Nitrous oxide dynamics in managed northern forest soil profiles: is production offset by consumption?
Kellman, L. and K. Kavanaugh. 2008. Biogeochemistry 90: 115-128
Abstract
This study investigates soil N2O dynamics
in forest soils representing early (3-years) and late
(>50 years) post-harvest succession in Atlantic Canada
over a 9-month snow-free period in order to
develop a better understanding of the role of managed
forests as sources and sinks of N2O. We couple
measurement of surface flux with detailed measurements
of subsurface N2O concentrations at four
mineral soil depths (0, 5, 20 and 35 cm) at 40 plots
located within four sites. Median surface fluxes were
similar at all sites regardless of the management stage
(-5 to 19 ugN2ON/m2/day), with all sites behaving
as net sinks and sources of N2O over the
measurement period. Subsurface mineral soil N2O
concentrations at early (3-year) post-harvest succession
sites, which ranged from median values of
362 ppbv at 0 cm to 1783 ppbv at 35 cm depth, were
significantly higher than late post-harvest succession
sites where median concentrations ranged from
329 ppbv at 0 cm to 460 ppbv at 35 cm depth.
Examination of relationships between subsurface gas
storage and surface flux magnitudes, suggested
although recently harvested forest soils may be
producing N2O at a greater rate than mature forest
soils, observed patterns are consistent with a strong
sink for this gas that prevents its conservative
transport through the soil profile, and ultimate
emission to the atmosphere through the majority of
the measurement period.
Key Words
Nitrous oxide, Forest management, Greenhouse gases, Climate change
