High diversity of arbuscular mycorrhizal fungi in a boreal herb-rich coniferous forest

* Here, the diversity of arbuscular mycorrhizal (AM) fungi was determined in a boreal herb-rich coniferous forest in relation to environmental variables. * Root samples of five plant species (Fragaria vesca, Galeobdolon luteum, Hepatica nobilis, Oxalis acetosella and Trifolium pratense) were analysed from stands differing in age and forest management intensity. * Thirty-four Glomeromycota taxa (small-subunit ribosomal RNA gene (SSU rDNA) sequence groups) were detected from 90 root samples (911 clones), including eight new taxa. Sequence groups related to Glomus intraradices were most common (MO-G3 and MO-G13). Samples of H. nobilis were colonized by more AM fungal taxa (3.68 +/- 0.31) than those of O. acetosella (2.69 +/- 0.34), but did not differ significantly in this respect from those of F. vesca (3.15 +/- 0.38). Effects of forest management, host plant species (except above) or season on the number or composition of fungal taxa in root samples were not detected, and neither were they explained by environmental variables (vegetation, soil and light conditions). * This is the most taxon-rich habitat described to date in terms of root-colonizing Glomeromycota. The data demonstrate the importance of temperate coniferous forests as habitats for AM fungi and plants. Lack of obvious fungal community patterns suggests more complex effects of biotic and abiotic factors, and possibly no adverse effect of common forest management practices on AM fungal diversity.     

Sixty years of vegetation dynamics in a south boreal coniferous forest in southern Norway

Abstract. Vegetation data from permanent plots were collected in 1931, 1961 and 1991 in a south boreal forest 20 km north of Oslo in southern Norway. Major changes were found in the vegetation composition during those 60 years. The main changes were a reduction in the frequency of species and the frequency of joint occurrences of vascular species such as Andromeda polifolia, Calluna vulgaris, Cornus suecica, Eriophorum vaginatum, Maianthemum bifolium, Melampyrum pratense, Trientalis europaea, Vaccinium uliginosum and V. oxycoccus, and mosses, e.g. Dicranum fuscescens, Hylocomium splendens, Pleurozium schreberi, Ptilidium ciliare and Ptilium crista-castrensis. The observed changes were interpreted as being induced by internal processes e.g. notably a long-term change from paludified forest to mesic forest. In particular the growth of Picea abies seems to be a main driving force. The dominance of Picea abies and Vaccinium myrtillus appears to have rendered the conditions more unfavourable for other species. A doubling of the living stem biomass of P. abies during the last 67 yr shows that this old-growth forest has not yet reached a steady state. It was demonstrated that species such as Deschampsia flexuosa and Molinia caerulea did not increase in frequency in response to nitrogen deposition, as has occurred elsewhere in northern Europe. pH in the humus layer increased with 0.2 unit from 1961 to 1991. The results of this study indicate that protection from logging has initiated the reduction of species in the field layer and bottom layer. This study questions if monitoring of forest vegetation should be restricted to protected forests as is the practice in Scandinavia today. We recommend that also areas with some kind of selective cutting will be used for monitoring of forest vegetation.     

Bird community energetics in a boreal coniferous forest

The annual minimum energy consumption of the bird community was 2524 × 10³ kcal km⁻², of which 44% was consumed by wintering species and 73% by passerines. The daily energy consumption was in summer 14–16 × 10³ and in winter 1–2 × 10³ kcal km⁻². In spruce forests and in afforested swamps birds required approximately 0.12% of the net primary production. Their total annual energy consumption was covered by invertebrates (59%), vertebrates (2%) and vegetable matter (39%); the food derived from the ground (55%), from trees (44%) and from the air (1%). Arboreal insectivorous passerines, ground passerines and gallinaceous birds were the most important ecological guilds. Among passerines existence metabolism accounted for 73% of the annual energy consumption, extra activity for 17%, breeding activity for 1%, moult for 4% and nestlings for 4%.     

木材腐朽菌在森林生态系统中的功能

木材腐朽菌是森林生态系统的重要组成部分,在森林生态系统中起着极为重要的降解还原作用,主要包括担子菌门非褶菌目、子囊菌门盘菌纲和半知菌类的部分真菌,能全部或部分降解木材中的木质素、纤维素和半纤维素,其降解机制有3种：白色腐朽、褐色腐朽和软腐朽．木材腐朽菌与生态系统中其它生物关系密切,为很多昆虫、鸟类提供营养,有些昆虫也能使木腐菌得到传播．保护木材腐朽菌的生物多样性是保护森林生态系统、维护生态系统健康的重要因素．     

Persistence of vascular plants in a Norwegian boreal coniferous forest

Persistence, the tendency of a species to remain in its original position and not to colonize new sites, is studied for the most abundant forest vascular plants (25 species in spruce forest and 7 in pine forest) in Solhomfjell, Gjerstad, S Norway Data sets included presence/absence in 199 meso plots (1 m²) and 3184 subplots (1/16 m²), analyzed over a 5 yr interval, and a subset of 50 meso plots and 800 subplots, analyzed for six consecutive years Relationships between species variables (seedling frequency and mobility rate compiled from the literature, and cover and abundance means in the study area) are studied, and related to species optima along ecologically interpreted DCA ordination axes Vascular plant mobility may increase towards nutrient-poor sites Dominance in the boreal forest floor is mostly by clonal species Persistence was calculated for different temporal (1-5 yr) and spatial (1/16 and I m²) scales Persistence patterns in the spruce and pine forests were similar, but persistence decreased towards the xeric pine forests One main component of variation in persistence was demonstrated by PCA analyses the absolute level of persistence, which is related to seedling recruitment vs clonal growth, and within clonal species to ramet longevity, abundance, mobility, growth pattern and mode of surviving the infavourable season Minor components of variation in persistence were related to spatial scale and temporal scale Persistence characteristics were species-specific and varied little between years Numerous species characteristics were relevant to interpretation of variation in persistence, indicating a continuous, multidimensional variation in life history characteristics     

Habitat models of wood-inhabiting fungi along a decay gradient of Norway spruce logs

Information on the habitat requirements of wood-inhabiting fungi is needed to understand the factors that affect their diversity. We applied culture-free DNA extraction and 454-pyrosequencing to study the mycobiota of decaying Norway spruce (Picea abies) logs in five unmanaged boreal forests. Fungal habitat preferences in respect of wood density gradient were then estimated with generalized additive mixed models. Fungal diversity and wood density were inversely related, i.e., OTU richness generally increased as the log became increasingly decomposed. White-rot fungi (e.g., Phellinus nigrolimitatus) and members of Hyphodontia did not show a clear response to the wood-density gradient, whereas abundance of Phellinus viticola and brown-rot fungi (e.g., Fomitopsis pinicola, Antrodia serialis, Coniophora olivaceae) peaked during intermediate decay and mycorrhizal fungi (e.g., Piloderma, Tylospora, Russula) increased in the later stages. This information on fungal habitat requirements facilitates the development of management practices that preserve fungal diversity in managed forests.     

Effects of simulated N deposition on understorey vegetation of a boreal coniferous forest

1. We report the short-term effects of simulated nitrogen (N) deposition on the understorey of a boreal forest in northern Sweden. Doses of ¹⁵N double-labelled NH₄NO₃ (0·5, 12·5, 25·0 and 50·0 kg N ha^–1) were applied to 1 m² plots in the summer of 1995 and plants were harvested the following autumn.
2. No significant treatment effects were found in either above- or below-ground biomass which was distributed as follows: the ericaceous shrub Vaccinium myrtillus contributed 76%, the grass Deschampsia flexuosa 4%, and the bryophytes Dicranum majus and Pleurozium schreberi 20%.
3. The recovery of applied N in these species was 24, 27, 27 and 32% of the 0·5, 12·5, 25·0 and 50·0 kg N ha^–1 applications, respectively, and thus the recovery increased with the N dose.
4. In the 0·5 kg N ha^–1 treated plots, the highest concentrations of fertilizer-derived ¹⁵N were found in the bryophytes, while in plots given the three higher N applications, leaves of D . flexuosa had the highest concentrations.
5. N application resulted in elevated concentrations of free amino acid N, which indicate increased storage of N in plant tissues. Furthermore, the N application resulted in increased damage to V . myrtillus by natural enemies. The severity of disease caused by two foliar parasitic fungi showed a clear numerical response to N treatment, as did the amount of herbivory as a result of Lepidoptera larvae.     

Sulfur speciation and distribution in soils and aboveground biomass of a boreal coniferous forest

Major sulfur pools are quantified in soils and aboveground biomass of a coniferous boreal forest. Total ecosystem S averages 1395 kg·ha⁻¹ of which 98% is found in the soil, with 89% being in the mineral horizons. Organic S dominates in soil, tree parts (trunks, branches + foliage, roots) and litterfall, ranging from 77 to 99% of total S concentration. Carbon-bonded S, ester sulfate and SO₄-S in soil profiles range respectively from 51–68%, 29–37% and 1–14% of total S concentrations and account respectively for 57, 33 and 10% of total S on an areal basis. Adsorbed SO₄ accounts for 82% of total SO₄, and can be predicted from Al bound to organic matter, amorphous Al and pH (r^{2 = 0.81}). There is a strong relationship between % carbon and carbon-bonded S in 4 of the 5 soil horizons studied which represent over 95% of the total soil organic matter, whereas ester sulfate is related to % carbon in 3 soil horizons representing only 37% of the soil organic matter. An analysis of atmospheric S loading and S data for 10 forested sites in Europe and North America suggests that the size of the organic S pool in forested systems is independent of atmospheric loading.     

Crustose lichens as indicators of forest continuity in boreal coniferous forests

The crustose lichen flora of fifteen areas in boreal coniferous forests from southern Sweden to Lapland was surveyed. Many of these areas are included in a national programme for monitoring long-term environmental change, the PMK programme. In all 190 species were recorded, 129 of them occurring on bark of conifers and lignum. Some species were found exclusively in forests with a long continuity. By using ordination and hierarchical classifications further species with similar habitat requirements were identified. An Indicator Species Index of Forest Continuity (ISIFC) was designed. Only two of the twenty index species occur on deciduous trees. The ISIFC was highly correlated with forest continuity and also with occurrence of species listed as threatened. Correlations with macroclimatic variables are considered sampling artifacts, and microclimatic factors are suggested to be of primary importance for species occurring in forests with a long continuity.     

Climate change implications of shifting forest management strategy in a boreal forest ecosystem of Norway

Empirical models alongside remotely sensed and station measured meteorological observations are employed to investigate both the local and global direct climate change impacts of alternative forest management strategies within a boreal ecosystem of eastern Norway. Stand‐level analysis is firstly executed to attribute differences in daily, seasonal, and annual mean surface temperatures to differences in surface intrinsic biophysical properties across conifer, deciduous, and clear‐cut sites. Relative to a conifer site, a slight local cooling of ?0.13 °C at a deciduous site and ?0.25 °C at a clear‐cut site were observed over a 6‐year period, which were mostly attributed to a higher albedo throughout the year. When monthly mean albedo trajectories over the entire managed forest landscape were taken into consideration, we found that strategies promoting natural regeneration of coniferous sites with native deciduous species led to substantial global direct climate cooling benefits relative to those maintaining current silviculture regimes – despite predicted long‐term regional warming feedbacks and a reduced albedo in spring and autumn months. The magnitude and duration of the cooling benefit depended largely on whether management strategies jointly promoted an enhanced material supply over business‐as‐usual levels. Expressed in terms of an equivalent CO₂ emission pulse at the start of the simulation, the net climate response at the end of the 21st century spanned ?8 to ?159 Tg‐CO₂‐eq., depending on whether near‐term harvest levels increased or followed current trends, respectively. This magnitude equates to approximately ?20 to ?300% of Norway's annual domestic (production) emission impact. Our analysis supports the assertion that a carbon‐only focus in the design and implementation of forest management policy in boreal and other climatically similar regions can be counterproductive – and at best – suboptimal if boreal forests are to be used as a tool to mitigate global warming.     

Assemblages of wood-inhabiting fungi along the gradients of succession and naturalness in boreal pine-dominated forests in Fennoscandia

In boreal forests, the level of naturalness and the stage of succession explain most of the variation in forest structure within a particular forest type. Thus, these two factors should also have a major effect on species assemblages in forests, at least on species groups associated with wood. The present study is the first attempt to analyze empirically the simultaneous effects of forest succession and naturalness on wood-inhabiting fungi, a taxonomic group of special ecological importance. The study area was situated in eastern Finland, middle boreal zone. A total of 41 study plots were established in Pinus sylvestris forests representing three levels of forest naturalness: natural, seminatural and intensively managed forests. Five stages of succession were distinguished according to the age of the dominating tree layer (<10, 40, 70, 110, and >150 yr old), except in managed forests where only four stages were available. A total of 5328 records of 195 species of fungi were made. The first, open stage of succession was clearly the most species-rich period of succession in all levels of forest naturalness. In natural and seminatural forests, the first stage of succession was also very distinctive in its fungal composition, and thus of special value in protecting biodiversity in boreal forests. In the succession following the first stage, the level of naturalness had more effect on assemblages of fungi than did the stage of succession. Intensive forest management affects threatened species particularly. In conclusion, natural young stages of succession should also be included in the network of boreal forest reserves.     

Successional development of wood-inhabiting fungi associated with dominant tree species in a natural temperate floodplain forest

Fungi play a crucial role in dead wood decay, being the major decomposers of wood and affecting microbiota associated with dead wood. We sampled dead wood from five deciduous tree species over more than forty years of decay in a natural European floodplain forest with high tree species diversity. While the assembly of dead wood fungal communities shows a high level of stochasticity, it also indicates clear successional patterns, with fungal taxa either specific for early or late stages of wood decay. No clear patterns of fungal biomass content over time were observed. Out of 220 major fungal operational taxonomic units, less than 8% were associated with a single tree species, most of them with Quercus robur. Tree species and wood chemistry, particularly pH, were the most important drivers of fungal community composition. This study highlights the importance of dead wood and tree species diversity for preserving the biodiversity of fungi.     

大兴安岭林区火烧迹地木腐菌主要类群的初步研究

对大兴安岭林区火烧迹地的17种主要木腐菌进行了报道,并就它们的生态习性和生态功能进行探讨．通过对火烧林分和非过火林分主要木腐菌类群变化的研究,确定在火烧迹地森林生态系统演替过程中的先锋菌物主要有8种,常见菌4种,以及在寒温带针叶林生态系统中的珍稀和濒危的木腐菌3种,并探讨了珍稀或濒危菌物的保护对策．     

Small scale pH buffering in organic horizons of two boreal coniferous forest stands

Factors behind the small-scale variaton of pH were examined in O horizons (humus layers) developed under two stands of Picea abies (L.) Karst. (Site F and K) by combining data on the composition of the cation exchange complex with data from titrations of corresponding H⁺-saturated samples. Cations extractable in 0.5 M CuCl₂ (S=cmol_c kg^–1 [2Ca+2Mg+2Mn+K+Na]), aluminium extractable in 1.0 M KCl (Al_e=cmol_c kg^–1 [3Al]) and in 0.5 M CuCl₂ (Al_org=cmol_c kg^–1 [3Al]), as well as pH measured in 0.01 M CaCl₂ (pH_Ca) were analysed in one-cm-layers of 13 O horizon cores at each site. Composite samples representing each of the one-cm-layers at each site, as well as samples with two different levels of Al saturation at Site K, were H⁺ saturated and titrated with NaOH to chosen end points of pH_Ca=4.0 and 5.5 in a 0.01 M CaCl₂ ionic medium. The Acid Neutralisation Capacity (ANC) was estimated as the amount of base needed to increase pH_Ca of the composite H⁺-saturated samples to the mean pH_Ca of the corresponding natural samples. The ANC was found to be similar in magnitude or higher than the amount of sites binding S+Al_e, which suggests that 1.0 M KCl exchangeable Al ions are nonacidic in acid O horizons. The relative contribution from i) the capacity of acidic functional groups, ii) their acid strength and iii) their degree of neutralisation to differences in pH_Ca between sites, among cm-layers and between samples with different levels of Al saturation were estimated from titration curves adjusted to hold two out of three factors (i, ii and iii) to be constant. The degree of neutralisation explained most of the differences in pH_Ca between the two sites, as well as between samples with different levels of Al saturation at Site K. The pH_Ca decrease by depth at site F was, however, partly explained by an increasing acid strength. The study emphasizes the importance of examining not only changes in the degree of neutralisation, but also changes in the acid strength and the capacity of buffering functional groups before conclusions about causes behind acidification processes can be made. Difficulties of accurately estimating the degree of neutralisation (base saturation) of acidic functional groups from the composition of adsorbed cations, owing to the unknown acidity of adsorbed Al, was also demonstrated.     

Dynamics of understory vegetation in an old-growth boreal coniferous forest, 1988–1993

Abstract. Understorey vegetation changes in a South Norwegian old-growth coniferous forest were studied between 1988 and 1993 in 200 1-m² vegetation plots. Our aims were to quantify the amount of between-year compositional change, and to elaborate the environmental basis for long-term vegetation change, including the previously identified gradient structure with a major gradient related to topography (and soil nutrient status and soil depth) and a minor gradient reflecting paludification and canopy coverage. Species richness (yearly mean and cumulative species number) and change in species richness differed between vascular plants and cryptogams, and between forest types. The number of vascular plant species decreased in pine forest in dry years; bryophyte species number increased in spruce forest. Statistically significant vegetation change, as tested by constrained ordination (CCA) with time as the constraining variable, is demonstrated for most one-year periods and for the five-year period in most forest types. Vegetation change along identified gradients, measured as plot displacement along DCA ordination axes, also occurred. The magnitude of year-to-year vegetation change was related neither to forest type nor to one-year period; different responses to climatic and environmental change were observed in each forest type. The largest average displacement observed, from medium-rich spruce forest towards poor spruce forest, was interpreted as a long-term trend. Humus-layer pH decreased by ca. 0.25 units from 1988 to 1993, most strongly in medium-rich spruce forest where exchangeable Ca decreased and Al and Mn increased strongly. Our study supports the hypothesis that vascular plants show a long-term and broad-scale response to soil acidification. Change in bryophyte composition is linked to some very long growing-seasons. Detailed analysis of short-term vegetation dynamics enhances the interpretation of long-term changes and stresses the complementarity of univariate and multivariate methods in the analysis of vegetation change.     

Comparison of wood-inhabiting myxomycetes in subalpine and montane coniferous forests in the Yatsugatake Mountains of Central Japan

To demonstrate altitudinal gradients (and resulting temperatures) that affect myxomycete biodiversity and species composition, we statistically compared myxomycete assemblages between a subalpine coniferous forest and a montane pine forest within the region of the Yatsugatake Mountains, Nagano Prefecture, Central Japan. In summer and autumn field surveys during 2003–2010, 53 myxomycete taxa (with varieties treated as species) were observed from 639 records of fruiting bodies in the subalpine forest and 32 taxa were detected from 613 records in the montane forest. There were 20 species in common between the assemblages and the percentage similarity index was 0.400. Myxomycete biodiversity was higher in the subalpine than in the montane forest. Nine myxomycete species were statistically frequent occurrences in the subalpine forest and appeared in autumn: Lamproderma columbinum, Cribraria macrocarpa, Trichia botrytis, Physarum newtonii, Diderma ochraceum, Enteridium splendens, Elaeomyxa cerifera, Trichia verrucosa, and Colloderma oculatum. Five species were restricted to appear in the subalpine forest: Cribraria purpurea, Cribraria rufa, Cribraria ferruginea, Cribraria piriformis, and Lepidoderma tigrinum. Dead wood in the subalpine forest provided a breeding habitat for specific myxomycetes that inhabit cold areas; that is those areas having geographical features of decreasing temperature and increasing elevation, such as the temperate area of Central Japan.     

The role of fungi in biogenic weathering in boreal forest soils

In this article we discuss the possible significance of biological processes, and of fungi in particular, in weathering of minerals. We consider biological activity to be a significant driver of mineral weathering in forest ecosystems. In these environments fungi play key roles in organic matter decomposition, uptake, transfer and cycling of organic and inorganic nutrients, biogenic mineral formation, as well as transformation and accumulation of metals. The ability of lichens, mutualistic symbioses between fungi and photobionts such as algae or cyanobacteria, to weather minerals is well documented. The role of mycorrhizal fungi forming symbioses with forest trees is less well understood, but the mineral horizons of boreal forests are intensively colonised by mycorrhizal mycelia which transfer protons and organic metabolites derived from plant photosynthates to mineral surfaces, resulting in mineral dissolution and mobilisation and redistribution of anionic nutrients and metal cations. The mycorrhizal mycelia, in turn provide efficient systems for the uptake and direct transport of mobilised essential nutrients to their host plants which are large sinks. Since almost all (99.99 %) non-suberised lateral plant roots involved in nutrient uptake are covered by ectomycorrhizal fungi, most of this exchange of metabolites must take place through the plant–fungus interface. This idea is still consistent with a linear relationship between soil mineral surface area and weathering rate since the mycelia that emanate from the tree roots will have a larger area of contact with minerals if the mineral surface area is higher. Although empirical models based on bulk soil solution chemistry may fit field data, we argue that biological processes make an important contribution to mineral weathering and that a more detailed mechanistic understanding of these must be developed in order to predict responses to environmental changes and anthropogenic impact.     

Changes in the occurrence and abundance of plant species in a Norwegian boreal coniferous forest, 1988–1993

Økland, R. H. 1995. Changes in the occurrence and abundance of Dlants sDecies in a Norwegian boreal coniferois forest, 1988–1993. — Nord. J. Bot. 15: 415–438. Copenhagen. ISSN 0107–055X.
Changes in the occurrence and abundance of vascular plants, bryophytes and lichens in a S Norwegian old-growth coniferous forest were studied, using 1 m² plots divided into 16 subplots. Fifty plots were analyzed for six consecutive years, 199 plots were analyzed at the beginning and the end of the study (in 1988 and 1993). Nonparametric tests were performed for combinations of species, data type (occurrence or abundance), forest type (spruce or pine), and time period (one-year or five-year). Results are interpreted by use of species persistence data, and by detailed comparisons with European long-term and experimental studies. Abundance changes in the pine forest are probably due to short-term (between-year) climatic fluctuations, notably drought. Some effects of the observers are also seen. True five-year trends were found in the spruce forest: (1) Deschampsia flexuosa (increase), (2) several vascular plant species with preference for richer sites, notably Oxalis acetosella (decrease), and (3) most bryophyte species (increase). True trends for vascular plants are discussed in relation to deposition of airborne nitrogen and soil acidification, while the increase of bryophytes probably is due to particularly favourable growth conditions in the five-year period.     

林火干扰对北方针叶林林下植被的影响

林下植被在北方针叶林植被群落中的物种多样性最高, 且具有较高的生物量周转率和地上部分净初级生产力, 对北方针叶林生态系统功能起着重要作用。火干扰是决定北方针叶林林下植被结构与功能的一个重要景观过程。该文综述了火干扰是如何通过与地形、火前林冠组成的交互作用而影响环境资源和林下植被的。最近的研究表明: 林下植被能够影响火后树木更新苗的定植、重建速率及森林演替轨迹; 林下植被还会通过影响元素的生物地球化学过程(凋落物降解和养分循环)影响林下环境资源的数量与异质性。因此, 研究火后初期北方针叶林林下植被的动态变化, 对于物种多样性保护和森林管理具有重要意义。