Global vegetation productivity and hydrometeorological variables

How does taking into account vertical variability of Soil Moisture impact on predicting vegetation productivity? Does this impact depend on climatic areas and vegetation types?

These are the main questions addressed by a recently published paper, outcome of Living Planet Fellow Sophia Walther research.

The study demonstrates how, at the global scale, semi-arid areas and vegetation types such as grasses and shrubs are controlled by comparatively deep soil layers moisture as they have deep rooting systems. A complexity not yet acknowledged by global vegetation models which apply constant soil depths.

Besides that, hydrometeorological controls – water (total soil moisture, precipitation) vs energy (solar radiation, temperature, vapour pressure deficit) – of vegetation productivity are compared by means of various proxy metrics, namely SIF (sun-induced fluorescence), NDVI (normalised difference vegetation index) and NIRv (near-infrared reflectance of terrestrial vegetation).


Main hydrometeorological controls on sun-induced fluorescence (SIF) using (a) total and (b) multi-layer soil moisture (SM). (c) Shifts between the energy and water controls from (a) to (b). Proportions of study area where each variable is the most important factor are shown in (d and e). TP denotes precipitation; TSM denotes total SM; SM1, 2, 3, 4 denote SM in layers 1, 2, 3, 4 respectively; TEM denotes temperature; SSRD denotes solar radiation; VPD denotes vapor pressure deficit.


Proxy metrics are derived from GOME-2 and MODIS long-track records, while energy and water-related variables are from the ERA5 reanalysis.


Li, W.Migliavacca, M.Forkel, M.Walther, S.Reichstein, M., & Orth, R. (2021). Revisiting global vegetation controls using multi-layer soil moistureGeophysical Research Letters48, e2021GL092856.



Featured image : Water droplets on vegetation. Credit: Guido Gloor Modjib