Arbuscular mycorrhizal fungi (AMF) play a critical role in facilitating plant nutrient absorption as they form obligate symbioses. However, the effects of nitrogen (N) input (e.g. N deposition and symbiotic N fixation) on AMF abundance and community composition in the karst-region grassland remain poorly understood.
Researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences (CAS) simulated N deposition experiment (N, 100 kg N ha-1 yr-1; phosphorus (P), 50 kg P ha-1 yr-1; NP, 100 kg N ha-1 yr-1 + 50 kg P ha-1 yr-1) and legume species (Amorpha fruticose vs Indigofera atropurpurea) under different planting densities in the grassland. They measured the AMF abundance and community composition, as well as soil properties.
They found that, Glomus in the grassland of karst held an absolute advantage when compared with other regions. AMF community composition changed substantially between December and July but did not respond to fertilization. N addition significantly increased AMF abundance and P addition significantly increased AMF diversity, suggesting that AMF abundance was sensitive to N addition but diversity was sensitive to P addition in the grassland.
Besides, the interaction between legume species and density had a significant effect on AMF abundance and community composition. Low densities of leguminous shrubs significantly increased AMF abundance than in control, but the AMF abundance significantly lowered in high density of I. atropurpurea.
Furthermore, nutrient availability was the main factor that affected AMF abundance and community composition. These findings suggested that P became more limiting with N input, which could improve AMF abundance and alleviate soil P deficiencies.
Related studies, published in Biology and Fertility of Soils and Science of the Total Environment, respectively, were supported by the National Key Research and Development Program, the National Natural Science Foundation of China, Youth Innovation Team Project of ISA, CAS, and Youth Innovation Promotion Association of Chinese Academy of Sciences.
Fungi are one of the five pillars of biodiversity in the ecosystem and occupy a wide range of ecological niches. XU Jianchu's research team from Kunming Institute of Botany has been engaged in fungal taxonomy and fungal ecology research since 2010.
Scientists had previously hypothesized that forest diversity resulted from a "rare-species advantage" driven by pathogenic, or harmful, fungi. The more trees there were in an area, the more quickly such fungi would accumulate on tree roots, the common model claimed. Now, new research suggests that beneficial fungi are closely involved as well. A Chinese-led team recently reported in Science that symbiotic fungi, which associate tightly with roots and help trees by exchanging nutrients, alter the rate that pathogenic fungi accumulate in the soil.
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