Using aerobic long-term incubations of 174 days, carbon and nitrogen m
ineralization, pools of potentially mineralizable C and N, microbial C
and N, and leaching of organic CaCl2-extractable C and N were determi
ned in forest floor material (O-F and O-H) and mineral soil (0-5 cm) c
ollected along a gap-stand gradient. Sample locations were the centre
of gaps, the northern part of gaps, the northern edge between gaps and
stand, and a mature European beech stand. Conditions changed along th
e gradient in (a) soil moisture, which was highest in the gap centre,
(b) soil temperature, which was elevated in the northern part of the g
ap and at the northern edge, and (c) active tree roots, which were abs
ent from the gap centre and the northern part. Samples were collected
21 months after gaps (30 m dial had been created. Because N mineraliza
tion in the field during the first year after gap creation was higher
in the gap than in the stand but lower in the second year, it was hypo
thesized that mineralizable substrate had been partially depleted unde
r gap conditions. No differences were found between the gap and the st
and in forest floor mass, or forest floor and mineral soil C and N con
centrations. In the forest floor, C and N mineralization, and conseque
ntly the potentially mineralizable C and N, as derived from first orde
r mineralization kinetics, decreased in the order stand > northern edg
e > gap centre > gap north. Amounts mineralized were 1053, 861, 761 an
d 610 g N g(-1) and 24.4, 22.6, 22.5 and 20.2 mg C g(-1) respectively.
In mineral soil, these values were highest in the gap centre. A subst
antial decrease in microbial biomass occurred in samples from the gap
centre during incubation. Other samples showed no marked decrease in m
icrobial biomass during incubation. In the forest floor a shorter turn
over time of mineralizable N was observed for gap locations, whereas t
he turnover of mineralizable C was slower in the northern part of the
gap and the northern edge. This suggests that potentially-mineralizabl
e pools of C and N were affected differently by either rooting, moistu
re or temperature. Similar turnover times (4-11 weeks) for potentially
-mineralizable N in both forest floor and mineral soil suggested simil
ar sources of mineralized N. Potentially-mineralizable C consisted of
more recalcitrant fractions in mineral soil than in forest floor. Nitr
ogen immobilization in the form of CaCl2-extractable organic compounds
was unimportant in this soil. Organic N (N-org) in CaCl2-leachates wa
s 4-12% of mineral N. Kinetic parameters indicated that N mineralizati
on in the second year after gaps had been created was lower in the gap
s, because mineralizable C and N pools had decreased. Copyright (C) 19
96 Elsevier Science Ltd.