No description available.

The waste management and recycling company, Söderhalls Renhållningsverk (SÖRAB) have constructed a surface flow wetland in order to treat surface runoff from the waste management site, Löt. The contaminated water passes several treatment steps until it reaches the wetland and a subsequent soil infiltration step. It is suspected that the flow path of the water through the wetland is short-circuited which may result in a reduced treatment efficiency. The current discharge concentrations of the chemical compounds tested for do not exceed the allowed discharge limits. However, it is of interest to keep the discharge concentrations as low as possible to protect sensitive areas and water bodies downstream. The aim of the thesis was therefore to investigate the flow pattern of the wetland and suggest measures which potentially could improve the treatment efficiency. The flow pattern was modelled numerically in a Physio-Mathematical model developed by Wörman and Kjellin (2020). The current flow pattern was modelled, followed by several simulation runs where the controlling factors of the flow were changed one by one. The validity of the modelling result is uncertain and should therefore be confirmed or rejected by conducting a tracer test prior to implementing any changes in the wetland design. The modelling results indicate the presence of a main flow path passing through the narrower section of the permeable embankment (intersecting the northern and southern part of the wetland, see Fig. 3). The results further indicate that the permeable embankment, the bottom topography and the vegetation distribution were the three major factors controlling the flow pattern within the wetland. Recommended improvements would therefore be to first conduct a tracer test to make sure that any changes implemented are based on the true current flow pattern. The embankment and the vegetation distribution seem to be the main causes of non-idealities in the flow but at the same time probably also have positive effects on the treatment efficiency (since they provide filtration and surface areas where microorganisms can attach to perform their treatment). One solution to reduce the non- idealities in the flow could therefore be to adjust the embankment to be equally wide and deep across the wetland. Furthermore, the bottom topography around the embankment could be adjusted so that the shift in bottom elevation is equal around it. This would probably aid in hindering the development of preferential flow paths through the embankment. Finally, the vegetation distribution could be made uniform. (It should also be noted that a uniform vegetation distribution would require adjustment of the water depth to be below 1,5 m to allow an equal establishment of vegetation). / Avfallshanterings- och återvinningsföretaget Söderhalls Renhållningsverk AB (SÖRAB) har anlagt en våtmark vid Löts avfallsanläggning, ca 35 km norr om Stockholm. Våtmarken utgör det näst sista reningssteget i reningsprocessen av lak- och processvatten från avfallsanläggningen. Riktvärdena för utsläppshalterna överskrids inte men det är önskvärt för SÖRAB att åstadkomma så låga utsläppsvärden som möjligt för att minimera påverkan på känsliga områden och vattendrag nedströms. SÖRAB misstänker dock att preferentiella flödesvägar kan förekomma där vattnet passerar alltför fort genom våtmarken. Detta resulterar ofta i en lägre reningseffektivitet då föroreningarna som är lösta i vattnet får en kortare kontakttid med de naturliga reningsmekanismerna som förekommer i våtmarken. Syftet med det här arbetet var därför att undersöka strömningen i våtmarken och identifiera vattnets flödesvägar med hjälp av en numerisk modell utvecklad av Wörman och Kjellin (2020). Strömningen i våtmarker styrs av en energigradient där flödet går från en punkt i ett vattendrag med högt energiinnehåll till en punkt med lågt energiinnehåll. Enligt principen om energins bevarande omvandlas energin mellan kinetisk, potentiell, tryckenergi och värmeenergi. Ändringen i energiinnehåll beror i sin tur på verkan av externa krafter (gravitationskraften, hydrostatiska tryckkrafter, friktionskrafter, kontraktions- och expansionskrafter och skjuvkrafter från vind. Dessa krafter verkar vid förändringar i bottentopografin, vattendjupet, ytmotståndet (vid våtmarkens botten och väggar), våtmarkens geometri samt där vattenytan är exponerad för vind. Dessa faktorer orsakar utvecklandet av skjuvkrafter i flödet som i sin tur orsakar utvecklandet av hastighetsprofiler och omblandning. Bildandet av hastighetsprofiler och omblandning av vattnet gör att olika vätskeelement eller föroreningar stannar i våtmarken olika lång tid då de rör sig olika fort. För att åstadkomma en så hög reningsgrad som möjligt är det därför önskvärt att hela våtmarkens volym nyttjas till samma grad och att samtliga vätskeelement rör sig med samma hastighet genom våtmarken vilket även kallas för en ideal flödesregim (där ingen omblandning i flödesriktningen förekommer). Då utvecklandet av skjuvkrafter i flödet utgör den grundläggande orsaken till avvikelser från en ideal flödesregim är det önskvärt att minimera dessa. De styrande faktorerna som orsakade utvecklandet av skjuvkrafter i flödet var som nämndes ovan: variationer i våtmarkens bottentopografi och vattendjup, våtmarkens geometri (som kan orsaka isolerade vattenvolymer), ytmotståndet (som bl.a. beror på distributionen av vegetation), vind, samt in- och utflödeshastigeter. Våtmarken undersöktes genom inmätning och lodning som sedan låg till grund för en konceptuell modell av systemet. Den konceptuella modellen utgjorde sedan en grund för att modellera våtmarken numeriskt. I den konceptuella modellen ingick identifiering och definition av systemgränser samt randvillkor, att definiera bottentopografin samt att dela in våtmarken i delområden med homogent flödesmotstånd. Systemgränser och randvillkor identifierades baserat på en vattenbalans. Med hjälp av vattenbalansen kunde relevanta komponenter att inkludera som randvillkor identifieras. Randvillkorens värden bestämdes genom mätningar av den hydrauliska potentialen med hjälp av en GNSS-mottagare (där GNSS står för Global Navigation Satellite System och mottagaren nyttjar satelliter för att bestämma höjd och position i en geografisk punkt) samt från erhållna mätvärden från SÖRAB av in- och utflöden som pumpas in och ut ur våtmarken. Då bottentopografin var okänd bestämdes den genom att vattendjupet mättes, interpolerades och subtraherades från en referensnivå. Vattendjupet mättes genom lodning och mätpunkterna interpolerades sedan i det geografiska informationsverktyget ArcMap för att erhålla ett heltäckande lager av mätvärden över vattendjupet. Därefter kunde vattendjupet subtraheras från vattenytans medelhöjd över havet vilket var 38,1 m och ett heltäckande lager över bottentopografin kunde erhållas. Flödesmotståndet beräknades enligt ekvation 16 (se avsnitt 2.1.) och våtmarken delades in i homogena delområden baserat på förekomsten av vegetation och om strömningen skedde genom ett poröst medium eller öppet vatten. Den numeriska modelleringen genomfördes genom att först modellera den nuvarande strömningen med och utan ett rör som går genom den genomsläppliga vallen. Därefter ändrades de styrande faktorerna för flödet en i taget för att kunna utvärdera vilken effekt varje faktor hade på strömningen i våtmarken för att åstadkomma en ideal flödesregim. Följande simuleringar genomfördes: (1) Bottentopografin gjordes jämn med ett vattendjup på 0,5 respektive 1,0 m, (2) inloppszonen gjordes längre för att undvika skapandet av isolerade vattenvolymer längs ytterkanterna, (3) vegetationens distribution gjordes homogen, (4) den genomsläppliga vallen justerades. Pålitligheten i resultatet från den numeriska modelleringen är osäker. Därför skulle ett spårämnesförsök behöva genomföras för att undersöka huruvida resultatet från modelleringen är tillförlitligt eller inte. Enligt modelleringsresultatet förekom en tydlig flödesväg som passerade genom den smalare delen av vallen. Modelleringen indikerade vidare att de kontrollerande faktorerna som styrde flödet i våtmarken framförallt utgjordes av distributionen av vegetation samt den genomsläppliga vallen tillsammans med omgivande bottentopografi. Det rekommenderas därför att modelleringsresultatets validitet först undersöks med ett spårämnesförsök innan några åtgärder vidtas. Möjliga förbättringsåtgärder som skulle kunna införas därefter för att sträva mot ett idealt flöde skulle kunna vara att justera den genomsläppliga vallen till att ha en lika stor tjocklek och ett lika stort djup överallt samt att justera bottentopografin runt vallen så att den förändras lika mycket runt vallen. Detta för att skapa förutsättningar för att undvika preferentiella flödesvägar genom den. En jämn fördelning av vegetation (och justering av vattendjupet till att understiga 1,5 m som tillåter kolonisering av växter) att störningar i flödet minimeras.

Centralized wastewater treatment systems need substantial funds besides high-cost operation and maintenance programs, which could be considered unsuitable for low-income developing countries. As a solution, it becomes the trend towards on-site wastewater treatment systems (OWTs) due to its cost-effectiveness and flexibility of implementation and management. However, the keenness to implement these systems appropriately and monitor them continually is crucial to ensure that they do not impact the surrounding environment and human health. Constructed wetland is one of the on-site wastewater treatment systems. These systems are comparatively affordable alternative technology, and adequate systems for small communities, rural, and hilly areas. In the present study, two constructed wetlands as on-site wastewater treatment systems in Sakib - Jerash Governorate, Jordan, were investigated regarding systems performance, social acceptance, and cost-benefit analysis. The first system is a vertical flow constructed wetland (VCW) that has been operating since January 2020. The second system is a recirculation vertical flow constructed wetland (RVCW) that has been in operation since July 2015. The checking of the theoretical design parameter and the actual loading conditions of the septic tanks and wetlands in both systems showed that both implemented septic tanks and the wetlands are adequate and appropriate for the design goals. The wetlands’ treatment performance showed sufficient capability in organic matter removal efficiencies: Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD), and Total Suspended Solids (TSS) removal efficiency. For pathogens: Total Coliform (TC) and Escherichia coli (E.coli), even though the removal efficiency was high, the effluents' values exceeded the local directive. Concerning nutrients removal, both systems showed low nitrogen and phosphorus removal efficiencies. Some suggestions and recommendations were proposed for improving nutrients removal and pathogen removal efficiencies. These recommendations were in desludging the septic tanks, replacing the filtering media, introduce plantation or add other carbon sources to the system, and using an additional aerobic filtration unit in the wetlands’ outlets. The study showed that the Jordanian society's nonacceptance of the on-site wastewater treatment systems could be handled through full transparency, educational workshops, and public participation. The latter contributed an increased sense of ownership robustly and increased concern of responsibilities on the operational and maintenance matters. Regarding the cost-benefit analysis, the study results demonstrated that the implementation of a constructed wetland as an on-site wastewater treatment system could be a beneficial and valuable alternative for clusters in rural areas and even in newly urbanized plans. The promising method for the treated wastewater's disinfection using clay minerals needs further investigation to determine the optimum clay mineral concentration on treatment and the needed time for exposure. / För att täcka centraliserade avloppsreningssystems drift och underhåll är det kapitalinsättningen av stor betydelse, förutom högkostnadsprogram, något som anses vara olämpligt för låginkomstländer. In-situ avloppsreningssystem verkar vara en lovande lösning till detta. För att dock säkerställa att dessa ej belastar den omgivande miljö och fungerar som det skall i förbehåll att dessa ständigt övervakas. Konstruerade våtmarker är en typ av in-situ vattenreningsteknik. Dessa system är lämpliga för småstäder, bergiga och tätortsområden. Dessa system är kostnadseffektiva och flexibla vad dess implementering och hantering anbelangar. Två dylika system är i fokus av denna studie, nämligen två konstruerade våtmarker i Sakib - Jerash i Jordanien och i synnerhet utforskas dess prestanda, social acceptans i och dessutom utfördes en nyttokostnadsanalys. Båda våtmarkerna i denna rapport har konstruerats med ett vertikalt markflöde och är i drift sedan januari 2020 och juli 2015 respektive. Dessa två system ger goda reduktioner med avseende på biokemiskt syrebehov och kemiskt syrebehov (BOD, COD), totalt suspenderat material (TSS), och effektivitet rörande patogen borttagning (TC och E. coli). Även om patogen borttagningseffektivitet i sig var hög förblev patogenhalt hög i det lokala direktivs avseende; de lokala förutsättningarna, nämligen designparameter och belastningsförhållanden, tillåter dock uppbyggande och drift av dessa två systemen som i fokus i detta studium. Beträffande borttagning av näringsämnen visade det sig att båda systemen har låg kväve- och fosforborttagningseffektivitet. Vissa förslag och rekommendationer föreslogs för att förbättra näringsämnen samt systemens effektivitet vad gäller patogenborttagning; i synnerhet dessa förslag beträffar pumpa ut slammet ur septiktanken, utbyte och backspolning av vattenfiltermedia, vattenväxterinförande eller tillägg av en extern kolkälla samt användning av en ytterligare aerobfiltreringsenhet vid utlopp. Det visade sig att det jordanska samhälle sätter käppar i hjulet vad gäller implementering av dessa våtmarker emedan dess förfarande är oacceptabelt. Dylika problem kan överbryggas genom full insyn, föredrag och workshops samt allmänhetens deltagande. Det sistnämnda gav upphov till en ökad känsla av äganderätt robust, något som ledde till ökat intresse för ansvar i drifts- och underhållsfrågor. Vad nyttokostnadsanalysen anbelangar visade det sig att implementering av ett dylikt system skulle vara fördelaktigt och värdefullt som alternativ för kluster på tätorts- och landsbygdsområden. Avloppsvattenbehandlingen med lermineraler verkar hittills vara en lovande metod vid betraktande av tidigare studier. Det behöver dock göras ytterligare undersökningar för avloppsvattenbehandlingen med lermineraler vid bestämmande av den optimala lermineral koncentration och dess exponeringstid.

<p>Coastal wetlands are hydrologically connected to their watershed and the lake. Water levels in Georgian Bay have been at a sustained low for thirteen years and thus connectivity of wetlands to the lake is being threatened as water levels decline. Decreased connectivity has likely caused changes in ecological and chemical characteristics. Future climate change models predict further water declines and potentially increasing the number of wetlands that will be hydrologically disconnected. The over-arching goal of this thesis is to investigate the role of connectivity between the lake and coastal marshes in eastern Georgian Bay on the amount of potential fish habitat, water chemistry and larval amphibian habitat.</p> <p>Bathymetric information is needed in order to estimate fish habitat and two approaches were utilized in order to collect these data. A site-specific method completed in 2009 used an intensive field survey in seven wetlands to create a digital elevation model and calculated the amount of fish habitat at 10 cm increments. A second, regional method, selected 103 sites by using a stratified random sample in 18 quaternary watersheds. In both methods, changes in water levels between 173 and 176 m asl resulted in the most drastic loss of habitat. Approximately 24% of the current fish habitat has already been lost due to low water levels.</p> <p>Water chemistry in coastal marshes is influenced by hydrologic connection. In the summers of 2010 and 2011, 35 coastal marshes were sampled, 17 of which had been impounded and disconnected by a beaver dam. Beaver-impounded marshes resulted in significantly lower pH, conductivity, dissolved oxygen and sulphate concentrations, but had significantly higher soluble reactive phosphors concentrations. These conditions are indicative of the lack of connection and reduced mixing with lake water. This altered habitat was shown to support breeding area for 7 species of amphibians, the most common being green frogs and the least common being American Toads and chorus frogs.</p> / Master of Science (MSc)

Monitoring and maintaining the health of coastal wetlands is a global concern. The greatest threat to coastal wetlands in the Great Lakes Basin are anthropogenic removal and enrichment. The coastal wetlands in Georgian Bay are relatively undisturbed by humans, but face disturbance caused by reduced annual water-level fluctuations. Since these wetlands are critical habitat for many fish, bird, amphibian, and reptile species, many efforts to accurately monitor and maintain their health have been put into place. Recently, these wetlands have been experiencing an abrupt (~1 m) transition to higher water levels, following 14 years of sustained lows, which allowed trees and shrubs to invade the meadow vegetation zone. This sustained water-level pattern has never occurred in this region before, offering the unique opportunity to study wetlands undergoing a transition, where areas of 10+ years of upland plant species growth was inundated and became part of the wetland habitat. This thesis first investigates how this change in water level affects the distribution of meadow, emergent, floating, and submerged vegetation both in physical space and area. The second chapter of this thesis presents long-term water quality, macrophyte, and fish community monitoring using ecological indices. Water quality and macrophyte indices are robust enough to monitor wetlands undergoing a transition; however, issues arise in the calculation of the wetland fish index, as the changes in macrophyte distribution described in Chapter 1 impact the ability to replicate community sampling using fyke nets. The research done throughout this thesis is highly beneficial in adding to the limited knowledge of key factors impacting macrophyte community shifting. This work also identifies water-level scenarios where managers must adjust sampling protocols to succeed in effectively sampling wetland fish communities. / Thesis / Master of Science (MSc) / The coastal wetlands in the Georgian Bay area are primarily threatened by human development and the removal of annual water-level fluctuations. From 1999-2013, the water level decreased and remained low. In 2014, the water level rose about 1 m, causing flooding of grass and trees that had grown in the meadow zone during the 14 years when the water level was low. The first goal of this thesis is to explain how and why all wetland plants are relocating during this period. The second goal is to make sure that common indicators of wetland health (water quality, plants, and fish) can still be used during a time when flooding of grasses and trees was occurring in wetlands. The findings in this thesis contribute to the ability to predict and understand how the plants will shift within a wetland during a time of flooding, as well as informing managers on appropriate sampling protocols.

No description available.

Reptile populations are in decline worldwide, with turtle species showing some of the largest drops in population. The bog turtle (Glyptemys muhlenbergii) is considered one of the rarest North American turtle species, and this rarity is made more severe by anthropogenic factors. The wetland habitats that are used by bog turtles contain seepage areas and soil saturation that are characteristic of specific types of wetlands, suggesting that bog turtle rarity may in part be attributed to narrow habitat requirements. In this dissertation, I have sought to spatially and temporally characterize the hydrology and soils of wetlands that are used by bog turtles in an effort to determine how these factors are related to the species' habitat requirements, movement, and activity. In Chapter 1, I evaluated hydrology over a continuous 28-month period using shallow groundwater wells in six wetland fens known to be used by bog turtles for breeding and six apparently similar, but unused, wetlands. The saturated surface area near wells was measured and correlated with depth to the water table. Overall, water tables remained high, with mean monthly depth to the water table for all 12 wetlands remaining > -35 cm (depth below surface datum is negative). Bog turtle breeding wetlands had significantly higher mean water tables and surface saturation than wetlands where no turtles were encountered, particularly during and after the two-year drought occurring in 2007 and 2008. Findings of Chapter 1 suggest that relatively small differences in water table hydrology can affect bog turtle biology and use of wetlands. Bog turtles access soils and move through them to thermoregulate, find cover, and hibernate. Most wetlands used by bog turtles are also grazed by livestock that can modify soil strength. In Chapter 2, I identified dominant soil series and sampled surface soils from wetlands used by bog turtles and similar, but unused, wetlands. Samples were analyzed for organic carbon content and particle size distribution. Organic carbon content was greater in areas that were always wet (10%) than temporarily wet areas (5%). Somewhat higher organic carbon contents were present in wetlands that were used by bog turtles (8.8%) than wetlands where turtles were never encountered (5.7%). Soil textures were sandy loams and silt loams on all the study wetlands. Based on measurements of soil strength made with a static cone penetrometer, bog turtles selected wetland locations with low-strength soils. The mean and variability of soil strength were no different between grazed and ungrazed areas. The physical qualities of surface soils in bog turtle wetlands are dependent on consistently high water tables. In Chapter 3, I described three field studies in which I deployed temperature loggers to measure and contrast ambient air and soil temperatures to turtle carapace temperatures during activity and hibernation. I used temperature signatures to evaluate the timing and cues of spring emergence and to recognize thermoregulatory activities during periods of turtle activity. Mean daily turtle temperatures (n=16 turtles) during the coldest portion of two winters ranged between 1.3°C and 6.1°C, with one turtle experiencing 14 continuous days at temperatures between -1°C and 0°C when ambient temperatures dipped below -10°C. Water tables remained within 10 cm below the soil surface throughout the winter, preventing freezing temperatures for shallow hibernating turtles. Soil temperatures at 10 cm depth were a primary cue for spring emergence. Daily mean summer turtle temperature (n=8) was 20.8°C. My findings indicated that the presence of water near the surface and the ability for turtles to submerge themselves in mud are important for thermoregulation. In Chapter 4, I used radio telemetry to evaluate bog turtle activity (distance moved / hour), linear range, and the pathways used for dispersal. I also investigated bog turtle activity during sampling periods with either wet or dry hydrology. Mixed model analysis indicated that turtles were much less active between 18:30 and 09:30 relative to the daytime and that turtles were most active during times when hydrology was categorized as wet during 2008 when moderate to severe drought was the dominant condition. Sex was not a factor in turtle activity. Bog turtle paths during large movements (≥ 80 m) were mostly contained to areas within 80 m of USGS 7.5â quadrangle mapped streams. Turtles made large movements more frequently during dry conditions. Results suggested that drying conditions can stimulate bog turtles to either remain inactive in sparsely available saturation or to move long distances to find wetter conditions. Future conservation efforts should focus on allowing safe dispersal among habitats by reducing obstructions and risks to travel near streams. I n chapter 5, I used GIS-derived data to compare land cover, stream order, topographic wetness index inverse, presence of hydric soils, and presence of National Wetland Indicator (NWI) wetlands on bog turtle occupied wetlands (n=50) to the same variables on apparently unoccupied (n=48) wetlands or random areas (n=74) along streams. Occupied areas differed from random areas in having near zero values of the topographic wetness index inverse (indicating areas with low slopes and large upstream drainage areas that are more prevalent in wet portions of the landscape), the presence of > 50% low vegetation typical of non-forested agricultural areas, and presence of 3rd order streams. I used significant regression coefficients to create a GIS layer of high quality bog turtle habitat over the landscape, and tested this layer with bog turtle field survey data collected in 2009 independently of model building data. The resulting model has the potential to quickly rule out large portions of the landscape as potential bog turtle habitat. Finally, in Chapter 6, I provided general recommendations for managing bog turtle habitats in Southwestern Virginia. Managing bog turtle wetlands must emphasize the maintenance of high water tables, while avoiding inundation. Maintaining connectivity among wetlands used by bog turtles is an important aspect to consider when developing bog turtle conservations plans associated with development and other land use changes. Educating landowners and enforcing existing wetland laws are imperative for effective bog turtle management in Southwestern Virginia. / Ph. D.

Salt marsh creation provides functions and values that are essential to maintain the welfare of people and the integrity of coastal area ecosystems. The literature review provides greater understanding of salt marsh functions and values technical information regarding wetland creation in coastal regions. Interviews and case study analyses identify issues and opportunities regarding salt marsh creation. Products of this study include a model approach, criteria for project evaluation, and principles and guidelines for salt marsh creation and coastal residential development. Model approach applies the technical information and processes of salt marsh creation provided by scientists and engineers to the landscape architecture design process. The model approach encourages involvement of the client and other professionals throughout the planning and design process. The proposed criteria provide a framework for landscape architects to evaluate the structure and function of created ecosystems and developments. Four salt marsh creation projects around the Chesapeake Bay were selected for review and evaluated according to these criteria. Each project provides evidence that salt marsh creation can benefit residential developments by providing long-term shoreline protection, water purification, wildlife habitat, and amenity of a naturalistic landscape. Design principles and guidelines will help ensure that the model approach is used by developers to attain salt marsh creation that fits the patterns and functions of surrounding ecological systems and increases residents' awareness of both functions and values of salt marsh and the larger. / Master of Landscape Architecture

Forested peatlands of the Great Dismal Swamp (GDS) have been greatly altered since colonial times, motivating recent restoration efforts. Community structure and function were hydrologically altered by 19th and 20th century ditches installed to lower water levels and enable early timber harvesting. Contemporary forest communities are comprised of maturing remnants from selective timber harvesting that ended in the early 1970s. Red maple (Acer rubrum) has become the dominant species across GDS, encroaching on or replacing the historical mosaic of cypress (Taxodium spp.)/tupelo (Nyssa spp.), Atlantic white-cedar (Chamaecyparis thyoides), and pocosin (Pinus spp.). Moreover, peat soil has been exposed to more unsaturated conditions resulting in carbon loss through decomposition and increased peat fire frequency and severity. Installation of ditch control structures aim to control drainage and re-establish historical hydrology, vegetation communities, peat accretion rates, and fire regime. To help inform restoration and management, we conducted two complimentary studies to test hypotheses regarding hydrologic influences on vegetation, peat depths, and peat fire vulnerability. First, we found thicker peat, lower maple importance, and higher species richness at wetter sites (e.g., higher mean water levels). In our second study, we evaluated the integrated effects of peat properties and water level dynamics on peat fire vulnerability. We found decreased burn vulnerability with increased wetness, suggesting that the driest sites were always at risk to burn, whereas the wettest sites never approached fire risk conditions. Together our findings demonstrate strong hydrologic controls on GDS ecosystem structure and function, thereby informing water level management for restoration goals. / Master of Science

Research documenting the functional changes of wetlands in response to harvest disturbance has often been limited to initial-response time frames of one or two years. A cypress (Taxodium distichum L. Rich.)-water tupelo ~ aQuatica L.) swamp located in the Mobile-T ensaw River Delta of Southwestern Alabama was harvested in the fall of 1986. Harvest treatments included: c1earcutting the entire study area with helicopter log removal, or with an added simulated rubber-tired skidder transport, or with herbicide control of all regenerating vegetation. An adjacent nondisturbed stand served as a reference area. Remeasurement of the area was initiated seven years after harvest. The helicopter logged and skidder simulation treatments have produced stands of comparable diameter, height, density, and basal area. ~ aqyatica was dominant in the skidder simulation treatment~ ~ tica, ~ nigra, and Fraxinus caroliniana dominated the helicopter treatment. Overstory biomass was less in the helicopter logged areas (20,981 kg/ha) than in the skidder simulation treatment (30,533 kglha). Lowerstory trees in both treatments were of comparable diameter and height, however, the helicopter treatment contained a greater density, basal area, and biomass ofFraxinus caroliniana. The rutting and mounding associated with the skidder simulation treatment favored a greater diversity of both diversity of both lowerstory and herbaceous species. Groundflora biomass was greatest in the herbicide controlled treatment (13,127 kg/ha), comparable in both the helicopter logged and skidder simulation treatments (5128 kg/ha; 5648 kglha, respectively), and least in the reference area (1495 kglha). Sediment accumulation reflected these differences in groundflora biomass; 104 mm in the herbicide controlled treatment, 79 mm and 63 mm in the helicopter logged and skidder simulation treatments, respectively, and 37 mm in the reference area. Three gradients were identified in the study areas via the tests of Latin squares, rows, and columns which actually corresponded to gradients of hydrology and! or sediment deposition. Square two was wetter than squares one or three because square two had fewer residual pullboat runs, which facilitate greater water movement. The rows are indicative of the distance from the main river channel; rows nearer the river are slightly higher in elevation, less inundated, and favor the less flood tolerant species. The columns reflect the sediment trapping patterns of the vegetation and the subsequent effects of site hydrology and nutritional status. / Master of Science