Assessment of vegetation performance on semicoke dumps of Kohtla-Jarve oil shale industry, Estonia/Kohtla-Jarve poolkoksimagede taimkatte seisund.
As the global supplies of crude oil are decreasing, other fossil fuels (like coal and oil shale) may gain importance. Oil shale, a relatively less known fossil fuel, contains a significant amount of kerogen, from which liquid hydrocarbons can be extracted. The global supply of oil shale was estimated at 411 Gt in 2005 (Andrews, 2006), but oil shale has an economic value only for 33 countries with the USA, Russia, and Brazil accounting for 86% of the world's oil-shale resources (Brendow, 2003). According to the report by EASAC (2007), the world's leading oil shale producer in 2005 was Estonia (70% of the world's total production), where oil shale is used for power generation, oil production, cement production, and by the chemical industry.
Mining and processing of oil shale have caused several environmental problems in North-East Estonia (Raukas & Punning, 2009). When used for oil extraction, approximately half of the oil shale turns into semicoke during pyrolysis. Although the semicoke has been utilized as a building material, road filling material, and growth substrate for plants (Kaar, 2002; Raave et al., 2004; Varnik et al., 2006; Harzia et al., 2007; Motlep et al., 2007), it has little value for industry and has therefore been dumped near chemical plants since the beginning of oil extraction in the 1930s. As manmade hills, these semicoke dumps form remarkable landmarks in the landscape of North-East Estonia (Luud et al., 2003).
Freshly deposed semicoke contains a large amount of phenols and has therefore been regarded as a hazardous substance. Phenols and other pollutants seep from the fresh semicoke and pollute the catchment area of creeks and rivers that flow into the Gulf of Finland. Another major problem is the emission of polycyclic aromatic hydrocarbons (PAHs) and dust that comes from the fine-grained material of semicoke dumps (Orupold & Henrysson, 1999; Raave et al., 2004). Also, various hazardous chemical compounds (e.g., arsenic acid), which were once used in the oil extraction process, have been buried to Kohtla-Jarve semicoke dumps. Some of the semicoke dumps have self-ignited and the burning process is still continuing causing the emission of hydrogen sulphide ([H.sub.2]S), ammonia (N[H.sub.3]), and heavy metals into the air (Raave et al., 2004; Oja et al., 2007).
Afforestation has been considered to be the most sustainable way of restoring the productivity of land damaged by oil-shale mining and industry (Vaus, 1970; Kaar, 2002). Since 1971, more than 160 thousand trees have been planted to semicoke dumps in North-East Estonia in order to establish a vital plant cover and to initiate soil formation (Kaar, 2003). The most productive tree species have been broadleaved trees such as Alnus glutinosa and Betula pendula, while conifers do not perform well on the semicoke dumps (Kaar, 2003). Ostonen et al. (2006) showed that the bioaugmentation of semicoke by supplying phenol-degrading bacteria to the substrate might improve the growth of B. pendula. The successful establishment of the tree layer on the semicoke dumps reduces significantly dust emissions (Kaar, 2003).
Natural dispersal of vegetation on semicoke dumps has attracted much less scientific attention than afforestation. However, naturally grown areas together with planted areas have proven to be a great success in creating diverse plant communities in wastelands (Lamb et al., 2005; Hobbs et al., 2006). For example, the self-grown vegetation of Kohtla-Jarve semicoke dumps includes several protected plant species, which were found by students of a local gymnasium during their school project (Schmidt, 2006).
The aims of this study were (1) to determine the distribution of different vegetation types on the Kohtla-Jarve semicoke dumps by creating a digital vegetation map, (2) to compare the performance of vegetation and the formation of organic soil in different vegetation types, and (3) to analyse the significance of semicoke dumps as a habitat for protected plant species.
MATERIAL AND METHODS
The study was conducted in an area where semicoke is dumped in Kohtla-Jarve, North-East Estonia (59[degrees]23'N, 27[degrees]13'E). The semicoke dumps are located in the Viru Plateau landscape region, which is an Ordovician limestone plateau. The mean monthly temperatures in the area range from -7 [degrees]C in January to 16 [degrees]C in July; the mean annual precipitation varies between 600 and 700 mm. The absolute altitude of the region is between 30 and 50 m above sea level (Arold, 2005).
Approximately 73 million tonnes of waste material has been deposited on the Kohtla-Jarve semicoke dumps since the 1930s. In total, the semicoke dumping site in Kohtla-Jarve occupies 2.2 [km.sup.2]. However, our study area covered only the older part of the sites where semicoke was dumped from the mid-1930s until the mid-1990s. This old dumping area covers 1.3 [km.sup.2] and contains seven semicoke hills grown together. The ridge of the hills is more than 100 m long and the hillside slopes may reach up to 60 degrees. The ridges are directed from east to west, so that hillsides are open to north and south (see Fig. 1). The maximum absolute height of the hills is 172 m and their maximum relative height is 127 m (Pae et al., 2005). The landscape in the study area is highly mosaic with ridges and sharp hillsides alternating with small valleys and plains. The semicoke dumping area was previously covered with fields and semi-natural meadows interspersed with moist mixed forests. Today the same landscape surrounds the area in north and west, whereas industrial and residential areas are located in east and south.
As semicoke is black-coloured, the surface temperature of the semicoke dumps may rise to high levels during summer months. The ground texture on the surface of the dumps is mostly coarse-grained, so the topmost layer of semicoke is prone to droughts. However, at a depth of 5-30 cm, the ground is fine-grained and its water holding capacity is much higher. The pH of fresh semicoke is more than 12, but over time the pH of the topmost layers declines (Ostonen et al., 2006). The composition of the mineral matter of semicoke is relatively uniform. Predominant components in the fresh semicoke are calcite, dolomite, quartz, K-feldspar, and clay minerals (Motlep et al., 2007). During deposition, the composition of semicoke changes as unstable phases of minerals are replaced by a considerable amount of ettringite (a Ca-Al-sulphate) (Motlep et al., 2007). As the growth substrate for plants, semicoke is a relatively poor material with low concentrations of nitrogen and phosphorus but with a relatively high concentration of potassium (Kaar, 2002).
In the first phase of vegetation analysis, the vegetated areas of the semicoke dumps were determined on the areal photos issued by the Estonian Land Board. These vegetated areas were studied in some detail in June and July 2004 and 2006, when 76 plots of 10 m x 10 m were established in the study area. The potential locations for the plots were pre-selected on the areal photos. The selection criterion was even distribution of the plots across the vegetated area of the semicoke dumps. In each plot, the vegetation was divided into tree layer (including shrubs) and herbaceous layer. In the tree and shrub layer, the species composition and the performance (number of healthy plants divided by the total number of plants) of different species were assessed. The origin of the tree layer (either planted or natural) was determined, based on the information found from old reclamation projects. In the herbaceous layer, the presence of herbaceous species was recorded and the general coverage of vegetation was assessed. When the herbaceous layer was very poor and sparse (only a few species or plants were present), the occurrence of species was recorded across a whole plot; in the cases the herbaceous layer was prosperous, quadrates of 1 m x 1 m were used to count plant species. The number of quadrates within a plot depended on the heterogeneity of the herbaceous layer and ranged from two to five. The quadrates were located evenly within plots. The forest floor depth (total thickness of the first generic soil horizons: litter, fermentation, and humus) was assessed in triplicates on each plot.
Based on the areal photos and the data of field observations, a vegetation map of the semicoke dumping area was created (using MapInfo Professional version 5). From the created digital map, the areas of different vegetation types and the hill slopes were measured. The vegetation types were arbitrarily distinguished according to the species composition and origin of the tree and shrub layer (see Table 1). For example, 'Betula10 planted' represents the vegetation where 10-year-old planted saplings of Betula pendula are dominant in the tree layer, whereas 'Betula10 natural' is a natural vegetation type where the dominating Betula pendula is 10 years old.
In the next step of data analysis, it was checked whether the species composition of herbs was affected by the properties of the tree and shrub layer (i.e., whether the herbaceous layer could be divided among the vegetation types distinguished according to the tree and shrub layer). Prior to any further analysis of the herbaceous layer, a species-area curve was plotted to check whether 76 sampling plots gave a sufficient overview of the most common herbs in the study area. All herbaceous species were divided among Grime's (1979) competitive (C), stress-tolerant (S), and ruderal (R) plant strategies. Plants are exposed to stress (resource limitation) and disturbance (biomass removal) to a variable extent, which leads to the S and R strategies. The C strategy characterizes plants that grow in resource rich (no stress) and undisturbed habitats. Besides there are combinations and intermediate strategy types including the indifferent CSR strategy. Additional information on the strategy types was obtained from Grime et al. (1988) and Hunt et al. (2004).
To describe the patterns in the species composition of herbs, we used nonmetric multidimensional scaling (NMS; McCune & Grace, 2002). The input data were the presence of herbaceous species in a study plot; only the species that occurred in at least two plots were included in the analysis. Two different data sets were used in NMS: one included all vegetation types, while the other included only the vegetation types where Betula pendula dominated in the tree layer (Betula chronosequence data). Before running NMS, the presence data of herbaceous species were transformed by using Booleyan smoothing. A random starting configuration and Sorensen's distance measure were applied in NMS. We used PC-ORD version 5 to do NMS. Pearson's correlation r was computed between vegetation data and environmental variables using SigmaPlot 10.
In total, 12 different vegetation types were identified: 11 where trees or shrubs dominated in the vegetation and one where only herbaceous vegetation was present (Fig. 1, Table 1). Together, these 12 vegetation types covered 0.89 [km.sup.2], that is about 70% of the study area. The area where trees dominated was 0.55 [km.sup.2].
The most common tree species was Betula pendula. The population of planted B. pendula covered 0.35 [km.sup.2] and an extra 0.19 [km.sup.2] was covered by naturally grown B. pendula stands (Table 1). Populus balsamifera was the second most abundant planted tree species on the semicoke dumps. This exotic species had started to spread naturally on the semicoke dumps. Most of the more than 20-year-old P. balsamifera trees were not healthy and had dead branches in their canopies, while in the mixed stands where it was not a dominant species, P. balsamifera was healthy. In total, P. balsamifera stands covered 0.11 [km.sup.2] (Table 1). Of other vegetation types, the treeless cover of herbaceous species occupied the largest area (0.21 [km.sup.2]; 'Grass natural' in Table 1).
In the understory, the dominating species were B. pendula, P. balsamifera, and P. tremula. The naturally grown Salix spp. population was abundant (Table 1). The exotic species Hippophae rhamnoides and Elaeagnus commutata had renewed well and spread almost everywhere on the semicoke dumps (Table 1). A small set of Pinus mugo had also been planted on the semicoke dumps; however, this species did not perform as well as other understory species.
There was no humus layer in the young B. pendula and P. balsamifera stands. An up to 2-cm-thick humus layer with leaf mould had developed in 20-year-old and older B. pendula stands. The thickest forest floor was measured in the Alnus30 planted' vegetation type; however, comparison of mean values of forest floor thickness indicated that differences among vegetation types were insignificant (one-way ANOVA, F = 2.5, P = 0.06; only the vegetation types where the forest floor layer occurred at least in one study plot were included in the analysis).
[FIGURE 1 OMITTED]
The total number of herbaceous species recorded across all stand types was 64. The first order jackknife estimate was 85 species and the second order jackknife estimate was 94 species (see McCune & Grace, 2002 for more information about the jackknife method). Thus, 76 study plots gave a sufficient overview of the species composition of herbaceous vegetation. The highest number of herbaceous species was found in the 'Betula20 natural' vegetation type, the lowest in the Grass natural' vegetation type (Table 2). The coverage of herbaceous vegetation was the highest in the 'Alnus30 planted' vegetation type (Table 1). The general coverage of herbaceous vegetation did not correlate with the hill slope (r = 0.22, P = 0.3), as there were bare plots also in areas with the zero slope. However, no vegetation grew in areas where the slope was more than 50 degrees and no study plots were established in such areas.
The most abundant species in the herbaceous vegetation was Achillea millefolium, which occurred in 46 plots, followed by Tussilago farfara and Taraxacum officinale (both in 41 plots). Pyrola rotundifolia occurred in 25 plots (Table 2). The processing of species composition data using NMS ordination resulted in a three-dimensional solution both for all vegetation types (final stress 10.3, final instability < 0.001, 250 randomized runs in the Monte Carlo test, P = 0.004) and for the Betula chronosequence data (final stress 10.0, final instability < 0.001, 250 randomized runs in the Monte Carlo test, P < 0.01). Cumulatively, the NMS axes explained 90% of the variance in the species composition of all vegetation type data, and 94% of the variation in the species composition of the Betula chronosequence data. In both cases, the study plots of different vegetation types were homogeneously distributed across the NMS space, indicating that the species composition of herbs did not differ among vegetation types (Fig. 2). In the case of the all vegetation type dataset, the slope of semicoke dumps correlated significantly with the 3rd NMS axis (r = 0.41, P = 0.04). Consequently, the species composition of herbaceous vegetation was affected by the hill slope.
Most herbaceous vegetation species were naturally grown and common to wasteland areas with low soil fertility. As regards plant strategy types, generalists (CSR-strategy), stress-tolerant species, and ruderals were dominant in the herbaceous vegetation (Table 2). The presence and abundance of several orchid species (Dactylorhiza baltica, D. fuchsii, D. incarnata, D. maculata, Epipactis atrorubens, E. helleborine, and Orchis militaris) in the herbaceous vegetation was somewhat surprising as some of them (e.g., O. militaris) did not occur in the areas surrounding the semicoke dumps of Kohtla-Jarve.
[FIGURE 2 OMITTED]
DISCUSSION AND CONCLUSIONS
The assessment of the success of reclamation depends on the initial goals of the project. The aim of the re-establishment of vegetation is often just to prevent erosion and to add economic value to the degraded lands. This involves planting fast-growing trees, which often results in the establishment of mono-specific plantations of exotic species on the degraded landscapes (Hunter et al., 1998). However, as the loss of biodiversity has become more serious, ecologically sound restoration of degraded ecosystems challenges environmental scientists. Thus, it has become particularly important to achieve the same biodiversity in degraded landscapes that was present before degradation or that is characteristic of surrounding non-degraded areas (Palik et al., 2000). For that reason, the selection of planting material has a crucial significance as tree species that may fulfil the less difficult goal of reclamation may have negative effects on the recovery of biodiversity (e.g., Holl, 2002; Pensa et al., 2008).
The Kohtla-Jarve semicoke dumping area has been reclaimed by planting approximately 34 different tree and shrub species (26 of them exotic) (Kaar, 2003). From the economic point of few, Betula pendula has been the optimal choice for planting as this species survives well under the conditions prevailing on the semicoke dumps (Kaar, 2003). As our results indicate, the formation of a substantial humus layer in the stands dominated by B. pendula takes about 20 years. The coverage of herbaceous vegetation is variable but increases with the age in Betula stands. As compared to B. pendula, Alnus glutinosa enhances the growth of herbaceous species and the formation of a soil layer. Thus, if the performance of herbaceous vegetation is prioritized, then planting with A. glutinosa should be preferred to B. pendula in flatter areas. The species of Alnus form symbiotic relationship with N2-fixing actinomycetes (Huss-Danell, 1997) and influence soil fertility and vegetation productivity through nitrogen-rich leaf litter (Huss-Danell, 1986; Rothe et al., 2002; Uri et al., 2002). For example, in reclaimed oil-shale opencasts, the presence of A. glutinosa in the tree layer affects positively the productivity of herbaceous species and soil formation (Pensa et al., 2004, 2008).
High percentage of Populus stands on the Kohtla-Jarve semicoke dumps is connected to the wide use of these species in creating green belts in industrial towns in the former Soviet Union. However, except for P. tremula, all other Populus species are alien to the Estonian flora and cause problems at the time of seed dispersal. As compared with B. pendula, Populus spp. do not thrive on semicoke dumps, and thus, their use as a planting material is not justified. From the exotic species that had started to spread on the semicoke dumps, Elaeagnus commutata and Hippophae rhamnoides suppressed almost all other plant species in areas where they dominated. Hence, although both of them help to prevent erosion, their use in reclamation projects has a negative influence on the recovery of biodiversity.
The composition of herbaceous vegetation did not show any distinctive characteristics in different vegetation types. Most of the species were common for wastelands or were generalists without any specific habitat requirements. This indicates that irrespective of the traits of the tree layer, the herbaceous vegetation is in the initial stages of its development and has not yet diverged according to properties of the tree layer. The dominance of ruderals and generalists is typical of areas that are in the first stages of the recovery from a disturbance (Grime et al., 1988). From the 64 recorded herbaceous species, only one, Festuca rubra, was sown; others had spread naturally to the dumps. Only three herbaceous species recorded are old forest species according to Hermy et al. (1999) (Table 2).
Although several protected orchid species were abundant in the study area, the value of the vegetation as the habitat for protected species was low. None of these protected orchid species is rare or endangered in the Estonian flora (Kukk & Kull, 2005) and the law does not require the protection of their habitats. However, the higher abundance of orchids on the semicoke dumps as compared with surrounding forests indicates that the conditions on the dumps are especially suitable for these species. One reason might be the high abundance of fungi, which are essential for the germination of orchid seeds; another reason might be the low abundance of competitive plant species, which might suppress the growth of orchids (which are mainly stress-tolerant species; Grime et al., 1988). This explains why only one orchid species was present in the Alnus stands, where the coverage of herbaceous vegetation was the highest.
The vegetation cover of disturbed ecosystems depends also on geomorphology, especially the slope gradient. The steep hillsides are open to soil erosion, although a dense vegetation cover with a humus layer can reduce it (Robichaud, 2005). In our study sites, the topsoil texture was gravelly and not solid. Therefore the young vegetation cover on dumps with no humus layer is vulnerable to erosion, especially on steep hillsides. So, the slope of the dump tended to affect the species composition of herbaceous vegetation. Although there was no firm correlation between the slope and vegetation cover, we found almost no vegetation in the steepest parts of hillsides near the ridges, particularly on the southern slopes. Extra activities are needed for the reclamation of those slopes. While microorganisms are essential for reducing the toxicity of semicoke (by biodegrading phenols) (e.g., Juhanson et al., 2007; Truu et al., 2007), the vegetation reduces topsoil erosion and the emission of semicoke dust into the air. Thus, the full coverage of the Kohtla-Jarve semicoke dumps with vegetation is an essential task, which, however, cannot be achieved without levelling the dumps.
In conclusion, our results confirm that the planting of Betula pendula in order to reclaim the semicoke dumping area has been a successful option, while the use of Populus spp. is not justified. Alnus glutinosa can give even better results than B. pendula in terms of promoting the formation of diverse herbaceous vegetation. The exotic species Elaeagnus commutata and Hippophae rhamnoides tend to suppress ground vegetation and planting with these species should be avoided if the recovery of herbaceous diversity is among the targets of reclamation. The significance of the Kohtla-Jarve semicoke dumping area as habitat for protected species is low, thus, there are no restrictions for re-shaping the dumps in order to reduce the slopes of the hills.
Mr Harry Sonford checked the language of the manuscript. The fieldwork was conducted and the vegetation data were collected within a project supported by the Estonian Science Foundation (grant No. 5764) and project 0282119s02 financed by the Ministry of Education and Research, Estonia.
Received 18 September 2009, revised 14 December 2009
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Riina Vaht (a), Margus Pensa (b,c) **, Mait Sepp (a), Aarne Luud (d), Helen Karu (e), and Tiina Elvisto (c)
(a) Department of Geography, University of Tartu, Vanemuise 46, 51014 Tartu, Estonia
(b) Institute of Ecology, Tallinn University, Pargi 15, 41537 Johvi, Estonia
(c) Institute of Mathematics and Natural Sciences, Tallinn University, Narva mnt. 25, 10120 Tallinn, Estonia
(d) Department of Environmental Protection, Estonian University of Life Sciences, Kreutzwaldi 64, 51014 Tartu, Estonia
(e) Department of Botany, University of Tartu, Lai 40, 51005 Tartu, Estonia
** Corresponding author, email@example.com
Table 1. Characteristics of vegetation types distinguished according to the properties of the tree and shrub layers on Kohtla-Jarve semicoke dumps Vegetation type Planted species Natural species Betula10 Betula pendula, Populus Elaeagnus commutata, planted balsamifera, Pinus Salix sp. mugo Betula10 Betula pendula, Populus natural balsamifera, Salix sp. Betula20 Betula pendula, Populus balsamifera, planted Hippophae Populus tremula rhamnoides, Swida sp., Caragana arborescens, Elaeagnus commutata, Padus avium Betula20 Hippophae rhamnoides Betula pendula, Populus natural balsamifera, Populus tremula, Pinus sylvestris, Picea abies, Salix sp. Betula30 Betula pendula Populus balsamifera, planted Populus tremula, Pinus sylvestris, Salix sp. Alnus30 Alnus glutinosa Betula pendula, Populus planted tremula, Alnus glutinosa Alnus30 Alnus glutinosa, Betula natural pendula, Populus balsamifera, Populus tremula, Sorbus aucuparia, Salix sp. Populus30 Populus balsamifera, Populus balsamifera, planted Hippophae rhamnoides Betula pendula, Sorbus aucuparia, Swida sp. Populus20 Populus balsamifera, natural Betula pendula, Sorbus aucuparia, Cornus sp. Hippophae Hippophae rhamnoides Elaeagnus Elaeagnus commutata Betula pendula, Populus tremula Grass Betula pendula, Populus natural balsamifera Average Coverage Vegetation Area, forest floor of herb No. of type [km.sup.2] depth, cm (SD) layer, % plots Betula10 0.22 0 (0) 5-20 5 planted Betula10 0.09 0 (0) 5-10 11 natural Betula20 0.08 2.22 (2.54) 50 13 planted Betula20 0.10 1.08 (1.50) 10-50 16 natural Betula30 0.05 3 (2.83) 40 12 planted Alnus30 0.01 7.3 (4.62) 100 4 planted Alnus30 0.005 2 (0.82) 50 1 natural Populus30 0.09 1.2 (1.30) 10-20 6 planted Populus20 0.02 0 (0) 5 4 natural Hippophae 0.003 2 (1.8) 0-10 1 Elaeagnus 0.002 0 (0) 0 1 Grass 0.21 0 0-5 2 Natural Table 2. Occurrence of herbaceous species in different vegetation types on the semicoke dumps in Kohtla-Jarve. The numbers indicate in how many study plots the species were found within a vegetation type (relative number of the study plots where the species occurred is in parentheses). Protected species are in bold, old forest species (according to Hermy et al., 1999) are marked with an asterisk. Strategy types are according to Grime's (1979) C-S-R plant strategies (C - competitive, S - stress-tolerant, R - ruderal) Strategy Betula10 Betula10 Species type planted natural Achillea millefolium CR/CSR 2 (0.4) 5 (0.5) Agrostis capillaris CSR Anthemis tinctoria R 1 (0.2) 3 (0.3) Artemisia absinthium CR/CSR 1 (0.2) 1 (0.1) Artemisia campestris 1 (0.1) Artemisia vulgaris C/CR 1 (0.1) Barbarea vulgaris R/CR 2 (0.4) Calamagrostis epigeios C/SC 3 (0.6) 4 (0.4) Campanula rotundifolia S Campanula trachelium * CSR Carduus crispus CR 1 (0.2) 1 (0.1) Centaurea jacea 1 (0.2) Cerastium holosteoides 2 (0.4) Cerastium sp. Cirsium arvense C Convallaria majalis * S/SC Crepis sp. 4 (0.4) Dactylis glomerata C/CSR Dactylorhiza baltica (#) S/CSR 1 (0.1) Dactylorhiza fuchsii * (#) S/CSR Dactylorhiza incarnata (#) S/CSR Dactylorhiza maculata (#) S/CSR 1 (0.2) Daucus carota SR/CSR Deschampsia cespitosa SC/CSR 1 (0.2) 2 (0.2) Echium vulgare R/CSR 1 (0.1) Epilobium angustifolium 4 (0.4) Epilobium sp. Epipactis atrorubens (#) S 1 (0.2) 2 (0.2) Epipactis helleborine (#) S Erucastrum gallicum 1 (0.1) Erysimum cheiranthoides R Festuca pratensis CSR 4 (0.4) Festuca rubra CSR 1 (0.1) Galium album Leucanthemum vulgare C/CSR Medicago lupulina R/SR Medicago sativa C/CSR Medicago x varia C/CSR Melilotus albus CR Orchis militaris (#) S/SR Orthilia secunda Pastinaca sativa 2 (0.2) Pilosella officinarum S/CSR 2 (0.2) Pilosella sp. 1 (0.1) Pimpinella major CSR Poa angustifolia S/CSR 1 (0.1) Poa compressa S/CSR 3 (0.3) Poa palustris CSR Poa pratensis CSR 1 (0.1) Poa trivialis CR/CSR Potentilla heidereichii 1 (0.1) Potentilla intermedia 1 (0.2) Pyrola rotundifolia S 3 (0.3) Reseda lutea SR/CSR 3 (0.6) 2 (0.2) Sagina nodosa S/SR 1 (0.2) Silene pratensis 1 (0.1) Solanum dulcamara C/CSR Solidago virgaurea S/CSR 1 (0.1) Sonchus oleraceus R/CR 2 (0.2) Taraxacum officinale R/CSR 2 (0.4) 6 (0.6) Trifolium pratense CSR Tussilago farfara CR 4 (0.8) 7 (0.7) Valeriana officinalis CSR Vicia cracca C/CSR Total number of species 17 29 Betula20 Betula20 Betula30 Species planted natural planted Achillea millefolium 10 (0.8) 11 (0.7) 8 (0.7) Agrostis capillaris 1 (0.1) Anthemis tinctoria 5 (0.4) 3 (0.2) 2 (0.2) Artemisia absinthium Artemisia campestris 5 (0.3) Artemisia vulgaris 2 (0.2) 1 (0.1) Barbarea vulgaris Calamagrostis epigeios 1 (0.1) 7 (0.4) Campanula rotundifolia Campanula trachelium * Carduus crispus Centaurea jacea Cerastium holosteoides 1 (0.1) Cerastium sp. 1 (0.1) 1 (0.1) Cirsium arvense Convallaria majalis * Crepis sp. 4 (0.3) 4 (0.3) 3 (0.3) Dactylis glomerata 1 (0.1) Dactylorhiza baltica (#) 2 (0.2) 3 (0.2) 1 (0.1) Dactylorhiza fuchsii * (#) 1 (0.1) 1 (0.1) Dactylorhiza incarnata (#) 1 (0.1) Dactylorhiza maculata (#) 1 (0.1) 3 (0.2) 2 (0.2) Daucus carota 1 (0.1) Deschampsia cespitosa 2 (0.2) 1 (0.1) 3 (0.3) Echium vulgare 6 (0.4) Epilobium angustifolium 3 (0.2) 6 (0.4) 1 (0.1) Epilobium sp. Epipactis atrorubens (#) 3 (0.2) 3 (0.2) 4 (0.3) Epipactis helleborine (#) 1 (0.1) Erucastrum gallicum 2 (0.2) Erysimum cheiranthoides 1 (0.1) Festuca pratensis 1 (0.1) 2 (0.1) 5 (0.4) Festuca rubra 6 (0.5) 7 (0.4) 2 (0.2) Galium album 1 (0.1) Leucanthemum vulgare Medicago lupulina 1 (0.1) 6 (0.4) 2 (0.2) Medicago sativa 1 (0.1) 2 (0.2) Medicago x varia 2 (0.2) Melilotus albus 3 (0.2) 5 (0.3) 3 (0.3) Orchis militaris (#) 3 (0.2) 1 (0.1) 2 (0.2) Orthilia secunda 1 (0.1) Pastinaca sativa 6 (0.6) 8 (0.5) 4 (0.3) Pilosella officinarum 3 (0.2) Pilosella sp. 1 (0.1) 1 (0.1) 1 (0.1) Pimpinella major Poa angustifolia 2 (0.2) Poa compressa 3 (0.2) 7 (0.4) 1 (0.1) Poa palustris 4 (0.3) Poa pratensis 4 (0.3) Poa trivialis 2 (0.1) 2 (0.2) Potentilla heidereichii Potentilla intermedia Pyrola rotundifolia 3 (0.2) 9 (0.6) 4 (0.3) Reseda lutea 3 (0.2) Sagina nodosa Silene pratensis Solanum dulcamara 1 (0.1) 1 (0.1) Solidago virgaurea 6 (0.4) 1 (0.1) Sonchus oleraceus 1 (0.1) 1 (0.1) Taraxacum officinale 6 (0.5) 9 (0.6) 6 (0.5) Trifolium pratense 1 (0.1) Tussilago farfara 5 (0.4) 5 (0.3) 3 (0.3) Valeriana officinalis Vicia cracca 1 (0.1) 1 (0.1) Total number of species 34 38 24 Alnus30 Alnus30 Populus30 Species planted natural planted Achillea millefolium 4 (1.0) 1 (1.0) 4 (0.7) Agrostis capillaris Anthemis tinctoria 1 (1.0) 1 (0.2) Artemisia absinthium Artemisia campestris 1 (0.2) Artemisia vulgaris 1 (1.0) 2 (0.3) Barbarea vulgaris Calamagrostis epigeios 1 (1.0) 2 (0.3) Campanula rotundifolia 1 (1.0) Campanula trachelium * 1 (1.0) Carduus crispus Centaurea jacea 1 (1.0) 1 (0.2) Cerastium holosteoides Cerastium sp. Cirsium arvense 1 (0.2) Convallaria majalis * 1 (1.0) Crepis sp. 2 (0.5) 3 (0.5) Dactylis glomerata 2 (0.5) 1 (1.0) 1 (0.2) Dactylorhiza baltica (#) 1 (0.2) Dactylorhiza fuchsii * (#) 1 (0.2) Dactylorhiza incarnata (#) Dactylorhiza maculata (#) Daucus carota Deschampsia cespitosa 2 (0.5) 1 (0.2) Echium vulgare 2 (0.3) Epilobium angustifolium 4 (0.7) Epilobium sp. 1 (0.2) Epipactis atrorubens (#) 3 (0.8) 1 (1.0) 2 (0.3) Epipactis helleborine (#) Erucastrum gallicum 1 (0.2) Erysimum cheiranthoides Festuca pratensis 1 (0.2) Festuca rubra 1 (1.0) 2 (0.3) Galium album Leucanthemum vulgare Medicago lupulina Medicago sativa Medicago x varia Melilotus albus Orchis militaris (#) 1 (0.3) 3 (0.5) Orthilia secunda Pastinaca sativa 1 (1.0) 4 (0.7) Pilosella officinarum 2 (0.3) Pilosella sp. Pimpinella major Poa angustifolia Poa compressa 1 (1.0) 1 (0.2) Poa palustris Poa pratensis Poa trivialis 4 (1.0) Potentilla heidereichii Potentilla intermedia Pyrola rotundifolia 1 (1.0) 3 (0.5) Reseda lutea Sagina nodosa Silene pratensis 1 (0.2) Solanum dulcamara 2 (0.3) Solidago virgaurea 1 (1.0) 4 (0.7) Sonchus oleraceus 1 (0.2) Taraxacum officinale 4 (1.0) 1 (1.0) 5 (0.8) Trifolium pratense Tussilago farfara 4 (1.0) 1 (1.0) 5 (0.8) Valeriana officinalis 1 (0.2) Vicia cracca Total number of species 9 17 31 Populus20 Grass Species natural Hippophae natural Achillea millefolium 1 (1.0) Agrostis capillaris Anthemis tinctoria 1 (0.3) 1 (1.0) Artemisia absinthium Artemisia campestris Artemisia vulgaris Barbarea vulgaris 1 (0.5) Calamagrostis epigeios 1 (1.0) 1 (0.5) Campanula rotundifolia Campanula trachelium * 1 (0.3) Carduus crispus Centaurea jacea 1 (1.0) Cerastium holosteoides Cerastium sp. Cirsium arvense 1 (1.0) Convallaria majalis * Crepis sp. Dactylis glomerata Dactylorhiza baltica (#) Dactylorhiza fuchsii * (#) Dactylorhiza incarnata (#) Dactylorhiza maculata (#) Daucus carota Deschampsia cespitosa 2 (0.5) Echium vulgare 1 (0.3) 1 (1.0) Epilobium angustifolium 1 (0.5) Epilobium sp. Epipactis atrorubens (#) 1 (0.3) Epipactis helleborine (#) Erucastrum gallicum Erysimum cheiranthoides Festuca pratensis 2 (0.5) Festuca rubra 2 (0.5) 1 (1.0) Galium album Leucanthemum vulgare 1 (1.0) Medicago lupulina 1 (1.0) Medicago sativa Medicago x varia Melilotus albus Orchis militaris (#) Orthilia secunda Pastinaca sativa 1 (0.3) 1 (1.0) Pilosella officinarum Pilosella sp. Pimpinella major 1 (1.0) Poa angustifolia Poa compressa Poa palustris Poa pratensis Poa trivialis Potentilla heidereichii Potentilla intermedia Pyrola rotundifolia 2 (0.5) Reseda lutea 1 (0.3) 1 (1.0) 2 (1.0) Sagina nodosa Silene pratensis Solanum dulcamara Solidago virgaurea Sonchus oleraceus Taraxacum officinale 2 (0.5) Trifolium pratense Tussilago farfara 4 (1.0) 1 (1.0) 2 (1.0) Valeriana officinalis Vicia cracca Total number of species 12 13 5 Note: Protected species are indicated with (#), old forest species (according to Hermy et al., 1999) are marked with an asterisk.
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|Author:||Vaht, Riina; Pensa, Margus; Sepp, Mait; Luud, Aarne; Karu, Helen; Elvisto, Tiina|
|Publication:||Estonian Journal of Ecology|
|Date:||Mar 1, 2010|
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