J J Day
Edwin Lees, in Botany of Worcestershire 1867, presents his systematic list in the form of a table divided into four Botanical Divisions: The Table of Plants. For each species, an assessment of abundance is given for each division. He gives 13 categories of abundance/distribution which are applied to all species. In addition, three relating to habitat and four relating to status are noted when appropriate. Interpretation of the 13 categories relating to abundance/distribution present a number of difficulties. These relate mainly to the two parameters of geographical distribution and abundance being insufficiently defined and combined or confused by Lees. Furthermore, their application is not always consistent. Despite this the 13 categories seemed too close to the ten frequency classes defined in the Checklist of the Worcestershire Flora (Day, J.J. 2000) to be ignored. Having come to an understanding of Lees' categories after entering the whole of Lees' Table of Plants (about 3500 records) onto the database the Lees categories were aligned to the ten point scale in the Checklist.
|
Frequency class |
Number of monads |
Percentage of monads |
Score |
|
Very common |
1501+ |
>75-100% |
1 |
|
Common |
1001-1500 |
>50-75% |
2 |
|
Widespread |
501-1000 |
>25-50% |
3 |
|
Widespread but localised |
201-500 |
>10-25% |
4 |
|
Uncommon |
101-200 |
>5-10% |
5 |
|
Scarce |
51-100 |
>2.5-5% |
6 |
|
Very scarce |
26-50 |
>1.25-2.5% |
7 |
|
Rare |
13-25 |
>0.6-1.25% |
8 |
|
Very Rare |
1-12 |
0.05-0.6% |
9 |
|
Extinct |
0 |
0% |
10 |
Above: Table of Checklist Frequency Classes (Day, J.J. 2000)
|
Lees’ Classes |
Assigned to checklist class |
|
General |
1 |
|
Plentiful |
2 |
|
Many places |
3 |
|
Abundant |
3 |
|
Not uncommon |
4 |
|
Not common |
5 |
|
Various places |
5 |
|
Several places |
6 |
|
Rather uncommon |
7 |
|
Occasional |
7 |
|
Very uncommon |
8 |
|
Numbered sites (1-4 localities) |
9 |
|
Extinct |
10 |
Above: Table of Lees’ classes and assignment to Checklist class
The Pea Family, Fabaceae were selected to test the methodology .
The assigned Checklist values were applied to the Lees categories. This for each species and within each district. The values were summed and divided by four to give a county average. Where a species was not present in a district in was assigned a rarity value of 10.
The Lees county averages were compared to the Checklist frequency class and the species ranked according to degree of change.
These are first draft results and the following notes should be taken into account before drawing conclusions.
| they are not a direct comparison, the modern assessment is based on geographical distribution as a measure of frequency, Lees includes local and relative abundance. |
| the modern survey has covered the ground more systematically and thoroughly (see distribution map elsewhere of all records to 1875); it will be likely to overestimate uncommon species in relation to Lees. |
| 2001 assessment is strictly numerical, Lees is an estimation from memory, his method is not good at ranking fairly common and widespread species |
| Lees' evaluations may need minor refinements |
| Lees has a tendency to inconsistency and error |
| Lees assessments change as he works through list (but not consistently) |
| Lees values have not been adjusted for the different areas of Botanical Districts, this is important as the 2001 classes are based on area. |
| Lees missed species (the Vicia orobus record is a herbarium specimen of Lees) |
| Lees did not know either the Lickey Division or the upper Teme valley well; there are under assessments here |
| loss within last 30 years not taken into account |
The results are presented below. They indicate a number of trends but should not be taken as a template for the flora as a whole. It is not a random sample and is highly unlikely to be representative of the entire flora. This is a single family with biological unity, especially in regard to physiology and breeding strategies.
Those species showing no apparent change or declines are similar to expected. This gives credence to the methodology as an agent for measuring change. There is a surprise, however, with the large group of species exhibiting apparent increases. This family, as a unit appears to have done well out of the land use changes of the past 150 years. The results seem reliable with regard to the spread of non-native species. However, there are some features which suggest that a further refinement of the method may be needed. Some anomalies may be due to Lees' inconsistencies. For instance, the surge in Medicago lupulina was entirely unexpected and will need verification against other sources. There is also a group of uncommon natives which indicate a low level of increase. I suspect this may be an artefact of recent survey effort and they are species in decline, having been under-recorded in the past.
In summary, the overall trends and patterns appear to be real, in the majority of cases, but the levels of change should not be taken as absolute values.
CHANGE 1867 - 2000
In the list that follows the First number = frequency based on Lees 1867 and the Second number = frequency based on Day 2001. X = not recorded in Lees Table of Plants
Species with No Apparent Change
tend to be :
| very common species |
| very rare species (where suitable habitat has survived) |
Species with Apparent Declines
tend to be:
| scarce natives confined by habitat |
| light demanding perennials (grassland / heath & saum communities) |
Two order decline
Onobrychis viciifolia 7 9
Trifolium campestre 1 3
Ulex gallii 3 5
Three order decline
Lathyrus linifolius 1 4
Genista tinctoria 1 5
Extinctions
Lathyrus palustris 9 10 Extinction
Trifolium scabrum X(9) 10 Extinction
Vicia orobus X(9) 10 Extinction
tend to be:
| non-native taxa |
| species associated with specific grassland management regimes |
| plants of tall grassland (climbers) |
| plants of tight grazed grassland (impact of motor mowing) |
| annuals |
| colonists, plants of disturbed ground and arable habitats |
Two order increase
Vicia hirsuta 4 2
Trifolium medium 5 3
Melilotus altissimus 6 4
Medicago sativa subsp. sativa 7 5
Trifolium arvense 7 5
Trifolium micranthum 7 5
Lathyrus sylvestris 9 7
Medicago polymorpha 9 7
Medicago minima X 9
Medicago sativa subsp.falcata X 9
Melilotus indicus X 9
Melilotus sulcatus X 9
Trifolium ornithopodioides X 9
Trifolium subterraneum X 9
Trifolium aureum X 9
Trifolium resupinatum X 9
Vicia lutea X 9
Three order increase
Lotus pendunculatus 6 3
Lathyrus nissolia 7 4
Lathyrus grandiflorus X 8
Four order increase
Medicago lupulina 5 1
Melilotus officinalis 9 5
Five order increase
Lathyrus latifolius 10 5
Medicago arabica 9 4
Melilotus albus X 6
Vicia faba X 6
Eight order increase
Trifolium hybridum X 3
References:
| DAY, J.J., Checklist of the Worcestershire Flora, 2001. |
| LEES, E., Botany of Worcestershire, 1867. |