The effects of stocking rate and grazing method on performance of yearling beef cattle grazing tallgrass prairies in north-central Oklahoma were evaluated from 1989 to 1994. Pastures dominated by big bluestem [Andropogon gerardii Vitman], little bluestem [Schizachyrium scoparium (Michx.) Nash], and indiangrass [Sorghastrum nutans (L.) Nash], were allocated to either short duration rotational or continuous stocking methods and stocking rates ranging from 52 animalunit-days (AUD) ha-1 to 90 AUD ha-1. Steers grazed the units from late April to late September. Precipitation was above average during the study period. Live weight gain per head was higher under continuous stocking than rotational stocking at all stocking rates. At 52 AUD ha-1 , individual gains under rotational stocking were 11% less than under continuous stocking. At 90 AUD ha-1 , individual gains under rotational stocking were decreased by 20%. Measurements of steer diets and forage standing crop suggest the reduction in weight gain was due to reduced forage intake under rotational stocking. Live weight gain per hectare increased with stocking rate and was higher with continuous stocking at all stocking rates. Net returns per hectare increased as stocking rate increased for both stocking methods but were lower for rotational stocking at all stocking rates. Variable costs per head would have to decrease by 24 to 34% under rotational stocking to equalize net returns between the 2 grazing methods. Unless the decline in gain per head can be reduced or eliminated, there is no economic incentive to implement rotational stocking under the conditions of this study.

Both carotid and intracranial chemoreceptors are critical to a normal ventilatory CO2-H+ chemosensitivity. At low levels of hypercapnia, the carotid contribution is probably greater than the central contribution but, at high levels, the intracranial chemoreceptors are dominant. The carotid chemoreceptors are also critical to maintaining a stable and normal eupneic PaCO2, but lesion-induced attenuation of intracranial CO2-H+ chemosensitivity does not consistently alter eupneic PaCO2. A major unanswered question is why do intracranial chemoreceptors in carotid body denervation (CBD) animals tolerate an acidosis during eupnea which prior to CBD elicits a marked increase in breathing.

Grazing system and stocking rate effects on standing crop of species and relative species composition of tallgrass prairies in north-central Oklahoma were evaluated from 1989 to 1993. Twelve experimental units, consisting of pastures dominated by

A key to management of short duration grazing systems is maintaining proper rest periods for individual pastures, but information on the necessary length of rest periods for tailgrass prairie is iimited. Research hypotheses for this study were that tallgrass prairie plant communities would respond differently to grazing schedules incorporating rest periods of varying lengths and that this response would be dependent on stocking rate. Treatments consisted of 3 grazing schedules (2,3, or 4 rotation cycles per 152 day grazing season) and 2 stocking rates (1.6 and 2.2 times the moderate continuous rate). Plant frequency, standing crop, species composition, and forage utilization were sampled from 1985 to 1989. Precipitation was above average in 4 of the 5 study years. Grazing schedule did not affect any vegetation parameter over time. Stocking rate did not affect plant frequency or species composition. Standhrg crop was reduced and forage utiiization increased at the higher stocking rate but these effects were consistent over time. Frequency of western ragweed [Ambrosiopsffos&c/rye DC.] and the reiative species composition of the forb component increased in all grazed pastures compared to ungrazed pastures. The overall lack of major treatment effects was attributed to favorable precipitation, spring burning, and the initial high-seral successional stage of the experimental pastures.

With recognition that historical consciousness, or "historicity," is culturally mediated comes acknowledgment that periodization of history into epochs is as much a product of cultural practice as a reflection of historical "fact." In this article, I examine popular "modernist" invocations of epoch in rural France-those positing traditional pasts against fluid presents with uncertain futures-which scholars frequently subordinate to analyses of collective memory and identity politics. Submitting this "response" to French modernity to temporal analysis reveals an additional critique in this periodization, one that valorizes enduring social time over processual temporalities, with implications for the temporal frameworks and ideology of anthropologists. [cultural rupture, enduring time, epoch, historicity, modernity, processual temporality, France]