Seasonal biological carryover dominates northern vegetation growth

The state of ecosystems is influenced strongly by their past, and describing this carryover effect is important to accurately forecast their future behaviors. However, the strength and persistence of this carryover effect on ecosystem dynamics in comparison to that of simultaneous environmental drivers are still poorly understood. Here, we show that vegetation growth carryover (VGC), defined as the effect of present states of vegetation on subsequent growth, exerts strong positive impacts on seasonal vegetation growth over the Northern Hemisphere. In particular, this VGC of early growing-season vegetation growth is even stronger than past and co-occurring climate on determining peak-to-late season vegetation growth, and is the primary contributor to the recently observed annual greening trend. The effect of seasonal VGC persists into the subsequent year but not further. Current process-based ecosystem models greatly underestimate the VGC effect, and may therefore underestimate the CO2 sequestration potential of northern vegetation under future warming. The future of terrestrial systems is influenced by their past, but this carryover effect is rarely quantified. Here, the authors provide the first quantitative evidence that a greener spring begets a greener summer and autumn, and that this carryover effect is even stronger than climate drivers.

Automated summary

The study demonstrates that the carryover effect of vegetation growth has strong positive impacts on seasonal vegetation growth in the Northern Hemisphere, particularly in early growing-season vegetation growth, surpassing the influence of past and co-occurring climate factors. This carryover effect persists into the subsequent year but does not extend further, significantly contributing to the observed annual greening trend.