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ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Publications at this Location » Publication #287521
Title: Runoff and sediment yield relationships with soil aggregate stability for a state-and-transition model in southeastern Arizona

Author
item Holifield Collins, Chandra
item Stone, Jeffry
item CRATIC III, L. - University Of Arizona

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2015
Publication Date: 3/1/2015
Citation: Holifield Collins, C.D., Stone, J.J., Cratic Iii, L. 2015. Runoff and sediment yield relationships with soil aggregate stability for a state-and-transition model in southeastern Arizona. Journal of Arid Environments. 117:96-103.

Interpretive Summary: A relatively quick and easy method to evaluation of a rangeland site’s potential to erode is the soil slake test. The test measures how strong soil aggregates are which is supposed to be indicative of how easily erodible the soil is. The resulting aggregate stability (AS) value is used within the context of a State and Transition Model which is a description of how a specific soil-vegetation association changes with changing climate and management. This study uses runoff and erosion data from a series of rainfall simulator experiments on sites of a State and Transition Model to test if AS is related to those hydrologic processes. The results show that the AS is not related to runoff but that erosion follows the trends suggested by the stability values. Analysis of relationships between runoff and erosion with canopy cover and bare soil suggest that there are thresholds beyond which both of these factors have the potential of increasing. The results also suggest that for AS < 4, the potential for a site to become unstable increases.

Technical Abstract: Soil erosion has been identified as the primary abiotic driver of site degradation on many semiarid rangelands. A key indicator of erosion potential that is being increasingly implemented in rangeland evaluations is soil aggregate stability (AS) as measured by a field soil slake test. However, there have been few studies that test if decreasing AS is an indication of increasing soil erosion. A rainfall simulator experiment was conducted in southeastern Arizona to measure runoff and erosion, aggregate stability, and cover attributes on three vegetation states of the state and transition model (STM) of the Loamy Upland ecological site. The states included the historic climax plant community (HCPC), a site encroached by mesquite (MN), and a site invaded by Lehmann lovegrass (ML). Within the context of the STM, runoff was only different between very high and low cover states. In contrast, both the values of erosion and AS better differentiated among the states, particularly between the HCPC and MN states. Runoff amount was not related to AS but erosion showed a non-linear negative relationship with increasing AS. Relationships between runoff and erosion with canopy cover and interspace bare soil suggest that certain cover thresholds exist where runoff and erosion have the potential to increase. The results also suggest that for this ecological site, AS < 4 may represent an increased potential for site degradation.Soil erosion has been identified as the primary abiotic driver of site degradation on many semiarid rangelands. A key indicator of erosion potential that is being increasingly implemented in rangeland evaluations is soil aggregate stability (AS) as measured by a field soil slake test. However, there have been few studies that test if decreasing AS is an indication of increasing soil erosion. A rainfall simulator experiment was conducted in southeastern Arizona to measure runoff and erosion, aggregate stability, and cover attributes on three vegetation states of the state and transition model (STM) of the Loamy Upland ecological site. The states included the historic climax plant community (HCPC), a site encroached by mesquite (MN), and a site invaded by Lehmann lovegrass (ML). Within the context of the STM, runoff was only different between very high and low cover states. In contrast, both the values of erosion and AS better differentiated among the states, particularly between the HCPC and MN states. Runoff amount was not related to AS but erosion showed a non-linear negative relationship with increasing AS. Relationships between runoff and erosion with canopy cover and interspace bare soil suggest that certain cover thresholds exist where runoff and erosion have the potential to increase. The results also suggest that for this ecological site, AS < 4 may represent an increased potential for site degradation.