Ectomycorrhizal (ECM) fungi form key symbioses with forest trees, strongly regulating plant nutrition and stress tolerance. This review synthesizes how ECM fungi redistribute plant-fixed carbon (C) in soil, interact with soil organic matter (SOM), and mediate the uptake and allocation of nitrogen (N), phosphorus (P) and other macro- and micronutrients. We highlight mechanisms underlying ECM enhanced organic and mineral N and P mobilization, including oxidative decomposition, enzymatic hydrolysis, and organic acid weathering. Beyond C-N-P dynamics, ECM fungi also enhance acquisition and homeostasis of elements such as K, Ca, Mg, Fe, and Zn, reshaping host nutrient stoichiometry, productivity, and soil microbial community composition. We further summarize multi-layered mechanisms by which ECM improve host plant resistance to pathogens, drought, salinity–alkalinity, and heavy metal stresses via physical protection, ion regulation, hormonal signaling, aquaporins, and antioxidant and osmotic adjustment. Finally, we outline research priorities, such as using trait-based, multi-omics, and microbiome-integrated approaches to better harness ECM in forestry and ecosystem restoration.

Ectomycorrhizal symbiosis is a cornerstone of ecosystem health, facilitating nutrient uptake, stress tolerance, and biodiversity maintenance in trees. Optimizing Pinus armandii–Tuber indicum mycorrhizal synthesis enhances the ecological stability of coniferous forests while supporting high-value truffle cultivation. This study conducted a pot experiment to compare the effects of three root nutrient regulations—Aolu 318S (containing N-P₂O₅-K₂O in a ratio of 15-9-11 (w/w%)), Aolu 328S (11-11-18), and Youguduo (19-19-19)—on the mycorrhizal synthesis of P. armandii–T. indicum. The results showed that root nutrient supplementation significantly improved the seedling crown, plant height, ground diameter, biomass dry weight, and mycorrhizal infection rate of both the control and mycorrhizal seedlings, with the slow-release fertilizers Aolu 318S and 328S outperforming the quick-release fertilizer Youguduo. The suitable substrate composition in this experiment was as follows: pH 6.53–6.86, organic matter content 43.25–43.49 g/kg, alkali-hydrolyzable nitrogen 89.25–90.3 mg/kg, available phosphorus 83.69–87.32 mg/kg, available potassium 361.5–364.65 mg/kg, exchangeable magnesium 1.17–1.57 mg/kg, and available iron 33.06–37.3 mg/kg. It is recommended to mix the Aolu 318S and 328S solid fertilizers evenly into the substrate, with a recommended dosage of 2 g per plant. These results shed light on the pivotal role of a precise N-P-K ratio regulation in fostering sustainable ectomycorrhizal symbiosis, offering a novel paradigm for integrating nutrient management with mycorrhizal biotechnology to enhance forest restoration efficiency in arid ecosystems.