[Net primary productivity of several mangrove species under controlled habitats]

Three mangrove species Sonneratia caseolaris, Kandelia candel and Aegiceras corniculatum were planted in different fishponds in April 2002 with three planting--breeding area proportions of 45 : 55, 30 : 70 and 15 : 85, respectively, and the growth of test mangrove plants were surveyed during 2 years after planting. The results showed that S. caseolaris and A. comiculatum could grow well in the coupling system, while K. candel could not. The survival percentage of S. caseolaris, K. candel and A. corniculatum was 92.9%, 93.9% and 44.7%, respectively. During the 2 years, the height of S. caseolaris increased 457.0 cm, and its basal diameter increased from 12.6 mm to 98.7 mm. A. corniculatum had an increment of 26.1 cm in height and 36.5 mm in basal diameter, while K. candel only had an increment of 20.4 cm in height and 26.4 mm in basal diameter. Based on the height, basal diameter, and biomass of trunk, branch, leaf and root, regressive equations of the four organs' biomass were obtained, and the whole biomass of standing trees in the coupling system was calculated. The average biomass of S. caseolaris was 5 597.8 g x m(-2) in April 2004, being increased 5 559.5 g x m(-2) in 2 years. At the same period, the standing biomass of A. corniculatum and K. candel was 962.5 g x m(-2) and 66.0 g x m(-2), with an increase of 932.7 g x m(-2) and 57.0 g x m(-2), respectively. The biomass of plant organs was in the order of stem > branch > root > leaf for S. caseolaris, leaf > branch > stem > root for A. corniculatum, and stem > root > leaf > branch for K. candel. The litter fall production of mangrove plants in 2 years was 1 149.2 g x m(-2), 170.8 g x m(-2) and 7.1 g x m(-2) for S. caseolaris, A. corniculatum and K. candel, respectively. Leaf litter took up more than half of the whole litter fall. From April 2002 to April 2004, the net primary production of S. caseolaris, A. corniculatum and K. candel was 7 048.9 g x m(-2), 1 105.9 g x m(-2) and 93.0 g x m(-2), respectively. The litter fall production occupied 20.5% of the net primary production for S. caseolaris, 15.4% for A. corniculatum, and 7.6% for K. candel, which meant that high productivity was accompanied by high return rate.