Arbuscular mycorrhizal fungi influence nutrient uptake along vertical niches in legume-grass mixtures

doi:10.17521/cjpe.2025.0272

Abstract

Abstract:

Aims Legume-grass intercropping is an important strategy for restoring degraded grasslands and improving productivity in Southwest China. Arbuscular mycorrhizal fungi (AMF) play a key regulatory role in nutrient uptake within these systems. However, the mechanism by which AMF regulates nitrogen uptake and allocation in intercropping communities composed of plants with varying rooting depths remains unclear.

Methods Based on differences in nitrogen-fixing traits and root depths, this study selected a deep-rooted legume Medicago sativa and a shallow-rooted legume Trifolium repens, intercropped with two grass species, Dactylis glomerata and Lolium perenne. Monocultures and mixtures were established with or without AMF. Using ¹⁵N labeling at two soil depths 3 cm shallow and 25 cm deep, we explored the effects of AMF on the nitrogen acquisition strategies and community functions of plants with different root depths.

Important findings Intercropping significantly increased the total community of the plant community. The combination of T. repens + D. glomerata + L. perenne performed best, increasing yield by 54.78% and 76.58% compared to T. repens or L. perenne monocultures, respectively. This highlights a significant belowground niche complementarity between shallow-rooted legumes and grasses, which enhanced resource use efficiency. Conversely, the deep-rooted M. sativa showed spatial root overlap with grasses, intensifying interspecific competition and diminishing in insignificant intercropping advantages. AMF inoculation significantly promoted biomass accumulation in the strongly mycorrhizal-dependent legumes while moderating the competitive dominance of the less-dependent grasses, thereby increasing the legume proportion within the community. Furthermore, AMF induced plasticity in root morphology, significantly increasing the root length of T. repens and L. perenne.¹⁵N tracing revealed that intercropping promoted legume nitrogen fixation rates; AMF inoculation further strengthened this process and reduced the uptake of soil ¹⁵N by legumes. Meanwhile, AMF narrowed the difference in ¹⁵N uptake by grasses across soil layers, promoting more efficient utilization of deep-soil nitrogen. AMF achieved optimal resource allocation at the community level by enhancing legumes nitrogen fixation efficiency and promoting deep soil nitrogen acquisition by grasses. This study verifies that the shallow-rooted legume + grass mixture combined with AMF inoculation is the optimal strategy for achieving belowground spatial partitioning and high aboveground yield, providing a theoretical reference for the establishment of artificial grasslands in Southwest China.

Key words: arbuscular mycorrhizal fungi (AMF), legume-grass mixture, deep root system, shallow root system, nitrogen uptake, biological nitrogen fixation, ¹⁵N labeling

WEI Li, WANG Peng-Sen, LIU Shan, FAN Rui, HUANG Nan, ZHANG Jian-Guo, Qimeilamu , GOU Yang, LIU Mo-Han, HUANG Ting, ZHOU Ji-Qiong. Arbuscular mycorrhizal fungi influence nutrient uptake along vertical niches in legume-grass mixtures[J]. Chin J Plant Ecol, 2026, 50(3): 760-773.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2025.0272

https://www.plant-ecology.com/EN/Y2026/V50/I3/760

Figures/Tables 10

Fig. 1 15N isotope labeling at various soil depths. AMF, arbuscular mycorrhizal fungi; -AMF, without AMF; +AMF, inoculation with AMF; Dg, Dactylis glomerata monoculture; Lp, Lolium perenne monoculture; Ms, Medicago sativa monoculture; Tr, Trifolium repens monoculture; Ms + Dg + Lp, Medicago sativa + Dactylis glomerata + Lolium perenne mix; Tr + Dg + Lp, Trifolium repens + Dactylis glomerata + Lolium perenne mix.

Table 1 Two-way ANOVA results of the effects of cropping system (CS), arbuscular mycorrhizal fungi inoculation (AMF), and their interaction on plant community biomass of four plant species

变量 Response variable		CS	AMF	CS × AMF
df		1/2	1	1/2
植物群落生物量 Plant community biomass
苜蓿 Medicago sativa	F	0.443	4.247	0.435
苜蓿 Medicago sativa	p	0.513	0.053	0.517
白三叶 Trifolium repens	F	67.118	9.526	1.301
白三叶 Trifolium repens	p	<0.001	0.006	0.267
鸭茅 Dactylis glomerata	F	4.940	3.113	0.212
鸭茅 Dactylis glomerata	p	0.014	0.088	0.810
黑麦草 Lolium perenne	F	20.072	1.601	0.624
黑麦草 Lolium perenne	p	<0.001	0.215	0.542

Fig. 2 Effects of culture system and inoculation with arbuscular mycorrhizal fungi (AMF) on plant community biomass (total aboveground and belowground biomass). -AMF, without AMF; +AMF, inoculation with AMF; Dg, Dactylis glomerata monoculture; Lp, Lolium perenne monoculture; Ms, Medicago sativa monoculture; Tr, Trifolium repens monoculture; Ms + Dg + Lp, Medicago sativa + Dactylis glomerata + Lolium perenne mix; Tr + Dg + Lp, Trifolium repens + Dactylis glomerata + Lolium perenne mix. Different lowercase letters denote significant differences between treatments (p < 0.05).

Fig. 3 Effects of culture system and inoculation with arbuscular mycorrhizal fungi (AMF) on plant above biomass, below ground biomass. -AMF, without AMF; +AMF, inoculation with AMF; Dg, Dactylis glomerata monoculture; Lp, Lolium perenne monoculture; Ms, Medicago sativa monoculture; Tr, Trifolium repens monoculture; Ms + Dg + Lp, Medicago sativa + Dactylis glomerata + Lolium perenne mix; Tr + Dg + Lp, Trifolium repens + Dactylis glomerata + Lolium perenne mix. The letters in parentheses indicate the aboveground biomass or belowground biomass of that specific plant species with the nixed system. CS indicates the cropping system, AMF indicates AMF inoculation, and CS × AMF indicates their interaction effect. Two-way ANOVA results are shown above each panel: *, p < 0.05; ***, p < 0.001. Different lowercase letters indicate significant differences between treatments (p < 0.05).

Fig. 4 Effects of culture system and inoculation with arbuscular mycorrhizal fungi (AMF) on plant root length. -AMF, without AMF; +AMF, inoculation with AMF; Dg, Dactylis glomerata monoculture; Lp, Lolium perenne monoculture; Ms, Medicago sativa monoculture; Tr, Trifolium repens monoculture; Ms + Dg + Lp, Medicago sativa + Dactylis glomerata + Lolium perenne mix; Tr + Dg + Lp, Trifolium repens + Dactylis glomerata + Lolium perenne mix. The letters in parentheses indicate the root length of that specific plant species within the mixed system. CS indicates the cropping system, AMF indicates AMF inoculation, and CS × AMF indicates their interaction effect. Two-way ANOVA results are shown above each panel: *, p < 0.05; **, p < 0.01; ***, p < 0.001. Different lowercase letters indicate significant differences between treatments (p < 0.05).

Fig. 5 Effects of culture systems on the intensity of mycorrhizal colonization. Dg, Dactylis glomerata monoculture; Lp, Lolium perenne monoculture; Ms, Medicago sativa monoculture; Ms + Dg + Lp, Medicago sativa + Dactylis glomerata + Lolium perenne mix; Tr, Trifolium repens monoculture; Tr + Dg + Lp, Trifolium repens + Dactylis glomerata + Lolium perenne mix. The letters in parentheses indicate the mycorrhizal colonization intensity of that specific plant species within the mixed system. Different lowercase letters indicate significant differences between treatments (p < 0.05).

Fig. 6 Effect of culture system on the mycorrhizal growth response of plant aboveground biomass. Dg, Dactylis glomerata monoculture; Lp, Lolium perenne monoculture; Ms, Medicago sativa monoculture; Ms + Dg + Lp, Medicago sativa + Dactylis glomerata + Lolium perenne mix; Tr, Trifolium repens monoculture; Tr + Dg + Lp, Trifolium repens + Dactylis glomerata + Lolium perenne mix. The letters in parentheses indicate the mycorrhizal growth response of that specific plant species within the mixed system. Different lowercase letters indicate significant differences between treatments (p < 0.05).

Fig. 7 Effects of culture system and inoculation with arbuscular mycorrhizal fungi (AMF) on nitrogen fixation ratio of legumes (Ndfa). -AMF, without AMF; +AMF, inoculation with AMF; Dg, Dactylis glomerata monoculture; Lp, Lolium perenne monoculture; Ms, Medicago sativa monoculture; Ms + Dg + Lp, Medicago sativa + Dactylis glomerata + Lolium perenne mix; Tr, Trifolium repens monoculture; Tr + Dg + Lp, Trifolium repens + Dactylis glomerata + Lolium perenne mix. The letters in parentheses indicate the nitrogen fixation rate of that specific plant species within the mixed system. CS indicates cropping system, AMF indicates AMF inoculation treatment, and Depth indicates 15N tracer depth; CS × AMF indicates their interaction. 25 cm, 15N tracer labeling at 25 cm depth; 3 cm, 15N tracer labeling at 3 cm depth. Three-way ANOVA results are shown above each panel: *, p < 0.05; **, p < 0.01; ***, p < 0.001. Different lowercase letters indicate significant differences between treatments (p < 0.05).

Fig. 8 Effects of culture system and inoculation with arbuscular mycorrhizal fungi (AMF) on aboveground plant nitrogen content. -AMF, without AMF; +AMF, inoculation with AMF; Dg, Dactylis glomerata monoculture; Lp, Lolium perenne monoculture; Ms, Medicago sativa monoculture; Ms + Dg + Lp, Medicago sativa + Dactylis glomerata + Lolium perenne mix; Tr, Trifolium repens monoculture; Tr + Dg + Lp, Trifolium repens + Dactylis glomerata + Lolium perenne mix. The letters in parentheses indicate the plant nitrogen content of that specific plant species within the mixed system. CS indicates cultivation mode and AMF indicates inoculation mode of AMF, CS × AMF is the interaction effect of the two. Two-way ANOVA results are shown above each panel: *, p < 0.05; **, p < 0.01; ***, p < 0.001. Different lowercase letters indicate significant differences between treatments (p < 0.05).

Fig. 9 Effects of culture system and inoculation with arbuscular mycorrhizal fungi (AMF) on plant uptake of tracer. -AMF, without AMF; +AMF, inoculation with AMF; Dg, Dactylis glomerata monoculture; Lp, Lolium perenne monoculture; Ms, Medicago sativa monoculture; Ms + Dg + Lp, Medicago sativa + Dactylis glomerata + Lolium perenne mix; Tr, Trifolium repens monoculture; Tr + Dg + Lp, Trifolium repens + Dactylis glomerata + Lolium perenne mix. The letters in parentheses indicate the plant tracer uptake of that specific plant species within the mixed system. CS indicates cultivation mode and AMF indicates inoculation mode of AMF, CS × AMF is the interaction effect of the two. Depth: depth of 15N tracer labeling; 25 cm, 15N tracer labeling at 25 cm depth; 3 cm, 15N tracer labeling at 3 cm depth: *, p < 0.05; **, p < 0.01; ***, p < 0.001. Different lowercase letters indicate significant differences between treatments (p < 0.05).

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