First Age-Estimation Model for Dracaena ombet and Dracaena draco subsp. caboverdeana

Abstract

Research Highlights: The first model for crown age estimation was developed for Dracaena ombet Heuglin ex Kotschy and Peyr. and D. draco subsp. caboverdeana Marrero Rodr. and R. Almeida. Background and Objectives: Dracaena species are monocotyledon trees without annual tree rings. Most arborescent dragon tree species are endangered; thus, it is important to determine the age structures of these populations for proper conservation management strategies, and for modelling of population trends. For these reasons, it is necessary to develop a methodology of crown age estimation. Materials and Methods: Field data were collected in the Desa’a Forest (Ethiopia) and in Santo Antão (Cape Verde Islands). Trees within each age class, as expressed by the number of branch orders, were measured. The diameter at breast height, tree height, stem height, number of branch orders, number of all leaf rosettes and number of flowering leaf rosettes within the crown were recorded for each sampled tree. The flowering probabilities were counted as input data for the model used. Results: The duration of the interval between flowering events was 5.23 years for D. ombet and 4.94 years for D. draco subsp. caboverdeana. The crown of the oldest tree of D. ombet with 18 branch orders was estimated to be 94.2 years old, and the crown of the oldest tree of D. draco subsp. caboverdeana with 22 branch orders was estimated to be 108.6 years old.