Current Central American agricultural practices are environmentally and economically unsustainable, yet the ancient Maya who lived in the same region thrived for thousands of years. Archaeologists have attempted to understand the factors enabling the prolonged success and ultimate collapse of the Maya societies. Some have proposed that the karst seasonal wetlands, called bajos, that border many Maya sites in the region were an influential factor in the Maya's ability to flourish. For the past decade, researchers have used carbon isotope analyses to identify areas of ancient maize agriculture at Maya archaeological sites. In this study, we collected soil samples from bajos and upland areas at Tikal, one of the most prominent Maya sites, located in northern Guatemala, and analyzed the samples for evidence of past C4 vegetation. Our results confirm that bajos were utilized by the ancient Maya for long-term maize cultivation. Additionally, they suggest that modern agricultural methods in Guatemala that strategically utilize bajos may improve productivity and sustainability.

Inom Rååns avrinningsområde, som är beläget i kommunerna Helsingborg, Landskrona, Svalöv och Bjuv, har anläggning av våtmarker pågått sedan 1990-talet. De anlagda våtmarkerna syftar till att minska näringsförlusterna från omkringliggande jordbruksmarker till vattendrag och gynna den biologiska mångfalden. I denna studie har 28 anlagda våtmarker inom Rååns avrinningsområde studerats. Studien hade två övergripande syften varav det ena var att undersöka sambandet mellan sedimentackumulering och våtmarkernas utformning samt placering i landskapet. Det andra syftet var att undersöka våtmarkernas renoveringsbehov. Renoveringsbehov syftar på åtgärder som behöver utföras för att upprätthålla våtmarkernas ursprungliga funktion och utformning såsom flödesvägar, vegetation, djupprofil samt in- och utlopp. Studien baserades på observationer och mätningar som utfördes i oktober år 2020. Resultatet visade att sedimentackumuleringen varierade mellan 0,2–2,3 cm per år och att både utformnings- och placeringsfaktorer påverkade sedimentackumuleringen. Det uppskattade ursprungliga vattendjupet hade en positiv korrelation med sedimentackumulationen och sedimentdjupet blev högre med våtmarkens ålder. Uppgrundningen var högre närmare inloppet i fyra av sju långsmala våtmarker (Längd-breddförhållande, 𝐿 ∶ 𝐵 > 3). I de långsmala våtmarkerna fanns även en positiv korrelation mellan hydraulisk belastning (HL) och sedimentackumulering. I våtmarker med 𝐿: 𝐵 < 3 fanns en övre gräns där höga värden på HL istället hade en negativ påverkan på sedimentackumuleringen. Våtmarkens storlek i relation till avrinningsområdet hade ett negativt samband med sedimentackumuleringen. Att många faktorer påverkade sedimentackumulationen gjorde att uppgrundningen skedde olika snabbt i våtmarkerna. Därmed kunde inte ett exakt åldersintervall för urgrävning fastställas. Däremot kan urgrävning potentiellt begränsas till början av våtmarker i de fall våtmarken är långsmal med djuphåla vid inloppet. De undersökta våtmarkerna hade varierande grad av renoveringsbehov. Urgrävning bedöms vara den mest resurskrävande åtgärden. Det är dock en nödvändig åtgärd om våtmarkerna ska fortsätta fungera som näringsfällor. Andra renoveringsbehov innefattade exempelvis enklare skötsel av vegetation, reparation av teknisk utrustning såsom rör och brunnar samt uppföljning av avtal med markägare för att se till att våtmarkerna förvaltas på sådant sätt att deras miljönytta gynnas. / Wetlands have been constructed within the catchment area of Råån since the 1990s. Råån is a river flowing through the municipalities Helsingborg, Landskrona, Svalöv, and Bjuv. The constructed wetlands aim to reduce nutrient leakage from surrounding agricultural land and increase biodiversity. In this study 28 constructed wetlands were studied with two aims: (i) to investigate the relationship between sediment accumulation in wetlands and wetland design and location in the landscape and (ii) investigate maintenance needs of the wetlands. Maintenance needs involve taking efforts to restore flow paths, depth profile, vegetation, and inlet and outlet to return the original function and design of the wetland. The study is based on observations and measurements carried out in October 2020. The results showed that sediment accumulation varied between 0.2–2.3 cm per year and that both wetland design and location affected sediment accumulation. Estimated original water depth had a positive correlation with sediment accumulation and sediment depth had a positive correlation with wetland age. The level of shoaling was higher closer to the inlet in four of seven long narrow wetlands (length- width ratio, L: W, > 3). In the long narrow wetlands, there was also a positive correlation between HL and sediment accumulation. However, in shorter and wider wetlands (L: W <3), there was an upper limit where high values of HL instead had a negative effect on sediment accumulation. Wetland area in relation to catchment area had a negative correlation with sediment accumulation. Shoaling rate is different in the wetlands since sediment accumulation is affected by many parameters. Thus, an exact time interval for excavation could not be determined. However, excavation can potentially be limited to the inlet of the wetlands if the wetland is long and narrow with a deep area near the inlet. The result showed that the wetlands had varying degrees of maintenance needs. Excavation is considered to be the most resource-intensive measure. However, excavation is necessary to maintain the function of the wetlands. Other maintenance needs include maintenance of vegetation, repair of technical equipment, and extension and enforcement of contracts with landowners to ensure that the wetlands are managed in such a way that the environmental function of the wetlands are favored.

Storing almost a third of the global soil carbon pool, wetlands are an essential component of the carbon cycle, and carbon-rich peat soil accumulates when carbon input through primary productivity exceeds output through decomposition. However, woody shrub encroachment in herbaceous wetlands can alter soil carbon processes, potentially diminishing stored carbon. To examine the effects of shrub encroachment on soil carbon, I compared soil carbon input through litterfall and fine root production, output through decomposition, and below-canopy microclimate conditions between Carolina willow shrub (Salix caroliniana) and herbaceous sawgrass (Cladium jamaicense) in the Blue Cypress Marsh Conservation Area (BCMCA), FL. To assess the level of production and its response to water level, I compared aboveground green biomass by measuring normalized difference vegetation index (NDVI) and photosynthetic stress by measuring photochemical reflectance index (PRI) between sawgrass and willow. I collected willow litterfall using litter traps and measured sawgrass and willow fine root production with fine root ingrowth bags. Litter decomposition was measured with decomposition bags deployed using a reciprocal litter placement design at BCMCA and incubated in a greenhouse to examine the effects of char and water level on decomposition. Above and belowground microclimate conditions were measured using sensors installed within sawgrass and willow canopies. Despite experiencing more photosynthetic stress, willow produced more green biomass than sawgrass. However, willow produced fewer fine roots than sawgrass and these roots were deeper within the soil. Willow litter decomposed faster even though sawgrass decomposition increased under drier conditions. Compared to the sawgrass canopy, the willow canopy had greater light availability, lower evaporative demand plus warmer and drier soils; however, litter decomposition did not differ between the canopies. These results suggest that willow encroachment can reduce the amount and alter the distribution of carbon within an herbaceous wetland, likely resulting in a net loss of soil carbon. Although willow encroachment may increase aboveground biomass carbon stocks, these stocks will likely be offset by a loss of soil carbon due to reduced fine root production and increased decomposition. Therefore, the transition from herbaceous wetland to shrub wetland will likely result in a loss of stored soil carbon. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

>Magister Scientiae - MSc / Wetlands are unique ecosystems that are acknowledged among the world’s most productive and valuable ecosystems. They are recognized as being essential to sustainable development and human welfare due to their unique environmental and socio-economic value. These highly productive ecosystems provide functions such as recycling of nutrients, watershed protection and flood control as well as grazing resources. Wetlands provide the basis for human livelihoods in Africa through ecosystem services. However, these ecosystems are affected by internal and external factors within and outside their catchments, hence the importance of monitoring those changes around these wetlands.

Wetlands are important elements of watersheds that influence water storage, surface water runoff, groundwater recharge/discharge processes, and evapotranspiration. To understand the cumulative effect wetlands have on a watershed, one must have a good understanding of the water-level fluctuations and the storage characteristics associated with multiple wetlands across a region. An improved analytical method is presented to describe the storage characteristics of wetlands in the absence of detailed hydrologic and bathymetric data. Also, a probabilistic approach based on frequency analysis is developed to provide insight into surface and groundwater interactions associated with isolated wetlands. The results of the work include: 1) a power-function model based on a single fitting parameter and two physically based parameters was developed and used to represent the storage of singular or multiple wetlands and lakes with acceptable error, 2) a novel hydrologic characterization applied to 56 wetlands in west-central Florida provided new information about wetland hydroperiods which indicated standing water was present in the wetlands 62% of the time and these wetlands were groundwater recharge zones 59% of the time over the seven year study, 3) the smallest extreme value probability distribution function was identified as the best-fit model to represent the water levels of five wetland categories in west-central Florida, 4) representative probability models were developed and used to predict the water levels of specific wetland categories, averaging less than 10% error between the predicted and recorded water levels, and 5) last, based on this probability analysis, the various wetland categories were shown to exhibit similar means, extremes and ranges in water-level behavior but unique slopes in frequency distributions, a here to for new finding. These results suggest that wetland types may best be differentiated by the regular variability in water levels, not by the mean and/or extreme water levels. The methods and analytical techniques presented in this dissertation can be used to help understand and quantify wetland hydrology in different climatological or anthropogenic stress conditions. Also, the methods explored in this study can be used to develop more accurate and representative hydrologic simulation models.

Tidal freshwater wetland soils contain large amounts of organic carbon, some of which is mineralized to carbon dioxide (CO2) and methane (CH4) by a diverse consortium of anaerobic microorganisms that includes fermenters, syntrophs, and methanogens (MG). These microbial groups are tightly linked and often rely on cooperative interspecies metabolisms (i.e., syntrophy) to survive. Environmental perturbations can disrupt these interactions and thus alter the rates and pathways of carbon cycling. One environmental change of particular concern in coastal wetlands is sea level rise, which can result in increased episodic saltwater intrusion events into these ecosystems. These events cause an influx of sulfate (SO4-2) to the soils and may stimulate sulfate-reducing bacteria (SRB), which can directly compete with syntrophs for energy sources (e.g., fermentation products such as butyrate). Since syntroph metabolism generates byproducts that serve as the energy source for many MG, this competition can have indirect negative effects on methanogenesis. In addition, SRB can directly compete with MG for these byproducts, particularly formate, H2, and/or acetate. The goal of this study was to understand how both MG and syntroph-MG consortia respond to and recover from SRB competition during an episodic saltwater intrusion event. To achieve this, microcosms containing soil slurry from a freshwater wetland were subjected to simulated saltwater intrusion, and metabolic inhibitors were used to isolate the activity of the various functional groups. This study focused on the breakdown of butyrate, which is a key energy source in syntroph‑MG consortia metabolisms. The observed changes in butyrate breakdown rates and byproduct accumulation during butyrate degradation assays confirmed that butyrate breakdown was mediated through syntroph-MG consortia, and that formate, rather than H2, was likely used as an electron carrier during syntrophic activity. Additions of SO4‑2 (as Na2SO4) to the freshwater microcosms stimulated SRB activity and shifted the MG community to favor acetoclastic members. These changes were accompanied by a 24% increase in CO2 production and an 80% decrease in CH4 production. Interestingly, when NaCl was added to achieve similar ionic strength, CH4 production decreased by ~32%, suggesting SRB competition is not the only factor affecting methanogenesis. Butyrate degradation rates demonstrated that while SRB were strong competitors for butyrate, concurrent syntrophic metabolism was possible. Further, data show that SRB were poor competitors for acetate, which could explain the increase in acetoclastic MG. Following removal of SRB competition, CH4 production recovered but only by ~50% after 28 days, which suggests that some MG communities in tidal freshwater wetlands may not be resilient to saltwater intrusion events. Over this same time, rates of syntrophic butyrate breakdown largely recovered, but butyrate breakdown resulted in the production of less CH4 and acetate and more CO2 and formate, indicating saltwater intrusion events may lead to persistent changes in the byproducts and pathways of carbon breakdown in tidal freshwater wetlands.

Tidal freshwater wetlands provide valuable ecosystem services such as nutrient cycling, coastal flood control, and reproductive habitat for early life stages of economically and ecologically important fishes. The nutrient rich environments that tidal freshwater wetlands occur in support high levels of primary productivity of phytoplankton and vegetation that provide essential reproductive habitat for anadromous clupeid fishes (Alosa spp., Brevoortia tyrannus) in Chesapeake Bay tributaries. Seasonal retention of clupeid eggs and larvae within tidal freshwater habitats may enhance early growth, survival, and year class strength. The primary goal of the present study was to characterize the relative importance of tidal freshwater wetlands to the early life history stages of anadromous, migratory, and resident clupeid fishes in the lower James River. From 2014-2018, conical tow nets were used to collect ichthyoplankton samples from representative locations within the tidal freshwater marsh-creek complex of Curles Neck Creek, Virginia during the period of February through May. Boat electrofishing was used to sample juvenile target clupeids within the marsh-creek complex during March through November 2014-2018. A strong positive correlation between larval and juvenile Blueback Herring and Atlantic Menhaden, supported the hypothesis of seasonal in-system retention. This was the first published study to describe spatial and temporal patterns of occurrence of clupeid fishes with varying life history strategies in a tidal freshwater marsh and highlighted the importance of tidal freshwater marshes as nursery habitat.

There is an extended concern for how to quantify the fluxes of greenhouse gasses (GHG) and how they are related to climate change and land use. Efforts have already been done, mostly regarding carbon (C) compounds, but there is still much to be done especially to understand regulating factors and interactions with the Nitrogen cycle. NitroEurope is a large project for the integrated European research into the N cycle. This study shares its aim, to improve the understanding the physics involved in the fluxes of the reactive N (Nr). More specifically, the patterns of some physical and biological processes related to Nr have been studied for two wetlands, one in the proximity of Edinburgh and the other in the North of Finland.   A common model setup has been used for both of them, since they are both peat soils. The differences applied to achieve appropriate performances give insights of their nature. The presence of snow is a major factor that governs the behavior of the site in Finland. The scaling of existing models for the estimation of heat transfer in the soil of the Scottish site is also critical, such as its groundwater level. The sites represent different climatic conditions, but for CO2 fluxes they showed similar behavior and response to governing meteorological conditions. Using the GLUE method in combination with a process oriented ecosystem model, some further insights have been gained for the regulation and control of greenhouse gas emissions from the two sites.

Wetlands are considered a last line of defence against poor water quality. Despite the natural capabilities of wetlands to remove a variety of contaminants from surface water, the track record for wetland conservation leaves much to be desired. In the northern parts of the City of Tshwane, 84% of wetlands have been degraded. When viewed against the poor bacteriological quality of river water in the study area, the lack of wetland conservation efforts is of particular concern. Given the large number of wetlands in the Tshwane area in need of rehabilitation, this study aimed to devise a methodology to prioritise these wetlands for rehabilitation. No blueprint for such a prioritisation process exists, as studies are adapted to take into account the availability of data and the unique requirements of the study area. The methodology for this study is based on the prioritisation of a specific river basin, based on expected maximum faecal bacterial load originating from various sources of pollution. Four river basins were compared with each other in a series of screening processes. Screening was done on a landscape level using a Geographic Information System (GIS) to generate various composite layers as part of the screening process. The screening processes relied on the application of several weighted criteria. Weights for criteria are based on scientific literature. Weights are also allocated in line with the “worst case scenario”, as the study is in essence an assessment of the various pollution sources and their maximum possible contribution to deteriorating surface water quality. A Simple Additive Weighting technique was used to assess the total pollution loads and total numbers of users at risk from contaminated surface water in each of the river basins. It is important to note that the objective is to only rate the pollution sources, whilst exact pollution loads were not calculated. Diffuse, areal and point sources of pollution were rated using the estimated contributions to faecal coliform loads. The river basin with the highest score was selected for the selection of candidate wetlands for rehabilitation purposes. The Apies River Basin scored highest for most of the criteria, with the exception of the number of households at risk from contaminated surface water. Despite the 0.60 weight allocated to households at risk, the extent of pollution sources in this river basin allowed it to be singled out as the basin in which a wetland for rehabilitation is most urgent in order to attenuate bacterial load. Two wetlands were short listed, based on their high need for rehabilitation, their hydrogeomorphic location (valley bottom with a channel), and given that they are larger than 1ha in size and within a minimum distance from the households at risk. Site level assessments are required for a final selection between the two, taking into account the nature of the current disturbances, the possibility of risk due to back-flooding, the projected costs associated with rehabilitation, the nature of the vegetation associated with the wetlands and the general conservation value of each of the wetlands.

Wetlands are crucial for respecting the planetary boundaries and reaching the United Nations Sustainable Development Goals, but wetland areas in Sweden has decreased significantly. The need for restoration, stronger protection, and land-sharing opportunities requires exploration of the subsistence practices involving wetlands in the past. This thesis investigates the sustainability potential of catchwork water-meadows. An integrated landscape analysis method (ILA) using spatial targeting was designed and tested in QGIS with a range of supporting data aiming to locate previously unknown and unprotected catchwork water-meadows in Jämtland County, that could be potential restoration targets. A literature search was conducted to gather general information on catchwork water-meadows impact on climate change, biogeochemical flows, threatened species, to re-imagine social aspects, and to find morphological characteristics that could be compared to remote sensing data. The literature search revealed varieties in construction, development of theories on nutrient sources over time, a species composition with 19 species and genera present on the Red List of threatened species. It is found that novel construction of catchwork water-meadows likely increase GHG release, but restoration projects on already modified land could possibly decrease GHG output depending on the no-action scenario and use of the produced biomass. There are indications that nutrient removal is possible but experimentation and more scientific measurements are needed. Social benefits include: resilience from economic diversification and being organised as a common, production of plant biomass for various uses, community building, and knowledge production. The ILA consisted of three stages, 1. spatial targeting, 2. site interpretation, and 3. evaluation. Three potential sites were located. Indications for and against identifying these as catchwork water-meadow are presented, and refinement of the ILA to reach definite verdicts are suggested.