Transplanted seedling age and watering effects on the field performance of Senegalia macrostachya (Rchb. ex DC.) Kyal. & Boatwr., a high-valued indigenous fruit tree species in Burkina Faso

Abstract

Senegalia macrostachya, ex-Acacia macrostachya is a multiple-use species providing many benefits to populations in arid and semi-arid regions. Despite its importance, limited research has been undertaken on its silviculture, growth, and productivity in plantations or in the wild. In this paper, we widely deployed the Generalized Additive Models for Location, Scale and Shape to identify factors controlling the temporal variability in S macrostachya annual pod and seed production. Data (survival rate, basal diameter, total height of each individual tree, and weight of pods and seeds produced) were collected from a factorial experiment testing different nursery production periods and the field performance of S. macrostachya under well-watered and water-stressed conditions. Long-term climate data were analyzed and the Standardized Precipitation–Evapotranspiration Index (SPEI) was calculated. Results showed that seedling survival and both height and radial growth were significantly influenced by seedling age at outplanting, watering, and climate aridity. The watered seedlings had the highest survival rate and grew taller than the non-watered seedlings. The watered seedlings also had the largest basal diameters, along with the highest pod and seed weights. There was temporal variation in S. macrostachya pod and seed production over time, indicating a cyclic production, depending mainly on climate factors. Seedling age at outplanting, early watering of outplanted seedlings, and climate aridity significantly influence not only seedling survival and growth parameters but also determine the levels of pod and seed production of S. macrostachya. Our results provide field-based evidence of the performance of this important species in the production of pods and seeds. The results also highlight the potential for domestication of S. macrostachya including use in plantations to help restore degraded rural landscapes in arid and semi-arid regions.