The Influence of Shallow Organic Zones On Moisture Retention In Coarse Soils of the Alberta Oil Sands Region.

Landscapes disturbed by mining in the Alberta Oil Sands require reconstruction to produce viable self sustaining ecosystems that mimic the functioning of a pre-disturbed soil.  Successful reclamation relies on the preliminary measurement of field capacity (FC) in soils that support target vegetation and soils that will be salvaged for use in cover systems.  The objective of this research is to examine the influence of the surface organically enriched zones on the field capacity of coarse textured soils.  Undisturbed soil profiles that support a and b ecosite vegetation and 4 year old clear cut sites were examined in this study.  Double-ring infiltration experiments with real time monitoring were conducted to monitor drainage and FC for each profile.  A Sentek EnviroSCAN and Diviner 2000 were used to monitor the moisture content of the profile over 7 days to a depth of 70 cm and a series of vertically installed TDR probes were used to monitor moisture content to a depth of 10 and 15 cm.  The sites were excavated, classified and intact and bulk samples were taken for laboratory analysis.  The depth of the organically enriched  layers ranged from 2-3cm, 1-2 cm, and 1-7 cm for the LFH, Ah, and Ae horizons respectively.  The measured FC in the organically enriched layers of the profile exceeded 200% of that in the underlying coarse soils.  After 7 days of drainage, the water storage in the upper 10 cm accounted for up to 90% of the total storage to a depth of 15cm.  This work highlights the importance of placing shallow organically enriched surface materials over coarse materials to replicate natural field conditions in reclamation covers.