The study of chalk grassland in Northern France: An historical review

The study of chalk grassland in Northern France has evolved through three main phases. During the period from the early 19th century to the First World War, the general flora of Northern France was studied in some detail, but there was little ecological understanding of plant communities. Some workers, however, did attempt to group chalk grassland species ecologically, and the primitive concepts of plant sociology unconsciously developed. Between the wars, with the growth of plant sociology, chalk grassland studies became more elaborate. Specific associations were now described and the wider aspects of chalk grassland phytogeography considered. The post-war period has seen a great increase in botanical activity in Northern France. There have been many regional chalk grassland studies, all of which, in varying degrees, have employed the techniques of plant sociology. It may at last be possible to synthesise these studies, and to describe the chalk grassland associations of Northern France.     

An 11400 year paleoecological history of a British chalk grassland

The first broad-based, paleoecological analysis of a sedimentary sequence on the British chalk, dating to the terminal Pleistocene, reveals a history of climatic, vegetational and faunal change. The past co-occurrence of currently allopatric species among molluscs, beetles and plants supports hypotheses of the impermanence of communities. Modern pollen rain data are utilized to refine the ecological interpretation of the fossil pollen data. The presence of the Windermere Interstadial (Allerod) and the Loch Lomond re-advance (Younger Dryas) are represented by decreased abundances of arboreal taxa and increased representation of cold grassland elements. Open grassland habitats appear to have been a continuous landscape element, at least locally, since the late-glacial period on the northern British chal Mands, although their species composition has changed greatly in the last 11400 yr.     

Dynamics of bryophytes in a chalk grassland

Dynamics of bryophytes were followed in a chalk grassland in 4 plots, 25×25 cm, each subdivided in to 400 subplots, in which every 3–4 months the presence of all bryophyte species was recorded. During the first 14 months no successional trends were visible. However, dynamics on the scale of one subplot were considerable. Degree of dynamics was markedly negatively correlated with original presence in the plots. Several explanations for this correlation are discussed.     

Restoration management of abandoned chalk grassland in the Netherlands

After abandonment of chalk grassland in the Netherlands, Brachypodium pinnatum had become very dominant and this resulted in a dramatic decrease of plant diversity. Restoration of these abandoned sites is important, because of its former high diversity with many nationally endangered species. To restore the chalk grassland vegetation, the impact of the introduction of different experimental cutting regimes was investigated during three years. The thick litter layer and the dominance of Brachypodium was strongly reduced after introduction of all cutting regimes. In all cutting treatments forb phytomass increased considerably, especially in the twice-a-year cutting vegetation, where the forb phytomass became as high as that of Brachypodium. Phanerogamic species diversity was stimulated in all cutting regimes. Especially the number of short-lived forbs. with a persistent seed bank, increased markedly in the twice-a-year cutting treatment. It is concluded that cutting the vegetation twice is adequate to reduce the negative effects of the thick litter layer and the abundant growth of Brachypodium. It creates an appropriate starting point for more detinite management, whether mowing or grazing. However, the restoration of a more complete species assortment strongly depends on the re-invasion possibilities of these species.     

Plant diversity in four chalk grassland sites with different aspects

Plant diversity and its components was studied on four chalk grassland sites in southeast England over a fourteen-month period. The sites were almost adjacent, and each faced one of the major compass points, N, S, E and W. Aboveground vegetation was recorded at monthly intervals by cover repetition, using a point quadrat technique. Seasonal patterns in the development of leaf area, bare ground, number of species present and diversity were similar on all sites. The N and W facing slopes and the S and E facing slopes resembled each other in several characteristics, while these two pairs of slopes differed markedly from each other. Thus, (i) there were more grasses but fewer forbs on the N and W slopes, (ii) overall diversity and forb diversity were lower on the N and W slopes but grass diversity was higher, (iii) equitability was lower on the N and W slopes, (iv) percentage similarity of begetation present was high when the N slope was compared with the W and when the S slope was compared with the E; other comparisons gave lower percentage similarity. It is proposed that the greater abundance of Carex flacca on the N and W slopes is important in causing these differences, and that it results in lower diversity on these slopes by occupying part of the habitat of the species-rich forb community which occurs on the S and E slopes. Dominance-diversity curves range from lognormal to geometric in form; some interpretation of changes they display can be made by assuming that the community is in a non-equilibrium state caused by seasonal environmental fluctuations each winter.     

Snail faunas in the early stages of a chalk grassland succession

Snail faunas from 10 sites in chalk grassland on the South Downs are described. The sites represent a range of early stages in the succession of grazed chalk grassland to scrub. The faunas of the later stages sampled, with vegetation 12–45 cm high, are substantially different from those of the earlier stages (2.5–10 cm high), lacking most xerophil species, and having much higher proportions of species typical of woods and hedgerows.
The results are discussed in relation both to those from other studies of existing faunas, and also to the environmental interpretation of buried faunas from geological and archeologtcal studies.     

Relationship between horizontal pattern and vertical structure in a chalk grassland

Our objective was to examine the relationships between patterns of vertical structure and species microassociations at various scales in a species-rich chalk grassland.Transect data were analyzed for species microassociations by multiscale ordination of presence data from the Gerendal Nature Reserve, The Netherlands. Results indicated microassociations at scales of 30 cm, 2 m, 3 m, and 10 or more m. The microassociations at each scale comprised different but overlapping constellations of species.For the same transect, profile photographs were taken through the vegetation against a white background, and image analysis was used to provide indices of vegetation vertical cover, height and vertical center of biomass. Pattern analysis of these data indicated a regular pattern at a scale of 3 m.Standardized cross-variograms of the patterns of microassociations and vertical structure revealed only very weak relationships, even though one microassociation pattern and the vertical structure patterns occurred at the scale of 3 m. This is because the two 3 m patterns fell in and out of phase.Abbreviations PCA principal components analysis     

Species composition and above ground phytomass in chalk grassland with different management

During the last decades chalk grasslands lost their agricultural importance in the greater part of their distribution area in W Europe. Due to their botanical richness a number of chalk grassland sites were established as Nature Reserve. As a consequence of the semi-natural character of these grasslands an appropriate management is necessary to maintain or to re-create this vegetation including a great number of rare and endangered species.This paper deals with the results of three different management practices, viz. mowing in autumn, sheep grazing and abandoning, of a medium term (8–11 yr) permanent plot experiment. Sheep grazing was considered the best management since it resulted in the highest number of species, phanerogams as well as bryophytes, and the highest number of characteristic chalk grassland species. Abandoning resulted in a decrease in species number and a dominance of a few species only.The changes in species number are related to the above ground biomass. Under the canopy in the abandoned plot light intensity and the Red/Far-red ratio are very low, which partly explains the decrease in species number as such conditions are not favourable to seedling emergence and survival.Plant nomenclature follows Heukels & Van Ooststroom (1975) for phanerogams, Margadant & During (1976) and van der Wijk et al. (1969) for bryophytes, and Westhoff & den Held (1969) for syntaxa.Presented at the Symposium on Vegetation Dynamics, organized by the International Society for Vegetation Science at Montpellier, 15–20 September 1980. I am grateful to Dr. H. J. During for useful comments.     

Effects of selective clipping and mowing time on species diversity in chalk grassland

Phytomass distribution and species diversity were followed in a chalk grassland with different selective clipping treatments during 4 years. Removal of the dominantBrachypodium resulted in a sharp increase in forb phytomass and in species number. The dominance-diversity curve changed in shape from geometric to log-normal. Obviously,Brachypodium restricted the growth of most other species. Removal of all species except the dominant showed, in contrast to the niche pre-emption theory, a marked increase in phytomass and reproductive effort ofBrachypodium. It seems that other mechanisms can also lead to a geometric distribution. Removal in a type of vegetation without obvious dominants and with a log-normal species distribution revealed that interspecific competition is not an important factor in this vegetation. This suggested a low intensity of species interaction and a large influence of restricting density-independent factors. Finally, to reduce the dominance ofBrachypodium we implemented a 4-year mowing experiment. Mowing earlier in the season resulted in a reduced exclusion of species byBrachypodium. This alternative mowing time may be sufficient to restore species diversity in chalk grassland. Experiments are under way to further substantiate this conclusion.     

Canonical analysis of asymmetric matrices: two applications from a study of chalk grassland in the south of England

Gower's (1977) method for the canonical analysis of asymmetric matrices (CAA) where the same entities index both the rows and the columns is described. This technique displays the indexing entities in a series of orthogonal planes of decreasing importance in such a way as to preserve the pattern of the asymmetry between them. The analysis is applied to a half-diallel experiment and to some leaf-overtopping data, both from a study of the control of relative abundance of perennials in chalk grassland. The results suggest a common source for the asymmetry in the very different interference and overtopping data, namely that of leaf height. It is concluded that relative abundance in the field may be determined, in part, by leaf height through aboveground interference between plants.Nomenclature follows Tutin et al., 1964–1980. Flora Europaea, Vols 1–5. Cambridge University Press, Cambridge.I am particularly indebted to the Nature Conservancy Council for permission to carry out the field experiment on the Aston Rowant N.N.R., and to do field work at Castle Hill N.N.R.We are grateful to R. A. Kempton for permission to use his methodology in the analysis of the half-diallel experiment prior to publication. This work was carried out while J.M. was in receipt of a Research Studentship from the Natural Environment Research Council, and L.G. was in receipt of an internal Research Studentship from Trinity College, Cambridge.     

Fine-scale spatial distribution of leaves and shoots of two chalk grassland perennials

The fine-scale spatial distribution of leaves and shoots of Brachypodium pinnatum and Carex flacca, two rhizomatous graminoids, was investigated in two chalk grasslands in South Limburg (The Netherlands). The objective was to examine whether leaves and shoots of Brachypodium, a dominant species, had a regular distribution on a small scale, as has been suggested for other clonal species that form high-density stands. Patterns were compared to Carex, which is never found to be as abundant as Brachypodium.The number of shoots and leaf contacts were counted in small quadrats, grouped in a grid. Using Moran's I analysis for autocorrelation, it appeared that leaves and shoots of both species were arranged in clumps, and that these clumps were randomly distributed across the soil surface. Shoot clumps in Carex were smaller in diameter and not as pronounced as those in Brachypodium.In most cases, patterns of leaves and shoots were positively correlated, indicating that leaves were predominantly positioned above and around the groups of quadrats where the shoots were attached. However, in dense stands of Brachypodium the positions of leaf clumps were not correlated to those of shoot clumps. This is a result of the tall growth form of this species and its high shoot densities, and it is suggested that this will be a characteristic of any species that dominates a dense stand.     

Comparison of three seed trap types in a chalk grassland: toward a standardised protocol

In a chalk grassland in north-western France, vegetation and seed rain were studied along two transects. We compared the efficiency of three types of seed traps (funnel traps, sticky traps, pots exposed in the field) to estimate the annual seed rain and to reveal various processes involved in plant community regeneration. Data were analysed to compare seed density, species richness and composition across seed traps and vegetation. Geostatistical analyses (semivariograms. were used to detect possible autocorrelation and to examine patterns of spatial variation in seed rain and vegetation. The results show that (1) funnel traps are most efficient (56 species, 8079 seeds.m^–2). (2) Each type of seed traps brings different information about the processes involved in seed dispersal and seedling establishment. Sticky traps help to understand import and export of seeds in a community through anemochory. Funnel traps may provide a measure of the auto-regeneration capacity of the vegetation through its local seed production. Pot traps integrate various processes involved between seed dispersal and seedling emergence. (3.) The exposition to environmental conditions generates marked spatial patterns in species richness measured in pots and in vegetation, selecting species able to survive. Pot traps indicate that numerous species producing seeds in standing vegetation are unable to establish in the field through seedling recruitment. Our study emphasizes the need of using different types of seed traps and spatial sampling configurations to assess the regenerative potential of standing vegetation and the various mechanisms involved in seed dispersal. A standardised protocol for seed rain sampling was finally developed.     

Observations on north-west european limostone grassland communities IV. Phytosociological notes on chalk grasslands in Denmark

This paper deals with phytosociological studies of Danish chalk grasslands. These grasslands should be reckoned to a new association, viz. Solidagini-Helictotrichetum pratensis, alliance Mesobromion, class Festuco-Brometea. Two geographically vicarious subassociations could be distinguished. Furthermore attention has been payed to the cryptogams occuring in these grasslands, the influence of dominance of an introduced plant species on the species diversity, and the changes during the last decades in species composition as well as in area of the chalk grasslands in Denmark.     

Root length/leaf area ratios of chalk grassland perennials and their importance for competitive interactions

Abstract. The use of root / shoot ratios to describe allocation of dry weight to structures for capturing soil resources and light is limited due to other functions of the root and shoot such as support and storage. The ratio of fine-root length to leaf area (RLA) provides a better expression of the relative sizes of above-and below-ground exchange surfaces. Dry matter partitioning, leaf area and root lengths were determined for five species of chalk grassland perennial (Carex flacca, Cirsium acaule, Festuca ovina, Leontodon hispidus and Scabiosa columbaria) by extraction of soil cores from an intact sward. The forb species had a greater proportion of their dry matter below-ground. Interspecific variation in values of RLA was considerable, mean values ranging from 137 m/m² in Cirsium acaule to ca. 27 000 m/m² for Festuca ovina. The implications of this interspecific variation in RLA for the competitive interactions in infertile calcareous grasslands are discussed in relation to phenology and internal nutrient cycling.     

Bioarchaeological research in Croatia--a historical review

The study of human skeletal remains from archaeological sites gives us the opportunity to answer important questions about the lifestyle of past populations. The discipline that studies human skeletal remains is known as bioarchaeology. This paper provides a historical review of bioarchaeological research in Croatia. It is based on the available published material that analyzes human skeletal remains from archaeological sites located on the Croatian territory covering time span from the Neolithic period to the late Middle Ages.     

Influences of space, soil, nematodes and plants on microbial community composition of chalk grassland soils

Microbial communities respond to a variety of environmental factors related to resources (e.g. plant and soil organic matter), habitat (e.g. soil characteristics) and predation (e.g. nematodes, protozoa and viruses). However, the relative contribution of these factors on microbial community composition is poorly understood. Here, we sampled soils from 30 chalk grassland fields located in three different chalk hill ridges of Southern England, using a spatially explicit sampling scheme. We assessed microbial communities via phospholipid fatty acid (PLFA) analyses and PCR-denaturing gradient gel electrophoresis (DGGE) and measured soil characteristics, as well as nematode and plant community composition. The relative influences of space, soil, vegetation and nematodes on soil microorganisms were contrasted using variation partitioning and path analysis. Results indicate that soil characteristics and plant community composition, representing habitat and resources, shape soil microbial community composition, whereas the influence of nematodes, a potential predation factor, appears to be relatively small. Spatial variation in microbial community structure was detected at broad (between fields) and fine (within fields) scales, suggesting that microbial communities exhibit biogeographic patterns at different scales. Although our analysis included several relevant explanatory data sets, a large part of the variation in microbial communities remained unexplained (up to 92% in some analyses). However, in several analyses, significant parts of the variation in microbial community structure could be explained. The results of this study contribute to our understanding of the relative importance of different environmental and spatial factors in driving the composition of soil-borne microbial communities.