An evaluation of the century model to predict soil organic carbon: examples from Costa Rica and Canada |
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| Authors: | Maren Oelbermann R P Voroney |
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| Institution: | (1) Department of Environment and Resource Studies, Faculty of Environment, University of Waterloo, Waterloo, ON, N2L 3G1, Canada;(2) School of Environmental Sciences, Ontario Agricultural College, University of Guelph, Guelph, ON, N1G 2W1, Canada |
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| Abstract: | Greater organic matter inputs in agroforestry systems contribute to the long-term storage of carbon (C) in the soil, and the
use of simulation models provides an opportunity to evaluate the dynamics of the long-term trends of soil organic carbon (SOC)
stocks in these systems. The objective of this study was to apply the Century model to evaluate the long-term effect of agroforestry
alley crop and sole crop land management practices on SOC stocks and soil C fractions. This study also evaluated the accuracy
between measured field data obtained from a 19-year old tropical (TROP) and 13-year old temperate (TMPRT) alley crop and their
respective sole cropping systems and simulated values of SOC. Results showed that upon initiation of the TROP and TMPRT alley
cropping systems, levels of SOC increased steadily over a ~100 year period. However, the sole cropping systems in both tropical
and temperate biomes showed a decline in SOC. The active and passive C fractions increased in the TROP agroforestry system,
however, in the TMPRT agroforestry system the active and slow fractions increased. The input of organic matter in the TROP
and TMPRT agroforestry systems were 83 and 34% greater, respectively, compared to the sole crops, which likely contributed
to the increased SOC stock and the C fractions in the alley crops over the 100 year period. Century accurately evaluated levels
of SOC in the TROP (r
2 = 0.94; RMSE = 226 g m−2) and TMPRT (r
2 = 0.94; RMSE = 261 g m−2) alley crops, and in the TROP (r
2 = 0.82; RMSE = 101 g m−2) and TMPRT (r
2 = 0.83; RMSE = 64 g m−2) sole crops. Century underestimated simulated values in the alley cropping systems compared to measured values due to the
inability of the model to account for changes in soil bulk density with increasing organic matter inputs with tree age from
prunings or litterfall. |
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