Infiltration rate decreased significantly and sediment production increased significantly on a site with a silty clay surface soil devoid of vegetation following periodic trampling typical of intensive rotation grazing systems. The deleterious impact of livestock trampling generally increased as stocking rate increased. Damage was augmented when the soil was moist at the time of trampling. Thirty days of rest were insufficient to allow hydrologic recovery. Soil bulk density, aggregate stability, aggregate size distribution and surface microrelief were related to the soil hydrologic response of the trampling treatments. Many of the world's rangelands evolved in the presence and under the influence of grazing ungulates. However, the introduction and maintenance of domestic livestock on continuously or rotationally grazed pastures has the potential for altering botanical composition and cover (Ellison 1960) and soil physical properties (Klemmedson 1956, Reed and Peterson 1961). Modification of those parameters, either singly or in concert, may accelerate the natural erosion process and result in decreased on-site productivity, increased sediment production, and increased susceptibility of downstream flooding. As stocking rates of domestic livestock are increased under continuous year-long or season-long grazing, rainfall infiltration generally decreases while runoff and sediment loss increase (Alderfer and Robinson 1947, Rauzi and Hanson 1966, Rhoades et al. 1964). Heavy continuous grazing is generally detrimental to soil hydrologic characteristics, while the effects of moderate or light continuous grazing are significantly less deleterious and frequently not significantly different from each other (Blackburn 1984, Gifford and Hawkins 1978). Supporters of intensive rotation grazing (IRG) systems such as the short-duration grazing method propose that heavy stocking rates under some forms of rotational grazing may be advantageous Authors are presently environmental research scientist, USA-CERL, Environmental Divison,

The impact of short‐term, high intensity livestock trampling on selected properties of a silty clay soil was determined at the Texas Agriculture Experiment Station located near Sonora, TX. Intensive livestock trampling typical of multi‐pasture rotational grazing systems had a negative impact on soil physical properties. The deleterious effects tended to increase as stocking rate increased. Trampling on dry soil caused disruption of naturally occurring aggregates and compaction of the surface soil layer. Trampling on moist soil deformed existing aggregates and led to the creation of a flat, comparatively impermeable surface layer composed of dense, unstable clods.

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/ An exhaustive search of the literature for foot and vehicle traffic impacts on vegetation has yielded more than 400 citations, two thirds of which held sufficient detail to be usefully distilled into a personal-computer data base. A total of 1444 individual observations involving 737 species that were trampled are included. Compromises were made in the depth of entry detail and to allow comparability among data. Inconsistent, generally short-term, experimental practices disallowed formal statistical analyses. Within those constraints, graminoids emerged with the highest mean resistance and resilience among life-forms. Climbers and cactoids ranked lowest in these categories. The herbaceous, typically broader-leaved (forb) life-form appeared most likely to suffer immediate losses. Shrubs and trees had the longest-lasting decreases in diversity following traffic impact. All life-forms had sensitive species. The greatest general species and individual plant losses take place in the first few passes by feet, wheels, or tracks. Plant and soil damage increases with the amount of weight and power applied. Greater soil moisture and/or deeper overstory shading magnify those impacts. Additional precepts may become apparent to data-base users through increased ease in making comparisons.KEY WORDS: Vegetation; Trampling; Vehicles; Traffic; Resistance; Resilience; Data base