Modelling climate, CO2 and management impacts on soil carbon in semi-arid agroecosystems

Abstract

In agroecosystems, there is likely to be a strong interaction between global change and management that will determine whether soil will be a source or sink for atmospheric C. We conducted a simulation study of changes in soil C as a function of climate and CO2 change, for a suite of different management systems, at four locations representing a climate sequence in the central Great Plains of the US.Climate, CO2 and management interactions were analyzed for three agroecosystems: a conventional winter wheat-summer fallow rotation, a wheat-corn-fallow rotation and continuous cropping with wheat. Model analyses included soil C responses to changes in the amount and distribution of precipitation and responses to changes in temperature, precipitation and CO2 as projected by a general circulation model for a 2 × CO2 scenario.Overall, differences between management systems at all the sites were greater than those induced by perturbations of climate and/or CO2. Crop residue production was increased by CO2 enrichment and by a changed climate. Where the frequency of summer fallowing was reduced (wheat-corn-fallow) or eliminated (continuous wheat), soil C increased under all conditions, particularly with increased (640 #L L -l ) CO2. For wheat-fallow management, the model predicted declines in soil C under both ambient conditions and with climate change alone. Increased CO2 with wheat-fallow management yielded small gains in soil C at three of the sites and reduced losses at the Iourth site.Our results illustrate the importance of considering the role of management in determining potential responses of agroecosystems to global change. Changes in climate will determine changes in management as farmers strive to maximize profitability. Therefore, changes in soil C may be a complex function of climate driving management and management driving soil C levels and not be a simple direct effect of either climate or management.

Spatial and temporal deployment of crop roots in CO2‐enriched environments

“…In fact, the magnitude of the impact of agricultural management practices on fine-root production and mortality, and the resultant transfer of C to soil, might overshadow any effects of elevated [CO # ] on these processes (Canadell et al, 1996). Using the CENTURY model to determine the interactions of temperature, precipitation, elevated [CO # ], and management practices, Paustian et al (1996) found that agricultural management practices were more important than climate change and elevated [CO # ] in controlling amounts of soil C. Therefore, interactive effects of agricultural management practices with increasing global [CO # ] must represent the main thrust of research concerning the impact of future global change on agricultural.…”

The effects of elevated [CO2] on plant-soil carbon below-ground: A summary and synthesis

“…Paustian et al (1996) used the CENTURY model to evaluate the interactions between climate change (including temperature and precipitation), CO2 fertilization and management in influencing soil carbon levels in three agroecosystems: a conventional winter wheatsummer fallow rotation, a wheat-corn-fallow rotation, and continuous cropping with wheat. The model analyses showed that management practice was more important than any aspect of climate change or [CO2] in controlling soil carbon levels.…”

Potential soil carbon sequestration in a semiarid Mediterranean agroecosystem under climate change: Quantifying management and climate effects

“…Previous model analyses suggest that climate impacts on both SOM turnover and crop growth may be modified by management practices (e.g. Paustian et al 1996). For example, Lugato and Berti (2008), in northeast Italy, observed significant differences in SOC sequestration under climate change depending on the management applied.…”