Abiotic and biotic controls of soil moisture spatiotemporal variability and the occurrence of hysteresis

Abstract

An expression that separates biotic and abiotic controls on the temporal dynamics of the soil moisture spatial coefficient of variation Cv(θ) was explored via numerical simulations using a mechanistic ecohydrological model, Tethys‐Chloris. Continuous soil moisture spatiotemporal dynamics at an exemplary hillslope domain were computed for six case studies characterized by different climate and vegetation cover and for three configurations of soil properties. It was shown that abiotic controls largely exceed their biotic counterparts in wet climates. Biotic controls on Cv(θ) were found to be more pronounced in Mediterranean climates. The relation between Cv(θ) and spatial mean soil moisture θ¯ was found to be unique in wet locations, regardless of the soil properties. For the case of homogeneous soil texture, hysteretic cycles between Cv(θ) and θ¯ were observed in all Mediterranean climate locations considered here and to a lesser extent in a deciduous temperate forest. Heterogeneity in soil properties increased Cv(θ) to values commensurate with field observations and weakened signatures of hysteresis at all of the studied locations. This finding highlights the role of site‐specific heterogeneities in hiding or even eliminating the signature of climatic and biotic controls on Cv(θ), thereby offering a new perspective on causes of confounding results reported across field experiments.Key Points:Abiotic controls are larger than biotic and are dominant in wet climatesHysteresis is stronger for Mediterranean than wet climatesHeterogeneity in soil properties weakens signatures of hysteresis