Simulation of nitrous oxide and nitric oxide emissions from tropical primary forests in the Costa Rican Atlantic Zone

Abstract

Nitrous oxide (N 2 O) and nitric oxide (NO) are important atmospheric trace gases participating in the regulation of global climate and environment. Predictive models on the emissions of N 2 O and NO emissions from soil into the atmosphere are required. We modified the CENTURY model (Soil Sci. Soc. Am. J., 51 (1987) 1173) to simulate the emissions of N 2 O and NO from tropical primary forests in the Atlantic Zone of Costa Rica at a monthly time step. Combined fluxes of N 2 O and NO were simulated as a function of gross N mineralization and water-filled pore space (WFPS). The coefficients for partitioning N 2 O from NO were derived from field measurements (Global Biogeochem. Cycles, 8 (1994) 399). The modified CENTURY was calibrated against observations of carbon stocks in various pools of forest ecosystems of the region, and measured WFPS and emission rates of N 2 O and NO from soil to the atmosphere.WFPS is an important factor regulating nutrient cycling and emissions of N2O and NO from soils making the accuracy of the WFPS prediction central to the modeling process. To do this, we modified the hydrologic submodel and developed a new method for the prediction of WFPS at the monthly scale from daily rainfall information. The new method is based on: (1) the relationship between monthly rainfall and the number of rainfall events, and (2) the relative cumulative frequency distribution of ranked daily rainfall events. The method is generic and should be applicable to other areas.Simulated monthly average WFPS was 0.68±0.02 -identical with the field measurement average of 0.68±0.02 from the annual cycle observed by Keller and Reiners (Global Biogeochem. Cycles, 8 (1994) . The simulated N 2 O/NO ratio was 11.2±1.9 compared with the measured value of 10.9±4.7. WFPS is the dominant determinant of the fraction of gross N mineralization that is emitted from the soil as N 2 O and NO. If WFPS were not limiting during part of the year, this fraction would be 4.2%. With some periods of lower WFPS, the realized fraction is 2.2%. Because of the strong relationships between N 2 O and NO emission rates and rainfall and its derivative, WFPS, these moisture variables can be used to scale up nitrogen trace gas fluxes from sites to larger spatial scales.

Modeling carbon dynamics in vegetation and soil under the impact of soil erosion and deposition

“…For example, Figure A2 shows that monthly rainy days increase nonlinearly with the amount of monthly precipitation at Batesville, Mississippi. Such a relationship can be found in other regions as well (e.g., in a tropical rainforest climate [Liu et al, 2000]). In EDCM, we use the long-term distribution of daily rainfall to allocate monthly precipitation to each individual rainy day in the month.…”

“…The basic concept of the hydrological submodel is based on work by Liu et al [2000], but there are several important modifications. The new model uses statistical relationships to estimate the number of rainy days in a month and then allocate the total monthly rainfall to each rainy day.…”

Nitrous oxide emissions from tropical hydroelectric reservoirs

“… b References: 1, this study; 2, Richey et al [1988]; 3, Delmas et al [2001]; 4, Davidson et al [2001]; 5, Garcia‐Montiel et al [2003]; 6, Sikar et al [2005]; 7, Keller and Reiners [1994]; 8, Liu et al [2000]; 9, Keller et al [1986]; 10, Sanhueza et al [1994]; 11, Donoso et al [1993]; 12, Hao et al [1988]. …”

Mapping the climate of Puerto Rico, Vieques and Culebra

“…Running and Gower, 1991;Running and Hunt, 1993). These models can also use monthly climate data (Tian et al, 2000;Wang et al, 2002), and include examples of predicting nitrogen trace gas emissions from soils (Liu et al, 2000).…”