Intertwining observations and predictions in vadose zone hydrology: A review of selected studies.

Observing state variables, fluxes, and key properties in terrestrial ecosystems should not be seen as disjointed, but rather as fruitfully complementary to ecosystem dynamics modeling. This intertwined view should also take the organization of the monitoring equipment into due account. This review paper explores the value of the interplay between observations and predictions by presenting and discussing some selected studies dealing with vadose zone hydrology. I argue for an advanced vision in carrying out these two tasks to tackle the issues of ecosystem services and general environmental challenges more effectively. There is a recognized need to set up networks of critical zone observatories in which strategies are developed and tested that combine different measurement techniques with the use of models of different complexity.