Networks of power and influence: the role of mycorrhizal mycelium in controlling plant communities and agroecosystem functioning

Abstract

Extraradical mycelia of mycorrhizal fungi are normally the “hidden half” of the symbiosis, but they are powerful underground influences upon biogeochemical cycling, the composition of plant communities, and agroecosystem functioning. Mycorrhizal mycelial networks are the most dynamic and functionally diverse components of the symbiosis, and recent estimates suggest they are empowered by receiving as much as 10% or more of the net photosynthate of their host plants. They often constitute 20%–30% of total soil microbial biomass yet are undetected by standard measures of biomass used by soil scientists and agromomists. Mycorrhizal mycelia provide extensive pathways for carbon and nutrient fluxes through soil, often exceeding tens of metres per gram of soil. We consider the amounts of photosynthate “power” allocated to these mycelial networks and how this is used in fungal respiration, biomass, and growth and in influencing soil, plant, and ecosystem processes. The costs and functional “benefits” to plants linking to these networks are fungal specific and, because of variations in physiology and host specificity, are not shared equally; some plants even depend exclusively on these networks for carbon. We briefly assess the potential contribution of extraradical mycorrhizal mycelium to sustainable agriculture and maintenance of biodiversity and highlight technologies that promise new vistas and improved fine-scale resolution of the dynamic spatial and temporal functioning of these networks in soil.Key words: arbuscular mycorrhiza, ectomycorrhiza, extraradical mycelium, hyphal networks.

Niveles de glomalina y su relación con características químicas y biológicas del suelo (andisol) en un relicto de bosque nativo del sur de Chile

“…Además, Lovelook y Miller (2002) informan que cuando un ecosistema boscoso se encuentra dominado con vegetación asociada principalmente con hongos ectomicorrícicos el potencial de inóculo de HMA aumenta. Así, en el sotobosque especies de plantas con MA pueden sobrevivir la competencia con plantas ectomicorrícicas, probablemente debido a que las raíces de las plantas con MA podrían conectarse mediante redes fúngicas transportando carbohidratos a plantas con desventajas fotosintéticas (Leake et al 2004).…”

Colonização micorrízica e nodulação radicular em mudas de sabiá (Mimosa caesalpiniaefolia Benth.) sob diferentes níveis de salinidade

“…Hameeda et al (2007) observaram que a utilização de palha de arroz e vermicomposto de palha de arroz como adubos orgânicos nas quantidades de 5 e 10 toneladas por hectares, respectivamente não proporcionaram inibição da CM, porém resultou na redução da matéria seca das plantas, em relação às plantas não inoculadas. As divergências observadas nos diversos estudos podem ser justificadas pela elevada variabilidade na composição dos adubos orgânicos, pois materiais orgânicos pobres em nutrientes podem estimular a CM e os ricos podem inibir (BUCHER, 2007) (LEAKE et al, 2004). No caso específico dos ambientes salinos, onde a atividade microbiana é baixa (BEZERRA et al, 2010), conseqüentemente a taxa de decomposição é lenta, logo a quantidade de nutriente liberada pelo vermicomposto pode não ter sido suficiente para causar efeito na CM, pois os recursos minerais no solo, principalmente P regulam a interação entre os simbiontes.…”

Reviews and syntheses: on the roles trees play in building and plumbing the critical zone

“…Uptake of these nutrients into hyphae and roots nourishes the plants. In fact, if P is present at a low concentration, some rootassociated fungi can "biosense" P hotspots and proliferate into those locations (Leake et al, 2004). This has not been shown for other elements (Wallander and Ekblad, 2015), although upward pumping of elements such as Ca has been hypothesized (Dijkstra and Smits, 2002).…”