## 1 Introduction
### Existing Forest Ecosystem Model Intercomparison Projects
Presently, no other current forest biogeochemistry MIP is evident for the Americas, leaving a substantial spatial sampling bias in model implementation. There is a critical need to conduct ongoing forest biogeochemistry model comparisons in this and other regions of the world in order to establish the regional foundation for robust global C cycle projections. While model initialization and validation data may be relatively difficult to come by in other regions, North America enjoys some of the most thorough forest inventory data in the world, with wide coverage and repeat sampling. This is particularly true for vast temperate and boreal forests in the US and Canada that are critical to the global C cycle. Meanwhile, Mexico, Puerto Rico, and the state of Hawaii contain tropical forests critical for improving models in these systems globally. In this work, we aim to begin this process for North America with a comparison of the Perfect Plasticity Approximation with Simple Biogeochemistry (PPA-SiBGC) and Landscape Disturbance and Succession with Net Ecosystem Carbon and Nitrogen (LANDIS-II NECN) models, which provide contrasting model structures for representing demographic and biogeochemical processes. In this forest biogeochemistry MIP, we focus on two sites on the East Coast of the United States, Harvard Forest (HF), Massachusetts and Jones Ecological Research Center (JERC), Georgia. The two sites were selected for their representativeness of the United States Eastern Seaboard and for the availability of data needed to parameterize and validate the models. Harvard Forest is one of the most-studied forests in the world, with Google Scholar returning 12,700 results for the site. We focus on results for the Environmental Measurement Station (EMS) eddy covariance (EC) flux tower site within the Little Prospect Hill tract - the longest-running eddy covariance flux tower in the world. While there have been fewer studies at Jones Ecological Research Center, Georgia, USA, Google Scholar returns1370 results for the site, reflecting its growing role in forest sciences research. Our study focuses on the Red Dirt (RD) EC flux tower site within the mesic sector. In this work, we aim to establish a foundation for future forest biogeochemistry model intercomparisons. This includes open-source object-oriented software to facilitate model parameterization, validation, intercomparison, and simplified reproducibility of results, based on our Earth-science Research and Development Environment (Erde), a library implemented in R and Python ([PERSON] and [PERSON], in preparation). We perform the model intercomparison for two key research forests in the United States to assess the ability of each model to reproduce observed biogeochemistry pools and fluxes over time. We hypothesize that the inclusion of forest growth, compositional change, and mortality processes in both models will allow for accurate predictions of biomass and NEE dynamics, as suggested in previous research [PERSON] et al. [88]. Accordingly, we compare both models to observations and to each other for a host of metrics related to biomass, C, N, and forest composition at the two research sites.