RESUMO
Salinity is among the most critical factors limiting the growth and species distribution of coastal plants. Water salinity in estuarine ecosystems varies temporally and spatially, but the variation patterns across different time scales and salinity fluctuation have rarely been quantified. The effects of salinity on floristic diversity in mangroves are not fully understood due to the temporal and spatial heterogeneity of salinity. In this study, we monitored water salinity at an interval of 10-min over one year in three mangrove catchment areas representing the outer part, middle part, and inner part respectively of Dongzhai Bay, Hainan, China. The number of mangrove community types and dominant mangrove species of the three catchment areas were also investigated. We found that the diurnal variation and dry-season intra-month variation in water salinity were driven by tidal cycles. The seasonal variation in water salinity was mainly driven by rainfall with higher salinity occurring in the dry season and lower salinity occurring in the wet season. Spatially, water salinity was highest at the outer part, intermediate at the middle part, and lowest at the inner part of the bay. The intra-month and annual fluctuations of water salinity were highest at the middle part and lowest at the outer part of the bay. The number of mangrove community types and dominant species were lowest at the outer part, intermediate at the middle part, and highest at the inner part of the bay. These results suggest that the temporal variation of water salinity in mangroves is driven by different factors at different time scales and therefore it is necessary to measure water salinity at different time scales to get a complete picture of the saline environment that mangroves experience. Spatially, lower salinity levels benefit mangrove species richness within a bay landscape, however, further research is needed to distinguish the effects of salinity fluctuation and salinity level in affecting mangrove species richness.
RESUMO
The complete mitochondrial genome of an endangered mangrove plant: Scyphiphora hydrophyllacea was analyzed in this paper, which is the first for the genus within the family Rubiaceae. The mitogenome sequence is 354,155 bp in length containing 3 ribosomal RNA genes, 16 transfer RNA genes, and 37 protein-coding genes. Gene ccmFc, ccmFn, rps3, rps13, rps10, rpl12, nad3 and cox1 contain one intron, gene cox2 and atp9 contain three introns and gene nad1, nad4 and nad7 contain four introns. Furthermore, Gene nad2 and nad5 have five introns. Gene nad1, nad2, nad5, nad7and Cox2 are trans-splicing genes. Phylogenetic analysis using the maximum likelihood method positioned S. hydrophyllacea closely with Asclepias syriaca in Gentianales.
RESUMO
Contrary to the global trend, the area of mangrove in Guangdong Province, southern China, has been increasing over the last two decades. Currently, three exotic mangrove species have been introduced for large-scale afforestation since 1985. A reassessment of the overall status of the mangrove species, habitat change, population of introduced species, was conducted through a comprehensive literature review as well as field investigations covering 96 sites. The success of conservation efforts is also evaluated. Upstream and high intertidal habitats are more vulnerable than downstream and lower intertidal ones, with habitat alteration being the biggest threats. Five mangrove species have narrow distributional extents with small populations, which could incur regional extinction. With the introduced species having naturalized at 42 sites, their role in mangrove management needs to be reconsidered. These findings collectively suggest a need to manage latent species loss and habitat degradation beyond the apparent increase in mangrove area and protection.