Abstract: The latitudinal diversity gradient (LDG) is one of the most notable biodiversity patterns in biogeography. The metabolic theory of ecology (MTE) explains ecological patterns, including the LDG. However, little is known about whether the LDG remains stable over time as climate warming progresses and whether MTE remains applicable to clarify this pattern. In this study, forest data spanning temperate, subtropical, and tropical zones across China were used to analyze long-term changes in the LDG of tree species over 2005–2020. Based on the MTE framework, spatial scales were considered to assess temperature dependence of typical forest trees species. Our results show that species richness decreased with increasing latitude, and that temperature was the primary driver of this change. Although temperature in China has significantly increased over the past two decades, the LDG of tree species has remained stable. However, there was a decrease in species richness in tropical regions over time. With predictions of the MTE, the logarithm of typical forest tree species richness exhibited negative linear relationships with the inverse of ambient temperature, indicating temperature dependence of species richness. However, the relationship remained stable and was strongly influenced by spatial scale, intensifying as spatial scale increased. The findings emphasize the important role of temperature in shaping the LDG. The effects of spatial scale, in particular, should be considered when biodiversity management plans are developed for future climate change.

Key words: Climate warming, Latitudinal diversity gradient (LDG), Metabolic theory of ecology, Species richness, Spatial scale, Temporal dynamic