Abstract

TORRES, Rubén; LUGO, Carlos; GORDON, Elizabeth  and  SUAREZ-VILLASMIL, Lourdes. In situ leaf decomposition of heliconia marginata in a herbaceous wetland (Barlovento, Venezuela). Polibotánica [online]. 2013, n.35, pp.21-40. ISSN 1405-2768.

Herbaceous wetlands are among the most productive ecosystems in the world; this is due to the biogeochemical processes associated with emergent plants, their high production and continuous decay of dead organic matter. We did a field experiment on an herbaceous wetland in Barlovento (Venezuela) to quantify the Heliconia-marginata (Heliconiaceae) decomposition coefficient under natural conditions, in a zone where this plant forms a monoespecific community across the southwest border of the wetland. The leaves were collected, dried, stored on decomposition bags and incubated in situ for 68 days. At specific times the bags were taken to quantify the ash-free dry weight. Also, we measured some abiotic variables (pH, conductivity, temperature, dissolved oxygen, and water depth). The abiotic variables did not change in a statistically significant way during the experiment. The leaf decomposition of H. marginata showed two stages: moderately fast decomposition during the first four days, with 13% loss of the initial ash-free dry weight, and a second stage with a lower weight loss. The decomposition rate of H. marginata was 0.0068 days^-1, in agreement with figures of other emergent species with high decomposition rates. The mean time required to break down 50% of vegetal biomass (t₅₀) was 147 day, but the incubation period only included washing of the sample. A folivorous and detritivorous fauna was almost absent; this suggests that the H. marginata low decomposition rate could be explained by the structural characteristics of the litter, which produces a slow decomposition and recycling rate of the organic matter.

Keywords : decomposition; ecosystem process; leaves fractionation; herbaceous wetlands; emergent plants; Heliconia marginata; Venezuela.

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