Soil biodiversity restoration as a function of aridity

Soil represents the largest reservoir of biodiversity on the Earth. These soil organisms are further critical to support multiple ecosystem services, such as carbon sequestration and sustaining fertility. Unfortunately, a third of all global soils are already severely degraded. Restoring soil biodiversity is critical to ensure ecosystem sustainability for future generations. Yet, the effectiveness of restoration programs in supporting soil biodiversity remains poorly understood. Here, we conducted a standardized field survey at 248 sites across a 4000 km aridity gradient in China’s drylands, with the aim of investigating the restoration of the most abundant soil organisms of the planet, including nematodes, mites, bacteria, and fungi. This dryland region has undergone the world’s largest ecosystem restoration programs over the past four decades. Our work showed that the success of dryland ecosystem restoration programs to recover soil biodiversity is environmental context-dependent and relies on the level of aridity. Thus, the restoration programs implemented in more arid ecosystems had a more pronounced and positive influence on soil biodiversity, compared to less arid environments wherein natural succession is likely to have similar effects to active restoration on soil biodiversity. Our work indicates that the more arid ecosystem should be the priority target for soil biodiversity active restoration. This knowledge is essential to optimize resource allocation for preferentially restoring the most vulnerable ecosystems and supporting their long-term sustainability.