The degradation of Pinus sylvestris var. mongholica plantations in Youyu County on the Loess Plateau has caused major ecological issues, though the mechanisms remain poorly understood. This study explores the effects of stand age and soil properties on the rhizosphere fungal community and their potential roles in plantation degradation. Soil samples were collected from plantations of different stand ages (13, 20, 25, and 35 years), and their fungal diversity and composition were analyzed using high-throughput sequencing. The results showed that soil organic carbon and total nitrogen declined with stand age due to high nutrient demand and limited litter input. The available phosphorus and available potassium (AK) contents were identified as key limiting factors, influencing ectomycorrhizal fungi abundance and the overall soil fungal diversity. With an increasing stand age, the fungal diversity decreased, the ectomycorrhizal fungi declined, and the pathogenic fungi increased, exacerbating plantation degradation. Regression analysis further indicated a significant negative correlation between AK content and stand age, suggesting potassium deficiency as a critical driver of tree health decline. This study highlights the pivotal role of soil nutrient availability in shaping rhizosphere fungal communities and sustaining P. sylvestris plantations, offering insights into degradation mechanisms and strategies to enhance forest resilience on the Loess Plateau.

This study investigated the differences in rhizosphere soil properties and their associations with microbial communities across eight Coffea arabica cultivars cultivated under uniform conditions at the Kangping Education and Research Base in Pu’er, Yunnan. We assessed arbuscular mycorrhizal fungi (AMF) colonization and spore density, analyzed soil chemical properties—including pH, organic matter (OM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), available potassium (AK), and slowly available potassium (SK)—and characterized microbial communities via high-throughput sequencing. The findings of this study demonstrate that coffee variety significantly influences the contents of available nutrients (AN, AP, AK) and OM in the rhizosphere soil. Sequencing indicated that Ascomycota dominated the fungal community, Chloroflexi and Proteobacteria were the primary bacterial phyla, and Glomus and Sclerocystis were the predominant AMF genera. Analysis of alpha diversity showed that in the bacterial community, S8 exhibited the highest diversity and richness, while S6 showed the lowest. For the fungal community, S6 had the highest diversity, S2 displayed the highest richness, and S5 showed the lowest values for both diversity and richness. Within the AMF community, S8 demonstrated the highest diversity, S7 exhibited the highest richness, and S6 had the lowest diversity and richness values. Overall, bacterial diversity surpassed fungal diversity. Redundancy analysis identified AK as a common key factor influencing both bacterial and fungal communities. Besides AK, OM and TN were also significant drivers for the fungal and bacterial communities, respectively, while the AMF community was most strongly associated with SK