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ISMC News 26 April 2022

Featured paper + Featured Soil Modeller

Featured Paper

Confronting the water potential information gap by Kimberly A. Novick et al. 2022 Nature Geoscience

Water potential directly controls the function of leaves, roots and microbes, and gradients in water potential drive water flows throughout the soil–plant–atmosphere continuum. Notwithstanding its clear relevance for many ecosystem processes, soil water potential is rarely measured in situ, and plant water potential observations are generally discrete, sparse, and not yet aggregated into accessible databases. These gaps limit our conceptual understanding of biophysical responses to moisture stress and inject large uncertainty into hydrologic and land-surface models. Here, we outline the conceptual and predictive gains that could be made with more continuous and discoverable observations of water potential in soils and plants. We discuss improvements to sensor technologies that facilitate in situ characterization of water potential, as well as strategies for building new networks that aggregate water potential data across sites. We end by highlighting novel opportunities for linking more representative site-level observations of water potential to remotely sensed proxies. Together, these considerations offer a road map for clearer links between ecohydrological processes and the water potential gradients that have the ‘potential’ to substantially reduce conceptual and modelling uncertainties.

Fig. Water flows downhill along gradients of Ψ in the soils (ΨS, where Ψ is relatively high, often >−1 MPa) through the stems (Ψx) to the leaves (ΨL, where potential is relatively low) and eventually to the air (Ψair, where it can be as low as −100 MPa). Ψ also directly controls key biological processes, including microbial function, mortality risk arising from damaged plant xylem, and plant–atmosphere gas exchange. While observations of environmental drivers, θ, and carbon and water fluxes are broadly accessible from environmental networks and remote sensing, Ψ time series are more discrete, sparse and generally not coordinated or discoverable.

The full paper can be downloaded from this link:  

Featured Soil Modeller

Modeling soil-atmosphere interaction at global scale by Peter Lehmann

Peter Lehmann is soil physicist at ETH Zurich, Switzerland, where he studied environmental sciences and wrote his master and PhD thesis (2002). Following research stages at ETH Lausanne and Swiss Federal Institute for Forest, Snow and Landscape Research WSL, he went back to ETH Zurich in 2008 as researcher and lecturer. After the focus on pore scale processes as PhD student and Postdoc, he worked on evaporation together with Dani Or at various scales. In that context, he is interested in the spatial distribution of soil hydraulic properties to predict evaporation rates at global scale. In addition to work on evaporation, he studies effects of mucilage on soil hydraulic properties (with Andrea Carminati) and the triggering of rainfall induced landslides. He teaches soil physics and measurement methods for bachelor and master students.
- Please tell us briefly about yourself and your research interest.
I’m working in soil physics at ETH since 25 years and witnessed several impressive advances, from intense field work on preferential flow to imaging-based insights in soil structures and Earth-system modeling. My research interests thus cover many scales (from pores and stomata to catchments and continents) and processes (landslides, rainfall partitioning, and soil-plant-water relations). In addition to modeling work, we try to formulate theories of the governing mechanisms of various soil processes and support our findings with experiments. The experiments include both simple lab scale measurements and imaging at various facilities in Switzerland (synchrotron-based X-rays and neutron imaging).

How did you first become interested in soil modelling and learn about ISMC?
I’m interested in soil modeling since my first measurements on nitrous gas emissions during an internship facing the complex interaction of different scales and processes. I was introduced to ISMC by Dani Or and learnt about the relevance of ISMC for global modeling.

Can you share with us your current research focus? And, please tell us briefly how your research could contribute to ISMC Science Panel’s activities
The recent research is on modeling soil hydraulic properties at global scale (PhD thesis of Surya Gupta), collecting data from all geographic regions with different soil formation processes. By combining information on soil properties and environmental covariates that are relevant for soil formation (climate, terrain, vegetation), we try to introduce soil structural effects in the determination of soil hydraulic properties. The collected data and maps could be of interest for other researchers of ISMC to quantify the effects of different soil hydraulic property maps in land surface modeling. In addition to the work on soil structural effects, we study physical constraints for the parameterization of soil hydraulic properties to ensure that the chosen parameter values are in agreement with expected infiltration and evaporation metrics.

Please tell us how can ISMC help you advance in your career?
The world of global modeling is still rather new to me and ISMC helps me to connect to people with more specific experience and knowledge. Especially, in ISMC there are many people with experience in land surface modeling and the collaboration with these researchers enables to include new approaches on (i) parameterization and (ii) process description into land surface models.

 What resources or skills would you recommend that early career members of ISMC should acquire? And how can ISMC help and support early career members in this regard?
Members of ISMC should provide a balance between modeling skills and research activities on soil processes to understand the limits (and power) of soil modeling. The various ISMC groups help to connect to experts in the field and to provide an overview on (i) available data sets and (ii) concepts and principles of soil modules in land surface models.

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