The effects of neighbor, distance, and organic fertilizer on the establishment and early performance of three woody species in a restoration trial in the Kunene region, Namibia
Land degradation poses a significant challenge in arid ecosystems across Africa, adversely affecting the livelihoods of many who depend on the environment. It has become an urgent priority to restore these ecosystems. While various restoration approaches have been studied globally, few have explicitly considered how neighboring plant species and plant spacing as well as organic fertilizer influence restoration outcomes. This study evaluated the effects of neighbor identity, planting distance, and organic fertilizer on the growth, survival, and leaf traits of three woody species – Vachellia erioloba, Colophospermum mopane, and Combretum imberbe. Experiments were conducted in outdoor and indoor environments using a "two-factor (2x9) complete randomized factorial design" with nine neighbor combinations and two levels of distance/fertilizer. Results from field experiments showed that neighbor effects varied by species. C. imberbe experienced improved stem length and biomass when paired with V. erioloba, while C. mopane had reduced survival when grown with V. erioloba at close spacing. Leaf nitrogen and surface area were generally lower when species were paired with heterospecific neighbors, with V. erioloba exerting the strongest influence. Wider spacing (1 m) enhanced growth and leaf traits for most species, although the impact on survival and nutrient uptake varied depending on species. In the greenhouse, manure produced mixed results, enhancing leaf traits for C. imberbe and V. erioloba when grown alone or with conspecifics, but reducing growth and survival in the presence of heterospecific neighbors. Recruitment of native species was positively associated with C. mopane and C. imberbe, especially under 1 m spacing, while V. erioloba showed a negative association. These findings could inform future revegetation initiatives and help design planting strategies that enhance target species performance in restoration
Land degradation, Ecological restoration, Plant interactions, Neighbors, Distance, Fertilizer, Woody species, Namibia, University of Namibia
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