Analyzing mechanisms regulating diversity in rangelands through comparative studies: a case in the southwestern Pyrennees

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1 Biodiversity and Conservation 9: , Kluwer Academic Publishers. Printed in the Netherlands. Analyzing mechanisms regulating diversity in rangelands through comparative studies: a case in the southwestern Pyrennees ROSA-MARIA CANALS 1, and MARIA-TERESA SEBASTIÀ 2 1 Dept. Producción Agraria, Universidad Pública de Navarra, Campus Arrosadia s/n, Pamplona, Spain; 2 Escola Tècnica Superior d Enginyeria Agrària, Universitat de Lleida, Rovira Roure, 177, Lleida, Spain; Author for correspondence ( rmcanals@unavarra.es) Abstract. The preservation of the floristic diversity of natural ecosystems and the maintenance of extensive livestock grazing are two of the major priorities of European Union agricultural and environmental policies. Temperate natural and seminatural grasslands are among the most threatened ecosystems in Europe. In order to establish the most appropriate management practices that prevent degradation and maintain the richness of these ecosystems, detailed analyses of the mechanisms that regulate biodiversity of the communities are particularly necessary. In this study we make a comparative analysis of the species richness and the diversity of the main rangeland communities in a widespread, heterogeneous area located in the Western Spanish Pyrennees. The nature and the contribution of perennials and annuals to the diversity patterns encountered are studied and related to the mechanisms suggested to regulate diversity in each case. Higher diversity values were reported in more environmentally stressed, xeric and moist communities. High spatial and temporal heterogeneity and low rates of competitive displacement related to the scarcity of basic resources are among the factors suggested to regulate the diversity of these communities. In areas where environmental factors are more favorable, such as perennial-dominated mesic rangelands, the enhancement of the diversity seemed more dependent on biotic disturbances, such as herbivory, that decreased the cover of perennials and favored the recruitment of short-lived species. Dispersal processes related to traditional nomadic grazing allow a flow of species from one rangeland to another but also enhance the establishment of species coming from lowland habitats. Most of the annuals enhancing the diversity of the mesic community were ruderals. The consideration of ruderals as exotics or as species belonging to this grazing ecosystem poses an interesting, controversial topic related to the ecological quality of the diversity estimated for these communities. Key words: diversity, floristic richness, grasslands, heathlands, ruderals Introduction Preservation of biodiversity is one of the current environmental priorities worldwide (Willems et al. 1993; Brown et al. 1995). Biodiversity conservation efforts must focus greater attention on ecosystem processes rather than on ecosystem products (McNeely 1994). Understanding the mechanisms that maintain biodiversity in particular ecosystems enables the development of management practices that prevent future degradation (Chapin and Körner 1994). Mechanisms responsible for

2 966 species diversity in communities constitute a central topic in ecology (Marañon 1991). Processes occurring on large spatial and temporal scales may greatly affect species richness of local communities (Ricklefs 1987). Processes occurring on contemporary and local scales are more likely to affect community diversity. At a local scale, mechanisms generating diversity are both abiotic and biotic in nature, internal and external to the communities. Separated ecological niches (Grubb 1977), facilitation (Quinos et al. 1997) and competitive interactions (Tilman 1994) have been suggested as explanations of species coexistence. In addition, grassland diversity may be enhanced by spatial and temporal heterogeneity caused by abiotic factors (such as climate and outcrops), by particular interactions among plants (Tilman and Paccala 1993), and by interactions with other organisms (e.g. mycorrhizal associations, Zobel et al. 1997). Intermediate levels of population reduction have been shown to exert a positive effect on community diversity as well (Grime 1973; Collins and Barber 1985). Population reductions may be caused by disturbances of different nature such as drought, frost, herbivory, burrowing activities and disease (Collins and Glenn 1988; Huston 1994). As a consequence, propagules of less vigorous competitors enter the community, maintaining a pool of rare species that increase the diversity of the whole grassland (Ter Heerdt et al. 1991; McIntyre et al. 1995). Environmental stresses (e.g. scarcity of water and nutrients) may similarly enhance diversity, by reducing the growth of dominant species and consequently, avoiding the extinction of many taxa by competitive displacement (Huston 1979). Despite the fact that processes regulating diversity are easy to understand theoretically, their recognition in the field remains more difficult, and subtle changes may shift diversity in varied directions. A climatically harsh period, even a short one, may lead to significant reductions of local species richness instead of increasing diversity (Tilman and El Haddi 1992). Herbivory on communities dominated by annuals may promote a loss of diversity due to the decrease of propagules (Waser and Price 1981). On the other hand, favorable, non-stressing conditions for a given environmental factor may allow a wider range of adaptations by different species, enhancing community diversity in less stressed communities (Whittaker 1965), whereas extremely low levels of resources may reduce the number of species able to cope with these critical constraints (Glenn-Lewin and Ver Hoef 1988; Puerto et al. 1990). The problem of the generation and maintenance of diversity is inseparable from the problem of the ecological patterning (Levin 1992). Communities are complex, and complex systems require many scales for adequate description (Wiens et al. 1986; Allen and Hoekstra 1992). Grasslands, although highly dynamic and unpredictable at small spatial scales, maintain nearly constant populations at the community level (Herben et al. 1993). Whereas fine-scale studies may reveal greater detail about the biological mechanisms underlying patterns, generalizations and comparisons are more likely to emerge from broader scales (Marañon 1991; Van der Maarel 1993). In this study, we compare the species richness of three rangeland communities at

3 967 different scales, we describe their diversity and we relate the patterns encountered to the nature and contribution of the main guilds of plants developing in these communities (perennial graminoids, perennial forbs and annuals). Following this comparative approach we expect to gain a better understanding of the nature of the diversity and processes involved in each case (Huston 1994). Methods The study area The study was carried out at the Urbasa-Andia Natural Park, a ha area located in the Western Spanish Pyrennees ( Nand E). The park encompasses diverse parent materials, physiographical trends and soils. Soils are derived from limestones, dolomites, loamy limestones, and, to a lesser extend, calcarenites and sandstones. Due to its geographical location, the climate reflects both the Atlantic and the Mediterranean influences. The mean annual temperature is 8.4 C and the mean annual precipitation is 1275 mm. Precipitation varies annually and seasonally, with droughts occurring during summer. The vegetation is a complex mosaic of montane grasslands, heathlands of Erica vagans and beech forests. Grasslands and heathlands are generally located at altitudes ranging from 900 m to 1494 m, and include many areas considered candidates for the preservation (Natura 2000 network, European Union directive 92/43/CEE, 21 May 1992). Previous studies in the area, which applied multivariate numerical techniques on floristic data, allowed the identification of the main types of rangeland communities developing in the Park: xeric, mesic and moist communities (Canals 1997). The contrasting features of these communities reflect the wide variety of topographic, geologic and edaphic conditions of the region. Xeric communities develop preferentially on hard limestones and dolomites and are frequently located on slopes and on skeletal and stony soils. Mesic communities, more frequent in flatter areas, develop preferentially on loamy limestones, where soils are deeper and well developed. Moist communities, which experience transient waterlogging during moist periods, occupy smaller areas and are frequently associated with nutrient-poor, sandy-podzolic soils developed on washed calcarenites and on sandstones. These three types of communities, although dominated by hemicryptophyte graminoids and forbs, display a high spectrum of functional groups and plant taxa. This is probably favored by the special location of these ranges, in the twofold transition between the Eurosiberian-Mediterranean and the Cantabric-Pyrennean regions. Table 1 includes a list of the most common species of each community and Appendix 1 lists all the taxa found in the inventories. Biotic disturbances have been and are very frequent in the park. Intense grazing by domestic livestock has been practiced since late Neolithic. Currently, traditional

4 968 Table 1. Average percentage frequency of the major species of perennials (graminoids and forbs) and annuals in xeric, mesic and moist communities. Numbers in bold indicate where the highest frequency of a species is encountered. Nomenclature of the taxa follows Aseginolaza et al. (1984). Type of community Taxa Xeric Mesic Moist Perennial graminoids Agrostis capillaris Avenula mirandana Brachypodium pinnatum Bromus erectus Carex caryophyllea Carex flacca Cynosurus cristatus Danthonia decumbens Festuca indigesta Festuca g. rubra Luzula campestris Perennial forbs Achillea millefolium Bellis perennis Galium verum ssp. verum Hieracium g. pilosella Hypochoeris radicata Lotus alpinus Merendera montana Plantago lanceolata Potentilla montana Potentilla tabernaemontani Thymus polytrichus ssp. polytrichus Trifolium repens Annuals Aira caryophyllea Aphanes arvensis Bromus hordeaceus Cerastium diffusum Moenchia erecta Poa annua Trifolium campestre Trifolium scabrum Trifolium striatum Veronica arvensis Vulpia myuros nomadic shepherding (transhumance), although decreasing, is still a common practice. Free-range grazing by sheep, cows, horses and pigs typically occurs from early spring until late autumn. However, some herds are stocked all year round. Stocking rates are irregularly distributed throughout the park and they are higher in the most

5 969 productive areas, where mesic and moist communities develop (approx. 1.3 cattle ha 1 ), and lower in the xeric ones (usually less than 0.7 cattle ha 1 and constrained to late spring and early summer). Soil disturbances are very frequent as well, and are mainly caused by moles (Talpa europaea) and, to a lesser extent, by voles (Microtus spp.), pigs and wild boars (Sus spp.) and by ants of the genus Lasius. Field sampling Thirty plots of 100 m 2 (10 10 m) were randomly established at the Urbasa-Andia rangelands: 12 on xeric, 13 on mesic and 5 on moist communities. Overall the plots encompassed an extensive spectrum of the environmental conditions found in the area (parent material, geomorphological feature, aspect, slope, soil properties and degree and kind of biotic disturbance) and are described in detail in Canals (1997). Inventories were conducted during the growing seasons of 1993 to The plots, established at random each year, were divided in 100 quadrats of 1 m 2. The presence of vascular species at each quadrat was recorded. Overall, 3000 quadrats of 1 m 2 were sampled. Richness, diversity measurements and statistical analyses Species richness (S) of the plots was determined both at 1 m 2 and at 100 m 2 scales. Since the inventories of the plots were conducted over three years, we first computed a two-way ANOVA to test the hypothesis that there were no differences in richness among years, neither interaction community by year (Anon 1994). Since the hypothesis was accomplished, species richness, as well as the coefficients of variation among quadrats of a plot (calculated as the deviation, from the average of the 100 quadrats, of the number of species at each quadrat of 1 m 2 ) were compared among communities by means of a one-way ANOVA. Because different statistics stress out different aspects of the diversity concept, four indexes were calculated to assess community diversity: the Shannon diversity index (H ), the Pielou evenness index (J ), the Simpson index of dominance (D), and the inverse of the Simpson index (1/D). Formulas of these indexes are: H = Sp i Ln p i where p i is proportion of individuals belonging to the species i. J = H /H max where H max = Ln S, beings the species richness. D = S[n i (n i 1)/N(N 1)]

6 970 where n i is number of individuals of the species i and N is the total number of individuals. The Shannon diversity index and Pielou s measure of evenness are recommended for large, intense samplings due to their sensitivity to the occurrence of rare species, whereas the Simpson index and its inverse are more sensitive to changes in the distribution of the most abundant species (Peet 1974). These indexes were determined using the Jack-knife technique. Ecologically, this procedure is equivalent to repeatedly resampling the community, taking a slightly different set of plots at each turn (Scheiner 1992). Besides obtaining a more reliable value of the diversity of the entire community (Magurran 1989) this procedure allows the identification (by means of the calculation of the pseudovalues, VPi) of the plots that most strongly affect (increasing or decreasing) the diversity of the whole community (within-community diversity). We also plotted species/area curves. The design of the species/area curve allows the determination of the diversity index α (slope of the regression line between the number of species and the log of the area), and is a useful tool to discriminate among different types of community spatial organization (Begon et al. 1988; Van der Maarel 1988a). In order to obtain a better linear regression, the area was log-transformed. The absence of significant interaction between the covariate (area) and the treatment (type of community) proved the homogeneity of the slopes. Regressions of the different communities were compared by means of an analysis of covariance. We used one-way ANOVAs to test for differences among communities in the frequency and presence of perennial graminoids, perennial forbs and annuals. We also computed correlations between within-plot and within-community diversity and the contribution (presence and frequency) of the different guilds of species at each community. Results Averaged richness of vascular plants in 100 m 2 and 1 m 2 areas was high at the three types of communities studied (Figure 1). In 100 m 2 plots, mean values ranged from 55 to 62 species, with a maximum of 78 species reported in a xeric plot and a minimum of 43 species reported in a mesic one. In 1 m 2 quadrats, average species richness varied between species, with a maximum of 37 species in a mesic quadrat and a minimum of 10 species in a xeric one. Although richness values did not differ significantly among communities, coefficients of variation were significantly higher in xeric plots, suggesting that xeric areas had a more variable, heterogeneous richness at small scales (1 m 2 ) (Figure 1). For the species-area curves (Figure 2), regressions between the log of the area and the number of species were linear and significant for the three communities (for moist community, R 2 = 0.50, P < 0.001; for mesic

7 971 Figure 1. Averaged richness of vascular plants in 100 m 2 and 1 m 2 at the different communities, and coefficients of variation calculated as the deviation, from the average of the 100 quadrats, of the number of species at each 1 m 2. The asterisk indicates the existence of significant differences between the coefficients of variation of the communities calculated from the ANOVA ( P<0.05). Figure 2. Fitted regression lines between the number of species and the log of the area for the three communities. Regression equations are for the moist community ( ): no. species = log (area); for the mesic community ( ): no. species = log (area); for the xeric community (- - -): no. species = log (area).

8 972 community, R 2 = 0.45, P < 0.001; for xeric community, R 2 = 0.72, P<0.001), and differed significantly among them (F = ,P < 0.001). The slopes of the regression lines of S on log A (parameter α) were 20.2 in xeric plots, 18.8 in moist and 15.7 in mesic plots. Diversity values varied significantly among communities. Moist and xeric communities displayed higher diversities than mesic ones for all the statistics calculated (Table 2). Diversity pseudovalues allowed the identification of the plots that most increased the diversity of the different communities (although these plots were not necessarily the most diverse per se, Table 3). Plots on exposed topographies with abundant outcrops (as plots 11 & 29) or near the forest boundary (plot 7) enhanced the diversity of the xeric community. In moist areas, a plot which experienced alternating damp dry conditions (plot 19) increased particularly the diversity of the community. In mesic areas, higher pseudovalues corresponded to intensely grazed plots (plots 22, 10 & 2). Regarding the different guilds of species, perennial forbs were the most diverse and abundant group at the three communities (Figure 3). Perennial graminoids had a high diversity of taxa in mesic and moist communities while annuals tended to be more frequent and diverse in the xeric ones, though not significantly. Correlation analyses showed that plots that contributed the most to the diversity of the mesic community were those with the highest contributions of annuals and the lowest presence and frequency of perennial graminoids (Table 4). However, these plots were not, when taken individually, the most diverse. In other words, in mesic areas, the decline of perennial graminoids and the increase of annuals enhanced within-community diversity, whereas within-plot diversity was not significantly correlated with any of these sets of species. Table 2. Mean values and confidence intervals of the indexes H,1/D, D and J at the three communities. Different scripts mean no overlap between the confidence intervals of the communities. Community Lower limit Mean Upper limit Diversity Shannon Weaver (H ) Moist a Xeric a Mesic b Diversity 1/Simpson (1/D) Moist a Xeric a Mesic b Dominance Simpson (D) Moist b Xeric b Mesic a Evenness Pielou (J ) Moist a Xeric ab Mesic b

9 973 Table 3. Presence and frequence of perennial graminoids and annuals, H index, 1/D index, and corresponding pseudovalues obtained from the Jack-knife computation. Pseudovalues (VP i) give a measure of the influence of each plot in the diversity of the whole community and are based on the formula: VPi = (nv ) ((n 1)(VJi)) where n is the sample size, V the global diversity index and VJi the diversity calculated without considering the i plot. Within-community diversity Within-plot diversity Annuals Perennial graminoids Shannon Inv. Simpson Shannon Inv. Simpson Plot Presence % Frequency % Presence % Frequency % pseudovalue pseudovalue index index Moist community Mesic community Xeric community

10 974 Table 3. Continued. Within-community diversity Within-plot diversity Annuals Perennial graminoids Shannon Inv. Simpson Shannon Inv. Simpson Plot Presence % Frequency % Presence % Frequency % pseudovalue pseudovalue index index

11 975 Figure 3. Percentage of annuals, perennial graminoids and perennial forbs in the different communities, considering their presence (open bars) and their frequency (dashed bars). The asterisk indicates the existence of significant differences among communities in the presence of perennial graminoids ( P<0.05).

12 976 Table 4. Significant Pearson correlation coefficients between the presence and frequence of the different guilds of species and the diversity indexes and pseudovalues. Within-community diversity Within-plot diversity Shannon Inv. Simpson Shannon Inv. Simpson Significant Pearson correlation coefficients pseudovalue pseudovalue index index Moist community % presence annuals NS NS NS NS % presence perennial graminoids NS NS NS b % presence perennial forbs NS NS NS NS % frequency annuals NS NS NS NS % frequency perennial graminoids NS NS NS NS % frequency perennial forbs NS NS NS NS Mesic community % presence annuals a b NS NS % presence perennial graminoids b c NS NS % presence perennial forbs NS NS NS NS % frequency annuals a a NS NS % frequency perennial graminoids b b NS NS % frequency perennial forbs NS NS NS NS Xeric community % presence annuals NS NS NS NS % presence perennial graminoids NS NS NS NS % presence perennial forbs NS NS NS NS % frequency annuals NS NS NS NS % frequency perennial graminoids NS NS NS NS % frequency perennial forbs NS NS NS NS a P<0.01; b P<0.05; c P<0.06. NS not significant. Discussion Species richness, diversity patterns and mechanisms involved Species richness in Urbasa-Andia rangelands was high and similar to the richness observed in some British, Dutch and Swedish rangelands (During and Willems 1984; Grubb 1986; Van der Maarel 1988b), although it did not reach the values reported in some Mediterranean grassland communities extremely rich in species (40 60 species per 1 m 2 ; Marañon 1986). In contrast with Sebastià (1991) who found in the southern Pyrennees that subalpine mesic grasslands were richer than xeric ones, we reported similar number of vascular plants in xeric, moist and mesic communities (Figure 1). Propagule availability (including species coming from the nearby forest) and better climatic conditions may explain the higher number of species obtained in xeric montane communities, compared to subalpine ones. Unlike species richness, diversity indices discriminated the communities quite well. Moist and xeric communities displayed higher mean values for most of the diversity indices calculated (Table 2). Moist and xeric rangelands developing in the

13 977 area are characterized by a low level of basic soil resources and a high environmental heterogeneity. Both mechanisms may increase the diversity of grassland communities (Grime 1973; Huston 1994). The scarcity of soil resources slows down the rate of competitive displacement between species, increasing the diversity of the communities (Fowler and Antonovics 1981: Janssens et al. 1998). Moist rangelands, developed on podzolic soils, have a low nutrient availability (mainly phosphorus, Canals and Sebastià, in press) and may suffer severe stresses from the hydric level (waterlogged conditions in moist periods and scarcity of water in summer due to sandy textures). In xeric areas, stresses may be related as well to water supply, strongly limited in summer months. Environmental heterogeneity enhances diversity by increasing the possibility of coexistence of species with separate ecological niches (Grubb 1977; Pineda et al. 1981). Temporal heterogeneity in moist rangelands might be mainly caused by the fluctuating water supply, suggested by the fact that the plot that most contributes to the diversity of the community displays a mixture of species tolerating damp drought conditions. Spatial heterogeneity in xeric areas is caused by abiotic factors such as slope, variable soil depth and presence of outcrops, and is enhanced by the scarce and clumped cover of the vegetation and the minute size of many of the species joining this community (Canals 1997). The scarcity of soil and water and the existence of outcrops in xeric rangelands favor an aggregated, tight horizontal structure of the vegetation. New propagules may arrive at random and establish in this patchy, clumped vegetation pattern. Higher coefficients of variation among 1 m 2 quadrats in xeric plots (Figure 1), lower diversification of perennial graminoids, and a high presence of annuals may confirm this idea (Figure 3). Mesic rangelands, which develop under less stressing conditions than xeric and moist communities, displayed the lowest diversity mean values (Table 2). The pattern observed opposes Whittaker s suggestion that favorable conditions enhance community diversity (Whittaker 1965). Although favorable conditions in mesic rangelands may increase the chances of species establishing in the community, aboveground constraints and competitive relationships increase when water stress decreases (Burke et al. 1998). In many grassland communities, diversity has proved to be tightly related to the outcome of the competition between species (Tilman 1982). A dense vegetation cover in mesic rangelands suggests that, at least, competition for light and space is common. This competition may be reflected by the higher dominance values found in mesic rangelands, promoted by several perennials (Tables 1 and 2). In these areas, the enhancement of the diversity may be dependent on some external factors, such as biotic disturbances. We observed that the plots that most increased the diversity of this community where those that experienced a more intense grazing regime. The effects of herbivory and other biotic disturbances may promote the establishment of new species (Levassor et al. 1990; Wheeler and Shaw 1991), that increase the diversity of the community (Table 3) and contribute to maintain an important pool of species, as high as that of the rest of the communities (Figure 1).

14 978 Guilds of species and its relationship to diversity At the three communities studied, perennial species were the most diverse and abundant. Within the matrix of perennials, annuals developed, appearing more diverse in drier, xeric sites (Figure 3). Despite their lower abundance, the encroachment of annuals, many of them ruderals (Anthemis arvensis, Lathyrus aphaca, Veronica arvensis, Poaannua, Trifolium glomeratum...) (Appendix 1), had profound effects on the diversity of the mesic rangelands. In fact, the increase in diversity of the mesic community was mainly caused by the entry of annuals (Table 4). In the study area, biotic disturbances have been observed to decrease the cover of the dominant perennial taxa and to enhance the establishment of short-lived species (Canals and Sebastià, in press). Various researchers have also recognized the role of biotic disturbances in the balance between annuals and perennials in grassland communities (Tilman 1983; Collins and Uno 1985). However, in grasslands developed under less favorable conditions, relationships between short-lived species and community diversity may not be as apparent. More stressful conditions may decrease the number of ruderals able to cope with these constraints. This may occur in moist rangelands, subjected to an intense disturbance regime, where no relationship between annuals and community diversity was observed (Tables 3 and 4). Final remarks Temperate natural and seminatural grasslands are among the most threatened ecosystems in Europe (Baldock 1990). The decline of traditional shepherding and the fragmentation of the landscape has caused a rapid loss of richness in these ecosystems (Fischer and Stocklin 1997). For that reason, an increasing concern exists about the importance of maintaining grazing practices that avoid the complete dominance of the most competitive species, enhance species dispersal and regenerate the richness and the diversity of the communities (Zobel et al. 1998). In this study, the diversity of mesic rangelands appears tightly dependent on the maintenance of these grazing practices, whereas diversity in more stressed communities may depend primarily on intrinsic phenomena, such as environmental heterogeneity and resource supply. Several authors have indicated that the establishment of species of high environmental value in European temperate grasslands is enhanced by free-range grazing, which allow a flow of species from one grassland to another (Dean et al. 1997; Poschlod et al. 1998). However, traditional grazing also favors the dispersal of species from different habitats such as weeds of lowland arable fields (where nomadic cattle spend winter months) (Malo and Suarez 1995). The establishment of these ruderals, many of them short-lived species, may particularly enhance the diversity of mesic communities. Following Magurran (1989), diversity is not always a synonym of ecological quality. Species richness and diversity are only valuable when applied to the species belonging to a particular ecosystem (Ratcliffe 1986). In Urbasa-Andia range-

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18 982 Appendix 1 List of perennial forbs, perennial graminoids and annuals common to the three communities, shared by two communities or found in only one type of community. Nomenclature follows Aseginolaza et al. (1984). Perennial forbs Perennial graminoids Annuals Species common to xeric, mesic and moist plots Achillea millefolium Agrostis capillaris Airacaryophyllea Asperula cynanchica Anthoxanthum odoratum Aphanesarvensis Bellis perennis Avenula marginata Cerastiumdiffusum Centaurea jacea subsp. sulcata Euphrasiasalisburgensis Cerastium arvense Brachypodium pinnatum Linumcatharticum Cerastium fontanum subsp. vulgare Briza media Medicagolupulina Chamaemelum nobile Carex caryophyllea Moenchiaerecta Cirsium eriphorum Cynosurus cristatus Myosotisdiscolor Crataegus monogyna Danthonia decumbens Petrorhagiananteulii Erica vagans Festuca gr. rubra Poaannua Eryngium burgatii Festuca indigesta Trifoliumcampestre Filipendula vulgaris Koeleria vallesiana Trifoliumscabrum Galium gr. pumilum Lolium perenne Trifoliumstriatum Galium verum subsp. verum Luzula campestris Veronicaarvensis Helianthemum nummularium Phleum pratense subsp. Vulpiamyuros Herniaria latifolia bertolonii Hieracium gr. pilosella Hypochoeris radicata Juniperus communis Leontodon autumnalis subsp. autumnalis Lotus alpinus Merendera montana Pimpinella saxifraga Plantago lanceolata Plantago media Polygala vulgaris Potentilla montana Potentilla tabernaemontani Ranunculus bulbosus Ranunculus montanus Scabiosa xolumbaria Scilla autumnalis Sedum album Sedum amplexicaule Taraxacum gr. erythrospermum Thymus polytrichus subsp. polytrichus Trifolium pratense Trifolium repens Species common to xeric and mesic plots Arenaria grandiflora subsp. grandiflora Avenula mirandana Acinosarvensis Carduncellus mitissimus Bromus erectus subsp. erectus Arenariaserpyllifolia Carduus nutans Carex brevicollis Bombycilaenaerecta Carlina acanthifolia subsp. cynara Trisetum flavescens subsp. Brachypodium Carlina vulgaris flavescens distachyon

19 983 Appendix 1. Continued. Perennial forbs Perennial graminoids Annuals Dianthus monspessulanus Eryngium campestre Euphorbia flavicoma subsp. occidentalis Gentiana verna Geum sylvaticum Hippocrepis comosa Medicago suffruticosa Minuartia verna Prunella laciniata Sanguisorba minor Scilla verna Sedum acre Seseli montanum Trinia glauca Vicia pyrenaica Bromushordeaceus subsp. hordeaceous Bupleurumbaldense subsp. baldense Cerastiumpumilum Erodiumcicutarium Euphrasiaalpina Filagopyramidata Geraniummolle Leontodonsaxatilis subsp. hispidus Minuartiahybrida Sherardiaarvensis Trifoliumdubium Valerianellamicrocarpa Species common to mesic and moist plots Convolvulus arvensis Poa supina Vulpiamuralis Hieracium auricula Potentilla erecta Prunella grandiflora subsp. grandiflora Prunella vulgaris Pteridium aquilinum Rumex acetosella Trifolium ochroleucon Species only found in xeric plots Acinos alpinus Carex depressa Alyssumminus Alchemilla flabellata Cares humilis Anthyllisvulnearia Allium senescens subsp. montanum Dactylis glomerata Arenariaobtusiflora Allium vineale Phleum phleoides subsp. ciliaris Androsace villosa Poa alpina Cerastiumglomeratum Arabis scabra Cochleariaaragonensis Armeria pubinervis Desmazeriarigida Asplenium ruta-muraria subsp. rigida Bupleurum flacatum Erophilaverna Campanula glomerata Euphorbiaexigua Campanula gr. rotundifolia Geraniumcolumbinum Campanula macrorhiza Minuartiarubra Centranthus lecoqii Saxifragatridactylites Coronilla minima Sclerathusannuus Daphne laureola Seneciovulgaris Draba aizoides Sonchusoleraceous Erodium glandulosum Torilisnodosa Genista hispanica subsp. occidentalis Globularia nudicaulis Helianthemum canum Hepatica nobilis Ononis striata

20 984 Appendix 1. Continued. Perennial forbs Perennial graminoids Annuals Phyteuma orbiculare Polygala serpyllifolia Saxifraga granulata Seseli cantabricum Teucrium pyrenaicum Species only found in mesic plots Carlina acaulis Poa compressa Anthemisarvensis Crepis capillaris Capsellabursa-pastoris Crocus nudiflorus Gastridiumventricosum Dianthus pungens subsp. brachyanthus Geraniumpusillum Echium vulgare Lathyrusaphaca Prunella grandiflora subsp. pyrenaica Papaverhybridum Prunus spinosa Trifoliumglomeratum Silene nutans Trifoliumsubterraneum Spiranthes spiralis Vicia sp. Stachys officinalis Viola reichenbachiana Species only found in moist plots Calluna vulgaris Carex demissa Juncusbufonius Cardamine pratensis Carex flacca Logfiaminima Cirsium pyrenaicum Carex hirta Ornithopusperpusillus Cruciata glabra Deschampsia cespitosa Parentucellialatifolia Daboecia cantabrica Holcus lanatus Plantagocoronopus Dianthus carthusianorum Juncus articulatus Radiolalinoides Equisetum palustre Juncus effusus Scirpussetaceus Galium saxatile Trifoliummicranthum Genista anglica Tuberariaguttata Gentiana pneumonante Hypericum humifusum Leontodon saxatilis subsp. saxatilis Lotus tenuis Mentha pulegium Pedicularis sylvatica subsp. sylvatica Potentilla reptans Ranunculus acris Ranunculus flammula Ranunculus paludosus Ranunculus repens Sagina procumbens Serratula tinctoria Silaum silaus Succissa pratensis Taraxacum gr. officinale Thymus pulegioides Trifolium fragiferum Veronica serpyllifolia subsp. humifusa Viola sylvestris subsp. riviniana