Introduction to axiophytes

Axiophytes are ‘worthy plants’ - the 40% or so of species that arouse interest and praise from botanists when they are seen. They are indicators of habitat that is considered important for conservation, such as ancient woodlands, clear water and species-rich meadows.

They are not the same as rare plants: species that have only ever been recorded in one or two sites in a county are often just chance occurrences, and have little ecological (or statistical) significance.

Lists of axiophytes provide a powerful technique for determining conservation priorities. Sites with many axiophytes are usually of greater importance than those with fewer; and changes in the number of axiophytes in a site over time can be used for monitoring the outcome of management practices.

It is not entirely a new concept. In Britain, the Wildlife Trusts in particular have for a long time been interested in using lists of indicators for assessing sites. Now, the combination of the BSBI’s expertise and the existence of comprehensive databases for manipulating large quantities of data make this process a much more realistic prospect.

The system for assigning plants depends on first drawing up a list of habitats of conservation importance. The axiophytes are those species which are:-

• 90% restricted to these conservation habitats;
• recorded in fewer than 25% of tetrads in the county.

An exception to the 25% rule can be made for species in conservation habitats that are particularly well represented and widespread in the county.

It should not be assumed that a very rare species that just happens to be in a good site is an indicator of that habitat - look at its distribution elsewhere for evidence of this.

The BSBI project

To date, fourteen counties in the British Isles: Dorset, South Hampshire (both vcs), Sussex (both vcs), Berkshire, Staffordshire, Shropshire, Cardiganshire, Lincolnshire (both vcs), Cheshire, South Lancashire, Co. Durham, Northumberland, Clyde Islands & Waterford) have drawn up lists of axiophytes. When a few more have done so, we shall analyse and compare the lists to understand them more fully, and draw up recommendations. In the meantime, you can download the available lists here (tables updated 5/6/2008).

Suggestions for use

Save the Excel table on your computer. Sort the data by the county you are working in and delete the rows that are irrelevant for your county. This leaves you with the list of species that are considered axiophytes for your county.

When you get a species list for, say, a site, paste the axiophyte list into it and then use one of Excel’s functions (e.g. a pivot table) to work out how many of the species in your site are axiophytes.

Progress to date

Visit the Natural Shropshire web site to see how habitat areas can be prioritised using axiophyte data.

Read our most recent report (pdf 96kb) on axiophytes in the Meres & mosses.

Download Mick Crawley’s Axiophytes of Berkshire (pdf 490kb).

Acknowledgements

My thanks to Arthur Chater, Margaret Cole, Mick Crawley, John Durkin, Dave Earl, Una Fitzpatrick Paul Green, Quentin Groom, Angus Hannah, John Hawksford, Graeme Kay, Alan Knapp, Clare & John O’Reilly, David Pearman, Martin Rand, Sarah Whild, Dan Wrench.

- Alex Lockton

What are axiophytes for?

1. Evidence for site designation

Lists of axiophytes for various BAP habitats can be used as an empirical measure for sites of nature conservation interest. This allows landowners and others to see why decisions have been made and makes them less vulnerable to challenges on scientific grounds.

2. Protecting the wider countryside

Each grid square in the countryside can be assigned a number according to the total number of axiophytes present. For axiophyte-rich squares, full surveys need to be carried out, and potentially damaging operations can be directed away from the most important areas.

3. Monitoring site condition

Because lists of axiophytes are much longer than the lists of rarities, they are much more sensitive to changes in ecology. If protected sites and nature reserves had lists of axiophytes, their abundance could be measured over the years and decades to see how well they are performing. Ellenberg Values can be calculated from the species lists, showing trends such as increasing eutrophication.

4. Prioritising resouce allocation

Because each site can be ranked according to the number of axiophytes it contains, a relative scale of site importance can be created, using a quantifiable method. Axiophytes are therefore a more effective way to allocate conservation resources.

Sites which have lost the most axiophytes most recently might well be the most promising ones for restoration. Targets can be set and monitored by specifying which axiophytes will benefit.