Abies beshanzuensis M. H. Wu is a critically endangered conifer endemic to cool, high-elevation forests; its narrow range renders it vulnerable to climate warming and associated heat and water stress. We simulated climate warming by growing seedlings along an elevational gradient (500-1200 m) to assess physiological and molecular stress responses. Seedlings at mid-high elevation (1000-1200 m) grew optimally, whereas low-elevation (500 m) seedlings showed stress symptoms. At 500 m, Yield and ETR declined sharply; stomatal conductance also dropped, and NPQ collapsed entirely, dropping below the 1550 m baseline, proving quantitatively insufficient to prevent massive photoinhibition. Consequently, leaf chlorophyll content and biomass peaked at 1000 m and declined precipitously toward 500 m. Low-elevation leaves accumulated significantly higher levels of proline, soluble sugars, and proteins. However, this robust osmotic adjustment was physically insufficient to counteract the severe drought and heat stress, culminating in elevated MDA content and severe cellular damage. Antioxidant enzyme activities were highest at 1000 m and decreased at lower elevations. Transcriptome profiling and analysis of DEGs revealed altitude-dependent gene regulation. At 500 m, structural hub genes driving oxidative phosphorylation, glutathione metabolism, flavonoid biosynthesis (CSF7, MDMC, CHS), circadian rhythms, and heat-shock proteins were strongly upregulated. In contrast, genes for photosystems, primary hormone signaling, brassinosteroid biosynthesis, and pathogen defense were suppressed. Simulated warming induced pronounced stress responses, with photosynthesis and growth severely compromised, overwhelming osmotic adjustment and antioxidant defenses. These findings underscore the extreme climate vulnerability of A. beshanzuensis, establish 1000 m as a lower survival threshold, and highlight the urgent need to protect its high-elevation habitat and implement assisted conservation strategies.

Montane shrubby grasslands, as one of the world’s important ecosystems, are highly sensitive to climate change and human activities, especially in the subtropical regions experiencing rapid economic development. However, little is known about how anthropogenic activities, such as firebreak construction, interact with elevation to influence plant diversity in these ecosystems. Shrub and herbaceous communities were surveyed in subtropical montane shrubby grassland within Baishanzu National Park, eastern China. Nine transects were established along firebreaks, each with two edge plots near firebreak and two interior plots away firebreak, and twelve additional control plots in adjacent undisturbed areas. Species diversity was assessed using the Hill index. Our results revealed distinct responses of shrubs and herbs to firebreak disturbance and elevation. Firebreaks reduced shrub diversity but enhanced herb diversity, and both groups exhibited contrasting elevational patterns. In control areas, shrub diversity decreased while herb diversity increased with elevation, whereas in firebreak zones, these relationships were altered, with edge plots showing a hump-shaped diversity pattern. Differences in shrub diversity but not herbs between interior and edge plots decreased with elevation. Species composition also differed significantly between firebreak and control areas, driven mainly by elevation in control areas and by soil properties near firebreaks. These findings demonstrate that firebreak construction reshapes the elevation–diversity relationships of both herbs and shrubs, highlighting the sensitivity of high-elevation montane shrubby grasslands to small-scale disturbances. Effective firebreak management should therefore account for both elevational context and disturbance intensity to maintain ecosystem biodiversity and stability.