Examining the Impact of Thermal Adaptation of Soil Microorganisms and Crop System on Climate Change’s Effects on Organic Matter in Tropical Soil

As populations in tropical regions increase and more food is needed, crop yields are decreasing. Increasing the amount of cleared land for crop production has negative impacts on soil quality and crop production as well as increasing the amount of greenhouse gas emissions.  Tropical crops are currently at optimal growth temperatures, and therefore decline in yields are expected with even a small increase in temperature.  Sierra et al. (2010) hypothesize that climate change in tropics affects soil organic matter<!–[if supportFields]> XE “soil organic matter (SOM)” <![endif]–><!–[if supportFields]><![endif]–> (SOM) content and soil fertility through the direct effect on the rate of microbial processes and by the indirect effect on crop growth.  The authors predict that temperature and rainfall will substantially increase, and affect maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–> crops significantly more than bananas.  Maize yields were found to decrease by 1% under the adaptation scenario studied, where no difference was found in banana yields. Decreasing rates of SOM and C mineralization were predicted for maize, and again no differences were found for banana crops. —Whitney Dawson
Sierra, J., Brisson, N<!–[if supportFields]>XE “nitrogen, N”<![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–>., Ripoche, D., Deque, M., 2010. Modelling the impact of thermal adaptation of soil microorganisms and crop system on the dynamics of organic matter in a tropical soil under a climate change scenario.  El Selvier 221, 2850–2858.ces 2, 29–35.

Sierra et al. model the thermal adaptation, the shift in the intrinsic response of a biological soil process to temperature due to soil warming, of soil microorganisms in response to climate change.  This process is then introduced in a crop system model, already calibrated to incorporate SOM<!–[if supportFields]> XE “soil organic matter (SOM)” <![endif]–><!–[if supportFields]><![endif]–> dynamics under tropical conditions. The study aims to see how climate change impacts SOM in agricultural tropical soil, and to evaluate the importance of microbial adaptation in SOM dynamics in crops.  The two crop systems compared are maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–> and banana, both currently of great use in the tropics.   Models for climate simulation and crop-soil relationships were borrowed from outside sources, selected for their previous calibration to the crops analyzed in this study, and accounting for irrigation effects.  The climate is simulated from 1950 to 2099 for tropical humid conditions.
The model predicts a 3.4 °C increase for air temperature and 1100 mm per year increase for rainfall due to an increase in of 375 ppm for atmospheric carbon dioxide concentration in the 2090–2099 decade in comparison to the 1950–1959 decade.   By controlling the change in C input, soil temperature, and soil moisture, the crops affects the response of SOM<!–[if supportFields]> XE “soil organic matter (SOM)” <![endif]–><!–[if supportFields]><![endif]–> to climate change. Little variation is seen in SOM until 2020, followed by a faster decrease for maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–> than banana. Banana had positive effects on growth from an increase in temperature, and relatively stable C inputs.  Maize growth and cycle length drastically decreased from increased temperature.  The difference in results between crops is due to the higher water consumption of banana than maize, affecting the soil temperature as well.  SOM is never stabilized in the period studied since C mineralization is always greater than C input.  The authors conclude from the models that microbial thermal adaptation does not fundamentally change the temporal pattern of SOM dynamics, but slightly modifies it.
Debate over climate change impacts occurs as a result of the difficulties is examining the relationship between soil, plant, and weather variables affecting SOM<!–[if supportFields]> XE “soil organic matter (SOM)” <![endif]–><!–[if supportFields]><![endif]–> dynamics under the scenario of climate change.  In the studied period, the factors controlling SOM decrease varied over time and with the crop system, not with a large amount of consistency.  It is suggested that progressive thermal adaptation of soil microorganisms can play an important role in mitigating climate change. 

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