08 May 2023
 | 08 May 2023

Relevance of near-surface soil moisture vs. terrestrial water storage for global vegetation functioning

Prajwal Khanal, Anne Hoek Van Dijke, Timo Schaffhauser, Wantong Li, Sinikka J. Paulus, Chunhui Zhan, and René Orth

Abstract. Soil water availability is an essential prerequisite for vegetation functioning. Vegetation takes up water from varying soil depths depending on the characteristics of their rooting system and soil moisture availability across depth. The depth of vegetation water uptake is largely unknown across large spatial scales as a consequence of sparse ground measurements. At the same time, emerging satellite-derived observations of vegetation functioning, surface soil moisture and terrestrial water storage, present an opportunity to assess the depth of vegetation water uptake globally. In this study, we characterise vegetation functioning through the Near-Infrared Reflectance of Vegetation (NIRv), and compare its relation to (i) near-surface soil moisture from ESA-CCI and (ii) total water storage from GRACE at the monthly time scale during the growing season. The relationships are quantified through partial correlations to mitigate the influence of confounding factors such as energy-related variables. We find that vegetation functioning is generally more strongly related to near-surface soil moisture, particularly in semi-arid regions and areas with low tree cover. In contrast, in regions with high tree cover and in arid regions, the correlation with terrestrial water storage is comparable to or even higher than with near-surface soil moisture, indicating that trees can and do make use of their deeper rooting systems to access deeper soil moisture, similar to vegetation in arid regions. In line with this, an attribution analysis that examines the relative importance of these soil water storages for vegetation reveals that they are controlled by (i) water availability influenced by the climate and (ii) vegetation type reflecting adaptation of ecosystems to local water resources. Next to variations in space, the vegetation water uptake depth also varies in time. During dry periods, the relative importance of terrestrial water storage increases, highlighting the relevance of deeper water resources during rain-scarce periods. Overall, the synergistic exploitation of state-of-the-art satellite data products to disentangle the relevance of near-surface vs. terrestrial water storage for vegetation functioning can inform the representation of vegetation-water interactions in land surface models to support more accurate climate change projections.

Prajwal Khanal et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-770', Andrew Feldman, 23 May 2023
    • AC1: 'Reply on RC2', Prajwal Khanal, 30 Oct 2023
  • RC2: 'Comment on egusphere-2023-770', Anonymous Referee #2, 11 Aug 2023
    • AC2: 'Reply on RC1', Prajwal Khanal, 30 Oct 2023
    • AC3: 'Reply on RC1', Prajwal Khanal, 30 Oct 2023

Prajwal Khanal et al.


Total article views: 614 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
421 172 21 614 46 7 12
  • HTML: 421
  • PDF: 172
  • XML: 21
  • Total: 614
  • Supplement: 46
  • BibTeX: 7
  • EndNote: 12
Views and downloads (calculated since 08 May 2023)
Cumulative views and downloads (calculated since 08 May 2023)

Viewed (geographical distribution)

Total article views: 615 (including HTML, PDF, and XML) Thereof 615 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 29 Nov 2023
Short summary
Water availability is essential for vegetation functioning, but the depth of vegetation water uptake is largely unknown due to sparse ground measurements. This study correlates the vegetation growth with soil moisture avaialbility globally to infer to vegetation water uptake depth using only satellite-based data. We find that the vegetation water-uptake depth varies across climate regimes and vegetation types and also changes during dry months on a global scale.