Soil moisture–plant interactions: an ecohydrological review

Abstract

Soil moisture is a key ecohydrological variable in the soil–plant–atmosphere systems; understanding soil moisture–plant interactions is at the core of ecohydrology research. Here we review the current state of knowledge regarding soil moisture–plant interactions and the ecohydrological effects of soil moisture dynamics. Approaches for investigating soil moisture–plant interactions are also reviewed, with emphasis on their ability to predict plant/ecosystem responses to soil moisture variations under environment change. The status and distribution of soil moisture affect ecohydrological processes such as runoff, infiltration and evaporation and plant morphology and function (e.g. transpiration and photosynthetic rate). Plants also affect soil moisture dynamics through its involvement in the water cycle. Soil moisture, evapotranspiration and atmospheric factors (e.g. vapour pressure deficit) are closely linked in transitional soil moisture regimes (ranging from dry to wet soil conditions), the identification of which is critical for quantifying these relationships under different soil moisture conditions. Clarifying the mechanisms of soil moisture–plant interactions can aid in the development of soil moisture models, especially those comprising detailed process representation and feedback. Long-term controlled experiments examining soil moisture dynamics and a meta-analysis of the results are useful for elucidating and quantifying the soil moisture–plant interactions. Soil moisture models are important tools for predicting changes in soil moisture–plant interactions. Simplifying descriptions of each process in models is important; moreover, optimality-based models can provide novel insights that would allow prediction of plant responses to changes in soil moisture dynamics due to environment fluctuations.