Carex Arenaria Research Articles

Cryptoniesslia setulosa gen. et sp. nov.

Cryptoniesslia setulosa , found on decaying leaves of Carex arenaria in Devon, is described as a new genus and species of the Niessliaceae. No anamorph was observed in agar cultures derived from ascospores.

The clear-felling of sand-dune plantations: Soil and vegetational processes in habitat restoration

Sand-dune pine plantations often have little conservation value. This paper examines vegetation and soil changes following clear-felling, and management strategies for the restoration of near-natural sand-dune habitats. A common response to clear-felling is the rapid establishment of a weed community characterised in Britain by Senecio spp. and Chamerion angustifolium, which is associated with vigorous growth and high initial levels of available nutrients. This community may gradually be invaded and replaced by typical dune species; however, in older plantations with more litter the ruderal flora is often replaced by a bryophyte and lichen community, and a tendency towards pine Pinus regeneration and invasion by Betula spp. is observed. C. angustifolium, which is capable of efficient nutrient cycling, and Carex arenaria persisted as local dominants on these deep litter layers. This was associated with a phase of nutrient immobilisation. Needle-litter modifies the sand-dune soil by retaining nutrients and soil moisture. It inhibits germination from the sand-dune seed-bank and contains a seed-bank of ruderal species. Litter removal can accelerate the change to a near-natural sand-dune habitat. Although it may not be possible to restore the original dune flora following clear-felling a dune plantation, it may be feasible to create one which is very similar, or even to create a vegetation type not previously present at the site but still with greater value for conservation than a pine plantation.

Competition at Community Boundaries: Mechanisms of Vegetation Structure in a Dune-Slack Complex

A re-examination of the distribution of the dominant species in a series of dune and slack communities after an interval of 24 years revealed varying amounts of movement in the boundaries between the different vegetation types. Some boundaries showed no measurable differences in location while others had changed significantly. The most stable boundary was between the Carex arenaria heath vegetation of the dune tops and the Filipendula ulmaria-dominated community of the adjacent dune slack. This boundary coincided with the maximum winter flood-line which has remained stable despite increased flooding, as excess water decants into drier slacks to seaward (...)

Control of Bracken and the Restoration of Heathland. II. Regeneration of the Heathland Community

1. This paper describes the effectiveness of a range of bracken control and heathland restoration treatments (cutting, spraying with asulam, and seed sowing, in factorial combination) at a Calluna and a grass heath in Breckland over 10 years. 2. In the grass heath, 13 species were recorded during the 10 years, although in most plots two species were dominant: Festuca ovina which was sown, and Deschampsia flexuosa which colonized naturally. Festuca ovina rapidly colonized the seeded plots, but Deschampsia flexuosa appeared 5 years later. After 10 years D. flexuosa was co-dominant on many plots. 3. On the Calluna heath, 13 vascular and three bryophyte species were found. The sown species Calluna was found mainly on seeded plots, especially where the bracken was cut. Agrostis capillaris, Dicranum scoparium and Galium saxatile were most abundant on plots where the bracken was cut twice yearly. Other species appeared independent of treatment, reflecting low abundance, ubiquitous distributions, or clumped distributions. Two clonal species, Carex arenaria and Calamagrostis epigejos, invaded in large patches where cover of other heath species was negligible. 4. Most of the species colonizing the restored areas had higher Ellenberg nitrogenindicator values than the dominant heathland species, indicating that soil fertility may be too high for successful heathland restoration. 5. The results are discussed in relation to practical conservation management and vegetation dynamics.

The Population Biology of Plants with Clonal Growth: III. Analysis of Tiller Mortality in Carex Arenaria

(1) Tiller survival in the rhizomatous sedge, Carex arenaria, was studied in two sand dune-slack systems on Anglesey, North Wales. (2) Field plots were established in the mature, senile and slack phases of natural populations where half of the plots received a large application of NPK fertilizer. The tiller populations within permanent quadrats were mapped at intervals of 1 or 2 months for 16 months. (3) The application of fertilizer led to a large increase in the numbers of shoots that emerged for the mature and senile phases but only a modest increase for the slack phase. (4) Because of the complexity of the survivorship data gathered there was considerable difficulty in determining whether or not the apparent differences in cohort survivorship were statistically significant. (5) Therefore, tiller counts were analysed by a non-parametric method which did not require that individual tillers within the same cohort die independently of each other, nor that they have an equal probability of death in a given time interval. (6) Separate statistical models were fitted to the mortality data from both control and fertilized quadrats, so that the main features of the data could be described together with the variability that was present. The residual variation was much greater for the fertilized quadrats, due to the heavy fertilizer application greatly increasing tiller population flux. (7) The mortality rates for three of the five cohorts (April, June and September), in both control and fertilized quadrats did not differ greatly for the time intervals that they had in common but differed significantly from the mortality rates of the other two cohorts (July and January). The cohorts from the mature and senile phases had similar mortality rates except for the fertilized quadrats at one of the two sites. The application of fertilizer led to higher mortality for the mature and senile phases but this was not the case for the slack phase. (8) The mortality distributions of the fertilized shoots with time were of a different shape from those for the controls.

The Population Biology of Plants with Clonal Growth: II. The Nutrient Strategy and Modular Physiology of Carex Arenaria

The Population Biology of Plants with Clonal Growth: II. The Nutrient Strategy and Modular Physiology of Carex Arenaria

ECOPHYSIOLOGY OF THE SAND SEDGE, CAREX ARENARIA L. III. XYLEM TRANSLOCATION AND THE OCCURRENCE OF PATCHES OF VIGOROUS GROWTH WITHIN THE CONTINUUM OF A RHIZOMATOUS PLANT SYSTEM

SUMMARY The older shoots on the rhizome of the sand sedge have a lower waterpotential than the younger ones closer to the rhizome tip. The xylem translocation stream, that runs through the rhizome in accordance with the gradient in waterpotential from tip to base, could be demonstrated in translocation experiments with acid fuchsine dye and lead (EDTA) chelate. The occurrence of patches of vigorous growth within the continuum of a sand sedge plant system can be explained by the properties of the xylem translocation system of the plant.

Changes in the species composition in an area dominated by Deschamsia flexuosa (L.) trin. as a result of cattle grazing

When marginal agricultural lands are left idle, a vegetation type develops which is not adapted to grazing. If such vegetation is grazed, as has happened in Mols Bjerge (Eastern Jutland, Denmark), changes occur in the composition of species,whereby the dominants are reduced while the less frequent species increase. In Mols Bjerge the main means of plant dispersal is vegetative (horizontal, rhizome) and endozoic (dispersal) via cattle. However, dispersal is very slow. Species such as Holcus mollis and Carex arenaria are dispersed vegetatively, while dicotyledonous herbs (especially Pimpinella saxifraga and Campanula rotundifolia) are dispersed endozoically. It is suggested that areas rich in species should be grazed by cattle immediately before those poor in species if it is desired to assist immigration of dicotyledonous species.

ECOPHYSIOLOGY OF THE SAND SEDGE CAREX ARENARIA L. II. THE DISTRIBUTION OF14C ASSIMILATES

14C assimilates produced in a single shoot of a sand sedge plant proved to be translocated in the direction of the rhizome tip only. Labelled assimilates were found in all roots in the part of the plant system between the shoot administered with 14CO2 and the rhizome tip, in the youngest shoot and in the rhizome tip itself. The percentage of assimilates exported by the mature shoots proved to be 30–35%. The amount of assimilates exported by the youngest shoot decreased from 22% in a 1-shoot system to zero in the bigger plant systems. In the 5-shoot system also the export of the second youngest shoot started to decrease. In spite of the relatively great sink strength of the rhizome tip with regard to the assimilates exported by the nearby situated young shoots, the main source of assimilates for the rhizome tip proved to be the older shoots, lying at some distance. The ecological importance of this is that the rhizome tip will be able to cross unfavourable habitats, without the need for assimilates from the newly formed shoots in those habitats.

Structure and permeability of the epidermal/hypodermal layers of the sand sedge (Carex arenaria, L.)

During the normal course of development in the root of sand sedge (Carex arenaria), many of the cells in the central cortex degenerate to form an extensive aerenchyma. The epidermis and multi-layered hypodermis become heavily suberized and only remain attached to the stele by a few, thin, radial files of cortical cells that have not autolyzed. These changes make it possible for epidermal/hypodermal sleeves to be isolated so that their permeability can be determined. The coefficient of diffusive permeability for tritiated water is of the order of 20 nm s−1, while the permeability coefficient for self diffusion of labelled phosphate and calcium is approximately 5.0 and 4.0 nm s−1 respectively. These values are approximately 200 (water) and 500 (phosphate and calcium) times lower than similar determinations made on isolated sleeves of onion roots. The outer layers of the mature root ofC. arenaria are thus extremely impermeable: any significant absorptive function has been lost at the expense of a protective role provided by the modified cortex for the vascular stele.

The Population Biology of Plants with Clonal Growth: I. The Morphology and Structural Demography of Carex Arenaria

(1) The structural demography of the rhizomatous sand sedge, Carex arenaria L., was studied in two dune-slack systems on Anglesey, North Wales. Carex arenaria was chosen as a model species, since any study of rhizomes is easier when plants grow in loose-textured substrates such as dune sand. (2) A distinctive architectural feature of this plant is the longevity of the rhizome system. Clonal growth by C. arenaria results in subpopulations of shoot modules (tillers) which may be separated into distinct growth phases in the field (juvenile, adolescent, mature, senile and slack). (3) Field plots were established in the mature, senile and slack phases of natural populations; half the plots received a massive nutrient application of NPK fertilizer. The shoot populations within permanent quadrats were mapped at frequent intervals. (4) Recruitment and death of tillers of C. arenaria occurred throughout the year, although the birth and death rates were both highest during the summer. The spring and summer cohorts were generally larger and had lower survivorship. Most of the flowering shoots were derived from shoot cohorts produced during the previous spring and summer. (5) Life expectancy of tillers differed little between the mature and senile phases, but was considerably less in the slack phase. (6) Nutrient application increased the density of shoot populations in the mature and senile phases, but even more striking was the speeding-up of the flux of shoot turnover. The mortality risk within individual cohorts was increased by adding nutrients. Survivorship curves were generally negatively skewed (Deevey Type I) though some maintained a constant death risk (Deevey Type II). Added nutrients changed the age structure of the shoot population to a more juvenile-dominated state. (7) The flux in the shoot populations in the slack phase was sluggish in response to applications of nutrients, probably because this phase was associated with abundant vegetation of other species which absorbed the applied nutrients.

ECOPHYSIOLOGY OF THE SAND SEDGE, CAREX ARENARIA L. I. GROWTH AND DRY MATTER DISTRIBUTION

SUMMARY The growth and the dry matter distribution of sand sedge plants were followed in time by means of an indirect estimation method. This method enabled us to calculate the time courses of both the growth of the whole plant, and the growth of the individual shoots from measurements of the shoot length, the number of leaves and the length and width of the leaf laminae only. The growth rate of each individual shoot decreases with time. In the primary shoots 1–7 the amounts of dry weight added during the experiment were equal to each other, indicating a higher growth rate for the younger shoots. A comparison of dry weight production and increase in dry weight of shoots gave the amount of dry matter import or export by those shoots. The dry matter production in the tip part of the rhizome (two shoots, a shoot bud, the rhizome parts and the roots attached to them) proved to be far too small to maintain the growth of the non-assimilating tissue in this part. There must be a considerable export from the older plant part towards the rhizome tip region. It should be mentioned that the results presented here are similar to those obtained from 14C studies. Because of its simplicity the method we used would be very suitable for use in field studies.

Plant Life on East Anglian Heaths: being Observational and Experimental Studies of the Vegetation of Breckland

THE interesting studies of vegetation at Breckland, East Anglia, which Dr. E. Pickworth Farrow has been publishing in the Journal of Ecology, have now been gathered together and published, with additional matter, in book form. This work provides the most definite and striking data as to the effects produced by rabbits in determining the nature of the vegetation. Thus their influence is traced in the degeneration of Calluna heath to grassland and in the prevention of natural regeneration of woodland. Interesting notes are provided on wind effects upon Calluna in sandy soils and upon the water supply in the soil as a determining factor in the type of vegetation of the soils at higher levels at Breckland, but in the main this work is characterised by the manner in which it underlines the significance of biotic factors. Cases that may be cited, in addition to the rabbits, are the effect of the shade thrown by Pteris, notably by the dead fronds, upon the spread of Calluna, and the influence of the litter of needles below the pines upon the spread of Carex arenaria.