Asymmetric belowground carbon transfer in a diverse tree community

Abstract

Roots of vascular plants interact with mycorrhizal fungi along withother components of the soil microbiome including nonmycorrhizal fungi, archaea, and bacteria (Högberg et al., 2008). The symbiotic interaction between the fungus and the root relies on transmission of soil-derived nutrients from the fungus to the host tree (Collins Johnson et al., 2010), increasing root absorption of water by the fungal hyphae and mediating the interaction of the root with other microbes in the soil (Aroca et al., 2007;Hestrin et al., 2019). The heterotrophic fungus benefits from the interaction by receiving carbon from the autotrophic host tree (Högberg et al., 2008). There are two main functional groups of mycorrhizae: ectomycorrhiza (EM) which do not penetrate the root cortex of the host and interact mainly with trees that are located in seasonally cold and dry climates, and arbuscular mycorrhiza (AM) whose hyphae penetrate the root cortex and interact mainly with plants that are located in seasonally warm and wet climates (Steidinger et al., 2019). Each individual tree may

Prosperity of the commons: Generalist mycorrhizal species dominate a mixed forest and may promote forest diversity by mediating resource sharing among trees

“…In the context of our mixed forest, trees A and B can represent EMF and AMF tree hosts, respectively, while mycorrhiza α , β , γ can represent EMF colonizing only EMF tree hosts, AMF colonizing only AMF tree hosts, and EMF colonizing both EMF and AMF tree hosts, respectively. Following studies that demonstrated trees’ resource sharing mediated by mycorrhiza (Klein et al 2016, Rog et al 2020), and specifically in the system studied here (Avital et al 2022, Cahanovitc et al 2022), we assumed in our model that whenever two adjacent trees are colonized by the same mycorrhizal fungi type, a mycorrhizal network is formed, enabling resource sharing between the two trees. We considered the cost to the donor tree and the benefits to the recipients, mediated by the mycorrhizal fungi (distinguishing between intra- and inter-tree-types benefits), as well as the expansion rates of the different mycorrhizal fungi types – the rate at which the hyphae grows and expands from one colonized tree to a neighboring tree, and colonizes it too ( Fig.…”

“…The computational model we constructed incorporates variability in the ability of different mycorrhizal fungal species to associate with several tree species, as well as for the ability of mycorrhizal fungi to mediate resource sharing between the tree hosts (Avital et al 2022, Cahanovitc et al 2022). We found that generalist mycorrhizal fungi can evolve even when subjected to an expansion rate disadvantage, provided that inter-tree-species cooperation is beneficial enough ( Fig.…”

“…To do so, we identified the mycorrhizal fungal community in a mixed Mediterranean forest associated with four mature tree species which were previously shown to share C in a mesocosm experimental system (i.e. growing on the same soil; (Avital et al 2022, Cahanovitc et al 2022). We investigated a high level of generalist mycorrhizal species overall, and specifically, that EMF species inhabit both EMF and AMF hosts.…”

“…To do so, we identified the mycorrhizal fungal community in a mixed Mediterranean forest associated with four mature tree species which were previously shown to share C in a mesocosm experimental system (i.e. growing on the same soil; (Avital et al 2022, Cahanovitc et al 2022). Considering the high phylogenetic diversity of tree species in the mixed Mediterranean forest (including EM-hosts and AM-hosts), we hypothesized a high level of generalist mycorrhizal species overall (Hypothesis I).…”

A dynamic rhizosphere interplay between tree roots and soil bacteria under drought stress

“…In the forest, mycorrhizal fungi, which were missing here, can have large effects too ( Meier et al, 2013 ). Specifically, C. sempervirens hosts a diversity of active arbuscular mycorrhizal species ( Avital et al, 2022 ). While the latter generally help in tree P nutrition, their activity is mostly reduced under drought.…”