From Ghana to China dry-hot valley: Assessing factors influencing fruit yield in agroforestry species Vitellaria paradoxa after 54 years of cultivation outside Africa

Although distributed across the Sudano-Sahelian region as an agroforestry system tree species, Vitellaria paradoxa has yet to be reported as successfully established outside of Africa, significantly limiting its yield and further exploitation. In this paper, in order to assess a well-established population of V. paradoxa in the Yuanjiang dry-hot valley of China and examine the relationships between morphological-geological factors and fruit yield, we monitored dendrometric traits and fruiting across 844 shea trees located on different aspects, and applied partial least square regression to build a yield model based on dendrometric and geographical variables. Results revealed climatic resemblance of the introduction site in Yuanjiang to the natural habitat in Ghana, and the growth performance and fruit yield were also comparable, but accumulated precipitation of about 600 mm was better for fruit yield when heat accumulation reached about 2,000 °C. Apart from crown diameter (p < 0.05), dendrometric parameters (basal diameter, basal area and tree height) had positively weak relationships with fruit yield. On the contrary, aside from north and northeast aspect, other aspects showed a strong negative influence. The findings presented that growth and productivity of V. paradoxa increased with dendrometric parameters and monthly average temperature on shady and semi-shady slope, providing a theoretical basis for the development of shea tree and construction of agroforestry system in dry tropical areas outside Africa.