Environmental drivers of planted seedling performance in a Zambian Miombo woodland restoration area

Miombo woodlands, crucial for biodiversity and ecosystem services in Southern Africa, face severe degradation, demanding ambitious restoration efforts in the coming decades. While Miombo restoration typically relies on passive regeneration, active tree planting may become increasingly necessary in highly degraded areas. For a planting approach to be successful, a better understanding is needed of which environmental factors drive higher survival and growth of the seedlings. Here, we examined the impact of environmental drivers on survival and growth rates of Miombo seedlings over two years post-planting in a Zambian restoration area, focusing on species' functional traits (specific leaf area, wood density, seed mass, specific root length), soil properties (pH, bio-available phosphorus, bulk density, CN-ratio), and neighboring woody plants. Traits associated with faster resource acquisition, such as higher specific root length, positively influenced growth, while traits linked to resource conservation, such as higher wood density and seed mass, negatively influenced growth. Seedling survival notably declined in soils with pH levels above 6.5, while growth was higher in soils with greater bulk density and lower phosphorus concentration. Our findings highlight the complexity of seedling performance and emphasize the need for tailored restoration strategies. Controlled experiments are needed to test the interactive effects of environmental drivers and targeted interventions that could significantly improve outcomes (such as shading, water addition, and mycorrhizal inoculation), on Miombo planting performance. Such efforts will provide practitioners with the evidence-based tools needed to enhance planting success in Miombo woodlands.