Abstract: The mycorrhizal diversity and morphological plasticity determine the adaptability of host plants to habitat changes. To understand the effects of mixture between coniferous and broadleaf trees on the morphological characteri-stics of ectomyzorrhizal (EcM) associations, we examined the influences of environmental factors on changes in morphological characteristics based on a systematic investigation of the EcM morphological traits in Pinus tabuliformis Carr. and Quercus liaotungensis Koidz. grown in pure stands as well as in various levels of mixture (i.e., P. tabuliformis and Q. liaodongensis in a 3:1 mixture, a 1:1 mixture, and a 1:3 mixture) in Taiyue Mountains of Shanxi Province. Results showed that the EcM in both species are predominantly of the contact exploration type in all stand types. In P. tabuliformis, the root tip numbers of the contact and medium-distance exploration types in mixed stands were significantly greater by 3%-10% and 10%-16%, respectively, than in pure stands. In Q. liaotungensis, the root tip numbers of the contact exploration type in mixed stands were significantly higher by 5%-10% than in pure stands. In both species, the values of Simpson morphological diversity index were higher in mixed stands than in pure stands. Redundancy analysis indicated that the morphological variability of EcM was mostly affected by soil nitrogen to phosphorus ratio (explainable by 7.5%) and soil water content (explainable by 5.2%) in P. tabuliformis, while it was mostly affected by soil carbon content in Q. liaotungensis (explainable by 3.5%). Both P. tabuliformis and Q. liaotungensis are capable of adapting to conditions with competition for, and sharing of, soil nutrients in mixed forests through morphological variations of EcM.

Key words: co-occurring habitat, ectomycorrhizae (EcM), EcM morphological trait, nutrient foraging strategy