Distinctive dryland soil carbon transformations and management: Insights from arid rangelands of southwestern United States

Authors: STEINER, JEAN - New Mexico State University; BRANDANI, CAROLINA - Texas A&M University; CHAPPELL, ADRIAN - Cardiff University; CASTANO-SANCHEZ, JOSE - New Mexico State University; HOELLRICH, MIKAELA - New Mexico State University; MCLNTOSH, MATTHEW - New Mexico State University; NYAMURYEKUNG'S, SHELEMIA - New Mexico State University; PIETRASIAK, NICOLE - New Mexico State University; Rotz, Clarence - Al; WEBB, NICOLAS - New Mexico State University

Submitted to: Advances in Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary: Ruminant livestock grazing often supports food and livelihoods in the arid rangelands which occupy about 40% of the terrestrial surface and are home to about 35% of the world's population. The importance of the biodiversity and abundance of direct and indirect ecosystem services of dryland regions is under-recognized and not well understood. Sustaining the soil resource is critical to sustaining these ecosystems and the people and biodiversity they support. Insight into the carbon dynamics in rangelands, highlight contrasts between dryland and more humid regions, and identify management practices to adapt to and sustain the natural resource base in rangeland systems. Managing multiple ecosystem services is critical, including sustaining the livelihoods of those who live on, and manage, the land. Sustaining ecosystem services, not solely for human benefits, requires maintaining the resource base, but past attention to dryland systems has focused on direct production benefits and has under-valued the indirect benefits of climate regulation, water supply and filtering, nutrient cycling, biodiversity, and others. Developing these benefits requires a new focus across global, national, and regional scales, as well as innovative technologies and approaches at the local level. 

Technical Abstract: Much of our understanding of soil carbon stems from research in humid, temperate environments; however, examples from southwestern USA describe distinctive dryland influences and carbon (C) transformations. Drylands occupy over 40% of earth’s land surface, have generally hot temperatures, small soil moisture, large evaporation, and consequently, small net primary productivity (NPP). Although soil organic carbon concentrations are small, vast dryland areas contain about 36% of global soil C stock. Unlike humid regions, soil inorganic carbon (SIC) is a large C stock in drylands. While often regarded as inactive, SIC is important for aggregation and soil organic matter protection in drylands and its biogeochemical processes may be managed to sequester SIC. Biocrusts are widespread in drylands, protecting soil from erosion and sequestering C, responsible for 25% of terrestrial nitrogen fixation and about 9% of dryland NPP. Drylands exclusively erode C by wind which redistributes organic matter and reduces C stocks without direct addition of carbon dioxide to the atmosphere. All these dryland distinctions are inadequately represented in models, particularly the significance of SIC, the role of biocrusts, and the large proportion of net ecosystem exchange diverted away from the atmosphere, relative to more humid environments. Past focus on direct production benefits has under-valued indirect benefits of climate regulation, water supply and filtering, nutrient cycling, biodiversity, and requires re-evaluation across scales of intervention to optimize multiple benefits in arid rangelands.