Phenology and carbon fixing: a satellite-based study over Continental USA

Global climate change has led to concerns about its impact on our biosphere and vegetation. Any impact of climate on vegetation can manifest in terms of changes in plant growth characteristics, its health and timing of different vegetative phenomena, such as germination, bud burst, maturity, etc. The duration and changes in the timing of plant growth stages can in turn impact the global carbon cycle. Similarly any change in plant productivity, because of changing climate will alter the carbon flux pattern by changing the overall biological flux being added or taken away from the atmosphere. We have used satellite data to study spatiotemporal changes in the plant phenology and plant productivity over the Continental USA (CONUS) to get an overall understanding of the evolution of these metrics over the past decade. Our study reveals that the prairies situated in the heartland of CONUS have become an increasingly important player in determining any changes in vegetation induced carbon source/sink patterns. The northern Great Plains has shown increased fixation of carbon in recent years, while the southern Plains has become a carbon source. This has been largely driven by changes in recent weather patterns where the northern plains have seen an increasingly cooler and wetter growing season whereas the southern plains have at the same time seen increased aridity, especially since 2011. This is also reflected in increasing growing season greenness values over the northern Plains and the opposite over the southern Plains. The gradual changing pattern of land biological fluxes over CONUS, as documented in this paper will likely be of interest to climate modellers as they seek to better understand the interaction between global carbon balance and climate change.