Abstract
Earth system models use soil information to parameterize hard-to-measure soil hydraulic properties based on pedotransfer functions. However, current parameterizations rely on sample-scale information which often does not account for biologically-promoted soil structure and heterogeneities in natural landscapes, which may significantly alter infiltration-runoff and other exchange processes at larger scales. Here we propose a systematic framework to incorporate soil structure corrections into pedotransfer functions, informed by remote-sensing vegetation metrics and local soil texture, and use numerical simulations to investigate their effects on spatially distributed and areal averaged infiltration-runoff partitioning. We demonstrate that small scale soil structure features prominently alter the hydrologic response emerging at larger scales and that upscaled parameterizations must consider spatial correlations between vegetation and soil texture. The proposed framework allows the incorporation of hydrological effects of soil structure with appropriate scale considerations into contemporary pedotransfer functions used for land surface parameterization.
Highlights
Earth system models use soil information to parameterize hard-to-measure soil hydraulic properties based on pedotransfer functions
This allows us to focus on soil structure modifications of soil saturated hydraulic conductivity and associated landscape hydrological responses such as rainfall partitioning to infiltration and runoff
Observations at different scales suggest that the simple paradigm of using soil texture as a main predictor of soil hydraulic properties (SHPs) is no longer tenable and factors such as soil structure, vegetation, and scale must be integrated into the parameterization of modern LSMs15,52
Summary
Earth system models use soil information to parameterize hard-to-measure soil hydraulic properties based on pedotransfer functions. The standard parameterization of SHPs in LSMs uses sample scale information, often with little consideration of effective (scale informed) parameter values that account for the heterogeneity (in space and time) of natural landscapes and emergent hydrological nonlinearities and feedbacks[12,17,18,19,20,21,22,23,24]. To this end, a definition of functional relationships between landscape attributes and SHPs, in combination with appropriate regionalization functions and scaling operators[22,24], might provide a way forward for a systematic and physically-based definition of SHPs across scales and locations[21,23,24,25]. We will show that, under certain soil and climatic conditions (i.e., fine-textured soils with dense vegetation cover subjected to high-intensity rainfall events), small scale soil structure plays a key role on the dynamics and timing of the hydrologic response even at the large scales relevant to LSMs
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