Modeling Soil Organic Carbon Change across Australian Wheat Growing Areas, 1960–2010

Guocheng Wang,Enli Wang,Yao Huang,Wen Zhang,Yongqiang Yu,Ben Bond-Lamberty

doi:10.1371/journal.pone.0063324

Abstract

Soil organic carbon (SOC) dynamics in Australian wheat-growing areas were simulated from 1960 to 2010 using Agro-C, a calibrated and validated biogeophysical model. Previously published data from field measurements were used to parameterize the Agro-C model. Model simulations show a decreasing trend in SOC over the last 50 years, mainly attributable to relatively low organic carbon (C) inputs. The rate of decrease in SOC tended to slow in the last two decades due primarily to an increase in wheat yields, which resulted in an increase in C input. Overall, we estimate that Australian wheat-growing areas, covering an area of 15.09 million hectares (Mha), lost 156 (86–222, 95% confidence interval) Tg C in the topsoil (to 30 cm depth) from 1960 to 2010. Approximately 80% of the SOC loss occurred in the period between the 1960s and the 1980s. Spatially, the SOC loss in areas with relatively high temperature and low precipitation, such as Queensland, the northern part of New South Wales and Western Australia, was more significant than that in other areas. We suggest that the loss of SOC could be halted, or even reversed, with an additional input of organic C into the soil at a minimum rate of 0.4 Mg ha–1 yr–1.

Highlights

Cultivation of natural soils generally leads to a reduction of soil organic carbon (SOC) because cultivation enhances the rates of carbon (C) mineralization, reduces the amount of biomass C returned to the soil, and accelerates SOC erosion and leaching processes [1,2]
2.2 Estimated Changes in SOC from 1960 to 2010 Our Agro-C simulation results suggest that SOC in Australian wheat-growing areas has decreased over the last five decades (Figure 3)
Our simulation results showed that the Australian wheat-growing areas have in general experienced SOC loss from 1960 to 2010, the rate of SOC loss has declined over time (Figure 3 and Table3)

Summary

Introduction

Cultivation of natural soils generally leads to a reduction of soil organic carbon (SOC) because cultivation enhances the rates of carbon (C) mineralization, reduces the amount of biomass C returned to the soil, and accelerates SOC erosion and leaching processes [1,2]. Australian cropland has experienced tremendous loss of SOC since the European settlement began, due largely to the loss of above-ground biomass C after the conversion of native land for agriculture [4]. Based on a regional meta-analysis, Dalal and Chan [6] suggested that, in the Australian wheat belt, soil would sequester a large amount of atmospheric CO2 20 years after the adoption of improved management techniques. Cropland SOC dynamics depend on a balance between C production and decomposition and are regulated by management and by highly variable climate and soil conditions [5,7]. Assessing regional SOC dynamics is difficult, in Australian croplands, due to the lack of detailed climate, soil, and management-related information

Methods

Results

Conclusion