title: Dominant role of plant physiology in trend and variability of gross primary productivity in North America.
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 (GSstartand 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 GPPmaxboth at the ecosystem and regional scales. During warmer spring and autumn, GSstartis advanced and GSenddelayed, respectively. GPPmaxresponds 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.
authors.affiliation: State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China.|Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Sha
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Department of Microbiology and Plant Biology, Center for Spatial Analysis, University of Oklahoma, Norman, OK 73019, USA.
authors.forename: Yao
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, CEA CNRS UVSQ, Gif-sur-Yvette 91190, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Ciais
authors.affiliation: Department of Microbiology and Plant Biology, Center for Spatial Analysis, University of Oklahoma, Norman, OK 73019, USA.|Instittue of Biodiversity Science, Fudan University, Shanghai 200433, China.
authors.forename: Xiangming
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma 73019, USA.|Center for Earth System Science, Tsinghua University, Beijing 100084, China.
authors.forename: Yiqi
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Kelly K
authors.initials: KK
authors.lastname: Caylor
authors.affiliation: State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China.|College of Ecological and Environmental Engineering, Qinghai University, Xining 810086 Qinghai, China.
authors.forename: Yuefei
authors.initials: Y
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Guangqian
authors.initials: G
authors.lastname: Wang
mesh_terms: D002980:Climate; D015233:Models, Statistical; D009656:North America; D063245:Plant Development; D018521:Plant Physiological Phenomena; D012044:Regression Analysis; D012621:Seasons; D013696:Temperature; D013997:Time Factors