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Accueil du site → Doctorat → États-Unis → 1998 → Plant cover effects on surface roughness, infiltration, runoff, and sediment yield of a sagebrush-grass rangeland

Colorado State University (1998)

Plant cover effects on surface roughness, infiltration, runoff, and sediment yield of a sagebrush-grass rangeland

Mergen, Daryl Edwin

Titre : Plant cover effects on surface roughness, infiltration, runoff, and sediment yield of a sagebrush-grass rangeland

Auteur : Mergen, Daryl Edwin

Université de soutenance : Colorado State University

Grade : Doctor of Philosophy (PhD)1998

Résumé
Vegetative cover, plant height, and soil surface roughness were measured on 100 plots in a sagebrush-grass rangeland to determine the influence that canopy and ground cover had on surface roughness. Fifteen minute rainfall simulations (100 mm hr-1 ) were conducted on the 1.2 m 2 plots to determine the influence of cover and surface roughness on runoff and sediment yield. Cluster analysis was used to separate the complete data set into 4 vegetation cluster groups based on canopy cover and form, (1) grass, (2) grass/shrub, (3) shrub, and (4) forb/grass groups. Significant differences (p ≤ 0.05) were found in soil organic matter, soil bulk density, surface roughness, plant height, and runoff among vegetation cluster groups. Results of multiple regression analyses for 4 cluster groups were more robust as compared with results from the single data set. A discriminant analysis model identified the percentage of bare ground, grasses, litter, and shrubs as important variables required for group separation and classification. Results of stepwise regression analyses, with runoff as the dependent variable, indicated that the time runoff began and soil characteristics were important. Results of stepwise regression analyses with sediment yield as the dependent variable indicated that vegetation and ground cover were important. Surface roughness (measured as a standard deviation) was significantly greater (p < 0.05) in the shrub group (38) and the grass group (12) was significantly less (p < 0.10) than the grass/shrub (19) and the forb/grass (20) groups. Shrubs created a mean soil surface height of 11 mm greater than bare soil followed by litter 5 mm, cryptogams 4 mm, grasses 3 mm, and forbs 2 mm. These differences in surface roughness in the shrub group were estimated to influence the amount of soil surface area exposed to runoff. Up to 50% less surface area could be exposed to infiltration in the shrub group compared with the other cluster groups at the same depth of runoff.

Mots clés : Surface roughness, Sediment yield, Infiltration, Hydrology, Sagebrush-grass rangeland, Plant cover Biological sciences, Earth sciences, Range management, Runoff

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