Ecosystem carbon and nitrogen gains following 27 years of grazing management in a semiarid alluvial valley

Brian Morra; Hondo Brisbin; Tamzen Stringham; Benjamin W Sullivan

doi:10.1016/j.jenvman.2023.117724

Ecosystem carbon and nitrogen gains following 27 years of grazing management in a semiarid alluvial valley

J Environ Manage. 2023 Jul 1:337:117724. doi: 10.1016/j.jenvman.2023.117724. Epub 2023 Mar 24.

Authors

Brian Morra¹, Hondo Brisbin², Tamzen Stringham², Benjamin W Sullivan³

Affiliations

¹ Department of Natural Resources and Environmental Science, The University of Nevada, Reno, 1664 N. Virginia St., Reno, NV, 89557, USA. Electronic address: bmorra@nevada.unr.edu.
² Department of Agriculture, Veterinary, and Rangeland Sciences, The University of Nevada, Reno, 1664 N. Virginia St., Reno, NV, 89557, USA.
³ Department of Natural Resources and Environmental Science, The University of Nevada, Reno, 1664 N. Virginia St., Reno, NV, 89557, USA; The Global Water Center, The University of Nevada, Reno, 1664 N. Virginia St., Reno, NV, 89557, USA.

PMID: 36966635
DOI: 10.1016/j.jenvman.2023.117724

Abstract

Soils in semiarid riparian ecosystems have large carbon (C) stocks that promote water and nutrient availability for productive plant communities consumed by grazing animals. Changes to riparian hydrologic conditions caused by channel incision result in different edaphic conditions and a greater abundance of upland plant species that may be associated with lower soil C stocks. Using riparian meadows alongside Maggie Creek in central Nevada, we show that 27 years of modified grazing practices can repair ecosystem processes and increase the C stocks. We compared C and nitrogen (N) stocks (of soils and plant biomass) on floodplains, terraces, and uplands of reaches where grazing was either modified or excluded to reaches where no changes to grazing practices were made. Grazing management allowed beaver to establish, improving hydrology and lengthening the growing season. These changes allowed C and N to accumulate on geomorphic surfaces that extended from the stream channel to the surrounding hillslopes. A stoichiometric relationship between C and N shows carbon sequestration can reduce nutrient runoff to nearby waterways and may depend on nitrogen availability. Gains in ecosystem carbon ranged from 93 to 452 g C m^-2 y^-1 and were dominated by increases in soil C. Gains in soil C occurred across the full depth range measured (0-45 cm) and were comparable to those found in restored wetlands and meadows located in more humid ecosystems. Carbon gains exhibited substantial variability caused by microtopography and plant community composition. While grazing exclusion resulted in the largest gains in ecosystem C, managed grazing that limited consumption of riparian plants increased ecosystem C relative to reaches where management wasn't changed. We demonstrate that managed grazing that maintains ecosystem process is compatible with projects aimed at increasing soil carbon in semiarid riparian rangelands.

Keywords: Beaver; Great Basin; Groundwater dependent; Maggie Creek; Meadow; Process based restoration; Rangeland; Wetland.

MeSH terms

Animals
Biomass
Carbon
Ecosystem*
Nitrogen* / analysis
Plants
Soil

Substances

Nitrogen
Carbon
Soil