Global Distributions of Arbuscular Mycorrhizal Fungi

Abstract

We examined potential large-scale controls over the distribution of arbuscular mycorrhizal (AM) fungi and their host plants. Specifically, we tested the hypothesis that AM fungi should be more prevalent in biomes where nutrients are primarily present in mineral, and not organic, forms. Values of percentage root length colonized (%RLC) by AM fungi, AM abundance, and host plant availability were compiled or calculated from published studies to determine biome-level means. Altogether, 151 geographic locations and nine biomes were represented. Percent RLC differed marginally significantly among biomes and was greatest in savannas. AM abundance (defined as total standing root length colonized by AM fungi) varied 63-fold, with lowest values in boreal forests and highest values in temperate grasslands. Biomes did not differ significantly in the percentage of plant species that host AM fungi, averaging 75%. Contrary to the hypothesis, %RLC, AM abundance, and host plant availability were not related to the size, influx, or turnover rate of soil organic matter pools. Instead, AM abundance was positively correlated with standing stocks of fine roots. The global pool of AM biomass within roots might approach 1.4 Pg dry weight. We note that regions harboring the largest stocks of AM fungi are also particularly vulnerable to anthropogenic nitrogen deposition, which could potentially alter global distributions of AM fungi in the near future.

Occurrence and species richness of mycorrhizal fungi in soil under different land use

“…The number of AMF species found in this study was added to those already compiled by Stürmer and Siqueira (2006), and increased to 63, the number of AMF species registered to Cerrado and reinforces that tropical savanna ecosystems might hold a large diversity of AMF compared with other biomes in the world. Production of fine root biomass that is significantly higher in savannas relative to other biomes, influences AMF abundance (Treseder and Cross 2006), and the species' richness might be one factor that accounts for this high diversity. Our results also highlight the importance in conserving native areas of Cerrado, to shelter The first record of this species in the biome Cerrado.…”

Fungal Traits That Drive Ecosystem Dynamics on Land

“…In addition, ectomycorrhizal root tips and rhizomorphs can be long-lived and slow to decompose (45,(251)(252)(253)(254)(255)(256)(257), which can contribute to microbial immobilization of C, N, and P. Altogether, mycorrhizal fungi may augment soil C storage (30,42,255,258,259). Moreover, their abundance is influenced not only directly by climate and nutrient availability but also by the presence and activities of host plants (260)(261)(262). For instance, mycorrhizal fungi often decline upon exposure to anthropogenic N enrichment, ostensibly because host plants reduce their investment in mycorrhizal fungi when soil nutrients become less limiting to plant growth (reviewed in reference 263).…”

Positive effects of organic farming on below‐ground mutualists: large‐scale comparison of mycorrhizal fungal communities in agricultural soils

“…Among ecosystems in which AMF have been studied, agricultural sites have typically been the poorest in AMF diversity (Oehl et al, 2003;Ö pik et al, 2006), although AMF abundance can be high (Treseder & Cross, 2006) and specific outcomes depend strongly on the study site (compare, for example, Helgason et al (1998), Daniell et al (2001) and Hijri et al(2006)). In small-scale direct comparisons, organic management has been shown to enhance AMF richness (Oehl et al, 2003;Hijri et al, 2006) and colonization levels (Bending et al, 2004), but it is not yet known whether organic management, in general, stimulates AMF diversity or abundance.…”