Significant early end of the growing season of forest vegetation inside China's protected areas.

The land surface phenology (LSP) indicators (i.e., start, end, and length of the growing season: SOS, EOS, LOS) are important to reflect the growth of forest and its response to environmental changes. However, the spatiotemporal variation and its mechanism of forest phenology under different human disturbance' levels are still unclear. Here, we compare the LSP indicators inside and outside China's 257 protected areas (PAs) and explore the influencing factors of phenological differences (ΔSOS, ΔEOS, ΔLOS). We find that in general, EOS inside PAs (mean ± s.e.m: 312.6 ± 1.2days) is significantly earlier than outside (314.6 ± 1.2days), and LOS inside PAs (218.9 ± 2.0days) are significantly shorter than outside (220.6 ± 2.0days). ΔSOS and ΔEOS are controlled by nighttime and daytime temperature differences, respectively, and both factors affect ΔLOS. This evidence provides a new understanding about the functions of PAs and its influence on forest vegetation growth.