112 Utilisation of Molinia caerulea Tussocks by Overwintering Beetles at Epping Forest
2 were sampled from the N.W. corner, near to the wood. The flooded area forming site 3 was more
central.
Deer-shelter Plain, approximately 1 km. N.E. of site 1, is a large area of wet grass heath with occasional
birch. Erica teralix and Calluna vulgaris arc also present.
There are natural springs in the south of the area and the shallow channels which flood the bases of
tussocks at site 3 are generally seasonal in nature. The water table at deer-shelter Plain site 2 was just
below ground level. Despite both sample areas containing flooded and unflooded tussocks, for the
purposes of the discussion the term 'site 2' refers only to unflooded tussocks sampled. Similarly
'site 3' refers only to flooded tussocks sampled. All sites lie on pebble gravel with underlying
Claygate beds which impede drainage to some degree.
Sampling took place during February 1999, over 2 days of comparable weather. Care was taken to
sample on rain free days to insure that water content of cores would not be markedly increased.
Methods
Initially, whole tussocks were sampled. This method is preferable as it yields greater numbers and
diversify of beetles and represents the whole tussock fauna . However due to constraints set by
available equipment, time and transportation, a more efficient, if less extensive sampling programme
was adopted.
Core sampling
Instead of sampling whole tussocks they were cored. This enabled more samples to undergo extraction
simultaneously and reduced the volume and weight of transportable material.
At each site tussocks were sampled randomly by the 'Plotless' method. Only tussocks with a basal
circumference > 70cm. and a height of at least 15cm were sampled; smaller tussocks broke up
during sampling. For sites 2 and 3 only flooded or unflooded tussocks were sampled. 12 tussocks
were sampled from each site; the number being limited by the availability of Tullgren funnels.
Once suitable tussocks were randomly chosen, the basal and uppermost circumferences were
measured, as was the height from ground level to the top of the well defined denser material. These
dimensions allowed calculation of approximate tussock volume. Ambient and tussock centre
temperatures were also taken.
The corer, with an internal diameter of 8.5cm, was screwed down into the centre of the tussock to a
depth of 30cm. Once removed from the corer the bulk of soil on the bottom of the core was removed
and the core was cut in two at a depth of 10cm. The proportion of soil in the lower part of the bottom
section varied between tussocks, although in each case the root and litter material was dense with a
small amount of soil in the spaces. Total core volume varied slightly, with tussock height. However
each core can be considered to be a standard sample in that it represents the beetle diversity of a
uniform cross sectional area and the totality of tussock below it. Each core section was sealed in a
polythene bag and labelled.
Approximately 2 hours after sampling the cores were removed from the bag and weighed in the
laboratory. Samples were then gently teased apart and the material from each section placed in a
Essex Naturalist (New Series) 17 (2000)