Categorical pahoehoe and 'a'a lava substrate textures of the 1855–56 Mauna Loa lava flow were quantified as surface area and a continuous lava roughness index. Hypsometric point-intercept plots and GIS were used to derive lava roughness models across multiple spatial scales. Water-energy dynamics were quantified as an aridity index. To test the substrate control model, aridity, elevation, lava roughness, and lava texture were used as predictors of primary succession across the topo-climatic gradient. Lava roughness explains the majority of variation in localized primary succession trajectories and ∼10% of the variation across this topo-climatic gradient. The aridity index is a better predictor of ecosystem development than elevation, explaining ∼80% of landscape-scale variation. Significant interactions between aridity and lava texture suggest equilibrium transition points for ecosystem development indicators, as predicted by the substrate control model. Quantified substrate roughness and the aridity index have potential applications for explaining early primary succession trajectories worldwide.