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.
Highlights
Grasslands are important ecosystems, as they provide a major food source, while preserving plant and animal diversity and offering additional ecosystem services, such as resource storage, soil protection, and recreational opportunities (White et al, 2000; Unger and Jongen, 2015)
Phosphorus addition may be one of the key factors enhancing the abundance of legumes and their ability to promote grass growth by nitrogen input into the system, with the soil nitrogen and phosphorus stoichiometry being determinant for positive long-term effects and sustainability of the SBP practice
We hypothesized that Arbuscular mycorrhizal fungi (AMF) would promote the competitive ability of the legume (i.e., T. subterraneum) over the grass (i.e., L. multiflorum), as phosphorus uptake via the AMF pathway should be more efficient than via the direct root pathway (Smith et al, 2011) and Trifolium should absorb more P by AMF hyphae than by its coarse root system (Sprent and James, 2007; Saia et al, 2014; Unger et al, 2016), while Lolium should be less colonized and rely more on root P uptake (Reinhart et al, 2012; Friede et al, 2016; Unger et al, 2016)
Summary
Grasslands are important ecosystems, as they provide a major food source, while preserving plant and animal diversity and offering additional ecosystem services, such as resource storage, soil protection, and recreational opportunities (White et al, 2000; Unger and Jongen, 2015). Seed mixtures of highly productive legumes and grasses are introduced in semi-natural pastures in order to increase soil nitrogen availability and improve productivity (Teixeira et al, 2015) This practice has been successful, with studies showing enhanced productivity in SBP, as compared to semi-natural pastures (Carneiro et al, 2008; Hernández-Esteban et al, 2019), thereby significantly increasing the sustainable stocking rates and providing animals with forage of higher nutritional value and plant digestibility. Phosphorus addition may be one of the key factors enhancing the abundance of legumes and their ability to promote grass growth by nitrogen input into the system, with the soil nitrogen and phosphorus stoichiometry being determinant for positive long-term effects and sustainability of the SBP practice
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