Effects of Leaf and Ramet Removal on Growth and Reproduction of Geonoma Congesta, A Clonal Understorey Palm

Abstract

SUMMARY (1) The responses of Geonoma congesta, a clonal understorey palm, to leaf and ramet removal were examined in sixty clones under natural field conditions in a Costa Rican rain forest. Fifteen clones, each with eight or fewer stems, were assigned to each of four treatments: (a) control (no manipulation), (b) removal of all but one ramet, (c) removal of 50% of the leaves from one ramet, and (d) removal of all but one ramet plus removal of 50% of the leaves. Ramet growth, new ramet production and reproductive activity were monitored annually for 3 years. (2) Ramet and leaf removal alone did not significantly increase mortality over controls, but mortality was significantly increased when both ramets and leaves were removed. Leaf and ramet removal had no significant effect on height-growth and stem-growth increments. Leaf size and stem diameter after 3 years were not influenced by leaf removal or ramet removal. Defoliated ramets had a significantly higher annual rate of leaf production per initial number of leaves than non-defoliated ramets, whereas ramet removal showed no significant effect on leaf production of the remaining ramet. (3) The number of clones producing at least one new sprout during the 3-year period did not vary significantly among treatments, nor was a significant difference observed in the total number of new sprouts produced per treatment. Ramet removal resulted in a significant decrease in the number of clones producing reproductive ramets, whereas leaf removal had no significant influence on the probability of reproduction within clones. On a ramet basis, the cumulative number of reproductive structures produced over 3 years was not significantly affected by either ramet or leaf removal treatments, nor was an interaction between treatments observed. (4) Clones of G. congesta are remarkably resistant to repeated defoliation and ramet removal. These results suggest that stored reserves are mobilized to maintain normal patterns of growth and ramet production following defoliation. Clonal growth in this species appears to buffer individual ramets against traumatic effects of ramet and leaf removal on growth, survival and reproduction.