Climatic differences among habitats shape the balance between maximum lifespan and life expectancy in Japanese tree species.

Old trees, often living for hundreds or even thousands of years, play vital roles in maintaining biodiversity and ecosystem services. However, their extraordinary longevity occurs under rare circumstances, as most individuals succumb to mortality. From an optimal resource allocation perspective, species adopting a life-history strategy with a high potential maximum lifespan (PML) are expected to also have a higher life expectancy (LE). Here we developed a framework to assess the longevity of 1-cm-diameter trees and calculated the PML and LE for 53 major tree species in Japan. The results revealed that the PML (mean 378 years) was 4.7 times higher than the LE (mean 81 years). Both indices showed a positive correlation, with a regression slope of 0.34; however, the explanatory power of the model was low (R = 0.22). This can be attributed to the fact that LE exhibits a stronger negative response to climate-related habitat severity compared with that of PML. Our findings suggest two key points: (1) trees may adopt a hierarchical ordering of demographic parameters that prioritize long-term survival duration over average survival rate, and (2) considering this balance, which varies among species, could enhance the cost-effectiveness of ecosystem restoration.