Scaling up enhanced rock weathering: field trials and ecohydrological modelling in a temperate forest

Enhanced Rock Weathering (ERW) utilizing basalt in forest ecosystems has emerged as a potentially scalable strategy for carbon dioxide removal (CDR) in the context of anthropogenic climate change. Despite a robust theoretical understanding of weathering processes across geological timescales, a critical lack of empirical ERW data exists for assessing its efficacy in climate mitigation at relevant timescales. Here, we present the first large-scale, replicated field trial of ERW coupled with tree planting at an afforestation experiment in mid-Wales. The factorial experimental design integrates basalt application and tree functional types (broadleaf vs. coniferous), examining key parameters such as soil pore water pH, alkalinity, soil respiration and aboveground tree biomass. By employing novel sampling techniques, we quantify ERW extent, providing nuanced insights. Over the first three years, initial observations highlight nutrient cycling perturbations post-basalt addition, offering immediate insights into ERW effects in a forested ecosystem. To mechanistically elucidate these observations, we introduce a novel ERW module within the Tethys-Chloris ecohydrological model framework, integrating a microbially explicit soil biogeochemical component. This integrated model aims to provide a robust foundation for understanding how ERW dynamics influence ecosystem carbon sequestration and guide best sampling practices.