Evaluation of topsoil inversion inU.K.habitat creation and restoration schemes

Abstract

Habitat creation and restoration schemes on former agricultural soils can be constrained by high residual soil fertility, a weedy seed bank, and a lack of suitable species in the seed rain. Topsoil inversion has been trialled across the United Kingdom as a novel technique to address these constraints. We investigated 15 topsoil inversion sites ranging in age (time since inversion) from 6 months to 5 years. We assessed surface soil fertility compared to adjacent noninverted soil, and vegetation composition with respect to the species introduced at each site. Soil organic matter, total and extractable N and P were lower in topsoil inversion surface soils, demonstrating that topsoil inversion can successfully reduce surface soil fertility prior to habitat creation and restoration. This reduction was maintained over the timescale of this study (5 years). Cornfield annual nurse crops provided instant visual appeal and gave way to grassland species over time. Sown species varied widely in their establishment success, and sowings were more successful than plug plantings. Grasses colonized naturally following sowing forb-only seed mixes, allowing introduced forbs to establish early on with reduced competition from the seed bank. Plant communities did not yet resemble seminatural communities, but all were in the early stages of community development. Results indicate that topsoil inversion can successfully lower surface soil fertility and reduce competition between sown species and agricultural weeds.

Seed bank dynamics in restored grassland following the sowing of high‐ and low‐diversity seed mixtures

“…This means that the vertical distribution of seeds across the actively managed soil profile may have been fairly homogeneous at the start of the experiment, and therefore the two cultivation treatments may have had little effect in terms of vertical redistribution of seeds in the soil profile. Accordingly, Glen () found that, compared to deep‐plowing to greater depths, conventional plowing has very limited effects on the seed bank in ex‐arable restoration.…”

“…Deep cultivation consisted of plowing to a depth of 30–40 cm, which inverted the uppermost soil layer. This is similar to conventional agricultural plowing and is not to be confused with the more recently developed restoration practice of “deep‐plowing,” which typically involves cultivation to a depth of about 80 cm (Glen et al ). The experiment was set up in four replicate blocks per site, and treatment plots were 6 m × 4 m with a 1‐m guard row between the plots (Pywell et al ).…”

Chronosequence of former kaolinite open cast mines suggests active intervention is required for the restoration of Atlantic heathland

“…There seems little potential, therefore, to expect long‐term, natural ALH recovery on the many kaolinite open cast mines located in regions where this habitat is most common, and especially where restoration occurs alongside active mining. Instead, and like many OCM sites globally, heathland restoration can likely only be facilitated by further interventions after mining operations cease (Holmes : Benigno et al ; Clemente et al ; Glen et al ).…”

“…On this basis, many different restoration techniques have been tested (Pywell et al ; Clemente et al ) but these can be categorized into two classes: those involving soil amelioration (e.g. nutrient addition, overturning) and those involving the selective addition of plants or seeds (Allison & Ausden ; Walker et al ; Pywell et al ; Glen et al ). The results of many previous studies indicate the most important factor for successful heathland restoration is prior land use, as the most successful restorations are situated on former heathland (Walker et al ).…”

Seed use in the field: delivering seeds for restoration success

“…Topsoil replacement, fertilization, or inoculation may be necessary on some sites such as mine spoils or other severely degraded or soil‐less sites to improve organic matter, nutrient status, and soil microbial communities (Munshower 1993). Conversely, on formerly cropped land, steps may be required to reduce nutrient status to favor native species and reduce weed invasions (Kirmer & Tischew 2014; Glenn et al 2017). Techniques used to reduce nutrient status include soil inversion, deep tillage to mix topsoil with deeper soil layers, or cultivation without fertilization for one or more years.…”