Compromised root development constrains the establishment potential of native plants in unamended alkaline post-mining substrates

Abstract

Seed biology in the annual herbaceous flora of ecologically stressful, seasonally wet habitats remains largely unexplored. Temporal and spatial species turnover between these habitats is often high, yet little is known about how fine-scale habitat variation drives intraspecific variability in seed dormancy depth and seed germination requirements.This study characterised seed dormancy and investigated the germination biology of six closely-related herbaceous annual species of Byblis from northern Australia. We assessed variation in the response of seeds of all species to temperature cues, as well as light and the naturally occurring germination stimulants KAR1 and ethylene. We also examined intraspecific variation in germination response and seed dormancy depth for three widely-distributed species with overlapping distribution occurring in habitats with differing soil thermal and hydrological conditions. Seed germination in all six species was significantly increased by exposure to either KAR1 or ethylene with this effect amplified in two species (B. filifolia and B. rorida) following a period of warm, dry afterripening. Seed dormancy depth and the germination response of seeds to both KAR1 and ethylene was partitioned more strongly between habitats than between species. Populations on shallow (<20 cm soil depth) sandy soils produced less dormant seeds than populations of the same species on deeper sandy soils (40+ cm) or on heavy cracking clays. The upper soil profile of shallow soil habitats was exposed to higher average temperatures, greater diurnal temperature fluctuation and greatly reduced moisture persistence compared to deeper soils. Fine-scale differences in the thermal and hydrological conditions of seasonally wet habitats appear to be strong drivers of dormancy depth in seeds of tropical Byblis.Widely-distributed species exhibit high levels of plasticity in seed dormancy depth and germination response between different habitats, with similar responses observed for sympatric species. In order to fully understand species turnover in tropical ephemerals, future studies should examine phenotypic plasticity and the rate of local adaptation of seed traits in greater detail.

Soil reconstruction after mining fails to restore soil function in an Australian arid woodland

“…Topsoils are particularly susceptible to mixing with higher‐pH subsoils during initial topsoil stripping prior to mining activities. Similar increases in pH and EC were observed after mining in sites in northeast America (Shrestha & Lal ), and in the arid regions of China (Huang et al ) and Western Australia (Cross et al ), causing poor hydraulic conductivity and inhibiting plant growth.…”

“…Bulk density in the reconstructed soils in our study was >2 Mg/m 3 at 15 cm at some sites, suggesting a major impediment to root penetration. These properties are crucial factors regulating soil hydrological function, root development, and plant‐water uptake (Huang et al ; Cross et al ).…”

Growth performance and element concentrations reveal the calcicole-calcifuge behavior of three Adiantum species

“…Some calcifuge plants adapted to severely Ca-impoverished soils do not strongly down-regulate their Ca uptake capacity, and, consequently, are highly sensitive to calcareous soils [9]. They are excluded from calcareous soils also by their lacking ability to fulfill their requirements for other essential elements [6,8], and this limitation may be further exacerbated by the reduced element availability at alkaline pH [21]. In contrast, calcicole plants can tolerate excess Ca and take up nutrients when grown on calcareous soils [6].…”

Seed and Seedling Detection Using Unmanned Aerial Vehicles and Automated Image Classification in the Monitoring of Ecological Recovery

“…Monitoring needs can be idiosyncratic and complex between different sites, as project requirements can be influenced by factors such as substrate, local vegetation communities and landforms [28]; a 'dark' treatment of undisturbed local sandy soil capped with a 1 cm layer of tailings generated from the processing of magnetite ore [29]; and a 'high red-ratio' treatment of undisturbed local sandy soil capped with a 1 cm layer of red clay loam soil from a mine site in the Midwest region of Western Australia [28]. All capping materials were sourced from a major magnetite mining operation located approximately 400 km northeast of Perth, Western Australia.…”

“…Additionally, to examine whether seed and seedling detection rates were affected by surface topography, half of each treatment plot was manually ripped to a depth of 20 cm, using a backhoe ( Figure 1) to mimic standard ripping practices in post-mining restoration [27]. crushed overburden rock (2-20 cm in size, giving increased surface heterogeneity) used to rock armor the slopes of restoration landforms [28]; a 'dark' treatment of undisturbed local sandy soil capped with a 1 cm layer of tailings generated from the processing of magnetite ore [29]; and a 'high red-ratio' treatment of undisturbed local sandy soil capped with a 1 cm layer of red clay loam soil from a mine site in the Midwest region of Western Australia [28]. All capping materials were sourced from a major magnetite mining operation located approximately 400 km northeast of Perth, Western Australia.…”