Spores Of Vesicular-arbuscular Mycorrhizal Fungi Research Articles

Temporal and spatial dynamics of vesicular-arbuscular mycorrhizal fungi under the canopy of Zygophyllum dumosum Boiss. in the Negev Desert

The temporal and spatial dynamics of vesicular–arbuscular mycorrhizal (VAM) fungi were investigated in a desert ecosystem. Soil samples under the canopy of Zygophyllum dumosum were collected monthly between November 1999 and October 2000 from 0–10 and 10–20 cm depths. VAM fungal colonization and spore density were used to compare the responses of VAM fungi to soil conditions. The mean percent colonization and spore density of VAM fungi reached maximal values in November 1999 and September 2000. Soil moisture was positively correlated with colonization of VAM structure groups. Vesicular and arbuscular colonization were positively correlated with soil organic matter and total soluble N. Spore density was also positively correlated with total soluble N. Our results suggest that spore density and the extent of vesicular and arbuscular colonization are useful indicators for evaluating changes in desert soil ecosystems.

Influence of edaphic and climatic factors on dynamics of root colonization and spore density of vesicular-arbuscular mycorrhizal fungi in Acacia farnesiana Willd. and A. planifrons W.et.A.

A study was conducted to assess the dynamics of vesicular-arbuscular mycorrhizal (VAM) fungi associated with Acacia farnesiana and A. planifrons in moderately fertile alkaline soils. The intensity of root colonization by VAM fungi and the distribution of VAM fungal structures varied with host species over a period of time. The occurrence of vesicles with varied morphology in the mycorrhizal roots indicates infection by different VAM fungal species. This was further confirmed from the presence of spores belonging to different VAM fungal species in the rhizosphere soils. Root colonization and spore number ranged from 56% – 72% and 5 – 14 g – 1soil in A. farnesiana and from 60% – 73% and 5 – 15 g – 1 soil in A. planifrons. Per cent root colonization and VAM spore number in the rhizosphere soil were inversely related to each other in both the Acacia species. However, patterns of the occurrence of VAM fungal structures were erratic. Spores of Acaulospora foveata, Gigaspora albida, Glomus fasciculatum, G. geosporum and Sclerocystis sinuosa were isolated from the rhizosphere of A. farnesiana whereas A. scrobiculata,G. pustulatum, G. fasciculatum,G. geosporum and G. microcarpum were isolated from that of A. planifrons. The response of VAM status to fluctuating edaphic factors varied with host species. In A. farnesiana though soil nitrogen (N) was positively correlated with root colonization, soil moisture, potassium and air temperature were negatively correlated to both root colonization and spore number. Per cent root colonization and spore number in A. planifrons were negatively related to each other. Further, in A. planifrons as the soil phosphorus and N were negatively correlated with the density of VAM fungal spores, the same edaphic factors along with soil moisture negatively influenced root colonization.

Vesicular-arbuscular mycorrhizae in tropical sedges of southern India

Twenty-four species of sedges (representing six genera) from different vegetation types in Western Ghats, South India, were examined for vesicular-arbuscular mycorrhizal (VAM) associations. All the sedges had VAM fungal infections with hyphae and vesicles, but arbuscules were observed only in 42% of the total species. The VAM fungal colonization varied considerably between species, ranging from 9 to 62%. Root colonization was positively and negatively correlated with root diameter and root hair length, respectively. The number of VAM fungal spores in the rhizosphere varied from 5 to 86 g-1 soil. No significant relationship was found between spore numbers or root colonization and either soil pH or moisture. Four Glomus spp., one Acaulospora sp., one Sclerocystis spp., and one Gigaspora sp. were identified among the VAM fungal spores. The results reflect a high incidence of VAM in sedges occurring in Western Ghats and emphasize the need to assess the VAM status of plant species from different ecosystems to understand their mycorrhizal status.

Vesicular-arbuscular mycorrhizal spore populations in sugar maple (Acer saccharum marsh. L.) forests

The numbers and types of spores of vesicular-arbuscular mycorrhizal fungi occurring in the top 15 cm of the soil in three maple forests in Eastern Canada were investigated using traditional wet-sieving/decanting methods. In the most acid site, at St. Hippolyte, Quebec, where the soil had been amended with base cations, after 1 year there was no effect on the numbers of spores present. Vesicular-arbuscular mycorrhizal spores present at St. Hippolyte consisted of Glomus rubiforme, other Glomus spp. and Acaulospora spp. Although the sporocarpic species, G. aggregatum, G. macrocarpum and G. rubiforme occurred at St. Hippolyte, they were not found at the two less acid sites (Waterloo, Ontario and Lacolle, Quebec) . Spores of Acaulospora spp. were found at all three sites, but were most abundant at St. Hippolyte. At St. Hippolyte the total number of spores was much higher than at the other two sites; at Waterloo numbers were an order of magnitude lower than at St. Hippolyte. It is suggested that G. rubiforme and Acaulospora species may be adapted to acid conditions. Seasonal patterns of spore abundance suggested that Acaulospora spp. may sporulate during the spring, whereas G. rubiforme may sporulate during the fall.

Direct observation of spores of vesicular-arbuscular mycorrhizal fungi growing on sugar maple roots in the field, using sodium hexametaphosphate as a soil dispersant

A method for observing the extramatrical mycelium and attached spores of vesicular-arbuscular mycorrhizal fungi on the roots of plants recovered from the field is described. The method can be used ...

Direct Observation of Spores of Vesicular-Arbuscular Mycorrhizal Fungi Growing on Sugar Maple Roots in the Field, Using Sodium Hexametaphosphate as a Soil Dispersant

Direct Observation of Spores of Vesicular-Arbuscular Mycorrhizal Fungi Growing on Sugar Maple Roots in the Field, Using Sodium Hexametaphosphate as a Soil Dispersant

Vesicular-arbuscular mycorrhizal fungi in coastal dune plant communities I. Spore formation of Glomus spp. predominates under a patch of Elymus mollis

Vesicular-arbuscular (VA) mycorrhizal fungi in pure patches of coastal dune plantsElymus mollis, Wedelia prostrata andZoysia macrostachya were examined for frequency of occurrence and number of spores of VA mycorrhizal fungi over one year. Six species in three genera of VA mycorrhizal fungi were recovered. Under a patch ofE. mollis, spores ofAcaulospora sp. 1,Glomus tortuosum, Glomus sp. 1,Glomus sp. 2 andScutellospora gregaria were recovered. Spores ofGlomus spp. were most common. In patches ofW. prostrata andZ. macrostachya spores ofAcaulospora sp. 1,G. tortuosum, Glomus sp. 1,Glomus sp. 2,S. gregaria andScutellospora sp. 1 were found.

Soil drainage and distribution of VAM fungi in two toposequences

Much remains unknown about the distribution and abundance of vesicular-arbuscular mycorrhizal (VAM) fungi in natural ecosystems. Our objective was to determine whether soil drainage and position in the toposequence affect VAM fungal spore production and colonization of soybean ( Glycine max L. Merr.) roots. Plant roots and rhizosphere soil from 24 soils, which consisted of sets of three soils each that varied in soil drainage class from four sites located in two toposequences [Clarion-Nicollet-Webster (CNW) and Sharpsburg-Macksburg-Winterset (SMW)], were sampled. Soils were analyzed for chemical properties, and numbers of VAM fungal spores per 50 g soil were determined by a wet-sieving-and-decanting technique. The percentages of root VAM fungal colonization were determined by the grid-line intersect method. The distribution of spores among locations, series and series within locations varied significantly ( P < 0.001). Soil from the CNW toposequence averaged 417 spores (50 g) −1 soil, whereas soil from the SMW toposequence averaged 147 spores (50 g) −1 soil. Within the two toposequences, the poorly to somewhat poorly drained soils had higher spore counts than the well-drained to moderately well-drained soils. In the CNW toposequence, the mean spore counts of Nicollet and Webster soils (poorer drained) were 1.37-fold higher than those of Clarion soils (better drained). In the SMW toposequence, the mean spore counts of Macksburg and Winterset soils (poorer drained) were 2.06 fold higher than those of Sharpsburg soils (better drained). VAM fungal colonization of roots ranged from 74 to 88% in the CNW toposequence and from 68 to 86% in the SMW toposequence. No correlation was found between spore count and VAM fungal colonization.

The impact of wildfire on vesicular-arbuscular mycorrhizal fungi and their potential to influence the re-establishment of post-fire plant communities

Wildfires are a typical event in many Australian plant communities. Vesicular-arbuscular mycorrhizal (VAM) fungi are important for plant growth in many communities, especially on infertile soils, yet few studies have examined the impact of wildfire on the infectivity of VAM fungi. This study took the opportunity offered by a wildfire to compare the infectivity and abundance of spores of VAM fungi from: (i) pre-fire and post-fire sites, and (ii) post-fire burned and unburned sites. Pre-fire samples had been taken in May 1990 and mid-December 1990 as part of another study. A wildfire of moderate intensity burned the site in late December 1990. Post-fire samples were taken from burned and unburned areas immediately after the fire and 6 months after the fire. A bioassay was used to examine the infectivity of VAM fungi. The post-fire soil produced significantly less VAM infection than the pre-fire soil. However, no difference was observed between colonization of plant roots by VAM fungi in soil taken from post-fire burned and adjacent unburned plots. Soil samples taken 6 months after the fire produced significantly more VAM than corresponding soil samples taken one year earlier. Spore numbers were quantified be wet-sieving and decanting of 100-g, air-dried soil subsamples and microscopic examination. For the most abundant spore type, spore numbers were significantly lower immediately post-fire. However, no significant difference in spore numbers was observed between post-fire burned and unburned plots. Six months after the fire, spore numbers were the same as the corresponding samples taken 1 year earlier. All plants appearing in the burned site resprouted from underground organs. All post-fire plant species recorded to have mycorrhizal associations before the fire had the same associations after the fire, except for species of Conospermum (Proteaceae), which lacked internal vesicles in cortical cells in the post-fire samples.

Populations of spores of vesicular-arbuscular mycorrhizal fungi in undisturbed soils of secondary semideciduous moist tropical forest in Cameroon

Secondary semideciduous, moist tropical forest at Mbalmayo (lat. 3°31′N; long. 11°30′E), Cameroon, has 108 trees ha −1 including representatives of 90 species and 33 families of angiosperms. The most abundant species, namely Alstonia boonei, Ricinodendron heudelotti and Terminalia superba, each contribute 5% to the total number of trees. These, and many of the other species, are known to form vesicular-arbuscular (VA) (endo-) mycorrhizal associations. Using a modification of the sucrose centrifugation method, spores of VA fungi were extracted from soil of undisturbed forest. The spores were attributed to five species of Acaulospora (laevigatum, mellea, morrowae, scrobiculata and spinosa), seven og Glomus (clavisporum, etunicatum, fasciculatum, geosporum, macrocarpum, occultum and rubiformis) and two of Scutellospora (coralloidea and pellucida). There were two other distinctive types of spores, C4 and C12, with affinities to spores of Acaulospora and Scutellospora respectively. A few spores seemed to be parasitized. Of the 250 spores per 100 g dry soil 63% were attributed to G. etunicatum and 18%, 6% and 5% to aggregates of G. occultum/A. scrobiculata, A. mellea/A. morrowae and C12/ S. pellucida respectively. Although spores were very unevenly distributed (Simpson's equitability index = 0.025), mean numbers in replicate plots (each 1 ha) were fairly consistent. However, numbers of C4, A. spinosa, A. laevigatum and G. occultum/A. scrobiculata were significantly larger near the trunks of Terminalia superba than at a distance (7.5–10 m away). Total numbers of spores extracted on different occasions sometimes differed significantly, but effects of season were not established. However, during the 2 year period of the investigation numbers of spores of some relatively sparse species consistently decreased while those of others increased. Total numbers of spores in the rhizosphere soils of four tree species were usually twice as large as those of spores in bulk soil (440–600 compared with 250 per 100 g dry soil). As in bulk soil, numbers of spores in rhizosphere soils were dominated by G. etunicatum and G. occultum/A. scrobiculata, but spores of A. mellea/A. morrowae, which tended to be restricted to Entrandrophragma cylindricum and Khaya sp., were replaced by those of G. geosporum. G. etunicatum was more strongly associated with Lovoa trichilioides than Entrandrophragma cylindricum, Khaya sp. and Triplochiton scleroxylon. On the other hand, G. fasciculatum/G. macrocarpum was linked with Entrandrophragma cylindricum, Lovoa trichilioides and Triplochiton scleroxylon but not Khaya sp.

Reassessment of Tetrazolium Bromide as a Viability Stain for Spores of Vesicular-Arbuscular Mycorrhizal Fungi

Reassessment of Tetrazolium Bromide as a Viability Stain for Spores of Vesicular-Arbuscular Mycorrhizal Fungi

Occurrence and importance of mycorrhizae in aquatic trees of New South Wales, Australia

Vesicular arbuscular mycorrhizal (VAM) infection was found in KOH-cleared and lactophenolblue-stained roots of Salix babylonica, Melaleuca quinquenervia and Casuarina cunninghamiana. These are all trees growing on creeks and river banks, in stationary or slowly flowing fresh or brackish waters in swamps, creeks, drains and channels, and in seepage areas of New South Wales, Australia. Larger and older roots lacked VAM infection in the inner cortex, probably due to suberisation of cells, and the endophyte was restricted to the epidermal layers. Spores and sporocarps of the VAM fungi Glomus fasciculatus, G. mosseae, Sclerocystis rubiformis, Gigaspora margarita and an unidentified Scutellospora sp. were wet sieved and decanted from aquatic sediments and soils. The presence of similar VAM fungal spores in the aquatic sediments and terrestrial soil suggests that they probably enter the aquatic sediments through run off from the land ecosystem. All three plants formed vesicular arbuscular (VA) mycorrhizae almost exclusively in the marshy, periodically inundated soils, but the same plant species formed endo-/ ectomycorrhizae when growing in soil with higher redox potentials (E h). Salix and Melaleuca tree roots possessed both VAmycorrhizae and ectomycorrhizae. VAM roots of Casuarina were equipped with both N-fixing Frankia nodules and proteoid roots. VAM endophytes did not invade nodular cortical tissues, suggesting the presence of an exclusion mechanism which needs further study. The highest VAM infection was found in nodulated specimens. Free-floating roots growing in water close to the banks were non-mycorrhizal but were mycorrhizal in the bottom-rooting state. VAM spore number and mycorrhizal infection seem to be associated with redox-potential, i.e. lower at sites such as swamps, water or sediments with lower E h values than in terrestrial soils with higher E h values. A relationship between soil moisture gradient and VAM infection pattern became apparent from the study of a C. cunninghamiana transect on a creek embankment, i.e. typical vesicles and arbuscules were found in roots from drier soils, there was a lack of arbuscules in relatively wet soils but large lipid-filled intracellular vesicles were present, and typical vesicles and arbuscules were absent in flooded creek beds where roots were associated with coenocytic intercellular hyphae with abundant lipid droplets. The importance of VA mycorrhiza, ectomycorrhizae, N-fixing root nodules and proteoid roots at the land-water interface is discussed with reference to the use of these trees as pioneering species for stabilising river and stream banks, reducing erosion, windbreaking, and as a long-term and inexpensive means of achieving biological control of aquatic weeds by shading waterways.

VAM fungus spore populations and colonization of roots of maize and soybean under conventional and low-input sustainable agriculture

Spore populations of vesicular-arbuscular mycorrhizal (VAM) fungi and formation of mycorrhizae in maize ( Zea mays L.) and soybean ( Glycine max (L.) Merr.) were studied in three farming systems: a conventional maize-soybean rotation and two low-input systems. Spore populations were counted in soil samples obtained at planting and after harvest for two growing seasons. Maize and soybean root systems were sampled for mycorrhizae early in the growing season. Low-input plots tended to have higher populations of spores of VAM fungi than conventionally farmed plots. Further, the readily identifiable species Gigaspora gigantea (Nicol. & Gerd.) Gerdemann & Trappe, was more numerous in low-inputs plots (up to 30 spores 50 cm −3 soil) than in conventional plots (0–0.3 spores 50 cm −3 soil), suggesting farming system affected species distribution as well. Colonization of plants in the field did not always reflect VAM fungus spore populations at planting. Greenhouse bioassays showed 2.5–10 fold greater colonization of plants growing in soil from low-input than conventional systems. The results indicate that conventional farming systems yield lower levels of VAM fungi whereas low-input sustainable agriculture, with cover crops planted between cash crops, has greater populations of VAM fungi and potential to utilize the benefits of VA mycorrhizae.

The Interaction of Harvester Ants and Vesicular-Arbuscular Mycorrhizal Fungi in a Patchy Semi-Arid Environment: The Effects of Mound Structure on Fungal Dispersion and Establishment

Disc areas created by the western harvester ant, Pogonomyrmes occidentalis, around their mound nests can comprise over 10% of the land surface in semi-arid shrub steppes of the Great Basin, USA. The harvester ant mounds are abandoned after 12-20 years and the mycorrhizal fungal inoculum dispersion patterns within these patches may affect subsequent plant establishment. It was hypothesized that harvester ant activity reduces mycorrhizal inoculum levels within the disc, and that mycorrhizal fungi must re-establish in these patches from surface-deposited, immigrating inoculum. To test this, we first excavated two ant mounds, which revealed a chambered core consisting of a mat of densely packed, clipped roots with 2000-5000 times the vesicular-arbuscular mycorrhizal fungal spore density found in the surrou ding undisturbed vegetation (...)

Growth dynamics and associated mycorrhizal fungi of little bluestem grass [Schizachyrium scoparium (Michx.) Nash] on burned and unburned sand prairies

SUMMARYWP examined the influence of burning on little bluestem grass productivity and its vesicular‐arbuscular mycorrhizal (VAM) fungal associates in a sand prairie community over (bar growing seasons (1586‐4). Above‐and below‐ground productivity was higher on the burned sites than on the unhurried sites. Percent VAM funga1 colonization levels were significantly burned sites than on the unburned sites. In contrast, early in the growing season, colonized and specific rout lengths were longer on the burned site than on the unburned sites but differences were not always significant. Roots of plants on the burned sites supported more fungal biomass than roots on the unburned sites especially during the early growing season. However, colonization d:it;i suggest that the fungi were unable to keep up with the greater below‐ground production of plants on the burned prairies. Mycorrhizal inoculum potential levels of little bluestem rooi zone and randomly collected soil and VAM fungal spore densities were lower on the burned sites than the unburned sites during the year of the burn. Above‐ and below‐ground tissue samples showed significantly higher concentrations and accumulations of several inorganic, nutrients on the burned site early and later in the growing season.However, in contrast, plants on the unburned sites had greater nutrient‐use efficiencies for several nutrients than plants on the burned sites. Lower nutrient‐use efficiencies of plants on burned sites may in pan be due to the onset of harsher environmental conditions during the growing season and/or to associated VAM fungi‐ VAM fungi associated with plants on the burned sites are likely a carbon drain on these plants, supporting greater fungal biomass, and hence, plants on burned sand prairie sites may not benefit from their VAM fungal association especially early in the growing season.

Plant and Soil Controls on Mycorrhizal Fungal Communities

A field experiment was conducted to examine the relative importance of soil factors and plant species on communities of vesicular—arbuscular mycorrhizal (VAM) fungi. Populations of VAM fungal spores were studies in 4—yr—old monocultures of five successional grass species grown in gradient of soil mixtures ranging from pure subsurface sand to pure sandy loam topsoil. A total of 19 species of VAM fungi were found across all treatments. Of the 12 most abundant VAM fungal species, 6 species had a significant dependence on both soil mixture and host species, while 2 were dependent only on soil and 2 only on host. To our knowledge, these are the first results indicating that even closely related hosts (five grasses) may cause divergence in VAM fungal communities on initially identical soils. Cluster analysis of the similarity of fungal communities by host plant species showed that fungal communities in the two late successional grasses to be most similar to one another and least similar to the fungal communities in the early successional grass species. Cluster analysis of the similarity of fungal communities by soil mixture showed the fungal communities in the sandy end of the soil gradient diverged predictably from the fungal communities in the black soil end of the gradient. These results support the hypothesis that soil factors and plant species may be of equal importance in regulating the species composition of VAM fungal communities.

Colonization of Soybean by Mycorrhizal Fungi and Spore Populations in Iowa Soils

AbstractMycorrhizae, a mutualistic association between fungi of the family Endogonaceae and higher plants, have been studied extensively in the greenhouse, but much less is known about the natural ecology of these fungal‐plant associations in field soils. A better understanding of the mycorrhizae of agronomic crops is needed because of their potential involvement in systems of sustainable agriculture. This study reports on the extent of root colonization by mycorrhizal fungi, the distribution of mycorrhizal fungal spores in the rhizosphere, and the mycorrhizal fungal genera associated with soybean [Glycine max (L.) Merr.] in 15 Iowa soils. Results indicated that soybean roots from most soils, in spite of some soils having very high soil‐test P levels, were extensively colonized (60–100%) by vesicular‐arbuscular mycorrhizal (VAM) fungi. Colonization was determined by evaluating the percentage of root segments with VAM fungi. The average colonization of plant roots from all soils was 89%, and the average Bray P1 soil‐test value was 60.3 mg kg−1 (values greater than 30.5 are considered by the Iowa State Soil Testing Laboratory to be very high). Abundant colonization was unexpected in these high‐P fertility soils because most authors report extensive colonization to occur mainly in plants growing in soils of low fertility. The VAM fungal spores were quite common in all rhizosphere soils sampled and ranged from 66 to 998 spores 100 g−1 soil. Total spore counts were significantly different among soil series (P &lt; 0.001) and within soil series (P &lt; 0.01). A negative correlation (P &lt; 0.05) was found between soil organic matter, P, and VAM fungal colonization. For VAM fungal genera (Glomus, Gigaspora, Acaulospora, and Scutellospora) were found associated with soybean rhizosphere soil. Among these, Glomus was the most abundant.

Synergistic effects of vesicular-arbuscular mycorrhizal fungi and diazotrophic bacteria on nutrition and growth of sweet potato (Ipomoea batatas)

Sweet potatoes were micropropagated and then transplanted from axnic conditions to fumigated soil in pots in the greenhouse. Spores of Glomus clarum were obtained from Brachiaria decumbens or from sweet potatoes grown in soil infected with this fungus and with an enrichment culture of Acetobacter diazotrophicus. Three experiments were carried out to measure the beneficial effects of vesicular-arbuscular mycorrhizal (VAM) fungi-diazotroph interactions on growth, nutrition, and infection of sweet potato by A. diazotrophicus and other diazotrophs obtained from sweet potato roots. In two of these experiments the soils had been mixed with 15N-containing organic matter. The greatest effects of mycorrhizal inoculation were observed with co-inoculation of A. diazotrophicus and/or mixed cultures of diazotrophs containing A. diazotrophicus and Klebsiella sp. The tuber production was dependent on mycorrhization, and total N and P accumulation were increased when diazotrophs and G. clarum were applied together with VAM fungal spores. A. diazotrophicus infected aerial plant parts only when inoculated together with VAM fungi or when present within G. clarum spores. More pronounced effects on root colonization and intraradical sporulation of G. clarum were observed when A. diazotrophicus was co-inoculated. In non-fumigated soil, dual inoculation effects, however, were of lower magnitude. 15N analysis of the aerial parts and roots and tubers at the early growth stage (70 days) showed no statistical differences between treatments except for the VAM+Klebsiella sp. treatment. This indicates that the effects of A. diazotrophicus and other diazotrophs on sweet potato growth were caused by enhanced mycorrhization and, consequently, a more efficient assimilation of nutrients from the soil than by N2 fixation. The possible interactions between these effects are discussed.

Extensive In Vitro Hyphal Growth of Vesicular-Arbuscular Mycorrhizal Fungi in the Presence of CO 2 and Flavonols

Various flavonoids were tested for their ability to stimulate in vitro growth of germinated spores of vesicular-arbuscular mycorrhizal fungi. Experiments were performed in the presence of 2% CO(2), previously demonstrated to be required for growth of Gigaspora margarita (G. Bécard and Y. Piché, Appl. Environ. Microbiol. 55:2320-2325, 1989). Only the flavonols stimulated fungal growth. The flavones, flavanones, and isoflavones tested were generally inhibitory. Quercetin (10 muM) prolonged hyphal growth from germinated spores of G. margarita from 10 to 42 days. An average of more than 500 mm of hyphal growth and 13 auxiliary cells per spore were obtained. Quercetin also stimulated the growth of Glomus etunicatum. The glycosides of quercetin, rutin, and quercitrin were not stimulatory. The axenic growth of G. margarita achieved here under rigorously defined conditions is the most ever reported for a vesicular-arbuscular mycorrhizal fungus.

The spatial dispersion of spores of vesicular-arbuscular mycorrhizal fungi in a sand dune: microscale patterns associated with the root architecture of American beachgrass

In order to develop a model of the spatial dispersion of populations of vesicular-arbuscular mycorrhizal fungal (VAMF) spores within a root zone, we hypothesized that their spatial pattern would be correlated with the below-ground architecture (growth and structure) of the root system. Detailed excavation and mapping of the roots within the vicinity of three clusters of Ammophila breviligulata ramets (culms) revealed a network of rhizomes, many of which were not connected to the original plant. The species richness of VAMF for the three plots ranged from six to nine, including five genera. A high degree of spore clumping was not significantly correlated with the location of roots, nor with any of the physical soil parameters tested, or with the abundance of spores in adjacent sampling areas. The abundance of spores at a particular location in the soil generally was not a good predictor of spore populations only 10 cm distant. Since such spores are not readily dispersed from the point of sporulation, it is likely that some spore aggregations formed previously in association with fibrous roots that have subsequently decayed and are no longer detectable in the soil profile.