Effects of leaf harvest on Thrinax radiata palm: implications for management and conservation

For centuries, Mayans have used Thrinax radiata leaves for roof thatching and broom manufacturing. To determine sustainable leaf harvest levels, an evaluation was done to study the effects of four harvest regimes on individual-level and leaf-level responses. Four leaf harvest (i.e. defoliation) intensities were simulated: control (0%); low (30%); intermediate (70%); and high (100%), following traditional practices. Readings were taken every six months over an 18-month period to record survival, trunk height, leaf production and new leaf nitrogen content. Low intensity harvest (30%) increased leaf size but had no effect on leaf production. On the contrary, six months after harvest, individuals in the 100% treatment produced more leaves than the control. However, this treatment negatively affected future growth, which was reflected in decreasing leaf number and size, 18 months post-harvest. New leaf nitrogen content was unaffected by harvest intensity, suggesting that the mechanism responsible for compensation of lost tissue in T. radiata is primarily mobilization of carbohydrate reserves, and not an increase in leaf nitrogen content. Thirty per cent defoliation of palm crown is suggested as a sustainable leaf harvest level to ensure no effect on leaf size and rapid recovery of initial leaf number.