Time-lagged responses of soil biota are pervasive and require new approaches

Tanel Vahter, Oscar Zárate-Martínez, Jarno Vanhatalo, Tomas Roslin

When land-use changes, soil biodiversity is typically assumed to respond immediately. Nonetheless, soils are inherently slow systems. We argue that soil communities often remain in a transient state for decades to centuries, generating persistent ecological legacies. These lags can arise through two interacting mechanisms: environmental inertia, as the physical and chemical properties of soils change slowly, and source limitation, as habitat loss erodes species pools at the landscape scale. We synthesize evidence that these processes generate long-term ecological memory in soils. As a consequence of time-lagged effects, soil systems may commonly exhibit extinction debt and recovery credit. While these concepts are well established in metapopulation theory, they remain underdeveloped for belowground biodiversity. Our perspective challenges static interpretations of soil biodiversity patterns and suggests that contemporary observations often reflect past land use more strongly than present conditions. To quantify these dynamics, we outline a research agenda integrating large-scale soil biodiversity data, historical land-use trajectories, and modelling approaches to separate legacy effects from contemporary drivers. Identifying where and when soil legacies persist, and when management or restoration can offset them, is essential for generating realistic projections of soil biodiversity under global change.