Plant/life form considerations in the rangeland hydrology and erosion model (RHEM)

Authors: SPAETH, KENNETH - Natural Resources Conservation Service (NRCS, USDA); Weltz, Mark; Williams, Christopher - Jason; Pierson Jr, Frederick

Submitted to: International Rangeland Congress
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2016
Publication Date: 7/18/2016
Citation: Spaeth, K.E., Weltz, M.A., Williams, C.J., Pierson Jr, F.B. 2016. Plant/life form considerations in the rangeland hydrology and erosion model (RHEM). In: Proceedings of the X International Rangeland Congress, July 18-22, 2016, Saskatoon, Saskatchewan, Canada. p. 1005-1006.

Interpretive Summary: Resilience of rangeland to erosion has largely been attributed to adequate plant cover; however, plant life/growth form, and individual species presence can have a dramatic effect on hydrologic and erosion dynamics on rangelands. Plant life/growth form refers to genetic tendency of a plant to grow in a certain shape and height (e.g., plants may be classified as trees, shrubs, vines, herbs (forbs and graminoids); sod forming; caespitose, tufted, or bunchgrass, sod/bunch; annual, biennial, or perennial). Field studies have shown that infiltration is usually greatest under trees and shrubs, followed by bunchgrass, annual grasses, and sodgrass. Grass species with well-defined bunchgrass life/growth forms have been correlated with higher infiltration capacity compared to sodgrass forms. The Rangeland Hydrology and Erosion Model (RHEM) was developed from rainfall simulation experiments on numerous vegetation types throughout the western U.S. RHEM considers the effect of plant life/growth forms with specific effective hydraulic conductivity and splash and sheet erosion equations. This paper demonstrates RHEM hydrology and erosion estimate sensitivity to plant life/growth forms in shortgrass prairie. Our results demonstrate the sensitivity of RHEM runoff and erosion responses to plant life/growth forms i.e., bunchgrasses and sodgrasses. Predictive plant variables such as foliar cover, production, and biomass are commonly used in developing regression equations and modeling hydrology and erosion in rangeland ecosystems. Plant morphological differences above and below ground exist between shrubs, bunchgrasses, sodgrasses, and forbs and are concomitant with differences in above ground foliar architecture and root morphology (taproot, fibrous roots, shallow or deep rooting systems, root pans). Individual equations were developed and incorporated into RHEM to account for life/growth form influences on hydrology and erosion in rangeland ecosystems.

Technical Abstract: Resilience of rangeland to erosion has largely been attributed to adequate plant cover; however, plant life/growth form, and individual species presence can have a dramatic effect on hydrologic and erosion dynamics on rangelands. Plant life/growth form refers to genetic tendency of a plant to grow in a certain shape and height (e.g., plants may be classified as trees, shrubs, vines, herbs (forbs and graminoids); sod forming; caespitose, tufted, or bunchgrass, sod/bunch; annual, biennial, or perennial). Field studies have shown that infiltration is usually greatest under trees and shrubs, followed by bunchgrass, annual grasses, and sodgrass. Grass species with well-defined bunchgrass life/growth forms have been correlated with higher infiltration capacity compared to sodgrass forms. The Rangeland Hydrology and Erosion Model (RHEM) was developed from rainfall simulation experiments on numerous vegetation types throughout the western U.S. RHEM considers the effect of plant life/growth forms with specific effective hydraulic conductivity and splash and sheet erosion equations. This paper demonstrates RHEM hydrology and erosion estimate sensitivity to plant life/growth forms in shortgrass prairie. Our results demonstrate the sensitivity of RHEM runoff and erosion responses to plant life/growth forms i.e., bunchgrasses and sodgrasses. Predictive plant variables such as foliar cover, production, and biomass are commonly used in developing regression equations and modeling hydrology and erosion in rangeland ecosystems. Plant morphological differences above and below ground exist between shrubs, bunchgrasses, sodgrasses, and forbs and are concomitant with differences in above ground foliar architecture and root morphology (taproot, fibrous roots, shallow or deep rooting systems, root pans). Individual equations were developed and incorporated into RHEM to account for life/growth form influences on hydrology and erosion in rangeland ecosystems.