Seasonal occurrence and diel locomotor activity in littoral Cladocera in a mesohumic lake in Norway

The community structure and standing crop biomass of a mangrove forest in Futian Nature Reserve, Shenzhen, the People's Republic of China was studied. This mangrove, located towards the northern latitudinal limit of the mangrove development (22°N), had relatively simple structure and low diversity (the Shannon-Wiener index was 0.78). The three dominant species, namely Aegiceras corniculatum, Kandelia candel and Avicennia marina, possess importance values of 72, 19 and 9%, respectively. The average height of the mangrove community was 4.5 m with no vertical stratification. The values of tree density of A. corniculatum and A. marina were found to be 5290 and 260 ha^–1, respectively. The biomass of both A. corniculatum and K. candel was best estimated from regression equations using a combination of height and diameter at breast height as the independent variables. For Avicennia marina, there was no simple correlation between biomass and height or diameter. The regression models suggested by previous workers did not give satisfactory estimation of biomass of A. marina in this mangrove forest. The total biomass of this mangrove forest was 12.1 kg m^–2, with 73% of such production contributed by A. corniculatum and 8% by A. marina. Because of its small percentage, the inaccuracy in estimating biomass of A. marina did not affect the overall determination of biomass of the whole community. Average above-ground biomass was 8.7 kg m^–2 (72% of the total biomass) and the major components were aerial woody tissues, stems and branches. The root:shoot ratio of this plant community was 0.4:1.