Species rich upland hay meadows are of high biodiversity importance and are internationally rare. There is increasing interest in restoring botanically diverse meadows in the uplands but little is known about the role of invertebrates. The purpose of the project was to investigate the role of (i) slugs as seedling herbivores and (ii) pollinators in affecting the plant communities. Research has revealed important interactions between invertebrates and plant life history traits with implications for grassland restoration. Slugs are known to affect plant communities by the selective seedling removal of more acceptable species, although few studies have considered their impact at restoration sites. A glasshouse feeding trial showed the acceptability of seedlings of different meadow plants to slugs is influenced by plant defensive properties. Field investigations of slug population densities identified a negative correlation with increasing levels of agricultural improvement. This relationship was partly driven by the increase in grass abundance cover in agriculturally improved meadows and may be influenced by the anti-feedant properties of silica-rich grass leaves. A 3-year mesocosm study found evidence that slugs are an important selective force affecting seedling recruitment and community composition. The selective seedling removal of the hemi-parasite and keystone species Rhinanthus minor was a key finding of this study. Use of Scanning Electron Microscopy showed the leaf surface of R. minor to be characterised by a diverse assemblage of trichomes which may play an important role in anti-herbivore defence. Parallel declines in pollinator and insect-pollinated plant populations have raised concerns that smaller populations of important pollinator groups such as bumblebees may be reducing seed set by plants. Survey work showed upland hay meadows to be an important forage resource for common and rare/scarce bumblebees. Bumblebees visited a small number of forage plants, most notably R. minor, Trifolium species and Geranium sylvaticum. Pollen supplementation tests did not find significant evidence that reproductive output of R. minor and G. sylvaticum (a gynodioecious species) was limited by pollination services. Testing of a new system to record pollinator visitors to flowers proved highly effective and offers the potential to significantly reduce time and labour input into the study of plant-invertebrate interactions. The project has shown that invertebrates are an important functional group affecting the success of plant species in hay meadows. The findings provide new and important information to the industry in developing management prescriptions for restoring upland hay meadows and other botanically rich plant communities.

To better understand boundary layer processes and improve hydro-meteorological models it is essential to quantify contributions from different land surface types to the total energy exchange. The effects of urban areas must be represented not only within densely populated towns and cities, but also at the regional scale. A multi-scale field campaign designed to investigate the exchange of energy and mass over suburban land surfaces was undertaken in Swindon, UK. Observations of heat, water vapour and carbon dioxide fluxes suggest Swindon behaves much like a natural landscape during summer, whereas anthropogenic activities dominate in winter. Eddy covariance data collected exhibit broad trends that are in accordance with studies in other locations, whilst marked seasonal contrasts build a more complete picture of the suburban environment. Scintillometry, a ground-based remote sensing technique, estimates turbulent heat fluxes at larger scales (0.1-10 km), comparable to model grids. The conventional single-wavelength method provides the sensible heat flux. Additionally, use of a unique millimetre-wave scintillometer in conjunction with an infrared scintillometer enabled both sensible and latent heat fluxes to be determined. These results represent the first observations of large-scale evaporation over urban areas using scintillometry. The technique is shown to perform reasonably well and recommendations are made for future research. Advantages include spatially integrated fluxes, particularly useful over heterogeneous surfaces where a mosaic of different land cover characteristics can lead to contrasts in surface-atmosphere exchanges. These observations are used to investigate the controls on evaporation and the behaviour of fluxes at different scales. Particular attention is given to seasonal variability, land cover and the availability of surface moisture and energy. Rapid evaporation directly after rainfall and dew are also explored. With improved understanding of the suburban climate, more accurate predictions can be made regarding the impact of land use development, environmental management schemes and climate change.

Sand dunes are important habitats which support a wide variety of flora and fauna. Dunes are under threat from issues such as climate change and scrub encroachmnent. This project examined the impact of conservation grazing by domestic cattle (Bos primigenius) as a management tool for maintaining designated dune systems in 'favourable condition' by reducing scrub cover and generating a species rich sward, whilst accounting for the potentially confounding effect of grazing by naturally occurring wild European rabbits (Oryctolagus cuniculus). GIS analysis of dunes in Northern Ireland suggested that they underwent substantial temporal change from the 1950s to 2010 with loss of open areas of bare sand replaced by increased areas of grassland but most notably scrub and woodland. A factorial experimental approach revealed that grazing by domestic stock reduced vegetation height and biomass whilst controlling the coverage of scrub species such as Ulex europacus (Gorse). Rabbit grazing had 2.6 times the effect of cattle grazing on sward height maintaining a well cropped sward. Rabbit abundance on dunes exhibited significant spatiotemporal variation that fluctuated by orders of magnitude making their impact difficult to predict. Seasonal grazing by cattle had no effect on plant community composition but year round grazing by rabbits skewed plant composition towards unpalatable species, particularly in close proximity to their warrens creating spatial variation in plant community structure. Input of nutrients via the deposition of dung by cattle and rabbits had no discernible· effect on soil pH or nutrient flow including nitrogen, carbon or other trace elements. A review of studies that examined scrub control techniques suggested that effective scrub management is best when using mechanical or manual clearance followed by the immediate application of herbicides with on-going grazing to prevent re-establishment. Recommendations are made for further research and management of designated sand dunes sites throughout Northern Ireland.

Aberffraw is a lkm wide and 3km long transgressive dune field on the Isle of Anglesey, North Wales, that extends inland along a northeast-southwest trending valley from a southwest facing beach, Traeth Mawr. The prevailing wind is from the southwest and both the parabolic dunes and the vaUey within which they lie are subparallel to the prevailing wind. The dune field at Aberffraw includes two foredunes ridges and three rows of active parabolic dunes. At the landward end is a lake, Llyn Coron, which has been formed by the dunes migrating up the valley and damming the river, Mon Ffraw. Rates of parabolic dune migration, calculated from aerial photographic analysis using a new linear fit method for compound dune forms, range from a minimum of 0 m1yr to 3.6 mJyr, with an average migration rate of 1 m1yr. Ground Penetrating Radar (GPR) was used to identify sedimentary structures in the subsurface of the two foredune ridges, four parabolic dune ridges and the associated interdune areas. Surveys at 100 MHz and 200 MHz allowed the resolution of both the gross dune field stratigraphy (bounding surfaces, erosion surfaces) and the smaller sedimentary structures (e.g. cross-stratification, foresets, cut and fill troughs), together with the water-table and basement. Interpretation of the GPR profiles used a combination of the radar facies technique and a radar sequence boundary stratigraphic approach to construct relative chronologies for sections of the stratigraphy. Detailed intersecting GPR surveys by Llyn Coron revealed a relative chronology of six sand packages younging successively towards the NE, bounded by erosion surfaces representative of relic lake beds. Large landward dipping erosion surfaces are interpreted as incursions by the lake, with a raised water-table resulting from highstand phases initiated by dune damming. Smaller troughs and planar based scours are interpreted as periods of deflation to a lowered water-table associated with lowstand phases of the lake. Prograding stacks of landward dipping foresets are interpreted as continued dune migration throughout these events. Hand augering was used to sample specific packages identified from the GPR profiles for Optically Stimulated Luminescence (OSL) dating to provide absolute ages for sand deposition. Samples were also acquired from the neighbouring site of Newborough Warren for comparison, and for radiocarbon dating. Quartz grains were dated using a single aliquot regenerative dose (SAR) protocol that allowed for sensitivity changes and monitoring of thermal charge transfer. Thirty-four dates ranged from AD 1281 for a 5 m deep sample to AD 1981 for a modern bleached sample, demonstrating good precision in contrast with the radiocarbon technique over this time scale. and confirming the relative chronology constructed from the GPR data. The OSL dates for sand movement at Aberffraw show good correlation with both local and regional temporal trends in sand movement for coastal dune areas in NW Europe, with a positive correlation between periods of sand movement and periods of increased storm frequency and severity associated with the North Atlantic Oscillation (NAO) and climatic deterioration during the Little Ice Age cooling event.

Exploring new terrestrial archives to investigate past climate and the resultant impact on ecosystems is key to assessing changing climate within large continents, where major records are limited. This study presents the first comprehensive geochemical investigation of clastic cave sediments, a previously under-explored field, demonstrating the effective use of caves as an environmental archive, and recovering useable records of moisture and vegetation regime within the complicated monsoonal system of South East Asia. Clastic cave sediments were recovered from a 2.4 m deep archaeological trench covering ~24 ka to ~12 ka within Hang Trong, Vietnam. Clay mineral, bulk carbon, pollen, terrestrial snail shells and plant-derived lipid biomarkers were analysed to provide a multi-proxy approach. No diagenetic alteration was found below 20 cm despite clay mineral and bulk carbon 013C analysis demonstrating microbial action and weathering of surface sediments. As previously observed in cave sediments, poor preservation lead to limited pollen recovery, however o13C values from CSIA and shell carbonate indicates C3 vegetation persisted around the cave during the last glacial maximum. The time-series 8180 record from recovered shells shows clear fluctuations corresponding to global climatic events including the LGM and Heinrich 1. It is hypothesised that these reflect moisture availability, with heavier isotopic values indicating drier periods. Most higher plant lipid biomarkers provide evidence for a stable forest composition, however a shift in n-alkane lipid from C31 to C27 can also be linked with the Heinrich 1 event. The warm Greenland interstadiall event is also expressed within the record by low 0180 shell values attributed to more available moisture and higher bulk o13C values, which indicate greater micro-organism action. Hang Trong's multi-proxy record adds to a growing body of evidence demonstrating the importance of global teleconections when assessing the impact of climate change on monsoons and local vegetation. The data collected here proves clastic cave sediments can hold valuable climatic proxies; something which is of especial importance as palaeoenvironmental archives rely on limited capture and preservation for long term environmental records.

No description available.

Arid mountain systems and their biological diversity are particularly vulnerable to changes in climate. The aim of this thesis was to evaluate climate variability and its impacts on ecological systems at different spatial and temporal scales, focusing on the Dry Puna ecoregion in the Central Andes, around the triple frontier of Argentina, Bolivia and Chile, and using a combination of climate data, data from remote sensors, and ecological surveys. I expanded on earlier generalized climatic trends by empirically assessing climate variability since 1980 with a larger set of weather stations at high elevation. I found no consistent temporal trends in temperature and rainfall, but high inter-annual variation in rainfall associated with El Niño Southern Oscillation (ENSO) effects. Climate and topography affected vegetation productivity (measured as the Normalized Difference Vegetation Index NDVI) in the Dry Puna in various ways. Primary productivity was overall low but higher in the High Plateau, under the humid influence of the Amazon. There was no significant temporal trend in productivity in the study area since 1980 and NDVI variability was chiefly driven by ENSO conditions (lower during El Niño years, with dry and hot summers). At a finer scale, vegetation types responded to low rainfall in different ways; tussock grasslands were the most affected by low rainfall; wetlands and scrublands the most resilient. The aridity of the Dry Puna also poses particular ecological limitations to animals. Using species distribution models and resource selection functions I showed that mesocarnivores coexist in this low productive ecosystem by selecting key resources at different degrees and scales, including free water, clusters of prey and refuge. The endangered Andean cat Leopardus jacobita, the most specialized, was also the most selective at finer scales and showed the larger spatial overlap with its preferred prey the southern mountain viscacha Lagidium viscacia. Using bioclimatic models at the continental level, I predicted that suitable habitats for Andean cats will decline under future scenarios of climate change by up to a third by 2080. Although 15% would still be represented within the current network of protected areas, there will be a dramatic decline in the northern reach of the species range. Given the dearth of earlier climatic and ecological studies in the Dry Puna, this thesis makes a substantial contribution to better understand the impact of climate on the productivity of this dry environment, and how threatened species may interact and respond to current and projected climate conditions.

This thesis aims to unpack the complexity of trajectories of land use change in semiarid Mediterranean agro-ecosystems - illustrated using findings from the Torrealvilla catchment in south-eastern Spain. The research looks at multiple dimensions of land use change and addresses the past, present, and future . It comprises of three key stages. Stage 1 quantifies land use change between 1956 and 2008, assesses the impacts on landscape fragmentation, and identifies important drivers of the detected changes. Stage 2 examines the linkage between farmer heterogeneity and the diversity of agricultural land uses in the studied landscape by developing a typology of farmers. It also investigates how farmers respond to future changes that potentially affect their farming and describes potential future trajectories of agriculture in the area and the implications for agro-ecosystem services provision. Stage 3 models the future trajectories of land use change for the studied landscape using two different approaches: Cellular Automata (CA) and Agent-Based scenario analysis. The research shows that over the past five decades the catchment has undergone significant changes with pronounced effects on landscape configuration. The changes involved three major trajectories (forest expansion, abandonment of rain-fed farming, and intensification) and were attributable to various interacting biophysical and socioeconomic drivers. The study differentiates six types of farmers according to the characteristics of their households and of their farm management. Different types of farmers are expected to pursue different land use directions with important impacts on future provision of agro-ecosystem services. Results from the final stage highlight a diverging future . "'To illustrate, while CA projection suggests scope for further expansion of irrigated farming, the agent-based scenario analysis indicates the opposite. Overall the thesis confirms that land use changes in Mediterranean agro-ecosystems are indeed complex entailing multiple, contrasting, and perhaps competing trajectories and are the manifestation of the interacting effects of various types of drivers. The thesis highlights conceptual and practical challenges in undertaking an integrated evaluation of land use change complexity. Future policy making should consider the various factors that are jointly shaping agricultural land use trajectories.

No description available.

Though the input of labile substrates into the rhizosphere by roots is known to promote decomposition of both soil organic matter (SOM) and surface litter, the presence of ectomycorrhizal (ECM) fungi living in symbiosis with plant roots has been shown to coincide with decreased litter decomposition rates in some systems. In a series of field experiments, techniques including forest girdling and soil trenching were used to exclude roots and ECM fungi in order to investigate the mechanisms controlling litter decomposition in forest soils. Soil trenching was carried out in combination with litter bag incubations, and measurements of soil CO2 flux in a 20 year-old Pinus contorta stand. The use of mesh in-growth collars allowed the influence of ECM fungal hyphae on litter mass loss, and their contribution to soil CO2 flux, to be established separately to that of roots. A specialised irrigation system allowed moisture effects caused by root/ECM hyphal water uptake to be investigated. Neither the presence of roots, nor ECM fungi had any influence on litter decomposition, and soil temperature was the only factor found to correlate with litter mass loss. The exclusion of roots and ECM hyphae led to increased utilisation of a simple substrate, 13C-labelled glucose. Results of incubations of four substrates, varying in structural complexity and nitrogen (N) content, suggested that the rapid utilisation of simple substrates by r-strategist microorganisms might be suppressed in the presence of ECM fungi. Though N content appeared to have a positive influence on substrate decomposition, the results were not significant. In contrast, when forest girdling was used in a nearby Tsuga heterophylla stand to exclude plant-assimilate C supply to the soil, a significant reduction in the rate of litter mass loss was observed. The results presented in this thesis indicate a potentially large role of ECM fungi in controlling decomposition in forest soils, and the mechanisms underlying their influence require further investigation.