Download (1906Kb)

Fo=sts have an appreciable influenoe an the hydrology of a site,
including soil moisture st:it us md run- off. Frm spirtj.tion mtes in
forest and grasslarid are of approximately the sa2.e ardor but forest3
intercept up to half, but more commonly around 2@40;6 of precipilation,
of'ten several tines the interception for grassland, Intercepted water
is evaporated so the soil tends to be drier and less let~ched under
forest than under dense grzssland.
Site preparation leads to a 103s of particulate matter and nutrients in
run-off, which may continue for several years after planting of the
fo~st. Rcdnaking also incmases soil en& nutrient loss frcm the site
temporarily.
Felling, o specially clear-f elling, leads to hcreuse s in a Oi1 leachf ng,
in run-off,
run-off.
and in the amounts of particulate mtsr5al and nutrients in
Soil and nutrient loss is only slight if loming is
carried out carefully, a h d if rapid regrowth of herbaceous vegetation
occurs.
Feliiiing lezds to increases of several OC in mean soil and
at ream temperature and in the diurnal temperature mn ge.
Tehperatul-e
ohanges will have an appreciable effect on the numbers and activities
of fauna, flora and microflora of these habitats.
Fertilizers and herbicides used in fomstry, affect the quality of the
run-off water only slightly and temporarily, if they are applied
carefully. However, theywill have aom effect on the soil by
altoring biolo&ic*.l zctiviky or the type and amount of plant remains
reackdng the soil surfme.
Forest systems, in contrast with non-forest systems, accumulate a large
nutrient capital in the trees themsulves and in the plant remains on,
and in, the soil, Factors which favour,this build up include evergreen
oor~dition of mny forest trees, resistance to decmpoaition of litter,
exploitation of n greater soil volume by tme root3 than by roots of
pssland and moorland plmt s , except pe rfiapa Yteridium, greater t rapphg
of aerosols &d possibly greater minerel weathering under fo~st than
under non-f ore st.