Introduction and ecological effects of an exotic mangrove species Sonneratia apetala

Mangroves are typically found in tropical coastal areas, and these ecosystems face deterioration and loss due to threats from climate and human factors. In this study, sediment cores were collected from human-planted mangroves in sub-tropical Ximen Island, China, and were determined for sedimentary phosphorus (P) species. The objective was to investigate the ability of mangroves planted in a zone bordering their temperature limit to preserve and regulate P. Our results showed that bioavailable P (BAP), which includes exchangeable-P (Ex-P), iron-bound P (Fe-P), and organic P (OP), accounted for approximately 64% of total P (TP). Apatite P (Ca-P), which accounted for 24% of TP, most likely originated from aquaculture activities surrounding the island. The vertical distribution of sedimentary P species along the sediment cores showed a rather constant trend along the salt marsh stand but considerable fluctuations for the mangroves and bare mudflat. These results indicate that mangroves accumulated P when there was a high P discharge event, and that this P was eventually released during organic matter decomposition and contributed to Ca-P formation. Nevertheless, old and young mangroves accumulated higher sedimentary P species, OP, and BAP compared to the salt marsh stand and bare mudflat areas. This study showed the potential of mangroves planted outside their suitable climate zone to preserve and regulate P.

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Geochemical Behavior of Sedimentary Phosphorus Species in Northernmost Artificial Mangroves in China

Mangroves are highly productive blue carbon ecosystems that preserve high organic carbon concentrations in soils. In this study, particle size, bulk elemental composition and stable carbon isotope were determined for the sediment cores collected from the landward and seaward sides of two mangrove forests of different ages (M1, ca. 60; M2, ca. 4 years old) to determine the effects of geomorphic setting and age (L1 = old mangrove and S1 = salt marsh stand in M1; L2 = young mangrove and S2 = bare mudflat in M2) on sediments and organic carbon accumulation. The objective of this study was to determine the feasibility of the northernmost human-planted mangroves in China to accumulate sediment and carbon. Our results showed that fine-grained materials were preserved well in the interior part of the mangroves, and the capacity to capture fine-grained materials increased as the forest aged. The biogeochemical properties (C/N: 5.9 to 10.8; δ13C: −21.60‰ to −26.07‰) indicated that the local organic carbon pool was composed of a mixture of autochthonous and allochthonous sources. Moreover, the accumulation of organic carbon increased with the forest age. The interior part of the old mangrove had the highest organic carbon stock (81.93 Mg Corg ha−1). These findings revealed that mangrove reforestation had positive effects on sediments and organic carbon accretion.

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Assessing the Effect of Age and Geomorphic Setting on Organic Carbon Accumulation in High-Latitude Human-Planted Mangroves

Mangrove forests, which occur in the intertidal regions of tropical and sub-tropical zones, have high ecological and economic values. They have rapidly reduced over the past decades due to various reasons. Reforestation is a common strategy for the conservation of mangroves, but information on the renewal capacity and viability of these artificial mangrove populations is still lacking. Here, we estimated the effective population size (NE) of an artificial population of Kandelia obovata (Rhizophoraceae) and explored the effects of intrinsic and extrinsic factors on changes in NE to evaluate population viability and develop appropriate management strategies for mangrove forests. This population consisted of three ecologically and genetically differentiated groups that had experienced a major low-temperature event during the winter of 2015–2016 and varied in cold resistance. We first detected population bottlenecks and estimated contemporary values of NE for different groups using microsatellite data. Next, we performed paternity analyses for seedlings and propagules to explore variations in the reproductive success of individuals within the three groups before and after the low-temperature event. Lastly, we simulated four scenarios to characterize the effects of low temperature, mating system, and variance in reproductive success on changes in NE in a hypothetical metapopulation based on empirical estimates. Our results show that groups with moderate or poor cold resistance experienced local bottlenecks, and shifts in effective breeders occurred following the low-temperature event, which indicates that low temperature has an effect on not only population size but also reproductive success. Furthermore, our simulations revealed that changes in NE are jointly affected by reproductive success, mating system, and environmental conditions. These findings enhance our understanding of the multiple factors that affect NE, and provide key information that will aid the reforestation and management of mangrove forests, especially when they are introduced to high-latitude areas.

Survive the north: transplantation for conservation of mangrove forests requires consideration of influences of low temperature, mating system and their joint effects on effective size of the reforested populations

To screen out the introduced mangrove species adaptive to the natural conditions in Wenzhou area,different provenances of mangrove species were experimented with and the annual growth of the experiment plots was investigatedThe results showed that survival rate of Kandelia candel,Sonneratia apetala,Aegiceras corniculatum and Excoecaria agallocha was 77%,73%,70% and 15% respectively,indicating the former 3 species could overwinter safely in the studied areaWhereas all the saplings of Laguncularia racemosa,Bruguiera gymnorhiza,Bruguiera sexangula varrhynchopetala,Rhizophora stylosa,Acanthus ilicifolius and Avicennia marina died in the winterCompared to the values measured in the summer,the increment amplitude of relative conductivity(RC) value of the tested species at 0℃ temperature was in the order that of Laguncularia racemosa Sonneratia apetala Aegiceras corniculatum one-year-old Kandelia candel eight-year-old Kandelia candelThe maximum increase of superoxide dismutase(SOD) value happened to Aegiceras corniculatum whose value measured at 0℃ increased by 105% compared to that of measured in the summerWhile the SOD values of Kandelia candel and Laguncularia racemosa did not change much with the seasonsThe proline(PRO) content in the leaves of Laguncularia racemosa in the winter increased by 2854% compared to the summer value,but there was very little change in this index for Sonneratia apetala and eight-year-old Kandelia candel along the seasonal changeThe comprehensive analyses showed that Sonneratia apetala,Aegiceras corniculatum,Excoecaria agallocha and Kandelia candel could safely survive the winter in the south part of Zhejiang Province,while the adaptability of other mangrove tree species to the studied area should be further experimented

Zheng Jian

Papers

Preliminary report on north-ward introduction experiment of several mangrove plants along the southern coast of Zhejiang Province.