Arbuscular mycorrhizal fungi (AMF) play a critical role in facilitating plant nutrient absorption as they form obligate symbioses. However, the effects of N input (e.g. N deposition and symbiotic N fixation) on AMF abundance and community composition in the karst-region grassland remain poorly understood.

The simulated N deposition experiment (N, 100 kg N ha^-1 yr^-1; P, 50 kg P ha^-1 yr^-1; NP, 100 kg N ha^-1 yr^-1 + 50 kg P ha^-1 yr^-1) and different legume species (Amorpha fruticose vs Indigofera atropurpurea) or planting densities (1.5 × 2 vs 1 × 1 m) in the grassland were set up at the Institute of subtropical agricultural (ISA) of the Chinese Academy of Science (CAS). Researchers measured the AMF abundance and community composition, as well as soil properties.

They found that, Glomus in the grassland of karst hold an absolute advantage when compared with other region. 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, suggested 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 increase AMF abundance than in control, but significantly lower in high density of I. atropurpurea.

Furthermore, nutrient availability was the main factor affected AMF abundance and community composition. These findings suggest that P became more limiting with N input, which could improve AMF abundance and alleviate soil P deficiencies.

The study was supported by the National Key Research and Development Program (2016YFC0502400), the National Natural Science Foundation of China (31670529; 31870502; 31870503), Youth Innovation Team Project of ISA, CAS (2017QNCXTD_ZJ), and CAS Youth Innovation Promotion Association (2015303).

The study entitled “Arbuscular mycorrhizal fungi abundance was sensitive to nitrogen addition but diversity was sensitive to phosphorus addition in karst ecosystems” and “Effects of different legume species and densities on arbuscular mycorrhizal fungal communities in a karst grassland ecosystem” was published in Biology and Fertility of Soils and Science of the Total Environment, respectively. Details can be found at https://link.springer.com/article/10.1007/s00374-019-01362-x; https://www.sciencedirect.com/science/article/pii/S0048969719318285.

Contact: WANG Kelin

E-mail: kelin@isa.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences