Community‐level consequences of mycorrhizae depend on phosphorus availability

Abstract

Abstract. In grasslands, arbuscular mycorrhizal fungi (AMF) mediate plant diversity; whether AMF increase or decrease diversity depends on the relative mycotrophy in dominant vs. subordinate plants. In this study we investigated whether soil nutrient levels also influence the ability of AMF to mediate plant species coexistence. First, we developed a conceptual model that predicts the influence of AMF on diversity along a soil nutrient gradient for plant communities dominated by mycotrophic and non-mycotrophic species. To test these predictions, we manipulated phosphorus to create a soil nutrient gradient for mesocosm communities composed of native prairie grasses and then compared community properties for mesocosms with and without AMF. We found that, where P was limiting, AMF increased plant diversity and productivity, and also altered community structure; however, at high P, AMF had little influence on aboveground communities. Compositional differences among treatments were due largely to a trade-off in the relative abundance of C 3 vs. C 4 species. Our study emphasizes how environmental constraints on mutualisms may govern community-and ecosystem-level properties.

Diversidade de fungos micorrízicos arbusculares em área de Caatinga, PE, Brasil

“…O alto nível de fósforo nas áreas estudadas pode ter influenciado negativamente a ocorrência dos FMA, prejudicando a colonização e a produção de glomerosporos. Em geral, solos com baixo nível de P (<40 mg dm -3 ) são mais ricos em espécies de FMA (Souza et al 2003;Collins & Foster 2009) e naqueles com concentração de fósforo >40 mg dm -3 a esporulação e a diversidade de FMA são negativamente afetados (Souza et al 2003;Hijri et al 2006;Gai et al 2009). …”

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

“…In line with this, it has been observed that AMF from less intensively managed sites are more beneficial for plant biomass production than AMF from sites of higher management intensity (Johnson, 1993;Singh et al, 2008b). However, it must be remembered that the beneficial effects of AMF decrease with increased nutrient fertility (Kiers & van der Heijden, 2006;Collins & Foster, 2009) and AMF may actually reduce plant growth at high fertility as a result of carbon loss (Smith et al, 2009). Moreover, some crops (e.g.…”

Arbuscular mycorrhiza and soil nitrogen cycling

“…Studies on AM species dependency, the weighted difference in dry weight biomass of a plant in the presence and absence of mycorrhizas, have revealed that C 4 grasses are considerably more responsive to AM fungi than C 3 grasses Harnett, 1997, 1998). Additionally, Collins and Foster (2009) were able to establish AM-free and AM-inoculated mesocosms of adequate size to address community shifts in abundance of grasses. Their targeted experimentation revealed a decline in abundance of C 4 grasses in the AM-free mesocosms with a concomitant increase of C 3 grasses (Collins and Foster, 2009).…”

“…Additionally, Collins and Foster (2009) were able to establish AM-free and AM-inoculated mesocosms of adequate size to address community shifts in abundance of grasses. Their targeted experimentation revealed a decline in abundance of C 4 grasses in the AM-free mesocosms with a concomitant increase of C 3 grasses (Collins and Foster, 2009). This shift may be one example of a more generalized change toward plants that respond positively in terms of growth.…”