Different responses of absorptive roots and arbuscular mycorrhizal fungi to fertilization provide diverse nutrient acquisition strategies in Chinese fir

摘要

Absorptive roots and arbuscular mycorrhizal fungi (AMF) constitute two related pathways for plant nutrient acquisition. However, if and how soil nutrient availability can regulate the integrated pattern of roots and AMF remain unclear. We analyzed the abundance and morphology of absorptive roots and AMF as well as the intraradical AMF community composition in response to four-year nitrogen (N) and phosphorus (P) additions in a Chinese fir (Cunninghamia lanceolata) plantation. Absorptive root biomass, length density and tissue density significantly decreased, and specific root length significantly increased with P addition. However, none of these root characteristics were significantly affected by N addition. In contrast, extraradical hyphal length density in the rhizosphere soil and the ratio of hyphal length density to mycorrhizal colonization rate significantly decreased with N addition, but remained unchanged under P addition while extraradical hyphal length density in the ingrowth mesh bags significantly decreased with both N and P additions. The relative abundance of Acaulosporaceae and Gigasporaceae increased and that of Glomeraceae decreased with P, while N addition did not significantly shift AMF community composition. Our findings indicate that the responses of absorptive roots and AMF to N addition in the Chinese fir plantation differ from their responses to P addition, suggesting diverse strategies for a single tree species to adjust to multiple soil nutrient conditions.