Contribution to the assessment of climate change effects on water balance in forest soil: application of the Biljou model to the cork oak forest of Ain Snoussi (north-western Tunisia)

Abstract

This study aims to analyse the availability and variability of soil moisture and its evolution considering climate change (CC) scenarios in a typical Mediterranean forest of cork oak (Quercus suber L.). The investigation was conducted in 3 forest stations at north-western Tunisia. Gravimetry and time domain reflectometry (TDR) were used to assess soil moisture. Biljou (BILan JOUrnalier), a daily water balance model, was applied to simulate the relative extractable water variation in 2009 as a reference simulation. Alike, other simulations of CC were performed using hypothetic meteorological and/or silvicultural data. The top-layer soil humidity fluctuates between 5 and 25% depending on time and stations. This oscillation interval narrows for the soils’ surface layer (7%). The forest surface conserves a soil moisture memory varying on a small spatial scale but stable over time. The deep layers of the three stations have the same way due to the attenuation of the biological and atmospheric influence. 2009’s reference simulation makes it possible to distinguish a low and slight period of stress easy to overcome (9 days with intensity 0.4). Soil drying severity, duration, and earliness will vary from one scenario to another. The number of days and the intensity of stress are high for all scenarios (64 to 166 days with intensity from 12 to 42.2). The most severe and persistent period of stress will be when the rain will be nil during summer and especially if summer period extends. CC impacts will be amplified when climatic and silvicultural scenarios are combined.