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TI will consider the effects of trees under only two headings,
i) roots ii) litter. SQil org~niams are associated a.kWy with rooks
and plant remaim and will theref ore be discussea briefly under bOth
he acting s .
The soil-atabuzing action of" tree rods is w11-known
(~ournier,'1972). In many U s District woodhnda on steep
slopes, an acornlation of soil and/or atones and moat
advanced soil profile development occurs on the upslope side
of tree bases or of the main swace roots,
th~t trms
This Sldjcatas
am inhibit hg saw downhill sail ~ovement but
that they are not preventing this navement entirely.
Clearly,
Chese observations do not iniiaate that trae roots are preventing
soil erosion which would have occur-red in the absence of tmea.
The distribution of tree roots in the 803.1 depends partly
on tree specibs and partly on soil characteristics. It
used t a be thought that certain species, for example spruces,
wen typically shallm-rooting whereas others', for example
pines a d many deciduous trees, =re deeprooting. This view
has now been largely discounted and it is becdng clear th~t
m y
species can adapt their rooting form and depth &en
infl~noed by soil characteristics such as shallow depth,
stminess or a high watertable (Strtton, 1969).
%em roots come into contact with rock they appear to
cause appmciable physical disintegration and chemical
mathering.
Kla~lsing (1 956), for example, suggested that
in a beech wood granite and diorite weathered at rates of
respectively 1 .2 and 2.1 mm year"' . Evidence of weathering
in forests by the action of acids leached f'rom okgao