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Subalpine shrubland is an important vegetation type in the Hengduan Mountains region of China, and its distribution has been substantially influenced by global warming. In this research, four subalpine shrub communities in the Hengduan Mountains were selected: Rhododendron heliolepis Franch. scrub, Rhododendron flavidum Franch. scrub, Quercus monimotricha (Hand.-Mazz.) Hand.-Mazz. scrub, and Pinus yunnanensis var. pygmaea (Hsueh ex C. Y. Cheng, W. C. Cheng & L. K. Fu) Hsueh scrub. A MaxEnt model was used to assess the suitable habitats and their primary drivers of four subalpine shrublands in China under different climate scenarios. Our results indicate the following: (1) The suitable habitat areas of the four subalpine shrublands exhibit a predominant distribution within the Hengduan Mountains region, with small populations in the Himalayas and Wumeng Mountain. Temperature and precipitation are identified as the primary drivers influencing the suitable habitat areas of the four subalpine shrublands, and the temperature factor is more influential than the precipitation factor. Furthermore, the contribution rate of slope to Quercus monimotricha scrub is 19.2%, which cannot be disregarded. (2) Under future climate scenarios, the total suitable habitats of the four subalpine shrublands show an expanding trend. However, the highly suitable areas of three shrublands (Rhododendron flavidum scrub, Quercus monimotricha scrub, and Pinus yunnanensis var. pygmaea scrub) show a contracting trend under the high-carbon-emission scenario (SSP585). (3) Driven by global warming, the suitable habitat areas of Rhododendron heliolepis scrub, Rhododendron flavidum scrub, and Pinus yunnanensis var. pygmaea scrub shift toward higher elevations in the northwest, while the distribution of Quercus monimotricha scrub varies under different carbon emission scenarios, with a much smaller shift range than the other three scrubs. Our study contributes valuable insights into the spatiotemporal dynamics of subalpine shrublands in China under climate change, providing scientific guidance for biodiversity conservation and ecosystem restoration. Full article

Pinus yunnanensis var. pygmaea demonstrates obvious loss of apical dominance, inconspicuous main trunk, which can be used as an ideal material for dwarfing rootstocks. In order to find out the reasons for the lack of apical dominance of P. pygmaea, endogenous phytohormone content determination by liquid chromatography–tandem mass spectrometry (LC–MS/MS) and comparative transcriptomes were performed on the shoot apical meristem and root apical meristem of three pine species (P. massoniana, P. pygmaea, and P. elliottii). The results showed that the lack of CK and the massive accumulation of ABA and GA-related hormones may be the reasons for the loss of shoot apical dominance and the formation of multi-branching, the abnormal synthesis of diterpenoid biosynthesis may lead to the influence of GA-related synthesis, and the high expression of GA 2-oxidase (GA2ox) gene may be the cause of dwarfing. Weighted correlation network analysis (WGCNA) screened some modules that were highly expressed in the shoot apical meristem of P. pygmaea. These findings provided valuable information for identifying the network regulation of shoot apical dominance loss in P. pygmaea and enhanced the understanding of the molecular mechanism of shoot apical dominance growth differences among Pinus species. Full article