Pulsatilla vulgaris (L.) Mill. - Plantlife

7.4 Monitoring and the Common Monitoring Standard
Traditionally Pulsatilla vulgaris has been monitored by simple counts of flowering ‘crowns’ or
estimates based on densities in small areas (e.g. Tarpey, 1999). These provide an overall
assessment of year to year variation but are limited for a number of reasons. First, ‘crowns’
do not represent discrete genets due to the production of offshoots close to parents. The total
count is therefore likely to overestimate the total size of the population possibly by orders of
magnitude. Second, grazing can have a marked influence on estimates especially on sites
where livestock are present during the flowering period. Third, such counts do not take into
account the life-stage structure of the population or whether recruitment is taking place
through the production of seed, presence of juveniles, etc.
Possible alternative approaches include counts within fixed plots as has been carried out at
Barnack Hills and Holes in Northamptonshire since 1975 (Fig. 15). This should preferably
include a number of demographic parameters, including the individuals in different lifestages,
flowering performance, seed production etc., and relate these environmental
variables such as sward height, % cover of bare ground, ‘hits’ on dominant grasses, etc. Simple
counts of rosettes rather than flower stems is probably a more preferable performance
parameter given the dramatic fluctuations in the numbers of flowers observed on some sites
(e.g. Fig. 15). These are less affected by seasonal factors and grazing and therefore provide a
more accurate assessment of the size of populations (Bailey, 1996). However, all these
approaches are likely to be time consuming to carry-out and therefore dependent on available
expertise, time and resources.
8 References
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