Frequency of 10 cm soil temperatures reaching −6.0°C or colder for varied miscanthus residue thicknesses.

<p>Fraction of total years during the 1978–2007 time period that simulated annual 10 cm soil temperatures were at or below a −6.0°C threshold (based on a 3-day running mean) for (a) MAIZE+TILL (bare soil), (b) MISCAN+R_{1 cm}, (c) MISCAN+R_{2.5 cm}, and (d) MISCAN+R_{5 cm} simulations.</p

Simulated soil temperature trends across the Midwest US.

<p>(a) Total change (from linear regression) in annual average 10 cm soil temperatures for 1948–2007 for the MAIZE+TILL (bare soil) simulation; (b) total change (from linear regression) in annual extreme minimum 10 cm soil temperature for the MAIZE+TILL (bare soil) simulation from 1948–2007; (c) total change (from linear regression) in annual extreme minimum 10 cm soil temperature for the MAIZE+TILL (bare soil) simulation from 1981–2007. Regions bounded by solid white lines indicate trends with P<0.05.</p

Impacts of miscanthus residue thickness on annual average extreme 10 cm soil temperatures.

<p>Average annual (1978–2007) extreme minimum 10 cm soil temperature changes at eight locations in the Midwest, based on a 3-day running mean, for MISCAN+R simulations with varied residue thicknesses relative to the MAIZE+TILL (bare soil) simulation.</p

Impacts of soil surface residue management on annual average extreme minimum 10 cm soil temperatures.

<p>Average annual (1978–2007) extreme minimum 10 cm soil temperatures (based on 3-day running mean) for (a) MAIZE+TILL (bare soil post harvest), (b) MAIZE+NOTILL, (c) MISCAN+R_{1 cm}, (d) MISCAN+R_{2.5 cm}, and (e) MISCAN+R_{5 cm} simulations. The position of the 0.0°C, −3.5°C, −6.0°C, and −8.0°C 10 cm soil temperature isopleths are highlighted by labels on solid black lines; (f) differences in average annual extreme minimum 10 cm soil temperatures for MISCAN+R_{5 cm} – MAIZE+NOTILL (Fig. 6e–Fig. 6b results).</p

Comparison of observed and simulated annual extreme minimum 10 cm soil temperatures.

<p>(a) Agro-IBIS average annual extreme minimum 10 cm soil temperature (based on 3-day running mean temperatures) compared with observations from 125 observation sites (SI, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068847#pone.0068847.s001" target="_blank">Table S1</a>) from the Midwest USA for original model values (open circles and dotted regression line), and statistically adjusted model values (filled circles and dashed regression line); (b) Agro-IBIS simulated frequency of occurrence of 10 cm soil temperatures (3-day running mean) reaching −3.5°C and (c) −6.0°C, respectively, compared with results from 125 observation sites in the Midwest USA. In these comparisons, Agro-IBIS was only simulated for a period from the beginning year that data was available for each observation station through 2007, which denotes the last year that gridded daily climate data was available.</p

Observed versus simulated interannual variability of mean Nov-Apr snow depth.

<p>Comparison of observed versus Agro-IBIS model simulated mean Nov-Apr snow depth for each year from 1963–1995 in (a) northern (43.5° to 47.5°N lat; −94.0 and −83.0°W lon) and (b) southern (39.5° to 43.49°N lat; −94.0 and −83.0°W lon) areas where observation stations were located. Previous IBIS-2 model results (Lenters et al., 2000) are plotted for comparison. Linear regression fits between observations and model results are denoted by the following lines: thin black (IBIS-2); gray solid (MAIZE+TILL); black dashed (POTVEG).</p

Comparison of observed and simulated soil temperatures in Illinois.

<p>(a) Comparison of 3-day running mean 10 cm soil temperatures for Agro-IBIS model simulations of miscanthus with no residue layer with observed values at the University of Illinois Energy Farm from 2009 to 2011. Observed values are the daily mean (n = 1 to 5) of observation for the miscanthus plots, n was less than five for periods when sensors were damaged, with n at least 3 for 80% of the days. (b) Comparison of monthly mean 10 cm soil temperatures for the same site and simulation. Data points are the mean (n = 3) of the 2009–20011 monthly values, error bars are ±1 S.E. for both simulated and observed values.</p

Comparison of observed and simulated monthly mean snow depths.

<p>Long-term monthly mean snow depths (1963–1995) for 34 Midwest station observations compared to previous IBIS and current Agro-IBIS simulations in (a) northern (43.5° to 47.5°N lat; −94.0 and −83.0°W lon) and (b) southern (39.5° to 43.49°N lat; −94.0 and −83.0°W lon) areas where observation stations were located. Observations and IBIS-2 results were obtained directly from previous statistical analyses for comparison here (Lenters et al., 2000).</p

Description of Agro-IBIS model runs.

<p>Description of Agro-IBIS model runs.</p

Frequency of 10 cm soil temperatures reaching −3.5°C or colder for varied miscanthus residue thicknesses.

<p>Fraction of total years during the 1978–2007 time period that simulated annual 10 cm soil temperatures were at or below a −3.5°C threshold (based on a 3-day running mean) for (a) MAIZE+TILL (bare soil), (b) MISCAN+R_{1 cm}, (c) MISCAN+R_{2.5 cm}, and (d) MISCAN+R_{5 cm} simulations.</p