. Further, this analysis reflected the higher chemical diversity in the organic layers visible by a high scattering of the calculated data points. Two tests with two separate data sets showed a reliable and reproducible performance of the model. Separations of forest types were best possible in the organic layers, in which the deciduous forests were separated best from mixed and coniferous forests. Also for these discriminations, aliphatic bands were dominating. Advanced degradation of soil organic matter resulted in small distances of equidistant forest-type group-centers in the 5-10 cm layers of the mineral soils. Dominating molecular moieties in the discriminant functions in these layers were carbonates and aliphatic bands. The applied methodology suggests mid-infrared spectroscopy as an appropriate tool for soil layer identification, allowing for unequivocal discrimination between organic and mineral soil layers. Discriminations of forest types delivered information about dominating mid-infrared bands in the single layers and allowed conclusions about functional groups dominating these differences.     

Estimating energy balance fluxes above a boreal forest from radiometric temperature observations

The great areal extent of boreal forests confers these ecosystems potential to impact on the global surface-atmosphere energy exchange. A modelling approach, based on a simplified two-source energy balance model, was proposed to estimate energy balance fluxes above boreal forests using thermal infrared measurements. Half-hourly data from the Solar-Induced Fluorescence Experiment, carried out in a Finnish boreal forest, was used to evaluate the performance of the model. Energy balance closure, determined by linear regression, found all fluxes to underestimate available energy by 9% (r² = 0.94). Significance in the energy balance of the heat storage in the air and in the soil terms was also analyzed. Canopy temperatures, measured by a CIMEL Electronique CE 312 radiometer, together with ancillary meteorological variables and vegetation characteristics, were used to run the model. Comparison with ground measurements showed errors lower than ±15 W m^?2 for the retrieval of net radiation, soil heat flux and storage heat flux, and about ±50 W m^?2 for the sensible and latent heat fluxes. A sensitivity analysis of the approach to typical operational uncertainties in the required inputs was conducted showing the necessity of accurate measurements of the target radiometric surface temperature.     

Addition of coarse woody debris – The early fungal succession on Picea abies logs in managed forests and reserves

Modern forestry practices have decreased the abundance of coarse woody debris (CWD), and as a result many species that depend on dead wood are now threatened. This implies a need to develop forestry practices that maintain biodiversity. We examined the conservation value of experimental spruce logs (control logs, logs placed in natural shade, and cut tree tops) for wood-inhabiting fungi in two forest stands, one nature reserve and one mature managed forest, in each of seven forest areas in northern Sweden. Here we report the initial findings of the experiment that was established in winter 2001–2002 and data were collected in 2002, 2003 and 2006. A pre-inventory of the local species composition in 2002 revealed a higher per area species richness, including red-listed species, in reserves than in managed forests. Ordination analyses of the experimental logs showed a significant effect of area, while not of stand type in 2003. ANOVA analysis showed no significant effect of stand type on species richness and abundance. In 2006, the species assemblage started to differentiate between the two stand types and forest age, forest site type (moisture), and distance to forest reserves, all explained part of the variation, whereas the amount of CWD, and species composition at the start of the experiment only showed a marginal effect.The early successional fungal community was dominated by two functional groups, humus-decayers and white-rot species, both characterized by a rapid, early colonization and fruit-body formation on the competition-free new substrate. A similar positive response to the new substrate was also observed for the mycorrhizal species in 2006. The high frequency and early appearance of humus-decayers and mycorrhizal species that do not primarily depend upon CWD for their nutrition suggest that their formation of fruiting bodies is limited by substrate availability. Thus some mycorrhizal fungi are apparently rare due to lack of suitable substrate for fruit-body formation.Evidence of dispersal-limitation was observed in 2006. Fomitopsis pinicola, an early colonizer in boreal forests, playing a key role for other wood-inhabiting organisms, colonized significantly more logs in the reserve stands compared with the managed stands. Our data demonstrate that lack of CWD strongly affects both species that depend upon wood for nutrition and species that depend upon wood for fruit-body formation. Thus some species may show an apparent rarity due to lack of suitable substrate. We conclude that creation of CWD appears to be a useful method to maintain or restore fungal diversity in boreal coniferous forests.     

The potential aboveground carbon storage of north American forests

To assess the possibility of using C offset as a method of sequestering CO₂ produced by the burning of fossil fuels, it is necessary to have accurate estimates of C reservoirs and fluxes. Recent studies have shown that estimates of C commonly used in the past are too large, and this may lead to confusion about the global C budget. Field data used in recent estimates of present C storage for the North American boreal and eastern deciduous forest biomes were reanalyzed to estimate their maximum potential C storage. The original data were collected using a stratified two-stage cluster survey sampling design. The reanalysis suggests that the boreal forest and eastern deciduous forest could sequester possibly as little as 13.4% (3.0 Pg) and 18.5% (1.5 Pg), respectively, more C than they presently store. These estimates represent the potential increase in C storage under present conditions, if the study areas were allowed to revert back into forests.     

Conservation of beetles in boreal pine forests: the effects of forest age and naturalness on species assemblages

The effort of boreal forest conservation has emphasised the preservation of old-growth forests while the role of young successional stages in maintaining biodiversity has remained largely unstudied. We compared the richness of beetle species and composition of species assemblages between managed and seminatural forests in five stages of forest succession. The sites were in boreal sub-xeric pine-dominated forests in eastern Finland. Seminatural study sites, especially the recently burned sites, were important habitats for threatened and near-threatened species. We propose that young stages of natural succession should be included in the network of protected forest areas. On the other hand, the composition of saproxylic species assemblages in seminatural forests differed from the assemblages in managed forests, indicating also the need to improve the forest management guidelines so that they better address the requirements of species protection. Regeneration methods applied should resemble or mimic the natural disturbances more closely.     

喀纳斯泰加林林下草本层地上碳密度对林火烈度的火后时间响应

为了探究林火烈度和火后时间对喀纳斯泰加林林下草本层碳密度的影响,在喀纳斯自然保护区设置火干扰样地,采用收获法进行了生物量调查。分莎草科、禾本科、豆科和其他草类4个功能群进行草本地上碳密度对林火烈度的火后时间响应研究。结果表明:喀纳斯林泰加林草本层地上碳密度的范围为0.096～0.359 t/hm²。在3个演替阶段,莎草科和禾本科对草本层地上碳密度贡献率大; 其他草类对草本层地上碳密度贡献率的范围为10.03%～40.97%; 豆科对草本层地上碳密度贡献率最小,仅在针叶阔叶林阶段中低烈度火后51～84 a的林分中其贡献率较大。喀纳斯林草生态系统大部分林分处于针叶阔叶和针叶混交林阶段,草本层地上碳密度在不同烈度的火干扰下总体趋势为:低烈度>中烈度>高烈度,表明低烈度火干扰有利于草本植物的生长。3个演替阶段草本功能群地上碳密度对林火烈度的火后时间响应并不相同,但草本层地上碳密度随着火后时间的增加总体呈减小趋势。高烈度火干扰对草本层地上碳密度的影响最大,且不利于保持或提高森林的生产力。通过清除林下凋落物将林火烈度控制在中、低烈度范围内,有利于提高草本层的碳汇功能。