Showing papers in "Wetlands Ecology and Management in 2015"
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TL;DR: In this paper, a ranking system for vulnerability assessment of mangrove systems integrating biotic and abiotic factors along with human management components, using validated methods previously developed for other research questions, was developed.
Abstract: Climate change, particularly its associated sea level rise, is major threat to mangrove coastal areas, and it is essential to develop ways to reduce vulnerability through strategic management planning. Vulnerability has three dimensions of exposure to stresses, associated sensitivity, and related adaptive capacity, and ways to measure components of each were trialled at sites in Africa and the South Pacific to develop an analysis procedure based on ranking. The approaches of the ranking system for vulnerability assessment of mangrove systems integrate biotic and abiotic factors along with human management components, using validated methods previously developed for other research questions. These include determining mangrove forest health, adjacent ecosystem resilience, the extent and effects of human impacts, and the environmental conditions of different mangrove settings. Results of the vulnerability assessment ranking using up to 20 measurements found all sites to have some components of vulnerability. Douala Estuary, Cameroon showed the highest vulnerability, owing to low tidal range, impacts from non-climate stressors, and evidence of moderate seaward edge retreat. Tikina Wai, Fiji showed inherent vulnerability owing to location on a subsiding coastline with a low tidal range, but this was offset by strong local community management capacity. Rufiji Delta, Tanzania showed inherent resilience owing to location on an uplifting coastline with a macrotidal range, but showed vulnerability from human impacts and lower local community management capacity. The most critical components to the vulnerability assessment were found to be exposure components of relative sea level trends and sediment supply, and sensitivity components of forest health, recent spatial changes and net accretion rates. The results provide a baseline against which to establish long-term ongoing monitoring, allowing continued assessment of the complex dynamics of climate change impacts, and providing an information base for strategic management decisions.
169 citations
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TL;DR: In this paper, the authors presented the estimation of ecosystem carbon stock in the Sundarbans using a large scale data set collected from systematic grid samples throughout the forest, and the results revealed that no matter whether the mangroves are tall or dwarf, a significant amount of carbon is stored into the sediment.
Abstract: The Sundarbans (21o30′–22o30′ N and 89o00′–89o55′ E) is the largest mangrove forest in the world. Forests are very important for sequestering atmospheric carbon and mangroves are amongst the most efficient in carbon sequestration. This study presents the estimation of ecosystem carbon (above- and belowground) stock in the Sundarbans using a large scale data sets collected from systematic grid samples throughout the forest. The variation of carbon stock in different vegetation types and in different salinity zones in Sundarbans was investigated. The relationships between carbon stock and different vegetation functional attributes (basal area, mean tree height, crown coverage etc.) were also investigated. The amount of carbon stored varied significantly among vegetation types, salinity zones and vegetation functional attributes (P < 0.05). Sundri (Heritiera fomes) dominated forest types store more ecosystem carbon (360.1 ± 22.71 Mg C ha−1) than other vegetation types. The fresh water zone shows the highest ecosystem carbon stock (336.09 ± 14.74 Mg C ha−1) followed by moderate and strong salinity zones. Salinity was found to enhance belowground carbon stock as revealed by the lowest proportion of belowground carbon stock (57.2 %) with respect to ecosystem carbon in fresh water zone and by the highest (71.9 %) in strong salinity zone. The results also reveal that no matter whether the mangroves are tall or dwarf, a significant amount of carbon is stored into the sediment. The vegetation attributes (basal area and mean tree height) of the dominant mangrove species in each vegetation type were identified as the key indicator of ecosystem carbon stock. We recommended some generalized regression equations to predict ecosystem carbon stock from basal area or mean tree height.
138 citations
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TL;DR: In this article, the authors used a similar approach to classify the macrohabitats of the black-water floodplains, rich in humic substances, poor in nutrients and acidic (igapo) of the Negro River and its blackwater tributaries.
Abstract: The Amazon River and its large tributaries are bordered by floodplains covering tens of thousands of square kilometers. Studies on the structure, function, and species composition have allowed a classification of the macrohabitats of Amazonian white-water floodplains, rich in suspended matter and nutrients and of neutral pH (varzea). Here we describe the use of a similar approach to classify the macrohabitats of the black-water floodplains, rich in humic substances, poor in nutrients and acidic (igapo) of the Negro River and its black-water tributaries. With 12 subclasses and 25 macrohabitats, the igapo is less complex than the varzea. Although white-water and black-water rivers are subjected to similar flood regimes, the low sediment load and shallower declivity of the Negro River lead to reduced sedimentation and erosion processes. Differences in nutrient levels between both ecosystems influence species composition, richness, and growth rates of higher plant communities. Species richness is lower in igapo than in varzea, and wood increment and litter production of igapo trees is about half that reported for varzea trees. In addition, igapo lacks highly productive herbaceous plant communities that are common in varzea. The classification of igapo macrohabitats provides a valuable tool for the elaboration of sustainable management strategies and conservation. While many varzea macrohabitats are suitable for small-scale agriculture, animal husbandry, forestry and commercial fisheries, the carrying capacity of igapo is limited and allows only for subsistence-level fishery and agriculture, the capture of ornamental fishes, and ecotourism. We argue that the biota of most igapo macrohabitats is highly sensitive to changes in hydrological cycles as caused by river damming and/or by climate change.
116 citations
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TL;DR: In this article, the authors examined decadal, annual, and spatial variation in wildlife-vehicle collisions along highway BR-262 in the southern Pantanal, and specifically, what is the rate of roadkill along BR- 262, and did it increased over the previous decade, which species are frequently victims of collisions and does this vary annually along the highway's length, and how can the context of collisions inform mitigation?
Abstract: The Pantanal of Brazil, the world’s largest freshwater wetland, supports a large diversity of species and is under continually increasing pressure from human development, including vehicle collisions with wild animals. We examined decadal, annual, and spatial variation in wildlife-vehicle collisions along highway BR-262 in the southern Pantanal, and specifically: (1) what is the rate of roadkill along BR-262, and did it increased over the previous decade, (2) which species are frequently victims of collisions and does this vary annually along the highway’s length, and (3) what anthropogenic or environmental factors may influence this variation and how can the context of collisions inform mitigation? We sampled the highway monthly, between April 2011 and June 2012, stopping when roadkill was observed to identify species and collect GPS coordinates and a photographic record. Data was analyzed temporally and in relation to traffic volume and precipitation, and imported into a GIS and analyzed spatially and in relation to elevation. We recorded 518 carcasses from 40 species over the 15 sampling periods. The rate of roadkill incidents was 1 every 6.2 km, a tenfold increase since 2002, and is now one of the highest in Brazil. IUCN Red List species were observed, including lowland tapir, giant anteater, and marsh deer. At the lowest elevations, during seasonal wetland inundation the causeway embankment is sought for refuge, increasing collision probability. Mitigation measures tied to seasonal flood pulse variation along the causeway may reduce the high rate of wild animal mortality and loss of biodiversity.
62 citations
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TL;DR: Wetland grasslands are generally able to withstand extremely heavy grazing over the dry season without becoming degraded because they are inaccessible to grazers during the period of flooding over the wet season, giving plants a full growing season's recovery period and storing a large proportion of their biomass in deep root systems and rhizomes as discussed by the authors.
Abstract: African wetlands include dambos or headwater valley grasslands in the upper regions of catchments, circular pan grasslands in drainage sumps, linear riverine grasslands in the mid regions of catchments and broad floodplains, swamps and deltas in the lower regions of catchments. Plant zonation on flood frequency and duration gradients occurs in predictable sequences across Africa and this variation combined with increasing retention of soil moisture for plant growth over the dry season with increasing flooding provides critical resource heterogeneity for herbivores. Consequently, wetlands are essential dry-season habitats for wild and domestic herbivore populations across Africa, often providing key resources that buffer herbivore population numbers in the face of severe dry seasons and droughts. Floodplain peripheries and shallow to intermediate-depth floodplains are generally preferred over the early dry season, with deep floodplains and swamps being used by the late dry season and during droughts. Wetland grasslands are generally able to withstand extremely heavy grazing over the dry season without becoming degraded because they are inaccessible to grazers during the period of flooding over the wet season, giving plants a full growing season’s recovery period, as well as by wetland grasses storing a large proportion of their biomass in deep root systems and rhizomes. African wetlands are under siege by upstream damming and by agricultural projects and further/reinforced conservation measures are needed to protect them, such as ecologically designed water releases from dams to maintain flooding regimes and prevention of agriculture on key floodplains for grazers.
61 citations
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TL;DR: In this paper, the authors used multitemporal PALSAR L-band radar imagery combined with object-based image analysis, data mining techniques and field data to derive vegetation structure and inundation patterns and characterize major vegetation types in varzea forests of the Mamiraua Sustainable Development Reserve.
Abstract: Remote sensing studies of vegetation cover and hydrologic dynamics in Amazonian wetlands have been mostly limited temporally or spatially, and the distribution and spatial configuration of Amazonian varzea habitats remains poorly known. This study uses multitemporal PALSAR L-band radar imagery combined with object-based image analysis, data mining techniques and field data to derive vegetation structure and inundation patterns and characterize major vegetation types in varzea forests of the Mamiraua Sustainable Development Reserve. Our results show that the combination of vegetation cover and inundation extent information can be a good indicator of the complex gradient of habitats along the floodplain. The intersection between vegetation and flood duration classes showed a wider range of combinations than suggested from field based studies. Chavascal areas—chacaracterized as a dense and species-poor shrub/tree community developing in old depressions, abandoned channels, and shallow lakes—had shorter inundation periods than the usually recognized hydroperiod of 180–240 days of flooding, while low varzea—a diverse community that have fewest and smallest species, and highest individual density and that tolerate 120–180 days of flooding every year—was distributed between flood duration ranges that were higher than reported by the literature. Forest communities growing at sites that were never mapped as flooded could indicate areas that only flood during extreme hydrological events, for short periods of time. Our results emphasize the potential contribution of SAR remote sensing to the monitoring and management of wetland environments, providing not only accurate information on spatial landscape configuration and vegetation distribution, but also important insights on the ecohydrological processes that ultimately determine the distribution of complex floodplain habitat mosaics.
51 citations
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TL;DR: In this article, the authors consider the extent to which methodological improvements and improved coordination between researchers could help to fill this gap and identify areas where further research and better coordination are particularly needed in order to reduce the uncertainties in estimates of tropical peatland carbon pools and fluxes.
Abstract: Our limited knowledge of the size of the carbon pool and exchange fluxes in forested lowland tropical peatlands represents a major gap in our understanding of the global carbon cycle. Peat deposits in several regions (e.g. the Congo Basin, much of Amazonia) are only just beginning to be mapped and characterised. Here we consider the extent to which methodological improvements and improved coordination between researchers could help to fill this gap. We review the literature on measurement of the key parameters required to calculate carbon pools and fluxes, including peatland area, peat bulk density, carbon concentration, above-ground carbon stocks, litter inputs to the peat, gaseous carbon exchange, and waterborne carbon fluxes. We identify areas where further research and better coordination are particularly needed in order to reduce the uncertainties in estimates of tropical peatland carbon pools and fluxes, thereby facilitating better-informed management of these exceptionally carbon-rich ecosystems.
42 citations
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TL;DR: Zhang et al. as discussed by the authors investigated plant species compositions, hydrological gradients, and soil variables in four dominant plant communities and examined the relationships between communities and abiotic factors by using detrended canonical correspondence analysis (DCCA) in wetlands associated with Dongting Lake.
Abstract: Hydrological regime and edaphic factors may operate synergistically to influence plant distribution in wetlands. However, this phenomenon has rarely been examined in freshwater lacustrine wetlands in China. Here, we investigated plant species compositions, hydrological gradients, and soil variables in four dominant plant communities and examined the relationships between plant communities and abiotic factors by using detrended canonical correspondence analysis (DCCA) in wetlands associated with Dongting Lake. The first and second axes of the DCCA ordination explained approximately 52.8 and 26.3 % of the total variance of the species–environment relationship, respectively. Water table depth was the strongest factor related to plant community composition and reflected the spatial distribution of vegetation in wetlands. Water-related soil variables (soil moisture content, bulk density, oxidation–reduction potential, and electrical conductivity) were significantly related to plant distribution. Soil nutrient factors (soil organic matter, total nitrogen, available potassium, and Olsen phosphorus) also played a role in plant distribution. Our findings emphasized the importance of hydrological gradients and related edaphic factors in determining the distribution of vegetation in freshwater wetlands. These findings have implications for conservation of freshwater lacustrine wetlands, which are often subjected to hydrological alteration and nutrient enrichment caused by anthropogenic disturbances and climate change.
42 citations
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TL;DR: In this paper, the most effective coastal protection systems consist of different elements arranged in series, for instance natural floodplains vegetated with mangroves and a sound dyke line.
Abstract: The dynamic coastlines in the Lower Mekong Delta of Vietnam are threatened by the impacts of climate change, particularly by the increased intensity and frequency of storms and floods, as well as by rising sea levels. The most effective coastal protection systems consist of different elements arranged in series, for instance natural floodplains vegetated with mangroves and a sound dyke line. However, the unsustainable use of natural resources and development in the coastal zone are threatening the protection function of the mangrove forest belt. In sites where severe erosion has destroyed the mangrove belt, restoration of floodplains and mangrove rehabilitation is only possible after the wave energy has been reduced by physical barriers. This can be achieved with bamboo fences, which reduce erosion and stimulate sedimentation. Restoration of the eroded floodplains creates the pre-conditions for rehabilitation of the destroyed mangrove forest. Mangrove management is an important element of an area costal protection strategy.
40 citations
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TL;DR: In this paper, a principal component analysis (PCA) was applied to a complete annual dataset of filtered EVI2 images (based on a 12-year average over the 2001-2012 period).
Abstract: The present study aimed at analyzing the spatio-temporal variability of the Pantanal vegetation cover, the largest tropical wetland in the world. A principal component analysis (PCA) was applied to a complete annual dataset of filtered EVI2 images (based on a 12-year average over the 2001–2012 period). There was about 99 % variance concentration in the first three components, with the respective loading responses and distributions (maximum, minimum and changes in the sign of the eigenvector loadings) matching the most significant seasonal interruptions. The first three principal components showed the essential aspects of the spatio-temporal variability of the local phenology, i.e. the cumulative greenness throughout the year, the later and more generalized senescence associated with the drought season climax, and the early senescence associated with sandy portions. Our results enabled the detection of homologous areas regarding vegetation density and the time and intensity of senescence. As the water availability throughout the year—the most important parameter for regional vegetation—is largely a function of geology (sediment grain size and vertical neotectonic), a geobotanic analysis of the Pantanal wetlands was also possible. Our PCA-based approach was able to capture the essentials of the phenological/environmental variability, with potential for application in other ecosystems with complex vegetation cover and functioning.
38 citations
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TL;DR: Wang et al. as mentioned in this paper investigated the trends and characteristics of individuals visiting four wetlands in South Korea and found that most visitors visited wetlands for sightseeing (50.94 %) or educational purposes (36.42 %) and remained for less than 2 hours.
Abstract: We investigated the trends and characteristics of individuals visiting four wetlands in South Korea. A total of 21,647,242 people visited the four wetlands from 2007 to 2012. The number of visitors increased significantly after the tenth Conference of Contracting Parties to the Ramsar Convention on Wetlands held in South Korea in 2008. Visitor data showed statistical evidence of seasonality in visits, with visitor numbers peaking in autumn of each year in all wetlands, probably because of the seasonality of natural resource availability in wetlands. Our findings are based on a self-administrated questionnaire survey completed by 600 respondents (150 from each wetland). Most respondents visited wetlands for sightseeing (50.94 %) or educational purposes (36.42 %) and remained for less than 2 h. Visits were primarily spent participating in educational and sightseeing programs. Thus, wetland visitor centers have an important role in wetland ecotourism and education. Guided educational and sightseeing programs for visitors, including independent, group, and family tourists, are helpful for effectively raising awareness of wetlands and distributing ecotourism concepts. Our study demonstrates that visiting wetlands is becoming an increasingly popular form of ecotourism in South Korea, supporting the importance of preserving this fragile ecosystem service.
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TL;DR: In this paper, an approach to improving ecological understanding by seeking relationships between archival remote sensing data and floodplain vegetation data was described. But the methods used are simple, objective, repeatable and inexpensive.
Abstract: Characterising hydroperiod and vegetation for flood-pulsed wetlands is a critical first step towards understanding their ecology. In large, data-poor wetlands such as Botswana’s Okavango Delta, quantifying hydrology and ecology presents great logistic and financial challenges, yet relationships between hydrology and floodplain ecology are essential inputs to management. This paper describes an approach to improving ecological understanding by seeking relationships between archival remote sensing data and floodplain vegetation data. We produced a high spatial resolution (30 × 30 m) time series of annual flood frequency from Landsat 5TM imagery for the period 1989–2009. A second, lower spatial resolution (250 × 250 m) series of monthly flood extent was developed from a band 1 (0.62–0.67 μm) threshold of MODIS (MOD09Q1) imagery for the period 2000–2012. Vegetation composition and abundance was sampled in 30 floodplain sites, using a modified Braun-Blanquet approach. Interpreted flood extent from MODIS was 92 % accurate compared to the Landsat interpretation, and 89 % accurate when assessed against field data. Three major classes of floodplain vegetation were identified from ordination and cluster analysis: Occasionally flooded savanna, Seasonally flooded grassland, and Seasonally flooded sedgeland. Relationships identified between hydroperiod and vegetation communities were tested against five validation sites, in four of which indicator species occurrence was predicted with ≥60 % accuracy. The methods used are simple, objective, repeatable and inexpensive. Relating floodplain vegetation to hydrological history provides a means of predicting shifts in species composition and abundance for given changes in hydrology.
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TL;DR: Investigating the effect of plant invasion, subsequent removal and replanting with a native species on C, N and P stoichiometry of the plant–soil system in the tidal wetlands of the Minjiang River shows that a conservative strategy and a high N-use efficiency and internal plant control of the N in the ecosystem underlie the invasive success of Spartina in this N-limited wetland.
Abstract: The tidal estuarine wetlands of China are rich in plant diversity, but several human-driven processes, such as species invasion, can affect the biogeochemical cycles of these ecosystems, and by changing soil conditions can inhibit the regeneration of native vegetation. We seasonally analyzed the carbon (C), nitrogen (N) and phosphorus (P) concentrations in soils and in leaves, stems and roots of the invasive species Spartina alterniflora and of the native species Cyperus malaccensis var. brevifolius Boeckeler. This latter species was analyzed both in natural non-invaded stands and in stands that had been invaded by Spartina but from which it had been removed and replaced by Cyperus. The aim was to investigate the effect of plant invasion, subsequent removal and replanting with a native species on C, N and P stoichiometry of the plant–soil system in the tidal wetlands of the Minjiang River. C and N concentrations averaged across seasons did not differ significantly among the plant species. P concentration was lower in the stems of Spartina than in the stems of the native species Cyperus but was not significantly different in the roots of the two species. The soil C and N concentrations were higher in the Spartina stand than in the Cyperus stand, whereas the soil P concentrations were not significantly different. The invasive species had a higher N-resorption capacity, N:P ratios in stem and roots, biomass, absolute growth and biomass N and had a lower relative growth rate and litter production than the native species. After the removal of the invasive plants, the regenerating native plants have a higher capacity to resorb N and lower relative growth rates. All these traits show that a conservative strategy and a high N-use efficiency and internal plant control of the N in the ecosystem underlie the invasive success of Spartina in this N-limited wetland. Relative growth rate was associated with lower plant N:P ratios, whereas absolute growth rate was associated with higher nutrient-use efficiency and lower C and N turnover and storage capacities in the biomass. Changes in soil properties produced by the establishment of an invasive plant can condition the later regeneration of native plants.
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TL;DR: In this paper, the authors investigated the role of agribusiness in the degradation of the Vereda and Murundu wetlands in the Cerrado catchment of Brazil, and found that the transition zone between dry and wet soils is the most fragile and susceptible to degradation due to the continuous expansion of land tillage.
Abstract: Vereda and Murundu wetlands are widespread in the Cerrado (Brazilian savannah). The wetlands occupy topographic depressions on the flat plateau, which are permanently or seasonally waterlogged, with topsoil that has high contents of organic matter and endemic fauna and flora. These systems are important for regulating the water flux in the riverine network. Despite their environmental importance, the wetlands are largely neglected in planning policy, environmental legislation and scientific research, resulting in their degradation by the expansion and intensification of agriculture. In the studied catchment, a typical tropical savannah landscape and a region of typical agribusiness land use in the state of Minas Gerais was considered, where the Vereda and Murundu ecosystems are completely surrounded by agriculture. The transition zone between dry and wet soils is the most fragile and susceptible to degradation because it is subjected to the continuous expansion of land tillage. If the agribusiness model deployed in the region is responsible for the increase in wetland destruction, then changes in regulatory laws to define and preserve permanent preservation areas in the Brazilian Forest Code, for the years 1934, 1965, 1989 and in the two versions from 2012, are an impediment to the effectiveness of forest and wetlands protection and the policy of sustainable development.
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TL;DR: In this paper, the authors compared the food web structure of a fringing mangrove-seagrass habitat and three fluvio-lagoons with marsh-eelgrass and mangroves-bare sediments during a dry season in Terminos Lagoon and Centla Wetlands, Southern Gulf of Mexico.
Abstract: Tropical coastal habitats like marshes, mangroves, and submerged grasses comprise diverse plant and animal communities and a certain degree of connectivity with other ecosystems. We compared the food web structure of a fringing mangrove-seagrass habitat and three fluvio-lagoons with marsh-eelgrass and mangrove-bare sediments during a dry season in Terminos Lagoon and Centla Wetlands, Southern Gulf of Mexico. Analysis of δ13C and δ15N stable isotopes in tissues of aquatic consumers, primary producers, and other carbon sources, in combination with isotope-based Bayesian methods, were performed to determine the main food sources and the isotopic niche of the consumers’ communities. Consumers in the mangrove-seagrass site showed high dependence on phytoplankton (average contribution 31 %), macroalgae (20 %) and organic matter derived from seagrasses (17 %). In the fluvio-lagoons, consumers showed high dependence on marginal vegetation (16–46 %). Phytoplankton and mangrove epiphytes comprised other important resources at these sites (with contributions of 24–44 %). The isotopic niche of consumers from the fringing mangrove-seagrass site did not overlap with those from the fluvio-lagoons. Moreover, despite the predominance of generalist consumers in all sites, differences in their isotopic niche area were observed, with consumers from the marsh-eelgrass site showing the narrowest. This suggests that consumer resource availability greatly differs in these habitats. Our results provide valuable information that help increase our understanding about the trophic structure in these important estuarine systems.
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TL;DR: In this paper, the authors compared results from previous studies in 1982 and 1999 and found that harvesting of mangrove wood, livestock browsing and trampling and footpaths occurred in more than 70 % of the estuaries.
Abstract: Seventeen estuaries that are permanently open to the sea provide habitat for mangrove forests along the Eastern Cape coast, South Africa These mangroves are of interest as they occur at one of the most southerly distributions in the world Climate change will influence future distribution patterns while present anthropogenic impacts are causing mangrove loss Mangrove area and species distribution in 2012 were compared with results from previous studies in 1982 and 1999 Anthropogenic impacts were noted and showed that harvesting of mangrove wood, livestock browsing and trampling and footpaths occurred in more than 70 % of the estuaries Browsing on trees by cattle resulted in a clear browse-line and browsing on propagules mainly by goats reduced seedling establishment Over the past 30 years, a total loss of 315 ha of mangroves was observed for all 17 estuaries However in three estuaries mangroves had re-established where they had been previously lost Extreme events such as floods and closure of the estuary mouth to the sea caused large changes in mangrove area in small estuaries In contrast in the larger forests which occurred in the larger estuaries, anthropogenic pressures such as harvesting reduced the area of mangroves Predicted climate changes coupled with anthropogenic impacts are likely to accelerate the loss of mangroves More sustainable practices are urgently needed to protect biodiversity and the ecosystem services that these forests provide
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TL;DR: In this article, a study was conducted to determine whether long-term overgrazing has affected carbon (C) storage in plant and soil pools in wet and mesic meadows.
Abstract: Wet meadows are important ecosystems for forage production and as carbon reservoirs in semi-arid areas. In Patagonia, Argentina, large areas of wet meadows have been classified as overgrazed by livestock. The objective of this study was to determine whether long-term overgrazing has affected carbon (C) storage in plant and soil pools in wet and mesic meadows. The study occurred in Northern Patagonia, in three study sites located along a precipitation gradient. Our results indicate that long-term overgrazing reduced, on average, 35 % of the total ecosystem C pool. There was significantly lower aboveground and belowground plant production in heavily grazed compared to lightly grazed sites, 419 ± 262 – 128 ± 110 g m2 year−1 and 3796 ± 2622 – 1702 ± 1012 g m2 year−1, respectively. Soil C concentrations were also less in heavily grazed sites (184 ± 98 – 105 ± 58 g kg−1 at 1 m depth, respectively). The response of meadows to long-term heavy grazing also appears to be influenced by different levels of precipitation, with sites in drier areas being apparently more susceptible to overgrazing. Our results indicate that new management and restoration practices are needed to stop and reverse meadow deterioration in degraded meadows of Northern Patagonia.
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TL;DR: In this article, the root sampling procedure applied for A. marina and S. alba trees was used for quantification of tree BGB for Avicennia marina (Forssk), Sonneratia alba J. Smith and Rhizophora mucronata Lam.
Abstract: A review of studies on belowground biomass (BGB) of mangroves revealed that procedures for excavation and determination of dry weight are insufficiently documented. The main objective of this study was therefore to describe procedures for quantification of tree BGB for Avicennia marina (Forssk.), Sonneratia alba J. Smith and Rhizophora mucronata Lam. The study covered four sites in Tanzania where 30 trees were sampled (10 for each species). A new root sampling procedure applied for A. marina and S. alba seemed to work adequately. Dry to fresh weight ratios (DF-ratios) varied between tree species, between tree sizes and between root components. Therefore, for each tree species, tree- and root component-specific DF-ratios were applied for dry weight determination. For A. marina and S. alba trees, a significant proportion of total tree BGB is stored in the root crown (34 and 10 % respectively). Future studies should therefore ensure inclusion of root crown when accounting for total tree BGB. Tests of previously developed models on our data revealed large prediction errors, partly due to differences in site conditions and partly due to incomprehensive excavation procedures applied when these models were developed. Local tree BGB models for mangroves should therefore be developed.
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TL;DR: In this article, allometric relationships between easily measurable independent variables like diameter at breast height (DBH) and total height (TH) and biomass of leaf, branch, bark, stem without bark, and total above-ground biomass of Excoecaria agallocha L. were tested.
Abstract: Allometric relationships between easily measurable independent variables like diameter at breast height (DBH) and total height (TH) and biomass of leaf, branch, bark, stem without bark, and total above-ground biomass of Excoecaria agallocha L. were tested. Similarly, relationships between independent variables (DBH and HT); and nutrients (N, P and K) and carbon content in total above-ground biomass were also evaluated. The best fit allometric models were selected by considering the values of parameter of estimation of the models such as R2, CV, Rmse, MSerror, Sa, Sb, and Akaike’s information criterion corrected (AICc). The selected allometric models were Log Biomass = 0.9256 Log DBH2 − 2.133; Log biomass = 1.1656 Log DBH2 − 1.7047; Log biomass = 1.0824 Log DBH2 − 1.7568; Log biomass = 1.0927 Log DBH2 − 1.0275; Log biomass = 1.0996 Log DBH2 − 0.8572 respectively for leaf, branch, bark, stem without bark and total above-ground biomass. Whereas the selected allometric models for nitrogen, phosphorus, potassium and carbon were Log N = 1.0972 Log DBH2 − 3.0845; Log P = 1.0947 Log DBH2 − 5.6790; Log K = 1.0990 Log DBH2 − 3.0370; Log C = 1.1 Log DBH2 − 1.1937 respectively. Highest concentration of nitrogen (16.07 mg/g) and phosphorus (0.05 mg/g) was observed in leaf, while higher concentration (45.95–48.60 %) of carbon was observed in stem and bigger branches. The findings of this study are first-hand information for forest managers and conservation workers for sustainable management of E. agallocha in the Sundarbans of Bangladesh.
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TL;DR: In this article, the authors proposed an approach that integrates spatial variables that have not been previously used, including type of wetland (complex or isolated) and land use (% of agricultural, urban, forest and water land cover), at a much finer geographical scale of 50 km2.
Abstract: Climate change will cause major changes in ecosystems. Therefore, it is crucial that climate change policy consider the value of all services that are provided by watershed ecosystems. For this purpose, geospatial data and economic analysis are combined to determine a monetary value for wetland ecosystem goods and services (EGSs) in the watersheds of the Yamaska and Becancour Rivers (Quebec, Canada). From published studies of wetland economic evaluations, we selected 51 relevant studies from 21 countries and performed a benefit transfer using meta-analysis. Our research emphasises the importance of considering multiple wetland characteristics when conducting a benefit transfer because of their complementary effects. We propose an approach that integrates spatial variables that have not been previously used, including type of wetland (complex or isolated) and land use (% of agricultural, urban, forest and water land cover), at a much finer geographical scale of 50 km2. Simultaneous use of detailed spatial and economic characteristics in each wetland area allowed us to assign heterogeneous EGS values and map these values in sub-watersheds (50 km2) of the two rivers. Our results demonstrate that location and scale can affect wetland value. When wetland valuation was conducted based on mean values for geospatial characteristics, the EGS [2014 purchasing power parity (PPP) price] that is provided by wetlands was $5277 PPP/ha/year for the Yamaska River Watershed (YRW) and $3979 PPP/ha/year for the Becancour River Watershed (BRW). When wetland valuation was performed at a more detailed sub-watershed scale to reflect variability within a watershed, EGS (2014 PPP price) that is provided by wetlands was valued higher at $9080/ha/year for YRW and $4702/ha/year (2014 PPP price) for BRW.
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TL;DR: In this paper, the first national estimation of carbon stocks in freshwater wetlands based on the compilation of soil carbon data from 126 sites across the country was presented, where the authors estimated C stocks for two soil sample types (mineral and organic) in different classes of wetlands (fen, bog, swamp, marsh, pakihi and ephemeral), and extrapolated C stocks to national level using GIS.
Abstract: Freshwater wetlands provide a range of ecosystem services, one of which is climate regulation. They are known to contain large pools of carbon (C) that can be affected by land-use change. In New Zealand, only 10 % of the original freshwater wetlands remain due to conversion into agriculture. This study presents the first national estimation of C stocks in freshwater wetlands based on the compilation of soil carbon data from 126 sites across the country. We estimated C stocks for two soil sample types (mineral and organic) in different classes of wetlands (fen, bog, swamp, marsh, pakihi and ephemeral), and extrapolated C stocks to national level using GIS. Bogs had high C content and low bulk densities, while ephemeral wetlands were the reverse. A regression between bulk density and C content showed a high influence of the soil type. Average C densities (average ± standard error) were 1,348 ± 184 t C ha−1 at full peat depth (average of 3.9 m) and 102 ± 5 t C ha−1 (0.3 m depth) for organic soils, and 121 ± 24 t C ha−1 (0.3 m depth) for mineral soils. At national level, C stocks were estimated at 11 ± 1 Mt (0.3 m depth) and 144 ± 17 Mt (full peat depth) in organic soils, and 23 ± 1 Mt (0.3 m depth) in mineral soils. Since European settlement, 146,000 ha of organic soils have been converted to agriculture, which could release between 0.5 and 2 Mt CO2 year−1, equivalent to 1–6 % of New Zealand’s total agricultural greenhouse gas emissions.
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TL;DR: In this article, the authors identified and mapped subtropical Argentine High Andean peatbogs based in a supervised classification of Landsat images, and a posteriori spatial processing to define functional units.
Abstract: Peatbogs are the most productive and biodiversity rich ecosystems of high dry Puna region, and provide essential ecosystems services to local inhabitants. Despite their ecological and economic importance, the geographic patterns and distribution of peatbogs as well the dynamic of this system are barely known. In this work we (1) identified and mapped subtropical Argentine High Andean peatbogs based in a supervised classification of Landsat images, and a posteriori spatial processing to define functional units; (2) used such classification to characterize the whole Argentina Puna region (14.3 million hectares) in terms of their geographic patterns of peatbogs; and (3) characterized the region’s sub-watersheds according to their peatbogs density and geographic characteristics. The post-process map reports a total area of peatbogs of 94427.55 ha (0.66 % of total study area) with 10,428 polygons. The majority of peatbogs are small or median (i.e., 21.8 % of total area included 10,000 ha represent 18 % of total area. Peatbogs density is spatially heterogeneous, with much higher density in the north and central east of the study area. Sub-watershed can be grouped into six main groups according to the percentage of peatbogs cover, mean size of peatbogs and altitude. The combination of basic information, such as map of peatbogs cover with spatial patterns characterization, is a priority input for the conservation planning of this extensive and valuable ecosystem, and to ongoing land use planning initiatives.
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TL;DR: In this paper, the effects of multi-decadal drying and drainage on plant community structure and productivity in four fens located in Alberta, Canada were examined, and it was found that long-term drying resulted in a two to fourfold increase in total biomass in three of the four fen sites, with a similar large increase in NPP in Treed Fen 1.
Abstract: Land-use and climate change are expected to cause drying of vegetation and surface soils in continental boreal peatlands. We examined the effects of multi-decadal drying and drainage on plant community structure and productivity in four fens located in Alberta, Canada. Long-term drying resulted in a two to fourfold increase in total biomass in three of the four fen sites, with a similar large increase in NPP in Treed Fen 1. The treed poor fens consistently had decreased moss cover and productivity with drainage. Across all sites, changes in understory community composition were related to the change in water table position as well as overstory canopy development that occurred post-drainage. Overall, drainage induced a shift toward a drier peatland regime, favoring increased canopy and vascular plant density at the expense of ground-layer mosses or the understory. Within the ground layer communities, drainage favored dry-adapted hummock moss and lichen species over those wet-adapted but dessication-prone species typical of low-lying lawns and hollows. Alteration of fen vegetation due to ecosystem drying will not only influence carbon sequestration but also will increase the vulnerability of peatlands to wildfire, increasing the risk of further ecosystem degradation and possible loss of resilience.
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TL;DR: This review focused on some specific histo-physiological features of the mangroves that help them to adjust and grow extensively in the saline rich coastal regions.
Abstract: This review focused on some specific histo-physiological features of the mangroves that help them to adjust and grow extensively in the saline rich coastal regions. Sundarban, the largest chunk of coastal ecosystems of the world located between India and Bangladesh has the widest range of mangrove species in its tidal influenced highly saline soil. Several anatomical characteristics to conserve water are mostly species specific and unique to these plants as such characteristics are not found in their genetically close relatives. The most conspicuous features are succulent leaves with increased mesophyll area, thick cuticle and wax deposition on epidermis. Chlorenchyma cells with large vacuoles are often found associated with different forms of salt secreting glands. A cavitation resistant xylem structure in the stem is one of the mechanisms of mangroves to safeguard their water transport. Non-annual growth ring in some mangroves could be a potential proxy for past environmental conditions. Most root systems show reduced cortex with aerenchyma but wider casparian strip. These anatomical characteristics are the basis for their physiological adaptation to high saline condition. Mangroves can regulate ion homeostasis under salt stress by salt secretion, ultrafiltration and ion sequestration. Salinity stress leads to accumulation of reactive oxygen species (ROS), peroxidation of membrane lipids and inactivation of proteins. Mangroves can activate diverse components of their antioxidative system to eliminate H2O2 and restrict the accumulation of ROS. All these characteristics help the mangroves to photosynthesize optimally and show a good vegetative growth under tidal influenced varied saline condition.
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TL;DR: Evaluated optical indices sensitive to vegetative development and surface water along with Synthetic Aperture Radar backscatter values were the most useful for mapping hydroperiod across habitats and emphasize the utility of satellite remote sensing for rice decision making and as cost-effective tools for supporting Monitoring, Reporting, and Verification protocol.
Abstract: Information on rice paddy practices and rice habitat is required by decision makers and monitoring protocol to manage the agricultural wetlands of the Sacramento Valley, California. Satellite remote sensing imagery have been able to support these needs with accurate maps of rice extent and delineation of winter flooding. However, delineation of rice and habitat, paddy hydroperiod, and spatiotemporal dynamics have not been thoroughly carried out in the region. The objective of this research application was to evaluate cost-efficient synthetic aperture radar and optical imagery for mapping agricultural wetlands and hydroperiod management. Ground-truth field data from the Glenn-Colusa Irrigation District was used to test a suite of remote sensing indices to differentiate among agricultural wetland types and irrigation practices. A Classification And Regression Tree approach that utilized the random forest algorithm was built to map the agricultural wetlands of the Sacramento Valley. Results show optical indices sensitive to vegetative development and surface water (Landsat NDVI and LSWI) along with Synthetic Aperture Radar backscatter values (PALSAR HH sigma nought σ° dB) were the most useful for mapping hydroperiod across habitats. Overpass timing and irrigation management were key factors in sensor and index selection. Nearly 93 % (185,494 ha) of rice paddies in the Valley underwent wet seeding practices and half (90,168 ha) of actively cultivated rice area was flooded during the winter. Eight percent (16,420 ha) of rice habitat received at least one irrigation application during the crop season. The most challenging habitat types to separate were fallow rice paddies that underwent different frequencies of inundation management due to permitting policies and duck habitat promotion. Overall, the results emphasize the utility of satellite remote sensing for rice decision making and as cost-effective tools for supporting Monitoring, Reporting, and Verification protocol.
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TL;DR: In this article, the authors provide an inventory, spatial distribution, and geochemical analysis of the lakes, and the characteristics of the associated surrounding landscape of the LN region in the Pantanal, and use that information to further add to the hypotheses on lake formation.
Abstract: The Brazilian Pantanal is an ecosystem of high biodiversity This biodiversity is largely supported by the dynamic hydrology and landscape of the region As part of the mosaic of this unique landscape, there are a variety of geochemically diverse lakes in the lower Nhecolândia (LN) sub-region The goal of this study was to provide an inventory, spatial distribution, and geochemical analysis of the lakes, and the characteristics of the associated surrounding landscape of the LN region in the Pantanal, and to use that information to further add to the hypotheses on lake formation To accomplish this, we made use of: (i) the spatial distribution of lakes and surrounding landscape units from a classification product generated from a combination of fine pixel resolution L-band ALOS/PALSAR, C-band Radarsat-2, and Envisat/ASAR; and (ii) in situ measured lake water geochemical propertiesWith an accuracy of 98 %, we found that the LN sub-region has 637 salinas and 8,214 baias The greatest degrees of salinas clustering are located in the southeast portion of the study area, and are surrounded by forested savanna, which are in higher grounds less prone to flooding Baias, however, are more broadly distributed in the region, and the highest occurrence is associated with the open mixed cover, comprised mostly of grasslands, which are in flood-prone areas Geochemically, salinas present a pH > 90 and total dissolved solids (TDS) generally >1,000 mg/L, while baias have a circum-neutral pH not much higher than 70, and TDS 90, comparable to the salinas, but relatively lower TDS and conductivity, and significant lower chloride The combination of the regional scale spatial data and associated geochemistry of lakes suggests that the geomorphological characteristics of the region, and consequent undulating terrains, create groundwater divides and groundwater-sheds that can develop local and regional flow systems and lead to lakes with different geochemistry The mechanisms responsible for the formation of the diversity of lakes in the region is likely due to combination of isolation from ground water/surface water recharge, evaporation, episodic flushing, and biogeochemical processes in the lake’s watersheds
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TL;DR: In this article, the authors compared the flight initiation distances (FID) of birds to recreational canoeing in arid northern Australia and found that can be used to establish buffers or codes of conduct for canoeists in wetlands, especially when water levels are low.
Abstract: Disturbance of birds by human activities is increasing and is of conservation concern. Little is known of the flight initiation distances (FID) of birds to recreational canoeing, although this activity is common and can occur in wetland areas inaccessible to vehicle or pedestrian traffic. We compared the FID evoked by a walker with that evoked by a canoe for 13 birds in wetlands in north–western Queensland. Canoes evoked shorter FIDs compared with walkers (means ± 95 % confidence intervals; 32.9 ± 7.6 m and 47.5 ± 7.4 m, respectively). These data could be used to establish buffers or codes of conduct for canoeists in wetlands in arid northern Australia, especially when water levels are low.
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TL;DR: In this paper, the optimal range and thresholds of aeration conditions, which impact methane formation in upper layers of peat originating from a natural fen (East Poland), were estimated.
Abstract: Methane is a greenhouse gas having well-known impacts on global radiative forcing. However, understanding the dynamics and thresholds of methane formation in peatlands, which undergo cyclic aeration and anoxia, is currently limited even though it is crucial for reliable estimation of methane emission to the atmosphere. The purpose of this study was to estimate the optimal range and thresholds of aeration conditions, which impact methane formation in upper layers of peat originating from a natural fen (East Poland). The experiment was conducted under laboratory conditions on two groups of differently treated soils which were incubated at field water capacity. One group was incubated in air and another in helium, both at temperatures of 5, 10 and 20 °C. Direct soil aeration estimation included measurements of redox potential and oxygen diffusion rate. The latter was used for the first time as an indicator of methane formation in soil. Both the aerated and anoxic groups showed that methane formation took place at ODR of below 20 μg O2 m−2 s−1 and Eh of below +240 mV which are the higher threshold levels for methanogenesis than previously reported. Maximum methanogenic activity amounted up to 71.86 mg CH4 kgDW−1 d−1. Aeration was capable of reducing this methanogenic activity by 28–100 %. Decreasing temperatures and aeration increased the time until the initiation of CH4 production (p < 0.05, n = 72).
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TL;DR: In this article, the authors revealed an inventory of 64 free-living marine nematode species from the Asia's largest coastal lagoon, Chilika (lat. 19°28′ and 19°54′N; long.
Abstract: The present study revealed an inventory of free-living marine nematode species from the Asia’s largest coastal lagoon, Chilika (lat. 19°28′ and 19°54′N; long. 085°05′ and 085°38′E), located in the East Coast of India and facing the Bay of Bengal. This study provided a checklist of 64 free-living marine nematode species belonging to 32 genera and 13 families. Among these, marine nematode species Oncholaimus oxyuris has been reported as new distributional record from Indian waters. The distribution of encountered nematode species was investigated in relation with environmental variables such as salinity and sediment texture throughout the lagoon. Most of the nematode species were found in stations which had high salinity (>6) and nature of sediments varied from sandy to silt/clay. However, few nematode families (e.g. Oncholaimidae and Microlaimidae) were also observed in low salinity stations of the lagoon indicating tolerance to variation in salinity.
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TL;DR: In this article, the benefits of integrating dense timeseries of Landsat sensor data for both validating assessments of change and determining the causes of change are outlined for wider application across the geographical range of mangroves in order to advance the development of JAXA's Global Mangrove Watch (GMW) program.
Abstract: Between 2007 and 2010, Japan's Advanced Land Observing Satellite (ALOS) Phased Arrayed L-band Synthetic Aperture Radar (PALSAR) captured dual polarization HH and HV data across the tropics and sub-tropics. A pan tropical dataset of Japanese Earth Resources Satellite (JERS-1) SAR (HH) data was also acquired between 1995 and 1998. The provision of these comparable cloud-free datasets provided an opportunity for observing changes in the extent of coastal mangroves over more than a decade. Focusing on nine sites distributed through the tropics, this paper demonstrates how these data can be used to backdate and update existing baseline maps of mangrove extent. The benefits of integrating dense timeseries of Landsat sensor data for both validating assessments of change and determining the causes of change are outlined. The approach is evaluated for wider application across the geographical range of mangroves in order to advance the development of JAXA's Global Mangrove Watch (GMW) program.