Litter accession and accumulation in a Melaleuca quinquenervia (Cav.) S.T. Blake wetland in south-eastern Queensland

Abstract

Litterfall and litter accumulation were investigated over two years in a Melaleuca quinquenewia wetland in south-eastern Queensland. In 1992, a seasonally wet year, litterfall was 809 ± 135 g m^-2 yr^-1 at the floodplain site and 764 ±192 g m^-2 yr^-1 at the riparian site, of which Melaleuca leaf litter made up 65% and 56% respectively. Litterfall was significantly lower and more variable in 1993, a drought year, being 725±106 g m^-2 and 675 ± 216 g m^-2 year^-1. There was a distinct seasonal pattern, with peak leaf litterfall occurring in spring in 1992 but extending into summer in 1993. Melaleuca leaf fall was significantly lower in 1993, possibly because drought conditions caused greater leaf longevity.

Litter accumulation on the forest floor was 3457 g m^-2 at the floodplain site and 2320 g m^-2 at the riparian site; there was no significant difference between years, although the organic matter content of the litter was lower in 1992, possibly as a result of leaching during flooding. Carbon content decreased with decreasing particle size of the litter, whereas nitrogen and phosphorus increased. There was no evidence to suggest leaching of nitrogen or phosphorus, and the high C: N: P ratios indicate slow rates of litter decay. The high accumulation of litter mass suggests that these woody wetlands may function as nutrient sinks.