Investigation of the Architecture and Age of Superlative Adansonia grandidieri from the Andombiry Forest, Madagascar

Abstract

Over the past years, our research on baobabs mainly focused on the largest Malagasy species, namely the Reniala or Grandidier baobab (Adansonia grandidieri Baill.). The biggest A. grandidieri are located in the Morombe area, especially in the so-called Andombiry Forest. This giant forest of Reniala hosts well over 6000 mature individuals, out of which more than 30 have very large sizes, i.e., circumferences over 20 m. We investigated, measured and dated by AMS radiocarbon the largest specimens. We found that all large Grandidier baobabs are multi-stemmed. They mostly exhibit a closed ring-shaped structure, with a false cavity inside. In this architecture, which enables Grandidier baobabs to reach very large sizes, the stems that build the ring typically have similar ages. Here we present the AMS radiocarbon investigation of two large baobabs, A 215 (girth 21.50 m) and A 257 (girth 25.70 m). According to dating results, the baobab A 215 has an age of only 375 years. It consists of four fused stems and has a closed ring-shaped structure. The baobab A 257 has the second largest trunk of all known live Reniala trees. It also exhibits a closed ring-shaped structure, with five fused stems around a false cavity, which has an opening toward the exterior. The dating results indicate that A 257 is around 900 years old.