Plant recolonization of reclamation areas from patches of salvaged forest floor material

Abstract

Question: Understorey development is a great challenge in the restoration of many forest sites, particularly when sources of vegetation propagules are scarce. Can placement of propagule-rich soil patches within reclaimed landscapes otherwise covered with propagule-poor material promote the dispersal of vegetation from the patches into the surrounding areas? Location: Large reclamation site in the Canadian (Alberta) boreal forest.Method: Patches of propagule-rich forest floor material were placed within a matrix of propagule-poor peat material. Vegetation assessments (cover estimates, seed rain) were done surrounding these patches in the third and fourth growing seasons. Results:There was significant egress of species from the patches into the peat after four growing seasons, and overall species associated with the patches had higher cover in the peat than species that were associated with the peat itself. While winddispersed herbaceous species from the patches were found at the leading edge of the egressing community, most species used vegetative propagation, resulting in short egress distances. Several patch-associated species were found in seed rain collected on the peat areas but were not observed in this material, suggesting seedbed limitations.Conclusion: Despite the relatively short distance of egress, this experiment suggests that placement of propagule-rich soil material within reclaimed landscapes will promote egress into adjacent propagule-poor soil material. K E Y W O R D Sapplied nucleation, boreal forest, plant community, plant egress, propagule bank, reclamation, restoration ecology, soil placement, soil salvage, understorey

Forest topsoil salvage and placement depth affects oil sands reclamation in the boreal forest

“…Direct placed forest topsoil derived from coarse texture soil provides a valuable source of propagules and soil that supports boreal forest plant community development. Our results align with other studies that show forest topsoil having greater species richness, diversity and desired forest species cover and density than peat-mineral substrate [ 5 , 7 ]. Forest topsoil provided tree and shrub densities greater then the common planting prescription of 2500 woody stems per ha [ 38 ].…”

“…Salvaging, which in this context refers to the careful removal and preservation of boreal forest topsoil (forest floor material mixed with upper soil mineral horizons), provides industry with a means to use a local diverse seed source and fertile surface soil to meet reclamation requirements [ 4 – 6 ]. Forest floor materials and topsoil are important sources of forest understory propagules for upland forest reclamation [ 5 , 7 ]. Direct placement of forest topsoil is considered a best practice in the oil sands [ 3 , 8 , 9 ].…”

Dominant drivers of plant community assembly vary by soil type and time in reclaimed forests

“…Native forbs generally expanded at a slow rate into the PMM with the average dispersal up to 2 m after 5 years. Jones and Landhäusser (2018) found similar rates of vegetative expansion from FFMM into PMM from an average of\ 2 m to a maximum of 4 m. The main species showing vegetative expansion used stolons (e.g. Fragaria virginiana).…”

“…The reclamation site in our study is located near a river with remnant forests on two sides, likely leading to a continual dispersal of late-successional species. In contrast, Jones and Landhäusser (2018) found limited evidence of biotic dispersal on a similarly aged oil sands reclamation site, though their site was isolated in the center of a large mine with no intact forest for several kilometers, which may have limited availability for biotic dispersal. By comparing both studies that are similar in age and soil configuration technique, we can see the importance of distance to remnant forests when using a passive reclamation technique to increase the ability of biotic movement and seed rain through the reclamation site.…”

“…Incoming seed rain species in this region is generally from wind dispersing trees or early successional species that have a continual input of seed into an area (Corbin et al 2016;Gallagher et al 2011). Species using vegetative reproductive structures have a relatively slow rate of expansion which is one of the downfalls of this reproductive method (Jones and Landhäusser 2018;Robinson and Handel 2000). However, many of the early successional species that use wind or gravity dispersal are also rhizomatous, such as Sonchus sp., Chamerion sp., and Calamagrostis canadensis.…”