Ectomycorrhizal Fungal Community Structure of Pinyon Pines Growing in Two Environmental Extremes

Abstract

We used molecular techniques to examine the ectomycorrhizal fungal community associated with pinyon pine (Pinus edulis) growing in two soil types in a semiarid region of northern Arizona: cinder soils low in nutrients and moisture, and sandy‐loam soils with higher moisture and nutrient levels. Pinyon performance (e.g., growth, reproduction, water stress) has been shown to be markedly lower in cinder than in sandy‐loam environments. Fungal community composition and richness were determined using RFLP (restriction fragment length polymorphism) analysis of ectomycorrhizal root tips collected from three sites within each soil type. Several patterns emerged from these analyses. First, communities in both cinder and sandy‐loam soils were dominated by one or a few abundant ectomycorrhizal types, a species abundance pattern common to many plant and animal communities. Second, unlike the pattern for many other organisms, ectomycorrhizal fungal type (species) richness was not correlated with measures of ecosystem productivity such as soil nutrient and moisture levels; cinder and sandy‐loam soils had similar numbers of ectomycorrhizal fungal types (range of 15–19 fungal types for both soil types). Third, soil type and fungal community composition were linked, as cluster analysis demonstrated greater similarity of fungal communities from sites within soil types than between them. Differential amplification using primers with enhanced specificity for basidiomycetes indicated that an average of 85% of the ectomycorrhiza found at the sandy‐loam sites were members of the subphylum Basidiomycotina, whereas over half (mean = 52%) of the ectomycorrhiza at the cinder sites were formed by members of other fungal groups, probably the subphylum Ascomycotina. Fourth, a preliminary survey of 14–45 ectomycorrhizal root tips from each of 20 trees at one cinder site indicated that trees were dominated by one or a few ectomycorrhizal RFLP types. However, the same RFLP types did not dominate on all trees, and dominant types showed considerable spatial variation. Fifth, the RFLP patterns of some fungal sporocarps matched those of ectomycorrhizal root tips, but many did not, indicating that many of the ectomycorrhizal fungi at these sites fruit infrequently, whereas other fungi with more abundant sporocarps may not form ectomycorrhiza. This emphasizes the need to characterize the ectomycorrhizal communities formed on the plant roots themselves, rather than characterization based on sporocarps alone, particularly in arid environments. Finally, the differences in ectomycorrhizal fungal communities we observed between soil types supported the concept that conserving fungal diversity requires conservation of host plant species over their entire range, not just typical sites. If future studies corroborate these patterns, our results suggest that abiotically stressful environments are important to include in these conservation efforts.

Post-fire, seasonal and annual dynamics of the ectomycorrhizal community in a Quercus ilex L. forest over a 3-year period

“…Only a few of the ECM morphotypes found were abundant and well distributed; most were rare species which occurred sporadically, a common pattern reported at any taxonomic level (Baar et al 1999;Dahlberg et al 2001;Durall et al 1999;Gardes and Bruns 1996;Gehring et al 1998;Grogan et al 2000;Hagerman et al 1999;Peter et al 2001;Stendell et al 1999;Taylor 2002). Most studies on ECM community structures suggest that C. geophilum and ECM in the Russulaceae, Thelephoraceae and other resupinate fungi dominate within all ECM communities (Dahlberg 2001;Horton and Bruns 2001;Peter et al 2001).…”

Site properties have a stronger influence than fire severity on ectomycorrhizal fungi and associated N-cycling bacteria in regenerating post-beetle-killed lodgepole pine forests

“…Field studies of ECM associated with black spruce (Robertson et al 2006 ) and subalpine fir (Kranabetter et al 2009 ) also found variations in ECM community structure due to differences in moisture. A study of ECM communities from pinyon pine trees growing in different soils noted that soil type was linked to fungal community composition (Gehring et al 1998 ). A recent study (Karst et al 2011 ) found that Douglasfir seedlings from lowmoisture soils had higher levels of ectomycorrhizal colonization than those from medium and high moisture soils.…”

Fungal Diversity – An Overview

“…As with other areas of mycology, molecular studies have recently revolutionized the study of ECM fungal diversity. In addition to clarifying the discrepancy between above and belowground fungal diversity, molecular surveys also revealed ECM communities as hyperdiverse (particularly when compared to plant host diversity) and composed mostly of rare species (Gehring et al, 1998, Taylor, 2002, Avis et al, 2003, Horton & Bruns, 2005, Walker et al, 2005, Avis et al, 2008, Morris et al, 2008, Branco & Ree, 2010. Figure 5 shows the typical patterns underlying ECM fungal communities: unsaturated species accumulation curves reveal the difficulty in obtaining complete community descriptions and a rank-frequency diagrams illustrate the rarity of most species.…”