FIG 4.

Model-predicted relationships between average annual water balance (average annual precipitation [mm] – average annual evapotranspiration [mm]) and soil expansive capability (linear extensibility percent) on the probability of NTM presence. (A) Relationships across the Hawaiian Islands based on predictions generated from a spatial model accounting for spatial correlation and sampling bias. (B) Predictions were generated for levels of water balance over which there was no confounding relationship between soil expansive capability and water balance. (C) Highly expansive soils with a high water balance have less leaching of Fe-oxide/hydroxide (Fe₂O₃) than TiO₂, an oxide that is not readily leached from soils. (D) Probability of NTM presence was positively related to the relative prevalence of Fe-oxide/hydroxide in wet soils but negatively related in dry soils.