Global datasets and Nd isotopes in pine needles estimate dust inputs to ecosystems in eroding landscapes

Inputs of dust can be essential to sustaining life in ecosystems where chemical weathering has depleted soils of bedrock-derived nutrients such as phosphorus. However, the ecological significance of dust has rarely been studied in mountain landscapes, where erosion continually exposes fresh minerals and thus provides a steady supply of bedrock-derived nutrients to soils. Despite the absence of empirical data, bedrock is thought to dominate the input of nutrients to soils in eroding landscapes. Here we use a global compilation of erosion rates and modeled dust fluxes to identify several eroding mountain landscapes where dust may provide a significant flux of nutrients to soils. During the Last Glacial Maximum (LGM), modeled dust inputs were on par with inferred bedrock supply rates in mountain ranges of western Europe and the eastern US. Although modern dust inputs in these regions are now orders of magnitude lower, soil residence times are long enough that high LGM dust fluxes likely influence modern nutrient cycling. In one landscape where inputs of dust are on par with bedrock, we employed a new application of Nd isotopes that directly quantifies the influence of dust on vegetation. Nd isotopes in pine needles, dust, and bedrock from our study site show that dust contributes as much as 88±13% of Nd to vegetation, demonstrating the ecological significance of dust in an eroding landscape. Together, our data compilation and isotopic measurements show that dust can dominate parent material inputs to soils and ecosystems despite continuous supply of fresh minerals from bedrock erosion.