Effects of fire on peatlands globally are reasonably well documented, however studies of fire effects on tropical peatlands are limited. Specifically, the influence of fire on the biogeochemistry of tropical peat organic matter (OM) is not well understood and this study is the first to investigate this topic. Peat samples from undrained and degraded (drained and burnt) peatland in Central Kalimantan, Indonesia were analysed using novel chemical techniques. Short-term (one month post-fire) effects on peat OM composition were determined using Pyrolysis-Gas Chromatography/Mass Spectroscopy (Py-GC/MS), allowing for detailed molecular investigation. Results revealed significant compositional differences between burnt and unburnt peat pyrolysates including, dominance of recalcitrant aromatic- and aliphatic-derived compounds in pyrolysates from burnt peat, while those from unburnt/undrained peat contained greater contributions of labile compounds including derivatives of lignin and polysaccharides. At one month-post fire, pyrolysates from the upper 5 cm of peat showed that almost all polysaccharides (0.1±0.1%) and lignin-derived compounds (0.8±1.2%) were depleted, although these compound classes were relatively concentrated in subsurface peat (5-50 cm). Charcoal was a significant fraction of the upper 5 cm up to one month post-fire, but none was detected in significant quantities deeper in the peat column (5–50 cm). One-month post-fire, the burnt peat was hydrophilic in the upper 5 cm but retained its inherent hydrophobic character at greater depth. Similar to fire, peat drainage also reduced OM diversity i.e. the number of identified pyrolysis products. Peat pyrolysates from a drained unburnt site were dominated by aliphatic components (41.5-70.8% in the upper 50 cm). Thus both fire and drainage result in alteration of peat OM composition. The effects of fire were, however, short-lived (persisting up to 1.5 years post-fire), implying that peat OM composition can exhibit some recovery over a relatively short time period. Fire frequency had no significant influence on peat OM composition; thermal alteration occurred during the initial fire with no further modification during subsequent fires. The implications of these results for peatland carbon cycling and post-fire ecosystem recovery are discussed.

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Blanket bog habitat is a globally scarce resource and as a result is amongst the most important of British vegetation types in an international context. The habitat supports four Annex 1 bird species including golden eagle (Aquila chrysaetos) as well as red grouse (Lagopus lagopus) which is only found on heather moorland habitats and provides an important food source for golden eagle. The habitat is a Biodiversity Action Plan habitat with a target to restore 845,000 hectares of degraded blanket bog by 2015. At least 190,000 hectares of blanket bog habitat have been planted with conifer plantation, mainly Sitka spruce (Picea sitchensis), which is unlikely to mature until 2020-2030. This thesis explores the potential for restoring blanket bog, to provide habitat for red grouse, through the removal of immature Sitka spruce plantation. Three different tree clearance techniques are considered in terms of impact on the developing vegetation plant community. . The most cost effective method of clearance, in situ chipping using an excavator mounted flail, is investigated in detail; in particular the effect of wood-chip depth on changes in wood chip decomposition, plant colonisation, plant community development and vegetation structure. Monitoring and experimental data were analysed using multivariate methods including Principal Response Curves, Detrended Correspondence Analysis and Redundancy Analysis, and univariate methods including linear mixed effects and spatio-temporal models. Restoration of blanket bog vegetation is clearly achievable within a relatively short timescale that is dependent on the size of the trees and hence depth of wood chip. Plant community recovery following in situ chipping of trees (yield class 10) that are 20, 25 and 30 years old is predicted to take 7,9 and 10.5 years respectively. Vegetation structure is linked to plant community, with the cover and age of Calluna vulgaris being particularly important. As a result it seems likely that suitable red grouse habitat will be achieved as the target blanket bog plant community is reached.

Water levels in restored wetlands are often managed through pump drainage via an integrated network of open ditches. The aim of this thesis is to evaluate P dynamics in the sediment water component of a ditch that is managed to control the water level in a recently restored (from agriculture), seasonal wetland in south west England. Comparisons are made with a neighbouring agricultural ditch that lies in the same catchment. It was clear that pump drainage provided a source of P to the wetland ditch from the wetland, particularly in the dissolved form.

The Uplands are very distinctive environments for their habitats, wildlife, land use, and management history. They mostly support heather communities and organic soils; their functioning is intrinsically linked to management practices (heather burning, draining and grazing). Recent habitat losses in the uplands have shown a need for their protection. This study focuses on the consequences of heather burning on peat soil characteristics in the Pennines. Two areas of research were investigated: (1) the modifications of the organic matter characteristics and input of black carbon (BC) to soil as a result of heather burning, and (2) the potential alteration of the soil accumulation rate due to fire regimes. The use of 13C NMR spectroscopy of soil organic matter has shown none of the structural changes usually observed for vegetation and soil affected by fire (e.g. increase of aromatic C), possibly indicating insufficient number of successive fires for changes to be noticeable. Instead, the changes were related to the degree of soil decomposition. A laboratory controlled burning experiment estimated low charcoal production from heather «1% vegetation biomass), representing a potentially low input of aromatic C and BC in soils. BC analyses of soil samples did not show any direct increase of BC content in soil either immediately after the fire, or at longer fire rotations (i.e. every 10 and 20 years). Rather, the BC content in soils is thought to originate from fossil fuel combustion. Dating techniques e1oPb), chronological indicators (total Pb, stable isotopes), and their comparison with external references to assess the soil accumulation rate indicate possible overestimations of the values. In this particular context, the validity of the 210Pb technique is questioned. The alteration of the signal in soils could be due to a volatilisation and redeposition of 210Pb during the fire. This needs further investigation.

Peatlands are globally-important carbon (C) stores, representing approximately one third of the terrestrial C pool. These C stores are now becoming increasingly vulnerable to rising temperatures, as well as land-use changes. Release of C from peatlands, either as the greenhouse gases CO2 and CH4 or as a result of erosion, constitutes a significant potential feedback to global warming. Despite their importance, there remains a large amount of uncertainty concerning the size of peatland C stores - a result of the small-scale spatial heterogeneity in peat depths and plant communities that exists within peatlands. Quantifying spatial variation in plant and soil microbial communities - the biological sources and sinks of C in peatlands - is necessary in order to reduce uncertainty concerning the spatial variation of peatland ecosystem functions. We characterised ecologically and hydrologically distinctive peatland landforms in a UK blanket peatland, determining associations between plant and soil microbial communities and differences in ecosystem functioning between landforms, as well as the contributions of individual landforms to overall ecosystem functioning. Peatland landforms supported distinctive soil microbial communities. Eroding areas and gullies were hotspots for CH4 fluxes and had higher winter global warming potentials than intact blanket peat. A simulated 10% expansion of eroding areas resulted in a loss of C equivalent to 1000 years of C sequestration by the blanket peatland, emphasising the importance of considering individual landforms when assessing peatland ecosystem functioning at the landscape scale. Our approach represents a novel combination of targeted field survey, robust image classification techniques and geostatistics, which could be transferred to other peatlands. The research papers presented in this thesis contribute to our current understanding of the importance of biological diversity for peat land C dynamics, and will establish a theoretical and methodological framework to improve predictions of peatland ecosystem functioning in response to future change.

The aim of this study is to produce high-resolution multi-proxy records of hydrological change, spanning the last c. 250 years, from nine ombrotrophic peatlands across the north of Ireland. The results provide important insights into the nature of recent climate change in the region. To quantify hydrological change, a combination of established proxy indicators are utilised, including testate amoebae, plant macrofossils and humification analysis. Reconstructions of water table change from testate-amoebae assemblages are undertaken using a transfer function previously developed for the north of Ireland. Chronological control is provided via tephrochronology and Spheroidal Carbonaceous Particle (SCP) analysis, supplemented by AMS 14C dating. Two important regional crypto-tephra's, the Hekla 1947 and Hekla 1510 tephra layers, are used to enhance the age-depth models. A new intermediate Hekla tephra layer is also described at six sites which is inferred to be sourced from the Hekla 1845 eruption event, from which tephra deposits have only previously. been established in Orkney and the Faroe Islands. The bog surface moisture records from the nine sites show a high degree of similarity, with synchronous changes occurring at all sites. Allogenic climate forcing rather than internal peatland dynamics, is thus suggested to be. driving the inferred hydrological changes. A phase of cool and wet conditions predominates in all the records from c. AD 1750 until the late 1800's/early 1900's, probably reflecting the end of the Little Ice Age (LIA). A phase of rapid drying is then recorded, although the timing of the onset varies locally between sites, it is prominent at all sites from c. AD 1940. The testate amoebae based records of hydrological change are validated through statistical comparisons with instrumental climate datasets from the region. Strong correlations are observed between the hydrological records and summer temperatures, and to a lesser extent summer precipitation, indicating that it is the interaction of summer seasonal temperature and precipitation which drives peatland hydrological change in the regional peatlands. Comparisons with other observed climate proxy records from elsewhere in northwest Europe suggest the recent drying in the peatlands from the north of Ireland is part of a climatic shift with wide spatial extent, although the exact timing shows minor variations. The acquisition of multiple intra-regional records preliminarily suggests that smaller bogs and those in lower topographic settings appear to be more sensitive to hydrological change than larger bogs and those in upland settings. This study thus contributes to the wider understanding of the character and impact of recent temperature/precipitation change on Irish peatlands and provides important baseline data for examining the response of future climate change on the region's peatlands.

Headwater streams are important habitats, unique in their heterogeneity and biodiversity. they are considered significant for the functioning of whole river systems. Many headwater systems. such as those in the temperate and sub arctic northern hemisphere, drain peat dominated catchments, a habitat that is increasingly threatened by climate change, acidification and pressures from an array of land management practices. Together these impacts are resulting in the widespread degradation of peatlands and it is hypothesised that stressors could severely impact streams draining these systems, causing shifts in macro invertebrate community composition and alterations to functional process rates. However, there is a lack of information on the exact impacts of these stressors to peatland streams and, furthermore, limited knowledge of these ecosystems in their intact state. Thus, the overarching aim of this work is to improve understanding surrounding the impacts of stressors to peatland streams and to contextualise this research with an improved knowledge of the dynamics of intact peatland streams. This work focused on streams originating from blanket peats in the UK, which form important headwaters of many major UK rivers, and had four main objectives. 1) Develop a holistic understanding of an intact peatland stream through intensive assessment of physico chemistry, macroinvertebrate communities and three functional processes (algae accrual, plant litter decomposition and whole stream metabolism) using both a longitudinal survey and intense seasonal monitoring. 2) Assess the impacts of two catchment-scale drivers of change in peatland habitats (rotational heather burning and erosion) on stream ecosystems, examining physicochemistry, macroinvertebrates and ecosystem functioning across fifteen streams. 3) Examine gradients of sedimentation associated with environmental change and land management using streamside mesocosm and reach experiments. 4) Consider the mechanisms that elicit a change in physicochemisty, macroinvertebrates and ecosystem function by considering interrelationships and advancement of conceptual models. The interdisciplinary approach used in this thesis allowed a novel assessment of the spatiotemporal variability of peatland stream ecosystems and for the first time hig~lighted alterations in both macroinvertebrate communities and ecosystem functioning along the stream length and across seasons in an intact peatland stream. Increases in macroinvertebrate abundance, primary production and community vi j b respiration were observed with increasing distance downstream and with increasing catchment size. These parameters, along with algae accrual and leaf litter decomposition rates, also showed strong seasonal patterns, decreasing in winter and amplifying in summer. Variations in these parameters were driven predominantly by increases in temperature, photosynthetically active radiation (PAR), suspended sediment concentrations (SSC), discharge and dissolved organic carbon (DOC). Erosion, and to some degree rotational heather burning, were found to impact physicochemical variables, with total oxidised nitrogen (TON) and SSC displaying increased concentration.s in impacted catchments. Associated shifts were found in macroinvertebrate communities, with amplified abundance in eroded catchments driven by increases in ' more sediment tolerate taxa, such as Chironomidae and Oligo chaeta. Streams draining eroded and burnt catchments also displayed lower numbers of sensitive Ephemeroptera, Plecoptera and Trichoptera taxa. Functional parameters did not reflect these changes in chemistry and biota, but there were clear differences between the fifteen individual streams. Experiments undertaken in streamside mesocosms and stream reaches showed impacts of organic sedimentation across several levels of ecological organisation. Increased benthic sedimentation led to declines in macroinvertebrate abundance, shifts in - species composition and increased sediment respiration rates. Short term influx of organic sediment in reach based experiments caused significant increases in the downstream drift of macroinvertebrates during nocturnal periods, however, these streams were quick to recover to pre-experiment drift rates and benthic communities were not affected over the period of the experiment. These influx events produced a rapid and severe decline in GPP measured though whole stream metabolism rates, This body of research highlights peatland streams as unique and heterogenic systems but also as systems that are sensitive to anthropogenic stressors at both the catchment and reach scale, These habitats have intrinsic importance, supporting diverse macroinvertebrate communities, are significant for the modulation of carbon and are good indicators of the condition of the surrounding catchment. Thus, this work emphasises the need for restorative measures and sustainable management in peatland habitats that considers the streams they support. In addition, this work furthers knowledge of the baseline conditions in these systems and increases understanding of the use of functional processes as ecological indicators in peatland..streams.