published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

<p>Rich fens are an important, but threatened, habitat type in the boreal landscape. In this thesis I have examined responses of rich fen vascular plants and bryophytes after drainage and restoration. </p><p>The effects of drainage on the rich fen flora were observed in a long time study and the responses were rapid and drastic. During an initial stage a rapid loss of brown mosses was observed, followed by increases of sedges and early successional bryophytes, and later by an expansion of dominants. Initial effects of hydrological restoration showed that rewetting can promote re-establishment of an ecologically functional rich fen flora, but has to be combined with other treatments, such as mowing or surface disturbance. </p><p>After restoration, re-establishment of locally extinct species may be hampered by dispersal limitations. To test if reintroductions could help to overcome dispersal limitations I performed transplantation studies with four common rich fens bryophytes to a rewetted site. The results showed that the species were able to establish, and that survival and growth were promoted by desiccation protection and liming. </p><p>I further examined competition among three of the most common bryophytes in natural boreal rich fens that usually occur mixed in a mosaic pattern but show small but important microtopographical niche separation. The results indicate similar competitive abilities among the species, and no case of competitative exclusion occurred. The results help to explain the coexistence of these species under natural conditions with microtopographic variation and repeated small scale natural disturbances. </p><p>Restoring a functional flora in drained rich fens is a complex task, which requires understanding of underlying causes of substrate degradation in combination with suitable restoration measures. The thesis suggests how the results can be used in practical restoration work, and also stresses the need for monitoring of restoration experiments over longer time. </p>

<p>This study was made as a part of a feasibility study on a polishing wetland at Rimbo wastewater plant (wwp) in Norrtälje municipality. The wwp had to decrease the nitrogen discharge to reach the limit 15 mg tot-N/l. The nitrogen in the outlet was mainly in the form of nitrate, hence the wetland mainly ought to support denitrification. The proposed area for the wetland was situated right next to the wwp and was already in the municipalitys posession. One aim of this study was to examine what spieces of plants needed to achieve highest possible denitrification. Some different plant spieces for providing a good and interesting environment for birds and people were also proposed. Furthermore a massbalance model was developed for studying the important exchange processes in a wetland, to study the impact of an uneven streambed on the hyporheic water exchange and for trying to predict the wetlands nitrogen removal capacity. Proposed plants to support denitrification was different reeds such as Common reed (Phragmites australis), Bulrush (Typha), Reed Sweet-grass (Glyceria maxima) och Reed Canry-grass (Phalaris Arundinacea). Common reed is a durable species who can survive in deeper water up to 2 metres while the others need a shallower water about 0,5 m of depth. For the good of the birdlife, different spieces of Sedges (Carex) were chosen due to their ability to produce large amounts of nutrient rich seeds. Measurment in sediment cores from Ekeby wetland in Eskilstuna gave a potential denitrification capacity of 3,31 mg NO3-N m^-3 _sed s^-1. The denitrification capacity was then used in a massbalance model were the theory of advective pumping in an uneven bedsurface also was implemented. Evaluation of the model results showed that an uneven bedsurface did not contribute to an increased nitrogen removal from the wetland, possibly due to a far too low advection and flow of the water. This was also a reason to why the distribution between denitrification from the water- and plant community vs the sediment was unbalanced. The model results showed that less than 1 % of the reduced nitrogen came from the sediment part, in contrast to current knowledge that says about 50%. The model and the participating exchange processes need to be further evaluated before the models prediction of nitrogen removal can be used in design of a wetland. Calculations and comparisons with other wetlands showed that with a well estimated, grown up and maintained wetland, there should be no problems in achieving the goal of nitrogen removal in Rimbo wetland. Such a wetland should also provide a good habitat for birds and animals and also be a good recreationarea for people to visit, properties that were appreciated as important effects in other wetlands studied in this work.</p> / <p>Detta arbete gjordes som en del av en förstudie för anläggande av en efterpolerande våtmark till reningsverket i Rimbo, Norrtälje kommun. Reningsverket behövde sänka sitt utsläpp av kväve till riktvärdet 15 mg tot-N/l. Huvuddelen av kvävet i utloppsvattnet förelåg i nitratform, varför denitrifikationen borde förstärkas genom att anlägga en våtmark. Det tilltänkta området för våtmarken ligger i anslutning till reningsverket och ägs idag av kommunen. I detta arbete undersöktes vilken växtlighet i våtmarken som var lämpligast för syftet att få en så bra denitrifikation som möjligt. Även olika växtarter för att ge en intressant miljö för fåglar och människor togs fram. Dessutom utvecklades en massbalansmodell som användes för att studera de utbytesprocesser som är viktiga i en våtmark, frågan hur en ojämn bottenmorfometri påverkar det hyporheiska vattenutbytet samt om det går att förutsäga reningskapaciteten i Rimbo våtmark. Lämpliga växter för denitrifikationen ansågs vara vassbildande växter, och då främst främst bladvass (Phragmites australis), men även kaveldun (Typha), jättegröe (Glyceria maxima) och rörflen (Phalaris Arundinacea). Bladvass är en mycket tålig växt som klarar stort vattendjup, medan de andra vassorterna behöver en grundare våtmark på ca 0,5 m. För fågellivets bästa ansågs starrväxter (Carex) vara viktiga arter då de producerar stora mängder frön. Mätning av denitrifikationspotentialen i sediment från Ekeby våtmark gav en hastighet för denitrifikationen i sedimentet på 3,31 mg NO3-N m^-3 _sed s^-1. Denitrifikationen från sediment användes sedan i en massbalansmodell där även även teorin om advektivt pumputbyte vid ojämn bottenform implementerades. En utvärdering av modellresultaten kunde avgöra att en ojämn eller vågig bottenmorfometri inte skulle förbättra reningen i våtmarken. Detta beroende på bland annat för låg advektionshastighet och flöde. Detta låga flöde ned i sedimentet bidrog även till att fördelningen av kväveborttag från sediment respektive vatten- och växtdelen blev snedfördelad. Enligt modellen var det mindre än 1% av kvävet som togs bort från sedimentet medan all vetenskap tyder på närmare 50%. Modellen och de ingående utbytesprocesserna bör utvärderas och utvecklas ytterligare innan den kan användas som verktyg för att beräkna kvävereningen från en våtmark. Beräkningar och jämförelser med andra våtmarker visade dock att en väl beväxt, utförd och beskickad våtmark inte skulle ha några problem att sänka nitrathalten till riktvärdet. En våtmark skulle även utgöra en bra uppehållsmiljö för fåglar, djur och människor vilket anses som viktiga mervärden i våtmarker på andra platser i Sverige.</p>

The Waiwhero wetland (16 ha) is one of the largest wetlands in the Rosedale Hills, 35 km north-west of Nelson, New Zealand. It has an extensive cover of Salix fragilis L. (crack willow) and has been hypothesised to be a source of groundwater recharge for the Moutere aquifers, an important local groundwater system. However the wetland could also be a groundwater discharge zone, because of the geological boundary that it straddles. The overall aim of this study was to determine the direction of groundwater flux of the wetland by measuring the water balance, with particular emphasis on the transpiration rates from the crack willow trees. The average daily transpiration (measurement was for 230 days) of crack willows in the wetland (6.4 mm/day) was close to twice the potential evapotranspiration (PET) for grassland (3.9 mm/day). The highest measured willow transpiration rate was 12.4 mm/day and the lowest was 0.8 mm/day. High transpiration from crack willows was due to the horizontal energy fluxes (advective energy), tree physiological characters and high soil water content. The study established that the wetland is a groundwater discharge zone with, on average for the two summer periods (2008 and 2009), the net groundwater discharge being 4.8 mm/day. The daily water balance results between two major rainfall events showed that the initial discharge source was from the surrounding hills and later stabilized at around 6 to 14 mm/day. It was believed to be a contribution from the shallow and deep aquifers or a combination of local region inflow and aquifers. The water balance showed that the main loss of water through the hydrological system of the wetland during summer was from the high transpiration of willows (7.7 mm/day). The extent of water savings estimated for the 16 ha wetland through a hypothetical situation of willow removal, and the assumption that it is filled with open water without any canopy cover, was 688 m3/day. However this water savings rate if applied to a large area of crack willow stands would be quite high. On similar lines it is important to understand the transpiration rates of other wetland tree species in New Zealand. This information would help in preparing regional council plans for the introduction of tree species in the wetland for better management of the water resources and sustainable ecosystem management.

The Tonle Sap is the largest and most important natural wetland in Southeast Asia. It covers an area of more than 15,000 km2 with a unique mosaic of natural and agricultural floodplain habitats that coexist with the largest fishery in the Mekong Basin. Accelerating hydropower development and climate change, however, are altering the Mekong’s hydrology, which could negatively affect downstream ecosystems. The Tonle Sap is facing a two-fold problem. First, the link between its hydrology and ecosystem properties is not well understood. Second, potential ecological changes caused by future hydrological disruptions related to hydropower and climate change are unknown. Thus, the main objective of this thesis was to quantify how alterations to the Mekong hydrology could affect the Tonle Sap ecosystem. The following studies were performed to addressed the objective: (1) an assessment of landscape patterns using geographical information and remote sensing tools; (2) an assessment of habitat patterns based on field surveys of water, vegetation, and soils; (3) ecosystem function modelling to simulate net primary production (NPP) as a function of water quantity, sediments, and habitat type; and (4) fauna habitat modelling linking the results from the assessment of landscape patterns to fauna species. The assessment of landscape patterns revealed a distinct relationship between inundation and vegetation. Habitats in the Tonle Sap were divided into five groups based on annual flood duration, as well as physiognomic factors and human activity: (1) open water, (2) gallery forest, (3) seasonally flooded habitats, (4) transitional habitats, and (5) rainfed habitats. Large habitat shifts could occur as a result of hydropower development scenarios by the 2030s; areas optimal for gallery forest could decrease by 82% from baseline conditions, whereas areas of rainfed habitats could increase by 10-13 % (813-1061 km2). The assessment of habitat patterns demonstrated that despite the complexity and intense human use of this ecosystem, the flood-pulse is the underlying driver of habitat characteristics by (1) determining inundation depth and duration; (2) creating the main soils gradient; (3) limiting the area cleared for agriculture; (4) influencing vegetation structure and water quality; and (5) shaping the composition of plant species. The ecosystem function model was used to estimate a reduction of 9-39% in annual NPP caused by different scenarios of hydropower development and/or climate change during 2032-2042. Cumulative impacts from hydropower would disrupt NPP to a greater extent than climate change. The fauna habitat model revealed that species richness was greatest in the gallery forests and seasonally flooded habitats. Animals that permanently reside in or that rely on these habitats to complete essential life-history stages would be the most affected by future changes. This thesis provides the first quantitative formulation that directly links fundamental components of the Tonle Sap ecosystem to its flood-pulse hydrology. It also provides a comprehensive assessment of the impacts of expected hydrological alterations. Hydropower is expected to bring more abrupt and distinct ecological alterations than climate change in future decades. Relative aerial changes to the gallery forests are expected to be greater than in other habitats. A decline of the Tonle Sap’s ecosystem services will occur if appropriate measures are not implemented. These measures include mitigating hydropower alterations, conserving natural habitats in areas that are likely to remain hydrologically undisturbed, restoring natural habitats in projected areas for optimal growth, and optimizing agricultural practices in the floodplain. Research findings from this thesis focused on the Tonle Sap, but given the fundamental commonalities between this system and other large floodplains, the information presented is highly informative to other large flood-pulse driven systems around the globe.

New knowledge gained over the past 15 to 20 years on the management of riparian zones in Arizona for water yield improvement has been organized and analyzed. Hydrologic processes and principles applicable to riparian zones, the distribution and nature of riparian vegetation in Arizona, and new resource management methods, needs, and constraints have been evaluated, The relationship between vegetation management for water yield improvement and other resource based products and uses of riparian zones such as timber, range for livestock, wildlife and fish, recreation, and aesthetics was also assessed. Past studies and surveys indicate that Arizona has approximately 280,000 to 320,000 acres of riparian vegetation, However, pertinent information such as species composition, vegetation density, depth to groundwater, groundwater quality, and landownership have not been mapped accurately for many riparian zones in Arizona, A continuous survey of riparian vegetation cover by remote sensing supplemented by ground truth is suggested to remedy this situation. Analysis of hydrologic studies indicated the following identifiable trends in water use by riparian species, Saltcedar, arrowweed, cottonwood, and hydrophytes are the heaviest users of water (between four and eight feet of water annually). Intermediate water users (annual use between two and five feet) are seepwillow, mesquite, quailbrush, four-wing saltbush, and greasewood. Lesser amounts of water are transpired by grasses and sedges and evaporated from bare soil (0,5 to three feet annually). Five water yield improvement methods applicable to riparian zones are evaluated; conversion of one vegetation type to another, channelization, cottonwood thinning, antitranspirant and biological control treatments. Conversion treatments to grasses or crops may yield water savings of up to 2,5 acre-feet per acre annually during the first year, However, some or all of this water may eventually be used by replacement vegetation, Several constraints including possible loss of wildlife habitat, contamination of water supplies by chemical herbicides, lowered aesthetic quality, and increased soil erosion with the removal of riparian vegetation reduce the opportunities for converting a large percentage of riparian vegetation in Arizona, To justify operational conversion programs in Arizona follow up studies of current conversion projects should be instituted, Rates at which revegetation takes place, declines in water salvage as revegetation occurs, amount and value of increased herbage production, and long term effects on plant distribution and animal life need to be determined. Channelization projects in the Southwest have been credited with increasing water yields; however, methods for determining these increases are poorly documented. Channelization for flood control purposes is limited because flow of flood water is accelerated in the vicinity of the excavation and may contribute to flooding and sedimentation on unchanneled segments. Cottonwood thinning designed to reduce evapotranspiration and flood hazards has been conducted along the Verde River, Increased water yields have not been measured, Adverse effects on fish and wildlife have been reported as a result of thinning cottonwoods. Limited thinning of cottonwoods to prevent bridges from washing out or to protect existing structures on the floodplain may be beneficial. Application of antitranspirant foliar sprays to reduce plant water use is a potential treatment method for increasing water yield in riparian zones. Antitranspirants were effective in reducing transpiration rates of saltcedar plants by up to 38 per cent for three to five weeks in greenhouse and limited field studies, Research on the feasibility of obtaining supplementary water from riparian vegetation through the application of antitranspirants should be expanded, Antitranspirants, if proven safe and effective, may be mutually acceptable to water, recreation, and wildlife interests. Biological control of saltcedar is not effective at present.

The Cienega de Santa Clara is a 5600 ha, anthropogenic wetland in the delta of the Colorado River in Mexico. It is the inadvertent creation of the disposal of brackish agricultural waste water from the U.S. into the intertidal zone of the river delta in Mexico, but has become an internationally important wetland for resident and migratory water birds. The marsh is dominated by Typha domengensis with Phragmites australis as a sub-dominant species in shallower marsh areas. The most important factor controlling vegetation density was fire. The second significant (P<0.01) factor controlling NDVI was flow rate of agricultural drain water from the U.S. into the marsh. Reduced summer flows in 2001 due to canal repairs, and in 2010 during the YDP test run, produced the two lowest NDVI values of the time series from 2000 to 2011 (P<0.05). Salinity is a further determinant of vegetation dynamics as determined by greenhouse experiments, but was nearly constant over the period 2000 to 2011, so it was not a significant variable in regression analyses. Evapotranspiration (ET) and other water balance components were measured in Cienega de Santa Clara; we used a remote sensing algorithm to estimate ET from meteorological data and Enhanced Vegetation Index values from the Moderate Resolution Imaging Spectrometer (MODIS) sensors on the Terra satellite. We used Landsat NDVI imagery from 1978-2011 to determine the area and intensity of vegetation and to estimate evapotranspiration (ET) to construct a water balance. Remote sensing data was supplemented with hydrological data, site surveys and literature citations. The vegetated area increased from 1978 to 1995 and has been constant at about 4200 ha since then. The dominant vegetation type is Typha domingensis (southern cattail), and peak summer NDVI since 1995 has been stable at 0.379 (SD = 0.016), about half of NDVI(max). About 30% of the inflow water is consumed in ET, with the remainder exiting the Cienega as outflow water, mainly during winter months when T. domingensis is dormant.

Bald cypress (Taxodium distichum) is known to respond to increases in precipitation with increased radial growth even when rooted in continuously saturated sediments where water is not a growth-limiting factor. Measurements of δ¹⁸O, Cl⁻, ³H and hydraulic head in surface water and shallow groundwater in an oxbow lake-wetland in northern Mississippi show that rapid downward flow of surface water into the root zone is initiated only after precipitation-induced increases in surface water depth exceed a threshold value. Rapid flow of surface water through the root zone has the potential to introduce oxygen to sediments that would otherwise be anoxic, facilitating nutrient uptake and growth. Climatic reconstruction using tree rings from bald cypress in this environment appears possible because increases in precipitation generally correlate well with increases in water level, which in turn enhances the delivery of oxygenated water to the roots.

This study focused on the investigation of the impact of household cleaning and personal care products on the quality of grey water and the assessment and optimisation of grey water treatment by a novel constructed wetland design. The prototype wetland design which comprised three-stage cascading beds (0.27 m 2 by 0.20 m deep) with sand media, (d10: 1.0 mm and d90: 4.0 mm) was tested for treatment performance to meet non-potable reuse standards in three versions, unplanted open beds, unplanted covered beds, and planted beds (comprising mixtures of Iris pseudacorus, Iris chrysographes, Carex elata Aurea and Mentha aquatica). The prototypes were benchmarked against a standard single-pass wetland (6 m 2 by 0.7 m) planted with Phragmites australis. Performance was measured in terms of removal of conventional water quality determinant parameters, as well as Total coliforms and E coli, and surfactants. Microbial dynamics were also monitored during the study by looking at variations in microbial compositions with time for the different wetlands. All the wetland versions effectively removed more than 98 % turbidity and organics meeting the most stringent reuse wastewater reuse standards of < 2.0 NTU and < 10 mg BOD5/L respectively. The influent grey water had low BOD:COD ratio ranging from 0.27 – 0.45, which is indicative of low biodegradability. The comparison of the cascade wetland performances showed the following: open beds > planted = covered, with the open beds version meeting reuse standards virtually throughout the monitoring period, despite recurrence of schmutsdecke in the top bed. All wetland technologies supported viable populations of microorganisms. Only phospholipid fatty acids (PLFAs) of lower carbon chain length (< C20) had concentrations greater than 1 mol %, in all the wetlands beds, confirming that the majority of the PLFAs in the media were from contribution of microbial organisms and not plant organic matter. Characterisation of microbial organisms was carried out to understand the constructed wetlands functioning and thus the treatment processes. The household products showed nutrient deficiency signifying low treatability. Product branding did not show correlation with any water quality parameters. In terms of toxicity, laundry and cleaning products were more inhibiting to soil microorganisms than were personal care products.

Farmyard runoff, i.e. the effluent generated by the rain falling over farmyards, tracks and roofs, is a significant and overlooked source of nutrients and pathogens which degrades aquatic ecosystems through eutrophication, siltation and wildlife poisoning, raises public health concerns, and incurs considerable costs for society. Among other Best Management Practices implemented to address agricultural water pollution and help achieve compliance with the Water Framework Directive, Constructed Farm Wetlands (CFWs), i.e. shallow surface flow wetlands comprising several vegetated cells in series, are being recommended for remediation of farmyard runoff, due to their capacity to remove or store pollutants. Investigation is therefore needed of their long-term water treatment efficiency and ecological value to optimize their design and cost-effectiveness and minimize their negative externalities. The main aims of this study were to: 1) evaluate the treatment performance of CFWs and the link between design, hydrology and efficiency; 2) assess their ecological value and the influence of water quality and design on wetland ecology; 3) identify their costs, benefits and the way they are perceived by farmers; and 4) inform guidelines for the design, construction and aftercare of sustainable CFWs. Research focused on two CFWs in south-east Scotland, one at a dairy farm and one at a mixed beef-arable farm, which receive runoff from yards and roofs, field drainage and septic tank overflow. From February 2006 to June 2008, rainfall, evaporation, water levels and flow at the CFWs were monitored, and their treatment efficiency was assessed from water samples collected manually regularly or with automatic samplers during storm events, and analysed using standard methods. In addition, their ecological value was assessed twice a year from vegetation and aquatic macroinvertebrate surveys. Finally, semi-structured interviews with eight farmers and a farm advisor and discussions with three CFW designers in Scotland and Ireland allowed collection of technical and economic data on farm practices, CFW construction and maintenance, and helped assess CFW cost-effectiveness and acceptance by farmers. Both CFWs reduced pollutant concentrations between inlet and outlet, with efficiencies at CFW1 and CFW2 respectively of 87% and < 0% for five-day biochemical oxygen demand, 86% and 83% for suspended solids, 68% and 26% for nitrate/nitrite, 42% and 34% for ammonium, and 12% and 31% for reactive phosphorus. Nevertheless, the concentration of all pollutants at the outlet of CFW1, and concentration of nitrate/nitrite at the outlet of CFW2 frequently exceeded river water quality standards. Water treatment efficiency varied seasonally, being significantly lower in winter, mainly due to lower temperatures, increased volume of inputs and reduced residence time. The ecological value of the two CFWs differed greatly. At CFW1 and CFW2 respectively, 14 and 22 wetland plant species and 24 and 46 aquatic macroinvertebrate species (belonging to 13 and 27 BMWP scoring families respectively) were recorded, illustrating the greater biodiversity conservation value of CFW2, which was one year older, larger, cleaner, comprised several ponds with a combination of open water and densely vegetated areas, and was subsequently more structurally diverse. The socio-economic study revealed that, despite significant costs associated with their construction (£20 000-£50 000 ha-1) and maintenance (£900-£1500 ha-1 yr-1), CFWs may still represent a more cost-effective alternative than conventional methods. However, their adoption, implementation and sustainable use by farmers were conditioned by land availability and suitability, existing farm infrastructure, detailed information on limitations and maintenance requirements, and adequate financial support for both construction and aftercare. To ensure a long-term, consistent and efficient water treatment, and to enhance biodiversity and landscape, well-maintained, large, vegetated, multi-cell CFWs with shallow overflows are recommended. Their size should be adapted to local precipitation patterns and catchment characteristics. Keywords: agriculture, best management practice (BMP), biodiversity, constructed farm wetland (CFW), costs, farmyard runoff, water pollution, water treatment.