114 Utilisation of Molinia caerulea Tussocks by Overwintering Beetles at Epping Forest
Two - Way Analysis of Variance was used to explore the difference in % water by weight of each site
and top and bottom core sections. This tested 4 specific null hypothesis about the distribution of %
water content. It was found that; % water by weight of top and bottom core sections was significantly
different (P< 0.01), the bottom sections being wetter, and that there was a significant difference
between the total water content of cores over the 3 sites (P< 0.01). By plotting the means and 95%
CL. (Fowler & Cohen 1995) it became apparent that the difference lay between sites 2/3 and 1 as
the 95% CL. for site 1 are isolated (table 1)
From analysis of tussock dimensions and core water content it is possible to state that tussocks
sampled at site 1 were significantly smaller (although not shorter) and dryer than those of the other
2 sites, the volumes and water contents of which did not differ significantly (assuming water content
of cores was representative of whole tussocks).
Beetle abundance and diversity
Numbers of individuals per site and the top/bottom distributions in the cores are given in table 2.
Site 1 harboured the greatest species richness, 12 species in all, with the carabids Agonum obscurum
and Pterostichus diligens, the staphylinids Tachyporus hypnorum and Atheta spp. and Trixagus
dermestoides being most abundant whilst the remaining 7 species occurred in low numbers. It is also
apparent that the majority of individuals occur in the top sections of the tussock cores and that many
of the rarer species are completely absent from the bottom sections, the species of the flooded site 3
are all absent from bottom sections with the exception of T hypnorum.
Table 2. Numbers of individuals for each species from each site including
top and bottom core section distributions and totals
Table . Numbers of individuals present in 12 cores per site are in bold, numbers
of individuals in top and bottom core sections are in brackets as; (Top - Bottom),
-denotes no record.
Essex Naturalist (New Series) 17 (2000)