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is associated hith variability in the pattern of rainf'a.ll
and in the ev~porztion of intercepted ~ at~r (~ubter, 1972;
Stewart & Oliver, 1972). Evaporation is likely to be
fastest and hence possibly greater during the warmer
conas. In low-growhg vegetation, t nnspiration and
evaporation are of sirrjlar magnitude but evspara.tion of
interoepted water fr~m for< st is gruater than transpimtiion
loss (~ufter, 19681, up to five tines greater under windy
conditions because af the aercdynar;jc roughness of the tree
oanopy (Ruttar, 1972).
In watershed studies at Cmeeta, USA (~oover, 19441,
clearfelling of mixed hardwoods increased run-off
by nearly 53% wid m-off as a p ercentage of incident
rainfall from to 59$ (c. 41 -6% according to ITi3bert,
1967). D~ta from ot ht r sites sunnariaed by Hibbert (1967)
indicate incmases in run-of"E of the same mJer or less
seer clea~felling forest. At Coweta, eetablisbnt
and growth of pines for 36-1 7 years on two catchments
reduced streamflow to 2 6 below the value expected for a
hrdwood st snd {Swank & Dqlasa, .1974),
fieparation of an area for planting of trees ort~n involves
drainage operations. Fron studies by Pafntor ot al., (1974)
on catchaents with variable soils (peaty pdzols, pe&t,
boulder clay, sand) on Plynljmon in riel~s and at Cmlburn
in north-west England the se operations can led to a
1000-fold incr~ase in los~
of particulate matter and
presumbly also in nutrients. A similar b& sndler
ef'fect occurs mhen an are:. is clearfelled (~omlan et .al.,
19&; Likens et al., 19?0), although Packer (q 967)
conoludes that clearfelling itself is virt-