Coupled Effects of Tree Species and Understory Morel on Modulating Soil Microbial Communities and Nutrient Dynamics

Morel mushrooms (<i>Morchella</i> spp.) are highly prized for their culinary and economic value. Understory cultivation, leveraging the symbiotic relationship between morels and trees, has gained increasing popularity. However, the effects of this practice on belowground microbial communities and nutrient dynamics remain poorly understood. In this study, we examined how understory cultivation of morels (<i>Morchella sextelata</i>) under five different tree species affects soil bacterial and fungal communities, as well as nutrient availability and mineral element content. The results revealed that soil physicochemical properties responded variably to morel cultivation under different tree species. Notably, understory morel cultivation reduced soil NO₃^--N by 38-67% across tree species, whereas NH₄⁺-N remained stable, reflecting the distinct nutrient preference of <i>Morchella</i> and associated trees, and suggesting targeted nitrate fertilization could mitigate nitrogen limitations. Understory cultivation significantly increased soil mineral elements, with <i>Zelkova serrata</i> (<i>Z. serrata</i>) showing the highest concentrations, elevating available potassium (AK), calcium (ECa), manganese (AMn) and boron (AB) by approximately 20%, 13%, 30%, and 168%, highlighting its potential for soil quality improvement. Microbial community composition was also significantly altered, with fungal communities exhibiting more pronounced shifts than bacterial communities, likely due to their closer ecological associations with morels. Importantly, <i>Z. serrata</i> markedly promoted microbial-mediated soil carbon and nitrogen accumulation, driven by mineral binding, root secretions and soil pH value. These findings enhance understanding of belowground effects of morel understory cultivation, revealing that select tree species like <i>Z. serrata</i> can improve soil quality and nutrient cycling, while targeted nitrate fertilization supports sustaining morel cultivation systems.