Emissions of Nitrous Oxide and Nitric Oxide from Soils of Native and Exotic Ecosystems of the Amazon and Cerrado Regions of Brazil
This paper reviews reports of nitrous oxide (N2O) and nitric oxide (NO) emissions from soils of the Amazon and Cerrado regions of Brazil. N2O is a stable greenhouse gas in the troposphere and participates in ozone-destroying reactions in the stratosphere, whereas NO participates in tropospheric phot...
Saved in:
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2001-01-01
|
| Series: | The Scientific World Journal |
| Online Access: | http://dx.doi.org/10.1100/tsw.2001.261 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | This paper reviews reports of nitrous oxide (N2O)
and nitric oxide (NO) emissions from soils of the
Amazon and Cerrado regions of Brazil. N2O is a
stable greenhouse gas in the troposphere and
participates in ozone-destroying reactions in the
stratosphere, whereas NO participates in tropospheric
photochemical reactions that produce
ozone. Tropical forests and savannas are important
sources of atmospheric N2O and NO, but rapid
land use change could be affecting these soil
emissions of N oxide gases. The five published
estimates for annual emissions of N2O from soils
of mature Amazonian forests are remarkably consistent,
ranging from 1.4 to 2.4 kg N ha–1 year–1,
with a mean of 2.0 kg N ha–1 year–1. Estimates of
annual emissions of NO from Amazonian forests
are also remarkably similar, ranging from 1.4 to
1.7 kg N ha–1 year–1, with a mean of 1.5 kg N ha–1
year–1. Although a doubling or tripling of N2O has
been observed in some young (<2 years) cattle
pastures relative to mature forests, most Amazonian
pastures have lower emissions than the forests
that they replace, indicating that forest-topasture
conversion has, on balance, probably reduced
regional emissions slightly (<10%). Secondary
forests also have lower soil emissions than
mature forests. The same patterns apply for NO
emissions in Amazonia. At the only site in Cerrado
where vegetation measurements have been made
N2O emissions were below detection limits and
NO emissions were modest (~0.4 kg N ha–1 year–1).
Emissions of NO doubled after fire and increased by a factor of ten after wetting dry soil, but these
pulses lasted only a few hours to days. As in
Amazonian pastures, NO emissions appear to
decline with pasture age. Detectable emissions
of N2O have been measured in soybean and corn
fields in the Cerrado region, but they are modest
relative to fluxes measured in more humid tropical
agricultural regions. No measurements of NO
from agricultural soils in the Cerrado region have
been made, but we speculate that they could be
more important than N2O emissions in this relatively
dry climate. While a consistent pattern is
emerging from these studies in the Amazon region,
far too few data exist for the Cerrado region
to assess the impact of land use changes on N
oxide emissions. |
|---|---|
| ISSN: | 1537-744X |