3.5 Changes in Spatial Pattern of Potential Suitable Areas of T. sinense
Compared to the current period, the suitable area for T. sinense decreased from the last interglacial period to the mid-Holocene, followed by an increase (Fig. 6). During the mid-Holocene, an additional area of approximately 119,693.5 km2 emerged, constituting 17.72% of the total area. These additions were mainly concentrated in central Yunnan and southern Gansu. Conversely, during the last glacial period, the cold climate led to a significant reduction in suitable habitats, resulting in a loss of 42,620.2 km2, or a 6.3% decrease (Table 5). Losses occurred predominantly in fragmented areas at the junction of Sichuan, Yunnan, Gansu, and Shaanxi provinces. Retention areas during the Last Glacial Maximum were primarily situated in Southwest China.
The expansion rate for 2050 was lower than that for 2070 across eight different climate scenarios with similar concentrations (Fig. 6). In the 2050s, the additional area for T. sinense initially expanded, then contracted with increasing greenhouse gas emissions. Conversely, by the 2070s, the additional area exhibited an upward trend with increased emissions. Except for the SSPs2.6 scenario, the loss rate in the 2070s was significantly higher than that in the 2050s (Table 5). Overall, under future climate scenarios, fragmentation of potential distribution areas suitable for T. sinense is expected to increase. Loss areas will concentrate in the southern region of the current suitable area, while added areas will primarily occur in the north. These areas require close monitoring for potential pattern changes.