Is there anything new about determining the root-zone water-storage capacity over large areas?

Root-zone water-storage capacity (S_r) represents the maximum value of soil-water stored in the active soil profile, and available for vegetation growth. The mapping of S_r over relatively large spatial scales necessitates the assumption of simplified functions and characteristics of an agroecosystem. Currently, S_r is still determined by resorting only to soil attributes, such as the plant-available water (PAW) that is based on the concepts of field capacity and permanent wilting, as well as on a static determination of the depth of the uniform soil profile.

In this study, we propose a novel approach to identify S_r as an indicator of soil-vegetation functioning (hereinafter referred to as S_r,i), depending not only on soil properties but also on vegetation characteristics and climatic regimes. The integrated approach proposed in this study accounts for the following two factors: (i) the entire shape of the soil-water retention function, which is much more informative of the amount of energy required to remove soil-water for vegetation needs, as well as (ii) the maximum value of an effective rooting depth depending on both local weather condition and land use.

Our contribution to this session consists of two parts:

- A preliminary part takes advantage of a detailed field drainage experiment and aims at demonstrating the superior performance of the S_r,i indicator compared with PAW;

- The subsequent part discusses the result of mapping S_r,i on a regional scale.

We show that S_r,i, together with other single or compound indicators, can effectively contribute to gaining a better understanding of agroecosystem’s vulnerability to drought. Moreover, employing a probabilistic framework, S_r,i helps identify the most likely Priority Intervention Areas (PIAs) that require the implementation of tailored management strategies to enhance their potential resilience.

This study was partly carried out within the “Agritech National Research Center” and received funding from the European Union Next-Generation EU [Piano Nazionale di Ripresa e Resilienza (PNRR) – Missione 4 Componente 2, Investimento 1.4 – D.D. 1032 17/06/2022, CN00000022]. The outcomes of this research are within the action Spoke #3, Task 3.2.1, “Solutions for soil quality assessment and protection”. This presentation reflects only the authors’ views and opinions, neither the European Union nor the European Commission can be considered responsible for them.