Mycorrhizal symbiosis pathway and edaphic fertility frame root economics space among tree species

Abstract

The root economics space (RES) is multidimensional and largely shaped by belowground biotic and abiotic influences. However, how root-fungal symbioses and edaphic fertility drive this complexity remains unclear.Here, we measured absorptive root traits of 112 tree species in temperate and subtropical forests of China, including traits linked to functional differences between arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) hosts.Our data, from known mycorrhizal tree species, revealed a 'fungal-symbiosis' dimension distinguishing AM from ECM species. This divergence likely resulted from the contrasting mycorrhizal evolutionary development of AM vs ECM associations. Increased root tissue cortical space facilitates AM symbiosis, whereas increased root branching favours ECM symbiosis. Irrespective of mycorrhizal type, a 'root-lifespan' dimension reflecting aspects of root construction cost and defence was controlled by variation in specific root length and root tissue density, which was fully independent of root nitrogen content. Within this function-based RES, we observed a substantial covariation of axes with soil phosphorus and nitrate levels, highlighting the role played by these two axes in nutrient acquisition and conservation.Overall, our findings demonstrate the importance of evolved mycorrhizal symbiosis pathway and edaphic fertility in framing the RES, and provide theoretical and mechanistic insights into the complexity of root economics.

Short-term responses of root exudation C and functional traits to drought of five temperate tree species

“…The concept that root traits are not simply analogues of leaf traits along a one-dimensional economics spectrum, i.e., a classical fast-slow "conservation" gradient (Bergmann et al 2017), but depend upon a multidimensional space (Kramer-Walter et al 2016;Bergmann et al 2020). In which, mycorrhizal fungal collaboration was suggested to dominate the root economics space (Bergmann et al 2020;Yan et al 2022). Negative correlation between mycorrhizal colonization and root exudation C and NSC were expected because greater mycorrhizal colonization would consume more C, including the interception of mycorrhizal hyphae or/and fascicles arbuscular, and respiratory metabolism (Kaiser et al 2015;Wen et al 2021).…”

The worldwide allometric relationship in anatomical structures for plant roots

“…However, large stomatal conductance will enhance the transpiration water loss, as such causing physiological drought to plants (Khan et al, 2007; Wang et al, 2018). The surge of leaf vein density in angiosperms since the mid-Cretaceous, hence resulting more efficient water supply to the mesophyll cell for photosynthesis, can be considered as evidence for plant adaptation to the physiological drought (Baraloto et al, 2010; Feild et al, 2011; Baird et al, 2021; Yan et al, 2022).…”

“…The core function of plant roots is to absorb soil water and nutrients, which is undertaken by a few terminal root branch orders, i.e., absorptive roots, mainly bearing primary root tissues (Guo et al, 2008b). Generally, the absorptive function is depicted by a range of traits in root morphology, physiology, anatomy, chemistry, mechanics and microbial symbiosis (McCormack et al, 2017; Wambsganss et al, 2021; Wen et al, 2022; Yan et al, 2022). Among these root traits, root diameter seems like the most important one given that it is closely associated with a suite of other root traits as well as mycorrhizal fungi apart from its well-known feature of easily measured and great inter-specific variation (Eissenstat et al, 2015; Li et al, 2018; Bergmann et al, 2020; Wen et al, 2022).…”

Phosphorus acquisition strategies of arbuscular mycorrhizal and ectomycorrhizal trees in subtropical plantations

“…As reported by Bergmann et al (2020) in their root economics space framework, plants with high specific root lengths adopt a do‐it‐yourself strategy, while plants with high rates of mycorrhizal colonisation favour an outsourcing strategy. Arbuscular mycorrhizal species have been reported to have thick roots with a thick cortex, while EM species have high root branching density (Comas et al, 2014; Yan et al, 2022). Plants with a high root tissue density tend to acquire resources slowly, while roots with a high N content tend to acquire resources rapidly (Bergmann et al, 2020).…”