NVC survey of Glims Moss & Durkadale SSSI and Loch of Banks SSSI

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1 COMMISSIONED REPORT Commissioned Report No. 078 Part 1 of 2 NVC survey of Glims Moss & Durkadale SSSI and Loch of Banks SSSI (ROAME No. F04LA14) For further information on this report please contact: Ruth Priestley Scottish Natural Heritage Junction Road KIRKWALL, ORKNEY KW15 1AW Telephone: Ruth.priestley@snh.gov.uk This report should be quoted as: Crossley, J. (2005). NVC survey of Glims Moss & Durkadale SSSI and Loch of Banks SSSI. Scottish Natural Heritage Commissioned Report No. 078 (ROAME No. F04LA14). This report, or any part of it, should not be reproduced without the permission of Scottish Natural Heritage. This permission will not be withheld unreasonably. The views expressed by the author(s) of this report should not be taken as the views and policies of Scottish Natural Heritage. Scottish Natural Heritage 2005.

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3 COMMISSIONED REPORT Summary NVC survey of Glims Moss & Durkadale SSSI and Loch of Banks SSSI Commissioned Report No. 078 (ROAME No. F04LA14) Contractor: John Crossley Year of publication: 2005 Background This report provides results of an NVC survey of Glims Moss & Durkadale SSSI and Loch of Banks SSSI in Orkney. It provides brief descriptions of the plant communities found in each of the sites and synoptic tables summarising the quadrat data collected. Just less than 200 quadrats were recorded. The other main outputs accompanying this report are NVC maps of the two SSSIs. Main findings l l Glims Moss & Durkadale SSSI is a combination of basin and valley fen including an area of raised bog. Twenty-one NVC communities and sub-communities were identified plus three further types that could not be allocated to a recognised NVC community. Loch of Banks SSSI is described as calcareous basin mire. The area of permanent standing water has reduced in recent times. Twelve NVC communities and sub-communities were identified. A further two types were identified but could not be allocated to a recognised NVC community. For further information on this project contact: Ruth Priestley, Scottish Natural Heritage, Junction Road, Kirkwall KW15 1AW Tel: For further information on the SNH Research & Technical Support Programme contact: The Advisory Services Co-ordination Group, Scottish Natural Heritage, 2 Anderson Place, Edinburgh EH6 5NP. Tel: or ascg@snh.gov.uk

4 Acknowledgements I am grateful to Ruth Priestley, SNH nominated officer for the contract, for the excellent support she has given in responding to requests for information, also to Eleanor Charman of SNH s GIS team for her advice on formatting data for generating maps in LGF, SNH s GIS facility. I am very grateful to Dave Horsfield, of SNH Advisory Services, for his great help when I was struggling to place some vegetation types in the NVC. He examined some of my data and suggested how the stands might relate to existing NVC communities, how they could be placed in the framework of phytosociological associations and alliances, and where to look for more information. This was invaluable, although it must be said that at the end of the day responsibility for any mistakes is entirely mine! Summary This report is part of a National Vegetation Classification (NVC) survey of two SSSIs in Orkney, Glims Moss & Durkadale and Loch of Banks. It provides brief descriptions of the plant communities found and synoptic tables summarising the quadrat data gathered. The other main outputs are 1:10000 and 1:5000 maps of the sites showing all NVC communities and sub-communities, with accompanying data in electronic form for generation of GIS maps. Target notes are also provided. Glims Moss & Durkadale SSSI is a combination of basin and valley fen, including an area of deep peat in the basin that has many of the characters of a raised bog. Peripheral areas consist of dry and wet heath, blanket bog and grassland. 21 NVC communities and sub-communities were recognised, and three intergrades. A further three types were found which could not be allocated to a recognised unit of the NVC. The Loch of Banks may be described as a calcareous basin mire. The area of permanent standing water at this site has apparently been much reduced by drainage in recent times. 12 NVC communities and subcommunities were recognised, and two intergrades. A further two types (one the same as at Glims/ Durkadale) were found which could not be allocated to a recognised unit of the NVC. The unrecognised communities have been compared with those described from other parts of Britain in JNCC and SNH reviews of NVC coverage, and in some cases efforts have been made to place them in the frame of the European phytosociological classification. Just less than 200 quadrats were recorded to support the identification of communities and sub-communities. Records were made of nationally and locally uncommon species found. Details of quadrat references, target notes, polygon data, quadrat data and new NVC community definitions for both the Loch of Banks and Glims Moss and Durkadale are stored on disc at the Kirkwall Office and central SNH Library. To view this data, please contact the Scottish Natural Heritage office in Kirkwall or the SNH Library.

5 Contents Acknowledgements Summary 1 BACKGROUND 1 2 AIMS AND OBJECTIVES 2 3 METHODS Fieldwork Data analysis and NVC fitting Use of the European phytosociological classification Previous surveys 6 4 DESCRIPTION OF SITES AND VEGETATION 7 GLIMS MOSS & DURKADALE 4.1 Introduction General character of the vegetation Uncommon plants NVC communities 9 5 DESCRIPTION OF SITES AND VEGETATION 40 LOCH OF BANKS 5.1 Introduction General character of the vegetation Methodology NVC communities 41 REFERENCES 54 Appendix 1 Target notes for Glims Moss & Durkadale 55 Appendix 2 Target notes for Loch of Banks 56 Quadrat data for each site have been saved as a separate section of electronic files in Microsoft Excel

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7 1 BACKGROUND NVC surveys of the two sites were required in 2004 to enable SNH Area staff to undertake Site Condition Monitoring (SCM) and to confirm the location and extent of fen, marsh & swamp habitats. SCM of fen, marsh & swamp habitats is based on NVC. 1

8 2 AIMS AND OBJECTIVES To conduct National Vegetation Classification surveys of vegetation communities at Loch of Banks SSSI and Glims Moss & Durkadale SSSI. To produce 1:10000 or 1:5000 maps of all vegetation within the SSSI boundaries, showing communities and sub-communities, with target notes and sample quadrat data for each community/sub-community. To collect and record data in a form suitable for digitising, in accordance with standard SNH guidance for NVC mapping projects. To produce a brief accompanying report. 2

9 3 METHODS 3.1 Fieldwork Timing Fieldwork was undertaken at Glims Moss & Durkadale on 11 days between 19 July and 23 Aug, with a further brief visit on 3 Sept to confirm vegetation boundaries from some vantage points (some vegetation types were much more marked by contrasting colours by this time), and at Loch of Banks on 4 days between 24 Aug and 2 Sept Field survey Ground to be covered on a day s visit was first walked to establish the range of habitats present, as far as possible by eye, and these were marked on photocopies of the OS 1:10000 maps of the sites. Areas with mosaic conditions or difficulties of identification were marked out from clearly differentiated adjoining areas, to await closer examination. Copies of 1:10000 aerial photographs of the sites were also taken into the field, and these were very useful for locating the boundaries of the more obvious vegetation types and features, especially areas with a high cover of dwarf shrubs, and small watercourses. At Loch of Banks the extent of standing water was quite different to that shown on the OS map and the aerial photos showing the present extent were invaluable. Sampling of vegetation types was then carried out as recommended in the NCC NVC field manual, by separately sampling at random in stands of vegetation judged by eye to be floristically and structurally homogeneous. At least five samples per vegetation type were taken, where possible, to provide a constancy score of I V (some vegetation types of scarce occurrence were sampled less than five times). Where it was difficult to establish the vegetation type, sampling was continued to achieve a larger data set. Thereafter, free mapping of communities was possible, with occasional sampling to confirm type and register variations. The size of quadrat used was 2 x 2m, except in species-poor swamp and tall herb fen where it was 4 x 4m. These details and other quadrat data are given in the synoptic tables describing individual communities later in this report. Quadrat and target note positions were recorded as a 10 figure (1m) grid reference using a GPS instrument, though the accuracy of this gadget is probably not as good as this and an 8 figure reference would be more realistic. Within each quadrat, all vascular plants, and bryophytes of frequent occurrence (and some less frequent but readily recognisable), were identified* and an estimate of cover value of each made, using the DOMIN scale of cover as shown below: 3

10 DOMIN score % % % % % % % 3 Many individuals 2 Several individuals 1 Few individuals * Nomenclature for vascular plants follows Stace (1997) and for bryophytes Blockeel & Long (1998). 3.2 Data analysis and NVC fitting Quadrat data were entered in tables in Microsoft Excel and matched to community and sub-community using the text and tables published in British Plant Communities (Rodwell, op.cit). Results were compared with scores produced by the MATCH programme, produced by Andrew Malloch of Lancaster University in the edition supplied as part of the MAVIS package (Modular Analysis of Vegetation Information System) by CEH. Results are summarised in synoptic tables in this report. Most groupings corresponded well or reasonably well with an NVC type, but in a number of cases they did not. In these cases the MATCH programme is not particularly useful, in supplying a number of alternative answers, some inappropriate, with low scores. A good deal of thought was given and some advice taken as to how to treat these problematic groupings. The solution has not been the same in all cases. Sometimes the constituent communities of a fine mosaic have been apparent, and in these cases the stands have been characterised as intermediates or transitions. Often it has been sensible to assign them to the best-fitting unit of the NVC, giving reasons for doing so, but in other cases it has seemed more useful to retain them as unique vegetation types, with identifying codes. All but one of these types has been allocated a new name and code. In these cases the method of naming follows the NVC convention of using species strongly preferential for the community followed by a descriptive term for the vegetation type (though the species have been chosen less rigorously as distinctive constants rather than strong preferentials). The code used is a unique one consisting of a first letter for the general kind of vegetation followed by letters standing for the distinctive species. Thus a potential new type of fen meadow or rush pasture with Carex nigra and Calliergonella cuspidata as distinctive constants is a mire community in the NVC and is named Carex nigra-calliergonella cuspidata fen meadow with a code of MCC. One case however is exceptional: this is where a code for a provisional new NVC type has already been suggested in an SNH review of NVC coverage (Cooper and MacKintosh, 1996 see below). The particular difficulties encountered in relation to some individual communities, and reasons for taking different approaches to them, are given in later sections of this report, but it is useful to summarise here the underlying reasons. 4

11 i) Vegetation types known to be poorly represented in the NVC Reviews for JNCC (Rodwell et al. 2000) and SNH (Cooper & MacKintosh, 1996) have drawn attention to new variation and gaps at plant community and sub-community levels in the NVC and briefly described the vegetation concerned. Almost all of the problematic vegetation at the Orkney sites relates to these gaps and some of it is almost certainly referable to some of the new types described in the reviews. Chief among them are: l l l l small-sedge, poor-fen vegetation of flushes and soligenous mires; fen meadow or rush pasture; vegetation dominated by Molinia caerulea inundation grassland where Agrostis stolonifera and Carex nigra figure prominently. Without having seen detailed description or synoptic tables of quadrat data relating to these types as they have been found elsewhere it is not possible to say precisely how similar to them the Orkney vegetation is. ii) Local individualities The extreme north-eastern location of Orkney, the cool oceanic climate (somewhat drier and colder than the west of Scotland), the effect of sea spray deposited in varying amounts over the entire archipelago and the effect on soils and water of the frequent base-richness of the underlying rocks provide an unusual combination of conditions compared to the median for British vegetation types. Some local peculiarities are striking: plant species commonly associated with rather divergent ecological conditions, and different NVC communities, can be found side by side. For instance the boraeo-arctic montane Festuca vivipara and the oceanic and southern-temperate Anagallis tenella may be found together in flushes, while the saltmarsh species Triglochin maritima commonly occurs in inland wetlands. The vegetation is also depauperate. One would expect, and it is the case, that some species common in north Scotland are missing from the islands flora. Others have very localised occurrence. In their absence, other species are able to occupy the gaps they have left. These factors can be expected to cause considerable differences in the composition of local vegetation communities when compared to the descriptions of NVC communities assembled from a wide range of places in Britain, or even Scotland. iii) NVC coverage of Orkney Data from Orkney lowland mires is almost completely absent from that used in compiling the relevant volume of British Plant Communities, (Rodwell 1991), so local variations are not featured in descriptions or NVC tables there. The subsequent JNCC and SNH reviews do not seem to include information from Orkney either. An Illustrated Guide to British Upland Vegetation (Averis et al. 2004) makes some references to Orkney, but they are very brief. 5

12 iv) Limitations of the survey As Cooper and MacKintosh (1996) point out in their review, intensive sampling of local areas, especially of one or two sites, will tend to multiply up any local peculiarities. Thus, for instance an associate species rare or occasional within an NVC community on a regional or national basis may appear as a constant on a table when the samples are only recorded from small areas where that species is locally abundant. It is hoped that any gross problems of this sort have been avoided, but they are to some extent inevitable in survey of a limited area. Note: For both the Loch of Banks, and Glims Moss and Durkadale Excel spreadsheets profiling new communities are stored on disc at the Kirkwall Office and in the central SNH Library. In addition Excel spreadsheets with quadrat references, target notes, polygon data and individual quadrat data are likewise stored on this disc. Requests for this information should be made through the Scottish Natural Heritage office in Kirkwall, Orkney or through the SNH Library Service. 3.3 Use of the European phytosociological classification The above difficulties have been borne in mind in sampling the vegetation and analysing the data. In the end, where a type has not fitted well to a unit of the NVC it has been a question of balancing considerations to decide which of the various approaches to describing it provides a better understanding of the vegetation. In the most problematic cases, it has been useful to follow the approach used in the JNCC review (Rodwell et al. 2000), of attempting to place the type in the frame of the European phytosociological hierarchy, as described in the Phytosociological Conspectus of British Plant Communities in the final volume of British Plant Communities (Rodwell, 2000). Some papers on Irish vegetation have been consulted to take this further. 3.4 Previous surveys NVC survey of much of Glims Moss and Durkadale was conducted by Matthew Tickner for the RSPB, as owners of much of the site (Tickner, 1990). This was part of a wider survey of RSPB Orkney upland reserves. The approach taken was fairly broad-brush and the report contains little discussion of or data on the more problematic communities. Many intermediate communities were mapped. A more detailed examination of other RSPB reserves was undertaken by Prosser and Wallace (1992). Though Loch of Banks was not among these, the nearby Loons and Loch of Isbister reserve, which is in the same wide, flat basin as Loch of Banks and connected to it by a drainage ditch, was included. There are similarities with the vegetation of Loch of Banks, and some with that of Glims Moss and Durkadale. Their report contains analysis of local individualities, detailed description of NVC communities, and discussion of the difficulties of placing some of these in the NVC. 6

13 4 DESCRIPTION OF SITES AND VEGETATION GLIMS MOSS & DURKADALE 4.1 Introduction Glims Moss and Durkadale SSSI has an area of 225.3ha. The bog of Glims Moss shows some essential features of a simple raised bog, composed of a discrete unit of deep peat (said to be up to 8m in depth) formed in a basin and surrounded by a fen and bog pool lagg zone. There are smaller units of deep peat adjacent to the main bog, distributed along the length of the Durkadale valley to the northwest. However neither the main bog nor the smaller units appear to be raised in the centre and there is therefore no slope to the edges. The fen and swamp occupying much of the rest of the site could be described equally well as basin or valley fen. Low hills rise on either side of the broad basin occupied by the peat bog, this basin narrows to a valley to the northwest, and a burn threads the basin and valley. It appears that the entire basin and much of the valley is filled with soft peat, though presumably mixed or overlain with alluvial material in places. The peat can be seen in the sides of the axial burn and the ditches that have been cut down to it. The movement of water through the site is undoubtedly complex, from sources comprising overbank flooding, direct rainfall, the bog peat, flushes on the adjoining hill slopes, and percolation of groundwater, this last being a major cause of complexity in the vegetation types. Percolating and flush water derived from the rock strata appears to be highly or moderately calcareous in many places, although no readings were taken during this survey. Prosser and Wallace (1992), surveying the Loons/Loch of Isbister basin 5km to the west found water ph values from 4.2 to 8.2. There is likely to be some enrichment of run-off and ditch water from agricultural sources, but such influences are likely to be slight in relation to the total volume of water input. Some facts about the history of the site have been gathered from local people. Formerly, peat cutting for domestic use has been carried out on a small scale. There are long abandoned and grown-in peat cuttings at two places on the southeast and southwest edge of Glims Moss bog, and more recent but also abandoned cuttings below Farafield on the northeast side of the site. Deep ditches have been cut at intervals down to the northeast side of the axial burn, to drain low-lying farmland adjacent to the fen basin. Some of these ditches were dug early in the 20th century, and were deepened and extended in the 1960s. Many have almost completely silted up and grown in (and are hazardous), but some have been recently cleaned. There is a linear feature consisting of a low bank and a slight hollow parallel to it, said to be the remains of an old drainage ditch, running for approximately 1km within the eastern edge of the raised bog. It is barely discernible on the ground but is clearly visible on the aerial photo. The remains of two wire fences cross the bog, but apparently these were put up to mark ownership boundaries, and there is no known history of grazing on the main bog. Grazing by cattle is carried out on parts of the site at Durkadale. 7

14 4.2 General character of the vegetation The existence of climatic and other factors particular to the islands, and their effects on the composition of plant communities, has been noted already. One of these effects is that a number of species were recorded with more frequency and abundance across a greater range of the vegetation communities sampled than would be expected. No analysis has been carried out to quantify the prevalence of species in comparison with their presence in NVC community tables, but viewing the data collected in this survey the species that stand out are Carex nigra, C flacca, C pulicaris, Potentilla palustris, Holcus lanatus and Festuca vivipara among mires, fen meadows and wet grasslands, and Empetrum nigrum ssp nigrum among wet heaths, blanket mire and transitional wet, peaty habitats. Overall there is an impression of representation of more basophile or mesotrophic species across a wide range of habitats, a blurring of distinctions between poor and rich fens, and unusually rich Molinia grasslands and fen meadows or rush pastures. Similar observations can be made about species with unexpectedly low occurrence. Completely absent from the stands surveyed were Festuca ovina, Juncus acutiflorus, Lotus uliginosus, Myrica gale and Sphagnum squarrosum. 4.3 Uncommon plants The nationally uncommon Carex diandra was recorded from a number of places and was locally abundant at one. Other plants recorded that are uncommon in Orkney were Carex paniculata, C limosa, Luzula pilosa and Eleogiton fluitans. A large sedge present in one dense stand at Durkadale is said to have been reliably identified as C riparia x rostrata (E. R. Bullard, pers.comm.) 8

15 4.4 NVC communities Woodlands and scrub W3 Salix pentandra Carex rostrata woodland Salix scrub occurs in patches throughout the swampier parts of the site. Often it is very low, merely a component of a field layer of grasses and sedges, or about 0.5m high among Phragmites. Many bushes though are 2 3m in height, forming complete canopies many square metres in extent. S phylicifolia is by far the commonest species, and the only one in the samples. S aurita and S cinerea (ssp not determined) are present, but relatively rare. The fit to W3 Salix pentandra-carex rostrata woodland is good, but for the presence of S phylicifolia as sole dominant in place of S pentandra and other Salix species. The vegetation may be seen as a local variant. Salix phylicifolia V 9 10 Filipendula ulmaria V 2 4 Cardamine pratensis IV 1 3 Equisetum palustre III 1 3 Lophocolea bidentata II 3 Calliergonella cuspidata II 2 4 Epilobium palustre II 2 3 Poa trivialis II 2 3 Galium palustre II 1 3 Caltha palustris II 1 2 Plagiomnium undulatum II 1 2 Agrostis stolonifera II 1 2 Holcus lanatus II 1 Eurynchium praelongum I 2 Carex rostrata I 2 Rhytiadelphus squarrosus I 2 Angelica sylvestris I 1 Brachythecium rivulare I 1 Bryum pseudotriquetrum I 1 Carex nigra I 1 Cerastium fontanum I 1 Deschampsia cespitosa I 1 Eriophorum angustifolium I 1 Juncus articulatus I 1 Mentha aquatica I 1 Molinia caerulea I 1 Ranunculus flammula I 1 Rumex acetosa I 1 Succisa pratensis I 1 4 x 4m Number of samples 5 Number of species per sample 10.4 (4 14) 9

16 4.4.2 Mires and heaths M5 Carex rostrata Sphagnum squarrosum mire With description of this community one arrives at the vexing question of how to characterise much of the large area of fen and fen meadow or rush pasture on soft peat at this site. Much of it is intermediate between the poor, calcifuge fen vegetation characterised by the M5 community or the M6 Carex echinata- Sphagnum mire on firmer peat (present but uncommon) and the richer, calcicolous flushes, fens and swamps (present in variety across the site). However, a little of it is clearly referable to the M5 community, and this is characterised in the sample data summarised in the synoptic table. The nominate species Sphagnum squarrosum and Carex rostrata are absent from the data, but there is a good representation of poor-fen herbs and bryophytes including sphagna. Carex nigra may be seen as a replacement for C rostrata and the absence of S squarrosum is a local singularity. All stands, including those sampled, were small and in mosaic with other communities, hence the presence at low frequency in the data of bryophytes characteristic of rich fens (Aneura pinguis, Dreplanocladus revolvens, Campylium stellatum): base-rich flushing and percolation is never far away at this site. This vegetation occupies soligenous zones and hollows in long-disused and grown-in peat cuttings on the southwest side of Glims bog. Potentilla palustris V 5 9 Carex nigra V 2 7 Aulacomnium palustre IV 3 4 Menyanthes trifoliata IV 2 7 Sphagnum fallax* III 2 7 *Formerly S recurvum Calliergonella cuspidata III 2-4 Sphagnum palustre III 1 7 Potamogeton polygonifolius II 3 5 Galium palustre II 2 3 Succisa pratensis II 2 3 Ranunculus flammula II 1 4 Aneura pinguis II 1 3 Carex echinata II 1 2 Sphagnum subnitens II 1 Chiloscyphus polyanthos I 4 Dreplanocladus revolvens I 4 Juncus bulbosus I 4 Sphagnum denticulatum* I 4 *Formerly S auriculatum var auriculatum Agrostis canina I 2 Erica tetralix I 2 Molinia caerulea I 2 Campylium stellatum I 1 Cardamine pratensis I 1 Epilobium palustre I 1 Holcus lanatus I 1 Juncus effusus I 1 2 x 2 m Number of samples 5 Number of species per sample 10.6 (8 15) 10

17 MCP Carex nigra-potentilla palustris mire (potential new NVC unit) This vegetation is not referable to a recognised unit of the NVC. With its constants of Carex echinata, Agrostis canina and Potentilla erecta it bears some similarities to the M6 Carex echinata-sphagnum recurvum/auriculatum mire a poor fen community of small sedges or rushes dominating over a carpet of base-intolerant sphagna, on firm peat or peaty gleys. It occurs in a habitat more suited to the M5 community already described, of fairly soft peat in soligenous zones around the Glims bog, and has the M5 constants of Potentilla palustris, Eriophorum angustifolium and Carex nigra as well as a range of mesotrophic herbs associated with M5 or one of the rich-fen communities. However, a cover of bryophytes preferential for either of these communities is lacking. This vegetation occurs at Glims Moss over no great area but with some consistency in two widely separated places. With greater knowledge of the Orkney fen vegetation it is quite possible that it could in future be identified as an intermediate between local variants of recognised NVC communities, or between those and provisional new units of the NVC. However it could well be referable to a provisional new community of small-sedge, poor-fen. From the phytosociological perspective on small-sedge fens (poor and rich), as applied in Ireland by O Criordain & Doyle (1994) the quadrats recorded have the class character species of the Scheuchzerio- Caricetea nigrae including: Carex nigra (V), Potentilla palustris (V), Epilobium palustre (III), Galium palustre (III), Pedicularis palustris (I) and Ranunculus flammula (I). The nearest association in O Criodain & Doyle appears to be Carici curtae-agrostidetum caninae. The stands have high constancy of two of the character species: Agrostis canina (V) and Carex echinata (V), while the third C. curta (II) is lower. Also, other species found, including C nigra, Eriophorum angustifolium, Holcus lanatus, Molinia caerulea and Potentilla erecta seem to correspond to make a reasonably good fit. Rodwell (2000) does not assign any of the NVC smallsedge fens to this association. The nearest group in the NVC in Rodwell (M5, M6, M7, M8) is assigned to the closely related alliance Caricion nigrae. MCP Carex nigra-potentilla palustris mire (potential new NVC unit) Potentilla palustris V 3 7 Juncus effusus II 1 2 Carex nigra V 2 7 Menyanthes trifoliata II 1 2 Agrostis canina V 2 5 Sphagnum fallax II 1 2 Holcus lanatus V 1 4 Angelica sylvestris II 1 Carex echinata V 1 4 Lychnis flos-cuculi II 1 Rumex acetosa V 1 3 Stellaria uliginosa II 1 Rhytiadelphus squarrosus IV 1 8 Equisetum palustre I 4 Eriophorum angustifolium IV 1 4 Agrostis stolonifera I 3 Potentilla erecta IV 1 4 Hypnum jutlandicum I 3 Filipendula ulmaria IV 1 3 Scleropodium purum I 3 Viola palustris III 2 4 Sphagnum palustre I 3 Carex panicea III 2 3 Lophocolea bidentata I 2 Anthoxanthum odoratum III 1 4 Pleurozium schreberi I 2 Calliergonella cuspidata III 1 4 Caltha palustris I 1 Succisa pratensis III 1 4 Calluna vulgaris I 1 11

18 Deschampsia flexuosa III 1 3 Cirsium palustre I 1 Epilobium palustre III 1 3 Erica tetralix I 1 Galium palustre III 1 3 Eriophorum vaginatum I 1 Luzula multiflora III 1 3 Festuca vivipara I 1 Molinia caerulea III 1 3 Pedicularis palustris I 1 Hylocomium splendens II 3 5 Ranunculus flammula I 1 Sphagnum palustre II 3 Rhytiadelphus loreus I 1 Carex pulicaris II 2 3 Salix phylicifolia I 1 Aulacomnium palustre II 1 2 Sphagnum subnitens I 1 Carex curta II x 2m Number of samples 5 Number of species per sample 23 (16 27) 12

19 M15a Scirpus cespitosus-erica tetralix/m5 Carex rostrata-sphagnum squarrosum mire wet heath transition Some soligenous areas on the south and east sides of the Glims bog are occupied by vegetation intermediate between wet heath and small-sedge poor fen or even rich fen. The vegetation is variable, sometimes appearing quite close to M5, with a high cover of moderately base-tolerant sphagna and swamp inhabitants like Potentilla palustris on softer peat (though as in the M5 community described above the nominate species Carex rostrata and Sphagnum squarrosum are absent). There is some M10 flushing to further complicate the situation. The dwarf shrubs are at high frequency in the table, and are obvious as small clumps and strands among grasses, sedges and bryophytes but do not dominate the vegetation structurally. These areas have been mapped as M15a/M5. Carex nigra V 3 7 Sphagnum denticulatum I 4 Potentilla palustris V 2 7 Odontoschisma sphagni I 3 Eriophorum angustifolium V 2 5 Sphagnum inundatum* I 3 Carex echinata V 1 3 Hylocomium splendens I 2 Succisa pratensis IV 2 4 Polytrichum commune I 2 Sphagnum fallax IV 1 8 Rhytiadelphus loreus I 2 Sphagnum palustre IV 1 6 Juncus effusus I 1 5 Agrostis canina IV 1 5 Deschampsia flexuosa I 1 4 Calluna vulgaris IV 1 4 Rhytiadelphus squarrosus I 1 4 Erica tetralix IV 1 4 Sphagnum capillifolium I 1 3 Festuca vivipara IV 1 4 Holcus lanatus I 1 2 Potentilla erecta IV 1 4 Eriophorum vaginatum I 1 Molinia caerulea III 1 6 Anthoxanthum odoratum I 1 Carex panicea III 1 3 Calliergonella cuspidata I 1 Menyanthes trifoliata II 4 6 Campylopus flexuosus I 1 Empetrum nigrum nigrum II 3 5 Caltha palustris I 1 Aulacomnium palustre II 3 4 Carex binervis I 1 Narthecium ossifragum II 1 8 Drosera rotundifolia I 1 Sphagnum papillosum II 1 3 Luzula multiflora I 1 Viola palustris II 1 3 Pedicularis palustris I 1 Sphagnum subnitens II 1 2 Polygala serpyllifolium I 1 Carex pulicularis II 1 2 Sphagnum fimbriatum I 1 Hypnum jutlandicum II x 2m Number of samples 10 Number of species per sample 16 (10 24) * Formerly S auriculatum var inundatum 13

20 M6 Carex echinata-sphagnum recurvum/auriculatum mire M6c Juncus effusus sub-community Little M6 vegetation of any sub-community was found on the site. This M6c sub-community, characterised by abundant Polytrichum commune, together with sphagna, overlain by a field layer of poor fen herbs with Juncus effusus, was found in a few small patches on the fringes of blanket bog running into grazed rush pasture at the northern end of Durkadale. Just one quadrat was recorded. Polytrichum commune 8 Juncus effusus 5 Calluna vulgaris 3 Eriophorum angustifolium 3 Succisa pratensis 3 Juncus conglomeratus 3 Potentilla palustris 2 Agrostis canina 2 Anthoxanthum odoratum 2 Holcus lanatus 2 Sphagnum fallax 2 Sphagnum subnitens 2 Luzula multiflora 1 Potentilla erecta 1 Rumex acetosa 1 Sphagnum palustre 1 2 x 2m Number of samples 1 Number of species per sample 16 14

21 M9 Carex rostrata-calliergon cuspidatum/giganteum mire M9b Carex diandra-calliergon giganteum community This vegetation is quite widespread on the eastern side of the site. It is rather varied, and often intermediate between the two sub-communities. The constancy of Epilobium palustre, the frequent presence of Carex giganteum, Caltha palustris and Cardamine pratensis, and the representation of other species at lower frequencies indicate the M9b sub-community. It grades into the MCC Carex nigra Calliergonella cuspidata fen meadow (potential new community). As part of this community, bryophyte lawns with abundant Calliergon giganteum and some Sagina nodosa, accompanied by Carex rostrata and/or Carex limosa occur in several places. The high frequency in the synoptic table of grasses including Festuca rubra and Holcus lanatus is partly accounted for by the inclusion of quadrats from a large area referable to this community at the northeast of the Durkadale valley, on a slope copiously irrigated by a line of springs. The land is so wet as to be swampy in places, but in places a drier crust has formed over the soft silt below, allowing a grassy vegetation to develop. Carex diandra is common here, though not frequent in the synoptic table, also Carex paniculata in large tussocks near the top of the slope. M9 Carex rostrata-calliergon cuspidatum/giganteum mire M9b Carex diandra-calliergon giganteum community Menyanthes trifoliata V 1 8 Plagiomnium undulatum I 1 7 Calliergonella cuspidata V 2 7 Rhytiadelphus squarrosus I 1 7 Carex rostrata V 1 6 Carex diandra I 1 4 Equisetum fluviatile IV 1 7 Carex paniculata I 1 4 Festuca rubra IV 1 5 Carex dioica I 2 Holcus lanatus IV 1 5 Hydrocotyle vulgaris I 1 4 Epilobium palustre IV 1 4 Hylocomium splendens I 1 4 Equisetum palustre III 1 9 Scorpidium scorpioides I 1 3 Caltha palustris III 1 5 Juncus bulbosus I 3 Cardamine pratensis III 1 3 Aneura pinguis I 1 2 Lophocolea bidentata III 2 4 Carex panicea I 1 2 Agrostis stolonifera III 1 4 Carex hostiana I 3 Calliergon giganteum III 1 4 Dactylorhiza sp I 1 2 Campylium stellatum III 1 4 Poa humilis I 1 2 Carex flacca III 1 4 Succisa pratensis I 1 2 Dreplanocladus revolvens II 4 7 Philonotis fontana I 1 Carex viridula ssp bracchyryncha II 3 6 Parnassia palustris I 4 Potentilla palustris II 3 4 Rhytiadelphus triquetrus I 4 Carex nigra II 2 7 Sphagnum subnitens I 4 Juncus articulatus II 2 4 Chiloscyphus polyanthos I 3 Lychnis flos-cuculi II 1 6 Rhizomnium punctatum I 3 Plagiomnium ellipticum II 1 5 Anthoxanthum odoratum I 2 15

22 Angelica sylvestris II 1 4 Bryum pseudotriquetrum I 2 Galium palustre II 1 3 Agrostis canina I 1 Rumex acetosa II 1 3 Carex pulicaris I 1 Sagina nodosa II 1 3 Deschampsia cespitosa I 1 Stellaria uliginosa II 1 3 Juncus effusus I 1 Cerastium fontanum II 1 2 Mentha aquatica I 1 Eriophorum angustifolium II 1 2 Molinia caerulea I 1 Carex limosa I 3 8 Phragmites australis I 1 Agrostis capillaris I 2 4 Pellia endiviifolia I 1 Poa trivialis I 2 4 Potentilla erecta I 1 Aulacomnium palustre I 2 3 Ranunculus flammula I 1 Brachythecium rivulare I 2 3 Ranunculus repens I 1 Brachythecium rutabulum I 2 3 Scleropodium purum I 1 Palustriella commutatum I 3 4 Thuidium tamariscinum I 1 Salix phylicifolia I 3 4 Viola palustris I 1 2 x 2m Number of samples 13 Number of species per sample (14 28) 16

23 M10 Carex dioica-pinguicula vulgaris mire M10a Carex demissa-juncus bulbosus/kochii sub-community This vegetation occurs in hillside flushes but also in flushed areas on peat and among Molinia-dominated grasslands, where it may be more extensive on a soft substrate. It is therefore somewhat varied, and there can be doubts over the classification of some stands which may be transitional to M9 mire. However, the short sward with a variety of small sedges either constant or frequent, together with the characteristic bryophytes and scattering of herbs is characteristic. The M10ai sub-community and variant is quite a good fit for this vegetation, though there are anomalies. In view of the somewhat varied habitats in which it has been sampled this is not surprising. One anomaly is the constancy of Carex flacca, a differential for the M10b sub-community. As noted in the introductory section of this report, C flacca appears at unexpectedly high frequency in a number of mire communities in Orkney, and in other respects the M10b variants are not as good a fit as M10ai. Another is the frequency of Schoenus nigricans, differential for the M10aiii variant; however the other differential species for the M10aiii variant, Drosera anglica, Blindia acuta, Pinguicula lusitanica, Myrica gale and others at lower frequency are absent. Also, the Schoenus here is often accompanied by Anagallis tenella, a species not associated with M10 at all. Another peculiarity at Glims/Durkadale is stands with Phragmites australis. These characteristics suggest the presence of another community altogether most likely a northern analogue of M13 Schoenus nigricans- Juncus subnodulosus mire, as well as M10, and communities transitional between the two. The amount of sampling carried out at this site cannot establish this, but the argument is taken up later in this report, in relation to the Schoenus flushes at Loch of Banks. These flushes and mires have been mapped as M10a. M10 Carex dioica-pinguicula vulgaris mire M10a Carex demissa-juncus bulbosus/kochii sub-community Dreplanocladus revolvens V 2 5 Potentilla erecta II 1 2 Juncus articulatus V 2 3 Equisetum fluviatile II 1 Molinia caerulea V 1 6 Euphrasia agg. II 1 Carex panicea V 1 4 Palustriella commutatum I 2 4 Eriophorum angustifolium V 1 4 Pedicularis palustris I 1 4 Campylium stellatum IV 3 4 Cratoneuron filinicum I 3 Selaginella selaginoides IV 2 3 Equisetum palustre I 2 3 Carex flacca IV 1 4 Ranunculus flammula I 1 3 Carex pulicaris IV 1 4 Agrostis canina I 2 Carex dioica IV 1 3 Mentha aquatica I 1 2 Succisa pratensis IV 1 2 Erica tetralix I 1 2 Hydrocotyle vulgaris III 1 8 Narthecium ossifragum I 1 2 Calliergonella cuspidata III 3 7 Angelica sylvestris I 1 Menyanthes trifoliata III 1 6 Lychnis flos-cuculi I 1 Anagallis tenella III 3 5 Prunella vulgaris I 1 17

24 Carex viridula ssp bracchyryncha III 2 4 Senecio aquaticus I 1 Aneura pinguis III 2 3 Aulacomnium palustre I 4 Scorpidium scorpioides III 2 5 Carex viridula ssp oedocarpa I 3 Carex hostiana III 1 5 Chiloscyphus polyanthos I 3 Carex nigra III 1 4 Epilobium palustre I 3 Filipendula ulmaria III 1 4 Eleocharis quinqueflora I 3 Cardamine pratensis III 1 3 Plagiothecium ellipticum I 3 Juncus bulbosus III 1 3 Potamogeton polygonifolius I 3 Pinguicula vulgaris III 1 3 Sphagnum capillifolium I 3 Sagina nodosa III 1 3 Thalictrum alpinum I 3 Agrostis stolonifera III 1 2 Carex rostrata I 2 Dactylorhiza sp III 1 2 Sphagnum denticulatum I 2 Schoenus nigricans II 4 8 Potentilla palustris I 2 Calliergon giganteum II 3 5 Carex diandra I 1 Festuca rubra II 2 3 Cirsium palustre I 1 Linum catharticum II 2 3 Empetrum nigrum nigrum I 1 Triglochin maritimum II 2 3 Leontodon autumnalis I 1 Calluna vulgaris II 1 3 Luzula multiflora I 1 Anthoxanthum odoratum II 1 3 Parnassia palustris I 1 Holcus lanatus II 1 3 Poa humilis I 1 Bryum pseudotriquetrum II 1 2 Rumex acetosa I 1 Caltha palustris II 1 2 Stellaria uliginosa I 1 Festuca vivipara II 1 2 Triglochin palustris I 1 2 x 2m Number of samples 8 Number of species per sample 30 (20-36) 18

25 M15 Scirpus cespitosus-erica tetralix wet heath Wet heath M15 vegetation at this site mainly falls into the M15c sub-community, and some into the M15b sub-community (see following sections). Other bits, scattered in small areas around the fringes of the site are fragmentary or transitional, and difficult to place in a sub-community. Where there is some water movement, especially where accompanied by past grazing, dwarf shrubs are scarce among dominant Molinia, at others there are transitions to M19 blanket mire. As usual, some base-rich flushing shows in the presence of Carex panicea and some poor fen herbs, indicating that these stands may be referable to the M15a Carex panicea sub-community. Some of these stands, a small proportion of the total area of wet heath, have been assigned to no sub-community. The frequency of Empetrum nigrum ssp. nigrum in the stands is a local individuality. M15b Typical sub-community Calluna vulgaris V 2 9 Luzula multiflora II 1 2 Erica tetralix V 1 6 Eriophorum vaginatum II 1 2 Potentilla erecta V 1 3 Deschampsia flexuosa II 1 Empetrum nigrum nigrum IV 3 5 Anthoxanthum odoratum I 4 Trichophorum cespitosum IV 1 5 Hylocomium splendens I 4 Hypnum jutlandicum III 3 6 Rhytiadelphus squarrosus I 4 Narthecium ossifragum III 3 5 Succisa pratensis I 4 Eriophorum angustifolium III 3 4 Festuca vivipara I 3 Molinia caerulea III 1 5 Juncus effusus I 3 Sphagnum palustre III 1 4 Racomitrium lanuginosum I 3 Agrostis canina III 2 Rhytiadelphus loreus I 3 Sphagnum subnitens II 1 2 Carex echinata I 2 Sphagnum fallax II 3 Carex nigra I 2 Sphagnum capillifolium II 4 Sphagnum papillosum I 2 Cladonia spp II 1 4 Dicranum scoparium I 1 Carex panicea II 3 Juncus squarrosus I 1 Plagiothecium undulatum II 2 Sphagnum tenellum I 1 2 x 2m Number of samples 5 Number of species per sample 14.6 (12 20) 19

26 M15 Scirpus cespitosus-erica tetralix wet heath M15c Cladonia sub-community This is the wet heath vegetation, with higher frequencies for Cladonia species, Racomitrium lanuginosum and Erica cinerea, covering much of the thin peat lying on a gentle slope running down to the Glims bog at the south of the site. There is some difficulty of classification with some heath developed on slightly higher ground among wet heath, bog and flush, where the vegetation appears close to H10 Calluna vulgaris-erica cinerea dry heath, but for the presence of scattered Sphagnae and Eriophorum angustifolium. These have almost always been regarded as M15c, but the balance has sometimes tipped in favour of H10 Calluna vulgaris- Erica cinerea heath. Calluna vulgaris V 5 7 Hypnum cupressiforme s.l. V 4 7 Erica tetralix V 3 5 Cladonia spp V 2 6 Empetrum nigrum nigrum V 2 5 Eriophorum angustifolium V 1 3 Potentilla erecta V 1 3 Trichophorum cespitosum IV 2 6 Racomitrium lanuginosum III 3 7 Sphagnum capillifolium III 4 Erica cinerea III 3 5 Carex panicea III 2 3 Narthecium ossifragum III 1 4 Sphagnum fallax III 1 4 Molinia caerulea III 1 3 Sphagnum tenellum III 1 3 Agrostis canina III 2 Plagiothecium undulatum III 1 2 Dicranum scoparium III 1 Pedicularis sylvatica III 1 Rhytiadelphus loreus II 2 4 Juncus squarrosus II 2 3 Carex nigra II 2 Festuca vivipara II 2 Eriophorum vaginatum I 4 Campylopus flexuosus I 2 Diplophyllum albicans I 2 Pleurozium schreberi I 2 Aulacomnium palustre I 1 Deschampsia flexuosa I 1 Listera cordata I 1 Polygala serpyllifolia I 1 Sphagnum palustre I 1 Sphagnum subnitens I 1 Succisa pratensis I 1 2 x 2m Number of samples 5 Number of species per sample 18.6 (14 23) 20

27 MCC Carex nigra Calliergonella cuspidata fen meadow (potential new NVC unit) Vegetation referable to this potential new community covers a significant part of the site, on soft peat situated to the northeast of the Glims bog and to the north along the Durkadale valley. It forms grassy but sedge-rich areas between small units of M19 blanket mire, M27 Filipendula-Angelica mire and Phragmites-dominated communities. Smaller areas of rich fen and flush occur among it. It is a consistent vegetation, 20 30cm in height, almost everywhere ungrazed and tussocky. This vegetation cannot be fitted to a recognised unit of the NVC. It is clearly referable to the class Molino-Arrhenatheretea, order Molinietalia caeruleae, and probably to the Junco conglomerati-molinion alliance (comprising only M24 and M25 in the NVC). However it is not very close to M24 or M25. There are similarities to other alliances in that order, and affinities also with the Caricion davallianae alliance (small-sedge, rich fen vegetation) in the class Scheuchzerio-Caricetae nigrae. Character species for the Molinietalia represented include Equisetum palustre, Filipendula ulmaria, Lychnis flos-cuculi, Angelica sylvestris, Cirsium palustre and Senecio aquaticus. However Juncus articulatus and J effusus are present only at low frequency in these stands. They seem closest to the Junco-Molinion despite only one character species, Succisa pratensis, being constant. However there is a good representation of differential species for the alliance: Carex nigra, C panicea, C pulicaris, Molinia caerulea. Rodwell (2000) refers to vegetation similar to M24 Molinia caerulea-cirsium dissectum fen meadow beyond its geographical limits. This may be similar to the Glims/Durkadale stands. The Orkney stands are not grazed, which could account for some differences. It is possible that this vegetation should be assigned to the M26 Molinia caerulea Crepis paludosa mire, probably the M26b Festuca rubra sub-community. Although only described from England in Rodwell (1991), Cooper and MacKintosh (1996) remark that a grassy type has been correctly identified from several places in Scotland, including the Uists. However, as they also remark, to identify M26 one is really relying on the high frequency of a few conspicuous species such as Crepis paludosa and Trollius europaeus, together with the variety of sedges, grasses and herbs. These conspicuous species are absent from the Orkney stands. Prosser and Wallace (1992) regarded very similar vegetation they found at The Loons as a form of M23 Juncus effusus/acutiflorus-galium palustre rush-pasture, M23a Juncus acutiflorus sub-community, though it lacks any bulky Juncus species and most of the other constants. This vegetation, in a thin and modified form, is also found under a great part of the Phragmites-dominated vegetation at Durkadale. 21

28 MCC Carex nigra Calliergonella cuspidata fen meadow (potential new NVC unit) Carex nigra IV 3 8 Cirsium palustre II 1 Equisetum palustre IV 2 8 Potentilla erecta II 1 Calliergonella cuspidata IV 2 6 Juncus articulatus I 3 4 Anthoxanthum odoratum IV 2 5 Menyanthes trifoliata I 2 7 Plagiomnium undulatum IV 1 3 Potentilla palustris I 2 3 Festuca rubra III 2 5 Deschampsia cespitosa I 3 Molinia caerulea III 2 5 Scleropodium purum I 3 Agrostis canina III 2 4 Senecio aquaticus I 2 Filipendula ulmaria III 1 6 Stellaria uliginosa I 2 Carex panicea III 1 6 Brachythecium rivulare I 1 4 Rhytiadelphus squarrosus III 1 5 Mentha aquatica I 1 2 Agrostis stolonifera III 1 4 Salix phylicifolia I 4 Angelica sylvestris III 1 4 Salix repens I 4 Ranunculus flammula III 1 4 Triglochin palustris I 3 Caltha palustris III 1 3 Cardamine pratensis I 2 Equisetum fluviatile III 1 3 Juncus effusus I 2 Lophocolea bidentata III 1 3 Lathyrus pratensis I 2 Lychnis flos-cuculi III 1 3 Arrhenatherum elatius I 1 Rumex acetosa III 1 3 Dactylorhiza sp I 1 Succisa pratensis III 1 3 Eurynchium praelongum I 1 Carex flacca III 1 2 Juncus bufonius I 1 Galium palustre III 1 2 Prunella vulgaris I 1 Epilobium palustre II 2 4 Ranunculus acris I 1 Eriophorum angustifolium II 2 3 Thuidium tamariscinum I 1 Poa humilis II 1 4 Trifolium repens I 1 Carex pulicaris II 1 3 Triglochin maritimum I 1 Carex rostrata II 1 3 Viccia cracca I 1 Brachythecium rutabulum II x 2m Number of samples 8 Number of species per sample 22 (16 33) 22

29 M18 Erica tetralix-sphagnum papillosum raised and blanket mire, M18a Sphagnum magellanicum-andromeda polifolia sub-community Almost all the vegetation of Glims bog can be placed in the M18b and M19a mire communities (see subsequent sections), but the vegetation of an area of about 1ha conforms well to the M18b sub community description. Sphagna including S magellanicum provide much of the ground cover, and Drosera rotundifolia is very common. Just one quadrat was recorded. Calluna vulgaris 5 Sphagnum papillosum 6 Sphagnum capillifolium 6 Empetrum nigrum nigrum 5 Eriophorum angustifolium 4 Sphagnum magellanicum 4 Cladonia spp 3 Erica tetralix 3 Hypnum jutlandicum 3 Narthecium ossifragum 3 Odontoschisma sphagni 3 Drosera rotundifolia 2 Pleurozium schreberi 2 Sphagnum tenellum 2 Number of samples 1 2 x 2m Number of species per sample 15 23

30 M18 Erica tetralix-sphagnum papillosum raised and blanket mire, M18b Empetrum nigrum nigrum-cladonia sub-community Much of the Glims bog has a drier surface than that which supports the M18a vegetation, and it can be placed in the M18b sub-community, which is similar in appearance to the M15c wet heath Cladonia sub-community on shallow peat nearby. The vegetation of smaller units of deep peat raised above surrounding fen in the Durkadale valley is usually closer to M19a, but some is intermediate within 18b: these areas have been mapped as M19a. Just three quadrats were recorded. Calluna vulgaris III 6 7 Cladonia spp III 3 7 Empetrum nigrum nigrum III 1 4 Eriophorum vaginatum III 1 4 Hypnum jutlandicum III 1 4 Sphagnum capillifolium III 5 7 Trichophorum cespitosum III 2 7 Sphagnum papillosum II 4 5 Eriophorum angustifolium II 3 4 Drosera rotundifolia II 2 4 Erica tetralix II 2 Racomitrium lanuginosum II 1 4 Molinia caerulea I 2 Aulacomnium palustre I 1 Potentilla erecta I 1 2 x 2m Number of samples 3 Number of species per sample 11.3 (11 12) 24

31 M19a Calluna vulgaris-eriophorum vaginatum blanket mire, M19a Erica tetralix sub-community This mire vegetation was sampled at scattered locations across the site, and is the commonest community on deep peats, mainly on the gentler slopes of flanking hills and on the southern half of the main bog, less frequently on other parts of the basin and valley. Calluna vulgaris V 6 8 Eriophorum vaginatum V 4 8 Empetrum nigrum nigrum V 2 5 Hypnum jutlandicum V 1 8 Erica tetralix V 1 4 Sphagnum capillifolium IV 3 6 Cladonia spp IV 1 4 Rhytiadelphus loreus IV 1 4 Trichophorum cespitosum III 1 3 Dicranum scoparium III 1 2 Pleurozium schreberi II 3 4 Aulacomnium palustre II 2 4 Sphagnum papillosum II 2 3 Sphagnum subnitens II 2 3 Racomitrium lanuginosum II 1 3 Hylocomium splendens II 1 3 Eriophorum angustifolium II 1 Sphagnum fallax I 5 Carex nigra I 4 Odontoschisma sphagni I 3 Plagiothecium undulatum I 3 Mylia taylorii I 2 Sphagnum palustre I 2 Sphagnum tenellum I 2 Drosera rotundifolia I 1 Juncus squarrosus I 1 Mnium hornum I 1 Narthecium ossifragum I 1 Polytrichum commune I 1 Vaccinium myrtillus I 1 2 x 2m Number of samples 6 Number of species per sample 12.5 (10 16) 25