Impact of agriculture and forestry on landscapescale soil organic carbon storage in Saskatchewan
van Kessel, C.
The 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.
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