Extracellular Enzyme Activity and Nutrient Characteristics of Pinus massoniana Lamb. Families with Different Growth Levels: Insights into the Ectomycorrhizal Fungal Community and Rhizosphere Soil

The symbiosis between ectomycorrhizal (ECM) fungal species and the root system of Pinus massoniana is important for its growth. However, the characteristics of ECM fungal communities and their relationships with extracellular enzyme activities and nutrients in the rhizosphere soil of different P. massoniana genotypes have not been well characterized. In this study, P. massoniana families (groups of offspring from different parents) with different levels of growth were selected for investigating ECM fungal communities, soil nutrients, extracellular enzyme activity, and leaf nutrient concentrations to explore the relationships between P. massoniana and the composition of the ECM fungal community. The high-growth (HG) family of P. massoniana had more different ECM fungal communities than the medium-growth (MG) and low-growth (LG) families; each family had a unique and dominant genera (HG: Amphinema and Pseudoclathrosphaerina; MG: Russula and Auricularia; and LG: Russula and Amanita). Amphinema was the main contributor to the differences among the three families (contribution: HG-MG 0.225 and HG-LG 0.17) and had rich extramatrical mycelium, which favored the growth of the HG family and positively affected the accumulation of soil organic carbon. Structural equation modelling showed that the dominant genera in the HG family had significant positive effects on the activity of three extracellular enzymes (BG, NAG, and AP) (weak to moderate positive effects of Amphinema on BG, NAG, and AP and moderate positive effects of Pseudoclathrosphaerina on BG, NAG, and AP), which might have contributed to the differences in extracellular enzyme activities among the families with different growth levels. Redundancy analysis indicated that P. massoniana growth traits (tree height, diameter at breast height, and timber volume), soil total nitrogen, and the N/P ratio significantly influenced ECM fungal communities. The study revealed the characteristics of ECM fungal communities, soil extracellular enzyme activity, and nutrient features of P. massoniana with different growth levels, which help improve our understanding of the relationship between P. massoniana genotype and ECM fungal communities.