Role of Vachellia karroo as a nurse plant in oldfields targeted for passive restoration

Background: In degraded environments such as oldfields, nurse plants can facilitate the growth of targeted restoration plant species through ameliorating them from extreme environmental conditions, creating nutrient rich microclimates, and protecting recruiting plants from grazing. Objectives: This study examined the role of Vachellia karroo nurse plant on soil physico-chemical properties and vegetation diversity in oldfields targeted for passive restoration at Tanglewood research farm in Eastern Cape Province, South Africa. Methods: Soil were quantified for physico-chemical properties in 48 plots measuring 25 m2 (5 m x 5 m) that were located under and outside 24 V. karroo nurse plants. In addition, detailed vegetation surveys were conducted in the above-mentioned plots. Results: Our results show that soil total N and C concentrations were higher under than outside V. karroo nurse plants. Soil penetration resistance and water repellency levels were lower under than outside V. karroo nurse plants, however monthly variations were also observed. Species richness and Shannon-Wiener diversity were higher under than outside V. karroo nurse plants, with species such as Searsia crenata, Azima tetracantha, Asparagus africanus, and Opuntia sp., frequently occurring under V. karroo nurse plants. Conclusion: The study concludes that V. karroo nurse plant has a positive effect on some soil physico-chemical properties and vegetation diversity underneath it. It is recommended that V. karro needs to be included in future oldfield restoration strategies if passive restoration at Tanglewood research farm is to be successful.