Temporal and structural effects of stands on litter production in Melaleuca quinqueneriva dominated wetlands of south Florida.

Authors: Rayamajhi, Min; Van, Thai; Pratt, Paul; Center, Ted

Submitted to: Wetlands Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2005
Publication Date: 8/1/2006
Citation: Rayamajhi, M.B., Van, T.K., Pratt, P.D., Center, T.D. 2006. Temporal and structural effects of stands on litter production in Melaleuca quinquenervia dominated wetlands of south Florida. Wetlands Ecology and Management. 14:303-316.

Interpretive Summary: Melaleuca quinquenervia has dominated large areas of the Florida Everglades in the southeastern USA, where it has transformed once sedge-dominated marshes into melaleuca forests. In these areas, we measured tree girth, determined stand densities, and estimated aboveground biomass of melaleuca stands in 1997. We discovered that the diameter of melaleuca tree-trunk increases when the tree density in the stand decreases. On weight basis, live trees were made up mostly of woods and other (leaves, fruits, and flowers) plant parts were in smaller proportions. In the next step we collected and quantified the amount of small twig, leaf, flower and fruit falling from the melaleuca trees in these stands for the ensuing 4 -year period. We determined that: 1) overall amount of the fall of plant materials was highest during 1999-2000, 2) total amount of litterfall was highest in mature stands whereas leaf fall was highest in younger stands, 3) leaves were retained on trees for longer period of time in wet- than in dry locations, and 4) leaves, fine stems, mature fruits, bud scales, reproductive structures, and residues represented decreasingly smaller proportions of the total plant parts falling from trees. The fall of stems, leaves, flowers, and immature and mature fruits was consistently higher among large- than in medium- or small-tree stands. On the other hand, the fall of non-melaleuca plant materials was higher in small- than in medium- or large-tree stands, which indicated the presence of larger number of non-melaleuca plants in small- than in medium- or large-tree stands. Month-wise, fine-stem and mature-fruit fall occurred during February and November, which correlated with maximum wind speed during the year. Leaf fall occurred year-around but peaked during April, July, and October. Fall of the amount of bud-scales and reproductive structures was higher during October-January indicating the major vegetative growth and flowering events during these months.

Technical Abstract: 1) Melaleuca quinquenervia, an Australian invasive tree, now dominates large areas of the Florida Everglades in the southeastern USA, where it has transformed once sedge-dominated marshes into melaleuca forests. 2) We measured melaleuca stand attributes in non-flooded, seasonally flooded, and permanently flooded habitats in 1997 and quantified litterfall components over 3-4 years in late-, mid-, and early -phenostages of melaleuca stands. 3) Tree density varied inversely with trunk dbh, which in turn varied directly with basal area coverage, and aboveground biomass. Woody components and mature fruits comprised the major and minor portions of aboveground biomass, while leaves and mature fruits represented the most and the least litterfall amounts during the ensuing year. Total litterfall was highest in mature stands whereas leaf fall was greatest in young (early phenostage) stands. Leaf longevity increased with habitat wetness. 4) Leaves, fine stems, mature fruits, bud scales, reproductive structures, and residues represented decreasingly smaller proportions of the total litterfall. The leaf proportion was greatest (80.9%) in non-flooded and least (69.1%) in permanently flooded habitats; within habitats it was greatest in early (85.6%) and least in late (64.7%) phenostage stands. Reproductive structures and mature fruits had their highest representation in the litterfall within late phenostage stands while the bud-scales showed no particular trend associated with the phenological stage of the stand. 5) The overall amount of litterfall was greatest during 1999-2000. Amount of stems, leaves, reproductive structures, bud scales, immature and mature fruits, and residue fractions were consistently higher in late than in mid- or early-phenostage stands. The highest total melaleuca litterfall was 0.662, 0.882, and 1.128 kg m-2yr-1 in early-, mid-, and late-phenostages, respectively in seasonally flooded habitats. Non-melaleuca fractions within habitat were greater in early- than in mid- or late-phenostage stands. 6) Fine-stem and mature-fruit fall occurred during February and November and correlated (r > 0.70) with maximum wind speed. Leaf fall occurred year-around with peaks in April, July, and October. Fall of bud-scales and reproductive structures peaked during October-January indicating a major vegetative growth and flowering events but showed weak correlations (r < 0.70) with weather events.