Native-plant amendments and topsoil addition enhance soil function in post-mining arid grasslands

Area of Science:

• Environmental Science
• Soil Science
• Restoration Ecology

Background:

• Disturbed arid lands, particularly post-mining sites, face severe topsoil limitations, hindering revegetation efforts.
• Mine waste often lacks essential soil characteristics, requiring amendments to support seedling establishment and survival.
• Organic matter addition is proposed as a strategy to enhance soil function and plant survival in degraded arid ecosystems.

Purpose of the Study:

• To evaluate the impact of soil reconstruction, plant species composition, and organic amendment on seedling establishment and soil properties in arid mining restoration.
• To assess the effects of native organic amendment (Triodia pungens biomass) on the growth and survival of Triodia wiseana.
• To analyze changes in soil chemical, physical, and biological characteristics, including microbial activity and nutrient mineralization, in reconstructed soils.

Main Methods:

• A 12-month multifactorial microcosm study was conducted in a controlled environment.
• Restoration techniques included blending soil materials, varying plant compositions, and amending with Triodia pungens biomass.
• Soil properties measured included microbial activity, total organic carbon (C), total nitrogen (N), and C and N mineralization rates.

Main Results:

• Organic amendment increased soil C and N content, though levels remained lower than in natural topsoil.
• Amended mine waste exhibited high microbial activity and C mineralization, but low N mineralization, negatively impacting Triodia wiseana emergence and survival.
• Similar growth and survival rates of Triodia wiseana were observed in pure topsoil and a 50:50 topsoil-mine waste blend.

Conclusions:

• Fresh organic amendments can lead to short- to medium-term nitrogen immobilization, potentially hindering seedling establishment in arid mine restoration.
• The presence of even a reduced amount of topsoil is critical for successful plant establishment in reconstructed arid soils.
• Future restoration strategies should consider the timing and type of organic amendments to mitigate nutrient immobilization and promote plant survival.