Leguminous tree species create islands of fertility and influence the understory vegetation on nickel-mine tailings of different ages

• Published in: Ecological engineering 2020-08, Vol.155, p.105902, Article 105902
• Main Authors: Nyenda, T., Gwenzi, W., Gwata, C., Jacobs, S.M.
• Format: Article
• Language: English
• Subjects: Age; Available phosphorus, organic matter, bulk density, fertility island; Bulk density; Calcium; Canopies; Canopy; Clay minerals; Ecological effects; Fertility; Islands; Mine tailings; Mine wastes; Nickel; Nitrogen; Organic matter; Organic phosphorus; Phosphorus; Physicochemical processes; Physicochemical properties; Plant communities; Plant cover; Plant populations; Planting density; Potassium; Reclamation; Rehabilitation; Seedlings; Species; Species richness; Species richness, vegetation cover, leguminous trees; Substrates; Tailings; Total N; Trees; Tropical climate; Understory; Variance analysis; Vegetation; Vegetation community; Vegetation cover; Vegetation effects; Vegetation establishment
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2020.105902

Understanding the patterns of vegetation establishment on rehabilitated mine tailings is critical in evaluating the effectiveness of rehabilitation programs, but is still largely unknown. The concept of formation of fertility islands and their effect on vegetation establishment on two rehabilitated nickel mine tailings of different ages (20 and 40 years) since last depositions in tropical Zimbabwe was investigated to compare: (1) the tailings physicochemical properties: nitrogen (N), phosphorus (P), potassium (K), organic matter (OM), calcium (Ca), pH, salinity, texture and bulk density between perceived fertility islands (tree-canopy sites) and off- canopy sites, (2) vegetation structural and compositional attributes of canopy and the adjacent off-canopy sites, on the two tailings dumps, and, (3) to identify substrate correlates to observed vegetation attributes. We hypothesized that: (1) total N, Mineral N, OM and available P were significantly higher on canopy than adjacent off- canopy sites, (2) vegetation cover and species richness were higher on canopy than on off-canopy sites, and, (3) dump age and tree species had significant effect on substrate and vegetation attributes. We sampled substrate and vegetation in 1 m2 quadrats laid under planted tree canopies and the adjacent off-canopy sites on tailings dumps that were rehabilitated by planting leguminous trees. The Factorial ANOVA test showed that dump age and tree species had no significant effect on substrate properties and vegetation attributes. Mineral N, total N, available P, OM, and clay content were significantly higher on canopy than on the adjacent off-canopy sites while bulk density was significantly lower on canopy than on off-canopy sites. All vegetation structural attributes (overall plant aerial cover, grass cover, forb cover, woody seedlings cover and tuft density), species richness were significantly higher on canopy than on off-canopy sites. Plant communities on canopy sites were distinct from those on off-canoppy sites, regardless of dump age. Results demonstrate the ecological engineering potential of the leguminous trees through creating fertility islands that influence understory vegetation establishment on mine tailings. •Fertility islands (FIs) were formed under canopies of planted leguminous tree species on nickel mine tailings•Vegetation cover and diversity were significantly higher on the FIs than on the adjacent sites.•Plant communities on FIs were distinct from those on o