Native seed, soil and atmosphere respond to boreal forest topsoil (LFH) storage

Abstract

During mining topsoil is salvaged and stockpiled until ready for reclamation, stockpiling can have detrimental effects on seed viability and soil quality. Research has assessed effects of salvage and placement depth of forest topsoil on plant community establishment, with little work on effects of storage, particularly in the boreal forest. Our research assessed boreal forest topsoil storage methods to determine effects on soil chemical and physical properties, native seed viability and germination and rhizome viability and emergence. Factors were topsoil stockpiling length, stockpile size, season of construction and soil texture. Four replicates of large and small stockpiles were constructed in the mineable oil sands, in northeastern Alberta. During construction seeds and rhizomes from a variety of native boreal plant species were buried within large (0.05, 1.0, 2.0, 4.0, 6.0 m) and small (0.05, 1.0, 3.0 m) stockpiles. Soil gas probes were installed at similar depths as seed and rhizomes were placed. Seeds and rhizomes were extracted eight months and sixteen months after construction; during that time soil samples were collected for various chemical analyses. Irrespective of stockpile size, the majority of species seeds and rhizomes buried below 1 m lost viability and did not germinate after eight months. Anaerobic soil conditions developed soon after construction and persisted at depths below 1.0 m in large stockpiles, and over time anaerobic conditions developed in smaller stockpiles. Only seeds of Geranium bicknellii and Dracocephalum parviflorum had a high survival rate in stockpiles; both species have hard seed coats and are physically dormant. Various soil nutrients increased in concentrations in their soluble forms after stockpiling. Direct placement of topsoil is a preferred soil handling technique; however, if topsoil has to be stockpiled increasing the surface area of stockpiles will help preserve some seed and rhizome viability.

Early ecosystem establishment using forest floor and peat cover soils in oil sands reclamation

“…Stockpiling may have a direct impact on soil propagule vitality (Mackenzie et al 2019; Dhar et al 2019; Shaughnessy et al 2022), as most of our cover soils were stockpiled 3 to 6 months except Sites 2 and 4 where stockpiling times for PMM were not well documented. Mackenzie et al (2019) found stockpiling can lead to significant losses in viability within 8 months.…”

“…Reclamation outcomes depend on multiple factors including biotic and abiotic conditions and time since reclamation (MacKenzie et al 2012; Chen et al 2017; Dhar et al 2018; Mackenzie et al 2019). Abiotic site conditions such as cover soil type can play significant roles in plant community development (Chen et al 2017; Mackenzie et al 2019). In contrast, biotic factors such as microbial activity help soil formation and nutrient cycling (MacKenzie et al 2012; Macdonald et al 2015).…”

“…Considerable reclamation research has been conducted in the oil sands, focusing on overstory and understory development, stockpiling, cover soil types and depth, soils, and microbial communities (Naeth et al 2013; Macdonald et al 2015; Pinno and Hawkes 2015; Chen et al 2017; Mackenzie et al 2019; Dhar et al 2019, 2020a). However, none of this research has explicitly investigated species-level interaction with different cover soil types, placement depths, and time since reclamation during early plant community development in boreal forests.…”

Impact of soil stockpiling on ericoid mycorrhizal colonization and growth of velvetleaf blueberry (Vaccinium myrtilloides) and Labrador tea (Ledum groenlandicum)

“…Physical and chemical properties of stockpiled soil change during topsoil stripping, stockpiling, and storage. Stockpiling can increase soil bulk density, decrease microbial activity, reduce nutrient cycling, increase volumetric water content, and decrease seed viability (Strohmayer 1999; MacKenzie 2013; Mackenzie & Naeth 2019). Anaerobic conditions increase with the increasing depth of piles over time and are more severe in fine‐textured soils (Abdul‐Kareem & McRae 1984).…”

A comparison between reclamation stockpile and boreal forest seed banks and plant communities

“…Stockpile seed bank communities can be evaluated in different ways. For example, there are studies that quantify the decline in seed viability over time by burying seeds (Mackenzie & Naeth 2019) and other studies that compare the seed bank present in stockpiles at different depths (Iverson & Wali 1982; Dickie et al 1988; Golos & Dixon 2014). However, few studies have looked at the seed bank present in multiple stockpiles at once and compared those communities to the aboveground plant communities and nearby undisturbed areas.…”