Aboveground biomass investments and light interception of tropical forest trees early in succession

Abstract

Background and Aims: Crown structure and above-ground biomass investment was studied in relation to light interception of trees and lianas growing in a 6-month-old regenerating forest. Methods: The vertical distribution of total above-ground biomass, height, diameter, stem density, leaf angles and crown depth were measured for individual plants of three short-lived pioneers (SLPs), four long-lived pioneers (LLPs) and three lianas. Daily light interception per individual Fd was calculated with a canopy model. The model was then used to estimate light interception per unit of leaf mass (Fleaf mass), total above-ground mass (Fmass) and crown structure efficiency (Ea, the ratio of absorbed vs. available light). Key Results: The SLPs Trema and Ochroma intercepted higher amounts of light per unit leaf mass (Fleaf mass) because they had shallower crowns, resulting in higher crown use efficiency (Ea) than the other species. These SLPs (but not Cecropia) were also taller and intercepted more light per unit leaf area (Farea). LLPs and lianas had considerably higher amounts of leaf mass and area per unit above-ground mass (LMR and LAR, respectively) and thus attained Fmass values similar to the SLPs (Fmass = Farea x LAR). Lianas, which were mostly self-supporting, had light interception efficiencies similar to those of the trees. Conclusions: These results show how, due to the trade-off between crown structure and biomass allocation, SLPs, and LLPs and lianas intercept similar amount of light per unit mass which may contribute to the ability of the latter two groups to persist. Key words: Bolivia, canopy model, crown structure, leaf mass ratio, lianas, light interception, pioneers, specific leaf area, tropical forest.