Temporal and spatial variability in photosynthetic activity of Vitellaria paradoxa in agroforestry parklands of Burkina Faso

The Vitellaria paradoxa) is a key woody species in sub-Saharan Africa, supporting the livelihood of over 18.4 million people - particularly women. However, its survival and productivity are increasingly threatened by climate change, characterized by raising temperatures and reduced water availability. The species’ future resilience will depend on its physiological adaptability to shifting climatic conditions. To assess this adaptability, we studied photosynthetic performance of 24 shea trees in situ from April to December 2023 the most active period of leaf phenology across two contrasting climatic zones in Burkina Faso. We evaluated how photosynthetic efficiency responded to climatic variability over this nine-month period. Unregulated energy dissipation (φNO) and regulated energy dissipation in the form of heat (φNPQ) were significantly different (P < 0.001) between phytogeographic zones during monitoring period. The chlorophyll content was significantly higher (P < 0.001) in leaves from humid southern Sudanian phytogeographic zone (42.9 ± 0.4 SPAD) than in drier northern Sudanian zone (40.8 ± 0.37 SPAD). Linear regression showed a significant increase in protective energy dissipation (NPQt) in response to instantaneous photosynthetically active radiation in shea leaves from dryer northern site (R²=0.4). Additionally, leaf temperature was strongly correlated with ambient temperature, explaining 78–84% of variations (P < 0.001). Overall, V paradoxa from the more humid southern site zone exhibited better photosynthetic performance. These findings highlight spatial differences in photosynthetic responses and provide valuable insights about which photosynthetic parameters are affected by climate change. This can pave the way for management options to cope with climate change effects.