Climate Change Impacts on the Ecosystem Functions and Services of Mangrove Forests

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Ecology and Management".

Deadline for manuscript submissions: closed (1 March 2020) | Viewed by 50842

Special Issue Editors


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Guest Editor
Biodiversity Research Centre, Academia Sinica, Nankang, Taipei 11529, Taiwan
Interests: forest ecosystem; soil biochemistry; microbiology and biogeochemistry
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Department of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan
Interests: system ecology; wetland ecology; marine ecology; estuarine

Special Issue Information

Dear Colleagues,

Mangroves are both economically and ecologically important, covering 70% of the tropical and subtropical sheltered coastlines. They provide many critical ecological functions and ecosystem services, including coastal protection, habitat provision, biodiversity support, food security, tourism and recreation. Recent scientific advances have showed that mangrove forests represent important carbon sinks and are able to serve as the natural solution to global greenhouse effects and contribute mitigation effort to climate change. However, mangroves have been extensively eliminated by human-induced habitat destruction and deforestation, inland hydrological alteration, and pollution in recent decades. If such exploitation of mangroves is uncontrolled, it will result in rapid decrease in abundance and diversity of mangroves and subsequently leading to permanent loss in biodiversity and many ecosystem services. Moreover, mangrove ecosystems are continuously affected by the catastrophic climate changes, such as rise in sea levels, temperature and atmospheric CO2 concentrations. Clearly, there is a pressing need for effective conservation, restoration and management of mangrove ecosystems for the battle against climate change and the sustainable future of nature and humans. The patterns and processes, and mechanisms of how mangrove ecosystem structures, functions and services respond to climate changes and various human impacts need to be better understood to enable the precise prediction of changes in ecological functions and ecosystems services of mangroves in the future. We encourage studies from all fields, including experimental studies, monitoring approaches and models, to contribute to this Special Issue in order to promote knowledge and adaptation strategies for the preservation, management, and future development of mangrove forest ecosystems.

Prof. Dr. Chih-Yu Chiu
Prof. Dr. Hsing-Juh Lin
Guest Editors

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Keywords

  • Climatic changes
  • Disturbances
  • Ecological impacts
  • Carbon sequestration
  • Biodiversity
  • Microbiology
  • Biogeochemistry
  • Ecosystem services
  • Conservation, restoration and management

Published Papers (10 papers)

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Research

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21 pages, 3501 KiB  
Article
Differential Response of Macrobenthic Abundance and Community Composition to Mangrove Vegetation
by Sin-He Pan, Chuan-Wen Ho, Chiao-Wen Lin, Shou-Chung Huang and Hsing-Juh Lin
Forests 2021, 12(10), 1403; https://doi.org/10.3390/f12101403 - 14 Oct 2021
Cited by 11 | Viewed by 2381
Abstract
The mass planting of mangroves has been proposed as a mitigation strategy to compensate for mangrove loss. However, the effects of mangrove vegetation on the abundance and community composition of macrobenthos remain controversial. The macrobenthic communities in four intact mangrove forests with different [...] Read more.
The mass planting of mangroves has been proposed as a mitigation strategy to compensate for mangrove loss. However, the effects of mangrove vegetation on the abundance and community composition of macrobenthos remain controversial. The macrobenthic communities in four intact mangrove forests with different conditions and the adjacent nonvegetated mudflats of two mangrove species with distinct stand structures on the western coast of Taiwan were examined. Some macrobenthic taxa occurred only in the mangroves, suggesting macrobenthic critical habitats. Seasonal shift in community composition was more pronounced in the mudflats than in the mangroves, possibly due to the rich food supply, low temperature, and shelter function provided by mangrove forests. However, crab density was always lower in the mangroves than in the mudflats. There was a negative relationship between the stem density of Kandelia obovata (S., L.) and infaunal density. The pneumatophore density of Avicennia marina (Forsk.) correlated negatively with epifaunal density. Our results show that the response of macrobenthic abundance and community composition to mangrove vegetation was inconsistent. We reason that mangroves are critical habitats for the macrobenthos in the mudflats. However, if mangrove tree density is high, we predict that the macrobenthic density will decrease. This suggests that at some intermediate level of mangrove tree density, where there are enough mangrove trees to harbor a macrobenthic community but not enough trees to significantly reduce this density, mangroves management can be optimally achieved to promote the presence of a diverse and dense macrobenthic community. Full article
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13 pages, 3670 KiB  
Article
Composition and Activity of N2-Fixing Microorganisms in Mangrove Forest Soils
by Yo-Jin Shiau, Yu-Te Lin, Rita S. W. Yam, Ed-Haun Chang, Jhe-Ming Wu, Tsu-Hsuan Hsu and Chih-Yu Chiu
Forests 2021, 12(7), 822; https://doi.org/10.3390/f12070822 - 22 Jun 2021
Cited by 6 | Viewed by 2137
Abstract
Mangrove forests are considered to be a highly productive ecosystem, but they are also generally nitrogen (N)-limited. Thus, soil N2 fixation can be important for the stability of both mangrove ecosystem functions and upland N supply. This study evaluates the N2 [...] Read more.
Mangrove forests are considered to be a highly productive ecosystem, but they are also generally nitrogen (N)-limited. Thus, soil N2 fixation can be important for the stability of both mangrove ecosystem functions and upland N supply. This study evaluates the N2 fixation activity and composition of relevant microorganisms in two coastal mangrove forests—the Guandu mangrove in an upstream estuary and the Bali mangrove in a downstream estuary—using the acetylene reduction method, real-time polymerase chain reaction, and next-generation sequencing. The results demonstrated that ambient nitrogenase activity was higher in downstream mangrove forests (13.2–15.6 nmol h−1 g−1 soil) than in upstream mangrove forests (0.2–1.4 nmol h−1 g−1 soil). However, both the maximum potential nitrogenase activity and nitrogenase gene (nifH gene) copy number were found to be higher in the upstream than in the downstream mangrove forests, implying that the nitrogenase activity and diazotrophic abundance may not necessarily be positively correlated. In addition, amended MoO4 (which inhibits the activity of sulfate-reducing bacteria in N2-fixation) yielded low nitrogenase activity, and sulfate-reducing bacteria made up 20–50% of the relative diazotrophic abundance in the mangrove forests, indicating that these bacteria might be the major active diazotrophs in this environment. Full article
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15 pages, 1974 KiB  
Article
Assessing Impacts of Metallic Contamination along the Tidal Gradient of a Riverine Mangrove: Multi-metal Bioaccumulation and Biomagnification of Filter-Feeding Bivalves
by Rita S. W. Yam, Yen-Tzu Fan, Zhehan Tan, Tzu-Dan Wang and Chiu-Yu Chiu
Forests 2020, 11(5), 504; https://doi.org/10.3390/f11050504 - 01 May 2020
Cited by 10 | Viewed by 2254
Abstract
Most riverine mangroves (characterized by salinity fluctuations and tidal inundations), are seriously threatened by metallic pollution. Whether differences in salinity and tidal effects along the river continuum can affect metallic bioaccumulation and the biomagnification of species is still unknown. Bivalves are representative sessile [...] Read more.
Most riverine mangroves (characterized by salinity fluctuations and tidal inundations), are seriously threatened by metallic pollution. Whether differences in salinity and tidal effects along the river continuum can affect metallic bioaccumulation and the biomagnification of species is still unknown. Bivalves are representative sessile inhabitants in mangrove ecosystems, with a high capacity to bioaccumulate metallic contaminants. The present study used two bivalves, Meretrix lusoria and Mytilopsis sallei, to monitor inter-site changes in metallic contamination and assess the associated ecological impacts along the tidal gradients of riverine mangroves. The concentrations of a total of six metals (Cr, Ni, Cu, Zn, Cd and Pb) in M. lusoria and M. sallei, collected at three different sites along Danshuei Riverine Mangrove, were investigated. The metallic concentrations of the whole soft body of the studied bivalves, and the associated surface sediment from each site, were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the inter-site effects on the bioaccumulation and biomagnification of metallic contaminants in bivalves. There are increasing concentrations of four metallic contaminants, Zn, Cr, Cd and Cu, in the seaward direction of the bivalves. The increasing mean metallic concentrations along the seaward direction may be the effect of salinity, further decreasing the rate of the elimination of these metals, thus resulting in a net increase in metallic contaminants. Our results clearly show prominent inter-site changes in the metallic burdens of bivalves in our study on riverine mangrove ecosystems associated with different levels of bioaccumulation and biomagnification of metallic contaminants. Thus, it is important to monitor multiple sites along the dynamic environment of riverine mangroves in order to gain a good understanding of the ecological impact of metallic pollution risks. The present findings provide important evidence of the use of simple indices to assess the ecological impacts of metallic pollution in riverine mangroves. Full article
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19 pages, 6386 KiB  
Article
Spatial Habitat Suitability Models of Mangroves with Kandelia obovata
by Shang-Shu Shih
Forests 2020, 11(4), 477; https://doi.org/10.3390/f11040477 - 23 Apr 2020
Cited by 16 | Viewed by 3494
Abstract
Mangrove forests provide important estuarine ecosystem services but are threatened by rising sea levels and anthropogenic impacts. Understanding the habitat characteristics required for mangrove growth is significant for mangrove restoration and integrated management. This study aims to build spatial habitat suitability index (HSI) [...] Read more.
Mangrove forests provide important estuarine ecosystem services but are threatened by rising sea levels and anthropogenic impacts. Understanding the habitat characteristics required for mangrove growth is significant for mangrove restoration and integrated management. This study aims to build spatial habitat suitability index (HSI) models for Kandelia obovata mangrove trees. Biological and habitat-related environmental data were collected in the Wazwei and Guandu wetlands in northern Taiwan. We adopted inundation frequency, soil sorting coefficient, and water salinity as the key environmental factors to build HSI models. The dependent variable of these environmental factors was the mangrove biomass per unit area. Significant differences were found for the mangrove biomass on different substrata and shore elevations. The tidal creek had the lowest elevation, and mangrove areas were found at the highest elevations. The oxidization level of the substrate under mangrove forests was high, indicating that the root system of mangroves could carry oxygen into the soil and result in oxidation. Human activities were found to lead to the reduced growth conditions of mangroves. The validation of the HSI model, considering the inundation frequency and soil sorting coefficient, proved to be reliable, with an accuracy ranging from 78% to 90%. A better simulation was found after revising the model by incorporating the factor of water salinity. The model forecast of the mangrove responses to the sea-level rise indicated an increase in the inundation frequency and thus an induced shift and shrinkage of the mangrove area. The increased HSI values of the bare mudflat area demonstrate an option for the potential restoration of mangrove trees. Given the findings of this study, we concluded that mangroves could spread from estuaries to upstream areas due to rising sea levels and might be limited by humanmade impacts. Restoring degraded floodplains is suggested for mangrove habitat rehabilitation. Full article
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16 pages, 2378 KiB  
Article
Methane Emissions from Subtropical and Tropical Mangrove Ecosystems in Taiwan
by Chiao-Wen Lin, Yu-Chen Kao, Meng-Chun Chou, Hsin-Hsun Wu, Chuan-Wen Ho and Hsing-Juh Lin
Forests 2020, 11(4), 470; https://doi.org/10.3390/f11040470 - 21 Apr 2020
Cited by 17 | Viewed by 4165
Abstract
Mangroves are one of the blue carbon ecosystems. However, greenhouse gas emissions from mangrove soils may reduce the capacity of carbon storage in these systems. In this study, methane (CH4) fluxes and soil properties of the top 10 cm layer were [...] Read more.
Mangroves are one of the blue carbon ecosystems. However, greenhouse gas emissions from mangrove soils may reduce the capacity of carbon storage in these systems. In this study, methane (CH4) fluxes and soil properties of the top 10 cm layer were determined in subtropical (Kandelia obovata) and tropical (Avicennia marina) mangrove ecosystems of Taiwan for a complete seasonal cycle. Our results demonstrate that CH4 emissions in mangroves cannot be neglected when constructing the carbon budgets and estimating the carbon storage capacity. CH4 fluxes were significantly higher in summer than in winter in the Avicennia mangroves. However, no seasonal variation in CH4 flux was observed in the Kandelia mangroves. CH4 fluxes were significantly higher in the mangrove soils of Avicennia than in the adjoining mudflats; this trend, however, was not necessarily recapitulated at Kandelia. The results of multiple regression analyses show that soil water and organic matter content were the main factors regulating the CH4 fluxes in the Kandelia mangroves. However, none of the soil parameters assessed show a significant influence on the CH4 fluxes in the Avicennia mangroves. Since pneumatophores can transport CH4 from anaerobic deep soils, this study suggests that the pneumatophores of Avicennia marina played a more important role than soil properties in affecting soil CH4 fluxes. Our results show that different mangrove tree species and related root structures may affect greenhouse gas emissions from the soils. Full article
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14 pages, 11752 KiB  
Article
Effects of Salt on Root Aeration, Nitrification, and Nitrogen Uptake in Mangroves
by Yan Zhao, Xun Wang, Youshao Wang, Zhaoyu Jiang, Xiaoyu Ma, Aniefiok Ini Inyang and Hao Cheng
Forests 2019, 10(12), 1131; https://doi.org/10.3390/f10121131 - 11 Dec 2019
Cited by 18 | Viewed by 3513
Abstract
The potential effects of salt on the growth, root anatomy, radial oxygen loss (ROL), and nitrogen (N) dynamics in mangroves were investigated using the seedlings of Avicennia marina (Forsk.) Vierh. The results showed that a moderate salinity (200 mM NaCl) appeared to have [...] Read more.
The potential effects of salt on the growth, root anatomy, radial oxygen loss (ROL), and nitrogen (N) dynamics in mangroves were investigated using the seedlings of Avicennia marina (Forsk.) Vierh. The results showed that a moderate salinity (200 mM NaCl) appeared to have little negative effect on the growth of A. marina. However, higher salt stresses (400 and 600 mM NaCl) significantly inhibited the biomass yield. Concentrations of N in the roots and leaves decreased sharply with increasing salinity. Nevertheless, the presence of salt directly altered root anatomy (e.g., reduced root porosity and promoted suberization within the exodermis and endodermis), leading to a significant reduction in ROL. The results further showed that reduced ROL induced by salt could restrain soil nitrification, resulting in less ammonia-oxidizing archaea and bacteria (AOA and AOB) gene copies and lower concentrations of NO3 in the soils. While increased root suberization induced by salt inhibited NH4+ and NO3 uptake and influx into the roots. In summary, this study indicated that inhibited root aeration may be a defense response to salt, however these root symptoms were not advantageous for rhizosphere nitrification and N uptake by A. marina. Full article
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19 pages, 2248 KiB  
Article
Propagule Dispersal Determines Mangrove Zonation at Intertidal and Estuarine Scales
by Wenqing Wang, Xiaofei Li and Mao Wang
Forests 2019, 10(3), 245; https://doi.org/10.3390/f10030245 - 10 Mar 2019
Cited by 39 | Viewed by 5481
Abstract
Propagule dispersal has generally been recognized as a vital factor affecting the spatial structure of tropical forest plants. However, available research shows that this hypothesis does not apply to mangrove species the propagules of which are dispersed by water. Due to the lack [...] Read more.
Propagule dispersal has generally been recognized as a vital factor affecting the spatial structure of tropical forest plants. However, available research shows that this hypothesis does not apply to mangrove species the propagules of which are dispersed by water. Due to the lack of comprehensive and quantitative information as well as the high spatio-temporal heterogeneity of the mangrove environment, the exact factors affecting the spatial structure of mangrove forests are poorly understood. To assess this, we selected a mangrove estuary with high mangrove species richness that experiences great changes in water salinity. After investigating the zonation of mature mangrove individuals across tides and the estuary, we measured the size and initial specific gravity of the propagules and then selected the eight most common species from which to observe the changes in specific gravity, buoyancy, and root initiation during dispersal at different sites with different water salinity regimes. The relationships among distribution patterns, propagule establishment, and dispersal behavior were investigated. We found that mangrove propagule dispersal is not a passively buoyant process controlled by water currents. During dispersal, mangrove propagules can actively adjust their specific gravity and root initiation. The dynamic specific gravity of the propagules was negatively related to propagule buoyancy and surface elevation. The differences in propagule specific gravity corroborated the distribution patterns of the species across the intertidal zone and estuary. Mangrove zonation on both the intertidal and estuarine scale can be explained by the tidal sorting hypothesis, as zonation is controlled by the tidal sorting of the propagules according to buoyancy and by the differential ability of the propagules to establish in the intertidal zones. The results add new understanding of observed mangrove species zonation and should inform conservation managers when restoring mangroves or evaluating the potential impacts of global change and anthropogenic disturbances that might alter the hydrology, including the water salinity regime. Full article
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Review

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12 pages, 1157 KiB  
Review
Dynamics of Methane in Mangrove Forest: Will It Worsen with Decreasing Mangrove Forests?
by Hironori Arai, Kazuyuki Inubushi and Chih-Yu Chiu
Forests 2021, 12(9), 1204; https://doi.org/10.3390/f12091204 - 05 Sep 2021
Cited by 7 | Viewed by 3907
Abstract
Mangrove forests sequester a significant amount of organic matter in their sediment and are recognized as an important carbon storage source (i.e., blue carbon, including in seagrass ecosystems and other coastal wetlands). The methane-producing archaea in anaerobic sediments releases methane, a greenhouse gas [...] Read more.
Mangrove forests sequester a significant amount of organic matter in their sediment and are recognized as an important carbon storage source (i.e., blue carbon, including in seagrass ecosystems and other coastal wetlands). The methane-producing archaea in anaerobic sediments releases methane, a greenhouse gas species. The contribution to total greenhouse gas emissions from mangrove ecosystems remains controversial. However, the intensity CH4 emissions from anaerobic mangrove sediment is known to be sensitive to environmental changes, and the sediment is exposed to oxygen by methanotrophic (CH4-oxidizing) bacteria as well as to anthropogenic impacts and climate change in mangrove forests. This review discusses the major factors decreasing the effect of mangroves on CH4 emissions from sediment, the significance of ecosystem protection regarding forest biomass and the hydrosphere/soil environment, and how to evaluate emission status geospatially. An innovative “digital-twin” system overcoming the difficulty of field observation is required for suggesting sustainable mitigation in mangrove ecosystems, such as a locally/regionally/globally heterogenous environment with various random factors. Full article
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15 pages, 1636 KiB  
Review
Biogeochemical Processes of C and N in the Soil of Mangrove Forest Ecosystems
by Yo-Jin Shiau and Chih-Yu Chiu
Forests 2020, 11(5), 492; https://doi.org/10.3390/f11050492 - 27 Apr 2020
Cited by 36 | Viewed by 8471
Abstract
The mangrove forest provides various ecosystem services in tropical and subtropical regions. Many of these services are driven by the biogeochemical cycles of C and N, and soil is the major reservoir for these chemical elements. These cycles may be influenced by the [...] Read more.
The mangrove forest provides various ecosystem services in tropical and subtropical regions. Many of these services are driven by the biogeochemical cycles of C and N, and soil is the major reservoir for these chemical elements. These cycles may be influenced by the changing climate. The high plant biomass in mangrove forests makes these forests an important sink for blue C storage. However, anaerobic soil conditions may also turn mangrove forests into an environmentally detrimental producer of greenhouse gases (such as CH4 and N2O), especially as air temperatures increase. In addition, the changing environmental factors associated with climate change may also influence the N cycles and change the patterns of N2 fixation, dissimilatory nitrate reduction to ammonium, and denitrification processes. This review summarizes the biogeochemical processes of C and N cycles in mangrove forest soils based on recently published studies, and how these processes may respond to climate change, with the aim of predicting the impacts of climate change on the mangrove forest ecosystem. Full article
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13 pages, 1031 KiB  
Review
Impact of Global Change on Nutrient Dynamics in Mangrove Forests
by Daniel M. Alongi
Forests 2018, 9(10), 596; https://doi.org/10.3390/f9100596 - 25 Sep 2018
Cited by 97 | Viewed by 13574
Abstract
The cycling of essential nutrients is central to mangrove productivity. A mass balance shows that mangroves rely on soil ammonification, nitrification, and dissimilatory reduction to ammonium for available nitrogen. Mangroves are often nutrient limited and show tight coupling between nutrient availability and tree [...] Read more.
The cycling of essential nutrients is central to mangrove productivity. A mass balance shows that mangroves rely on soil ammonification, nitrification, and dissimilatory reduction to ammonium for available nitrogen. Mangroves are often nutrient limited and show tight coupling between nutrient availability and tree photosynthesis. This relationship and, thus, forest productivity can be disrupted by various disturbances such as deforestation, changes in hydrology due to impoundments, land-use change, increasing frequency and intensity of storms, increasing temperatures, increasing atmospheric CO2 concentrations, and a rising sea-level. Deforestation and hydrological changes are the most devastating to soil nutrient-plant relations and mangrove productivity. Land-use changes can result in positive and negative impacts on mangroves and can also results in increasing frequency of storms and intensity of storms. Increasing temperatures and atmospheric CO2 levels have an initially enhanced effect on mangroves and microbial transformation rates of nitrogen and phosphorus. The effects of rising seas are complex and depend on the local rate of sea-level rise, the soil accretion rate, the subsidence or uplift rate, and the tidal position. If mangroves cannot keep pace with a sea-level rise, seaward mangroves will likely drown but landward mangroves will expand and show enhanced growth and more rapid nutrient cycling if space permits. Full article
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