Variation of Natural Recruitments, Root Yield and Belowground Carbon Stocks between a Forest Gap and Uncut Forest in Rekawa Mangroves, Sri Lanka

Abstract

Researches are scanty for comparing the belowground biomasses and carbon stocks betweenman-made gaps and uncut areas of Sri Lankan mangrove forests. In order to reduce this studygap, a 6 years old forest gap and adjacent uncut forest area were selected from a Ceriopstagalstand (06o 02/ N and 80o 50/ E) in Rekawa Lagoon Sri Lanka and three 5 m x 5 m plots weresampledin each site for comparing the belowground root biomasses (obtained from two rootcores: 60 cm deep and 15cm diameter, from each plot) and root carbon contents (determinedby loss on ignition).

The uncut forest area had significantly higher tree (height above 150 cm) densities (1.0 ± 0.1m-2) than the gap (0.45 ± 0.3 m-2) area (Mann-Whitney U Tests; P<0.05). The uncut foresthad significantly higher fine and medium root dry weights (1260 ± 182 and 1166 ± 200 gm-2respectively) over the gap (612.0 ± 114.0 and 597.8 ± 164.1 gm-2 respectively). The dryweights of coarse and total roots of the gap (4245 ± 452, 5454 ± 715gm-2 respectively) andthe uncut forest (3664 ± 516, 6089 ± 884 gm-2 respectively) were not differed significantly(Two sample t-test, p>0.05).

The carbon contents of fine, medium, coarse and total roots between the gap (126.1 ± 18.2,105.1 ± 19.5, 50.1 ± 8.6, 284.6 ± 38.1gm-2 respectively) and the uncut forest (107.4 ± 15.1,95.8 ± 15.7, 41.7 ± 6.8, 244.5 ± 35.3 gm-2 respectively) were not differed significantly (Twosample t-test, p>0.05).

Unchanged belowground dry weight and hence the unaffected root carbon contents in the gapwould imply growing of new roots in to the gap area from surrounding trees for absorbingnutrients from decaying stumps.