Our understanding of the controls on N-cycling and availability in for
est soils following disturbance is limited. A comparative study was co
nducted to examine the spatial distribution of soil N in forest soils
and assess the effects of site disturbance. Sampling grids were establ
ished within a 120 x 120 m representative area at a native site, and a
t recently (i.e. 4-year-old) burned and clear-cut sites. A three-dimen
sional classification of landscape form was used to stratify each land
scape into distinct landform elements. The spatial distribution of ino
rganic-N was not related to landform element, irrespective of site dis
turbance, indicating an absence of topographic control at the scale st
udied. However, a narrowing of the NH4+-to-NO3- ratio at the clear-cut
site compared to the native site suggests that N-cycling was influenc
ed by site disturbance. Similarly, an increase in the size of the micr
obial biomass at the clear-cut site, coupled with a widening of the mi
crobial biomass C-to-N ratio, suggest that disturbance altered both th
e size and composition of the microbial biomass. Potential N and C min
eralization, and net nitrification in the forest floor and surface min
eral horizons representing two distinct landform complexes were studie
d in a controlled aerobic 8-wk incubation experiment. Accumulation of
NH4+ and NO3- differed markedly between sites although the effects of
topographic position were generally non-significant. Inorganic-N accum
ulated principally as NH4- in soils From the native site due to an ext
ended lag in nitrification. In contrast, NH4+ accumulation in soils fr
om the recently disturbed sites remained limited, whereas NO3- accumul
ation predominated. Thus, although topography did not markedly influen
ce N distribution at the scale studied, site disturbance had a direct
effect on N-cycling processes in these forest soils.