Using GPR to analyze regeneration success of cork oaks in the Maâmora forest (Morocco)

Maâmora forest is considered as one of the world's largest cork oak forest. Located in North-West Morocco, it covers a total area of 133 000 ha. The forest consists of about 65 000 ha of cork oaks, while the rest of its area is covered by eucalyptus, acacias and maritime pines. In the past several decades, it has been suffering from degradation, yet it plays an important economic and social role. Studies identified that water balance (climate and soil factors) is one of the main factor that regulates the success of cork oak regeneration. In fact, the forest's soil is composed of a more or less deep sand layer (0.3 m - 6 m) laying above a clay layer. The overall goal of this thesis is to study the relationship between the growth of cork oaks and soil factors using GPR techniques. More specifically, it consists of first, setting up a lightweight frequency domain GPR then, studying the vigor of trees and detecting the soil properties that can lead to successful cork oak regeneration. The forest plot chosen for this study is located in B canton of Maâmora forest (plot VI-6) and has a high variability in terms of tree growth and regeneration success. It is also characterized by variable sand and clay layer depths. Two different GPR were used in this study: a lightweight frequency domain GPR, to map the surface soil moisture and a time domain commercial GPR, to detect soil textural transitions in depth. Results show that both GPR provided information on soil properties. Generally, the most humid areas were characterized by successful regeneration plots of cork oaks. Soil texture (red sands), clay layer depth (< 3.5 m), and clay structure (red clays of Maâmora) are among the factors that influence cork oak growth. Hence, GPR provided valuable results even though further soil analyses would allow to fully understand the soil water hydrodynamics.