The current and future role of biota in soil-landscape evolution models

Biota are major drivers of geomorphological development. Vegetation and soil fauna act as ecosystem engineers, changing the environment through physical structures and individual activities such as litter layering, tree uprooting, and animal mounding. Furthermore, through varying litter quality triggering different degrees of animal bioturbation, they jointly drive soil and landscape development heterogeneously in space over time. Soil-landscape evolution models succeed in incorporating soil development with landscape evolution. However, the roles of biota and biotic interactions in these models are still underexposed. We cannot fully understand changes in environmental and soil-landscape systems without a proper appreciation of biotic processes. In this contribution, we first review the role of biota in pedological and geomorphological processes. Then we compare the coverage of soil and landscape processes of soil-landscape evolution models and outline the role of biota in current soil-landscape evolution models. Finally, we define five levels of soil-landscape evolution model complexity that allow increased detail in biota-soil-landscape interactions. The results show how vegetation characteristics and animal bioturbation in current models are simplified compared with geomorphological processes, and that the geomorphological impact of litter quality and quantity and interactions between vegetation and animals are not taken into consideration at all. As understanding the complex soil-landscape-biota system is fundamental in exploring the coevolution of ecosystem and landscape, it deserves more efforts to develop a biota-soil-landscape evolution model that does more justice to the manifold impacts of biota.