Terrestrial Wetlands Research Articles

Estimating of chlorophyll fluorescence parameter Fv/Fm for plant stress detection at peatlands under Ramsar Convention with Sentinel-2 satellite imagery

Monitoring vegetation is essential in Earth Observation (EO) due to its link with the global carbon cycle, playing a crucial role in ecosystem management. The fluorescence of chlorophyll (ChF) is a reliable indicator of plants' photosynthetic activity and growth, especially when they are experiencing unfavourable conditions, particularly in terrestrial wetlands. These wetlands are integral components of the landscape, contributing significantly to climate mitigation, adaptation, biodiversity, and the well-being of both the environment and humanity. We conducted a research study using the XGBoost machine learning algorithm to map the chlorophyll fluorescence parameter Fv/Fm in the Biebrza River Valley, which is known for its marshes, peatlands, and diverse flora and fauna. Our study highlights the benefits of using ensemble classifiers derived from EO Sentinel-2 satellite imagery for accurately mapping Fv/Fm across terrestrial landscapes under the Ramsar Convention at Narew River Valley (Poland) and Čepkeliai Marsh (Lithuania). The XGBoost algorithm provides an accurate estimate of ChF with a robust determination coefficient of 0.747 and minimal bias at 0.013, as validated using in situ data. The precision of Fv/Fm chlorophyll fluorescence parameter estimation from remote sensing sensors depends on the growth stage, emphasizing the importance of identifying the optimal overpass time for S-2 observations. Our study found that biophysical factors, as denoted by spectral indices related to greenness and leaf pigments, were highly impactful variables among the top classifiers. However, incorporating soil, vegetation and meteorological indicators from remote sensing data could further increase the accuracy of chlorophyll fluorescence mapping.

Impact of Water Table on Methane Emission Dynamics in Terrestrial Wetlands and Implications on Strategies for Wetland Management and Restoration

Impact of Water Table on Methane Emission Dynamics in Terrestrial Wetlands and Implications on Strategies for Wetland Management and Restoration

A review of carbon monitoring in wet carbon systems using remote sensing

Carbon monitoring is critical for the reporting and verification of carbon stocks and change. Remote sensing is a tool increasingly used to estimate the spatial heterogeneity, extent and change of carbon stocks within and across various systems. We designate the use of the term wet carbon system to the interconnected wetlands, ocean, river and streams, lakes and ponds, and permafrost, which are carbon-dense and vital conduits for carbon throughout the terrestrial and aquatic sections of the carbon cycle. We reviewed wet carbon monitoring studies that utilize earth observation to improve our knowledge of data gaps, methods, and future research recommendations. To achieve this, we conducted a systematic review collecting 1622 references and screening them with a combination of text matching and a panel of three experts. The search found 496 references, with an additional 78 references added by experts. Our study found considerable variability of the utilization of remote sensing and global wet carbon monitoring progress across the nine systems analyzed. The review highlighted that remote sensing is routinely used to globally map carbon in mangroves and oceans, whereas seagrass, terrestrial wetlands, tidal marshes, rivers, and permafrost would benefit from more accurate and comprehensive global maps of extent. We identified three critical gaps and twelve recommendations to continue progressing wet carbon systems and increase cross system scientific inquiry.

Methane in the Precambrian atmosphere

Biological methane production occurs in anoxic terrestrial wetlands and in sulfate depleted marine sediments. It has been suggested that methanogens may have flourished in the anoxic and sulfate-poor environments of the Precambrian ocean, generating large amounts of methane that would have accumulated in the atmosphere and warmed the early Earth. However, modern ferruginous and sulfate-poor environments such as Lake Matano are not very efficient at generating methane, converting only about 5% of organic carbon to CH4 despite the lack of alternative remineralization pathways. We apply this restriction to a simple model of marine carbon cycling in order to generate new estimates of methane concentrations in the Precambrian atmosphere. Our results suggest that, if the ancient biosphere were similarly inefficient, atmospheric methane concentrations did not exceed 1 ppm, or about twice the pre-industrial value, at any time during the Proterozoic. Following the evolution of oxygenic photosynthesis, the maximum methane concentration in the Archean atmosphere was order 100 ppm, but no more than 1 ppm if steady state oxygen concentrations were greater than 10−8 present atmospheric levels. Substantially larger methane concentrations are only possible before the evolution of oxygenic photosynthesis.

Increased methane concentration alters soil prokaryotic community structure along an artificial pH gradient

Global climate change may have a large impact on increased emission rates of carbon dioxide and methane to total greenhouse gas emissions from terrestrial wetlands. Methane consumption by soil microbiota in alpine wet meadows serves as a biofilter for the methane produced in the waterlogged soil below. Altered pH regimes change microbial community composition and structure by exerting selection pressure on soil microorganisms with different ecological strategies and thus affect greenhouse gas emissions resulting from the metabolic activity of soil microorganisms. However, responses of prokaryotic communities to artificial pH shift under elevated methane concentration remain unclear. In this study, we assessed diversity and relative abundance of soil prokaryotes in an alpine meadow under elevated methane concentration along an artificial pH gradient using laboratory incubation experiments. We established an incubation experiment treated with artificial pH gradient (pH 4.5–8.5). After 3 months of incubation, 300 ml of methane at a concentration of 20,000 ppm was added to stimulate potential methanothrophs in topsoil. Sequencing of 16S rRNA gene indicated increasing of relative abundances of Crenarchaeota, Chloroflexi, Bacteroidetes, and Planctomycetes in soil after addition of methane, while the relative abundances of Actinobacteria and Gemmatimonadetes did not significant change before and after methane treatment. Results of phylogenetic relatedness of soil prokaryotes showed that microbial community is mostly shaped by deterministic factors. Species indicator analysis revealed distinct OTUs among various pH and methane treatments. Network analysis revealed distinct co-occurrence patterns of soil prokaryotic community before and after methane addition, and different correlation patterns among various prokaryotic taxa. Linear regression model revealed significant decrease of methane oxidation along elevated pH gradient. Soil pH constituted a strong environmental filter in species assembly of soil prokaryotic community. Methane oxidation rates decreased significantly with elevated pH. The interactive effects of elevated methane concentration and pH are therefore promising topic for future research.

Petrogenic organic carbon retention in terrestrial basins: A case study from perialpine Lake Constance

Inland waters play a major role in the global carbon cycle, with particulate organic carbon (POC) burial in terrestrial wetlands surpassing that in ocean sediments. Lake Constance, the second largest lake at the periphery of the European Alps, receives POC sourced from both aquatic and terrestrial productivity as well as petrogenic OC (OCpetro) from bedrock erosion. Distinguishing POC inputs to lake sediments is key to assessing carbon flux and fate as reworked OCpetro represents neither a net sink of atmospheric CO2 nor source of O2. New stable and radiocarbon isotopic data indicate that 11 (9–12) Gg/yr of OCpetro is buried in Lake Constance with underlying sediments on average containing 0.3 (0.25–0.33) wt% OCpetro. Extrapolation of these results suggests that 27 TgOCpetro/yr (12–54 TgOC/yr) could be subject to temporary geological storage in lakes globally, which is comparable to estimates of 43−25+61 TgOCpetro/yr delivered to the ocean by rivers (Galy et al., 2015). More studies are needed to quantify OCpetro burial in inland sedimentary reservoirs in order to accurately account for atmospheric carbon sequestration in terrestrial basins.

Syntrophy Goes Electric: Direct Interspecies Electron Transfer.

Direct interspecies electron transfer (DIET) has biogeochemical significance, and practical applications that rely on DIET or DIET-based aspects of microbial physiology are growing. Mechanisms for DIET have primarily been studied in defined cocultures in which Geobacter species are one of the DIET partners. Electrically conductive pili (e-pili) can be an important electrical conduit for DIET. However, there may be instances in which electrical contacts are made between electron transport proteins associated with the outer membranes of the partners. Alternatively, DIET partners can plug into conductive carbon materials, such as granular activated carbon, carbon cloth, and biochar, for long-range electron exchange without the need for e-pili. Magnetite promotes DIET, possibly by acting as a substitute for outer-surface c-type cytochromes. DIET is the primary mode of interspecies electron exchange in some anaerobic digesters converting wastes to methane. Promoting DIET with conductive materials shows promise for stabilizing and accelerating methane production in digesters, permitting higher organic loading rates. Various lines of evidence suggest that DIET is important in terrestrial wetlands, which are an important source of atmospheric methane. DIET may also have a role in anaerobic methane oxidation coupled to sulfate reduction, an important control on methane releases. The finding that DIET can serve as the source of electrons for anaerobic photosynthesis further broadens its potential environmental significance. Microorganisms capable of DIET are good catalysts for several bioelectrochemical technologies and e-pili are a promising renewable source of electronic materials. The study of DIET is in its early stages, and additional investigation is required to better understand the diversity of microorganisms that are capable of DIET, the importance of DIET to carbon and electron flow in anaerobic environments, and the biochemistry and physiology of DIET.

Methane fluxes show consistent temperature dependence across microbial to ecosystem scales

Methane (CH4) is an important greenhouse gas because it has 25 times the global warming potential of carbon dioxide (CO2) by mass over a century. Recent calculations suggest that atmospheric CH4 emissions have been responsible for approximately 20% of Earth's warming since pre-industrial times. Understanding how CH4 emissions from ecosystems will respond to expected increases in global temperature is therefore fundamental to predicting whether the carbon cycle will mitigate or accelerate climate change. Methanogenesis is the terminal step in the remineralization of organic matter and is carried out by strictly anaerobic Archaea. Like most other forms of metabolism, methanogenesis is temperature-dependent. However, it is not yet known how this physiological response combines with other biotic processes (for example, methanotrophy, substrate supply, microbial community composition) and abiotic processes (for example, water-table depth) to determine the temperature dependence of ecosystem-level CH4 emissions. It is also not known whether CH4 emissions at the ecosystem level have a fundamentally different temperature dependence than other key fluxes in the carbon cycle, such as photosynthesis and respiration. Here we use meta-analyses to show that seasonal variations in CH4 emissions from a wide range of ecosystems exhibit an average temperature dependence similar to that of CH4 production derived from pure cultures of methanogens and anaerobic microbial communities. This average temperature dependence (0.96 electron volts (eV)), which corresponds to a 57-fold increase between 0 and 30°C, is considerably higher than previously observed for respiration (approximately 0.65 eV) and photosynthesis (approximately 0.3 eV). As a result, we show that both the emission of CH4 and the ratio of CH4 to CO2 emissions increase markedly with seasonal increases in temperature. Our findings suggest that global warming may have a large impact on the relative contributions of CO2 and CH4 to total greenhouse gas emissions from aquatic ecosystems, terrestrial wetlands and rice paddies.

Environmental controls over methane emissions from bromeliad phytotelmata: The role of phosphorus and nitrogen availability, temperature, and water content

AbstractTank bromeliads are common epiphytic plants throughout neotropical forests that store significant amounts of water in phytotelmata (tanks) formed by highly modified leafs. Methanogenic archaea in these tanks have recently been identified as a significant source of atmospheric methane. We address the effects of environmental drivers (temperature, tank water content, sodium phosphate [P], and urea [N] addition) on methane production in anaerobically incubated bromeliad slurry and emissions from intact bromeliad tanks in montane Ecuador. N addition ≥ 1 mg g−1 had a significantly positive effect on headspace methane concentrations in incubation jars while P addition did not affect methane production at any dosage (≤ 1 mg g−1). Tank bromeliads (Tillandsia complanata) cultivated in situ showed significantly increased effluxes of methane in response to the addition of 26 mg N addition per tank but not to lower dosage of N or any dosage of P (≤ 5.2 mg plant−1). There was no significant interaction between N and P addition. The brevity of the stimulatory effect of N addition on plant methane effluxes (1–2 days) points at N competition by other microorganisms or bromeliads. Methane efflux from plants closely followed within‐day temperature fluctuations over 24 h cycles, yet the dependency of temperature was not exponential as typical for terrestrial wetlands but instead linear. In simulated drought, methane emission from bromeliad tanks was maintained with minimum amounts of water and regained after a short lag phase of approximately 24 h. Our results suggest that methanogens in bromeliads are primarily limited by N and that direct effects of global change (increasing temperature and seasonality, remote fertilization) on bromeliad methane emissions are of moderate scale.

Planning management adapted to climate change effects in terrestrial wetlands and grasslands

Wetlands and grasslands are seriously affected by climate change. A main challenge for agriculture and nature conservation is, in parallel with mitigation, adaptation planning. We started a stakeholder dialogue to develop adaptive management of natural areas in the Körös-Maros National Park (SE Hungary). Impacts that affect terrestrial wetlands and grasslands and their agricultural use and are linked to climate change or other pressures were explored. Identification of stakeholders should be followed by providing information about climate change impacts on natural and human systems, a discussion of goals and objectives, a community based assessment, then elaboration of adapted strategies and measures. There is strong need to differentiate between stakeholders, and customise communication strategies for different groups. The benefits of stakeholder involvement are enhanced awareness, willingness to taking action, inclusion of local knowledge, information exchange among affected parties, identification of win-win-solutions for land users and nature conservation, and building trust in authorities.

Tidal Marsh Vegetation of China Camp, San Pablo Bay, California

China Camp (Marin County, California) preserves extensive relict stands of salt marsh vegetation developed on a prehistoric salt marsh platform with a complex sinuous tidal creek network. The low salt marsh along tidal creeks supports extensive native stands of Pacific cordgrass (Spartina foliosa). The outer salt marsh accreted following hydraulic gold mining sedimentation. It consists of a wave-scarped pickleweed-dominated (Sarcocornia pacifica) high salt marsh terrace with a broad fringing low marsh dominated by S. foliosa, including intermittent, variable stands of alkali-bulrush (Bolboschoenus maritimus). Most of the extensive prehistoric salt marsh plains within the tidal creek network also support mixed assemblages of S. pacifica, but high marsh zones along tidal creek banks support nearly continuous linear stands of gumplant (Grindelia stricta) and saltgrass (Distichlis spicata) with more diverse salt marsh forb assemblages. Salt pans with submerged wigeongrass (Ruppia maritima) are scarce, local, and small. The landward edge of the tidal marsh forms rare examples of ecotones with adjacent terrestrial vegetation, including those of alluvial valleys (riparian scrub and woodland, freshwater marsh, sedge-rush meadows) and hillslope grassland and oak woodland vegetation. Narrow high tidal marsh ecotones bordering terrestrial grasslands are locally dominated by creeping wildrye (Elymus triticoides) and Baltic rush (Juncus balticus), mostly on south-facing slopes. Brackish tidal marsh ecotones above ordinary high tides are associated with freshwater discharges from groundwater and surface flows. Brackish marsh ecotones support large clonal stands of sedge, bulrush, and rush vegetation (Carex praegracilis, C. barbarae, Bolboschoenus maritimus, Juncus phaeocephalus, Schoenoplectus acutus), intergrading with terrestrial freshwater wetlands and salt marsh. The terrestrial ecotone assemblages at China Camp are comparable with those of other prehistoric tidal marshes in the San Francisco Estuary, but China Camp lacks most native clonal perennial Asteraceae and halophytic annual forbs of the region’s remnant high tidal marsh ecotones. Few globally rare salt marsh plant populations have been reported from China Camp within the National Estuarine Research Reserve and State Park boundaries, but some species regionally uncommon in San Francisco Bay tidal marshes occur. To date, non-native tidal marsh plant invasions have been relatively minor and localized within China Camp.

Tidally Driven Export of Dissolved Organic Carbon, Total Mercury, and Methylmercury from a Mangrove-Dominated Estuary

The flux of dissolved organic carbon (DOC) from mangrove swamps accounts for 10% of the global terrestrial flux of DOC to coastal oceans. Recent findings of high concentrations of mercury (Hg) and methylmercury (MeHg) in mangroves, in conjunction with the common co-occurrence of DOC and Hg species, have raised concerns that mercury fluxes may also be large. We used a novel approach to estimate export of DOC, Hg, and MeHg to coastal waters from a mangrove-dominated estuary in Everglades National Park (Florida, USA). Using in situ measurements of fluorescent dissolved organic matter as a proxy for DOC, filtered total Hg, and filtered MeHg, we estimated the DOC yield to be 180 (±12.6) g C m–2 yr–1, which is in the range of previously reported values. Although Hg and MeHg yields from tidal mangrove swamps have not been previously measured, our estimated yields of Hg species (28 ± 4.5 μg total Hg m–2 yr–1 and 3.1 ± 0.4 μg methyl Hg m–2 yr–1) were five times greater than is typically reported for terrestrial wetlands. These results indicate that in addition to the well documented contributions of DOC, tidally driven export from mangroves represents a significant potential source of Hg and MeHg to nearby coastal waters.

Distance- versus patch-based movements of woodland caribou during spring dispersion in northern Quebec

Habitat selection studies are widespread in the scientific literature on woodland caribou (Rangifer tarandus caribou). Knowledge of habitat selection informs our understanding of caribou biology and life history requirements. Recent innovations in GPS telemetry have allowed us to track animal locations over space and time with remarkable accuracy, greatly enhancing our understanding of space use patterns and allowing us to more closely examine the role of scale and landscape heterogeneity in movements of woodland caribou. In conjunction, new spatial statistics and mechanistic approaches to resource selection analysis serve to reduce error in model selection and explain how landscape covariates influence caribou behaviour. With a view to maximizing functional connectivity between winter and summer ranges in managed landscapes of Northern Quebec, we first distinguished between biologically relevant seasonal phases in caribou movement by modeling distance moved over time using polynomial regression (Ferguson & Elkie, 2004a), identifying seasonal cut-off periods where the second derivative equals zero. We were interested in understanding how caribou per¬ ceive and respond to the heterogeneous landscape so we first tested for the presence of scalar activity in caribou move¬ ments. For each study animal (n=25) we fit a broken stick model to the ln frequency of movement rates recorded during spring dispersion, where appropriate establishing a unique rate criterion (rc) per animal (Johnson et al., 2002a) in order to differentiate between intrapatch and interpatch movements. Intrapatch movements are thought to represent forag¬ ing or resting phases whereas interpatch movements are associated with distance-based migratory activity; therefore we treated the two processes differently. We used kernel density estimates (plug-in method) for all points associated with patch-based movements during spring dispersion to define use-intensity levels for resource patches. Polytomous logistic regression was used to model patch resource selection by woodland caribou (Rittenhouse et al., 2008). In contrast, con¬ ditional logistic regression was used to model interpatch (i.e. distance-based) movements and a Step Selection Function (SSF) was built describing where a given animal was most likely to be found from one relocation to the next (Fortin et al., 2005b). Candidate models included covariates for road density, distance to forest cutovers, recent burns, terrestrial lichen abundance, coniferous forest, open wetlands, and distance to waterways. Results will be presented and application of models to connectivity analyses will be discussed.

Controls on the hydrogen isotopic composition of biogenic methane from high‐latitude terrestrial wetlands

To investigate the controls on the δD isotopic composition of biogenic CH4 in terrestrial wetlands, we collected a series of samples for δD‐H2O, δD‐CH4, δ13C‐CH4, and δ13C‐DIC (dissolved ΣCO2) along a N‐S transect across Alaska from 60°N to 70°N latitude from 7 to 15 August 2001. The δD‐H2O and δD‐CH4 values varied from −108‰ to −161‰ and from −308‰ to −394‰, respectively, from south to north and were significantly correlated, indicating the significant influence of the δD‐H2O on the δD of terrestrial CH4 collected along a latitudinal spatial gradient. Additionally, the apparent fractionation factors (α, αA–B = RA/RB, where R = 13C/12C or D/H) for H2O → CH4 (αD) and DIC → CH4 (αC) varied from 1.26 to 1.42 and from 1.035 to 1.084, respectively, and were inversely correlated. We conclude that while δD‐H2O is a critical factor controlling δD‐CH4 across latitudes, the CH4 production mechanism is also responsible for variation in the δD‐CH4. If the isotopic values of the precursors of methane, H2O, DIC, and organic matter are relatively constant, CH4 produced by acetate fermentation will be enriched in δ13C and depleted in δD relative to CH4 produced via the CO2 reduction pathway. Production mechanism variation will be particularly important in controlling variations in CH4 isotopic composition with depth. The strong dependence of δD‐CH4 on the δD of environmental H2O indicates that specific fields on plots of δD‐CH4 versus δ13C‐CH4 may not always accurately represent the isotopic composition of CH4 produced by CO2 reduction in northern wetlands. Because of this variation at high latitude, we assert that δD‐CH4 values cannot be associated with production mechanism in an absolute sense. The production mechanism effect is in addition to the effect of the δD‐H2O.

Beyond methane: Towards a theory for the Paleocene–Eocene Thermal Maximum

Extreme global warmth and an abrupt negative carbon isotope excursion during the Paleocene–Eocene Thermal Maximum (PETM) have been attributed to a massive release of methane hydrate from sediments on the continental slope [1]. However, the magnitude of the warming (5 to 6 °C [2],[3]) and rise in the depth of the CCD (>2 km; [4]) indicate that the size of the carbon addition was larger than can be accounted for by the methane hydrate hypothesis. Additional carbon sources associated with methane hydrate release (e.g. pore-water venting and turbidite oxidation) are also insufficient. We find that the oxidation of at least 5000 Gt C of organic carbon is the most likely explanation for the observed geochemical and climatic changes during the PETM, for which there are several potential mechanisms. Production of thermogenic CH4 and CO2 during contact metamorphism associated with the intrusion of a large igneous province into organic rich sediments [5] is capable of supplying large amounts of carbon, but is inconsistent with the lack of extensive carbon loss in metamorphosed sediments, as well as the abrupt onset and termination of carbon release during the PETM. A global conflagration of Paleocene peatlands [6] highlights a large terrestrial carbon source, but massive carbon release by fire seems unlikely as it would require that all peatlands burn at once and then for only 10 to 30 ky. In addition, this hypothesis requires an order of magnitude increase in the amount of carbon stored in peat. The isolation of a large epicontinental seaway by tectonic uplift associated with volcanism or continental collision, followed by desiccation and bacterial respiration of the aerated organic matter is another potential mechanism for the rapid release of large amounts of CO2. In addition to the oxidation of the underlying marine sediments, the desiccation of a major epicontinental seaway would remove a large source of moisture for the continental interior, resulting in the desiccation and bacterial oxidation of adjacent terrestrial wetlands.

Contribution of winter to the annual CH4 emission from a eutrophied boreal lake

The springtime methane (CH4) emission from a small, eutrophied boreal lake was assessed during the winter ice-cover by measurement of gas ebullition and CH4 accumulation in the water column in association with the development of oxygen depletion after ice formation. The winter CH4 production was estimated to result in a loss of 3.6-7.9 g CH4 m(-2) from the lake to the atmosphere during the short period of ice melt. This could account for 22-48% of the annual CH4 emission from the pelagic zone of the lake. The contribution of winter to the annual CH4 release can be similar or even higher in seasonally ice-covered northern aquatic ecosystems than in northern terrestrial wetlands, thus winter must be considered in any studies into the aquatic CH4 emissions. The trophic state and wintertime oxygen conditions, linked to the changes in land-use in the catchments and climate, are important factors controlling the springtime lake CH4 emissions.