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Structural equation model showing drivers of aboveground mangrove biomass in the lagoonal environment of Aldabra (model fitting parameters are Fisher's C = 0.87, P = 0.65, degrees of freedom = 2). Solid and dashed arrows represent significant (P < 0.05) and non-significant paths, respectively. Numbers adjacent to arrows are the standardized effect sizes of the relationship (Grace et al., 2012; unstandardized coefficients are given in Table A3). The coefficient of determination (R 2 ) value reports the total variation in a dependent variable (soil nutrient content, mangrove AGB) that is explained by the combined predictor variables (mangrove tree image from ian.umces.edu/symbols/).
Source publication
Lagoonal mangrove ecosystems are vital for carbon capture, protection of coastlines and conservation of biodiversity. Yet, they are decreasing globally at a higher rate than other mangrove ecosystems. In addition to human drivers, local environmental factors influence the functioning of lagoonal mangrove ecosystems, but their importance and combine...
Contexts in source publication
Context 1
... influence and the relative importance of local environmental drivers on mangrove AGB in a lagoonal ecosystem with structural equation models. Our SEM were supported for the lagoonal mangrove ecosystem since the covariate structure implied by the SEM did not differ from the covariance structure in the observed data (Fisher's C, df = 2, P > 0.05, Fig. 4). Soil nutrient content, water level variation, and soil salinity explained 82 % of the variation in mangrove AGB. Soil nutrient content was the most influential driver of mangrove AGB with a standardized coefficient of 0.80 (Table A3)-a change of 1 SD in the total soil nutrient content is estimated to result in a 0.80 SD change in ...
Context 2
... driver of mangrove AGB with a standardized coefficient of 0.80 (Table A3)-a change of 1 SD in the total soil nutrient content is estimated to result in a 0.80 SD change in mangrove AGB. Water level variation had a similar positive effect on mangrove AGB (0.58; standardized coefficient) through its positive effect on soil nutrient content (see Fig. 4). Specifically, higher variation in the water level promoted higher soil nutrient content, which positively influenced the AGB. The total soil nutrient content variation explained by the daily water level variation was 52 %. We did not observe an indirect effect of water level variation on mangrove AGB through soil salinity (path ...
Context 3
... coefficients for the structural equation model for mangrove above ground biomass (AGB) in the lagoonal ecosystem of Aldabra presented in Fig. 4. Standardized coefficients (scaled by standard deviations) of significant values (P < 0.05) are bolded. The path coefficients and their corresponding standard error, standard estimate and test statistic (critical value) are provided. ...
Citations
... Very limited studies have investigated the interrelation between soil nutrients and stand structure of mangrove forests. The soil nutrients, especially essential macronutrients, influence the variation of mangrove AGB (Constance et al. 2022). The AGB significantly correlates with soil phosphorus (r = 0.85, p < 0.01), and salinity (r = − 0.79, p < 0.05) (Boto and Wellington 1984). ...
Background
The mangrove ecosystem has the highest carbon sink potential which significantly contributes to bringing carbon neutrality. Understanding the carbon stock dynamics along the age of forest stands in the mangrove forest ecosystem is of significance for managing the forests and their carbon accumulation. This study aimed to estimate the forest structural attributes, biomass and total ecosystem carbon stock (TECS) of old natural (age > 50 years) and young planted (age ~ 20 years) mangrove forest stands at Bichitrapur Mangrove Reserve Forest in eastern coast of India. We also attempted to understand the interrelationship of structural attributes, biomass and soil properties in the mangrove forests. To achieve the results, twenty random plots were established (size: 20 m × 25 m) and suitable allometric equations along with species-specific wood density values were used to estimate the biomass and carbon stock.
Results
Altogether, 29 plant species (18 exclusive and 11 associate species) were recorded. The mean total biomass (± SE) and soil organic carbon (at 30 cm depth) were 165.31 ± 20.89 t ha ⁻¹ and 40.20 ± 1.24 t C ha ⁻¹ for young stands, and 586.12 ± 56.74 t ha ⁻¹ and 49.68 ± 2.39 t C ha ⁻¹ for old stands, respectively. Among mangrove species, Avicennia marina contributed the highest vegetation biomass in both forest stands (59.72 t ha ⁻¹ and 262.28 t ha ⁻¹ in young and old stands, respectively), followed by Avicennia officinalis (35.05 t ha ⁻¹ ) and Sonneratia apetala (26.09 t ha ⁻¹ ) in young stand and Avicennia alba (169.28 t ha ⁻¹ ) and Avicennia officinalis (115.58 t ha ⁻¹ ) in old stand. The mean TECS was 235.62 ± 27.34 t C ha ⁻¹ . The contribution of vegetation and soil to TECS was 63% and 37% in the young stand, whereas in the old stand it was 83% and 17%, respectively. The correlation analyses revealed that mean stand height ( r = 0.87), basal area ( r = 0.99), soil nitrogen ( r = 0.76), potassium ( r = 0.78), and carbon ( r = 0.80) were significantly positively correlated with total biomass at p < 0.01.
Conclusions
Our results demonstrate that old mangrove forest stands store substantially high carbon stock than young planted forest stands, implying the role of forest age in determining the carbon storage potential of mangrove ecosystems.
... Remote sensing techniques can effectively predict and map AGB values over large areas Zhu et al. 2015). Early approaches relied primarily on the combined use of optical and radar data to derive vegetation indices and structural information correlated with AGB estimation (Aslan et al. 2016;Constance et al. 2022;Jensen and Hodgson 1985;Liang et al. 2022;Oh et al. 1992;Rachkulik and Sitnikova 1976;Salunkhe et al. 2018;Treuhaft and Siqueira 2000;Zhu et al. 2020a, b). They are used to develop AGB prediction models by utilizing the relationships between fieldobserved AGB samples and multispectral bands and vegetation indices (VIs) of passive optical images or radar backscatter polarizations (Kovacs et al. 2013;Proisy et al. 2007). ...
Background
Integrating optical and LiDAR data is crucial for accurately predicting aboveground biomass (AGB) due to their complementarily essential characteristics. It can be anticipated that this integration approach needs to deal with an expanded set of variables and scale-related challenges. To achieve satisfactory accuracy in real-world applications , further exploration is needed to optimize AGB models by selecting appropriate scales and variables.
Methods
This study examined the impact of LiDAR point cloud-derived metrics on estimation accuracies at different scales, ranging from 2 to 16 m cell sizes. We integrated WorldView-2 imagery with LiDAR data to construct biomass models and developed a genetic algorithm-based wrapper for variable selection and parameter tuning in artificial neural networks (GA-ANN wrapper).
Results
Our findings indicated that the highest accuracies in estimating AGB were yielded by 4 m and 6 m cell sizes, followed by 8 m and 10 m, associated with the dimensions of vegetation canopies and sampling plots. Models integrating WorldView-2 and LiDAR data outperformed those using each data source individually, reducing RMSEr by 5.80% and 3.89%, respectively. Combining these data sources can capture the canopy spectral responses and vertical vegetation structure. The GA-ANN wrapper model decreased RMSEr by 1.69% over the ANN model and dwindled the number of variables from 38 to 9. The selected variables included vegetation density, height, species, and vegetation indices.
Conclusions
The appropriate cell size for AGB estimation should consider the sizes of vegetation canopies, tree densities, and sampling plots. The GA-ANN wrapper effectively reduced variables and achieved the highest accuracy. Additionally, canopy spectral and vertical structure information are vital for accurate AGB estimation. Our study offered insights into optimizing mangrove AGB models by integrating optical and LiDAR data. The approach, data, model, and indices employed in this research can effectively predict AGB estimates of any other forest types or vegetation cover types in different climate regions.
... Mangroves are well recognised as ecologically as well as economically important, dynamic coastal ecosystems, playing crucial roles in protecting the habitat from natural disasters through maintaining the productivity, health, carbon sequestration, and tolerance to various abiotic stresses (Akram et al., 2023). Recent research (Constance et al., 2022) has revealed that mangrove growth is frequently impeded by the scarcity of some essential macronutrients like phosphorus (P) and nitrogen (N). Through colonization, arbuscular mycorrhizal fungi (AMF) could fulfil such nutrient requirements in saline and poor-nutrient soils in mangrove ecosystem (Akaji et al., 2022). ...
Mangroves, despite thriving at the fringes of habitat tolerance in coastal regions, stand out as one of the world's most highly productive ecosystems. This study delves into the remarkable symbiotic relationship between mangroves and arbuscular mycorrhizal fungi (AMF). Specifically, it assesses seasonal diversity in six true mangrove species and four associated species, situated in Henry's Island, Bakkhali, India. Spore density and root colonization were examined across different seasons. The highest spore density was observed in Heritiera fomes (a timber-producing mangrove) during the post-monsoon season, followed by pre-monsoon and monsoon periods. Root colonization was notably prominent in Ceriops tagal (Indian mangrove), Bruguira gymnorrhiza (Oriental mangrove), and Sonneratia alba (flowering evergreen mangrove) during both pre-and post-monsoon seasons. This study unveiled a rich fungal diversity, with a total of 60 AMF species belonging to 13 genera. Among these, the genus Glomus emerged as the dominant group, with species such as G. deserticola along with another genus Rhizophagus intraradics displaying widespread distribution. Notably, Glomus consistently ranked as the most prevalent genus throughout the year, indicating its remarkable adaptability and strong dispersal capacity in both true and associate mangrove plant species. This research sheds light on the seasonal dynamics of AMF associations in mangrove ecosystems, emphasizing the significance of Glomus as a key player in this symbiotic relationship. These findings contribute to our understanding of the ecological intricacies within mangrove habitats and highlight the adaptability of certain AMF genera to varying environmental conditions.
... Shoreline substrate is categorised based on the physical properties of the shoreline material, ranging from hard rock to soft sediments. This plays a crucial role in root establishment (Arnaud et al., 2023) and nutrient availability (Constance et al., 2022). Shoreline stability, defined as the susceptibility of shoreline segments to erosion and accretion, based on historical trends, was selected as it directly impacts long-term habitat persistence and restoration sustainability (Cabaço et al., 2008;Evans et al., 2022;Xiao et al., 2020). ...
Blue carbon ecosystems (BCEs), such as mangroves, saltmarshes, and seagrasses, are important nature-based solutions for climate change mitigation and adaptation but are threatened by degradation. Effective BCE restoration requires strategic planning and site selection to optimise outcomes. We developed a Geographic Information System (GIS)-based multi-criteria decision support tool to identify suitable areas for BCE restoration along the 2512 km-long coastline of Victoria, Australia. High-resolution spatial data on BCE distribution, coastal geomorphology, hydrodynamics, and land tenure were integrated into a flexible spatial model that distinguishes between passive and active restoration suitability. The tool was applied to identify high-priority locations for mangrove, saltmarsh, and seagrass restoration across different scenarios. Results indicate substantial potential for BCE restoration in Victoria, with 33,253 ha of suitable area identified, mostly (>97%) on public land, which aligned with the selection criteria used in the tool. Restoration opportunities are concentrated in bays and estuaries where historical losses have been significant. The mapped outputs provide a decision-support framework for regional restoration planning, while the tool itself can be adapted to other geographies. By integrating multiple spatial criteria and distinguishing between passive and active restoration, our approach offers a new method for targeting BCE restoration and informing resource allocation. The identified restoration potential will also require collaboration with coastal managers and communities, and consideration of socioeconomic factors. With further refinements, such as incorporating multi-criteria decision analysis techniques, GIS-based tools can help catalyse strategic blue carbon investments and contribute to climate change mitigation and adaptation goals at different spatial scales. This study highlights the value of spatial identification for BCE restoration and provides a transferable framework for other regions.
... among different pools and compartments, such as soil, water, plants, and animals (Araújo et al., 2021;Constance et al., 2022;Hossain & Nuruddin, 2016;Wong et al., 1995). The mangrove ecosystem encompasses several crucial components: forest, soil, and marine (Hossain & Nuruddin, 2016). ...
Mangrove soil is crucial for maintaining the health and nutrient balance of coastal ecosystems. It often serves as the final sink for commercial, aquaculture, and agricultural contaminants. This necessitates developing and understanding precise insights into mangrove health and sustainability through tailor-made evaluation indices. Currently, there are few studies regarding the assessment of mangrove ecosystem sustainability. The Thai Binh Mangrove is the third-largest province in terms of mangrove coverage in northern Vietnam. This mangrove has not undergone a direct assessment of soil quality using ground-level data. Therefore, this study focuses on evaluating the current state of the Thai Binh Mangrove in Vietnam, identifying key factors contributing to its degradation. Soil samples were collected from 38 stations across the mangrove and analyzed for pH, heavy metals, and nutrients over two years, from 2022 to 2023. The mangrove soil quality is assessed using Principal Component Analysis (PCA) and Cluster Analysis (CA). The Pollution Load Index (PLI) is used to characterize soil pollution, and it ranges from 0.29 to 1.09. Additionally, the Ecological Risk Index (ERI) is used to assess the ecological impact of soil pollution, revealing that the area falls within the low-risk category. The study also proposes measures like aquaculture, ecotourism, and increased awareness and education regarding the sustainability of mangroves and soil quality. The study underscores the significance of international cooperation, treaties, and legislative reform in assisting decision-makers with sustainable mangrove management.
... For example giant tortoises play a major role in the terrestrial organic matter of Aldabra (Falcón and Hansen 2018). Constance et al. (2022) suggested that the spatial distribution of nutrients in mangrove soils in Aldabra's lagoon was due to macrofauna such as Aldabra giant tortoises. In general, mangroves lead to more depleted δ 13 C being incorporated into seagrasses (Bouillon et al., 2008), and mangroves dominate over half of Aldabra's lagoon coastline (Constance et al., 2022). ...
... Constance et al. (2022) suggested that the spatial distribution of nutrients in mangrove soils in Aldabra's lagoon was due to macrofauna such as Aldabra giant tortoises. In general, mangroves lead to more depleted δ 13 C being incorporated into seagrasses (Bouillon et al., 2008), and mangroves dominate over half of Aldabra's lagoon coastline (Constance et al., 2022). Furthermore, large seabird breeding colonies in the mangroves around the lagoon (Diamond 1974;Š úr et al., 2013) can C.L. Sanchez et al. contribute large amounts of bio-available nitrogen, phosphorous and trace elements into the surrounding ecosystems (De La Peña-Lastra 2021). ...
Using stable isotope analysis of carbon and nitrogen of turtle tissues and putative prey items, we investigated the diet of immature green turtles and hawksbill turtles foraging in the lagoon of Aldabra Atoll, a relatively undisturbed atoll in the southern Seychelles. Aldabra offers a unique environment for understanding sea turtle ecology. Green turtles mostly consumed seagrass and brown algae while hawksbill turtles mainly consumed mangroves and invertebrates. Green turtles showed a dietary shift with size (a proxy for age). There was minimal niche overlap between species and evidence of small-scale foraging site fidelity with turtle tissue reflecting site-specific prey. This highlights the ecological importance of seagrass and mangrove habitats and suggests that turtles play a role in controlling algal biomass at Aldabra. This study is the first to closely examine the foraging ecology of these sympatric turtle species in the Western Indian Ocean, a globally important region for both species.
... 7,46 Foliar N:P ratio in our study was 11.7 G 2.45 (mean G SD), suggesting mangroves in our study are N limited, which is typical for fringe mangroves influenced by frequent tidal flushing. 7,47 N limitation at our study site is further indicated by the equally low N:P ratios documented in previous analyses on mangrove soil 48 and lagoonal sediment porewater on Aldabra. 49 At our seabird sites, uptake of seabird-derived nutrients alleviated mangrove nutrient limitations of both N and P, observed by reductions in foliar C:N and C:P ratios of R. mucronata. ...
... Soil nutrient content is a main driver of mangrove aboveground biomass on Aldabra. 48 Therefore, by fertilizing mangroves where they nest, seabirds likely enhance mangrove productivity in their breeding areas, further promoting suitable nesting habitat, likely creating a positive-feedback loop for seabird populations. 10 Indeed, both mangroves and mangrove-nesting seabird populations on Aldabra have increased over the last few decades. ...
... 73,74 Furthermore, Aldabra's mangroves comprise one of Seychelles' largest blue carbon ecosystems. 48 By improving mangrove nutrient status and health, we show that seabirds nesting on Aldabra boost biodiversity and ecosystem services. ...
Eutrophication by human-derived nutrient enrichment is a major threat to mangroves, impacting productivity, ecological functions, resilience, and ecosystem services. Natural mangrove nutrient enrichment processes, however, remain largely uninvestigated. Mobile consumers such as seabirds are important vectors of cross-ecosystem nutrient subsidies to islands but how they influence mangrove ecosystems is poorly known. We assessed the contribution, uptake, cycling, and transfer of nutrients from seabird colonies in remote mangrove systems free of human stressors. We found that nutrients from seabird guano enrich mangrove plants, reduce nutrient limitations, enhance mangrove invertebrate food webs, and are exported to nearby coastal habitats through tidal flow. We show that seabird nutrient subsidies in mangroves can be substantial, improving the nutrient status and health of mangroves and adjacent coastal habitats. Conserving mobile consumers, such as seabirds, is therefore vital to preserve and enhance their role in mangrove productivity, resilience, and provision of diverse functions and services.
... Organic matter is essential for providing energy and materials to bacteria, plants, and animals. It also contains vitamins and substances that can either accelerate or slow the growth rate (Constance et al., 2022). ...
... Avicennia lanata exhibited higher growth rates than Rhizophora mucronata. Therefore, the frequency of inundation has a significant impact on mangrove growth (Constance et al., 2022). After monitoring the growth of mangroves in a rehabilitation area for six months, it was discovered that the height and diameter of mangroves were not significantly affected by water quality and organic matter content. ...
Mangroves participate in controlling climate change by acting as the lungs of the world through the absorption and storage of blue carbon. The high-standing water on the land that must be rehabilitated is one of the obstacles encountered, so a special strategy is needed, namely, implementing a mangrove rehabilitation media structure using the demplot mangrove method. This study aimed to analyze mangrove growth based on the application of mangrove rehabilitation media structures and to calculate potential carbon stocks based on the value of tree biomass from mangrove rehabilitation monitoring. In this study, tree height and diameter were measured and linked to the water quality and frequency of inundation. Mangrove carbon reserves were also calculated based on biomass values. Good growth in the height and diameter of mangroves occurred in Avicennia lanata stands with an inundation frequency of 6 h/day. The largest projection of potential carbon stocks from the results of monitoring mangrove rehabilitation was also stored in Avicennia lanata mangrove stands at 0.3467 kg/tree (60 months), 0.6287 kg/tree (120 months), and 0.9107 kg/tree (180 months).
... Due to the slightly acidic nature of these soils, seasonal and site-specific variations in K concentrations can have an impact on the diversity of bacteria in mangrove substrates (Behera et al. 2013). Certain regions that harbour vital nutrients, such as K, exhibit a greater abundance of mangroves with elevated aboveground biomass (Constance et al. 2022) (Table 1). Furthermore, with regard to the restoration of mangrove ecosystems that have been damaged, discrepancies in nutrient levels, including K, may have an impact on the organisms that are linked to these areas and impede the future recovery of mangroves over an extended period (Krishnapriya et al. 2023). ...
... Elevated levels of Mg, Ca, and S are positively correlated with increased above-ground biomass in mangrove ecosystems situated in lagoonal environments. During particular times of the year, research has shown that interior mangroves possess higher levels of S, Ca, and Mg, while riverine mangroves have lower values, suggesting elevated environmental stresses in mangroves found inland (Constance et al. 2022) ( Table 2). The composition and arrangement of vegetation from mangroves in secondary mangrove ecosystems, which are expected to remain mature forests, are primarily influenced by soil nutrients Mg and S. The amount of S and Mg in the continually growing biomass of trees was observed to increase with age in both the roots and leaves (Cooray et al. 2021). ...
Mangroves represent highly important coastal ecological systems on a global scale. Despite being highly examined ecosystems, the literature reveals several knowledge gaps regarding the impact of soil-water relationships in mangrove forests. This comprehensive literature review integrates extant studies on the impact of soil-water relationships within mangrove ecosystems at global and local levels, with the aim of identifying the factors that facilitate or impede their capacity to flourish productivity. Our findings demonstrate that various biogeochemical processes that take place in soil and water have an impact on the functioning and balance of mangrove ecosystems. These processes prompt mangroves to develop ecophysiological adaptations that enable them to mitigate the effects of harsh environmental stressors and changes, predominantly caused by anthropogenic activities. Alterations in both the physical and chemical properties of soil and water within mangrove ecosystems can have a direct impact on their distribution, density, and diversity. The review underscores the necessity of establishing appropriate policies and governance mechanisms for the protection and conservation of mangroves. The interplay between soil and water has a significant bearing on the functioning of mangrove ecosystems, with potential implications for productivity and functionality as anthropogenic and natural phenomena constantly alter their physicochemical properties.
... Mangrove restoration in some cases can counter these losses (UNEP, 2016). Anthropogenic protection and restoration have been proven to enhance the mangrove carbon sink (Azman et al., 2023;Ray et al., 2023) by increasing the mangrove biomass and fostering the carbon sequestration ability of mangrove forests (Constance et al., 2022). For instance, increasing mangrove area on the lower Texas coast over the past century has increased local carbon sequestration rate and potentially the overall carbon storage (Bianchi et al., 2013). ...
