The relationship between Rhododendron simsii and its soil microbial community under heat stress was not clear. In this study, the effects of heat stress on the physiological characteristics, soil physicochemical properties and soil microbial community structure of R. simsii were investigated. The experimental control (CK) was set as day/night (14/10 h) 25/20°C and experimental treatments were set as light heat stress (LHS) 35/30°C and high heat stress (HHS) 40/35°C. Our results showed that, compared with CK, LHS treatment significantly increased malondialdehyde, hydrogen peroxide, proline and soluble sugar contents, as well as catalase and peroxidase activities, while HHS treatment significantly increased ascorbate peroxidase activity and decreased chlorophyll content. Compared with CK, LHS treatment significantly reduced soil ammonium-nitrogen and nitrate-nitrogen content, while HHS significantly increased soil ammonium-nitrogen content. Compared with CK, both treatments changed the soil microbial community structure. For bacterial community, LHS and HHS treatment resulting in the significant enrichment of Burkholderia-Caballeronia-Paraburkholderia and Occallatibacte, respectively. For fungal community, LHS treatment resulting in the significant enrichment of Candida, Mortierella and Boothiomyces. The redundancy analysis showed that plant physiological characteristics, soil ammonium-nitrogen content were significantly correlated with the soil microbial community. Therefore, heat stress altered the soil microbial community structure, and affected the availability of soil available nitrogen, which in turn affected the physiological characteristics of R. simsii. We suggest that soil microbial community may play an important role in plant resistance to heat stress, and its mechanism deserves further study.

The diverse ecosystems in the mountainous regions of southwestern China provide various essential ecosystem services, which are critical for the ecological protection and sustainable development of the upper reaches of the Yangtze and Pearl Rivers. Although the scale dependency of ecosystem services has been demonstrated, the effects of different grid scales on the complex mountain ecosystem services remain unclear. This study selects Wangcao Town in Zunyi City, Guizhou Province of China, as a typical representative of mountainous areas. Utilizing GIS technology and the InVEST model, the response of five key ecosystem services to four grid scales (30 m, 100 m, 300 m, and 600 m) is analyzed. The results reveal that nutrient purification is significantly more sensitive to changes in grid scale compared to water yield, soil retention, carbon storage, and crop production. While increasing the grid scale alters the correlation coefficients between ecosystem services, it does not fundamentally change the trade-offs and synergies among them. Differences in ecosystem service responses and their relationships are observed across different slope gradients under varying grid scales. Most ecosystem services and their relationships exhibit greater sensitivity to grid scale in the 0-5º slope range compared to other slope gradients. The dominant landscape type plays a critical role in the scale dependency of ecosystem services in complex mountainous terrain as the grid scale changes.