Plate IV. Photographs taken with a 'fish-eye' lens to show the structure of the
tree canopy and the extent to which light reaches the ground vegetation. The
two scenes represent the extremes of shade to be found in Epping Forest. The
camera was pointed vertically upwards from 50 cm above the ground; it
records almost a complete hemisphere; everything is in focus, including
distant trees, nearby plants and raindrops on the lens. The grid superimposed
on Photograph A is for the purpose of measuring the parts of the sky covered
by foliage; the curves labelled I - VII show the sun's apparent path across the
sky on the 21st of each month from December to July. The photographs were
taken on 23 July 1975, a very dull day.
A. Bury Wood. Narrow plain, some 200 m wide, oriented ENE-WSW,
bordered on the north by experimental re-pollarding. This point receives light
from about 60% of the sky, plus from 2 to 7 hours daily of direct sunlight
except in winter. Abundant ground vegetation (brambles, Deschampsia
caespitosa, etc.) and shrubs; note Juncus sp. to NE of camera.
B. Great Monk Wood. Old pollard beeches long uncut and overgrown.
When the trees are in leaf this point receives a minute fraction of daylight and
no direct sunlight other than small sunflecks. The intense shade has eliminated
all shrubs; ground vegetation is reduced to Leucobryum glaucum and sparse
Deschampsia flexuosa.
O. Rackham and D. E Coombe
74