Divergent hydrological responses to restoration between planted and natural forests basins in drylands

Semi-arid and arid regions Afforestation in global arid and semi-arid regions has expanded over the past two decades, largely driven by carbon-sequestration initiatives, but these activities consume substantial water and may constrain local development. Policy makers are therefore increasingly concerned about how to minimize the water consumption associated with restoration in drylands. However, it remains unclear how different forest management types, such as planted and natural forests (PFs and NFs), affect basin-scale water yield. Using the evapotranspiration data, forest management maps, and climate datasets, we investigated the water yield responses to forest expansion in planted and natural forests basins based on the Budyko framework. For the long-term average, the water yields in PFs basins are 3–12 % less than those in NFs basins. When considering the changes following forest expansion, the reduction in water yield is about 10 % greater in PF basins than in NFs. Attribution analysis points to underlying alteration rather than climate change as the main contributor to both water yield decrease. However, the underlying contribution is substantially larger in PF basins than in NF basins. This is because PF basins exhibit greater changes in their underlying surface parameter. Before afforestation, the sensitivities of water yield to both underlying surface conditions and climate were comparable between PFs and NFs basins. After restoration, these sensitivities became markedly larger in PFs basins than in NFs basins. The difference in ecosystem biodiversity and complexity between PFs and NFs basins can be the potential reason for the divergent water yield responses to restoration. • Planted forests in drylands lose more water, but reduce losses in humid zones. • Water sensitivities to land and climate are higher in planted forest basins post-restoration. • Natural growth is an option to reduce the local negative hydrological effects from vegetation change.