Litter fall production and leaf decomposition in a mangrove stand (Lumnitzera racemosa Willd. community) in Songkhla Lake, Thailand

Litter fall production and leaf decomposition in a mangrove stand (Lumnitzera racemosa Willd. community) in Songkhla Lake, Thailand

Saowapa Angsupanich, Assoc. Prof., D. of Aquatic Sci., F. of Natural Resources, PSU.
Nipit Srisuwon, F. of Environmental Management, PSU.
Somsak Maneepong, D. of Earth Sci., F. of Natural Resources, PSU.
Corresponding e-mail : asaowapa@ratree.psu.ac.th

Grant : TRF/BIOTEC, Thailand
Presented : The 11th JSPS Joint Seminar on Marine Science, 20-22 November 2000 at National Olympics Memorial Youth Center, Tokyo, Japan
Key words : litter fall, leaf decomposition, Lumnitzera racemosa, Songkhla Lake

The study describes litter fall and leaf decomposition at the mangrove site in the inner Songkhla Lake of southern Thailand where Lumnitzera racemosa Willd. is the dominant species. The total annual litter production was 1,543 g dry weight m^-2y^-1. Eighty four percent was L. racemosa litter (1,299 g DW m^-2y^-1). Its leaf litter was the main component (1,069 g DW m-2y-1). The leaf and flower litter peaked during the heavy rainy season with maximum production in October, although there was no significant difference among seasons. The fruit litter was the second most important component and it was significantly higher (P<0.05) in the heavy rainy season than in other seasons. The total nutrient contents calculated from the total L. racemosa leaf litter fall in a year were 453.0 g DW m^-2 for carbon, 27.2 g DW m^-2 for calcium, 9.6 g DW m^-2 for potassium, 7.7 g DW m-2 for magnesium, 5.8 g DW m^-2 for nitrogen, 0.43 g DW m^-2 for phosphorus and 2.5 g DW m^-2 for sulfur.

The amount of leaf litter lost through decomposition on various substrates was different. The loss rate of leaf litter materials was highest when placed at sites which were submerged all of the year (98% in 3 months) while a lower rate occurred at sites which only sometimes flooded (62.86% in 3 months). The most rapid decay of leaf litter took place within the first 4 weeks of immersion in seawater and thereafter the rate gradually decreased.

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