Ectomycorrhizal Diversity Research Articles

Some Effects of N on Ectomycorrhizal Diversity of Scots Pine ( Pinus sylvestris L.) in Northeastern Germany

In the last three decades high industrial nitrogen (N) emissions have led to eutrophication of a Scots pine stand (Pinus sylvestris [L.]) near Schwedt characterized by a broad cover of Calamagrostis epigejos [L.] Roth (Poaceae). In comparison to the relatively unimpacted control site (low N site), this high N site showed a remarkably low mycorrhizal frequency (percentage of mycorrhizas on total amount of root tips) with seasonal lows down to 27 %. At the low N site the highest number of mycorrhizal root tips was found in the organic layer. At the high N site the amount of mycorrhizas per soil volume was similar in both organic and mineral soil layers, and also significantly lower when compared to the amount at the low N site. The high N site revealed only nine mycorrhizal morphotypes instead of eighteen found at each sampling date at the control site. 80 % of the coenosis at the high N site were represented by only four morphotypes resulting in a low diversity. The seasonal decrease in the mycorrhizal frequency, the small amount of mycorrhizas and the low diversity suggest that the high N deposition at this site has reduced the ability of the pine trees to withstand natural stresses such as prolonged drought or frost periods. This corresponds well with the 42 % reduction in tree stocking density at the high N site compared to the low N site.

Diversity of ectomycorrhizal fungi in Britain: a test of the species–area relationship, and the role of host specificity

The host range of ectomycorrhizal (ECM) fungi in Britain was examined by compilation of a data matrix from published literature sources, based primarily on accounts of sporocarp associations with particular host genera. Information was gathered for 577 species of ECM fungi belonging to 51 genera, and 25 genera of host trees, representing the majority of ECM fungal species and host genera recorded in Britain.Pronounced variation was recorded in the number of ECM fungal species associated with different host genera, with over 200 species recorded with Betula, Fagus, Pinus and Quercus. There was a positive linear relationship (r2=0·47, P=0·007) between the number of species of ECM fungi associated with different host genera and the total area occupied by each tree genus in Britain (both values log‐transformed). There was also variation in the number of species of ECM fungi which were apparently specific to particular host genera, values ranging from zero (in 15 genera) to >40 in the case of Betula and Fagus. In total, 233 fungal species appeared to be specific to a single host genus (i.e. 40% of those surveyed). Comparison of the ECM mycota associated with different host genera by PCA accounted for 17% of the total variation, with genera belonging to the Fagaceae (Quercus, Fagus and Castanea) tending to cluster together, indicating a degree of overlap in their ECM associates. Exotic conifer species, which displayed a lower ECM diversity than would be expected from their distributional areas, were characterized by a high degree of overlap with the ECM associates of Pinus and Betula.These results indicate that the abundance of different genera of host trees and variation in host specificity could provide a basis for understanding patterns of diversity in ECM fungi within Britain.

Soil transfers from valley oak (Quercus lobata Nee) stands increase ectomycorrhizal diversity and alter root and shoot growth on valley oak seedlings

Soils from valley oak (Quercus lobata Nee) riparian areas of the Cosumnes River Nature Conservancy Preserve near Sacramento, California were added to growth medium of valley oak seedlings grown in a greenhouse or in agricultural fields at Cosumnes which probably once supported valley oak trees and are now replanted with native riparian vegetation or allowed to revegetate naturally. Agricultural field soil from the Cosumnes River Preserve was presumed to be low or lacking in ectomycorrhizal inoculum. The study was designed to (1) determine whether valley oak stand soil transfer could cause mycorrhizal infection on valley oak seedlings in an agricultural field and in a greenhouse, (2) describe ectomycorrhizal morphological types formed on valley oak seedlings, and (3) determine whether seedling growth is enhanced more by transfer of natural valley oak stand soil than agricultural field soil. In the field study, transfer of forest soil increased average ectomycorrhizal diversity (2.4 types) more than transfer of agricultural field soil (1.2 types). Valley oak seedlings were responsive to ectomycorrhizal infection in the field study. With increase in mycorrhizal infection there was an increase in shoot growth at the expense of root growth. In the greenhouse study, both percent mycorrhizal infection and mycorrhizal diversity were increased more by transfer of oak forest and woodland soils than agricultural field soil. Eight morphotypes occurred on seedlings in forest and woodland soils but only three morphotypes in agricultural soil. This result strongly suggests that the agricultural field also harbors ectomycorrhizal propagules but forest and woodland soils support a more abundant and diverse ectomycorrhizal flora.

Ectomycorrhizal diversity on Betula papyrifera and Pseudotsuga menziesii seedlings grown in the greenhouse or outplanted in single-species and mixed plots in southern British Columbia

Habituellement, le potentiel d'inoculum et la diversite des champignons ectomycorhiziens sur un site diminuent suite a la recolte. L'objectif de cette etude consistait a determiner si la plantation d'un melange d'especes d'arbres suite a la coupe permettrait de maintenir une plus grande diversite de champignons ectomycorhiziens que la plantation d'une seule espece. Le bouleau a papier (Betula papyrifera Marsh.) et le douglas taxifolie (Pseudotsuga menziesii (Mirb.) Franco) furent plantes seuls ou en melange, dans differentes proportions et densites, dans trois sites situes dans la zone continentale au sud de la Colombie-Britannique. Dans le cas de l'essai au champ, les types d'ectomycorhizes furent caracterises apres un examen morphologique detaille de 12 semis par parcelles, 4, 16 et 28 mois apres la plantation. Les champignons mycorhiziens Thelephoia, la race E, Rhizopogon (sur le douglas taxifolie uniquement), Mycelium radicis atrovirens et Cenococcum etaient les plus abondants. La dominance de Thelephora a diminue au cours de la periode d'echantillonnage de 82 a 41% des ectomycorhizes chez le bouleau et de 26 a 15% chez le douglas taxifolie. Rhizopogon est demeure aussi abondant chez le douglas taxifolie (de 36% des ectomycorhizes a 4 mois jusqu'a 37% a 28 mois). Vers le 28 e mois, 91% des mycorhizes chez le bouleau et 56% chez le douglas taxifolie etaient communes aux deux especes. Cela a d'importantes implications dans le transfert potentiel des nutriments et du carbone entre les deux especes. A 16 (P = 0,068) et 28 (P = 0,088) mois apres la plantation, l'homogeneite de la population d'ectomycorhizes associee au systeme racinaire du douglas taxifolie etait plus grande dans les parcelles ou il y avait un melange d'especes que dans celles ou il n'y avait qu'une seule espece. La richesse (nombre de types d'ectomycorhizes) et l'indicc de diversite de Simpson par semis n'etaient pas affectes par le melange des especes d'arbre. La densite de la plantation n'a pas affecte la richesse, l'homogeneite ou la diversite. Les ectomycorhizes qui se sont developpes sur les semis de douglas taxifolie ou de bouleau cultives en serres dans des sols provenant de ces sites etaient tres semblables a ceux qui se sont developpes sur le terrain. Cela demontre qu'on peut faire des essais en serres pour predire quel type d'ectomycorhizes se formeront sur les semis cultives sur des sites perturbes, au moins pour les quelques premieres annees apres la plantation.

Ectomycorrhizal diversity on <I>Betula papyrifera</I> and <I>Pseudotsuga menziesii</I> seedlings grown in the greenhouse or outplanted in single-species and mixed plots in southern British Columbia

Ectomycorrhizal diversity on <I>Betula papyrifera</I> and <I>Pseudotsuga menziesii</I> seedlings grown in the greenhouse or outplanted in single-species and mixed plots in southern British Columbia

Spatial patterns of mycorrhizal infectiveness of soils long a successional chronosequence

This study quantified intersite variation and spatial pattern in arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) infectivity of soils among six sites constituting a successional chronosequence in southwestern Ohio, USA. The study sites included an active agricultural field (chronic disturbance), a site which had been stripped of its surface soil (pseudo-stripmine, acute disturbance), 5- and 10-year-old fields, a 25- to 30-year-old prairie restoration, and an undisturbed, mature forest. AM infectivity was lower in the agricultural field, successional fields, and prairie than in the mature forest, but there was no clear correlation between time since disturbance and the overall level of AM infectivity. Spatial structure in AM infectivity decreased with time since disturbance. In the pseudo-stripmine site and active soybean field, semivariance analysis attributed 44–50% of the total variance in AM infectivity among samples to spatial structure, whereas spatial dependancy accounted for only 18% of total variance in the mature forest. Kriging of AM infectiveness demonstrated small, isolated areas in the disturbed plots that were devoid of AM infectiveness, whereas the kriged AM maps of the other four sites showed AM infectiveness to become progressively more homogeneous. ECM infectiveness was lacking from 35–50% of the samples from the disturbed sites, and both overall ECM infectiveness and ECM diversity increased with time since disturbance. Approximately 44% of the variance in ECM infectiveness was related to spatial structure in the two disturbed sites, and large areas entirely devoid of ECM infectivity were present on the kriged ECM maps for these sites. There was less spatial structure in ECM in the old fields and prairie and very little in the mature forest. The results of this study emphasize the need to explicitly evaluate spatial heterogeneity in mycorrhizal infectivity in studies of the role of mycorrhizae in succession.

Characterization of Picea abies (L.) Karst. ectomycorrhizas: discrepancy between classification according to macroscopic versus microscopic features

In a 3-year study of ectomycorrhizal diversity in 2 Norway spruce stands in Switzerland the macroscopically classified ectomycorrhizal types were analyzed microscopically to compare the results of the 2 approaches. A total of 22 ectomycorrhizal types were macroscopically classified in the 2 stands. Microscopic investigations — particularly of mantle structures — resulted in the identification of 7 additional types to give a total of 29. These additional types resulted from separation of macroscopically identical types occurring on both stands (type-pairs) at the microscopic level. The problematic nature of characterization and classification of ectomycorrhizas is discussed.