Introduction: climatic and soil property factors that
Introduction: There are many different classification systems within the UK the first notable one being Tansley (1939) who used dominant tree species to classify woodlands, however it is not always easy to determine the dominant species in mixed woodlands and much of the UK was missing.
This was later improved by Peterken (1981 and 1993) who used the basis of Tansleys’ system, but concentrated more on the management and stand mixes, coming up with 89 ‘semi-natural ancient woodland’ stand types and sub- types (Peterken 1993).This was replaced by National Vegetation Classification (NVC) in 1991 which rather than just looking at the main stands incorporates all the woodland layers classifying them into communities. The NVC was commissioned by the Nature Conservancy Council in 1975 and divides woodland and scrub into 73 communities and sub-communities (Hall et al 2001). This system was developed to try and make classifications in the UK similar to those being used in Europe as well as to update the Tansley classification system.The NCV is more in-depth than both Tansley and Peterkins classifications as it covers the whole of the UK systematically (Rodwell 1991). The forestry commission have also come up with a classification system, this is mainly targeted at foresters, using climatic and soil property factors that influence tree growth to determine favourable woodland/ tree types for individual sites (Pyatt et al 2001).
In 1992 the United Nations conference’ Earth Summit’ met in Rio Janeiro and came up with Agenda 21 on the environment and sustainable development, climate change and biological diversity. A result of this was the European Union Habitats and Species Directive and the UK Biodiversity Action Plan, these require that habitats and species which are threatened or likely to become threatened are protected and preserved. Habitats that are listed in Annex 1 of the Habitats and Species Directive have to be classified in all member states.The habitats listed in Annex 1 are rather broad as they are for all the EU countries, there is an interpretation manual which tries to help determine what is required for each habitat classification however the descriptions are in many instances very misleading (Hall & Kirby 1998; Rodwell & Dring 2001).
The UK has classified its primary woodland types and also those which are important to the UK though may not fully be classified as one of the Annex 1 forest Habitats.There have been efforts to make comparisons with the other classification systems for woodland in the UK. I hope to briefly cover the methods used for the Peterken, NVC, Ecological Site Classification and the Habitats Directive and there usefulness for conservation.
Classifications: Peterken Stand Types: Peterken 1993 Stand Types: These are first split into 12 groups, some of which may be identified by one tree species, others by more than one.Groups 7-11 are classed using five species which rarely occur together and have well-defined geological ranges. The mixed deciduous groups (1-6 and 12) are split successively with the presence of species present in the woodland type increasing (see Table 1). These groups where then split into stand types depending on the soil, drainage, topography and geology as well as the correlation of corresponding dominant, field layer species associated with each.
Table 1: Peterken Main Stand Types, above the line shows the groups with there associated dominant species opposite, under the line shows the mixed woodlands and the species found within them which accumulate as you go down the list. (Adapted from Peterken 2003). GroupStand typeindicator species Group 7AlderwoodsAlnus glutinosa Group 8BeechwoodsFagus sylvatica Group 9Hornbeam woodsCarpinus betulus Group 10Suckering elm woodsUlmus carpinifolia, Ulmus procera Group 11PinewoodsPinus sylvestris Group 1Ash-wych elm woodsUlmus glabra Group 4Ash-limewoodsTilia cordata, Ulmus glabraGroup 5Acid oak-limewoods Group 2Ash-maple woodsAcer campestre, Tilia cordata, Ulmus glabra Group 3Hazel-ash woodsFraxinus excelsior, Acer campestre, Tilia cordata, Ulmus glabra Group 6Birch-oakwoodsQuercus petraea, Quercus robur, Fraxinus excelsior, Acer campestre, Tilia cordata, Ulmus glabra Group 12BirchwoodsBetula pendula, Betula pubescens, Quercus petraea, Quercus robur, Fraxinus excelsior, Acer campestre, Tilia cordata, Ulmus glabraThe main features used for assessing a given semi –natural coppiced wood are mainly tree species and floristic tables as well as ecological factors such as soil type, pH, drainage and geographic area. He used 30 x 30 m plots and uses a modified Domin scale to include single large plants, small plants, saplings, seedlings, Dead plants and those just outside the sample as well as normal percentage cover.
Only 450 samples where used out of 700 and these where neither randomly nor evenly distributed.This classification could be used with just a few species of tree recoded with the soil pH and type and the over geology known. This classification can be used for identifying ancient woodland stands relatively quickly; however localised variations in stand types may be missed due to the incompleteness of the data used. National Vegetation Classification: The National Vegetation Classification has preceded the Peterken ‘Stand Type’ commissioned by Joint Nature Council Committee. It covers the whole of the UK with Volume 1 being Woodland and Scrub communities.This volume has a key which may be used when trying to identify a woodland type.
It is split into 58 sub-communities of which 34 can be classed as ancient woodland (Rodwell 1991; Rackham 2003). The woodland NVC used 2,648 samples of ancient and recent woodlands throughout Britain (Hall et al 2001). The NVC is now used for Phase 2 vegetation surveys as it is much more detailed than the phase 1 survey which is normally used to first classify a given habitats over a large areas quickly, using a colour coded map with target notes.As the NVC and Phase 1 habitat surveys only deal with vegetation it is important to also carry out surveys on the species that live within the habitat to ensure the whole biodiversity of the site is taken into account.
The Peterken, NVC and phase 1 classifications are reliant on the surveyor’s judgement in: 1) assessing homogenous stands of vegetation 2) being able to correctly identify the species 3) assessing the Domin Scale to each species and 4) classing intermediate stands to a single category. Ecological Site Classification:The Ecological Site Classification (ESC) used by the Forestry Commission is a PC based classification system, similar to the Biogeographic Ecosystem Classification used in British Columbia. It uses climate and soil factors in order to work out the most suitable species for a sight and can be combined with 20 NVC categories (Pyatt et al 2001). The model uses, accumulated temperature, moisture deficit, windiness, soil moisture regime, soil nutrient regime and continentality to work out the suitability of the site for a given tree species or woodland.
There are two options in using this package depending on the amount of site information available. The ‘ESC to Go’ only needs minimal information: a grid reference, the elevation and soil type, this will enable a model to work out the accumulated temperature, moisture deficit, windiness and continentality (using the Conrad Index) and will give a very rough estimate for soil type. ‘ESC Pro’ requires more knowledge about the site: soil texture, rooting depth, lithology and the field-layer vascular plans, but gives a more reliable estimate (Ray 2001).Plant indicator species are used to determine the soil nutrient regime, the percentage of cover of the dominant plants, should be taken using up to 10 quadrat samples, similar to the NVC method (Ray 2001).
The climatic information appears to be based on the grid reference and altitude of the site, which is likely to change due to the current global warming. It’s not quite clear whether or not the model will allow for these changes. The figures for the climate and soil properties have been taken form other data bases at the time the ESC was constructed.Therefore like the NVC and Peterken classifications it could be rather static, unless it is updated regularly. EU Habitats Directive: The EU Habitats Directive woodland types are very broad and as such are hard to classify. There seems to be quite a bit of information on how it relates to the classifications already in place in the UK, though these are also quite convoluted with no singular classification completely covering a Habitat Directive woodland type. This has been made even more confusing by the addition of the Biodiversity Action Plan habitats (BAPs) which are based on annex 1 habitats but are more in depth.
There is a lot of information about the status of UK BAPs but very little on how to classify them, the information I can find seems to point towards NVC communities, giving rise to the assumption that the same methods apply here as to NVC. Annex 1 of the Habitat Directive lists woodland types throughout Europe by first splitting the classifications into 6 groups: Borreal, Temperate, Mediterranean, with deciduous, conifer, mountainous and sclerophyllous attached for example: 9100) Forests of Temperate Europe or (9400) Temperate mountainous coniferous forest. 2 Sub types are coded through 9000 -9500 (9100) Forests of Temperate Europe) and either a number or a letter preceded by a zero, with the forest type described some what haphazardly by a mixture of geology, plant species (EU 2003). British woodlands are all classified within 9 categories listed under the heading Forests of Temperate Europe (see Table 2). The interpretation manual (2003) gives a brief description of the habitat classification including: regions, soil type and flora and also a corresponding classification from the countries where it maybe found.
There are some discrepancies between the interpretation manual and the 2001 report by Rodwell and Dring, which was meant to clarify the habitat directive forest types for use in the UK but only serves to confuse matters even more, by bringing in other HD types and discussing the movement between them, which although interesting, has little to do with classifying the particular woodland/forest. In particular the sub-Atlantic and Medio–European Oak or Oak-horn beam forests of Carpinion betuli, Natura 2000 code 9160 and HD 41. 4 has a different name in the Rodwell report but the same codes and the W10 NVC community is only matched with Rodwell report, because he doesn’t agree with the presence of Hyachinthoides non-scripta, ruling British woodlands out of this category (Rodwell & Dring 2001). W10 is listed in 90A0 Old sessile oak woodlands with Ilex and Blechnum in the British Isles along with W17 and W11. Table 2: UK Habitats Directive Types in relation to other UK classification types: The red NVC classes are just found in Rackham & Dring 2001 and the NVC highlighted in green are just found in the EU 2003 manual.
Adapted from Rackham & Dring 2001 and EU interpretation manual 2003). Habitats directive Annex 1 TypeNVC TypeForestry Commission TypeStand Type 9120 -Atlantic acidophilouse beech forests with Ilex and sometimes also Taxus in the shrublayer (Quercinion robori-petraeae or Ilich-Fagenion) (41. 12)W14 Fagus sylvatica – Rubus fruticosus woodland and W15 Fagus sylvatica –Deschampsia flexuosa woodland1. Lowland acid beech and oak woods8A Acid sensile oak –beech woods, 8B Acid pedunculate oak – beech woods, 8D Acid pendunculate oak-ash-beech woods and 8E Senssile oak-ash-beech woods 9130 Asperulo –Fragetum beech forests (41. 3)W12 Fagus-Mercurialis woodlands &W14 Fagus-Rubus woodland2.
Lowland beech-ash woods8C Calcareous pedunculate oak-ash-beech woods. 9160 Sub-Atlanitic and medio-European oak or oak-hornbeam forest of the Carpinion betuli (41. 24)W10 Quercus-Pteridium-Rubus woodland3. Lowland mixed broadleaf woodland9 Hornbeam woods 9180 Tilio-Acerion forests of slopes, screes and ravines 41. 4W8e-g Fraxinus excelsior-Acer-Mercurialis & W9 Fraxinus-Sorbus-Mercurialis. 4.
Upland mixed ashwoods1A,C&D Ash-wych elm woods and 3C&D hazel-ash woods and 4C Western maple-ash-lime woods. 190 Old acidophilous oak woods with Quercus robur on sandy plains. (41. 51)W16 Quercs-Betula- Deschampsia1. Lowland acid beech and oak woods6C Lowland birch –oak woods 91A0 Old sessile oak woods with Ilex and Blechnum in the British Isles. (41. 53)W10 Quercus-Pteridium-Rubus woodland, W11 Quercus-Betula-Oxalis, W16 Quercs-Betula- Deschampsia & W17 Quercus- Betula-Dicranum woodlands5.
Upland oakwoods & 6. Upland birchwoods6A Upland sessile oak woods & 6B Upland pedunculate oak woods. 91C0 Caledonian Forest (42. 51)W18 Pinus sylvestris-Hylocomium splendens.
W19 Juniperus communis ssp. Communis-Oxalis acetosella woodland. 7. Native Pinewoods11 Acid Birch-Pine and 11B Acid Oak-Pine stands. 91D0 Bog woodland (44. A1 to 44. A4)W4 Betula pubescens- Molinia caerulea woodland and W18 Pinus- Hylocmium woodland8 Wet Woodlands11 Pine Woods and 12 Birch woodland 91E0 Alluvial forests with Alnus glutinosa and Fraxinus excelsior (Alno-Pandion, Alnion incannae, Salicion albae) (44.
3)W6 Alnus- Urtica, W7 Alnus-Fraxinus –Lysimachia and W5 Alnus –Carex woodland8 Wet Woodland7 Alderwoods 91J0 Taxus baccata woods of the British Isles (42.A71)W13 Taxus baccata woodland2. Lowland Beech –ash Woods8C calcareous peunculate oak –ash-beech woods.
Perhaps the woodlands that aren’t in the Habitats Directive Annex 1 could be incorporated into BAP habitats instead, as the habitats directive is so broad and cannot possibly include every woodland type within the whole of Europe. The classifications at present are likely to be changing with climate change. Plants are going to be moving and dieing out due to temperature and precipitation changes.The present classifications are a short term solution and if the Natura 2000 network is set up then perhaps this will allow plants to move into the boards of its species range increasing its survival chances.
The problem with this classification is that it covers a wide area very inadequately, and it is therefore left to each country to try and define their own classifications based on the little information they have; the same problems as with Peterken and NVC just on a larger scale with more room for misinterpretation.Nevertheless, I think the Natura 2000 network (if it ever gets off the ground) is in theory a good idea with climate change and continued fragmentation of the landscape. Conclusion: It is thought that plant traits and functions are better for classification between sites of a similar type, as these are not affected by soil type, climate or species range to give species richness and an insight into ecosystem function (Grime 1998).Grime looks at the plant characteristics and the roles the species play in a given ecosystem, so allows for species change according to there geographical limits and environmental constraints and seems to be bases on the realized niche concept. If this was used with NVC or the HD it might allow for more diverse structural coverage of British woodlands, although it does require a conversion of vegetation coverage so that the traits can be analysed, although this allows for succession and the ability of plants to colonize it could cause more confusion.
There seems to be a plethora of classification systems available for classifying woodlands all with varying numbers of classification types. It seems that the focus has turned from the management and conservation of woodlands to their classification. I agree that it is useful to have classifications in order to gain a rough idea of what kind of management may be needed. However it seems that once a classification has been determined this dominates the whole management and conservation process, not allowing for any diversity in the management with in the woodland.The individuality of woodlands and their biodiversity could well be lost through the habitat action plans that are being set to preserve them. A lot of judgment on classification is subjective and down to the individual surveyor, if using TABLEFIT to analyse NVC data you have the choice of using Domin values or DAFOR.
DAFOR is very hard to match to Domin values and is likely to mean that the classification is even less accurate.I have yet to find a classification that categorically states that it classifies the exact habitat type of a given ‘woodland’ and I’d be very sceptic if one were to try, as nature is never exact, which is what makes it so diverse, so why are the powers that be trying to use them as such? References: Directive 92/43/EEC Treaty of Accession 2003 Annex1. European Commission (2003) Interpretation Manual of European Union habitats, EUR 25, DG Environment Nature & Biodiversity. Grime J P (1998) Benefits of plant diversity to ecosystems: immediate, filter and founder effects. Journal of Ecology. 86, 902-910.Hall J E & Kirby (1998) The relationship between biodiversity action plan priority and broad habitat types and other woodland classifications.
JNCC report 288, UK. Hall J E, Kirby K J and Whitbread A M (2001) National Vegetation Classification field guide to woodland. Joint Nature conservation committee, UK Peterken G (1993) Woodland Conservation and Management, second edition, Chapman & Hall, UK. Pyatt G, Ray D and Flecher J (2001) An ecological site classification for Forestry in Great Britain.
Forestry Commission Bullenin 124. UK. Rackhan O ( 2003 ) Ancient Woodlands, Castelpoint Press, UK.Ray D (2001) Ecological Site Classification – A PC based decision support system for British forests – users guide. Forestry Commission, UK. Rodwell J S; Pigott CD; Ratcliffe DA; Malloch AJC; Birks HJB; Proctor MCF; Shimwell DW; Huntley JP; Radford E; Wigginton MJ and Wilkins P.
(1991) British Plant Communities Vol. 1. Woodlands and scrub. Cambridge University Press, UK. Rodwell J & Dring J (2001) European Significance of British woodland types. English Nature, No.
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