The increased effect of spring leaf unfolding on autumn senescence in the northern and southern hemispheres

Plant phenology, the timing of periodic events in plant development, is an indicator for detecting climate-vegetation dynamics. Although the importance of vegetation growth carryover (VGC) on phenology was recognized in the Northern Hemisphere (NH), it is unclear how VGC and climatic factors contribute to phenology and how these contributions evolve at a global scale. Utilizing two sets of satellite NDVI data, we explored the impacts of climate change and VGC on start-of-season (SOS) and end-of-season (EOS) plant phenology during the past four decades. Here we show that, globally, advanced SOS resulted primarily from the increasing temperature and radiation, whereas delayed EOS was mainly attributed to the increasing temperature and VGC in SOS (VGC _SOS ). VGC _SOS was the main driver of EOS in the southern hemisphere (SH), whereas it was temperature in the NH. Furthermore, the contribution of VGC _SOS to EOS displayed increasing trends over the past four decades in both hemispheres, which was particularly significant in NH. These differences were due primarily to the more evident "warming and drying" trends in the SH than NH, which weaken VGC _SOS 's impact on vegetation EOS. We conclude that VGC _SOS contributes substantially to EOS in both hemispheres, offering insights for accurate predictions of vegetation growth and carbon sequestration under future global warming scenarios.