Integrating spatial and environmental stressors in a population model of Folsomia candida (Collembola, Isotomidae): a Formal Model within ALMaSS framework

Collembola are key soil invertebrates that contribute to decomposition processes and nutrient cycling in agricultural ecosystems. Folsomia candida , a parthenogenetic euedaphic species, is widely used as a model organism in ecotoxicological testing, yet population-level responses to environmental stressors in spatially structured landscapes remain poorly understood. We present a formal model of F. candida developed using a subpopulation approach within the Animal, Landscape and Man Simulation System (ALMaSS). The model integrates stage-structured population dynamics with spatially explicit landscape processes, incorporating hourly weather data and daily soil moisture dynamics at 10 by 10 m resolution. Growth, development, reproduction, and mortality are driven by temperature, soil moisture, and food quality through empirically parameterised thermal performance curves and dose–response functions fitted to published experimental data. The model explicitly represents egg, juvenile, and adult life stages, with stage transitions and vital rates responding non-linearly to environmental conditions. Soil moisture effects are modelled using a novel integration of ERA5 reanalysis data, soil physical properties, and evapotranspiration to estimate surface soil water potential. Temperature and moisture effects are combined using a limiting-factor approach, reflecting current understanding of physiological constraints. The model is designed for simulations at subpopulation spatial scales of 100 m 2 , within landscapes typically 10 km × 10 km, providing a mechanistic framework for exploring F. candida population dynamics under realistic environmental heterogeneity in agricultural landscapes. This formal model documentation establishes the theoretical foundation and empirical basis for subsequent model implementation, evaluation, and application to questions in landscape ecology and environmental risk assessment.