116 Utilisation of Molinia caerulea Tussocks by Overwintering Beetles at Epping Forest
Discussion
Reliability of Results
The cut off point separating top and bottom sections of cores was purely arbitrary and unless otherwise
stated further discussion refers to whole cores or pooled numbers per site. Due to possible mortality
caused by coring, transportation or extraction numbers of beetles in cores are if anything, under-
represented. It is important to note that the sample size was not particularly high and that although
the total number of species for each site was recorded within the first 8 or 9 samples, it is not
possible to state whether a more extensive programme would reveal a greater diversity of beetles. It
is also important to bear in mind that the cores only represent a percentage of the tussock and that the
total coleopterous diversity and abundance is almost certainly greater. Luff (pers. comm.) suggests
that coring may exclude larger species overwintering at the edges of tussocks.
Species general habitat associations and records
Generally habitat associations and relative abundances of the species recorded in this study agree
with those of other comparable studies. All species have been previously recorded in Epping Forest
(Hammond 1995 & 1999).
Agonum fuliginosum, the most abundant of carabids in the unflooded tussocks of the wet heath is
widely regarded as a wetland or marsh inhabiting species (e.g. Dawson 1965, Hammond 1999 &
Luff 1965). A. obscurum was less frequent at site 2 but abundant at site 1, this is in agreement with
Hammond's (1999) classification of the species as markedly moisture demanding but not exclusive
to wetlands.
In accordance with the results of this study, Dawson (1965), working on similar habitat found A.
obscurum, A. fuliginosum and Pterostichus diligens to be the 3 most abundant carabids, and Holmes
et al. (1993) found the latter 2 to be among the 4 commonest carabids of a Welsh wet heath.
Tachyporus hypnorum was the most abundant of species and this is representative generally of its
very common status . Of the remaining staphylinids identified to species, all but Stenus providus
were recorded in the vicinity of a Yorkshire wet heath (Bauer 1989) and also in low numbers (< 6
indiv. /10 traps / yr. , ().()5) confirming that the
broader habitat differences did not affect the numbers of carabids in tussock cores. It was also found
that the numbers of staphylinids did not differ significantly between samples at each site (Anovar,
P>0.05).
Essex Naturalist (New Series) 17 (2000)