LANDSCAPE-SCALE LINKS BETWEEN MICROBIAL ECOLOGY AND SURFACE PROCESSES IN THE EASTERN SIERRA MOUNTAINS, CA

The relationship between life and landscapes on Earth has long been established. These interconnections are expressed by the variability of life along different neighboring environments but also by changes to Earth’s surface brought on by the organisms living in these locations. While the role of microbial life in various weathering processes has been demonstrated experimentally and observed at the nanometer-centimeter scale, the apparent 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 (soil production, surface weathering, and erosion) 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 quantified 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 examine 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.