Spreading Topsoil Encourages Ecological Restoration on Embankments: Soil Fertility, Microbial Activity and Vegetation Cover

Abstract

The construction of linear transport infrastructure has severe effects on ecosystem functions and properties, and the restoration of the associated roadslopes contributes to reduce its impact. This restoration is usually approached from the perspective of plant cover regeneration, ignoring plant-soil interactions and the consequences for plant growth. The addition of a 30 cm layer of topsoil is a common practice in roadslope restoration projects to increase vegetation recovery. However topsoil is a scarce resource. This study assesses the effects of topsoil spreading and its depth (10 to 30 cm) on two surrogates of microbial activity (β-glucosidase and phosphatase enzymes activity and soil respiration), and on plant cover, plant species richness and floristic composition of embankment vegetation. The study also evaluates the differences in selected physic-chemical properties related to soil fertility between topsoil and the original embankment substrate. Topsoil was found to have higher values of organic matter (11%), nitrogen (44%), assimilable phosphorous (50%) and silt content (54%) than the original embankment substrate. The topsoil spreading treatment increased microbial activity, and its application increased β-glucosidase activity (45%), phosphatase activity (57%) and soil respiration (60%). Depth seemed to affect soil respiration, β-glucosidase and phosphatase activity. Topsoil application also enhanced the species richness of restored embankments in relation to controls. Nevertheless, the depth of the spread topsoil did not significantly affect the resulting plant cover, species richness or floristic composition, suggesting that both depths could have similar effects on short-term recovery of the vegetation cover. A significant implication of these results is that it permits the application of thinner topsoil layers, with major savings in this scarce resource during the subsequent slope restoration work, but the quality of topsoil relative to the original substrate should be previously assessed on a site by site basis.

Short-Term Landscape Restoration through Optimal Management of Stockpiled Topsoil on Plant Diversity and Growth of Tree Species

“…Addition of topsoil to the original substrate in embankment will increase soil fertility and this improvement will depend on the depth of the topsoil added to the original substrate. Organic matter content, total nitrogen and assimilable phosphorus were all higher in topsoil in comparison with original embankment substrate (Rivera et al, 2014). Generally, 0/100cm (T 1 ) recorded least values throughout the study.…”

“…(2008) found that increasing soil volume enhances biodiversity effects on plant production. According to Rivera et al (2014), topsoil application enhanced species richness of restored embankment in relation to control. However, the depth of the spread topsoil did not significantly affect resulting plant cover, species richness or floristic composition (Rivera et al, 2014).…”

“…According to Rivera et al (2014), topsoil application enhanced species richness of restored embankment in relation to control. However, the depth of the spread topsoil did not significantly affect resulting plant cover, species richness or floristic composition (Rivera et al, 2014). After 3 years, richness (S) significantly increased with soil depth (P < 0.0001), but there was no significant change in species diversity (P > 0.1) or composition (multi-response permutation procedure, P > 0.2).…”

Climate and soil factors influencing seedling recruitment of plant species used for dryland restoration

“…topsoil) in restoration of degraded semi-arid areas (Machado et al, 2013;Muñoz-Rojas et al, 2006b;Rivera et al, 2014). Muñoz-Rojas et al (2016b) showed that soil functions in a rehabilitated area of northwest Western Australia, with the use of mine waste material, can reach levels of microbial activity and organic C similar to those of topsoil once vegetation was established.…”

“…During open-cut and strip mining operations, the top layer of soil is commonly removed and stockpiled before starting the extraction process and then respread before seeding the target sites for restoration (Lamb et al, 2015;Rivera et al, 2014). This topsoil is an important source of seeds, nutrients and microorganisms Golos and Dixon, 2014;Koch, 2007;Muñoz-Rojas et al, 2016b) but its use in restoration is often limited by its scarcity and the detrimental conditions that topsoil stockpiling can have on soil functionality (Keipert et al, 2002).…”