Abstract
Arbuscular mycorrhizal (AM) fungi can establish mutualistic symbioses with most terrestrial plants and therefore play a crucial role in the re-vegetation and rehabilitation of degraded ecosystems. Yet, little information is available on AM fungal communities associated with dominant tree species in the semi-arid region of the Loess Plateau, Northwest China. In this study, topsoil (0–20 cm) and subsoil (20–40 cm) samples were collected from the rhizosphere of five dominant tree species in northern Shaanxi Province, to investigate the distribution and diversity of their associated AM fungi. The tree species were Hippophae rhamnoides Linn., Juniperus communis L., Populus cathayana Rehd., Robinia pseudoacacia L., and Salix matsudana Koidz. In total, 24 AM fungal species of eight genera were isolated from the rhizosphere soil samples and identified based on their spore morphology. Funneliformis and Funneliformis monosporum were respectively the most abundant genus and species of AM fungi. The distribution and diversity of AM fungi differed among the five tree species and also between the two soil depths. Across different tree species, the spore density of AM fungi varied from 2.85 to 15.32 spores g−1 fresh soil, with a species richness of 3–7, Shannon–Wiener index of 0.81–1.08, and evenness index of 0.30–0.53. The mycorrhizal colonization rate had a significant negative correlation with both the Shannon-Wiener index and species richness, whereas it was positively correlated with the evenness index. Permutational multivariate analysis of variance, non-metric multidimensional scaling, and structural equation modeling revealed that tree species, rather than soil depth or its interactions with tree species, had significant effects on the composition of AM fungal communities. In conclusion, the distribution and diversity of AM fungi associated with the dominant tree species were mainly affected by host tree species identity in the semi-arid ecosystem. Claroideoglomus etunicatum (W.N. Becker & Gerdemann) C. Walker & A. Schüßler and Glomus reticulatum Bhattacharjee & Mukerji appeared to be promising candidates for ecological restoration in the Loess Plateau region because of their adaptation to its semi-arid conditions with a broad spectrum of host tree species.
Highlights
The semi-arid Loess Plateau (Shaanxi Province, northwest China) is a natural mountainous region characterized by complex topographical and geological conditions
This study investigated the effects of host tree species and soil depth on Arbuscular mycorrhizal (AM) fungal communities by detecting their species composition in rhizosphere soils obtained from five dominant tree species in the semi-arid region of the Loess Plateau
The highest mycorrhizal colonization rate was found under R. pse at the 0–20 cm soil depth, while the lowest rate was observed under S. mat at the 20–40 cm depth
Summary
The semi-arid Loess Plateau (Shaanxi Province, northwest China) is a natural mountainous region characterized by complex topographical and geological conditions. Drought stress is a pervasive phenomenon throughout this region, which often negatively impacts vegetation restoration projects [1,2]. In such arid and semi-arid areas, the availability of soil nutrients and water for plants is largely limited under drought stress conditions [3]. Colonization by AM fungi can increase plant survival and growth in adverse environments by delivering mineral nutrients (especially phosphate) from soil to the host plant, and enhancing plant resistance to biotic (e.g., pathogens and nematodes) and abiotic stresses (e.g., drought, salinity, and heavy metals) [7]. The symbiosis between AM fungi and particular tree species could be a key ecological factor determining trees’ survival and adaptation under drought stress [9]
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