Dominant, Abundant, Frequent, Occasional or Rare?

I recently volunteered to carry out a botanical survey of 3 fields on species-rich farmland in Curry Rivel. It was an excellent opportunity to work with highly experienced botanists including the two South Somerset botanical recorders, Plantlife and Somerset Wildlife Trust ecologists. The land has been managed with advice from Plantlife on meadow restoration over a number of years. The survey offered an opportunity to assess biodiversity and progress.

One of the fields was an ancient meadow, although we were not told which in advance and were surprised once we knew. Species varied across individual fields depending on the soil. One field had a pronounced ridge; another a marked damp area.

Species Lists

By the end of the survey, we had produced 4 separate lists. One field was split in two because it crossed a boundary. We concentrated on the grassland species, but also noted species within hedges. The first field contained 84 different species; the second field had 62 species with 59 species at its top over the boundary; the third field again had 84 species.

DAFOR Scale

The final lists were broken down according to the DAFOR scale used by ecologists. This voluntary work proved a good refresher for me as I studied this during my Masters in Plant Diversity. The letters of DAFOR stand respectively for Dominant, Abundant, Frequent, Occasional and Rare.

Value	Percentage Cover	Notes
D – Dominant	> 75%	Rarely used in practice.
A – Abundant	51 – 75%	Very common over most of the site
F – Frequent	26 – 50%
O – Occasional	11 – 25%
R – Rare	1 – 10%

Subjective?

Although the various categories relate to percentage cover, the scale is inherently subjective. Some assessments resulted in some lively debate and teasing among members of our group. The final tables used the categories Locally Dominant (LD), Locally Frequent (LF) and Locally Occasional (L0) which at least one member of our group was not permitted to use in her daily work. We even ended up with OLA (Occasional Locally Abundant) and OLF (Occasional Locally Frequent). Creeping Bent, Agrostis stolonifera fell into the OLA category in the top section of the second field. Corky-fruited Dropwort, Oenanthe pimpinelloides, fell into the OLF category in the second field.

Grasses

We identified some 22 different grasses across the 3 fields. False Oat Grass, Arrhenatherum elatius was the most frequent. It was even considered Locally Dominant (LD) in the second field. This identifies our fields as mesotrophic (neutral) MGI grassland according to National Vegetation Classification (NVC). This is an ungrazed grassland. We know from the farmer that it is grazed at times by sheep. Sheep are known to be selective and leave tougher grasses in stands, reflecting the patchiness seen during our survey. The MG1 classification also usually contains a layer of fine-leaved grasses. We noted 4 of the stated 5 – notably Festuca rubra (Red Fescue), Poa trivialis (Rough Meadow Grass), Lolium perenne (Perennial Rye-grass) and Elytrigia repens (Common Couch). MG1 also contains sprawling legumes. There were rare finds of Vicia cracca (Tufted Vetch) and Vicia sativa (Common Vetch) in the first field and just the former in the third field. Rubus fruticosus agg. was also frequently and suitably present trailing from hedgerows.

Other Frequent Species

There were nearly 15 non-grass species noted as frequent or locally frequent in at least one field. Yellow Rattle, Rhinanthus minor, was frequent in 3 of our 4 lists. This plant is regarded as the key to success in any wild flower meadow. It is parasitic on grasses and checks their growth to give other species a chance to compete.

Rare Species

We were excited to find two particular species hidden in the second field. We found 2 plants of Adder’s Tongue, Ophioglossum vulgatum in the lower section and two Bee Orchids, Ophrys apifera in the top section.

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Insects Galore!

The abundance of insects was marked in the 3 meadows. There were lots of butterflies, bees, grasshoppers and crickets. We saw a number of Roesel’s Bush-crickets, Roseliana roeselii, with distinctive markings, but unfortunately they did not pause long enough for me to get a photo.

So much biodiversity has been lost since my childhood. The grasshoppers and crickets seemed to jump around us with every step. They transported me back to the days when I used to walk through meadows on my way to primary school. Those sites are now housing estates. I had forgotten how they used to teem with life. It was great to spend a morning surveying farmland that favoured biodiversity again.

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References and Further Reading

• Brock, Paul D. (2021): Britain’s Insects. A field guide to the insects of Great Britain and Ireland. Princeton University Press, Woodstock, Oxfordshire.
• Brock, Paul D. (2019): A comprehensive guide to Insects of Britain & Ireland. Revised & expanded edition. Pisces Publications. Newbury, Berkshire.
• Cooper, E. A. (1997): Summary descriptions of National Vegetation Classification grassland and montane communities. No. 14. Joint Nature Conservation Committee. Peterborough.
• Eeles, Peter (2019): Life Cycles of British & Irish Butterflies. Pisces Publications. Newbury, Berkshire.
• The Flora of North-east England (?): Guidance Notes for recording DAFOR Scores

Note

Karen does not seek or receive any commercial interest or advantage from this blog. She is not promoting any business venture. She simply loves to share fascinating facts about plants. These pages illustrate her love of plants, botany, biodiversity, gardens and creative expression. There is always so much to learn about plant diversity. This blog is designed as a showcase for photography, commentary on plants and wildlife, gardens and other places visited, horticulture and related topics. Viewpoints are her own, not those of her employer.

All above photos © Karen Andrews except where Creative Commons usage stated.