The Relationship Between Seasonal Pattern of Photosynthetic Parameters and Plant Phenology

The plant physiological observations during the whole growing season showed a strong seasonal variation of the biochemical parameters in the photosynthesis model, such as maximum carboxylation velocity and maximum rate of electron transport in Farquhar model, which are essential for accurate modeling of photosynthesis and carbon exchange. These photosynthetic parameters are influenced by temperature, leaf nitrogen content, leaf age, and other factors. The seasonal pattern of photosynthetic parameters derived from most ground measurements contains three different phases, increased at juvenile, stable at maturity, and decreased at old stage. While the three phases of parameters do not directly correspond with the calendar seasons, and the periods for these phases vary among species. Plant phenology is the study of periodic biological events, and the whole plant growth season could be divided to several phenological phases. The phenological phases are usually estimated by temporal series analysis of satellite remote sensing vegetation index. By comparing seasonal pattern, there is correspondence between the phases of photosynthetic parameters and the phases of plant phenology. Therefore, the photosynthetic parameters could be changed for the different phenological phases from remote sensing data. While this study is in progress to explore the relationship between phenological phases and the phases of photosynthetic parameters, and it is possible to improve a transition algorithm between two phases for accurate estimation of photosynthetic parameters at a large scale.