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In the past three decades, peatlands all over the world such as upland bogs, tropical fens, have been undergoing significant and rapid degradations. These degradations cause carbon loss and CO2 emissions, and also fuel climate change. In this research, I present three case studies on how space geodetic tools, especially Radar Interferometry (InSAR), can be used to monitor and to advance our understanding of the long-term surface changes in peatlands. First, I investigate the eroding extent and severity of upland UK peatlands using InSAR. Both short wavelength C-band and long wavelength L-band data are explored in this study. I detect a long-term peat subsidence rate of about 0.3 cm/yr, and 2 cm of decrease in peat height between 2002 and 2010. I also examine the coherence performance of C- and L-band over upland bogs. I find L-band data provides better coherence than C-band in upland bogs. Second, I use InSAR time series generated by L-band images to map the spatial and temporal subsidence of drained tropical peatlands in Sumatra, Indonesia. And based on InSAR-derived subsidence rate data, I estimate carbon loss or CO2 emission. Third, I assess the effectiveness of peatland restoration work in in Central Kalimantan, Indonesia using InSAR (L-band images). Restoration effects and impact factors are investigated by the spatial and temporal changes of peat height, which also provide useful information for guiding future restoration activities in this region. Overall, this research suggests that InSAR time series is feasible to monitor long-term peat height change in peatlands, provides new insights into the dynamic surface changes in peatlands, and helps to study the carbon loss and CO2 emissions from peatlands, and understand restoration effects.

1. Climate change is predicted to negatively impact ecosystems globally. Freshwaters are particularly susceptible, due to thermal and hydrological sensitivity and poikilothermic fauna. Such change may ultimately imperil ecosystems service provision. Adaptation schemes that limit ecological and economic impacts are therefore widely advocated. The major management action recommended for rivers is restoration of “buffer strips” of riparian tree cover, which can lower stream water temperatures, and should therefore protect thermally sensitive species, including economically important salmonid fish (Family: Salmonidae). 2. Despite thermal consequences being well-quantified, community-wide biotic responses to restoration remain unexplored. Such ecological consequences may ultimately govern the efficacy of this measure in protecting focal species, but there is limited evidence available from which to predict restoration outcomes and inform management efforts. 3. Using 24 upland streams, this thesis assessed ecological consequences of differential catchment tree cover on stream communities. Using surveys and experimentation, the project assessed the role catchment afforestation in mediating the importance of terrestrial resource subsidies to stream food webs, structuring macroinvertebrate communities, and supporting salmonid fish. 4. Several lines of evidence indicated that wider catchment tree cover controls the functional composition of stream communities, by mediating availability of terrestrial resources. However, buffer strips did not approximate the effects of wider broadleaf forest, and supported communities that were functionally indistinguishable from streams draining unafforested moorland. Unexpectedly, catchment broadleaf cover did not ultimately affect salmonid populations, contrary to expectations. 5. In combination, these results contribute to the understanding of land use effects on stream communities, and provide clear evidence needed to guide future management efforts. These findings suggest two distinct adaptation options: restoration of buffer strips should be able to confer benefits to fish populations, by offsetting thermal impacts without jeopardising food availability. However, re-instatement of wider broadleaf forest could potentially re-establish woodland stream communities.

In this thesis, two practical models for predicting the drag force exerted on flexible riparian vegetation under hydrodynamic loading have been developed. The models were formulated based on the results of a unique experimental data set that consisted of high resolution force-velocity and physical property measurements for twenty-one full-scale riparian trees, in both foliated and defoliated conditions. One of the models has then been used to numerically simulate the impact of riparian woodland on the flooding characteristics of a mid-catchment river site. Analysis of photographs and video footage of the trees from the experimental study during drag force testing allowed the frontal projected area to be determined, both in still air and as a function of flow velocity. The observed reductions in projected area and drag coe�cient with velocity were normalized using the projected area in still air to provide an empirical relationship between the ‘rigid’ drag coe�cient and area Reynolds number. The resulting drag force predictions were found to be accurate when properly calibrated against the vegetation under consideration. A second, more physically based model to predict the reconfiguration of flexible vegetation has been developed based on dimensional analysis of the relevant parameters, including flexural rigidity. The model utilizes a novel vegetative Cauchy number to determine the extent of the reconfiguration and has been shown to be more accurate than two existing drag force models. The model has also been validated against independent drag force data, demonstrating that it is applicable to vegetation of di�ering scale, morphology and flexibility. Serial and parallel optimizations of an existing two-dimensional hydrodynamic modelling code have enabled detailed numerical simulations of extreme flood events to be undertaken for a mid-catchment river site in Somerset, UK. The results indicated that riparian vegetation has a minimal impact on the downstream flooding characteristics, at least for the small site investigated herein. Significant reductions in key flow properties, namely velocity and bed shear stress, were however observed within the vegetated areas.

Lowland tropical peatlands can act as sinks and sources of carbon, interchanging greenhouse gases (GHG) with the atmosphere. Despite the importance of lowland tropical peatlands in the past, present and future global carbon cycle, uncertainties exists about the controls regulating the processes of carbon turnover. Therefore, this study examined different controls of carbon turnover, including abiotic, biotic and anthropogenic. For this purpose, six peatlands with different dominant vegetation were selected in the north western region of the Republic of Panama (9° 4' 16.06" N; 82° 6' 28.98" W). Two phasic communities were used as experimental models; Raphia taedigera palm swamps and mixed forest swamps with Campnosperma panamensis. A combination of in situ and ex situ experiments were performed between March 2010 and November 2012: i) ex situ respirometric assays were used to quantify differences in carbon turnover through the peat profile under different redox regimes, ii) litter bags experiments were used to investigate the effect of plant materials with distinct botanical origins on peat accumulation, iii) the effect of vegetation on greenhouse gases emissions was assessed with in situ and ex situ experiments and iv) land use change (LUC) was monitored to evaluate its consequences on the short term carbon turnover processes. Ex situ respirometric assays suggested that organic matter composition of peat plays a major role in controlling the potential CO2 and CH4 production. Under anaerobic conditions, the potential CO2 and CH4 production decreased with depth. The potential CO2 and CH4 productions in the surface peat layers of the anaerobic assays were 7 and 120 fold higher than those in deeper layers of the peat profile respectively. The change in redox regime affected the carbon turnover; the CO2 potential production in the surface layers (< 50 cm depth) increased 20 fold when exposed to aerobic conditions, whilst the deeper layers (> 50 cm depth) increased 47 fold. In contrast, CH4 production was reduced two orders of magnitude under aerobic conditions. Tissue types of R. taedigera and C. panamensis showed different in situ decomposition rates. Decomposition was significantly slower belowground than at the surface, reflecting the importance of the redox regime on the litter decomposition. Roots presented the lowest in situ decomposition rates among tissues both at the surface (R. taedigera: 0.59 ± 0.04 y-1; C. panamensis: 0.45 ± 0.01 y-1) and belowground (R. taedigera: 0.13 ± 0.01 y-1; C. panamensis: 0.17 ± 0.005 y-1). Macromolecular analyses revealed that roots and stems have similar composition to the peat material accumulated in deeper layers. Vegetation exerted a direct control on GHG fluxes from lowland tropical peatlands. In both ex situ and in situ measurements, fluxes of CO2 and CH4 varied with vegetation activity. In terms of CO2eq (Addition of mass flow of GHG, converted with the global warming potential of each gas), the agricultural LUC increased CO2eq emissions from the R. taedigera swamp at Cricamola by ca. 20 t CO2eq ha-1 y-1. At the pristine site, CO2, CH4 and N2O contributed with ca. 90, 9 and 1 % of the TCO2eq respectively. In contrast, in the anthropogenically impacted plot, CO2, CH4 and N2O contributed with ca. 29, 69 and 2 % of the TCO2eq respectively. Water table strongly influenced the carbon turnover. Under flooded conditions (water table at or above the surface; 0 to 0.15 m), the CH4 emissions were ca. 4 times higher in comparison with those where the water table was below the surface (−0.01 to −0.4 m). In contrast, CO2 emissions were ca. 1.5 times higher when the water table was below the surface. It was concluded that the interdependence of hydrology, peat composition and vegetation activity are the main factors controlling carbon turnover in the lowland peatlands of the north western region of Panama. This thesis has shown that fine scale alterations of these three factors can have large scale consequences, demonstrating sensitivity to perturbations and ease shift of lowland tropical peatlands from carbon sinks to carbon sources.

Peatlands are multiservice ecosystems: they are the largest terrestrial store of carbon in the UK, unique habitats which provide a home for internationally important species and managed for forestry, farming and game management and shooting. This makes understanding the impact of management practices on their ecology important if they are to be sustainably managed for multi-benefits. Fire has long been used to manage peatlands in the UK to improve grazing and habitat provision for livestock and game. The effect of fire on carbon cycling in blanket bogs is of increasing concern as greenhouse gas emissions from land use is now an important management as well as political issue. Gaps however, still exist in our understanding of the controls on greenhouse emissions from blanket bogs and the impact fire may have on them both directly and indirectly by modifying vegetation composition and environmental conditions. The main objective of this research was to assess the effect of fire on greenhouse gas emissions by measuring methane and ecosystem respiration after burning at blanket bog sites across Scotland for a period of up to 3 years and relating changes in fluxes with changes in vegetation composition and abiotic conditions. In addition, the response of the Sphagnum layer to burning was assessed by looking at the recovery of Sphagnum capillifolium in the field and in a novel laboratory experiment. The indirect effects of fire on methane emissions were further investigated by a laboratory experiment devised to test if high temperatures would be fatal to methanotrophic bacteria in the Sphagnum layer, reducing methanotrophy, and thus a mechanism for fire to increase methane emissions in the short term. The results showed that methane emissions and ecosystem respiration were not significantly different in burnt plots when compared to adjacent unburnt plots at each of the three sites studies. Methane emissions were only weakly correlated to the position of the water table and neither methane fluxes or ecosystem respiration correlated with measures of vegetation composition and above ground biomass. Methanotrophy in Sphagnum was found to be difficult to detect, with a high temperature treatment having no significant effect on rates of methane oxidation. S. capillifolium was found to respond to fire by growing new auxiliary stems if the capitulum was consumed or irreversible damaged physiologically by temperatures experienced at the moss surface, with surface temperatures around 400oC with a temperature residency time of 30 seconds on artificially dried samples the most damaging, but not lethal, treatment. These results suggest that low severity fires which only consume the canopy vegetation, not penetrating the peat and leaving the moss layer mostly intact, do not have significant effects on methane emissions and ecosystem respiration in the short and medium term. In addition, it suggests that S.capillifolium can, under certain circumstances, survive a fire with the characteristics of those studied here. These findings reiterate that best practice burning guidelines must continue to ensure that burning is only carried out on blanket bog when conditions are conducive to fires with the characteristics studied here, which had little effect on important components of the carbon cycle and are survivable by at least one of the most common species of Sphagnum.

Northern peatlands play an important role in the cycling of carbon (C) globally, and contain up to one third of the world’s soil C despite only covering a small percentage of its land surface (Gorham, 1991). Changes in climate and land use are increasing the vulnerability of these vast C stocks, by altering the conditions favourable for peat accumulation and therefore C sequestration. The establishment of wind farms on peatlands is increasing in the UK, as a result of the growing need for sustainable energy and the suitably high wind speeds that are typical to these upland ecosystems (Smith et al., 2014). There is limited understanding of the impacts of operational wind farms on their host ecosystems, but evidence to suggest that wind farms create microclimate conditions by altering ground-level temperature is increasing (Armstrong et al., 2014a; Baidya Roy and Traiteur, 2010; L. Zhou et al., 2012). The sensitivity of peatland C cycling processes to wind farm-induced microclimatic changes represents a considerable gap in knowledge. Further, the role that aboveground and belowground peatland communities have in mediating the effects of wind farm microclimates on C cycling processes remains unknown. By examining plant-soil interactions across a peatland at Black Law Wind Farm and under a range of microclimate conditions in the laboratory, this thesis aimed to investigate the influence of plant functional type (PFT) and microclimatic conditions on physical, chemical and biological peatland properties, greenhouse gas (GHG) emissions and litter decomposition. Results show that a PFT legacy in peat plays a mediatory role in the response of CO2 and CH4 emissions to microclimatic differences in temperature and water table. Mass loss of litter is primarily driven by PFT differences in litter quality, with interactions between litter types controlling decomposition of litter mixtures via non-additive effects, and interactions between litter types and PFT legacies in peat affecting the likelihood of home-field advantage and disadvantage (HFA and HFD) litter mass loss. This thesis demonstrates that the direct effects of microclimatic changes in temperature and water table are important drivers of peatland C cycling processes; however the indirect effects of microclimate change on plant community composition e.g. the relative proportion of PFTs could influence these processes to a greater extent. Examining the importance of PFTs in C cycling processes at wind farm peatlands is important in improving predictions of peatland C sequestration under future climate change scenarios, and in calculating the C savings achieved by land-based renewable technologies.

Estonian coastal wetlands are of international importance as they support characteristic biological diversity. Their limited extent and distribution mean that these wetlands are of high conservation concern, and as such have been identified as a priority in the European Union Habitats Directive. These wetlands are typified by a flat, extensive landscape, situated between the micro-tidal «0.02m), brackish Baltic Sea and a forest interior. Due to the low relief these wetlands may be under threat from sea level rise. This research consisted of four studies: (i) to determine and quantify the relationship between a range of coastal wetland plant community types, elevation and edaphic conditions. Results demonstrated that plant community distribution was significantly affected by micro-topography and edaphic variability. The majority of the plant communities were discernible in the field by elevation alone and elevation was found to be the factor that could distinguish the greatest number of plant communities. (ii) to determine an appropriate method of interpolating LiDAR elevation data and assess the use of LiDAR data in creating a static correlative model to determine plant community type based on elevation. Results showed that with dGPS calibration the model could accurately predict plant community location. Validation of the model in two further sites showed that the correlative model was able to predict plant community with almost perfect (K 0.81) and moderate agreement (K 0.53) dependent on the site. (iii) to determine sediment accretion rates to complete the dynamic model by analysing the level of radionuclides, 137CS and 210Pb, in discrete core sections. Results showed that during periods of greater storminess sediment accretion increased almost threefold. These sensitivity data were included in the dynamic correlative model. (iv) to assess the effects of sea level rise on plant communities in Estonian coastal wetlands under five sea level scenarios, two accretion rate scenarios and factoring in isostatic uplift rates. Results showed that local sea level will rise in some sites and decrease in others dependent on location and SLR scenario. This study has indicated that in many instances Estonian coastal wetlands will increase in extent in the future due to high rates of sediment accretion, particularly in a scenario with more frequent storms, and isostatic uplift. The study has shown that following validation, calibration and sensitivity analysis LiDAR data can be used to accurately predict plant community type in microtopographical ecosystems. The model developed in this study of Estonian coastal wetlands is likely to be transferable to other appropriate habitats such as tidal, estuarine, and floodplains wetlands.

Northern peatlands are an important component of the global carbon (C) cycle and have been a net sink of atmospheric C during the Holocene. Under current climate warming conditions, the future sink-source balance of these peatlands is uncertain. In particular, peatlands near the southern limit of permafrost are likely to be sensitive to changes in topography as well as climate. In order to predict how the sink-source balance may change, this thesis focuses on determining the generality of observed patterns of C accumulation in Northeastern Canada. The methodological approach in this thesis is unique. A total of 30 cores were taken from 9 peatlands located in 3 ecoclimatic regions along the North Shore of the Gulf of St Lawrence. This replication of records allows for climate-scale (allogenic) signals to be separated from the internal or local factors (autogenic), and for statistical testing of differences between regions and within sites over time. Trends in carbon accumulation rates (CAR) were analysed on three levels: (1) within individual sites along a hydrological or microtopography gradient, (2) between overall regions located along a climatic or permafrost gradient, and (3) over time on a multi-centennial scale. Lead-210 (210Pb) dating was used throughout the analysis to increase temporal resolution for the last 150-200 years of C accumulation. The method was thoroughly tested from preparation to analysis and found to produce reliable results, comparable with other dating methods. These dates were then used to develop combined age-depth models for longer-term context. Replicated records of 210Pb inventories and fallout rates were also used to address questions of deposition patterns and post-depositional mobility in peat profiles. Total inventories decreased with water table depth, with lichen hummocks having significantly higher inventories. One site also received significantly higher 210Pb deposition than the other two, as it is more sheltered from the Gulf influence. Recent carbon accumulation rates for the 150-year period for all microforms across all regions was 62.1 ± 4.4 g C m-2 a-1, and were highest for Sphagnum hummocks (79.9 ± 8.9 g C m-2 a-1) and lowest for dry lichen hummocks (42.7 ± 6.2 g C m-2 a-1). Patterns and trends at this scale were mainly driven by autogenic processes, including incomplete decomposition in the acrotelm peat. Models of peat accumulation related to acrotelm thickness were found to be overly simplistic, as carbon accumulation for intermediate microforms showed large natural variability driven by changing ecohydrological feedbacks, in part due to permafrost degradation at one of the sites. Over a multi-centennial scale, carbon accumulation rates were driven by a combination of climatic changes and ecohydrological feedbacks due to shifts in the microform configuration in response to permafrost degradation. Changes in carbon accumulation rates were detected and coincided with Little Ice Age temperature/solar minima (including the Spörer, Maunder and Dalton Minima), permafrost degradation since the 1950s, and recent climatic changes in the mid-1990s. Snow cover and exposure of sites and microforms were found to play an important role, rather than solely climatic variables. Rapid Sphagnum re-establishment in post-permafrost degraded features and increasing temperatures meant that carbon accumulation was highest for the northernmost site in the transect. Age-depth models using a combination of lead-210 and radiocarbon dates allowed for the calculation of carbon accumulation rates at a decadal resolution. While peat carbon sequestration is projected to increase in northern regions, the fate of peatland C near the southern limit of permafrost is complex. Future studies seeking to interpret recent changes should include multiple cores and consider both regional climatic and local ecohydrological drivers.

Calluna-dominated habitats, including dry heaths and peat bogs, provide important ecosystem services such as biodiversity, soil carbon stores and water supply. Climate change projections estimate drier conditions throughout their range, which could lead to increased wildfire activity. Such altered fire regime could induce a fundamental change to the ecology of Calluna moorlands and increase carbon emissions from their carbon-rich soils. The aim of this research was to understand how ecosystem response varies in relation to increased fire severity in Calluna heathlands and peat bogs. I completed experimental fires at two sites in Scotland, a dry heath and a raised bog, where I manipulated pre-fire fuel structure and fuel moisture content to achieve a gradient of fire severity and investigated the subsequent effect on post-fire vegetation regeneration and soil carbon dynamics. I found that drought increased fire severity in terms of ground fuel consumption and soil heating through increased flammability of the moss and litter layer. Substantially higher fire-induced ground heating was recorded when this layer ignited. When consumption of the moss and litter layer was extensive, post-fire soil thermal dynamics were altered and diurnal and seasonal thermal variation was higher, resulting in warmer soils that may lead to higher soil carbon emissions. Fire effects (ground fuel consumption, ground heating, changes in post-fire soil thermal dynamics) were much stronger at the dry heath than at the raised bog, likely due to ecohydrological differences between sites, i.e. thicker moss layer and deeper, wetter soil at the raised bog. For example, average fire-induced maximum temperatures at the soil surface at the dry heath increased from 31 degree C to 189 C due to drought, but at the raised bog they increased from 10 C to 15 C. Post-fire vegetation community composition varied in relation to the gradient of fire severity at the dry heath. Higher fire severity increased abundance of dominant ericoid species (Calluna vulgaris, Erica cinerea and Erica tetralix ) through improved substrate conditions (consumption of the moss and litter layer leading to bare soil), despite the fact that higher fire-induced soil heating hindered their regeneration. Short-term soil carbon emissions increased after burning due to a greater reduction in photosynthesis than in ecosystem respiration. Methane fluxes were negligible at the dry heath, but increased after burning at the raised bog, especially in warmer conditions. Generally, higher fire severity had little effect on soil carbon dynamics (ecosystem respiration, net ecosystem exhange, methane flux and dissolved organic carbon concentration), but higher autumn emission after higher fire severity at the dry heath and the important control of plant functional type cover suggest differences may become apparent in the longer term. This research advances our understanding of how an altered fire regime with higher fire severity could alter ecosystem functioning in Calluna moorlands and impact on its conservation value and belowground carbon stores. The work presented here can be useful to managers using burning as a land management tool, or who need to plan for wildfire occurrence in these fire-prone habitats, to inform strategies to accomplish a range of objectives, including conservation, protection of carbon stores and recreation, and to researchers interested in environmental change in Calluna moorlands. This research was funded by the University of Glasgow with support from the Centre for Ecology and Hydrology, the Ohio State University and Glen Tanar Estate.