Modeling the stipe growth of the Oenocarpus bataua palm in the Central Cordillera of the Andes, Colombia

Abstract

Over 9.4years in the premontane natural forest of Colombia, we measured the annual rates of growth in length (RGL) of the stipes, the stipe length (l) and the annual rates of leaf scars (RLS) in 109 palms of Oenocarpus bataua. We counted leaf scars on the stipes and the leaves of the crown of each palm (SPL) and determined the position of the scar from the first inflorescence on 79 stipes. The RLS are not correlated with the RGL, are not constant and show negative allometry with l. We correct the RLS of each palm with the mean value of a function to obtain the mean rates of leaf scars (MRLS). We estimate the age (t) for each l, dividing SPL by MRLS for each l. We model l as a function of t in years using von Bertalanffýs growth model (l=f(t)) and the relative growth in length, RGL ((1/l)dl/dt=f(t)), which we integrate to obtain a new expression of von Bertalanffýs growth model. For the same ages, both growth equations estimate very similar values of l that are not significantly different from the values of l for 27 palms whose ages were determined using 14C bomb dating. By averaging the values of the two growth equations, we obtained the following results regarding the life history of O. bataua: (i) the life span once the elongation of l begins is 169years, (ii) the half-life is 35years, (iii) the mean residence time is 33.3years, (iv) the maximum RGL(dl/dt) is 0.37myear−1 and occurs at 17.3years, (v) and the maximum l/t, is 0.31myear−1 and occurs at age 31. Moreover, the age of the first reproductive event occurs at 18.03±6.08years and at l heights of 5.53±1.79m.