Juncus Squarrosus Research Articles

Juncus Squarrosus (Juncaceae) in Romania: Its First Certain Occurrence and a New Plant Association for the Romanian Vegetation

Abstract This study confirms the first certain occurrence of Juncus squarrosus L., an Atlantic species, in the Romanian native flora. Characteristic plant communities with J. squarrosus occur in the Apuseni Mts (Western Romanian Carpathians). At these sites J. squarrosus has the southeastern limit of its European distribution. The identified plant communities with J. squarrosus in Romania are devoid of some Atlantic species present in Western and Central European communities and therefore are assigned to the Nardo-Juncetum squarrosi (Nordh. 1920) Bük. 1942 association. This plant community is a new syntaxon for the Romanian vegetation.

Climate, pollution and grazing drive long‐term change in moorland habitats

AbstractQuestionDwarf shrub moorland dominated by ericaceous plants is a distinctive, internationally important feature of northwest Europe, with its stronghold in Scotland. There have been major declines in its condition and extent. How has moorland composition changed within Scotland over the past ca. 35 yr and what is the role of climate change, pollution and grazing in driving these changes?LocationFive hundred and forty locations across Scotland, UK.MethodsWe used a long‐term resurvey approach to assess change across Scottish moorlands. We relocated plots sampled ca. 35 yr previously in alpine heath, dry heath, wet heath and bog, and recorded vegetation species composition. We assessed change in species group richness and cover and mean Ellenberg values between surveys, using paired t‐tests. We used CCA with variation partitioning and regression analysis to analyse the vegetation data with spatial data sets on climate, pollution and grazing, to assess the role of each driver in driving vegetation changes.ResultsSignificant diversity and compositional changes between surveys were found for all habitat types, particularly alpine heath. Significant associations were found with climate (many variables), pollution (N and S) and herbivore number (primarily deer). Species richness generally increased, but several specialist species declined in cover, especially those associated with higher altitude habitats (e.g. Arctostaphylos uva‐ursi, Salix herbacea and alpine lichens). Many of the most successful species are ubiquitous, e.g. the widespread grazing‐ and pollution‐tolerant graminoids Anthoxanthum odoratum, Juncus squarrosus, Festuca rubra and Nardus stricta and the generalist mosses Rhytidiadelphus squarrosus and Hylocomium splendens.ConclusionsDiversity and composition of moorlands in Scotland have changed significantly over the ca. 35‐yr period studied; the drivers of these changes are complex, with climate, pollution and grazing playing variable roles across habitats. The reduction in specialist species, homogenization of alpine heaths and declines in forb and lichen cover all represent negative changes in the biodiversity value of Scottish moorlands.

Biogeochemistry of uranium in the soil-plant and water-plant systems in an old uranium mine

The present study highlights the uranium (U) concentrations in water–soil–plant matrices and the efficiency considering a heterogeneous assemblage of terrestrial and aquatic native plant species to act as the biomonitor and phytoremediator for environmental U-contamination in the Sevilha mine (uraniferous region of Beiras, Central Portugal). A total of 53 plant species belonging to 22 families was collected from 24 study sites along with ambient soil and/or water samples. The concentration of U showed wide range of variations in the ambient medium: 7.5 to 557mgkg−1 for soil and 0.4 to 113μgL−1 for water. The maximum potential of U accumulation was recorded in roots of the following terrestrial plants: Juncus squarrosus (450mgkg−1 DW), Carlina corymbosa (181mgkg−1 DW) and Juncus bufonius (39.9mgkg−1 DW), followed by the aquatic macrophytes, namely Callitriche stagnalis (55.6mgkg−1 DW) Lemna minor (53.0mgkg−1 DW) and Riccia fluitans (50.6mgkg−1 DW). Accumulation of U in plant tissues exhibited the following decreasing trend: root>leaves>stem>flowers/fruits and this confirms the unique efficiency of roots in accumulating this radionuclide from host soil/sediment (phytostabilization). Overall, the accumulation pattern in the studied aquatic plants (L. minor, R. fluitans, C. stagnalis and Lythrum portula) dominated over most of the terrestrial counterpart. Among terrestrial plants, the higher mean bioconcentration factor (≈1 in roots/rhizomes of C. corymbosa and J. squarrosus) and translocation factor (31 in Andryala integrifolia) were encountered in the representing families Asteraceae and Juncaceae. Hence, these terrestrial plants can be treated as the promising candidates for the development of the phytostabilization or phytoextraction methodologies based on the accumulation, abundance and biomass production.

Characterisation of holocene plant macrofossils from north spanish ombrotrophic mires: Vascular plants

Methods and criteria that were used to identify plant macrofossils from four ombrotrophic mires in northern Spain are presented. Twelve monocotyledon and ten dicotyledon species were recorded. Some were identified from vegetative or reproductive macroremains (Eriophorum angustifolium, Molinia caerulea, Calluna vulgaris, Erica mackaiana, Erica tetralix, Potentilla erecta), while others were recognised only by their fruits (Rhynchospora alba, Carex durieui, Carex echinata, Carex binervis, Carex demissa, Betula alba), seeds (Juncus squarrosus, Juncus bulbosus, Luzula multiflora, Narthecium ossifragum, Drosera rotundifolia, Drosera intermedia, Caltha palustris, Daboecia cantabrica), rhizome fragments with remains of leaves (Agrostis curtisii), or twigs with buds and leaves (Vaccinium myrtillus). Descriptions of the specific distinctive characters for the plant macrofossils that were recorded are accompanied by illustrations that facilitate their interpretation. Dichotomous identification keys are also provided.

Effets be l'étrépage pour la restauration de landes tourbeuses en haute belge

Vegetation restoration was attempted in a degraded wet heath overgrown by Molinia caerulea in High Ardenne (Belgium). Top peat—removal was applied in spring 1989 and the vegetation was recorded, in 1989 and 1998, using the Braun—Blanquet method. Top peat—removal had a pronounced and beneficial effect, decreasing the cover of Molinia caerulea and increasing the cover of typical wet heath species (Juncus squarrosus, Carex panicea, Erica tetralix, Trichophorum cespitosum, Narthecium ossifragum). Peat removal also promoted the re—establishment of rare species like Drosera rotundifolia and Lycopodiella inundata. The results of diaspore bank are presented.

A test of mowing and soil-removal restoration techniques in wet heaths of the High Ardenne, Belgium

Vegetation restoration was attempted in four plots of a degraded wet heath overgrown by Molinia caerulea in High Ardenne (Belgium). Two treatments, mowing for two years and removal of the top 3-28 cm of peat, were applied in spring 1989. The vegetation was recorded in 1989 and 1998 using the Braun-Blanquet method. After nine years, the mowing treatment had relatively little effect on vegetation composition. We observed a 0-25 % decrease of Molinia cover and an increase of some heath species like Calluna vulgaris (12-47 %) and Erica tetralix (0-12 %). However, top peat removal had a pronounced and beneficial effect. A decrease of a mean of 66 % in cover of Molinia caerulea was observed as well as an increase of the cover of Erica tetralix (0-12 %). Peat removal also promoted the re-establishment of some typical wet heath species like Juncus squarrosus and Carex panicea, as well as of some rare pioneer species like Drosera rotundifolia and Lycopodiella inundata. This treatment appears to be favorable for the regeneration of degraded wet heaths in High Ardenne.

LONG-TERM TRENDS OF RADIOCESIUM ACTIVITY CONCENTRATIONS IN VEGETATION IN IRISH SEMI-NATURAL ECOSYSTEMS

137Cs activity concentrations were determined in vegetation from four Irish blanket bog ecosystems during the summer months of 1989-1997. The dominant and abundant vegetation species were sampled at each site and the data were used to estimate long-term trends of 137Cs activity concentrations. A general decline in the 137Cs activity concentrations in vegetation was observed from all sites sampled. The fastest and most consistent long-term rates of 137Cs decline were observed in the bryophyte and lichen vegetation group with 137Cs effective half-life (T ef) values of 2.2 to 10.7 y. The ericoid group with the exception of one case also showed a significant long-term decline in 137Cs activity concentrations with T ef values of 3.5 to 12.4 y as did the rush species Juncus squarrosus (T ef range 9.3 to 12.8 y). The sedge and grass groups showed the slowest and the least consistent rates of 137Cs decline, with T ef values of 2.9 to 59.8 y. Preliminary evaluation of 137Cs activity concentrations in sheep from some of the studied sites suggests that the decline found in vegetation is reflected in sheep.

Vegetation development on upland and marginal land treated with herbicide, for bracken (Pteridium aquilinum) control, in Great Britain

A chronosequence, or space-for-time substitution, survey was carried out to investigate the impact on associated vegetation of spraying with asulam for the control of Pteridium aquilinum. The survey covered 117 sites in upland and marginal areas of Great Britain. A series of environmental variables were measured including those defining or relating to regional spread, mesoclimate, microclimate and site condition. The vegetation showed high β-diversity with a considerable number of sites representative of upland grassland, heath and woodland. Species α-diversity increased after spraying. However regional differences were found.Indirect gradient analysis (unconstrained ordination using detrended correspondence analysis) suggested strong spatial, slope and sea distance gradients in determining species composition. Site conditions and time since spraying were also correlated. There was a high degree of collinearity between environmental variables. A hybrid ordination (using canonical correspondence analysis) was employed to investigate further the role of time (the only constrained variable) since spraying. The ordination showed a trend of species in time-after-spraying, starting with those lost early (Oxalis acetosella) and ending with stress-tolerant species (Juncus squarrosus). This ordination also revealed a second gradient almost parallel to axis 2 spanning the dichotomy between species rich grassland and degraded or invaded heath.Though control procedures appear to be reducing bracken successfully, there are strong regional variations in vegetation development. Thus, policy changes are suggested whereby either, improved cost-effectiveness, or, more effective treatment may be available.

Responses of three generations of a xylem‐feeding insect, Neophilaenus lineatus (Homoptera), to elevated CO2

AbstractA population of the xylem‐feeding spittlebug, Neophilaenus lineatus, on blocks of natural vegetation transferred to large hemispherical chambers was studied over two generations with continuous exposure to elevated CO2 (600 ppm). The third generation was transferred from the blocks to potted Juncus squarrosus to enable measurements of fecundity. The principal food plant throughout was Juncus squarrosus. Survival of the nymphs was reduced by more than 20% in elevated CO2 relative to ambient (350 ppm) in both years of the main experiment. Elevated CO2 also delayed development by one or more nymphal instars in each year. Fecundity was not significantly affected.The C/N ratio of whole Juncus leaves was increased in elevated CO2 and the transpiration rates of the plants were reduced. These changes may have been responsible for the effect of elevated CO2 on spittlebug performance. However, other factors such as plant architecture and microclimate may also be important.

Root production, turnover and respiration under two grassland types along an altitudinal gradient: influence of temperature and solar radiation.

We have measured the rates of root production and death and of root respiration in situ under two grasslands along an altitudinal gradient in the northern Pennines, UK, represented by a lowland site at 171 m in an agricultural setting, and three upland sites between 480 and 845 m. One grassland was dominated by Festuca ovina and was on a brown earth soil; the other was dominated by Juncus squarrosus and Nardus stricta and occurred on a peaty gley. The natural altitudinal gradient was extended by transplantation. Although root biomass and root production (estimated using minirhizotrons) both showed pronounced seasonal peaks, there was no simple altitudinal gradient in either variable, and neither root production nor root death rate was a simple function of altitude. Increased root accumulation in summer was a function of change in the length of the growing season, not of soil temperature. Root populations in winter were similar at all sites, showing that increased production at some sites was accompanied by increased turnover, a conclusion confirmed by cohort analyses. Respiration rate, measured in the field by extracting roots and measuring respiration at field temperature in an incubator, was unrelated to temperature. The temperature sensitivity of respiration (expressed as the slope of a plot of log respiration rate against temperature) showed no simple seasonal or altitudinal pattern. Both root growth (under Festuca) and respiration rate were, however, closely related to radiation fluxes, averaged over the previous 10 days for growth and 2 days for respiration. The temperature sensitivity of respiration was a function of soil temperature at the time of measurement. These results show that root growth and the consequent input of carbon to soil in these communities is controlled by radiation flux not temperature, and that plants growing in these upland environments may acclimate strongly to low temperatures. Most carbon cycle models assume that carbon fluxes to soil are powerfully influenced by temperature, but that assumption is based largely on short-term studies and must be reassessed.

Effects of temperature elevation on the population dynamics of the upland heather psyllid Strophingia ericae (Curtis) (Homoptera: Psylloidea)

1 Cloches permeable to gas and water were used to simulate the effect of climate warming on upland populations of the heather psyllid Strophingia ericae at Moor House National Nature Reserve in the North Pennines, UK.2 The cloches produced an average warming of about 1 °C in the heather canopy over a period of one year.3 The density of S. ericae increased markedly in cloches within a few months of erection.4 Species composition and numbers of potential predators were similar inside cloches and in control plots.5 In the two year life‐cycle of S. ericae, the warming effect advanced the phenology from the second to third instar in the first winter, but in the second winter, fifth instar nymphs did not moult prematurely to adult.6 The density of S. ericae was higher on Calluna vulgaris at its boundary with Juncus squarrosus than in the pure C. vulgaris sward (in both cloched and control plots).

An Evaluation of Ratio Systems in Radioecological Studies

Replicate samples of soil, Juncus squarrosus and Calluna vulgaris were taken within a grid system on an organic peatland soil site in Ireland. A similar sampling survey was carried out on an organic rich forest soil site in Sweden, where Vaccinium myrtillus and Vaccinium vitis-idaea with corresponding soil samples were taken within a Picea abies stand. The data were used to investigate the relationship between soil and plant 137Cs content and to examine the validity of using ratios to describe this relationship. Findings from both countries were in agreement. There were no significant changes in plant 137Cs concentration associated with increasing soil content. When data from both countries were merged and treated as a single data set, a significant overall positive correlation (95% confidence level) between soil and plant 137Cs levels was observed. Concentration ratios and transfer factors were calculated for 137Cs and 40K uptake from soils to plants. Both ratio types exhibited a clearly defined decrease associated with increasing soil concentrations for both radionuclides. Findings demonstrate serious problems with the use of ratios for the evaluation of radionuclide transfer.

A new method for prediction of radiocaesium levels in vegetation: Evidence from Irish uplands

Vegetation and soil samples from three upland areas in the Republic of Ireland were collected and analysed for radiocaesium. The data were used to investigate temporal trends in vegetation and to examine the relationships among radiocaesium concentrations in soils and various plant species. Radionuclide concentrations in Calluna vulgaris were compared with those in Erica cinerea, Erica tetralix and Juncus squarrosus and a consistent pattern emerged on all three study sites. No marked seasonal variations in concentrations were observed in these species. Clearly defined seasonal behaviour was, however, observed in Scirpus caespitosus. Concentrations were highest in Calluna vulgaris and Scirpus caespitosus, reaching peak activities of approximately 2000 Bq kg −1 dry weight. Concentrations in the other species were considerably less. A plant-to-plant ratio system is proposed as a new method for prediction of radionuclide concentrations in plants. Values calculated for plant-to-plant ratios are compared to traditional soil-to-plant ratio values and field data are used to test the performance of these ratios. Replication of both ratio systems gave consistent results when the experiments were repeated. The data demonstrate that the plant-to-plant ratio system can produce predictions as accurately as the soil-to-plant system. Results further suggest that the two systems are intrinsically related and that ratio values tend to be site specific but are of some value for between site predictions.

Long-term vegetation change in the Juncus squarrosus grassland at Moor House, northern England

Data from the long-term experiment on sheep grazing versus zero sheep grazing (i.e. in an enclosure) on the composition of the Juncus squarrosus grassland at the Moor House NNR are presented. The data have been analysed to assess change in (1) the abundance of individual species, (2) higher plant and bryophyte communities, and (3) vegetation structure. The higher plant data suggested that both the enclosed-and grazed plots were changing in the same direction, but the enclosed plot was moving much faster. The general tendency was towards a blanket bog vegetation dominated by Eriophorum vaginatum and Calluna vulgaris. Juncus squarrosus has declined very quickly in the enclosed plot, but there has also been a slower decline in the grazed one. A significant increase in Calluna vulgaris has occurred only in the enclosed plot. In contrast, the bryophyte data showed completely different successional trajectories in the two treatment plots.

Studies in the Grazing of Heather Moorland in North-East Scotland. V. Trends in nardus Stricta and Other Unpalatable Graminoids

(1) Botanical composition, grazing treatment and trends in heather (Calluna vulgaris (L.) Hull.) were recorded for periods of 4-15 years at moorland sites ranging in altitude from 70 to 700 m. Tussocks of Nardus stricta L. in permanent 1-M2 areas were monitored yearly at three sites. (2) Changes in the cover of Juncus squarrosus L., Molinia caerulea (L.) Moench and Nardus were inversely related to cover trends in Calluna, but only weakly so. Juncus squarrosus was unresponsive, with only one significant change at its twenty sites; Molinia increased significantly at four sites where Calluna declined. (3) Nardus showed many small increases in cover which were counterbalanced by large decreases at two of its twenty-three sites, giving a negligible overall trend. Increases were largest at sheep-grazed sites, but no significant general relationship could be shown with grazing type. (4) Nardus changes were more consistently related to the state of Calluna as expressed by percentage cover x height than to the trends of Calluna cover. Nardus declined once Calluna mean height exceeded 15 cm. At one site heavy cattle grazing reduced Nardus cover. (5) Many seedlings of Nardus became established, most in positions close to mature tussocks. (6) Increment in Nardus tussock diameter was little influenced by grazing, even though tussocks grazed in one summer were more likely to be grazed in the next. (7) It is concluded that Nardus will spread in grazed moorland unless soils are very dry or Calluna is present and allowed to grow tall for periods of several years.

The spider communities on peat and upland grasslands In northern England

Between midsummer 1976 and November 1977 some 29000 spiders belonging to 168 species were caught in pitfalls on 42 peat and upland grassland sites covering an altitude range of 11–827 m in the north of England. The similarities between the spider faunas of each site have been assessed using a modified form of Sørensen's Index and the sites clustered according to their similarities. The sites divided into two major groups; (1) mineral soils where grasses are dominant or shallow peat soils where Juncus squarrosus is dominant and (2) peat soils where Eriophorum vaginatum and Calluna vulgaris are dominant. It is suggested that this major division is the result of the plant “architecture” rather than the species composition of the vegetation. Direct comparison between paired peat and grassland sites at the same altitudes shows no marked separation in the spider species composition on the two soil types but there are differences in abundance of individual species. The three peat site clusters form an altitudinal sequence which is not the result of the decline in numbers of non‐linyphiid species with increase in altitude as the cluster formation is largely dependent on the linyphiid species which dominate the catches.Twenty one common species have been used lo identify the communities. Many of these species are often found together and form associations. Typically, a number of associations contribute to each community. Only 19 species contribute more than 4% to the numbers of individuals caught in any one community.Diversity declines with increase in altitude, as does the number of species caught. The decline in the number of species caught is the effect of a decrease in non‐linyphiid species with increasing altitude. There is no significant decline in the numbers of species of linyphiids with increase in altitude.

The Effect of Clipping on Net Photosynthesis and Dark Respiration Rates of Plants from an Upland Grassland, with Reference to Carbon Partitioning in Festuca ovina

Four co-existing species (Deschampsia flexuosa, Festuca ovina, Juncus squarrosus and Nardus stricta) were subjected to clipping and the net photosynthetic and dark respiration rates were followed after this treatment for 50 d. Concurrently carbon partitioning in F. ovina plants clipped initially and again at 50 and 100 d was examined. An expansion of new leaf lamina was observed with F. ovina, which had a greater net photsynthetic rate per unit leaf area than unclipped lamina. The remaining leaf lamina (stubble) after clipping also showed net photosynthetic and dark respiration rates greater than unclipped lamina; these responses were unique to F. ovina plants. N. stricta was the only other species to attain a pre-clipping photosynthetic rate within 6 d. Clipped F. ovina plants showed a change in carbon allocation pattern, with a reduction in carbon allocated to roots. 14C accumulated in roots and stubble was shown to have a role in regrowth, as was current assimilate via the production of new leaf lamina. Plants initially clipped before exposure to 14C, redistributed less 14C to new shoot growth and, therefore, lost less when subsequently clipped. Further redistribution of 14C came from leaf stubble tissue and not at the expense of roots. The variation between species in clipping response are discussed in terms of the implications for coexistence.

The predation of predispersed Juncus squarrosus seeds by Coleophora alticolella (Lepidoptera) larvae over a range of altitudes in northern England.

Seed production by the rush Juncus squarrosus and its subsequent predation by the larvae of the moth Coleophora alticolella were measured at a series of sites at different altitudes in northern England. The density of seeds produced is progressively reduced with increasing altitude. The density of larvae was greatest in the middle region of the transect. Seed predation was therefore highest at about 300 m. Predation was reduced to nil above 520 m, where the larvae were absent, but remained between 40 and 50% below 250 m. The density of predispersed seed surviving was greatest at the lowest site where the highest density of seeds was produced and predation was moderate. The lowest densities of surviving seeds were found around 300 m and also above 600 m where there was no predation but few seeds were produced. A similar density survived around 520 m as at 245 m, although the density of seed produced at 520 m was less than 30% of that at 245 m. The results are discussed in relation to the population dynamics of the moth in different parts of its altitudinal distribution.

Nitrogen acquisition in four co‐existing species from an upland acidic grassland

The concentration of both nitrate and ammonium nitrogen was measured in soil taken from an upland acidic (pH 4.5) grassland habitat, containing four co‐existing species, Deschampsia flexuosa (L.) Trin., Festuca ovina L., Juncus squarrosus L. and Nardus stricta L. Both nitrate and ammonium nitrogen were found to be present in the soil, in similarly small quantities. The effect of both sources of nitrogen on relative growth rate was studied, and an attempt was made to determine whether nitrate or ammonium nitrogen is the immediate source of nitrogen for these plants using assays of nitrate reductase (EC 1.6.6.2) and ammonium uptake. All four species showed larger growth rates on the same concentration of ammonium nitrogen compared to nitrate nitrogen. All species showed low activities of leaf nitrate reductase, even in plants grown on 18 mol nitrate m−3. Ammonium uptake activity appeared to be higher in species which showed the lowest nitrate reductase activity and least response to increasing nitrate concentration in the growth medium.

The ectoparasitization ofColeophora alticolella(Lepidoptera) in relation to its aititudinal distribution

Abstract.1. The parasitization of the larvae ofColeophora alticolella. feeding onJuncus squarrosus, was investigated at a series of altitudes from 15 to 520m above sea‐level in northern England during 1977 and 1978.2. Six species of primary parasitoid and one hyperparasitoid were reared from this host. Five of the primary parasitoids were ectophagous; only two specimens of the endoparasitoid,Gonotypus melanostoma, were reared.3. All of the parasitoid species were recorded at 15 m but fewer at sites of higher altitude. Only one species,Scambus brevicomis, was recorded above 305 m, and none above 395 m. The hyperparasitoid,Tetrastichus endemus, waspresent only at 15 m.4. Percentage parasitization was highest at 15 m; it was reduced from 51% to only 2% between 215 and 305 m in 1978. There was an increase in host density over this altitudinal range.5. Three species,Scambus brevicomis. Elachertus olivaceusandEuderus viridis, accounted for most of the parasitization, but their relative proportions vaned at different altitudes.6. The sex‐ratios of the parasitoids reared fromColeophora alticolellaranged from 3.2% females forScambus brevicomis, which is considered to also use larger hosts, to 99.4% females forElachertus olivaceus, which develops by thelytokous parthenogenesis.7.Euderus viridisandScambus brevicomisstarted to attack theColeophora alticolellalarvae at a later date at 245 m than at 15 m, but attack byElachertus olivacatswas not delayed at the higher site.