## 2 Materials and Methods
### Model Descriptions
#### 2.1.1 Landis-Ii Nencn  
The LANDIS-II model is an extension of the original LANdscape DI disturbance and Succession (LANDIS) model [90; 91; 92] into a modular software framework [87]. Specifically, LANDIS-II is a model core containing basic state information that interfaces or communicates with external user-developed models known as \"extensions\" using a combination of object-oriented and modular design. This design makes LANDIS-II a modeling framework rather than a model. The LANDIS family of models, which also includes LANDIS PRO [93] and Fin-LANDIS [94; 95], are stochastic hybrid models [29] based on the vital attributes/fuzzy systems approach of the LANDSIM model genre [96]. This genre borrows heavily from cellular automata [97] and thus Markov Chains by applying simple heuristic rule-based systems, in the form of vital attributes, across two-dimensional grids.  
Models of the LANDSIM genre focus on landscape-scale processes and assume game-theoretic vital attribute controls over successional trajectories following disturbance [98]. The LANDSIM model genre is thus a reasonable match for the classical forest fire model [99], given its local two-dimensional cellular basis. In contrast to the original LANDIS model, LANDIS-II is implemented in Microsoft C# rather than ISO C++98 [100], simplifying model development in exchange for a proprietary single-vendor software stack [87].  
The latest version of LANDS-II (v7) supports Linux through use of the Microsoft.NET Core developer platform. The modular design of LANDS-II is intended to simplify the authorship and interaction of user-provided libraries for succession and disturbance. The centralized model core stores basic landscape and species state information and acts as an interface between succession and disturbance models. While there have been numerous forest landscape models over the years [21; 22; 23; 24; 25], the LANDIS family of models has enjoyed notable longevity and is currently united under the LANDIS-II Foundation. Part of its longevity is attributable to the prioritization of model functionality over realism in order to appeal to application-minded managers seeking a broad array of functionality.  
The Net Ecosystem Carbon and Nitrogen (NECN) model [101] is a simplified variant of the classical Century model [36; 37]. The original ten soil layers in Century have been replaced by a single soil layer, with functions for growth and decay borrowed directly from Century v4.5. The NECN succession model Figure 1 is thus a process-based model that simulates C and N dynamics along the plant-soil continuum at a native monthly timestep.  
Atmospheric effects are included through monthly climate (i.e., temperature maxima, minima, means, and standard deviations, and precipitation means and standard deviations). Explicit geometric representation of tree canopies is forgone in favor of bounded statistical growth models based  
Figure 1: LANdscape D disturbance and Succession II Net Ecosystem Carbon and Nitrogen (LANDIS-II NECN) model structure.  
theoretically on Liebig's Law of the Minimum. Functions for growth, mortality, and decay are adopted from Century [36] while hydrology is based on the simple bucket model [102]. The regeneration function is the only new process in NECN and is also based on Liebig's Law. For a detailed description of the NECN model, readers may refer to the original model publication [101]. Parameterization of the LANDIS-II model for both sites was based on updating parameters used in recent [103; 104; 105; 106] and ongoing ([PERSON] et al., in review) work.