Abstract: Based on the measurement of biomass and productivity, the caloric value of different fractions of two species in S.apetala-S.caseloris forest, and their standing crop of energy and net energy production were determined. There were some differences in caloric values among the fractions of S. apetala and S. caseloris, and the caloric value of leaf was the highest,while that of the fine roots was the lowest. The caloric values of various fractions of S.apetala were much higher than those of S.caseloris .The standing crop of energy in S.apetala S.caseloris forest was 84744.72 kJ穖^-2 . The standing crop of energy accumulated in S. apetala population was 54693.26 kJ穖^-2, accounting for 64.54 % of the total, and that of S.caseloris population was 30051.46 kJ穖^-2, accounting for 35.46%. The energy return value of litters was 24549.54 kJ穖^-2 穣r^-1,that of S.apetala population was 17233.99 kJ穖^-2 穣r^-1 (accounting for 70.16%), and that of S.caseloris population was 7325.55 kJ穖^-2 穣r^-1 (29.84%).The net energy production was 50391.4 kJ穖^-2 穣r^-1 for S. apetala S. caseloris forest in1999, in which the net energy production of S. apetala population was 31778 kJ穖^-2 穣r^-1 .

Key words: Sonneratia apetala, Sonneratia caseloris, Caloric value, Energy, Futian of Shenzhen, carbonation, carbon sink, steel slag, greenhouse gas inventory, uncertainty