Reduced aboveground tree growth associated with higher arbuscular mycorrhizal fungal diversity in tropical forest restoration

Establishing diverse mycorrhizal fungal communities is considered important for forest recovery, yet mycorrhizae may have complex effects on tree growth depending on the composition of fungal species present. In an effort to understand the role of mycorrhizal fungi community in forest restoration in southern Costa Rica, we sampled the arbuscular mycorrhizal fungal (AMF) community across eight sites that were planted with the same species (Inga edulis, Erythrina poeppigiana, Terminalia amazonia, and Vochysia guatemalensis) but varied twofold to fourfold in overall tree growth rates. The AMF community was measured in multiple ways: as percent colonization of host tree roots, by DNA isolation of the fungal species associated with the roots, and through spore density, volume, and identity in both the wet and dry seasons. Consistent with prior tropical restoration research, the majority of fungal species belonged to the genus Glomus and genus Acaulospora, accounting for more than half of the species and relative abundance found on trees roots and over 95% of spore density across all sites. Greater AMF diversity correlated with lower soil organic matter, carbon, and nitrogen concentrations and longer durations of prior pasture use across sites. Contrary to previous literature findings, AMF species diversity and spore densities were inversely related to tree growth, which may have arisen from trees facultatively increasing their associations with AMF in lower soil fertility sites. Changes to AMF community composition also may have led to variation in disturbance susceptibility, host tree nutrient acquisition, and tree growth. These results highlight the potential importance of fungal–tree–soil interactions in forest recovery and suggest that fungal community dynamics could have important implications for tree growth in disturbed soils.     

Molecular diversity of arbuscular mycorrhizal fungi and patterns of host association over time and space in a tropical forest

We have used molecular techniques to investigate the diversity and distribution of the arbuscular mycorrhizal (AM) fungi colonizing tree seedling roots in the tropical forest on Barro Colorado Island (BCI), Republic of Panama. In the first year, we sampled newly emergent seedlings of the understory treelet Faramea occidentalis and the canopy emergent Tetragastris panamensis, from mixed seedling carpets at each of two sites. The following year we sampled surviving seedlings from these cohorts. The roots of 48 plants were analysed using AM fungal-specific primers to amplify and clone partial small subunit (SSU) ribosomal RNA gene sequences. Over 1300 clones were screened for random fragment length polymorphism (RFLP) variation and 7% of these were sequenced. Compared with AM fungal communities sampled from temperate habitats using the same method, the overall diversity was high, with a total of 30 AM fungal types identified. Seventeen of these types have not been recorded previously, with the remainder being similar to types reported from temperate habitats. The tropical mycorrhizal population showed significant spatial heterogeneity and nonrandom associations with the different hosts. Moreover there was a strong shift in the mycorrhizal communities over time. AM fungal types that were dominant in the newly germinated seedlings were almost entirely replaced by previously rare types in the surviving seedlings the following year. The high diversity and huge variation detected across time points, sites and hosts, implies that the AM fungal types are ecologically distinct and thus may have the potential to influence recruitment and host composition in tropical forests.     

Multi-host ectomycorrhizal fungi are predominant in a Guinean tropical rainforest and shared between canopy trees and seedlings

The diversity of ectomycorrhizal (ECM) fungi on adult trees and seedlings of five species, Anthonotha fragrans, Anthonotha macrophylla, Cryptosepalum tetraphyllum, Paramacrolobium coeruleum and Uapaca esculenta, was determined in a tropical rain forest of Guinea. Ectomycorrhizae were sampled within a surface area of 1600 m(2), and fungal taxa were identified by sequencing the rDNA Internal Transcribed Spacer region. Thirty-nine ECM fungal taxa were determined, of which 19 multi-hosts, 9 single-hosts and 11 singletons. The multi-host fungi represented 92% (89% when including the singletons in the analysis) of the total abundance. Except for A. fragrans, the adults of the host species displayed significant differentiation for their fungal communities, but their seedlings harboured a similar fungal community. These findings suggest that there was a potential for the formation of common mycorrhizal networks in close vicinity. However, no significant difference was detected for the δ(13)C and δ(15)N values between seedlings and adults of each ECM plant, and no ECM species exhibited signatures of mixotrophy. Our results revealed (i) variation in ECM fungal diversity according to the seedling versus adult development stage of trees and (ii) low host specificity of ECM fungi, and indicated that multi-host fungi are more abundant than single-host fungi in this forest stand.     

The potential for mycobiont sharing between shrubs and seedlings to facilitate tree establishment after wildfire at Alaska arctic treeline

Root‐associated fungi, particularly ectomycorrhizal fungi (EMF), are critical symbionts of all boreal tree species. Although climatically driven increases in wildfire frequency and extent have been hypothesized to increase vegetation transitions from tundra to boreal forest, fire reduces mycorrhizal inoculum. Therefore, changes in mycobiont inoculum may potentially limit tree‐seedling establishment beyond current treeline. We investigated whether ectomycorrhizal shrubs that resprout after fire support similar fungal taxa to those that associate with tree seedlings that establish naturally after fire. We then assessed whether mycobiont identity correlates with the biomass or nutrient status of these tree seedlings. The majority of fungal taxa observed on shrub and seedling root systems were EMF, with some dark septate endophytes and ericoid mycorrhizal taxa. Seedlings and adjacent shrubs associated with similar arrays of fungal taxa, and there were strong correlations between the structure of seedling and shrub fungal communities. These results show that resprouting postfire shrubs support fungal taxa compatible with tree seedlings that establish after wildfire. Shrub taxon, distance to the nearest shrub and fire severity influenced the similarity between seedling and shrub fungal communities. Fungal composition was correlated with both foliar C:N ratio and seedling biomass and was one of the strongest explanatory variables predicting seedling biomass. While correlative, these results suggest that mycobionts are important to nutrient acquisition and biomass accrual of naturally establishing tree seedlings at treeline and that mycobiont taxa shared by resprouting postfire vegetation may be a significant source of inoculum for tree‐seedling establishment beyond current treeline.     

Arbuscular mycorrhizal communities in tropical forests are affected by host tree species and environment

Arbuscular mycorrhizal (AM) fungi are mutualists with plant roots that are proposed to enhance plant community diversity. Models indicate that AM fungal communities could maintain plant diversity in forests if functionally different communities are spatially separated. In this study we assess the spatial and temporal distribution of the AM fungal community in a wet tropical rainforest in Costa Rica. We test whether distinct fungal communities correlate with variation in tree life history characteristics, with host tree species, and the relative importance of soil type, seasonality and rainfall. Host tree species differ in their associated AM fungal communities, but differences in the AM community between hosts could not be generalized over life history groupings of hosts. Changes in the relative abundance of a few common AM fungal species were the cause of differences in AM fungal communities for different host tree species instead of differences in the presence and absence of AM fungal species. Thus, AM fungal communities are spatially distinguishable in the forest, even though all species are widespread. Soil fertility ranging between 5 and 9 Mg/ha phosphorus did not affect composition of AM fungal communities, although sporulation was more abundant in lower fertility soils. Sampling soils over seasons revealed that some AM fungal species sporulate profusely in the dry season compared to the rainy season. On one host tree species sampled at two sites with vastly different rainfall, relative abundance of spores from Acaulospora was lower and that of Glomus was relatively higher at the site with lower and more seasonal rainfall.     

Evidence for mutualist limitation: the impacts of conspecific density on the mycorrhizal inoculum potential of woodland soils

The ability of seedlings to establish can depend on the availability of appropriate mycorrhizal fungal inoculum. The possibility that mycorrhizal mutualists limit the distribution of seedlings may depend on the prevalence of the plant hosts that form the same type of mycorrhizal association as the target seedling species and thus provide inoculum. We tested this hypothesis by measuring ectomycorrhizal (EM) fine root distribution and conducting an EM inoculum potential bioassay along a gradient of EM host density in a pinyon–juniper woodland where pinyon is the only EM fungal host while juniper and other plant species are hosts for arbuscular mycorrhizal (AM) fungi. We found that pinyon fine roots were significantly less abundant than juniper roots both in areas dominated aboveground by juniper and in areas where pinyon and juniper were co-dominant. Pinyon seedlings establishing in pinyon–juniper zones are thus more likely to encounter AM than EM fungi. Our bioassay confirmed this result. Pinyon seedlings were six times less likely to be colonized by EM fungi when grown in soil from juniper-dominated zones than in soil from either pinyon–juniper or pinyon zones. Levels of EM colonization were also reduced in seedlings grown in juniper-zone soil. Preliminary analyses indicate that EM community composition varied among sites. These results are important because recent droughts have caused massive mortality of mature pinyons resulting in a shift towards juniper-dominated stands. Lack of EM inoculum in these stands could reduce the ability of pinyon seedlings to re-colonize sites of high pinyon mortality, leading to long-term vegetation shifts.     

Vesicular-arbuscular mycorrhizal inoculum potential affects the growth of Stryphnodendron microstachyum seedlings in a Costa Rican human tropical lowland

This study used a plant bioassay to investigate the vesicular-arbuscular mycorrhizal (VAM) inoculum potential of soil from three vegetation types (fern, secondary forest, and grass) in an abandoned pasture in the tropical humid lowlands at La Selva, in northeastern Costa Rica. Growth, measured as seedling height, number of leaves, and total (above- and belowground) biomass, of Stryphnodendron microstachyum Poepp. et Endl. (Synon. S. excelsum Harms) seedlings was significantly lower when grown in soil inoculum from the fern areas than in soil inoculum from the forest and grass areas. However, S. microstachyum seedlings grown in the fern inoculum had significantly greater VAM colonization than seedlings grown in the forest and grass inoculum. In addition, roots collected from a dominant plant species from each of the three vegetation types showed that the fern (Nephrolepsis biserrata) had significantly greater mycorrhizal colonization than the tree (Pentaclethra macroloba (Willd.) Kuntze or the grass (Brachiaria spp.). The results of this study suggest that differences in mycorrhizal inoculum potential among vegetation types and its effects on seedling growth may have important implications for the restoration and management of degraded lands.     

Forest reclamation of fly ash deposit: a field study on appraisal of mycorrhizal inoculation

An extensive field trial was established on a fly ash deposit (1) to evaluate whether the inoculation with arbuscular mycorrhizal fungi (AMF) and/or ectomycorrhizal fungi (EcMF) improves growth and survival of 13 planted tree species and (2) to trace the inoculated mycorrhizal fungi in tree roots after one growing season. Molecular methods were applied to characterize AMF and EcMF entering the studied system (inocula, native soil, and roots of nursery seedlings). Biometric parameters and mortality of the trees were recorded and the presence of AMF and EcMF in sampled trees was determined both microscopically and genetically. Mycorrhizal inoculation did not improve survival or growth of any tree species. Most AMF‐host and all EcMF‐host seedlings were highly precolonized already from the nursery. An abundant and diverse AMF community was also found in the field soil. The AMF inoculum taxa partially overlapped with AMF in the native soil and in the precolonized roots. After one season, the only two inoculum‐unique AMF taxa were detected in host species non‐precolonized or only partially precolonized from the nursery. The components of EcMF inoculum were not detected in any sampled tree. After the season, the ectomycorrhizal hosts maintained most of their original EcMF taxa gathered in nursery, some tree species were additionally colonized by EcMF probably originating from the soil. Our results show considerable self‐restoration potential of nature on the target site. Mycorrhizal inoculation thus did not bring any conclusive advantage to the planted trees and seems superfluous for reclamation practice on the fly ash deposit.     

Terrestrial vertebrates promote arbuscular mycorrhizal fungal diversity and inoculum potential in a rain forest soil

We examined whether terrestrial vertebrates affected the arbuscular mycorrhizal fungal spore communities and mycorrhizal inoculum potential (MIP) of a tropical rain forest soil by comparing plots where terrestrial vertebrates had been excluded for 3 years to adjacent control plots. We extracted spores from soil using sucrose density gradient centrifugation and assayed MIP by growing seedlings of maize ( Zea mays ) and a rain forest tree ( Flindersia brayleana ) in intact soil cores from exclosure and control plots. Control plots had significantly higher spore abundance, species richness and diversity than exclosures. Spore community composition also differed significantly between exclosure and control plots. Seedlings of both plant species grown in control cores had significantly higher arbuscular-mycorrhizal colonization than those grown in exclosure cores. This study suggests that loss of vertebrates could alter rates of mycorrhizal colonization with consequences for community and ecosystem properties.     

High compatibility between arbuscular mycorrhizal fungal communities and seedlings of different land use types in a tropical dry ecosystem

We conducted this study to explore limitations for the establishment of mycorrhizal associations in disturbed areas of the tropical dry ecosystem in the Chamela region of Jalisco, Mexico. Specifically, we: (1) assessed the diversity and composition of arbuscular mycorrhizal fungal (AMF) communities through spore morphospecies identification in three common land uses (primary forest, secondary forest, and pasture), (2) tested the inoculum potential of the AMF communities and the effect of water stress on the establishment of mycorrhizal associations in seedlings of various plant species, and (3) explored the importance of AMF community composition on early seedling development. Soil and root samples were taken from 15 random points in each of three plots established in two primary forests, two 26-year-old secondary forests, and two 26-year-old pastures. We expected that because of soil degradation and management, pastures would have the lowest and primary forests the highest AMF species richness. We found evidence for changes in AMF species composition due to land use and for higher morphospecies richness in primary forests than in secondary forests and pastures. We expected also that water stress limited plant and mycorrhizal development and that plants and AMF communities from secondary forests and pastures would be less affected by (better adapted to) water stress than those from the primary forest. We found that although all plant species showed biomass reductions under water stress, only some of the plant species had lower mycorrhizal development under water stress, and this was regardless of the AMF community inoculated. The third hypothesis was that plant species common to all land use types would respond similarly to all AMF communities, whereas plant species found mainly in one land use type would grow better when inoculated with the AMF community of that specific land use type. All plant species were however equally responsive to the three AMF communities inoculated, indicating that all plants established functionally compatible AMF in each community, with no preferences. The results suggest that early seedling growth and mycorrhizal development in secondary forests and pastures is not likely limited by diversity, quantity, or quality of mycorrhizal propagules but by the high temperature and water stress conditions prevailing at those sites.     

The response of ectomycorrhizal fungal inoculum to long-term increases in nitrogen supply

The inoculum of ectomycorrhizal (EM) fungi was examined in a 16 y long nitrogen fertilization experiment maintained in a temperate oak savanna. To measure EM fungal inoculum, bur oak seedlings were grown in three types of bioassays: (i) intact soil cores that measure inoculum such as spores, mycelia and mycorrhizal roots; (ii) resistant propagule bioassays that measure inoculum types resistant to soil drying; and (iii) previously mycorrhizal root bioassays that measure the ability of EM fungi to colonize new roots from mycorrhizal roots. Colonization of bur oak seedlings was characterized by morphotyping and where necessary by restriction analysis and internal transcribed spacer (ITS) sequencing. Fourteen morphotypes were found in intact soil core bioassays with species of Cortinarius, Cenococcum and Russula abundant. Five morphotypes were found in resistant propagule bioassays with Cenococcum, a thelephoroid morphotype and a Wilcoxina-like ascomycete abundant and frequent. In intact soil core bioassays total percent root colonization and number of morphotypes were not affected by N supply in 2000 and 2001. However the composition of EM fungi colonizing oak seedling roots was different with increased N supply such that Russula spp. (primarily Russula aff. amoenolens) were most abundant at the highest level of N supply. Dominant Russula spp. did not colonize any roots in resistant propagule bioassays but did colonize oak seedling roots from previously mycorrhizal roots. Results suggest that in this savanna N supply can influence the kinds of inoculum propagules present and thereby might affect the dynamics of ectomycorrhizal communities by differentially influencing reproductive and colonization strategies.     

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.     

Links between tree species, symbiotic fungal diversity and ecosystem functioning in simplified tropical ecosystems

We studied the relationships among plant and arbuscular mycorrhizal (AM) fungal diversity, and their effects on ecosystem function, in a series of replicate tropical forestry plots in the La Selva Biological Station, Costa Rica. Forestry plots were 12 yr old and were either monocultures of three tree species, or polycultures of the tree species with two additional understory species. Relationships among the AM fungal spore community, host species, plant community diversity and ecosystem phosphorus-use efficiency (PUE) and net primary productivity (NPP) were assessed. Analysis of the relative abundance of AM fungal spores found that host tree species had a significant effect on the AM fungal community, as did host plant community diversity (monocultures vs polycultures). The Shannon diversity index of the AM fungal spore community differed significantly among the three host tree species, but was not significantly different between monoculture and polyculture plots. Over all the plots, significant positive relationships were found between AM fungal diversity and ecosystem NPP, and between AM fungal community evenness and PUE. Relative abundance of two of the dominant AM fungal species also showed significant correlations with NPP and PUE. We conclude that the AM fungal community composition in tropical forests is sensitive to host species, and provide evidence supporting the hypothesis that the diversity of AM fungi in tropical forests and ecosystem NPP covaries.     

Phylogenetically diverse AM fungi from Ecuador strongly improve seedling growth of native potential crop trees

In many deforested regions of the tropics, afforestation with native tree species could valorize a growing reservoir of degraded, previously overused and abandoned land. The inoculation of tropical tree seedlings with arbuscular mycorrhizal fungi (AM fungi) can improve tree growth and viability, but efficiency may depend on plant and AM fungal genotype. To study such effects, seven phylogenetically diverse AM fungi, native to Ecuador, from seven genera and a non-native AM fungus (Rhizophagus irregularis DAOM197198) were used to inoculate the tropical potential crop tree (PCT) species Handroanthus chrysanthus (synonym Tabebuia chrysantha), Cedrela montana, and Heliocarpus americanus. Twenty-four plant-fungus combinations were studied in five different fertilization and AMF inoculation treatments. Numerous plant growth parameters and mycorrhizal root colonization were assessed. The inoculation with any of the tested AM fungi improved seedling growth significantly and in most cases reduced plant mortality. Plants produced up to threefold higher biomass, when compared to the standard nursery practice. AM fungal inoculation alone or in combination with low fertilization both outperformed full fertilization in terms of plant growth promotion. Interestingly, root colonization levels for individual fungi strongly depended on the host tree species, but surprisingly the colonization strength did not correlate with plant growth promotion. The combination of AM fungal inoculation with a low dosage of slow release fertilizer improved PCT seedling performance strongest, but also AM fungal treatments without any fertilization were highly efficient. The AM fungi tested are promising candidates to improve management practices in tropical tree seedling production.     

Community composition and diversity of Neotropical root‐associated fungi in common and rare trees

Interactions between plants and root‐associated fungi can affect the assembly, diversity, and relative abundances of tropical plant species. Host–symbiont compatibility and some degree of host specificity are prerequisites for these processes to occur, and these prerequisites may vary with host abundance. However, direct assessments of whether specificity of root‐associated fungi varies with host abundance are lacking. Here, in a diverse tropical forest in Los Tuxtlas, Mexico, we couple DNA metabarcoding with a sampling design that controls for host phylogeny, host age, and habitat variation, to characterize fungal communities associated with the roots of three confamilial pairs of host species that exhibit contrasting (high and low) relative abundances. We uncovered a functionally and phylogenetically diverse fungal community composed of 1,038 OTUs (operational taxonomic units with 97% genetic similarity), only 14 of which exhibited host specificity. Host species was a significant predictor of fungal community composition only for the subset of OTUs composed of putatively pathogenic fungi. We found no significant difference in the number of specialists associating with common versus rare trees, but we found that host abundance was negatively correlated with the diversity of root fungal communities. This latter result was significant for symbiotrophs (mostly arbuscular mycorrhizal fungi) and, to a lesser extent, for pathotrophs (mostly plant pathogens). Thus, root fungal communities differ between common and rare trees, which may impact the strength of conspecific negative density dependence. Further studies from other tropical sites and host lineages are warranted, given the role of root‐associated fungi in biodiversity maintenance.     

Effects of Mycorrhizae and Nontarget Organisms on Restoration of a Seasonal Tropical Forest in Quintana Roo, Mexico: Factors Limiting Tree Establishment

We initiated a study of the effects of mycorrhizal fungal community composition on the restoration of tropical dry seasonal forest trees. Tree seedlings were planted in a severely burned experimental site (1995 fire) during the growing season of 1998 at the El Edén Ecological Reserve, in north Quintana Roo, Mexico. Seedlings of Leucaena leucocephala, Guazuma ulmifolia, Caesalpinia violacea, Piscidia piscipula, Gliricidia sepium, and Cochlospermum vitifolium were germinated in steam‐sterilized soil and either remained uninoculated (nonmycorrhizal at transplanting) or were inoculated with mycorrhizal fungi in soils from early‐seral (recently burned) or late‐seral (mature forest) inoculum. Inoculum from the early‐seral soil was largely Glomus spp., whereas a diverse community of arbuscular mycorrhizal fungi were reintroduced from the mature forest including species of Scutellospora, Gigaspora, Glomus, Sclerocystis, and Acaulospora. Plants grew better when associated with the mature forest inoculum, unlike a previous experiment in which plants grew taller with the early‐seral inoculum. Reasons for the different responses include a less‐intense burn resulting in more residual organic matter. In addition to mycorrhizal responses, plants were severely affected by deer browsing. One tree species, C. vitifolium found in the region but not in the reserve, was eliminated by a resident fungal facultative pathogen. Several practical conclusions for restoration can be made. The common nursery practice of soil sterilization may be detrimental because it eliminates beneficial mycorrhizal fungi; species not native to the site may not survive because they may not be adapted to the local pathogens; and herbivory can be severe depending on the landscape context of the restoration.     

Influence of host species on ectomycorrhizal communities associated with two co-occurring oaks (Quercus spp.) in a tropical cloud forest

Interactions between host tree species and ectomycorrhizal fungi are important in structuring ectomycorrhizal communities, but there are only a few studies on host influence of congeneric trees. We investigated ectomycorrhizal community assemblages on roots of deciduous Quercus crassifolia and evergreen Quercus laurina in a tropical montane cloud forest, one of the most endangered tropical forest ecosystems. Ectomycorrhizal fungi were identified by sequencing internal transcribed spacer and partial 28S rRNA gene. We sampled 80 soil cores and documented high ectomycorrhizal diversity with a total of 154 taxa. Canonical correspondence analysis indicated that oak host was significant in explaining some of the variation in ectomycorrhizal communities, despite the fact that the two Quercus species belong to the same red oak lineage (section Lobatae ). A Tuber species, found in 23% of the soil cores, was the most frequent taxon. Similar to oak-dominated ectomycorrhizal communities in temperate forests, Thelephoraceae, Russulaceae and Sebacinales were diverse and dominant.     

Forest microsite effects on community composition of ectomycorrhizal fungi on seedlings of Picea abies and Betula pendula

Niche differentiation in soil horizons, host species and natural nutrient gradients contribute to the high diversity of ectomycorrhizal fungi in boreal forests. This study aims at documenting the diversity and community composition of ectomycorrhizal fungi of Norway spruce ( Picea abies ) and silver birch ( Betula pendula ) seedlings in five most abundant microsites in three Estonian old-growth forests. Undisturbed forest floor, windthrow mounds and pits harboured more species than brown- and white-rotted wood. Several species of ectomycorrhizal fungi were differentially represented on either hosts, microsites and sites. Generally, the most frequent species in dead wood were also common in forest floor soil. Ordination analyses suggested that decay type determined the composition of EcM fungal community in dead wood. Root connections with in-growing mature tree roots from below affected the occurrence of certain fungal species on seedling roots systems in dead wood. This study demonstrates that ectomycorrhizal fungi differentially establish in certain forest microsites that is attributable to their dispersal and competitive abilities. Elevated microsites, especially decayed wood, act as seed beds for both ectomycorrhizal forest trees and fungi, thus affecting the succession of boreal forest ecosystems.     

Effect of tree host species on fungal community composition in a tropical rain forest in Panama

Abstract.  To determine whether host species influence the composition of fungal communities, the ascomycetes and basidiomycetes present on three tree species ( Prioria copaifera (Fabaceae), Quararibea asterolepis (Bombacaceae), and Trichilia tuberculata (Meliaceae)) were sampled on the 50-ha Forest Dynamics Project plot in lowland moist tropical forest on Barro Colorado Island, Panama. The most abundant fungal morphotypes of both ascomycetes and basidiomycetes were generalists found on all three hosts, but detrended correspondence analysis revealed distinct differences in fungal community composition among host trees. These differences among hosts were constant across census years. Randomization tests revealed that there were significantly fewer host-generalist fungi than expected for ascomycetes but not for basidiomycetes. These results indicate that host composition plays a role in structuring both ascomycete and basidiomycete fungal communities, but that the most successful fungal morphotypes are capable of colonizing multiple host species.