Constraining the continental-scale terrestrial carbon cycle using NEON data. NSF, 2020-2024 (PI: Jingfeng Xiao, University of New Hampshire)

The National Ecological Observatory Network (NEON) has been collecting large volumes of ecological measurements across the U.S. In its early phases, NEON planned to translate flux observations to the continental scale and to develop continental-scale C flux products, while these products were later determined to be beyond NEON's scope and were descoped. We have developed techniques to upscale fluxes from towers to the continental scale using state-of-the-art satellite observations (e.g., MODIS, OCO-2). These approaches can translate fluxes from NEON sites to the continental scale and to generate gridded flux products. Moreover, NEON offers an extensive list of flux- and pool-based measurements related to land C cycle and presents an unprecedented and yet unexplored opportunity to quantify the US land C sink and its uncertainty. We have also developed a matrix approach to land C cycle modeling. The matrix approach makes it possible to assimilate multiple heterogeneous data sets into comprehensive models by overcoming the computational hurdle. It enables assimilation of both flux- and pool-based data to simultaneously constrain rate and state variables of complex models, which cannot be done before. The matrix approach-enabled data assimilation has the potential to realize the values of NEON data for predicting US land C sequestration potential with uncertainty fully quantified.