『Abstract
Nitrous oxide (N2O) emission from agricultural
land is an important component of the total annual greenhouse
gas (GHG) budget. In addition, uncertainties associated with agricultural
N2O emission are large. The goals of this
work were (i) to quantify the uncertainties of modelled N2O emissions
caused by model input uncertainty at point and landscape scale
(i.e. resolution), and (ii) to identify the main sources of input
uncertainty at both scales. For the Dutch western fen meadow landscape,
we performed a Monte Carlo uncertainty propagation analysis using
the INITIATOR model. The Monte Carlo analysis used novel and state-of-art
methods for estimating and simulating continuous-numerical and
categorical input variables, handling spatial and cross-correlations
and analyzing spatial aggregation effects. Spatial auto- and cross-correlation
of uncertain numerical inputs that are spatially variable were
represented by the linear model of coregionalization. Bayesian
Maximum Entropy was used to quantify the uncertainty of spatially
variable categorical model inputs. Stochastic sensitivity analysis
was used to analyze the contribution of groups of uncertain inputs
to the uncertainty of the N2O emission at
point and landscape scale. The average N2O
emission at landscape scale had a mean of 20.5 kg N2O-N
ha-1 yr-1 and a standard deviation of 10.7
kg N2O-N ha-1 yr-1,
producing a relative uncertainty of 52%. At point scale, the relative
error was on average 78%, indicating that upscaling decreases
uncertainty. Soil inputs and denitrification and nitrification
inputs were the main sources of uncertainty in N2O
emission at point scale. At landscape scale, uncertainty in soil
inputs averaged out and uncertainty in denitrification and nitrification
inputs was the dominant source of uncertainty. This was partly
because inputs were assumed constant across areas with the same
soil type and land use, which is probably not very realistic.
Experiments at landscape scale are needed to assess the spatial
variability of these fractions and analyze how a more realistic
representation influences the uncertainty budget at landscape
scale. This research confirms that results from uncertainty analyses
are often scale dependent and that results for one scale cannot
directly be extrapolated to other scales.
Keywords: Uncertainty propagation analysis; N2O
emission; Landscape scale; Fen meadow landscape; Aggregation;
model input uncertainty』
1. Introduction
2. Materials and methods
2.1. The model INITITOR
2.2. The Dutch western fen meadow landscape
2.3. Selection of model inputs for uncertainty quantification
(Quickscan)
2.4. Input uncertainty quantification of selected model inputs
2.4.1. Numerical constants
2.4.2. Spatially variable continuous model inputs
2.4.3. Spatially variable categorical model inputs
2.5. Assessment of uncertainty at point and landscape scale
2.6. Assessment of the main sources of uncertainty
3. Results
3.1. Selection of model inputs for uncertainty quantification
3.2. Uncertainty quantification of selected model inputs
3.3. Uncertainty in N2O emissions at point and landscape scale
3.4. Main sources of uncertainty
4. Discussion
4.1. Input uncertainty quantification
4.2. Uncertainty of N2O emissions at point
scale
4.3. Uncertainty of N2O emission at landscape
scale
5. Conclusions
Acknowledgements
References