No description available.

Ecological restorations have become increasingly important as humans have made irreversible changes to ecosystems; biogeochemical cycle alterations and land use changes have led to degraded conditions (Vitousek et al. 1997a). While some modifications to the environment are unavoidable, society is beginning to realize that changes are necessary. While some ecosystem functions may be beyond repair (e.g., biodiversity loss and extinction of species), it is important that the problem is faced head on and those functions that are still salvageable be restored. These environmental repairs can be done through ecological restoration. I looked at two different ecosystems, prairie streams and agricultural streams, that have undergone restoration to help functions. Patch-burn grazing (PBG) is increasingly used as a management practice on the few remaining tallgrass prairie parcels in an effort to simulate effects of large ungulate grazers. Yet, little is known about potential impacts and recovery of aquatic habitats from this management approach. My objective was to assess the influence of PBG with cattle on prairie streams and build on previous research at this site. I hypothesized that cattle grazing would negatively impact water quality and reduce stream biotic integrity, but riparian fencing would mitigate these impacts. We also assessed stream recovery for two years following the removal of ungulates from the study sites and hypothesized that biological and chemical effects would reverse. Six headwater streams (two controls, two PBG with 10 m fenced riparian zones, and two PBG with unfenced riparian zones) on Osage Prairie, Missouri, were sampled over seven years (2009-2015) encompassing pre-PBG (2 years), PBG (3 years), and post-PBG (2 years) periods. Macroinvertebrates and water chemistry were sampled monthly. Nitrate (NO3-) concentrations increased in the fenced and unfenced watersheds compared to the control watersheds (p = 0.015 and p < 0.0001, respectively) and between the fenced and unfenced watersheds (p = 0.001) during the PBG period relative to pre-PBG. Total phosphorus (TP) increased in the fenced and unfenced watersheds after grazing began compared to the control (both p < 0.0001) but did not differ between the fenced and unfenced watersheds (p = 0.187). Relative Chironomidae biomass and abundance increased in the unfenced watersheds in response to grazing (p = 0.008 and p < 0.001, respectively). No differences were observed in relative Chironomidae biomass and abundance, NO3-, and TP from pre-PBG to post-PBG indicating the recovery of these metrics. Results suggest that the negative effects of PBG on prairie streams can be somewhat mitigated by riparian fencing. Additionally, these streams are relatively resilient to PBG and recovery can take place during a rest cycle as brief as two years. Approximately one billion dollars is spent annually on restorations of degraded stream reaches in the United States. However, few projects are monitored upon completion, or monitoring focuses on a single parameter. Other than modifications to physical attributes of streams, the influence of restoration projects on ecosystem processes remains largely unknown. We sampled eleven Midwestern streams that had undergone habitat restorations from 3-15 years prior to sampling. Restoration techniques included in-stream habitat enhancements, bank stabilization, and riparian restoration. We predicted that gross primary production (GPP) would be lower in restored streams due to decreased nutrient inputs, and that respiration would be greater due to increased litter inputs from restored riparian areas. We also hypothesized that the restored streams would have greater invertebrate richness, abundance, and biomass, as well as high densities of intolerant taxa such as Ephemeroptera, Plecoptera, and Trichoptera (EPT taxa) due to higher water quality and better habitat. Restored reaches and unrestored upstream reaches were sampled for physical characteristics, water chemistry, benthic algal biomass, whole-stream metabolism, and macroinvertebrate communities. GPP in restored sites was marginally higher than unrestored sites (t5 = 2.53, p = 0.05), despite no differences in PO4-3, NO3-, or NH4+ concentrations. Three restored sites were autotrophic (P/R > 1), while four unrestored sites were heterotrophic. Total macroinvertebrate biomass was marginally higher in the restored sites compared to unrestored sites (t10 = 1.94; p = 0.08). EPT biomass was also marginally higher in restored sites than unrestored sites (t10 = 1.91; p = 0.09) but no difference was observed in EPT abundance. Results suggest that stream habitat restorations enhance some, but not all ecosystem processes and marginally enhance macroinvertebrate communities.

Through complex metabolic interactions aquatic microbial life is essential as a driver of ecosystem functions and hence a prerequisite for sustaining plant and animal life in the sea and on Earth. Despite its ecological importance, infor­mation on the complexity of microbial functions and how these are related to environmental conditions is limited. Due to climate change and eutrophication, marine areas facing oxygen depletion are increasing and predicted to continue to do so in the future. Vertically steep oxygen gradients are particularly pronoun­ced in the Baltic Sea. In this thesis, therefore, the ecosystem functions of micro­bial communities were investigated, using metagenomics, to understand how they were distributed along the steep oxygen gradient at the Landsort Deep, the deepest point of the Baltic Sea. Furthermore, microbial communities from the Lands­ort Deep transect were compared to microbial communities of other marine environments to establish whether the environment at this site resulted in a characteristic community. To reveal what microbial community functions and taxa were active in the anoxic sediment a metatranscriptomic approach was used. Results showed a marked effect of the coupled environmental parameters dissolved oxygen, salinity and temperature on distribution of taxa and par­ti­cularly community functions. Microbial communities showed functional capa­cities consistent with a copiotrophic life-style dependent on organic ma­terial sinking through the water column. The eutrophic condition with high organic load was further reflected in the metatranscriptome of the anoxic sedi­ment com­munity, which indicated active carbon mineralisation through ana­erobic hetero­trophic-autotrophic community synergism. New putative linkages between nitro­gen and- sulphur metabolisms were identified at anoxic depths. Further­more, viable Cyanobacteria in the anoxic sediment was evident from the tran­script analyses as another reflection of marine snow. High abundance and expres­­sion of integron integrases were identified as a charac­teristic feature of the Lands­ort Deep communities, and may provide these communities with a mech­an­ism for short-term-adaptation to environmental change. In summary, this thesis clearly documents what impact eutrophication and oxygen depletion have on microbial community functions. Furthermore, it specifically advances the mechanistic insight into microbial processes in anoxic deep-water sediment at both genomic and transcriptional level. Given the predicted progress of oxygen depletion in marine and brackish environments, this work advances information necessary to estimate effects on marine and in particular brackish ecosystem functions where anoxic conditions prevail. / Mikroorganismer är essentiella för fungerande ekosystemfunktioner i akvatiska miljöer och därmed en förutsättning för övrigt växt- och djurliv på vår planet. Trots deras ekologiska nyckelroll är kunskapen om mikroorganismernas funk­tion och komplexitet samt hur dessa är relaterade till miljön begränsad. På grund av eutrofiering och klimatförändringar har marina områden som lider av syrebrist ökat och en ytterligare utbredning av marina och bräckta områden med syrebrist är predicerad i framtiden. Stora områden av Östersjön kännetecknas av vertikala syregradienter med syresatt ytvatten och anoxiskt bottenvatten. I denna avhandling undersöktes därför med metagenomik hur mikrobiella ekosystems funktioner var utbredda längs den vertikala syregradienten i Östersjöns djupaste del, Landsortsdjupet. Dessutom jämfördes de mikrobiella samhällena från Lands­­­ortsdjupet med mikrobiella samhällen från andra marina miljöer för att utröna om den karakteristiska miljön i Landsortsdjupet återspeglade de mikro­biella samhällen som lever där. För att undersöka vilka mikroorganismer samt vilka mikrobiella ekosystemfunktioner som var aktiva i det anoxiska sedimentet i Lands­ortsdjupet användes metatranskriptomik. Resultaten visade en stark kor­re­lation mellan miljöparametrarna syrehalt, salinitet och temperatur och för­del­ningen av mikrobiell taxa och i synnerhet mikrobiell funktion längs Lands­orts­djupets transekt. De mikrobiella samhällena uppvisade en funktionell kapa­citet förenlig med en livsstrategi beroende av organiskt material som sjunker genom vattenkolonnen som en konsekvens av eutrofiering. Eutrofa förhållanden med hög halt av organiskt material var även återspeglad i metatranskriptomet från det anoxiska sedimentet, som indikerade aktiv mineralisering av organiskt kol genom anaerob heterotrof-autotrof synergism. Nya möjliga kopplingar mellan kväve- och svavelmetabolism identifierades i det anoxiska vattnet. Vidare visade resultat från metatranskriptom-analys att livsdugliga cyanobakterier var abun­danta i det mörka och anoxiska sedimentet, vilket även detta kan vara en konse­kvens av sjunkande organiskt material. Hög abundans och hög transkribering av integrongener kunde identifieras som ett karakteristiskt kännetecken hos de mikro­biella samhällena i Landsortsdjupet vilket skulle kunna förse dem med en me­kanism för anpassning till miljöförändringar. Sammanfattningsvis dokumen­terar denna avhandling tydligt vilken påverkan eutrofiering och syrebrist har på mikrobiella funktioner. Dessutom för den specifikt kunskapen om mikrobiella processer i anoxiska djupvattensediment framåt på både genom- och transkrip­tions­nivå. Mot bakgrund av en predicerad ökning av syrebristen i marina mil­jöer, bidrar denna avhandling med information som är viktig för att kunna förutse vilka effekter anoxiska förhållanden kan komma att få på ekosystemfunktioner i marina miljöer och i brackvattenmiljöer i synnerhet.

Bioeconomy strategies in high income societies focus at replacing finite, fossil resources by renewable, biological resources to reconcile macro-economic concerns with climate constraints. However, the current bioeconomy is associated with critical levels of environmental degradation. As a potential increase in biological resource use may further threaten the capacity of ecosystems to fulfil human needs, it remains unclear whether bioeconomy transitions in high income countries are sustainable. In order to fill a gap in bioeconomy sustainability assessments, we apply an ontological lens of coupled social-ecological systems to explore critical mechanisms in relation to bioeconomy activities in the global resource system. This contributes to a social-ecological systems (SES)-based understanding of sustainability from a high income country perspective: the capacity of humans to satisfy their needs with strategies that reduce current levels of pressures and impacts on ecosystems. Building on this notion of agency, we develop a framework prototype that captures the systemic relation between individual human needs and collective social outcomes on the one hand (microlevel) and social-ecological impacts in the global resource system on the other hand (macro-level). The BIO-SES framework emphasizes the role of responsible consumption (for physical health), responsible production (to reduce stressors on the environment), and the role of autonomy and selforganisation (to protect the reproduction capacity of social-ecological systems). In particular, the BIO-SES framework can support (1) individual and collective agency in high income country contexts to reduce global resource use and related ecosystem impacts with a bioeconomy strategy, (2) aligning social outcomes, monitoring efforts and governance structures with place-based efforts to achieve the SDGs, as well as (3), advancing the evidence base and social-ecological theory on responsible bioeconomy transitions in the limited biosphere.

Tropical coral reefs provide important ecosystem goods and services that are supported by one or more ecosystem functions (e.g., recruitment, primary production, calcification, and nutrient recycling). Scleractinian corals drive most of these functions, but a combination of global and local anthropogenic stressors has caused persistent shifts from coral- to algae-dominated benthic reef communities globally. Such phase shifts likely have major consequences for ecosystem functions; yet, related knowledge is scarce in general, but particularly at the community level, under ‘in situ’ conditions, and under the influence of changing environmental variables. Thus, we conducted a series of interconnected in situ experiments in coral- and algae-dominated reef communities in the central Red Sea, combining traditional community ecology approaches with novel metabolic and biogeochemical assessments from December 2016 to January 2018. Specifically, we (i) examined the influence of coral-algal phase shifts on recruitment and succession patterns, (ii) assessed the role of benthic pioneer communities in reef carbon and nitrogen dynamics, (iii) developed a novel approach to measure functions of structurally complex reef communities in situ, and (iv) quantified biogeochemical functions of mature coral- and algae-dominated reef communities. The findings suggest that coral-algal phase shifts fundamentally modify critical reef functions at different levels of biological organization, namely from pioneer to mature reef communities. For example, community shifts, through a lower habitat complexity and grazing pressure, decreased the number of coral recruits by >50 %, thereby inhibiting the replenishment of adult coral populations. At the same time, a 30 % higher productivity (annual mean) and increased organic carbon retention in algae-dominated communities supported a fast biomass accumulation and community growth, altering the habitat-specific community metabolism and reef biogeochemistry. Seasonal warming amplified these functional differences between coral- and algae-dominated communities, likely promoting a positive feedback loop of reef degradation under predicted ocean warming. Overall, this dissertation provides quantitative data on critical functions of classical and phase shifted novel reef communities, on tipping points for the collapse of community functions, and potential future winners and losers. The knowledge gained with this thesis helps, thereby, to understand how phase-shifted reef ecosystems function and which services will be generated in comparison to coral-dominated reefs under near-future stress scenarios.

Investigating forest soil biodiversity is essential to increase our understanding of ecosystem functions, assess potential consequences of global change, and thus optimize future decision-making processes. This cumulative PhD thesis contributes to this field by elucidating responses of bacterial and fungal forest soil communities, and their associated functions, in relation to tree diversity using a trait-based ecological approach with a focus on microbial living strategies. The three main chapters investigated microbial communities, using PCR-amplicon molecular methods, bioinformatics and novel statistics in the frame of the SoilForEUROPE project funded through the 2015–2016 BiodivERsA COFUND call for research proposals. Links between above-belowground biodiversity are crucial to understand forest functionality. For instance, studies on relationships of tree diversity and tree identity with microbial diversity reveal shifts in litter decomposition, nutrient cycling, primary production and the regulation of greenhouse gas emissions. These kinds of studies commonly compare microbial populations of different tree taxonomical groups. However, the effects of different tree taxa on microorganisms are mediated by tree morphology, physiology, phenology and genetics. Therefore, the use of specific plant traits to study biodiversity has become more frequent, adding a mechanistic understanding of compositional or functional shifts and interactions with soil microbial communities. This generalizable approach provides a common currency to compare similar microbial communities from different regions or environments with few microbial taxa in common. Microbial communities are also filtered by other processes such as global drivers, stochastic events, abiotic and biotic factors in addition to the mentioned tree traits. This environmental filtering process results in a functional microbial community structure, also with their own set of traits to increase their population size through higher performance and as response the capacity to affect their own ecosystem. Furthermore, it is expected that a particular set of microbial traits represents the life history strategies that favored a particular community under specific environmental conditions. This thesis correlates tree traits with bacterial and fungal communities by using a wide-ranged European forest platform with 64 plots of four different latitudinal regions. The SoilForEUROPE design also included multispecies and monospecific forests comprising 13 main tree species and 33 different tree species compositions. All these conditions supplied a diversity of environments to improve our knowledge of microbial soil diversity and above-belowground interactions. The here presented thesis encompasses five individual chapters. Chapter 1 provides the research context, project presentation and the main approach used. The Chapters 2 and 3 were developed in association with colleagues from the University of Freiburg and investigate four major European forest types: boreal forests (Finland), hemi‐boreal forests (Poland), mountainous beech forests (Romania) and thermophilous deciduous forests (Italy). Chapter 4 focuses purely on temperate forest plots and Chapter 5 compiles and concludes the results and presented ecological meanings. In particular, Chapter 2 evaluated the influence of tree species composition and diversity on fungal diversity and community composition, and highlights the relationships of fungal guilds and enzymatic activities with tree traits in detail, while also taking environmental variables into account. We demonstrated, how guilds like fungal saprotrophs mirror the litter quality, while tree root traits are often linked to an increasing number of fungal symbiotrophs. We found that forest types of higher latitudes, which are dominated by fast tree communities, correlated with high carbon‐cycling enzymatic activities. In contrast, Mediterranean forests with slow tree communities showed high enzymatic activities related to nitrogen and phosphorus cycles. In Chapter 3, we investigated links between bacterial communities, their functionality and root trait dispersion. Bacterial diversity revealed no major changes across the root functional dispersion gradient. In contrast, predicted gene profiles linked to plant growth activities suggested an increasing bacterial functionality from monospecific to multispecies forest. We also exposed that in multispecies forests, the bacterial functionality declines with the increasing functional dispersion of the roots. We further revealed important effects of the tree species identity on bacterial community composition, but we did not find significant relationships with root functional dispersion. However, bacterial network analyses indicated that multispecies forest have a higher complexity in their bacterial communities, which points towards more stable forest systems with greater functionality. Chapter 4 aimed to explore microbial communities of different soil depths from 0 to 30 cm across forests covering deciduous, evergreen and mixtures plots. Microbial abundance and diversity were especially affected by soil depth and by the presence of evergreen trees. Results showed higher accuracy to detect niche preference by using taxonomy levels than metabolic pathways or fungal guilds as features of a machine learning model. We found that bacterial communities are primarily shaped by soil depth in contrast to fungal community, which were rather influenced by the forest composition. Results also supported the importance of mixed forest to maintain nutrient cycling and a broad diversity of metabolites compared to monospecific forest and this differences where particular perceived in the upper 10 cm of soil. Chapter 5 concludes the thesis and presents a few remarks highlighting microbial strategies that might be favored under a particular soil forest composition. Overall, this thesis not only revealed the ecological patterns of soil forest microbial communities, but also provides a practical tool with necessary information to support decision-making and enlarge the schemes to conserve soil biodiversity.

Unionida musslor (stormusslor) är en djurgrupp som kan ha positiv påverkan på ekosystemfunktioner i vattendrag och ökar den biologiska mångfalden. Musslorna absorberar föda genom filtrering av vattenmassor, vilket genererar en bättre vattenkvalitet och ger mat till andra bottendjur. Syftet med denna studie var att undersöka en av våra svenska stormusslor flodpärlmusslan (Margaritifera margaritifera), och om det fanns något samband mellan musselbankar och bottenfauna. Provtagning av bottenfauna skedde i Vasslabäcken, Örebro län. 54 prover togs totalt och 27 av dem togs vid musselbankar medan resterande 27 var kontroll utanför musselbankar. Studien visade ingen signifikant skillnad i den totala bottenfaunans täthet i musselbankar jämfört med kontrollområden utanför musselbankar. Däremot fanns en signifikant högre täthet av nattsländor i kontrollerna än i musselbankarna, medan det inte fanns några skillnader i täthet mellan kontroller och musselbankar för några andra djurordningar. Det fanns även fler ordningar utanför musselbankar än i musselbankar, men antalet individer var så få att inga långtgående slutsatser kan dras. För att vidare undersöka musslors påverkan på flora och fauna kan man undersöka fler år och säsonger under året, samt använda sig av en mer experimentell design. / Unionidea mussels (large mussels) are a group of animals that can have a positive impact on ecosystem functions in watercourses and increase biodiversity. The mussels absorb food by filtering water masses, which generates a better water quality and provides food for other benthic animals. The purpose of this study was to investigate one of our swedish large mussels the freshwater pearl mussel (Margaritifera margaritifera), and whether there was any connection between musselbanks and benthic fauna. Sampling of benthic fauna took place in Vasslabäcken, Örebro region. A total of 54 samples were taken and 27 of them were taken at musselbanks while the remaining 27 were controls outside musselbanks. The study showed no significant difference in the density of the total benthic fauna in musselbanks compared with control areas outside musselbanks. On the other hand, there was a significantly higher density of moths in the controls than in the musselbanks, while there were no differences in density between controls and musselbanks for any other animal orders. There were also more schemes outside musselbanks than in musselbanks, but the number of individuals was so small that no far-reaching conclusions can be drawn. To further investigate the impact of mussels on flora and fauna, you can investigate more years and seasons during the year, and use a more experimental design.

Les sols des friches industrielles sont souvent multi-polluées et représentent des surfaces toujours plus importantes présentant de forts enjeux sociaux-économiques. Leur réhabilitation passe par une bonne compréhension du fonctionnement écologique des sols, qui, en plus d’être pollués, présentent des structures et des teneurs en nutriments souvent inhabituelles. Malgré cela, une recolonisation par la faune, la flore et les microorganismes est généralement observée. La capacité de ces nouvelles communautés à restaurer et maintenir les fonctions clés des sols reste à évaluer, et cela semble indissociable de la mesure d’une ou plusieurs fonctions écosystémiques. La décomposition de la litière est un processus écosystémique clef permettant la réalisation des cycles biogéochimiques du carbone et des nutriments. Les processus de la décomposition dépendent à la fois de ses acteurs (faune et microorganismes) et de la qualité de la litière végétale. De ce fait, la réponse de cette fonction écosystémique à la pollution du sol intègre les effets de cette pollution sur les communautés de plantes, d’animaux, et de microorganismes, ce qui en fait un indicateur potentiellement pertinent pour évaluer les effets de la pollution sur le fonctionnement des écosystèmes du sol. L’objectif central de cette thèse a donc été d’étudier le fonctionnement des friches industrielles en se focalisant sur les effets délétères de la pollution des sols sur la décomposition de la litière de feuilles. L’hypothèse centrale découlant de cet objectif a été que la pollution des sols pouvait impacter la décomposition par deux voies d’action. (1) La première voie, directe, est constituée de l’ensemble des effets délétères que pourraient provoquer les polluants sur les acteurs de la décomposition dont dépend la bonne réalisation de cette fonction. (2) Concernant la deuxième voie d’action, nous avons supposé que la pollution, en entraînant des modifications de la physiologie des plantes, pouvait modifier les paramètres physico-chimiques de la litière et ainsi impacter de façon indirecte la décomposition des litières. Nos résultats ont permis de montrer l’absence de l’effet direct pour huit friches industrielles fortement polluées, et ce malgré des perturbations des communautés d’acteurs, avec notamment une augmentation de l’abondance des détritivores et une modification de la colonisation microbienne des litières sur les sites pollués. Ces résultats plaident en faveur d’une redondance fonctionnelle suffisante au sein de ces communautés, permettant de maintenir le processus de décomposition. Nous avons également montré un effet indirect positif de la pollution sur la décomposition. Cet effet résulte de l’amélioration systématique de la qualité de la litière, entraînant dans certains cas une augmentation de l’activité des acteurs de la décomposition. Par ailleurs, nous avons également montré une accumulation des polluants dans ces mêmes litières, en particulier le Zn et le Cd, polluants pouvant potentiellement produire des effets délétères sur les acteurs de la décomposition. Toutefois, la présence de ces ETM n’a pas semblé influencer la consommation des litières par certains acteurs de la décomposition de la litière. Cependant, ce résultat reste à valider in situ en présence de l’ensemble des communautés de détritivores. De nombreuses perspectives s’ouvrent à la suite de ces travaux. Parmi elles, il reste notamment à déterminer 1) quels sont les mécanismes (physiologiques) qui entrainent une augmentation de la qualité des litières produites sur les sols contaminés ? 2) comment des communautés différentes permettent d’assurer des taux de décomposition similaires ? et 3) quels sont les impacts de la consommation des litières provenant des sites contaminés sur le fonctionnement et la physiologie des détritivores ? / Brownfield soils are multi-polluted areas, which cover an increasing surface and thus present serious socio-economical challenges. A better understanding of the ecological functioning of these sites is mandatory for their restoration. In addition to the high pollution found at these sites, brownfields are characterized by a specific soil structure and occasionally also by particular nutrient contents. Despite these constraints, several brownfield are well colonized by plants, fauna and microorganisms. The capacity of these new communities to uphold main ecosystem function remains to be evaluated based on the measurement of one or several ecosystem functions. Leaf litter decomposition is critically important in driving carbon and nutrient biogeochemical cycles. This function depends on decomposition actors (fauna and microorganisms) but also on leaf litter quality. By that, leaf litter decomposition integrates effects of soil pollution on plant, animal and microorganism communities. Thus, leaf litter decomposition is a relevant indicator to evaluate pollution effects on the functioning of soil ecosystems. The main objective of this thesis was to study brownfields soil function by focusing on the impairment of soil pollution on the leaf litter decomposition. The main hypothesis was that soil pollution could negatively affect leaf litter decomposition by two different ways. (1) By direct effects, resulting from adverse effects of soil pollution on decomposition actors, and (2) by indirect effects, assuming that soil pollution will induce modifications of the plant’s physiology, resulting in changes in leaf litter quality and subsequent effects on the decomposition. Our results revealed the absence of direct negative effects for eight highly polluted sites, despite a disturbance of decomposer actors, specifically the increase in abundance of detritivores and a modified microbial colonization of the leaf litter at the polluted sites. These results are in favor of a sufficient functional redundancy of decomposer actors in the local communities, which allowed the maintenance of the decomposition process. We also showed a positive indirect effect of soil pollution on the decomposition. This effect resulted from the improvement of litter quality produced at the polluted sites. This induced, at least for some sites, an increase of the decomposition rate, possibly due to a higher activity of decomposer actors. Furthermore, we also observed pollutants accumulation in these litter, especially Cd and Zn. These pollutants could potentially impair decomposition actors. Whatever, presence of these pollutants in litter did not impair litter consumption by some detritivores. Numerous perspectives can be developed from this study. Among them it seems specifically important to evaluate: 1) which are the (physiological) mechanisms behind the increase in leaf litter quality at polluted sites? 2) How can different communities assure the same decomposition rates at polluted sites? and 3) Are there negative effects observed on the performance and physiology of detritivores when consuming leaf litter from polluted sites ?

No description available.

Abstract Human activities have increasingly altered freshwater ecosystems. Land use is a major driver of habitat loss and land use-related input of nutrients and other pollutants from agriculture, forestry and urbanization have deteriorated water quality. Freshwater research has mainly focused on lakes and streams while the effects of anthropogenic stressors on groundwater-dependent ecosystems (GDEs) are poorly known. Likewise, the effectiveness of ecological restoration in mitigating human disturbance in GDEs remains understudied. In this thesis, I studied the effects of two main anthropogenic stressors – land drainage and groundwater contamination – on boreal spring ecosystems and evaluated the recovery of spring biodiversity and ecosystem functioning after habitat restoration. I applied several structural (macroinvertebrates, bryophytes, leaf-decomposing fungi and groundwater bacteria) and functional (organic matter decomposition and primary productivity) measures to provide a comprehensive insight into these issues. Both stressors modified spring ecosystems. Land drainage reduced the key ecosystem processes. Long-term monitoring of drainage-impacted springs showed a marked biodiversity loss and change of spring-dwelling bryophytes, and no signs of recovery were observed after about 20 years since the intial land drainage. Groundwater contamination, indicated by elevated nitrate and chloride concentrations, altered the structure of spring biota, reduced their taxonomic diversity and suppressed primary productivity in the most severely contaminated springs. Spring restoration improved habitat quality by reducing drainage-induced inflow of surface water, thus re-establishing groundwater-dominated hydrological conditions. Restoration increased abundance of habitat-specialist bryophytes and shifted macroinvertebrate composition towards natural conditions, despite the restoration actions being fairly recent. Anthropogenic activities can thus cause severe structural and functional degradation of spring ecosystems, and their self-recovery potential from these stressors seems low. Habitat restoration bears great promise as a cost-effective approach to mitigate drainage-induced impacts on spring ecosystems, but protection and co-management of groundwater resources are urgently needed to secure the role of springs as biodiversity hotspots in the boreal forest landscape. / Tiivistelmä Ihmistoiminta muuttaa yhä enemmän vesiekosysteemejä. Maankäyttö on johtanut elinympäristöjen häviämiseen, ja siihen liittyvä ravinne- ja haitta-ainekuormitus maa- ja metsätaloudesta sekä kaupunkiympäristöistä on merkittävästi huonontanut veden laatua johtaen maailmanlaajuiseen vesiluonnon monimuotoisuuden heikentymiseen. Vesiekosysteemien tutkimus on keskittynyt pääasiassa järvi- ja jokiympäristöihin, kun ihmistoiminnan vaikutukset pohjavesiriippuvaisiin ekosysteemeihin tunnetaan edelleen huonosti. Samoin kunnostusten merkitys pohjavesiriippuvaisten ekosysteemien tilan parantamiseksi on selvittämättä. Väitöskirjassani tarkastelin kahden keskeisen ihmistoiminnan – metsäojituksen ja pohjaveden laadun heikkenemisen – vaikutuksia lähde-ekosysteemeihin sekä arvioin elinympäristökunnostusten vaikutuksia niiden rakenteeseen ja toimintaan. Sovelsin työssäni rakenteellisia (pohjaeläimet, sammalet, lehtikariketta hajottavat sienet ja pohjavesibakteerit) ja toiminnallisia (eloperäisen aineksen hajoaminen ja perustuotanto) mittareita tuottamaan kattavan käsityksen tutkimuskysymyksiini. Sekä metsäojitukset että pohjaveden laadun heikkeneminen aiheuttavat muutoksia lähteiden rakenteessa ja toiminnassa. Metsäojitukset hidastavat keskeisiä ekosysteemitoimintoja ja johtavat lähdesammallajiston muutokseen ja monimuotoisuuden taantumiseen. Pohjaveden pilaantuminen, jota työssä ilmennettiin kohonneilla nitraatti- ja kloridipitoisuuksilla, heikentää lähdelajiston monimuotoisuutta, muuttaa lajikoostumusta ja johtaa perustuotannon laskuun voimakkaimmin kuormitetuissa lähteissä. Kunnostus parantaa lähde-elinympäristön laatua vähentämällä metsäojien aiheuttamaa pintavesivaikutusta palauttaen pohjavesivaltaisen hydrologisen tilan. Lähdekunnostusten myötä lähdesammaleet runsastuvat ja pohjaeläinyhteisön rakenne palautuu luonnontilaisten lähteiden kaltaiseksi, vaikka kunnostuksista on kulunut vasta muutamia vuosia. Väitöskirjan tulokset osoittavat, että ihmisen toiminta voi aiheuttaa muutoksia lähde-ekosysteemien rakenteessa ja toiminnassa ja lähteiden luontainen palautuminen häiriöstä on hidasta. Lähde-elinympäristöjen kunnostus vaikuttaa lupaavalta suojelutoimenpiteeltä metsäojitusten vaikutusten vähentämisessä, mutta lähteiden säilyttäminen monimuotoisena ja suojelullisesti arvokkaana luontotyyppinä edellyttää pohjavesivarojen hallinnan ja tilan suojelun tehostamista.