Estimating vegetation productivity of urban regions using sun-induced chlorophyll fluorescence data derived from the OCO-2 satellite

Abstract

Sun-induced chlorophyll fluorescence (SIF) is a byproduct of plant photosynthesis, considered to be an indicator of photosynthetic activity. It has been found in literature that there is a linear statistical relationship between vegetation gross primary productivity (GPP) and SIF in different kinds of plants, which provides a more convenient method for GPP estimation. The new high-resolution SIF data derived from the OCO-2 satellite provide an accurate method for the study of urban vegetation growth at urban scale. In this work, we analyzed the feasibility of using OCO-2 SIF data to estimating urban vegetation GPP. First, we explored the potential of using SIF to monitor vegetation growth in urban areas. The global coverage of OCO-2 SIF in space and time was also explored. The value of OCO-2 SIF varied seasonally and was consistent with changes in vegetation growth. We also found that SIF can more efficiently reflect the true growth status of vegetation than of NDVI in urban areas. Second, we explored the relationships between vegetation GPP measured at flux observation stations and OCO-2 SIF data. In specific, we used GPP data from flux observation stations to match OCO-2 SIF in time and established the statistical relationships between vegetation GPP and OCO-2 SIF. Based on our analysis, the statistical relationships between GPP and SIF were established for different vegetation types. In the study, we estimated vegetation GPP in the urban region of the Pearl River Delta, China, using statistical relationships between GPP and SIF. The results showed that vegetation GPP estimated using the high-resolution OCO-2 SIF can show spatial details of vegetation productivity in urban regions and temporal variations of vegetation growth. In conclusion, the method of using OCO-2 SIF to estimate GPP established in this study could provide support for the study of vegetation productivity in urban regions around the world.