Distribution pattern of total organic carbon in soils of micro tidal mangrove ecosystem in west coast of Sri Lanka

Abstract

Abstract soil organic carbon represents a significant pool of carbon within the biosphere, which estimated over three times of carbon that found in the atmosphere. Mangroves play a important role in the accumulating higher soil organic carbon among the other wet lands and terrestrial ecosystems, due to its superior in primary productivity and extensive root system enhances the trapping of sediments suspended in the tidal and flooding water currents. Study was focused on the stock of total organic carbon (TOC) and its horizontal and vertical distribution in mangrove soils of Negombo estuary, Sri Lanka. Two study sites, Kadolkele, a relatively undisturbed natural mangrove area and Wedikanda, a stand have been cultivated and sustainably utilized by fishermen to extract twigs and branches for “brush parks”. Highest TOC content (12.42 %) in its dry weight was recorded vertically at top soil layer (0-15 cm depth) and horizontally, between the zone 10- 30 m landwards from estuarine shoreline. Bulk density of mangrove soil ranged between 1.10 – 1.20 g cm-3 and lowest was recorded at upper layer and slightly increase with the depth. Highest amount of TOC was calculated, 204.93 t ha-1 at top soil layer (0 -15 cm) and observed decrease in vertically. TOC of 104.66 t ha-1 at 15 -30 cm depth and 68.58 t ha-1 at 30 - 45 cm depth respectively. A statically significant (p<0.05) positive correlation (r2 = 0.67) was revealed between TOC in mangrove soil and stem density.