Fen Areas Research Articles

Establishment of helophytes in the course of fen restoration

Abstract. In two fen areas of northeastern Germany, different techniques of re‐introduction to establish reed‐bed species in formerly intensively used, species‐poor, grasslands, after rewetting, were studied under three hydrological regimes (permanent inundation, temporary inundation, border irrigation) with the aims (1) to establish peat‐forming vegetation and (2) to enhance species richness.Establishment was successful for nearly all species investigated under all hydrological variants. There were differences between individuals sown and those which had been planted. Wet, but not inundated soil linked with vegetation gaps create ‘safe sites’ which enable successful germination and seedling establishment. The survival rate for both planted and sown individuals was generally high, with the exception of Cladium mariscus, Eupatorium cannabinum and Phragmites australis Recommendations for restoration management include the establishment of the following successful species: Carex acutiformis, C elata and C paniculata to establish peat‐forming vegetation; Iris pseudacorus, Lysimachia vulgaris, Lythrum salicaria to enhance species richness.

Species density of phanerogams and bryophytes in Dutch forests

In Dutch forests the species density of vascular plants ranges from 1 to 61 species per 300 m2. The vascular plant species density is high in the coastal dunes, southern Limburg, river valleys, and fen areas. With the exception of southern Limburg, these areas constitute the Holocene part of the Netherlands. Low species densities occur in the sandy centre of the country. To a large extent, the areas of high species density of vascular plants follow the main river valleys. The bryophyte species densities range from 0 to 21 species per 300 m2. High bryophyte species densities occur mainly in the sandy centre and in the north-eastern part of the Netherlands. The highest species densities occur in fen woodlands and derelict coppices. Bryophyte species density is low in the coastal dunes and the very young woodlands in the recently reclaimed areas (polders). The species density contour maps of vascular plants and bryophytes in the Netherlands have little in common.

Availability of organic and inorganic phosphorus compounds as phosphorus sources for Carex species.

Inorganic phosphates (ferric phosphate, calcium phosphate and aluminium phosphate) and organic forms of phosphorus (inosito) hexaphosphate and β-glycerophosphate) were tested as phosphorus (P) sources for the growth of three Carex species from fens differing in productivity- and nutrient availability. Aluminium phosphate and β-glycerophosphate were equally effective sources of P for all three Carex species as KH2 PO4 , which was used as a control treatment. Phosphorus from ferric phosphate and calcium phosphate was also taken up bv Carex acutiformis Ehrh., a species of high productivity from eutrophic fen areas, but not by the other two species. Only Carex lasiocarpa Ehrh., a species from P-limited fens, showed a higher P-uptake when grown with inositol phosphate than in the second control treatment without P. The P-source also affected, with differences between species, the biomass allocation to the below-ground plant parts and the area of absorption surface of the roots. The mobilization of organic sources of P by fen Carex species found in the present study might be an important factor in the P dynamics of fens because of the high contents of organic P in the fen peat soils where these species grow. In the same way, the utilization of inorganic sources of P can play a relevant role in the P-cycle in these systems where the discharge of ground water rich in ions can lead to the fixation of P into inorganic compounds. However, the differing abilities of the various Carex species to mobilize P from P-pools does not explain clearly their preferential presence in different fens in relation to the P-availability.

Changes in the extent and fragmentation of heathland and other semi-natural habitats between 1920–1922 and 1987–1988 in the llŷn Peninsula, Wales, UK

Habitat modification is assessed over a period of 20th century agricultural expansion in the Llŷn Peninsula, a coastal district on the western oceanic fringe of Britain. Habitat area data were derived from vegetation maps produced by surveys in 1920–1922 and 1987–1988. These are compared to assess the extent and nature of habitat change and degree of fragmentation. There was an overall depletion of 3 629 ha (44%) of semi-natural habitat, mostly due to conversion to agricultural grassland in low-lying areas. The major reductions were in dry heathland (1 500 ha, 51%) and especially in wet heathland (1738 ha, 95%), and there were also declines in the areas of scrub, fen and sand dune habitats. There appear to have been temporary fluxes in some vegetation types, especially wet grassland and bracken, and local gains have also offset losses in deciduous woodland. In many cases, habitat erosion has been accompanied by diminution in patch size, and there were fewer large areas of semi-natural habitat in the 1980s. Implications for nature conservation are discussed, and it is suggested that the larger surviving patches should be a focus for priority protection. Possibilities for habitat redevelopment are considered.

Modelling ecologically sustainable economic development in a region: a case study in the Netherlands

This paper addresses the relevance of the notion of sustainable development in a regional context and the use of models for regional sustainable development policy. First, the notion of sustainable development is discussed by linking socio-economic and ecological elements. In a spatial context an often neglected but relevant concept is regional sustainable development (RSD). Its relationship with both the global concept of sustainable development and sustainable use of resources is discussed. The use of models for sustainable development in a regional context is investigated. All potential models integrate economy and ecology: a description of economic processes, ecological processes and their interactions; and an inclusion of socio-economic and ecological indicators in the policy evaluation. Only dynamic models are considered, as they are regarded to be the most relevant class for addressing issues of sustainable development. It is argued that scenario and simulation models are most appropriate on a regional level, as here the level of detail in describing the economics and ecology is fairly balanced. Finally, a case study is presented for the Peel region, an area in the Netherlands, where presently agriculture causes considerable damage to groundwater, forests, and protected fen areas due to intensive cattle farming, irrigation and drainage. Several relevant development scenarios for RSD planning are developed, and the model analyses for each of them are reviewed from the viewpoint of RSD.

Breeding waders and their conservation on the wetlands of Tiree and Coll, Inner Hebrides: K. B. Shepherd & D. Stroud, Wildfowl, 42, 1991, pp 108–117

Breeding wader populations on a range of machair and other wetland biotopes on the Hebridean islands of Tiree and Coll were surveyed in 1987 and 1988. Six species breed, five of them (Lapwing, Redshank Oystercatcher, Ringed Plover, Dunlin and Snipe) in nationally important numbers. Habitat selection was investigated on nine sample survey sites, and extrapolated results indicate that a total of 6020 pairs of waders bred on Tiree, and 1330 on Coll. Several wetland and machair habitats held large numbers of breeding birds of particular importance were small areas of marsh and fen, wet machair, Phragmites beds, coarse wet pasture and old decaying runways set in areas of dry machair. The extent of European machair has been surveyed for breeding waders in the last five years. Tiree and Coll, together with the southern isles of the Outer Hebrides, hold internationally important populations, and are important in maintaining the range of several species within the British Isles (as required by international legislation). Agricultural operations, specifically drainage and intensification of grassland management, could be damaging to currently prime wader habitats. As well as protection of key areas, long-term conservation of these populations would be achieved by support for traditional forms of crofting which, over past centuries, has created the agricultural landscape on these islands.

Conservation of rare plant habitat: Insights from the recent history of vegetation and fire at crystal fen, Northern Maine, USA

Crystal Fen in north-central Maine has become well-known as a locality with numerous rare plants. Recent observations of apparent drying and an increase in abundance of woody vegetation in the fen have led to concerns that an adjacent railroad bed and drainage ditch may be causing changes that threaten the habitat of several rare and interesting plant taxa. A description of these changes comes from analysis of (1) aerial photographs dating from 1938 to the present; (2) characteristics of the present vegetation, including the age of living woody plants; (3) evidence of fire on the fen; and (4) the fossil-pollen and charcoal stratigraphy for the past 200 years from an area of the fen that is becoming increasingly wooded. Results indicate that during much of its history the fen may have been at least partially wooded, except in the area that is wettest and most open today. Construction of the railbed in 1893, and the passing of cinder-producing steam locomotives along the tracks thereafter, apparently promoted expansion of fen vegetation by impeding drainage and by igniting occasional fires that reduced the abundance of woody stems. Thus, the extensive open habitat where populations of some rare plants occur is, in fact, an artificial result of human activities. Recent drier conditions post-date the construction of a drainage ditch in 1937 and the introduction of diesel-powered locomotives around 1950, which largely eliminated the ignition of fires and allowed the re-expansion of woody taxa over most of the fen. This trend represents a partial retreat to natural conditions. The study demonstrates that (1) rare plants occur in a variety of habitats (open, lightly forested, and heavily forested) at Crystal Fen, suggesting that these populations would be best served by maintaining such habitat diversity; and (2) past human disturbance led to expansion of open areas, which is the habitat most suitable for some of the rare taxa. In the future, both open fen areas and overall habitat diversity could be artificially enhanced using a variety of management practices including cutting, prescribed burning, and manipulating drainage to maintain a mixture of vegetation types.

Response of the fen violet, Viola persicifolia Schreber, to different management regimes at Woodalton Fen National Nature Reserve, Cambridgeshire, England

The fen violet Viola persicifolia has decreased rapidly in Britain during the last century as a result of drainage and habitat destruction and it is now listed as an endangered species. Data are presented for five years' monitoring of populations existing under contrasting management regimes at Woodwalton Fen National Nature Reserve. This is the beginning of a long-term study which aims to identify management regimes which will allow the retention of healthy populations at Woodwalton, and which could be used to maintain or re-establish healthy populations elsewhere. The maintenance of open fen areas with few competitive species is important for persistence of the fen violet. Natural disturbance (e.g. from falling tress) and a high and fluctuating water table have probably provided this in the past. Annual grazing or mowing regimes may maintain open areas but also encourage competitive monocotyledons.

Factors Affecting Recruitment from the Seed Bank of Sedge (Cladius mariscus) Dominated Communities at Wicken Fen, Cambridgeshire, England

This paper attempts to identify factors which account for variation in the species composition of standing vegetation in four Cladium mariscus dominated areas of Wicken Fen, a wetland nature reserve. It was assumed that either the species composition of the seed banks, or the factors affecting recruit- ment from the seed banks, would vary. This distinction would help explain the ecology of fen succession and help in conservation management. Neither the species composition of the seed banks nor nutrient availability in the peat showed significant differences. However, differences were found in the probability of flooding, light intensity at ground level, and in peat surface mois- ture and temperature regimes. The nature of the standing vegetation appeared related to two factors: (1) the presence/absence, and timing of the management practice of mowing and harvesting, and (2) the probability, frequency and dura- tion of winter and spring floods as suggested by Godwin & Tansley (1929) model. An elaboration of that model suggests that the dense canopy created by a pure stand of the non-deciduous perennial Cladium mariscus creates a micro- environment inimical to germination of other species. As the habitat dries, or following the mechanical removal of the canopy by harvest, the ability of the Cladium mariscus to maintain the dark, damp, cool ground-level micro-climate is reduced, the rate of recruitment from the seed bank is increased, and the species richness of the standing vegetation is increased. This suggests that if the habitat is to be preserved the present mowing regime for carr control should be re- evaluated.

Status of aquatic macrophytes in an undrained area of fen in the Norfolk broads, England

The aquatic macrophyte vegetation of dykes and pools in an area of undrained fen in Broadland, Norfolk, is analysed and described. Three main types of vegetation have been identified, an Elodea-Potamogeton crispus community, a Ceratophyllum-Stratiotes community and a Utricularia vulgaris community. The first two normally occur near the land margins of the fens and the last mainly on deep peat in the central areas. Most luxuriant macrophyte growth was observed at the fen margins where levels of nitrate-nitrogen, derived from land drainage, were higher (both in the water and sediments) than in the central fen areas. Preliminary comparisons are made of some chemical characteristics of the water and sediments of sites with a well developed macrophyte vegetation with others where macrophytes are very poorly developed, or completely absent. Sites poor in macrophytes had higher levels of sodium in the water and sediments and also more strongly reducing sediments than those with a rich macrophyte vegetation. However, measured levels of dissolved inorganic nitrogen and soluble reactive phosphorus were lower, or not significantly different. A recent reduction in the amount of Stratiotes aloides in some dykes may possibly be related to nutrient impoverishment rather than enrichment.

The macrophytic vegetation of Loch Urigill and other lochs of the Ullapool area

Summary From the 15 lochs examined at altitudes between 9 and 267 m in western Sutherland and Wester Ross, a few areas of tall fen (with Hippuris, Sparganium erectum, Osmunda etc.) survive to indicate its potential distribution. Predominant grazed fen comprises patches of short Juncus articulatus and Carex nigra. Reedswamp is scarce, being dominated by Eleocharis palustris, Carex lasiocarpa and Schoenoplectus lacustris and, rarely, by Phragmites and Sparganium erectum. Floating-leaved vegetation was only encountered twice. Submerged vegetation to water depths of at least 1 m consists in the main of sparse Lobelia-Littorella with Juncus bulbosus, typical of the prevailing stony shores in every loch. Extensive Isoetes lacustris meadows may occur beyond that, with Potamogeton praelongus or P. perfoliatus stands in waters of alkalinities over 0·45 m-equiv 1-1, reaching depths of 3 m in Loch Urigill. Loch Urigill is unusual in having dominant Isoetes at a water alkalinity of 0·76 m-equiv 1-1 along with abundan...

CHEMICAL, PHYSICAL, AND LAND-USE INVESTIGATIONS OF ORGANIC TERRAIN

Chemical and physical properties of selected organic soil samples were studied in relation to the chemical status of the associated ground water. Soil analyses included standard chemical analyses, fibre content, bulk density, particle density, hydraulic conductivity and water retention properties. In situ water chemical analysis included temperature, conductivity, dissolved oxygen and pH. Laboratory measurements of dissolved Ca, Mg, N, K, Si, NO3, F and Cl are also reported. The results are interpreted with reference to the surface expression and overall terrain morphology of the sampling area resulting in the formation of different peat types and associated vegetation. Physical and chemical data indicate a relationship between degree of decomposition and magnitude of various parameters. The distinction between bog and fen areas in terms of the level of dissolved electrolytes permits the prediction of the nature of the material comprising the organic soil. The distinctive properties of organic soils are discussed in terms of some use constraints imposed by the nature of the material in the context of afforestation of this terrain type.

The peasantry and the English revolution

Large sections of the English peasantry were prospering in the sixteenth and early seventeenth centuries. But they suffered a reversal of their expectations in the 1620s and 1630s. They were subjected to higher rents and entry fines and to the loss of some of their common rights and common pastures, especially in the fen and forest areas. Agrarian discontent led many peasant to oppose the king and royalist landlords in the civil war and to support parliament and the parliamentarian party.

THE DISTRIBUTION OF TESTATE AMOEBAE (RHIZOPODA: TESTACEA) IN SOME FENS AND BOGS IN NORTHERN ENGLAND

1. Eleven bog and fen areas (330 samples) in Northumberland, Westmorland and Lancashire were examined for testate Protozoa, providing a series of habitats with a pH range 3·2-7·0. 2. In fen conditions, above pH about 5·0, a group of 25 species occurred regularly and almost exclusively. The commonest species were Quadrula symmetrica, Cyphoderia ampulla, C. trochus var. amphoralis, Lesquereusia spiralis, Nebela collaris sensu stricto, N. lageniformis, N. penardiana, Euglypha rotunda, E. ciliata, Pontigulasia bigibbosa, N. tubulosa, N. galeata and Sphenoderia dentata. 3. In bog areas (pH 3·2-4·6), Amphitrema stenostoma, A. wrightianum, Difflugia bacillifera, D. bacillariarum, D. brevicolla, Nebela carinata and possibly Placocista spinosa were characteristic of pools. 4. In acid hummocks, wet areas were dominated by Amphitrema flavum and Hyalosphenia papilio, with Nebela tincta, Arcella catinus, N. militaris, Assulina muscorum, Heleopera rosea and Euglypha strigosa frequently present. Drier areas were dominated by N. tincta, Assulina muscorum, Arcella catinus, Heleopera sylvatica complex, Euglypha strigosa and N. militaris, with Trigonopyxis arcula and Bullinularia indica. 5. A number of species occurred over a wide range of habitats, but usually showed some ‘preference’ for either bog or fen conditions. 6. Fen areas contained more species (Mean 30·1) than areas with pH less than 5·0 (Mean 18·9). 7. The distribution of Testacea in northern England is similar to that recorded in other parts of Europe, but the types of association proposed by Harnisch (1927) are of only limited application.

The Corixidae (Hemipt.) of some Danish lakes

1. As bays in lakes gradually fill with vegetation, the succession in soft water may pass from Phragmites to Carex and then Sphagnum, an oligotrophic succession; or, at the other extreme, found in hard-water lakes or near the mouths of rivers in soft-water lakes, from Phragmites and Typha to Salix and Alnus, a eutrophic succession. There are successions of intermediate type. These changes are accompanied by changes in the species of Corixidae. 2. In the hard-water Danish lakes studied, Phragmites is the main reedswamp plant and it persists long after the accumulation of its remains has raised the bottom above the average level of the water. Eventually it is replaced by Alnus. The weight of the trees, probably coupled with the rotting of the mat of Phragmites roots, depresses the soil level and forms pools. 3. Corixa striata is found in the outer parts of reed-beds; C. linnei near the landward edge of wide reed-beds; C. sahlbergi in pools in the Alnus woods. Evidently these species succeed one another as fen develops from open water. 4. C. falleni was found at many stations but not often in abundance. The records suggest that optimum conditions for it are outside reed-beds, in places where organic matter accumulates on the bottom. C. fossarum was found abundantly in two places where open water was due to human excavation in areas of fen. 5. General conclusions about Corixid successions are summarized in the diagram on p. 000 6. What has hitherto been known as Corixa striata is split into two species. The new one, which is the only one found in Great Britain, but which has also been recorded from France, Italy and Sweden, is named C. lacustris. C. lacustris is broader and rounder posteriorly than C. striata (fig. 4), and the pale lines on its corium are wider, particularly at the ends (fig. 3), but the variability of both characters renders difficult the certain distinction of some specimens by means of them. The outer row of palar pegs curves in suddenly at the inner end in C. striata, but not in C. lacustris (fig. 3). The only character on which the two species can be separated easily is the shape of the right and left genital forceps (figs. 5 and 6).