Uncertainty in Ecohydrological Modeling in an Arid Region Determined with Bayesian Methods

<div><p>In arid regions, water resources are a key forcing factor in ecosystem circulation, and soil moisture is the critical link that constrains plant and animal life on the soil surface and underground. Simulation of soil moisture in arid ecosystems is inherently difficult due to high variability. We assessed the applicability of the process-oriented CoupModel for forecasting of soil water relations in arid regions. We used vertical soil moisture profiling for model calibration. We determined that model-structural uncertainty constituted the largest error; the model did not capture the extremes of low soil moisture in the desert-oasis ecotone (DOE), particularly below 40 cm soil depth. Our results showed that total uncertainty in soil moisture prediction was improved when input and output data, parameter value array, and structure errors were characterized explicitly. Bayesian analysis was applied with prior information to reduce uncertainty. The need to provide independent descriptions of uncertainty analysis (UA) in the input and output data was demonstrated. Application of soil moisture simulation in arid regions will be useful for dune-stabilization and revegetation efforts in the DOE.</p></div

Characteristics of <i>Nitraria sphaerocarpa</i> investigated between 2006 and 2010.

<p>Characteristics of <i>Nitraria sphaerocarpa</i> investigated between 2006 and 2010.</p

Flow chart of the evolving array of the parameters in Bayesian uncertainty estimation.

<p>Flow chart of the evolving array of the parameters in Bayesian uncertainty estimation.</p

Frequency posterior probability distributions of partial parameters generated with the Bayesian approach, using 5,000 samples.

<p>Note: <i>Lambda(8)</i> was pore size distribution index at 100 cm soil depth. <i>Air Entry(1)</i> and <i>Air Entry(7)</i> were the air entry pressure at 10 and at 80 cm soil depth, respectively. <i>MinimumCondValue</i> was the minimum hydraulic conductivity in the hydraulic conductivity function; <i>Saturation(1)</i> and <i>Saturation(2)</i> denoted water content at saturation in the 10 and 20 cm soil layer, respectively. <i>Wilting Point(3)</i> and <i>Wilting Point(5)</i> meant water content at wilting point in the 30 and in the 50 cm soil layer, respectively. <i>Total Conductivity(1)</i> and <i>Total Conductivity(2)</i> implied water content at saturation in the 10 and 20 cm soil layers, respectively. <i>Residual Water(5)</i> and <i>Residual Water(7)</i> were residual soil moisture at 50, and 70 cm soil depth, respectively. Details and data used are described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151283#pone.0151283.s004" target="_blank">S4 File</a>.</p

Soil water content dynamics and the corresponding precipitation processes between 2009 and 2013.

<p>Details and data used are described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151283#pone.0151283.s001" target="_blank">S1 File</a>.</p

Statistical results of soil moisture and temperature simulated for different soil layers (before uncertainty analysis).

<p>Statistical results of soil moisture and temperature simulated for different soil layers (before uncertainty analysis).</p

Correlation between probe and weighted values derived from measured probe and in situ weighting method.

<p>Details and data used are described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151283#pone.0151283.s004" target="_blank">S4 File</a>.</p

Locations of the dune study site, Heihe River, and the Linze National Station.

<p>Locations of the dune study site, Heihe River, and the Linze National Station.</p

Statistical results of model calibration and validation after uncertainties analyzing.

<p>Statistical results of model calibration and validation after uncertainties analyzing.</p

Corrected results of precipitation data.

<p>Blue bars denote inferred true precipitation (mm), and the red error bars indicate standard deviation between the records and corrected precipitation. Details and data used can be found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151283#pone.0151283.s001" target="_blank">S1 File</a>.</p