Modeling Soil Organic Carbon in a Semiarid Region of Kazakhstan Using EPIC

Authors: CAUSARANO, HECTOR - Universidad Nacional De Asuncion; Doraiswamy, Paul; McCarty, Gregory; MURATOVA, NADIYA - Space Research Institute; PACHIKIN, KONSTANTIN - Kazakhstan Research Center; AKHMEDOV, BAKHYT - Science Systems, Inc; WILLIAMS, JIMMY - Blackland Research And Extension Center

Submitted to: Agronomy for Sustainable Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2010
Publication Date: 8/9/2010
Citation: Causarano, H., Doraiswamy, P.C., McCarty, G.W., Muratova, N., Pachikin, K., Akhmedov, B., Williams, J.R. 2010. Modeling soil organic carbon in a semiarid region of Kazakhstan using EPIC. Agronomy for Sustainable Development. http://dx.doi.org/10.1051/agro/2010028.

Interpretive Summary: Intensive cultivation, summer fallowing, excessive grazing in semiarid regions in central Asia has resulted in degradation of rangelands and reported to caused depletion of soil organic carbon (SOC) and increased soil erosion. A limitation for determining the impacts of land use changes on SOC, in the steppe region of central Asia, is the lack of information on SOC stocks under the predominant land uses. A study was conducted as part of a World Bank project to determine current and potential soil carbon sequestration for a 13800 km2 semi-arid area in Shetsky Rayon located central east Kazakhstan. A baseline soil carbon map was developed from satellite imagery-based landuse classification and digitized soil properties. The Environmental Policy Integrated Climate (EPIC) model was used to study long-term impacts of land use changes and soil management on SOC to a depth of 50 cm during 1955–2030. The primary land uses were: native rangeland vegetation, wheat, wheatgrass, and abandoned croplands. Combining land use classification and soil maps with EPIC, proved valid for studying impacts of land use changes and management practices on SOC. If land use remained as it is now, total stock of SOC would decrease equivalent to a loss of 723 kg C ha-1 yr-1. If best management practices are implemented, resulting in reallocation of land use according to the land capability with abandoned croplands being converted to reduced-tillage wheat or wheatgrass, total stock of SOC would increase equivalent to 4700 kg C ha-1 yr-1. The conclusion was that by selecting appropriate management for an optimum combination of landuse, soils, and crop cover for a particular climatic zone, an area which was a net source for atmospheric CO2 can be potentially transformed to a net sink in this region.

Technical Abstract: Inappropriate land use and soil mismanagement produced wide-scale soil and environmental degradation to the short-grass steppe ecosystem in the semiarid region of Kazakhstan. We used the Environmental Policy Integrated Climate (EPIC) model to study long-term impacts of land use changes and soil management on soil organic carbon (SOC) to a depth of 50 cm during 1955–2030, in a 13800 km2 area in central east Kazakhstan containing degraded agricultural lands. Simulated land uses were: native rangeland vegetation, wheat (Triticum aestivum L.), wheatgrass (Agropyron cristatum L.), and abandoned croplands. The EPIC model was initialized with soil properties obtained from a soil map produced for the study area. Statistics on weather variables were obtained from five meteorological stations and from the Agricultural Meteorology Modeling System of the US Air Force Weather Agency (AGRMET). Data on crop management, fertilizer application and tillage practices were gathered from expert knowledge. Simulations were performed for each polygon on a land use classification map of the study area, resulting in 4661 simulations being used to scale up results. Simulated SOC explained 50% of the variation in measured SOC. Of the 1.38 million hectares in the study area, 78% were under native vegetation, 3% cultivated to wheat, 8% on wheatgrass, and 11% were abandoned croplands in 2005. If land use remained constant, total stock of SOC would decrease from 87.6 Tg in 2005 to 86.6 Tg by 2030, equivalent to an annual loss of 723 kg C ha-1. However, if best management practices are implemented, resulting in reallocation of land use according to the land capability with abandoned croplands being converted to reduced-tillage wheat or wheatgrass, total stock of SOC would increase to 94.1 Tg by 2030, equivalent to 4700 kg C ha-1 yr-1. Overall, combining land use classification and soil maps with EPIC, proved valid for studying impacts of land use changes and management practices on SOC. With the available data, EPIC produced relatively accurate results but more data on spatial and temporal variation in SOC are needed to improve model calibration and validation.