Author : Wijarn Meepol

Summary : The study was conducted to determine the differences between mangroves at downstream and upstream of Klong Ngao, Ranong Province from June 1 2001 to May 31 2002. Two 200-m long transect lines in each site were established from seaward margin to landward. twenty 10 x 10 square meter plots were constructed in each transect line to study litter production stand structure, water salinity and soil properties. Results showed that mangroves at downstream had higher value in number of species than those at upstream (17 species at downstream and 13 species at upstream). While average densities of trees (2,160 stem/ha), saplings (1,130 stem/ha) and seedlings (1,795 stem/ha) of mangroves at upstream had higher values than at downstream (1,640; 597; 495 stem/ha, respectively). Water salinity of mangroves at downstream showed higher salinity than those at upstream in both wet and dry seasons. At downstream, water salinity were 22 and 33 ppt in wet and dry season, respectively while at upstream, 18 and 30 ppt. Mangrove soils at downstream were high in sand content while upstream soils in silt and clay contents. Both soils were high in organic matter, sulphur, and other nutrients. Mangrove soils at downstream and upstream were significantly different in sand, silt and clay contents at Ag, Cg1 and Cg2 horizons. However, for the chemical properties such as pH (air dried soils), electrical conductivity, organic matter, cation exchange capacity, total nitrogen, available phosphorus, exchangeable magnesium, sulphur and sodium were not significantly different at the Ag, Cg1 and Cg2 horizons between mangrove soils at downstream and upstream.