Mycorrhiza re-establishment on post-mined rehabilitated areas of the Brand se Baai Succulent Karoo vegetation.

[摘要] Parts of the West Coast Strandveld and adjacent Succulent Karoo on the arid coast ofNamakwaland in the Western Cape of South Africa are subject to surface mining. Anunderstanding of mycorrhizal association of plants in the natural vegetation of thisarea could contribute to the improvement of post-mining re-vegetation of the area.This study investigated mycorrhizal association of plants in the West CoastStrandveld, and compared mycorrhizal infection rates of soils taken from naturalvegetation to soils from post-mined rehabilitated vegetations. The study was dividedinto two components.In the first component a pot experiment was conducted in the greenhouse to assessvesicular-arbuscular mycorrhiza (AM) infectivity of post-mined rehabilitated areas ofBrand se Baai in Namakwa Sands mining areas. Rehabilitated areas used in this studyincluded sites that has been strip mined for heavy minerals and then progressivelybackfilled with sub-soil sand remaining after mineral extraction (tailings), topsoil andtranslocated plants in an effort to restore the structure and functional aspects of themined site to its original (pre-mining) ecosystem. Rehabilitated sites 1 assessed in thisstudy included sites backfilled with: tailings + translocated plants (TP); tailing +topsoil + translocated plants (TSP) and tailings + topsoil only (TS). Natural sites (N)were also assessed to serve as reference points. AM infection was evaluated aspercent root colonization on wheat planted as bioassay on sterilised sand andinoculum from rehabilitated sites in the ratio of 3:1 respectively. Results of this studycomponent showed that mycorrhiza infectivity of rehabilitated soils was high on TSPand TS because mining disturbance has been remedied by topsoil with or withouttranslocated plant replacement. The structural and chemical components of topsoilused as rehabilitation material favoured re-establishment of microbial activities.Infectivity was however low on soils rehabilitated with tailings and translocatedplants (TP) because this treatment lacked topsoil which is a major source of infectivemycorrhizal propagules. Infectivity was also low in soils from undisturbed sites (N)probably high phosphorus concentration or presence of perennial vegetation led to low mycorrhiza infection. Results showed that there was no significant effect ofmycorrhiza on plant growth rate, nutrient uptake or carbon cost of mycorrhizal plantswhen related to non-mycorrhizal plants, instead the biomass production and nutrientcontents of plants were determined by chemical properties of treatment soils.The second component of the study investigated presence of mycorrhiza on randomlyselected common indigenous species of Aizoaceae, Asparagaceae, Asteraceae,Chenopodiaceae, Fabaceae, Lamiaceae, Mesembryanthemaceae, Restionaceae,families growing on unmined areas of the study site. Total mycorrhiza infection wasrecorded on 85% of the assessed species with percent infection level ranging from 8%in Atriplex lindleyi and Drosanthemum hispidum to 98% in Salvia lanceolata.Functional mycorrhizal association with arbuscule structures were however onlyobserved on 15% of all species assessed. Low arbuscules infection observed inindigenous species assessed in this study could be associated with the timing ofmycorrhiza infection assessment and root competition in the soil. There was noinfection observed on four species belonging to Chenopodiaceae, Zygophyllaceae,Sterculiaceae, and Asteraceae families, which represented 15% of all speciesassessed. Most species belonging to Chenopodiaceae and Zygophyllaceae have beenreported as non-mycorrhizal in other studies, absence of mycorrhiza on the remainingthree families species observed in this study require further confirmation.

[发布机构] Stellenbosch University