How lithology impacts global topography, vegetation, and animal biodiversity

Abstract:

Chemical and mechanical properties of lithology set boundary conditions for landscape evolution and biological colonization of substrate. Topographic steepness is thought, in part, to be determined by the erodibility of bedrock; soil properties partially reflect the geochemistry and structure of the parent bedrock. To quantify the influence of lithology on topography, vegetation density, and animal biodiversity, I compile global lithologic, topographic, climatic, and biological datasets. I find significant differences between slope and river channel steepness among most lithologies that, after accounting for tectonic uplift regimes, likely reflect differences in erosional resistance among lithologies. Additionally, I split the dataset into different climate zones and do not find evidence that climate influences the relative steepness differences of the main lithologic units. To isolate the effect of lithology on vegetation and animal biodiversity, I account for the heterogeneous lithologic distribution among climate zones, by using temperature-precipitation binning of data, multiple linear regression, and generalized additive models. I show that siliciclastic, plutonic, and, for some biological variables, metamorphic rocks exhibit elevated values of vegetation density and tetrapod and amphibian species richness, relative to carbonate rocks. These results likely reflect lithology-related variation in soil nutrients and hydrology that promote or inhibit habitat suitability, and highlight how karst surface water infiltration affects local biology. These findings illustrate the importance of bedrock lithology as a predictor of topographic form and terrestrial biota on Earth.