The landscape of models, i.e. the analysis space for model complexity in this exercise, was defined by three dimensions of complexity, i.e. structural (i.e. population dynamics), functional (i.e. ecophysiology) and spatial (i.e. landscape context) complexity. Each dimension was operationally defined by a set of indicators, representing major ecosystem processes and traits (see Table 1). Model complexity was assessed for every indicator using an ordinal scoring relative to the selected reference models (see below), where the most complex representation of the process among the reference models received the highest (5) and the most simple representation the lowest score (1). Aggregation of indicators within the three dimensions was performed by a mean operator.
Table 1: Indicator definition for the three assessment dimensions
| dimension | indicator | description |
| structural complexity (population dynamics) | structure | structural representation of the ecosystem, its constituents and their interactions; includes the approach to model competition |
| composition | compositional representation of the ecosystem (e.g., species) | |
| regeneration | resolution in modeling the processes related to regeneration of trees | |
| mortality | approach to model the processes related to tree death (excluding disturbance- and management-related mortality causes) | |
| management | representation and flexibility in individual- to stand level management | |
| functional complexity (ecophysiology) | primary production | representation of gross primary production and respiration in the model |
| allocation | processes structuring ecosystem compartments, i.e. allocation of photosynthetic products to tree organs | |
| element cycling | element cycles modeled explicitly (e.g., C, N, H2O) | |
| atmospheric processes | which atmosphere-related factors (e.g., climate parameters) are included and how are they represented | |
| belowground processes | detail and process resolution of soil-bound processes in the model | |
| spatial complexity (landscape context) | disturbances | account of natural disturbances in the model |
| management | representation and flexibility in management aspects at the landscape level (e.g., patterns, scheduling) | |
| interactions | spatio-temporal interactions at the landscape scale (e.g., disturbance interactions, seed dispersal) |