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

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

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

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

Plant residue biophysical values used to modify Agro-IBIS to simulate the effects of crop residue on soil surface energy balance and heat transfer.

<p>Plant residue biophysical values used to modify Agro-IBIS to simulate the effects of crop residue on soil surface energy balance and heat transfer.</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

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

Comparison of observed and simulated soil temperatures in Iowa and Wisconsin.

<p>(a) Comparison of monthly average 10 cm soil temperatures for three Agro-IBIS model simulations with observational station data from Hu and Feng (2003) averaged over the state of Iowa for 1982–2002. Error bars are ±1 S.E. for both simulated and observed values. (b) Comparison of monthly average 10 cm soil temperatures for three Agro-IBIS models simulations compared with observational data at the University of Wisconsin-Madison Arlington Agricultural Research Station in tilled maize and switchgrass study plots for July 2009- June 2012. Observed data (maize and switchgrass) represent the monthly mean among 3 replicate plots (n = 3). Long-term averages (1988–2011) of monthly mean 10 cm soil temperature collected at the UW-Madison Automated Weather Observing Network (AWON) site at Arlington are plotted for comparison. Error bars are ±1 S.E. for all simulated and observed values.</p

Soil temperature differences between different residue layer thicknesses.

<p>Average annual (1978–2007) extreme minimum 10 cm soil temperature differences, based on a 3-day running mean, for the following paired simulations: (a) MISCAN+R_{1 cm} minus MAIZE+TILL (bare soil post harvest), (b) MISCAN+R_{2.5 cm} minus MAIZE+TILL, (c) MISCAN+R_{5 cm} minus MAIZE+TILL.</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