Increasing nitrogen deposition due to human activity might have a serious i
mpact on ecosystem functions such as the nitrogen transformations conducted
by microbes. We therefore focused on nitrous oxide (N2O) production as an
indicator of soil microbial activity. The rates of N2O emission from the fo
rest floor were measured every two weeks in two forest stands in the centra
l part of Japan: a red pine stand at Kannondai and a deciduous stand at Yas
ato. Nitrogen deposition rates by throughfall were 30.6 kg N ha(-1)y(-1) at
Kannondai and 15.7 at Yasato. The rates of N2O emission ranged from 0.5 to
14.2 mug N m(-1)h(-1) (mean 4.5) at Kannondai and from 0.2 to 7.0 mug N m(
-2)h(-1) (mean 2.3) at Yasato. The N2O emission rate showed significant pos
itive relationships with soil temperature and nitrogen deposition during th
e preceding two weeks. The annual emission rates of N2O were 0.38 kg N ha(-
1)y(-1) at Kannondai and 0.20 at Yasato. As a percentage of the annual nitr
ogen deposition, these rates were 1.23% at Kannondai and 1.27% at Yasato.