Download (1906Kb)

5. Sulphate in st rean-wat ar decreased bec2use ~f increased
run-off and eliaimtion of sulphate generation within the
syst8D.
6, Sremmaker tenperaturea were higher aftar deforestation
0 0
and varied 3 -4 C diurnally in smer ompamd with virkual
constancy prior to felling.
The mnzgement pr:~ctices used by =ens
ot al. , provention of
regrowth of all vegetation afier clearfelling by use of
herbicide, no cunatruction and use of forest roads and no
removal of felled trees fiorc their site, were very different
frm norm1 forestry opcrat ions in IT, S.A. and ix Europe so
their results are likely to he of limit ad applicability
generally.
Soppor (1 975) has placed then in the cwtexb
of results f'rm numerous other catckment studies in North
America and canaluded that sediment and turbidity problems
can be minindaed by careful siting and const metion of Logging
rwds, stream tenporature changes can be avoiba by leaving
a narrow strip of trees or brush alongside strew: and
nutrient losses following clea~cutting are snaU to negligible
if rapid revegetation of the site occurs, The iqortunce
of a contkuous vegetation cover 2nd its associakd litter layer
in retaining nutrients on a site hsts been stressed by Thorns
Bc G~iga1 (I 976) for evergreen mountain laurel in Tennessee,
Tam et d., (197b) also reviewed the effecta of forest
operations with particular relevance to Europe. They provide
evidenoe that nitrate - 1V increases up to &fold in water fiwn
clear-cut areas parkicularly on the more fertile soils,
Addition of N fertilizers, particulmly armaonim nitrate, can
lead to large tnore&ses in N content of atrear~water and
ground water. The fate of added nitrogen on c1ea.r-felling
is debatable but the scanty available avidence suggests that