Examining the key roles of reforestation and termite mounds on soil properties and biodiversity in an agroforestry system in Cambodia

Abstract

In Cambodia, pepper (Piper nigrum) is cultivated intensively, primarily through uniform plantations where large areas are dedicated to a single variety. This study aimed to explore how the integration of reforested areas affects ecosystem functioning in agroforestry systems, with a particular focus on biodiversity, carbon storage in the soil, and water infiltration. Additionally, it focused on the specific role of termite mounds, which are known for their unique properties in natural ecosystems, but have never been studied in agroforestry systems. Eight years after the beginning of the reforestation, the area consisted of a forest, characterized by its specific vegetation and the presence of termite mounds, plantations of pepper, and paddy fields (Oryza sativa). These environments could be discriminated by their specific biological activity and diversity, and soil physical (soil texture, water hydraulic conductivity) and chemical (C, N, P, pH, electrical conductivity) properties. Except for the low tree diversity in pepper plantations, this environment was very similar to the forest, in terms of soil properties and soil fauna diversity, most likely due to the specific climate found in pepper plantations and the utilization of compost for increasing soil fertility. PLS-SEM models showed that the abundance of litter explained more soil chemical properties than tree diversity in the forest. This study also showed that the similar P content in forests compared to cultivated areas, which received organic fertilizers, could be explained by the restitution of P from litter. Finally, we demonstrated that termite mounds can be viewed as hotspots of fertility and biodiversity within the forests, emphasizing their potential use as soil amendment to enhance the fertility of the pepper and rice plantations.