Arbuscular Mycorrhizal Fungi and Nutrition Determine the Outcome of Competition Between Lolium multiflorum and Trifolium subterraneum

Abstract

Arbuscular mycorrhizal fungi (AMF) may affect competitive plant interactions, which are considered a prevalent force in shaping plant communities. Aiming at understanding the role of AMF in the competition between two pasture species and its dependence on soil nutritional status, a pot experiment with mycorrhizal and non-mycorrhizal Lolium multiflorum and Trifolium subterraneum was conducted, with manipulation of species composition (five levels), and nitrogen (N)- and phosphorus (P)- fertilization (three levels). In the non-mycorrhizal state, interspecific competition did not play a major role. However, in the presence of AMF, Lolium was the strongest competitor, with this species being facilitated by Trifolium. While N-fertilization did not change the competitive balance, P-fertilization gave Lolium, a competitive advantage over Trifolium. The effect of AMF on the competitive outcome may be driven by differential C-P trade benefits, with Lolium modulating carbon investment in the mycorrhizal network and the arbuscule/vesicle ratio at the cost of Trifolium.

Competitive interactions in two different plant species: Do grassland mycorrhizal communities and nitrogen addition play the same game?

“…Numerous studies have stated that the suppression of AMF colonization might impact the growth of host plants, leading to alteration in plant interactions (Qiao et al, 2016). In line with these findings, many studies have showed that higher competitive ability is associated with more excellent mycorrhizal growth responses of interspecific competitive interaction (Jansa et al, 2008;Johnson, 2010;Unger et al, 2021), consequently the simultaneous responses by N-addition and AMF and their interactions can affect plant nutrient uptake and acquisition.…”

“…However, earlier research has confirmed that the mixed AMF inoculum treatment is more beneficial to the host than a single-species inoculum ( Boyer et al., 2015 ; Armada et al., 2016 ). Due to the differences in growth strategies and nutrient acquisition by the competing plant species, it is hard to unravel the mechanisms by mycorrhizal fungi, which might alter plant performance in interspecific competition ( Smith and Read, 2008 ; Unger et al., 2021 ). Recently, the specific mechanisms related to AMF colonization and its effects on the host and non-host plants to compete with N-addition have not been well approached.…”

“…Worldwide application of N may have caused significant changes in aboveground plant diversity and production and the composition and diversity of underground microbial community ( Zhou et al., 2016 ; Qin et al., 2022 ). The efficacy of grassland may be affected by competitions between legume and non-legume plants, due to the changes in availability of macronutrients, particularly phosphorus (P) and N. During plant competition, plant biomass and abundance are inhibited by N enrichment, and P is usually more effective in enhancing the competitiveness of legume plants than N addition ( Unger et al., 2021 ). Furthermore, N-addition may weaken plant-microbe interactions, induce dormancy, and causes indigenous destruction of vulnerable functional grouping of microbes ( Kearns et al., 2016 ; Jiang et al., 2018 ).…”

“…The mycorrhizal symbiotic association with plant roots may also improve plants ability to protect themselves against several types of biotic and abiotic stresses and root pathogens ( Lewandowski et al., 2013 ; Zhou et al., 2022 ; Bahadur et al, 2019a ). Recently, numerous studies have reported that N-addition will reduce AMF community diversity and abundance ( Chen et al., 2017 ; Williams et al., 2017 ); nonetheless, positive or even neutral effects of N-addition have also been reported in various studies ( Zheng et al., 2014 ; Unger et al., 2021 ). For instance, a field experiment conducted in Qinghai-Tibet Plateau reports that AMF spore density is not affected by N-addition, while the extraradical hyphal density dramatically increases ( Zheng et al., 2016 ).…”