Gharahi Ghehi, N., Werner, C., Hufkens, K.,
Kiese, R., Van Ranst, E., Nsabimana, D., Wallin, G., Klemedtsson, L.,
Butterbach-Bahl, K., and Boeckx, P.: Detailed regional predictions of N2O and NO emissions from a tropical highland rainforest, Biogeosciences Discuss., 10, 1483-1516
Abstract.
Tropical forest soils are a significant source for the greenhouse gas
N2O as well as for NO, a precursor of tropospheric ozone. However,
current estimates are uncertain due to the limited number of field
measurements. Furthermore, there is considerable spatial and temporal
variability of N2O and NO emissions due to the variation of
environmental conditions such as soil properties, vegetation characteristics
and meteorology. In this study we used a process-based model
(ForestDNDC-tropica) to estimate N2O and NO emissions from tropical
highland forest (Nyungwe) soils in southwestern Rwanda. To extend the model
inputs to regional scale, ForestDNDC-tropica was linked to an exceptionally
large legacy soil dataset. There was agreement between N2O and NO
measurements and the model predictions though the ForestDNDC-tropica
resulted in considerable lower emissions for few sites. Low similarity was
specifically found for acidic soil with high clay content and reduced
metals, indicating that chemo-denitrification processes on acidic soils
might be under-represented in the current ForestDNDC-tropica model. The
results showed that soil bulk density and pH are the most influential
factors driving spatial variations in soil N2O and NO emissions for
tropical forest soils. The area investigated (1113 km2) was estimated
to emit ca. 439 ± 50 t N2O-N yr−1 (2.8–5.5 kg N2O-N ha−1 yr−1) and 244 ± 16 t NO-N yr−1 (0.8–5.1 kg N ha−1 yr−1).
Consistent with less detailed studies, we confirm that
tropical highland rainforest soils are a major source of atmospheric
N2O and NO.
