Ectomycorrhizal fungal succession in mixed temperate forests

Ectomycorrhizal (ECM) fungal communities of Douglas-fir (Pseudotsuga menziesii) and paper birch (Betula papyrifera) were studied along a chronosequence of forest development after stand-replacing disturbance. Previous studies of ECM succession did not use molecular techniques for fungal identification or lacked replication, and none examined different host species. Four age classes of mixed forests were sampled: 5-, 26-, 65-, and 100-yr-old, including wildfire-origin stands from all four classes and stands of clearcut origin from the youngest two classes. Morphotyping and DNA sequences were used to identify fungi on ECM root tips. ECM fungal diversities were lower in 5-yr-old than in older stands on Douglas-fir, but were similar among age classes on paper birch. Host-specific fungi dominated in 5-yr-old stands, but host generalists were dominant in the oldest two age classes. ECM fungal community compositions were similar in 65- and 100-yr-old stands but differed among all other pairs of age classes. Within the age range studied, site-level ECM fungal diversity reached a plateau by the 26-yr-old age class, while community composition stabilized by the 65-yr-old class. Simple categories such as 'early stage', 'multi stage', and 'late stage' were insufficient to describe fungal species' successional patterns. Rather, ECM fungal succession may be best described in the context of stand development.     

Ectomycorrhizal colonization on black spruce and jack pine seedlings outplanted in reforestation sites

Six-week-old, mycorrhiza-free, bareroot jack pine and black spruce seedlings were outplanted in ten reforestation sites, situated between 45–48° latitude N and 69–74° longitude W, within the province of Quebec, representing diverse operational forestry disturbances and ecological conditions. Two months after outplanting, root systems of black spruce seedlings had fewer mycorrhizae than those of jack pine seedlings. Ectomycorrhizal colonization on black spruce seedlings did not vary significantly with the reforestation site. Percent mycorrhizal colonization for these seedlings was positively correlated with seedling dry weight while with the jack pine seedlings, mycorrhizal colonization varied significantly with the outplanting site and there was no correlation between mycorrhizal formation and seedling dry weight. Multiple linear regressions showed pH to be a determinant soil factor for mycorrhizal colonization for the two species. Drainage was the other influential factor affecting colonization of black spruce while organic matter accumulation was more important for jack pine. Inoculation with selected ectomycorrhizal fungi could be more important for black spruce than for jack pine seedlings.     

Dynamic changes in nursery and indigenous mycorrhiza ofPinus sylvestris seedlings planted out in forest and clearcuts

The community of indigenous mycorrhizal fungi on planted-out nursery seedlings of Scots pine (Pinus sylvestris L.) was surveyed for two years at two sites in Sweden. Factors studied were the effect of forests versus clearcuts on these communities, age of clearcut, planting-out in early summer versus autumn, age of planted-out seedlings and time of soil scarification. Analyses of variance and detrended correspondence analysis showed that the relative magnitude of the effects of these factors upon the composition of the ectomycorrhizal community on seedlings planted out was site > time of outplanting > forest/clearcut > age of clearcut > time of soil scarification. In general, clear-cutting had a minor effect, both qualitatively and quantitatively. Nineteen different mycorrhizal types were recorded. After two seasons, seedlings hosted an average of 1.8 indigenous mycorrhizal types and 0.95 nursery mycorrhizal types comprising 35% and 65% of the mycorrhizal roots, respectively.Piloderma croceum colonized seedlings significantly more frequently in forests than in clearcuts, whereas the reverse was found forCenococcum geophilum, and two other mycorrhizal types. However, there is a general agreement between mature coniferous forests and clearcuts as regards both the inoculum potential of dominant fungi adapted to early colonization, and the composition of these fungal species. The fungal adaptations to forests obviously resemble those conditions occurring at clearcuts.     

Little evidence for niche partitioning among ectomycorrhizal fungi on spruce seedlings planted in decayed wood versus mineral soil microsites

Ectomycorrhizal fungal (EMF) communities vary among microhabitats, supporting a dominant role for deterministic processes in EMF community assemblage. EMF communities also differ between forest and clearcut environments, responding to this disturbance in a directional manner over time by returning to the species composition of the original forest. Accordingly, we examined EMF community composition on roots of spruce seedlings planted in three different microhabitats in forest and clearcut plots: decayed wood, mineral soil adjacent to downed wood, or control mineral soil, to determine the effect of retained downed wood on EMF communities over the medium and long term. If downed and decayed wood provide refuge habitat distinct from that of mineral soil, we would expect EMF communities on seedlings in woody habitats in clearcuts to be similar to those on seedlings planted in the adjacent forest. As expected, we found EMF species richness to be higher in forests than clearcuts (P ≤ 0.01), even though soil nutrient status did not differ greatly between the two plot types (P ≥ 0.05). Communities on forest seedlings were dominated by Tylospora spp., whereas those in clearcuts were dominated by Amphinema byssoides and Thelephora terrestris. Surprisingly, while substrate conditions varied among microsites (P ≤ 0.03), especially between decayed wood and mineral soil, EMF communities were not distinctly different among microhabitats. Our data suggest that niche partitioning by substrate does not occur among EMF species on very young seedlings in high elevation spruce-fir forests. Further, dispersal limitations shape EMF community assembly in clearcuts in these forests.     

Ectomycorrhizal fungal communities in late-successional Swedish boreal forests, and their composition following wildfire

This study was conducted to evaluate the effects of wildfires on ectomycorrhizal (EM) fungal communities in Scots pine ( Pinus sylvestris ) stands. Below- and above-ground communities were analysed in terms of species richness and evenness by examining mycorrhizas and sporocarps in a chronosequence of burned stands in comparison with adjacent unburned late-successional stands. The internal transcribed spacer (ITS)-region (rDNA) of mycobionts from single mycorrhizas was digested with three restriction enzymes and compared with an ITS–restriction fragment length polymorphism (RFLP) reference database of EM sporocarps. Spatial variation seemed to be more prominent than the effects of fire on the EM fungal species composition. Most of the common species tended to be found in all sites, suggesting that EM fungal communities show a high degree of continuity following low-intensity wildfires. Species richness was not affected by fire, whereas the evenness of species distributions of mycorrhizas was lower in the burned stands. The diversity of EM fungi was relatively high considering that there were only three EM tree species present in the stands. In total, 135 EM taxa were identified on the basis of their RFLP patterns; 66 species were recorded as sporocarps, but only 11 of these were also recorded as mycorrhizas. The species composition of the below-ground community of EM fungi did not reflect that of the sporocarps produced. EM fungal species present in our ITS–RFLP reference database accounted for 54–99% of the total sporocarp production in the stands, but only 0–32% of the mycorrhizal abundance.     

Ectomycorrhizal fungal community of naturally regenerated European larch (Larix decidua) seedlings

An investigation was undertaken to assess the community structure of ectomycorrhizal (ECM) fungi on naturally regenerating European larch (Larix decidua Mill.) seedlings grown under forest conditions. The sites examined were in two managed monoculture larch forests, differentiated by soil chemistry and mature tree density. Morphological and molecular analyses revealed a total of 22 fungal taxa. From detected ECM fungal taxa, 13 were noted at Site I and 13 at Site II. Only four taxa were found in both sites (Russula ochroleuca, Thelephora terrestris, Lactarius tabidus and Paxillus involutus). The most abundant species at Site I (lower mineral concentration, high tree density) was Hydnotrya tulasnei (25.7?%), followed by Pseudotomentella tristis, Tomentella sublilacina and Russula puelaris. At Site II (higher mineral concentration, low tree density) the dominant fungal symbiont of larch seedlings was clearly Wilcoxina mikolae, which accounted for 74?% of mycorrhizal tips. The less abundant species comprised T. terrestris, L. tabidus, Xerocomus pruinatus and R. ochroleuca. The analysis of similarity (ANOSIM) and non-metric multidimensional scaling (NMDS) ordination clearly separated the ECM fungal assemblages in the two sites tested. Because our study sites were differentiated by many factors, it is not easy to distinguish one factor in particular to explain the differences observed between the ECM communities at Sites I and II. The results obtained significantly increase our knowledge about the diversity of the ECM fungi hosted by L. decidua. The large number of ECM fungi detected was the first observation showing these fungi as symbiotic partners of European larch.     

Ectomycorrhizal fungal communities of pedunculate and sessile oak seedlings from bare-root forest nurseries

In this study, we present the detailed molecular investigation of the ectomycorrhizal (ECM) community of Quercus petraea and Quercus robur seedlings grown in bare-root forest nurseries. In all tested oak samples, mycorrhizal colonization was nearly 100%. Morphological observation and molecular investigations (sequencing of fungal ITS rDNA) revealed a total of 23 mycorrhizal taxa. The most frequent and abundant fungal taxa were Hebeloma sacchariolens, Tuber sp., and Peziza sp.; from the detected fungal taxa, 20 were noted for Q. petraea and 23 for Q. robur. Depending on the nursery, the species richness of identified ECM fungal taxa for both oak species ranged from six to 11 taxa. The mean species richness for all nurseries was 5.36 and 5.82 taxa per Q. petraea and Q. robur sample, respectively. According to the analysis of similarity, ECM fungal communities were similar for Q. petraea and Q. robur (R = 0.019; p = 0.151). On the other hand, detected fungal communities were significantly different between nurseries (R = 0.927; p < 0.0001). Using the Spearman rank correlation, it was determined that the ectomycorrhizal diversity (in terms of richness, the Shannon diversity, evenness, and Simpson dominance indices) is significantly related to the soil parameters of each nursery. We conclude that individual nursery may be considered as separate ecological niches that strongly discriminate diversity of ECM fungi.     

Ectomycorrhizal fungal communities associated with Pinus thunbergii in the eastern coastal pine forests of Korea

We investigated the ectomycorrhizal (ECM) fungal colonization status of Pinus thunbergii mature trees and regenerating seedlings varying in age in coastal pine forests on the east coast of Korea. We established one 20 × 20-m plot at each of two study sites at P. thunbergii coastal forests in Samcheok. Fifty soil blocks (5 × 5 × 15 cm) were sampled at regular intervals, and ten P. thunbergii seedlings of age 0, 1–3, 3–5, and 5–10 years were sampled in each study plot. In total of 27 ECM fungal taxa, Cenococcum geophilum was dominant, followed by Russula sp., Sebacina sp., and unidentified Cortinuris sp. in mature trees. In 0-year-old seedlings, some fungal species such as Sebacina sp., C. geophilum, and unidentified Cortinarius sp. were dominant whereas only C. geophilum was dominant after 1 year, and there were no apparent succession patterns in ECM fungal compositions beyond a host age of 1 year. Most ECM fungal taxa that had colonized seedlings of each age class were also observed in roots of mature trees in each site. These taxa accounted for 86.7–100% and 96.4–98.4% of ECM abundance in seedlings and mature trees, respectively. The results indicate that the species composition of ECM fungal taxa colonizing seedlings of different age in forests is similar to that of surrounding mature trees. Our results also showed that C. geophilum is a common and dominant ECM fungus in P. thunbergii coastal forests and might play a significant role in their regeneration.     

Photosynthetic CO2-fixing activity in dark-grown spruce seedlings

Bicarbonate-dependent O₂-evolving activity in dark-grown cotyledonsof Picea abies was measured with an oxygen electrode with differentpreillumination times. The activity showed a slight linear increasewith increasing preillumination time. On the other hand, O₂-evolvingactivity (Hill activity) of chloroplasts prepared from preilluminateddark-grown cotyledons exhibited a characteristic change of asteep rise followed by a gradual increase with increasing preilluminationtime. The results obtained were discussed in connection withthe light activation of the latent, inactive O₂-evolving centerin dark-grown cotyledons. (Received December 8, 1978; )     

Ectomycorrhizal fungal sporocarp diversity and discovery of new taxa in Dicymbe monodominant forests of the Guiana Shield

Ectomycorrhizal (ECM) fungi historically were considered poorly represented in Neotropical forests but in the central Guiana Shield substantial areas are dominated by leguminous ECM trees. In the Upper Potaro Basin of Western Guyana, ECM fungi were sampled for 7?years during the rainy seasons of 2000–2008 in three 1-ha plots in primary monodominant forests of the ECM canopy tree Dicymbe corymbosa (Fabaceae subfam. Caesalpinioideae). Over the plot sampling period sporocarps of 126 species of putative or confirmed ECM fungi were recovered. These taxa represented 13 families and 25 genera of primarily Agaricomycetes, but also Ascomycota (Elaphomycetaceae), the majority of which are new to science. Russulaceae contained the most species (20 Russula; 9 Lactarius), followed by Boletaceae (8 genera, 25 spp.), Clavulinaceae (17 Clavulina), and Amanitaceae (16 Amanita). An additional 46 species of ECM fungi were collected in forests of the Upper Potaro Basin outside the study plots between 2000 and 2010, bringing the regional number of ECM species known from sporocarps to 172. This is the first long-term ECM macrofungal dataset from an ECM-dominated Neotropical forest, and sporocarp diversity is comparable to that recorded for ECM-diverse temperate and boreal forests. While a species accumulation curve indicated that ECM sporocarp diversity was not fully recovered inside of the plots,?~80% of the total species were recovered in the first year. Sequence data from ECM roots have confirmed the ECM status of 56 taxa represented by corresponding sporocarp data. However,?>50% of ECM fungal species from roots remain undiscovered as sporocarps, leading to a conservative estimate of?>?250 ECM species at the Potaro site. Dicymbe forests in Guyana are a hotspot for ECM fungal diversity in the Neotropics.     

Feeding by short-snouted weevils on seedlings of seven tree species planted beneath Norway spruce at differing stand densities

1 Short-snouted weevils, including Strophosoma spp. and related species, may damage tree seedlings. We investigated the damage caused by these weevils feeding on seedlings of seven tree species planted in clear-cuts and under shelterwoods with three densities (control, dense, and sparse).
2 There were no pronounced differences in damage caused by short-snouted weevils in the various shelterwood densities. Most feeding occurred in the clear-cuts during the first year, whereas more seedlings were damaged in the shelterwoods of all densities in the second year. In the third year, virtually no feeding occurred in either the clear-cuts or shelterwoods. We cannot explain this pattern of damage, but a fallow period of 2 years seems to prevent short-snouted weevil damage.
3 We determined the general feeding preferences for short-snouted weevils to be cherry, lime > beech, oak, spruce > maple, ash. However, although Strophosoma mellanogrammum [Correction added after online publication 8 December 2008: Strophosoma melanogrammum corrected to Strophosoma mellanogrammum ] was observed feeding on seedlings, no full short-snouted weevil inventory was conducted, so caution must be exercised when drawing conclusions from this study regarding weevil damage patterns and feeding preferences.
4 Short-snouted weevils can sometimes occur in large numbers and may destroy entire reforestation projects, but in our study their influence on seedling growth and survival was minor.     

Ectomycorrhizal fungal communities of Quercus liaotungensis along local slopes in the temperate oak forests on the Loess Plateau, China

Topographic factors strongly affect the diversity of plants and local environmental conditions, yet little is known about their effects on the distribution of ectomycorrhizal fungi (EMF). By combining morphological and molecular identification methods, we investigated the relationship between EMF communities of Quercus liaotungensis and topographic factors along local slopes in the temperate oak forest on the Loess Plateau of northwest China. ITS-RFLP analysis revealed a high diversity of EMF taxa (135 taxa) associated with Q. liaotungensis along three local slopes. EMF communities among slope sites or slope positions, tended to share major common EMF species, which accounted for more than 80 % of the total EMF abundance, and showed a diverse distribution, which mainly related to rare species. Ordination analyses showed that EMF taxa distribution was significantly correlated with several environmental variables (slope site, slope position, slope gradient, and soil C:N). Topography-mediated changes of environmental conditions may be important determinants of the distribution of EMF taxa along local slopes (slope position and slope site) in the central Loess Plateau.     

Ectomycorrhizal colonisation of Sitka spruce [Picea sitchensis (Bong.) Carr] seedlings in a Scottish plantation forest

 The ectomycorrhizal (ECM) colonisation of seedling Sitka spruce (Picea sitchensis) was examined in an uneven-aged plantation forest in southern Scotland. The extent of ECM colonisation of individual seedlings was 43.8–97.2%, with an overall mean of 80.3 ± 1.1%. A total of 13 ECM morphotypes were differentiated, with 1–4 ECM types colonising an individual seedling. ECM colonisation was dominated by a single species, Tylospora fibrillosa, which accounted for 72.4–97.7% of the ECM colonisation recorded, on a plot mean basis. Other ECM types appeared to be distributed very patchily, only two types (Lactarius sp. and Mycelium radicis atrovirens Melin) exceeding a mean of 10% colonisation in any one plot. No significant correlations were recorded between ECM colonisation and seedling growth, or between ECM colonisation and soil pH, loss-on-ignition, or water content. Accepted: 16 October 1997     

Water flux and canopy conductance of natural versus planted forests in Patagonia, South America

In NW Patagonia, South America, natural shrublands and mixed forests of short Nothofagus antarctica (G. Forst.) Oerst. trees are currently being replaced by plantations with Pseudotsuga menziesii (Mirb) Franco. This land use change is controversial because the region is prone to drought, and replacement of native vegetation by planted forests may increase vegetation water use. The goal of this study was to examine the physiological differences, especially the response of water flux and canopy conductance to microclimate, that lead to greater water use by exotic trees compared to native trees. Meteorological variables and sapflow density of P. menziesii and four native woody species were measured in the growing season 2005–2006. Canopy conductance (gc) was estimated for both the exotic (monoculture) and native (multi-species) systems, including the individual contributions of each species of the native forest. Sapflow density, stand-level transpiration and gc were related to leaf-to-air vapor pressure difference (VPD). All native species had different magnitudes and diurnal patterns of sapflow density compared to P. menziesii, which could be explained by the different gc responses to VPD. Stomatal sensitivity to VPD suggested that all native species have a stronger stomatal control of leaf water potential and transpiration due to hydraulic limitations compared to P. menziesii. In conclusion, differences in water use between a P. menziesii plantation and a contiguous native mixed forest of similar basal area could be explained by different gc responses to VPD between species (higher sensitivity in the native species), in addition to particular characteristics of the native forest structure.     

Habitat availability in forests and clearcuts for saproxylic beetles associated with aspen

To maintain biodiversity in managed, boreal forest in Scandinavia, aspen trees (Populus tremula) are often retained at clearcutting. In this study, the habitat availability for beetles associated with aspen coarse woody debris (CWD) was predicted for forests and clearcuts with a model of CWD dynamics. Habitat requirements of eight beetle species (Agathidium bicolor, Cerylon ferrugineum, Cyphaea curtula, Endomychus coccineus, Homalota plana, Mycetophagus fulvicollis, Ptilinus fuscus and Xylotrechus rusticus) were obtained from their occurrence patterns in relation to characteristics of CWD objects in forest and on clearcuts in a study landscape in central Sweden. Three species were more frequent in forest and three at clearcuts. Five species increased with increasing girth of the CWD. Three were more frequent on standing CWD, and two on lying CWD. From the same study area, we also obtained field data on the recruitment of CWD (i.e., tree mortality) and amounts of different types of CWD. Annual tree mortality of aspen was higher for recent clearcuts (6.3%) compared with older clearcuts (1.1%). For all species, the habitat availability was higher on clearcuts, because enhanced tree mortality increased the amount of recently dead CWD. As a conclusion, green-tree retention of aspen is a conservation effort that is beneficial for species associated with aspen CWD.     

Ectomycorrhizal fungal communities on seedlings and conspecific trees of Pinus mugo grown on the coastal dunes of the Curonian Spit in Lithuania

Ectomycorrhizal (ECM) communities of mature trees and regenerating seedlings of a non-native tree species Pinus mugo grown in a harsh environment of the coastal region of the Curonian Spit National Park in Lithuania were assessed. We established three study sites (S1, S2, and S3) that were separated from each other by 15 km. The ECM species richness was rather low in particular for mature, 100-year-old trees: 12 ectomycorrhizal taxa were identified by molecular analysis from 11 distinguished morphotypes. All 12 taxa were present on seedlings and on mature trees, with between 8–11 and 9–11 taxa present on seedlings and mature trees, respectively. Cenococcum geophilum dominated all ECM communities, but the relative abundance of C. geophilum mycorrhizas was nearly two times higher on seedlings than on mature trees. Mycorrhizal associations formed by Wilcoxina sp., Lactarius rufus, and Russula paludosa were also abundant. Several fungal taxa were only occasionally detected, including Cortinarius sp., Cortinarius obtusus, Cortinarius croceus, and Meliniomyces sp. Shannon’s diversity indices for the ECM assemblages of P. mugo ranged from 0.98 to 1.09 for seedling and from 1.05 to 1.31 for mature trees. According to analysis of similarity, the mycorrhizal communities were similar between the sites (R = 0.085; P = 0.06) and only slightly separated between seedlings and mature trees (R = 0.24; P < 0.0001). An incidental fruiting body survey that was conducted weakly reflected the below-ground assessment of the ECM fungal community and once again showed that ECM and fruiting body studies commonly supply different partial accounts of the true ECM fungal diversity. Our results show that P. mugo has moved into quite distinct habitats and is able to adapt a suite of ECM symbionts that sufficiently support growth and development of this tree and allow for natural seedling regeneration.     

Ectomycorrhizal fungal community in alkaline-saline soil in northeastern China

Alkaline-saline soil is widespread in arid and semiarid regions of the world and causes severe environmental and agricultural problems. To advance our understanding of the adaptation of ectomycorrhizal fungi (EMF) to alkaline-saline soil, we investigated EMF communities on Mongolian willow (Salix linearistipularis) growing in alkaline-saline soil (up to pH 9.2) in northeastern China. In total, 75 root samples were collected from 25 willow individuals over 4.7 ha. To identify fungal species in ectomycorrhizal root tips, we used terminal restriction fragment length polymorphism and sequencing analyses of the internal transcribed spacer region of ribosomal DNA. We detected 11 EMF species, including species of Inocybe, Hebeloma, and Tomentella of the Basidiomycota and three Ascomycota species. The EMF richness of the study site was estimated to be 15–17 using major estimators. The most abundant species was Geopora sp. 1, while no Geopora-dominated EMF communities have been reported so far. Phylogenetic analysis showed that the phylogroup including Geopora sp. 1 has been found mostly in alkaline soil habitats, indicating its adaptation to high soil pH. Because EMF are indispensable for host plant growth, the EMF species detected in this study may be useful for restoration of alkaline-saline areas.     

Aluminium effects on spruce and beech seedlings

Summary Natural spruce seedlings sampled on acid brown soil of the Belgian Ardennes, either on mineral soil, or on the litter layer, show higher Al content in the latter case, where substrate Al content is lower. Absorbing power of the root for Al organic chelates is probably higher than for Al⁺³ ions.Most soluble Al is chelated, especially in the holorganic and hemiorganic layers, under spruce and beech. In the mineral layers pH is above 3.8, and total Al in soil solutions is always found to be less than 2 eq/ml.