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In mangrove forests, soil salinity is one of the most significant environmental factors determining mangrove forest distribution and productivity as it limits plant water uptake and carbon gain. However, salinity control on mangrove productivity through plant hydraulics has not been investigated by existing mangrove models. Thus, we present a new individual-based model linked with plant hydraulics to incorporate physiological characterization of mangrove growth under salt stress. Plant hydraulics was associated with mangroves nutrient uptake and biomass allocation apart from water flux and carbon gain. The developed model was performed for two-coexisting species of Rhizophora stylosa and Bruguiera gymnorrhiza in a subtropical mangrove forest in Japan. The model predicted that the productivity of both species was affected by soil salinity through downregulation of stomatal conductance, while B. gymnorrhiza trees grow faster and suppress the growth of R. stylosa trees by shading that resulted in a B. gymnorrhiza-dominated forest under low soil salinity conditions (B. gymnorrhiza compared to R. stylosa, leading to an increase in biomass of R. stylosa despite the enhanced salt stress (> 30 ‰). These predicted patterns in forest structures across soil salinity gradient remarkably agreed with field data, highlighting the control of salinity on productivity and tree competition as factors that shape the mangrove forest structures. The model reproducibility of forest structures was also supported by the predicted self-thinning processes, which likewise agreed with field data. In addition, the mangroves morphological adjustment to increasing soil salinity – by decreasing transpiration and increasing hydraulic conductance – was reasonably predicted. Aside from the soil salinity, seasonal dynamics in atmospheric variables (solar radiation and temperature) was highlighted as factors influencing mangrove productivity in a subtropical region. The physiological principle-based improved model has the potential to be extended to other mangrove forests in various environmental settings, thus contributing to a better understanding of mangrove dynamics under future global climate change.

Aim: Mangrove wetlands span broad geographical gradients, resulting in functionally diverse tree communities. We asked whether latitudinal variation, allometric scaling relationships and species composition influence mangrove forest structure and biomass allocation across biogeographical regions and distinct coastal morphologies. Location: Global. Time period: Present. Major taxa studied: Mangrove ecosystems. Methods: We built the largest field‐based dataset on mangrove forest structure and biomass to date (c. 2,800 plots from 67 countries) to address macroecological questions pertaining to structural and functional diversity of mangroves spanning biogeographical and coastal morphology gradients. We used frequentist inference statistics and machine learning models to determine environmental drivers that control biomass allocation within and across mangrove communities globally. Results: Allometric scaling relationships and forest structural complexity were consistent across biogeographical and coastal morphology gradients, suggesting that mangrove biomass is controlled by regional forcings rather than by latitude or species composition. For instance, nearly 40% of the global variation in biomass was explained by regional climate and hydroperiod, revealing nonlinear thresholds that control biomass accumulation across broad geographical gradients. Furthermore, we found that ecosystem‐level carbon stocks (average 401 ± 48 MgC/ha, covering biomass and the top 1 m of soil) varied little across diverse coastal morphologies, reflecting regional bottom‐up geomorphic controls that shape global patterns in mangrove biomass apportioning. Main conclusions Our findings reconcile views of wetland and terrestrial forest macroecology. Similarities in stand structural complexity and cross‐site size–density relationships across multiscale environmental gradients show that resource allocation in mangrove ecosystems is independent of tree size and invariant to species composition or latitude. Mangroves follow a universal fractal‐based scaling relationship that describes biomass allocation for several other terrestrial tree‐dominated communities. Understanding how mangroves adhere to these universal allometric rules can improve our ability to account for biomass apportioning and carbon stocks in response to broad geographical gradients.

Despite the global focus on the COVID-19 pandemic, the promise of impact to tropical coastlines and stochasticity of destruction caused by tropical cyclones remains unaltered, forcing human societies to adapt to new unadaptable scenarios. Super Cyclone Amphan’s landfall—the third cyclone of the season within the world’s largest mangrove forest—brought a new uncertainty to this undeveloped region of South Asia. How do vulnerable people deal with multiple disasters that limit necessary humanitarian response while still maintaining the natural environmental integrity of a system harboring critical wildlife populations and protecting people from further disaster? We explored this reality for the Sundarbans region using a remote sensing technique and found that the western part of Sundarbans mangroves was severely damaged by Amphan, suggesting that rapid remote sensing techniques can help direct resources, and recognize the eventuality that response will be a best effort for now. If 2020 is a window, multiple disaster management scenarios may become more common in the future. Yet, society’s obligation for maintaining environmental integrity remains unchanged.

The Tonle Sap Lake and Floodplain (TSLF) supports many globally threatened species and its fishery has sustained Cambodia’s people for millennia. The rate of habitat loss has accelerated in recent years due to political and economic conditions, and a warming climate and El Nino events that created opportunities for people to burn scrubland at an elevated rate. Here, we use a point-based landcover assessment method to document the impacts of local-scale drivers, in particular agricultural intensification, on habitat trends between 1993 and 2018. The areal extent of scrubland and grassland in the TSLF declined from ~ 74% in 1993 to ~ 52% in 2018, as a result of intensification and expansion of rice cultivation. During that time period, grassland cover declined from ~ 3160 to ~ 519 km2, whilst between 2008 and 2018, scrubland cover declined from ~ 8660 to ~ 6776 km2. Habitat loss has had catastrophic implications for grassland-dependant species, such as Bengal Florican, and, we estimate that habitat changes in the TSLF may have caused carbon stocks to decline by 12% while fish productivity is also likely to have dropped, with significant implications for food security. To put this habitat loss in context, losses over the past 10 years have been nearly twice as large as published predictions of the amount likely to be lost between 2010 and 2040 due to hydropower. We suggest that the expansion and intensification of rice cultivation is the greatest current threat to habitats in the TSLF and deserves greater attention from policy makers and practitioners.

Mangrove forests are salt-tolerant intertidal vegetation in tropical and subtropical areas. Mangrove ecosystems provide commercial products, valuable fisheries, and aquaculture resources, protect and stabilize coastlines, and are important carbon sinks. However, they are threatened globally by human activities such as deforestation, pollution, and development causing fragmentation between the well-preserved, restored, and disturbed mangrove forests. Despite this, mangroves can adapt and strive well and are notable well associated with microbial diversity. Here, we investigate the diversity of microbes in different environmental settings using preferred reporting items for systematic and meta-analyses (PRISMA) analysis for publications from Scopus and the Web of Science databases. We report publications since 1987, and observed an exponential increase in publications beginning in the year 2000, which may be associated with the development of molecular and sequencing technologies. Differences in bacterial diversity was observed across the well-preserved, restored, and disturbed mangrove environments. Disturbed mangrove forests had a higher diversity (70 unique taxon orders reported) compared to well-preserved (33 unique taxon orders reported) and restored forests (38 unique taxon orders reported). Based on our analysis, we found that the microbial community plays an important role in the survival and adaptability of mangroves under varying environmental conditions. Thus, there is a need and a lot of potential for research in the area of mangrove microbiology with reference to ecology, biogeochemistry, and geomorphology.

Mangroves provide several ecosystem services but suffer from multi-source degradation. Their global mapping at fine-scale needs efficient classification fusing very high resolution (VHR) satellite imageries. Visible (VIS) and near-infrared (NIR) imageries are great assets for mapping when supervised by machine learners. However those imageries commonly rely on three VIS and one NIR bands, impeding successful discrimination of diverse objects. The mangrove classification is besides largely supported by shallow learners. This research produced the first object-based mangrove classification using the VHR superspectral (16-band) WorldView-3 imagery supervised by convolutional neural networks. Four spectral datasets were segmented and classified using a U-net architecture: red-green-blue (RGB); RGB with yellow and coastal (VIS); VIS with red edge, NIR1 and NIR2 (VIS-NIR); and VIS-NIR with eight mid-infrareds (VIS-NIR-MIR). Even if very satisfactory results were computed for the four segmented datasets (averagely ranging from 0.92 to 0.96), the best model was derived from the 16-band full dataset.

The present study aimed to identify the nutritional and antioxidant potential of mangrove fruits of Xylocarpus granatum, Sonneratia alba, and Bruguiera gymnorrhiza growing in Rawa Aopa Watumohai Na...

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Several ecological and biogeochemical processes in mangroves are influenced by crab activities through bioturbation, leaf litter consumption, or fecal deposition. Bioturbation might be influenced by crab burrow dynamics or surrounding abiotic and biotic factors or both. Therefore, it is necessary to examine burrow dynamics under different abiotic and biotic conditions. This study was conducted in the estuarine mangroves of Fukido River in the northern part of Ishigaki Island, Japan. Two transects consisting of five and seven 14-m diameter circular plots were established perpendicular to the mangrove/ocean interface. Spatial and seasonal burrow dynamics data were collected from five randomly chosen quadrates within each plot. Burrow density, renewed burrows per day, and collapsed burrows per day significantly varied spatially and seasonally. Burrow density strongly depended on sediment bulk density. Numbers of renewed and collapsed burrows per day were the same (R2 = 0.86) though they significantly differed among the four seasons with being lowest in the winter season. This suggests that temperature, precipitation and crabs occurrence might control seasonal burrow dynamics. Proportion of collapsed burrows were strongly and significantly correlated to sediment bulk density, salinity and sediment temperature, which suggests that sediment properties provide structural support for burrows maintenance. On the other hand, vegetation cover and sediment characteristics influence the proportion of renewed burrows. Burrow depth was significantly controlled by sediment particle size, which suggests that crabs do not create deeper burrow if sediments contain higher amount of coarse sand. Entrance diameter was correlated to percentage organic matter, salinity, fine sand and distance from the river that means seaward sites are occupied by smaller and shallow burrows. Our results suggest that the burrow dynamics depend on abiotic and biotic factors and are useful for understanding spatial and seasonal variations for estimating bioturbation effects on mangroves biogeochemical cycle.

Mangrove is classified as an important ecosystem along the shorelines of tropical and subtropical landmasses, which are being degraded at an alarming rate despite numerous international treaties having been agreed. Iskandar Malaysia (IM) is a fast-growing economic region in southern Peninsular Malaysia, where three Ramsar Sites are located. Since the beginning of the 21st century (2000–2019), a total loss of 2907.29 ha of mangrove area has been estimated based on medium-high resolution remote sensing data. This corresponds to an annual loss rate of 1.12%, which is higher than the world mangrove depletion rate. The causes of mangrove loss were identified as land conversion to urban, plantations, and aquaculture activities, where large mangrove areas were shattered into many smaller patches. Fragmentation analysis over the mangrove area shows a reduction in the mean patch size (from 105 ha to 27 ha) and an increase in the number of mangrove patches (130 to 402), edge, and shape complexity, where smaller and isolated mangrove patches were found to be related to the rapid development of IM region. The Moderate Resolution Imaging Spectro-radiometer (MODIS) Leaf Area Index (LAI) and Gross Primary Productivity (GPP) products were used to inspect the impact of fragmentation on the mangrove ecosystem process. The mean LAI and GPP of mangrove areas that had not undergone any land cover changes over the years showed an increase from 3.03 to 3.55 (LAI) and 5.81 g C m−2 to 6.73 g C m−2 (GPP), highlighting the ability of the mangrove forest to assimilate CO2 when it is not disturbed. Similarly, GPP also increased over the gained areas (from 1.88 g C m−2 to 2.78 g C m−2). Meanwhile, areas that lost mangroves, but replaced them with oil palm, had decreased mean LAI from 2.99 to 2.62. In fragmented mangrove patches an increase in GPP was recorded, and this could be due to the smaller patches (< 9 ha) and their edge effects where abundance of solar radiation along the edges of the patches may increase productivity. The impact on GPP due to fragmentation is found to rely on the type of land transformation and patch characteristics (size, edge, and shape complexity). The preservation of mangrove forests in a rapidly developing region such as IM is vital to ensure ecosystem, ecology, environment, and biodiversity conservation, in addition to providing economical revenue and supporting human activities.

The efficiency of carbon (C) sequestration and its long-term storage by the mangroves and other shallow coastal habitats (like seagrass, tidal marsh, macroalgae) has been well recognized in mitigating climate change. Sediment is the largest reservoir of this sequestered C, also known as “blue C.” Blue C can be exported from sediment to the coastal water as dissolved or particulate form, or degraded to CO2 and release in the atmosphere, or it can be buried within the sediment for centuries to millennia. Other than discussing sedimentary C exchange processes in mangroves, we also reviewed current global database of blue C and identified South Asian countries as poor inventory despite a significant coverage (6.5%) and presence of world's largest deltaic mangrove, the Sundarbans (~10,000 km2). From data synthesis, blue C stock in South Asian mangroves is overall low compared to the neighboring South East (SE) Asian mangroves, that is due to less C% in sediment, low forest productivity, and nutrient limitation in the sediment. Application of stable isotopes, molecular biomarkers have been discussed to delineate sources of organic carbon (OC) in the sediment. Potential algal sources are recognized to contribute to sedimentary OC in southeastern India and Bangladesh mangroves, that could also explain their low C%, contrast to C-rich SE Asian mangroves where OC is largely of terrigenous origin. In the present discussion, C budget for the Indian Sundarbans has been revisited, that still warrants further investigations on biogeochemical sink processes (some aspects like benthic faunal production, fine root production, lithogenous or biogenous carbonate production, night-time benthic respiration). Lastly, we discussed on various aspects of blue C research to be undertaken in these mangrove ecosystems in future to fill the current gaps and challenges to develop better policies and how blue C research would help in conserving South Asian mangroves.

The launch of Roadmap towards Zero Single-use Plastics in 2018 demands baseline data on the management of marine debris in Malaysia. In 2021, Malaysia is placed 28th top plastic polluter in the world with plastic consumption at 56 kg/capita/year, therefore data on mismanaged plastic is imperative. This paper reviews the abundance and distribution of marine debris in selected Malaysian beaches over the last decade (2010–2020) and discusses issue on its management. Plastic debris on beaches in Malaysia, was reported to range from 64 items/m2, to as high as 1930 items/m2, contributing 30–45% of total waste collected. Plastics film was the most dominant, mainly originated from packaging materials. Therefore, appropriate action including improved marine waste management system is crucial to tackle the problem, together with effective governance mechanisms. Various suggestions were proposed based on the statistical-environmental data to reduce the occurrence of marine debris in the country.

Background and Objectives: In northern Vietnam, nearly 37,100 hectares of mangroves were lost from 1964&ndash, 1997 due to unsustainable harvest and deforestation for the creation of shrimp aquaculture ponds. To offset these losses, efforts in the late 1990s have resulted in thousands of hectares of mangroves being restored, but few studies to date have examined how effective these efforts are at creating restored mangrove forests that function similarly to the intact mangroves they are intended to replace. Materials and Methods: We quantified and compared soil carbon (C) stocks among restored (mono and mixed species) and intact mangrove forests in the provinces of Quang Ninh, Thai Binh, Nam Dinh and Thanh Hoa in northern Vietnam. A total of 96 soil cores up to a depth of 200 cm were collected every 25 m (25, 50, 75, 100, 125, and 150 m) along 16 linear transects that were 150 m long and perpendicular to the mangrove upland interface (six cores along each transect) at Quang Ninh (four transects), Thai Binh (five), Nam Dinh (four) and Thanh Hoa (three). Five-cm-long soil samples were then collected from the 0&ndash, 15 cm, 15&ndash, 30 cm, 30&ndash, 50 cm, 50&ndash, 100 cm, and &gt, 100 cm depth intervals of each soil core. Results: The study confirmed that the soil C stock of 20&ndash, 25-year-old restored mangrove forest (217.74 &plusmn, 16.82 Mg/ha) was not significantly different from that of intact mangrove forest (300.68 &plusmn, 51.61 Mg/ha) (p &gt, 0.05). Soil C stocks of Quang Ninh (323.89 &plusmn, 28.43 Mg/ha) were not significantly different from Nam Dinh (249.81 &plusmn, 19.09 Mg/ha), but both of those were significantly larger than Thai Binh (201.42 &plusmn, 27.65 Mg/ha) and Thanh Hoa (178.98 &plusmn, 30.82 Mg/ha) (p &lt, 0.05). Soil C stock differences among provinces could be due to their different geomorphological characteristics and mangrove age. Soil C stocks did not differ among mangroves that were restored with mixed mangrove species (289.75 &plusmn, 33.28 Mg/ha), Sonneratia caseolaris (L.) Engl. (255.67 &plusmn, 13.11 Mg/ha) or Aegiceras corniculatum (L.) Blanco (278.15 &plusmn, 43.86 Mg/ha), but soil C stocks of those mangroves were significantly greater than that of Kandelia obovata Sheue, Liu &amp, Yong (174.04 &plusmn, 20.38 Mg/ha) (p &lt, 0.05). Conclusion: There were significant differences in the soil C stocks of mangrove forests among species and provinces in northern Vietnam. The soil C stock of 20&ndash, 25-year-old restored mangrove forest was not significantly different from that of intact mangrove forest.

Mangrove forest conservation can help reduce global C emissions. Despite this benefit to climate change mitigation and adaptation, mangrove forests are being deforested or degraded at an alarming rate, though restoration efforts may offset these losses. The impacts of deforestation to C stocks are relatively intuitive and result in significant decreases in C stocks. It remains unclear how degradation from selective harvesting of trees affects C stocks or how effective restoration efforts are at restoring C stocks. Furthermore, total ecosystem C (TEC) stocks of pristine mangroves can significantly vary spatially. To address these issues, we conducted an intensive, national assessment of mangrove forests across Cambodia using a grid approach to: 1) examine how land use land cover (i.e., pristine, deforested, degraded, and restored forests) impacts TEC stocks, and 2) how TEC stocks vary spatially across the country. TEC stocks from deforested mangroves were always lower than pristine forests, resulting in an overall loss of 60% C (480 Mg C ha−1). However, TEC stocks from degraded and 25-year-old restored mangroves forests did not differ from pristine forests. Mean TEC in mangroves was 784.7 ± 30.1 Mg C ha−1, decreasing from 957.2 ± 32.8 Mg C ha−1 in the northern region to 628.9 ± 33.1 Mg C ha−1 in the central region to 386.2 ± 19.1 Mg C ha−1 in the southern region of Cambodia. Intensive sampling in mangroves across Cambodia verified impacts of deforestation reported elsewhere, revealed the lack of degradation impacts on TEC stocks, and demonstrated the effectiveness of restoration on TEC stocks after only 25 years. Our gridded sampling approach was able to capture spatial variability across Cambodia and provide a more realistic TEC stock information that can be used for national reporting or participation in C markets.

This study aims to establish allometric models and estimate aboveground biomass (AGB) of mangroves Rhizophoraceae in the Southeast Sulawesi, Indonesia. Allometric models of the AGB of mangroves Rhi...

This study aimed to determine the role of mangroves as a biofilter of heavy metals. The concentrations of heavy metals, namely copper, mercury, cadmium, zinc, and lead, in the mangroves Rhizophora apiculata, Ceriops tagal, Bruguiera gymnorrhiza, Lumnitzera racemosa, Xylocarpus granatum, Sonneratia alba, and Bruguiera parviflora at RAWN Park were determined using a Flame atomic absorption spectrophotometer. High concentrations of Cu (83.85μgg-1) and Hg (0.52μgg-1) were found in the tissues of L. racemosa, while high concentrations of Cd (10.81μgg-1), Zn (70.41μgg-1), and Pb (1.36μgg-1) were found in the tissues of B. gymnorrhiza, B. parviflora and C. tagal, respectively. The translocation and bioaccumulation factors of heavy metals by mangroves showed a variety of trends, which indicated the different partitioning and uptake capability of heavy metals in the tissues of various mangrove species. Thus, maintaining high diversity of mangroves is crucial to ensure the health and productivity of coastal zones.

The Philippines has lost nearly 70% of its natural mangrove cover since the early 1900s. As a result, large investments have been made to restore mangrove forests and the many ecosystem services that they provide. Most of these restoration efforts have been through outplanting of Rhizophora sp. seedlings, many of which have failed because the proper hydrological and ecological conditions were not properly assessed. Other afforestation projects involved planting seedlings in inappropriate places (e.g., seagrass beds, mudflats) that resulted in replacing one valuable ecosystem with another. The aim of this research was to investigate the growth of 3-, 9-, and 21-year-old afforested stands of Rhizophora spp. mangrove forest. We also investigated the impact of these plantations on local seagrass beds. The total aboveground biomass was 42.6, 74.4, and 111.7 Mg ha−1 for the 3-, 9-, and 21-year-old mangrove stands, respectively. Seagrass bed cover decreased under the closed canopy of the mangrove due to reduced photosynthetically active radiation and competition for growing space. This study shows that mangroves can grow to some extent on seagrass beds, though mangrove planting in these areas could eventually lead to seagrass loss. Thus, mangroves should not be planted in areas that are naturally occupied by other ecologically important ecosystems. The purpose of mangrove restoration should be clear and efforts should be focused on formerly deforested or degraded areas. Additional studies are needed from different locations to understand how mangrove planting in seagrass beds impacts growth performance and ecological functions of the latter ecosystem.

Species composition and productivity of mangrove forest at Okukubi River, Okinawa Island, Japan, were examined during a period from February 2010 to January 2013. Species composition, above and below-ground biomass changes, and litterfall production were measured. Bruguieragymnorrhiza has maintained its dominance (93.1%, relative dominance) of the stand. Mean mortality of trees was 16.4%, due to frequent attack of typhoons creating tree fall and hitting of other trees. The total above and below-ground biomass of the stand was 162.7 and 125.1 Mg ha − 1 , respectively. Among the total aboveground biomass of the trees, 7.2% was allocated to leaf, 69.2% to stem, and 10.1% to branch. In case of species wise contribution of biomass allocation, B . gymnorrhiza showed the highest score and R . stylosa the lowest. Mean annual litterfall was 11.8 Mg ha − 1 yr − 1 , with the maximum litterfall in summer and minimum in winter. The mean aboveground biomass increment and aboveground net primary productivity was 8.5 and 28.6 Mg ha − 1 yr − 1 , respectively. Total net primary productivity was estimated to be 42.5 Mg ha − 1 yr − 1 . This study revealed that mangrove forest with similar height and diameter produced different biomass production with different basal area. In the present study, the root biomass was large and the mean ratio of above/belowground biomass was estimated to be 1.3. It is emphasized that mangrove forests growing at the northern limit of their biogeographical distribution showed high biomass and net primary production indicating its ecological significance.

We aimed to investigate and compare the reproductive phenology of Bruguiera gymnorrhiza, Kandelia obovata, and Rhizophora stylosa in subtropical area, over 5 years. The three mangrove species of the Rhizophorace family yielded reproductive organs throughout the entire annual cycle, with the exception of K. obovata. In case of B. gymnorrhiza, flowers were observed throughout the year, with a massive production in September, whereas propagule production was highest in July. Reproductive organs of K. obovata followed a very specific monthly periodicity. The highest production of flowers, fruits were observed in July, and massive production of propagule was observed in September for R. stylosa. The highest number of flowers was recorded in R. stylosa followed by K. obovata and B. gymnorrhiza. However, propagule setting was lowest in R. stylosa as compared to other two species. The largest propagule was also observed in R. stylosa. This was significantly different from that of other two species. Multip...

Friess et al. discuss the results of conservation efforts for mangrove forests in recent years., SCOPUS: le.j, info:eu-repo/semantics/published

Mangrove forests play an important role in climate change adaptation and mitigation by maintaining coastline elevations relative to sea level rise, protecting coastal infrastructure from storm damage, and storing substantial quantities of carbon (C) in live and detrital pools. Determining the efficacy of mangroves in achieving climate goals can be complicated by difficulty in quantifying C inputs (i.e., differentiating newer inputs from younger trees from older residual C pools), and mitigation assessments rarely consider potential offsets to CO2 storage by methane (CH4 ) production in mangrove sediments. The establishment of non-native Rhizophora mangle along Hawaiian coastlines over the last century offers an opportunity to examine the role mangroves play in climate mitigation and adaptation both globally and locally as novel ecosystems. We quantified total ecosystem C storage, sedimentation, accretion, sediment organic C burial and CH4 emissions from ~70 year old R. mangle stands and adjacent uninvaded mudflats. Ecosystem C stocks of mangrove stands exceeded mudflats by 434 ± 33 Mg C/ha, and mangrove establishment increased average coastal accretion by 460%. Sediment organic C burial increased 10-fold (to 4.5 Mg C ha-1 year-1 ), double the global mean for old growth mangrove forests, suggesting that C accumulation from younger trees may occur faster than previously thought, with implications for mangrove restoration. Simulations indicate that increased CH4 emissions from sediments offset ecosystem CO2 storage by only 2%-4%, equivalent to 30-60 Mg CO2 -eq/ha over mangrove lifetime (100 year sustained global warming potential). Results highlight the importance of mangroves as novel systems that can rapidly accumulate C, have a net positive atmospheric greenhouse gas removal effect, and support shoreline accretion rates that outpace current sea level rise. Sequestration potential of novel mangrove forests should be taken into account when considering their removal or management, especially in the context of climate mitigation goals.

International audience; Currently there is limited information to estimate accurate and reliable mangrove forest area in Cambodia. Previous estimates did not explicitly illustrate the spatial distribution of mangrove for the entire country however , according to Global Forest Resource Assessment 2010, Cambodia's mangrove area cover in 1990 and 2010 was calculated at 79,638 ha and 55,704 ha, respectively using extrapolation of 1992-1996 (original data from Remote Sensing of forest cover 1992/93 and 1996/97) for 1990 and extrapolation of 1996-2002 (original data from Remote Sensing of forest cover 1996/97 and 2002) for 2010. This study mapped the spatial distribution of Cambodia's mangrove forest derived from 30 m x 30 m spatial resolution and polygon spatial extent from Landsat 8 (L8) image. Publicly available Landsat data was acquired from Google Earth Engine (GEE) Explorer including the Landsat Surface Reflectance-Landsat 8 (L8) OLI/TIRS; Top-Of-Atmosphere (TOA) L8 32-Day Reflectance Composite; Landsat Archive Pre-Collection from US Geological Survey (USGS, 2015); VHR Google-derived images (Collin et al. 2014) and field data collection from 63 plots representing the entire Cambodia of Surface Water Ambient Monitoring Program (SWAMP) to create a Google Fusion Table aiming at mapping the spatial resolution and extent. Random Forest (RF) Classifier, a supervised classification technique, was applied to three L8 images Archive Pre-Collection Level-1 (L8 OLI/TIRS) collected in December 2014, February 2015 and April 2015. Statistical analysis indicates the total area of mangrove forest cover reached 73,240ha with overall classification accuracy of 98.2%, 97.9% and 99.5% for three periods and the validation overall accuracy were 91.5%, 89.1% and 97.6%, respectively. Our findings suggest that L8 imagery and Google Earth Engine algorithm can be used to estimate area changes of mangrove forests in Cambodia with higher accuracy. The results of this study may be useful to assist decision making in planning for mangrove ecosystem restoration activities, evaluation of ecological services and in better estimation of carbon stock in mangrove forest. (Tier 1-default emission or Tier 3-plot data are more related to emission factor).

Regeneration of mangroves that occurred within Straits of Malacca over the last 35 years offers an excellent model system to examine how stand dynamics change over time. With exact stand age known, assessment of forest structure, biodiversity and biomass along a natural mangrove development chronosequence provides valuable information to define how long it takes mangrove restoration to return to a natural baseline condition. In natural settings, it is hypothesized that forest structure, diversity and biomass increase with stand age and that these are highest and most complex in intact mangroves. Thus, the study analyzed dynamics in species composition, forest structure and biomass across intact as well as naturally regenerated (NR) stands from 3, 6, 12, 18, and 25 years of age. Intact mangrove stands were structurally more complex and more diverse than younger stands. The preponderance of A. marina regeneration that appear for succession gives rise to a high importance value in the study area. The mean for above-ground and below-ground biomass was 71.00 ± 2.30 and 36.07 ± 0.52 Mg ha−1, respectively. Mean individual tree mass to tree density relationship resembles the mean tree weight–density trajectory of self-thinning even-aged plant populations where mean individual tree mass increased with decreasing density. Naturally regenerated mangroves supported higher tree diversity with complex in stand structure compared to restored mangroves, which were basically comprised of Rhizophora species. Restored mangroves attain higher biomass in a shorter period of time compared to naturally regenerated mangroves. Mangrove restoration should focus on naturally regenerated mangroves in order to increase carbon sequestration and thus provide climate change mitigation. Ecosystem services, biodiversity and climate change mitigation values need to be considered for both mangrove types as restored mangroves lower tree diversity compared to naturally regenerated mangroves of the same age stand. Therefore it is suggested that sustainable management such as silviculture method might be suitable for naturally regenerated mangroves to absorb more carbon from atmosphere and maintain the higher diversity.

Mangroves aboveground biomass (ABG) estimation at a large scale is a crucial to understand their role in mitigating climate change. The large-scale estimation of AGB is generally conducted with remote sensing techniques using stand characteristics such as canopy height and species composition. In the present study, we employed Lorey's mean canopy height (Hm) and basal area weighted mean wood density (ρm) to develop models for estimating AGB of mangroves in Asian regions such as Indonesia, Philippines and Japan, considering its application toward large-scale AGB estimation covering different climatic zones of subtropical zone in the Eastern Asia and tropical zone in the Southeastern Asia. The best power function model for AGB estimation with Hm as a single explanatory variable was selected based on AIC ranks. The Hm – AGB relationship model varied significantly among study sites. We successfully developed common allometric model to estimate AGB for closed-canopy mangroves in the Asian regions. The common allometric model of the Hm – AGB relationship tended to show underestimation for old growth mangroves having AGB > ca. 400 Mg ha−1. The common allometric model showed a similar trend with a previously developed model for mangroves in Bangladesh. On the other hand, the common allometric model for mangroves showed distinct difference from the model for terrestrial tropical forests, i.e. the range of Hm was narrower in mangroves than in terrestrial tropical forests, and AGB was quite higher in mangroves than in terrestrial tropical forests at a same range of Hm. The difference of AGB specific to Hm was explained by higher ρm and cumulative basal area (BA) in mangroves than that in terrestrial tropical forests. In particular, mangrove showed quite high BA in a comparison with terrestrial tropical forests. This study confirmed that developing mangrove specific biomass model is important since mangroves showed its unique characteristics through comparisons with terrestrial tropical forests, and limitations of the use of Hm as a single variable. It should be noted that old growth mangrove AGB is underestimated with the developed common allometric models. For old growth mangroves, carbon stock should be fairly evaluated with more accurate models otherwise their contribution to blue carbon would be overlooked, which could lead insufficient efforts for conservation of old growth mangroves. Further accurate models for estimating mangrove AGB at large scale are urgently required.

The mangroves are among the most at-risk coastal ecosystems, which are especially vulnerable to sea-level rise. This study aimed to know the growth capacity and biochemical defense of mangrove seedlings of Rhizophora mucronata under different sea water logging at experimental condition in Kendari bay, Southeast Sulawesi, Indonesia. Results showed that maximum leaf area, intrinsic rate increase of leaf area and relative growth rate (RGR) of height of the R. mucronata seedlings were significantly higher at treatment of 45 cm from the ground than other treatments, whereas RGR of diameter was the higher at treatment of 30 cm from the ground. Meanwhile, half expansion period leaf area was almost similar for all treatment. However, the carbon and nitrogen ratio in leaves of R. mucronata seedlings was significantly higher at seawater logging of 0 cm from the ground. The flavonoid and vitamin C concentrations in R. mucronata seedlings were higher at higher level inundation indicating protective role of these compounds under seawater logging stress.