Landscape-scale links between microbial ecology and surface processes

Microbial activity on Earth’s surface is key in the decomposition of organic matter and humus formation, carbon sequestration, cycling of rock-derived nutrients, and the development of soil structure and stabilization. While the role of microbial life in various weathering processes has been demonstrated experimentally and observed at the nanometer-centimeter scale, the obvious link between microbial life activity and landscape-scale geomorphic processes remains unexplored.

We examined the reciprocal relationship between microbial communities and rates of surface processes in recently deglaciated landscapes in the eastern Sierra Nevada Mountains, California, USA. Sampling along an elevational transect in a glacial basin in the high Sierra (between 2800 and 3050 masl), we quantify exposure ages and rates of soil production using cosmogenic nuclides and examine microbial community ecology in the same rocks and soils. Exposure ages from cosmogenic ¹⁰Be indicate rapid deglaciation around 12-13 ka and relatively fast soil production rates (~4.3-4.5 cm/kyr), independent of elevation.

To understand how these rapid soil production rates correlate with microbial community composition and diversity, we extracted and sequenced environmental DNA from near-surface soils, saprolite samples, and exposed surface rocks. Microbiome sequencing results constrain changes in microbial ecology from rock to soil, shed light on the complex relationship between microbial community dynamics, and weathering rates in the eastern Sierra, and help us to better understand the link between life and landscape evolution.