Ecohydrological functioning of an upland undergoing reclamation on post‐mining landscape of the Athabasca oil sands region, Canada

Abstract

Ecohydrological functioning of natural Boreal forest in Canada's Boreal Plains is a product of interactions between soil hydrophysical characteristics and hydrogeochemical processes. These interactions create a moisture–nutrient gradient within the surface soils, increasing along low‐relief transitions from upland to riparian zone, and in turn influence the distribution of vegetation communities. It is not yet known if/when analogous ecohydrological functions can be achieved in constructed uplands following industrial disturbance, such as that following oil sands development. Hence, to assess this, we studied interactions between hydrogeochemical processes and vegetation colonization in a constructed upland relative to hydrophysical properties of 2 reclamation cover substrates during a typical continental climate's growing season. Our results indicated that in 3 years of postconstruction, the establishment of a moisture–nutrient gradient that supports vegetation colonization along slope positions was still limited by heterogeneity of cover substrates. Portions of the upland under peat–mineral mix were characterized by lower nutrient availability, high moisture content, and establishment of planted shrubs and trees. In contrast, forest floor materials plots were characterized by poor soil quality, but higher nutrient availability and greater colonization of invasive grasses and native shrubs. We suggest that the colonization of underdeveloped soils by invasive grasses may facilitate pedogenic processes and thus should be accepted by reclamation managers as a successional milestone in the recovery of ecohydrological functioning of constructed uplands. Poor soil structure under forest floor materials could not support edaphic conditions required by plants to efficiently utilize fertilizer, making this practise futile at the early stage of soil development.

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

“…However, competition will likely play a larger role in structuring the vegetation community in the future once all available growing space is occupied. The initial spike of non-native species on FFMM indicates a combination of species exploiting initial resources (Alday et al 2011;Buss et al 2018;Gingras-Hill et al 2018) and the higher amounts of seeds present within the seedbank in the FFMM (Errington and Pinno 2015;Mackenzie and Naeth 2010). Over time on the FFMM the species cover remained relatively constant but continued to increase on PMM, this is related to the available growing space (bare soil).…”

“…As plant communities develop, competition and facilitation play a larger role in structuring the community. Competition from the dominant species can negatively impact ecosystem development by limiting the abundance, reproduction of other species, and available nutrients; however, many of these species may also be facilitating species survival by filling a specific niche (Gingras-Hill et al 2018;MacDougall and Turkington 2005). Long-term effects of competitive non-native and graminoid species on reclamation sites are relatively unknown.…”

“…Long-term effects of competitive non-native and graminoid species on reclamation sites are relatively unknown. It is unknown whether they act as competitors or if they are pioneer species in the early stages of succession (MacDougall and Turkington 2005;Gingras-Hill et al 2018). These interactions are likely dependent on cover soil as FFMM plant richness is often higher than PMM, leading to increased competition on FFMM (Gingras-Hill et al 2018).…”

Do Weeds Hinder the Establishment of Native Plants on a Reclaimed North American Boreal Mine Site?

“…Many of the boreal weeds may be acting as temporary placeholders in the early stage of vegetation community development and can potentially be outcompeted over time. A study done in Alberta's oil sands region on a reclaimed upland forest suggests that within early successional communities, weedy species can act as pioneers and may be facilitating native revegetation long-term [12]. However, facilitative interactions from non-native plants on the native vegetation community are scarce and generally occur in high stress environments [13][14][15][16].…”

“…However, facilitative interactions from non-native plants on the native vegetation community are scarce and generally occur in high stress environments [13][14][15][16]. In many cases, non-native species in higher stress environments can be crucial in the recovery of optimal soil conditions which may be uninhabitable by native trees or understory species [12,16]. Through facilitation, weedy species have been shown to create better soil conditions and structure due to their ability to efficiently capture limited resources and in turn enhance aboveground and belowground biomass, leading to the addition of organic matter to the soil [12,15,16].…”