Impact of agriculture and forestry on landscapescale soil organic carbon storage in Saskatchewan

Non-Peer ReviewedThe development of sound management approaches to reduce soil organic carbon (SOC) losses from soils presuppose that we thoroughly understand the sources of these losses. We use a landscape-scale research design to estimate the magnitude of carbon losses due to human activity by comparing SOC storage in undisturbed landscapes with comparable landscapes disturbed by clear-cutting of forests in the Mixedwood/Gray Luvisolic zone of central Saskatchewan and by agricultural activity in the Black soil zone. A slight drop in median levels of soil organic carbon storage in the upper 45 cm of the soil (from 56.8 Mg ha-1 in mature mixedwood sites to 52.7 Mg ha-1 in clear-cut landscapes) occurs due to clear-cutting of the Mixedwood forest. The dominant soil type in these landscapes, Gray Luvisolic soils, experience no significant change in SOC storage; however significant losses occur from Brunisolic (29% loss) and Gleysolic (32% loss) inclusions in these landscapes. Changes in SOC from Black soil zone landscapes are strongly related to texture: sandy glacio-fluvial landscapes experience slight gains of SOC (from 54.1 to 60.1 Mg ha-l); silt and clay glacio-lacustrine landscapes experience a 15.3% decrease in SOC (from 145.2 to 122.9 Mg ha-l); and loamy glacial till landscapes undergo a major decrease in SOC storage (from 119.6 to 75.2 Mg ha-l). Our results indicate that attempts to mitigate SOC losses from soils in Saskatchewan should concentrate on agricultural activities, especially in glacial till landscapes