Modeling net primary productivity in a Cretaceous terrestrial ecosystem: a probabilistic approach

The Late Campanian Big Cedar Ridge (BCR) fossil site provides a well-preserved record of a rapidly buried ecosystem, offering a unique opportunity to reconstruct past environmental conditions. Understanding net primary productivity (NPP) in such ecosystems is crucial for assessing the energy available to sustain large herbivorous dinosaurs. Here, we present a probabilistic model that estimates paleo-NPP using total organic carbon (TOC) from well-preserved paleosols. This approach integrates soil carbon stocks with decomposition rate estimates, providing a probabilistic approach to reconstructing ancient productivity.When tested in modern ecosystems, the model demonstrates strong predictive performance, particularly in high-TOC, oxygen-limited environments. Applied to BCR, the model estimates a mean NPP of approximately 1816 g C m−2 yr−1, a value comparable to modern tropical and subtropical wetlands. These findings suggest that this Campanian ecosystem was highly productive, capable of sustaining diverse megaherbivore populations and demonstrate the utility of probabilistic NPP modeling for reconstructing the energy budgets of extinct ecosystems and constraining their potential herbivore carrying capacities.By establishing a baseline for estimating primary productivity in deep time, this methodology can provide new insights into the relationship between ecosystem productivity, dinosaur diversity, and paleoecological structure. The model offers a framework for future studies, enhancing our understanding of how primary productivity shaped terrestrial ecosystems during the Mesozoic.