Ectomycorrhizal Associations of the Dipterocarpaceae

Abstract

Dipterocarps are one of the most important tree families in the lowland forests of Southeast Asia and are somewhat unusual among tropical trees in that they form ectomycorrhizal (EcM) symbiotic root-inhabiting fungal associations. It has been hypothesized that dipterocarps have been partnered in this mutualistic association prior to the separation of Gondwana. Under many conditions EcMs form rapidly on dipterocarp seedlings through inocula present in the soil, although few studies have been conducted to provide evidence that they improve seedling establishment and performance. There are hundreds of EcM species associated with dipterocarps. Fungal fruit body surveys suggest that the most important families are Amanitaceae, Boletaceae, and Russulaceae, although Thelephoraceae also become numerically important when root tips are examined. EcM communities are affected by various biotic and abiotic factors, as well as anthropogenic perturbations, and the importance of these in structuring EcM communities is examined herein.

Responses of Soil Fungi to Logging and Oil Palm Agriculture in Southeast Asian Tropical Forests

“…For example, the high relative abundance of the Russulales and Thelophorales in the forest EcM fungal communities appears to be a generalized phenomenon, as these lineages are also abundant in other tropical EcM surveys from the Neotropics and the African tropics [85][86][87], as well as in temperate and boreal EcM forests [57,88]. In other studies from dipterocarp forests, the Russulales and Thelophorales were prevalent in root tips [34,89,90], and the Russulales were abundant in sporocarp surveys, implying some correspondence in taxonomic composition between bulk soil, root tip, and fruiting body data. The reasons for the success of these EcM fungal lineages have not been determined but may be related to high diversity in their foraging strategies [91] and enzymatic functions [92].…”

“…The Dipterocarpaceae is the dominant tree family in these lowland tropical forests, and all known species (~500) form associations with ectomycorrhizal (EcM) fungi that play key roles in influencing tree growth and survival [34,35]. Therefore, a loss of EcM fungal inoculum from soils may impede the regeneration of these forests [36], which will lead to cascading extinctions across other trophic groups dependent on dipterocarp forests for survival.…”

Variation in leaf and soil δ15N in diverse tree species in a lowland dipterocarp rainforest, Malaysia

“…In fact, in other biomes, including Amazonian seasonal dry tropical forest, plant life forms significantly affect leaf d 15 N values (Schulze et al 1994;Houlton et al 2006;Ometto et al 2006). Although lowland tropical rainforest in Southeast Asia shows extremely high tree species diversity (Whitmore 1984; Ashton 2014), little is known about the N sources and N-uptake strategies that relate mainly to root symbiotic microorganisms of most tree species, except for upper canopy dipterocarp species (Dipterocarpaceae) that are characterized by EcM root symbiosis (Lee et al 2002;Slik et al 2003;Brearley 2012). Thus, we hypothesized that tree species in tropical rainforest in Southeast Asia have diverse leaf d 15 N values, because high competition for the uptake of soil N among diverse tree species may promote various strategies of nitrogen acquisition from different N sources.…”

Dispersion, an Important Radiation Mechanism for Ectomycorrhizal Fungi in Neotropical Lowland Forests?

“…Recent studies indicate that trends in EcM fungal biodiversity are not simply driven by a latitudinal gradient . Biodiversity depends on the forest type under study (Brearly, 2011;Smith et al, 2011) and is also influenced by host identity (Haug et al, 2005;Tedersoo et al, 2010a). Amongst the EcM surveys in Dipterocarpaceae vegetation (see Brearly, 2011 review and references therein), comparisons could be made with a SE Asian Mixed-dipterocarp forest (Peay et al, 2010), where diversity was measured in plot size identical to this study.…”