Dominant role of plant physiology in trend and variability of gross primary productivity in North America

Sha Zhou,Xiangming Xiao,Philippe Ciais,Yiqi Luo,Yao Zhang,Yuefei Huang,Kelly K Caylor,Guangqian Wang

doi:10.1038/srep41366

Abstract

Annual gross primary productivity (GPP) varies considerably due to climate-induced changes in plant phenology and physiology. However, the relative importance of plant phenology and physiology on annual GPP variation is not clear. In this study, a Statistical Model of Integrated Phenology and Physiology (SMIPP) was used to evaluate the relative contributions of maximum daily GPP (GPPmax) and the start and end of growing season (GSstart and GSend) to annual GPP variability, using a regional GPP product in North America during 2000–2014 and GPP data from 24 AmeriFlux sites. Climatic sensitivity of the three indicators was assessed to investigate the climate impacts on plant phenology and physiology. The SMIPP can explain 98% of inter-annual variability of GPP over mid- and high latitudes in North America. The long-term trend and inter-annual variability of GPP are dominated by GPPmax both at the ecosystem and regional scales. During warmer spring and autumn, GSstart is advanced and GSend delayed, respectively. GPPmax responds positively to summer temperature over high latitudes (40–80°N), but negatively in mid-latitudes (25–40°N). This study demonstrates that plant physiology, rather than phenology, plays a dominant role in annual GPP variability, indicating more attention should be paid to physiological change under futher climate change.

Highlights

Because the annual GPP variability is related to plant phenological and physiological changes, the responses of the above three indicators to climate variability is crucial to diagnose the drivers of annual GPP variability through the Statistical Model of Integrated Phenology and Physiology (SMIPP)
We found that plant physiology plays a more important role than phenology in determining the long-term trend and inter-annual variability of vegetation photosynthesis model (VPM) GPP and site scale AmeriFlux GPP
The importance of plant phenology on seasonal and annual GPP variability has been shown in many studies[1,2,5,28,29]

Summary

Introduction

The variation in the product of CUP by GPPmax was found to explain more than 90% of the temporal variability of annual GPP in most areas of North America during 2000–2010, and more than 95% of the spatial GPP gradients among 213 flux tower sites[4]. The Statistical Model of Integrated Phenology and Physiology (SMIPP) extends the approach of Xia et al.[4] by treating separately GSstart, GSend and GPPmax, as predictors of annual GPP This model described in Zhou et al.[14] was shown to explain 90 ± 11% of the inter-annual variability of GPP among 27 flux tower sites across North America and Europe. We derive the climatic sensitivity of the three indicators, and investigate the mechanism of annual GPP responses to temperature, precipitation and downward solar radiation through plant phenological and physiological changes over different regions

Methods

Results

Conclusion