The use of intertidal habitats by Grey Plovers, Pluvialis squatarola, and Curlews, Numenius arquata, was studied on Seal Sands in the Tees estuary, north-east England during the three winters 1975-78. Birds were uniquely marked with combinations of colour rings to obtain information on the behaviour of individuals throughout and in successive winters. Grey Plovers arrived on the estuary from July to February, giving rise to peak numbers in February, but left mainly in March and April. Thus periods of stay by individuals varied markedly, M contrast most Curlews arrived in late summer and left in spring. Consequently most individuals were present for similar periods, and the number on the estuary remained constant through the winter. However, the number of Curlews feeding on Seal Sands fell to a minimum in mid winter when some moved to feed on the fields. Both species showed a high percentage return rate to the estuary in successive winters. During each tidal cycle individuals changed their feeding sites in predictable ways. For any one bird the pattern was constant over periods of several weeks or months, and sometimes repeated in successive winters. In both species, four basic patterns in use of space could be identified. These were distinguished by: i) whether one or more than one feeding site was used during a tidal cycle, and ii) whether or not a feeding site was defended. The strategy employed on a particular site could be predicted from two characteristics of that site: i) its period of exposure, and ii) the rate of drainage of the substrate. It is argued that these characteristics determine the availability of Nereis diversicolor, the main prey of both bird species on Seal Sands. Simple models based on the supposed activity and depth distribution of Nereis on different sites explained much of the variety in use of space shown by individual Grey Plovers and Curlews both during a tidal cycle and during a winter. However the models were inadequate to explain the detailed components of foraging behaviour observed. Also, variability in the foraging responses to changes in Nereis availability was considerable, both between individuals and between days for the same individual; this raises doubts over the validity of studies based on "average" birds. Curlews show marked sexual dimorphism in bill length. This influenced the pattern in use of space employed by individuals. Most long-billed birds remained on the mudflats all winter, but many short-billed individuals (i, e. males) fed upon the adjacent pastures, particularly in mid winter when Nereis was most likely to be buried out of reach of their bills.

A study was carried out on the chemistry and vegetation of two streams containing elevated levels of heavy metals. In neither stream had the presence of these metals prevented the development of an algal flora, though species numbers were low in comparison with uncontaminated streams. The algal biomass was high in both streams, probably due to the lack of invertebrate grazers. Green algae were dominant. One of these streams, a highly calcareous mine effluent in Northern England (Durham code no. 0097), was studied throughout its annual cycle. Concentrations of heavy metals accumulated by the dominant algae (Mougeotia spp.) were equated with the physical and chemical properties of the water. Zn was supersaturated in the stream water (6.84 mg 1 (^-1) at pH 7.85); this was shown to be the major factor which influenced Zn accumulated by the algae. Samples from the other stream, a smelter tip seepage in South-East France (Durham code no. 3026), were available from an earlier visit. This stream contained extremely high levels of heavy metals (Zn = 3840 mg 1(^-1); Cd = 345 mg l(^-1)) and was dominated by the green alga Hormidium rivulare. Ten strains of green algae were isolated from these two streams and were shown to be resistant to Zn in the laboratory, probably as a result of genetic adaptation. Environmental factors which were likely to be affecting Zn toxicity were investigated for isolates of the dominant algae. Mg reduced Zn toxicity in both streams and may have an important role in the development of resistance by these algae. Field levels of Cd did not influence algal growth at field levels of Zn. The role of carboxylic acids in algal Zn resistance was investigated but could not be established. Accumulation studies suggest that Zn resistance by green algae involves internal detoxification of the metal and not exclusion.

Bryophytes are rarely used as a food source by any animal species, but the genus Tipula (Diptera, Tipulidae) contains some of the few insect species able to feed, and complete their life-cycle, on bryophytes. Vegetation particle volumes ingested by larvae of eleven Tipula species increased only marginally between instars and not to the extent expected from the rate of growth of body mass. Early and late instars within a species frequently ingested similar sized particles. The overall efficiency of digestion of vegetation particles was low and similar between the four instars of each of the eleven species. Generally, the only method by which later larval instars can obtain a higher proportion of nutrients is by feeding on a larger number of smaller vegetation particles and not by ingesting large particles. In feeding choice experiments, Tipula confusa preferred moss species from woodland habitats, whereas Tipula subnodicornis did not show an overall preference for either woodland or moorland moss species. Tipula subnodicornis also showed a less extensive hierachical preference/avoidance than Tipula confusa for the ten moss species investigated. The moss species Campylopus paradoxus and Sphagnum papillosum accumulated Pb(^2+) ions and Zn(^2+) ions to high concentrations. There was some evidence that Tipula subnodicornis larvae were deterred from feeding on these mosses with high levels of introduced heavy metal ions. Tipula montana was able to thrive and complete its life-cycle in Britain at lower altitudes than had been previously thought. Individuals of this species show a combination of one-year and two-year life-cycles at Waskerley Common. The feeding methods employed by Tipula species can explain why some of them have remained as consumers of bryophytes.

The nutritional condition (fat and protein reserves)of shorebirds was studied, mainly at Teesmouth and Lindisfarne, north-east England, during the non-breeding season. Normal patterns of fat and protein storage are similar in most coastal shorebird species. Fat reserves rise to a peak in midwinter. Fat is stored rapidly before both spring and autumn migrations. Protein reserves (measured as pectoral muscle size) remain steady during winter. Protein reserves increase before spring migration, but not before autumn migration. Most shorebirds regulate both fat and protein reserves during winter. Plovers (Charadriidae) have larger fat and protein reserves than Sandpipers (Scolopacidae). However rocky-shore species carry smaller reserves than species feeding on soft sediments. Interspecific differences are related to morphology, foraging behaviour, habitat use and winter movements. First-year shorebirds carry similar sized or larger reserves than adult conspecifics. Catabolism of nutritional reserves was studied during two periods of severe winter weather in north-east England. Reserves were catabolised faster by species that normally carried the largest regulated reserves. In eastern Britain some Redshanks cannot regulate their fat and protein reserves even during mild winters. Possible reasons are discussed. The condition of shorebirds that had starved to death during severe weather is examined. Redshanks, first-year Oystercatchers, inland species)and shorebirds that return early to breeding grounds are most at risk. Recovery of nutritional condition after starvation is examined. In addition to seasonal variation, differences in the size of regulated fat reserves occur in different wintering grounds. Total lean weights in relation to wing-length as a measure of body size are used to examine whether similar seasonal and latitudinal differences in protein reserves of shorebirds exist. Plovers have larger pectoral muscles than Sandpipers but similar total lean weight (measured in relation to body size). During winter, lean weights are lower in several equatorial and southern hemisphere areas than in northern temperate regions. Seasonal and latitutinal changes in lean weight are discussed in relation to periods of environmental stress.

This geographical investigation of land use and water use in the Esfahan region of Iran is concerned with the consequences of Man's managenent, development and exploitation. In the introductory chapter, the context of the research, the reasons for the selection of the Esfahan region as a study area and the main themes of the thesis are discussed. A systematic analysis is presented of the environmental characteristics, principally the geology, geomorphology, pedology, climate and hydrology of the area. The history of Man's adaptation to these constraints is reviewed; the contemporary patterns of land use and water use are examined; and the data and the statistical and cartographical analyses employed in the study of the patterns are discussed. Local variations of water resource practice, agriculture and rural population are elucidated. The effects of urban expansion and industrial development upon the region's water balance are considered.

1. The plant ecology of re-vegetated peat cuttings in ombrotrophic mires was investigated to elucidate factors having a major influence on the vegetation, with the aim of formulating management guidelines for the rehabilitation of such areas for nature conservation. 2. Most of the investigations were carried out at Thorne Moors, a cut-over derelict raised bog near Doncaster, S. Yorkshire. 3. The vegetation of the wide range of abandoned peat cuttings present at this site is described. Particular attention was paid to re-vegetated peat cuttings within an area comprising a series of cuttings, baulks and canals abandoned about 1920, now a proposed National Nature Reserve. Successional, hydrological and chemical factors and processes important in determining the distribution of vegetation were investigated. 4. Stratigraphical investigations show that some species which recolonized the abandoned peat cuttings (e. g. Sphagnum imbricatum and S. magetlanicum) have disappeared from the site since 1920. They have been replaced by species which were not major components of the undisturbed mire (e. g. Sphagnum recurvum and S. fimbriatum). 5. The distribution of the vegetation in peat cuttings principally reflects the height of the water table. Hydrological studies have also shown that the methods used to maintain the water table in the proposed National Nature Reserve (dams in ditches and drains and peat baulks), a virtually isolated peatland block, are effective. The peat of the baulks appears to have an extremely low hydraulic conductivity which may be a result of drainage.

1. Revegetation trends in abandoned peat workings indicate that peat cuttings are generally too dry for spontaneous re-establishment of raised bog vegetation. The latter was restricted to small flooded peat pits which had recolonised 'hydroserally' to support floating rafts of bog vegetation. 2. The water storage capacity of cut-over bog surfaces is low compared with undisturbed bog and blocking drains in a peat field at Thorne Moors, S. Yorks, was insufficient to prevent water-table instability. Experiments suggest this may severely inhibit Sphagnum growth. Lagoons may increase water storage on a bog surface and facilitate development of raised bog vegetation as floating rafts. This 'hydroseral' approach may be necessary to restore raised bog vegetation to some areas. 3. Hydrochemical conditions of cut-over sites may differ significantly from undisturbed bogs with implications for Sphagnum growth. Water samples from a peat field at Thorne Moors were comparatively acidic and contained comparatively high concentrations of most major ions (particularly NH4 and SO4), except phosphorus. Moderate nutrient enrichment is unlikely to adversely affect Sphagnum and additions of phosphorus to flooded peat pits significantly increased its growth. In solution culture, low pH (3.0-3.5) was sub-optimal for Sphagnum growth, but the use of CaCO3 to reduce acidity in the field had a toxic effect. 4. Sphagnum recolonisation may be limited by availability of propagules in cut-over areas. Experiments indicate that deliberate re-introduction encourages Sphagnum raft development, which is pioneered by aquatic species that regenerate more prolifically from fragments than intact gametophytes. Sphagnum rafts are encouraged in shallow water (< 5 0cm) and pools of small area. Numerous management options exist physically and chemically assisting raft development.

The Scottish Borders fens represent an important group of British fen sites. Despite their small size many of these fens support various rare plant communities and nationally and locally rare plant species as well as a wide range of species characteristic of wetland habitats. This study has demonstrated the importance of management history, site chemical conditions and site size and morphology in the vegetation development of the Scottish Borders fens. 2. Sixty-eight sites were included in a general survey. The vegetation at these sites was systematically recorded. Site features (vegetation rafts, springs, drains), surrounding land-use, gross peat stratigraphy and measurements of pH and electrical conductivity of the fen water were also recorded. A subset of contrasting sites was selected for detailed investigations into site chemical conditions and peat fertility, peat stratigraphy and the development of vegetation rafts. The quadrat data were analysed using a range of multivariate classification procedures. One classification was selected as the basis for the description of Scottish Borders fen plant communities. Twenty-four plant communities and variants are described representing rich-fen, poor-fen, bog, tall herb fen, fen meadow and swamp habitat types. The Scottish Borders fen plant communities were compared to existing comprehensive classifications of British fen vegetation. 4. The impact of marl and peat extraction at each site was investigated using documentary, visual and stratigraphic evidence for disturbance at each site. The status of each site was determined (cutover, partly cutover, un-disturbed) and this was related to the development of the present vegetation. Most of the Scottish Borders fens have been cut for peat or marl to some extent. However at some sites the peat stratigraphic sequences represent un-modified peat development since the late glacial. The efficiency of drains, strength of springs and basin morphology are important factors determining the development of vegetation over former peat and marl cuttings. 5. Site chemical conditions show much variation. The intensity of the surrounding land-use is positively correlated with peat fertility at the edges and water inflows of sites. The main axes of floristic variation correspond to the variation in base-richness of the fen water and fertility. There was no simple relationship between chemical variables and the occurrence of different plant communities. 6. The vegetation has developed as a quaking raft over fluid peat at many sites. Two Sphagnum dominated plant communities are confined to vegetation rafts. Their occurrence is determined by the inundation of the vegetation surface with base-rich water, the depth of the fluid peat beneath the raft and the degree of isolation of the vegetation surface from telluric water input. Where the vegetation has developed as a raft over the entire site the thickest rafts are found in the central areas. The mechanisms of central raft thickening are thought to be influenced by differential fluctuation of the water table relative to the vegetation surface across sites.

Previous experimental investigations (Grime & Curtis 1976; Hillier 1984), and long term climatic monitoring (Rorison et al 1986a,b) have revealed the frequent occurrence of drought during the summer period in calcareous grassland on the south-facing slopes of limestone dales in the Peak District of North Derbyshire, Northern England. The main objective of the studies in this thesis was to examine the role of drought as a determinant of the characteristics of one selected calcareous grassland system at Tongue End in Millersdale. Particular attention has been given to the interaction of drought with soil heterogeneity and mineral nutrient stress. Efforts have been made to differentiate between mechanisms of drought tolerance and drought avoidance, and this has allowed some assessment of the contribution of diversity in morphology, life history and physiology to the maintenance of species-richness in the vegetation at the site. Three complementary methods of investigation were adopted; (1) analysis of spatial patterns by grid sampling of the field site. (2) comparative study of 17 component species in standardized environments. (3) synthesis of plant communities in turf microcosms simulating certain aspects of the Tongue End habitats. In the final chapter (Chapter 8) an attempt is made to integrate results from the observations and experiments described in previous chapters. Evidence from the investigation suggests that on the south-facing slope at Tongue End, floristic diversity is maintained by naturally occurring phenomena, in which drought and low nutrient status interact with soil depth and rock exposure. These factors are responsible for high seedling mortality, gap creation and spatial heterogeneity. The hypothesis is formulated that (1) the species -rich community established on the south-facing slope at Tongue End contains an assemblage of plants most of which are attuned to both regular predictable disturbance and chronic nutrient-deficiency. (2) drought interacts with the mosaic in soil depth and rock exposure within the studied site; species with the potential to develop deep root-systems are locally prominent in circumstances where there is access to continuously moist subsoil.

As a consequence of our advancing knowledge of the impact of trace elements in environmental and biological systems there is increasing need for quantitative analytical techniques to accurately, sensitively and rapidly determine a wide range of trace elements in environmental samples. Since their emergence in 1975 microwave digestion techniques have revolutionised conventional approaches to sample digestion and have rapidly gained widespread acceptance as an effective method of sample preparation. This thesis describes how a number of novel on-line microwave digestion techniques have been developed, characterised and applied to the digestion of a range of environmental matrices which have proved time consuming or troublesome to digest by conventional techniques. A variety of batch open focused microwave digestion methods have been developed and utilised for the analysis of a range of environmental samples including tea leaves, seaweed and sediment samples. The techniques were optimised to determine a range of trace metals including Al, As, Ba, Ca, Cr, Cu, Fe, K, Mg, Mn, Pb, Ni, Ti, V and Zn and in each case were successfully validated by the analysis of suitable certified reference materials. These techniques demonstrated a number of advantages over conventional methods including less reagent usage, less contamination and substantial time savings. Speciation studies have been a focus for this work and have included the evaluation of an acetic acid microwave extraction method for the extraction of tributyltin, dibutyltin, monobutyltin and triphenyltin from sediment samples prior to analysis by high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). In addition the speciation of arsenic in biological samples was addressed by the development and evaluation of an on-Une microwave digestion technique. This enabled the speciation of arsenobetaine (AsBet), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and inorganic arsenic following their separation by HPLC. Decomposition was achieved by microwave digestion and followed by pre-reduction with L-cysteine and detection by hydride generation-atomic absorption spectrometry. Simple modification of the technique also facilitated the determination of total arsenic. In addition the total reducible arsenic species (inorganic arsenic, MMA and DMA) were determined directly by on-line pre-reduction-HG-AAS. The results obtained were in good agreement with the certified values for the reference materials NRCC DORM-1 (dogfish muscle) and TORT-1 (lobster hepatopancreas). The on-line microwave digestion approach was further developed for the determination of the total mercury content of solid environmental samples. This involved the combination of an on-line microwave digestion and a bromide/bromate oxidation reaction to facilitate complete oxidation of the organomercury species in slurried biological samples. Following this approach detection could be performed by cold vapour-atomic fluorescence spectrometry, giving a limit of detection of 13 ng l-1. In addition a batch method in which samples were digested with a mixture of hydrogen peroxide, nitric acid and sulphuric acid was developed and studied using temperature profile measurements. Both methods were successfully validated by analysis of the certified reference materials NRCC DORM-2 and PACS-1 (harbour marine sediment).