Seed banks may contribute useful or weedy species that fill gaps in pastures. In a previous study, pastures planted to complex mixtures of forages had a lesser proportion of weedy species in the aboveground vegetation. In this study, we relate changes in the species composition of the seed bank to changes in the aboveground vegetation. In August 2001, four mixtures [two, three, six, and nine species of temperategrasses, legumes and chicory (Cichorium intybus L.)] were established in replicated 1-ha pastures (eight total) in central Pennsylvania. Pastures were grazed by dairy cattle from April to September in 2002 and 2003. Soil cores (1.88-cm diam. by 5-cm depth) were taken in April and October in 2002 and 2003, and in April 2004 to determine the density of germinable seeds. Soil samples were placed in a greenhouse under natural light and controlled temperatures for 12 to 18 mo and germinated seedlings counted regularly. The total density of germinable seeds from all species did not differ among mixtures (P = 0.08). Annual nonleguminous forbs accounted for 79% of the germinable seeds. Yellow woodsorrel (Oxalis stricta L.) was the dominant annual forb. There were significant differences among pastures planted to different mixtures in the density of germinable annual forb seeds; however, these differences likely occurred because of preexisting spatial variation in seed bank composition. Seeded species contributed fewer than 1000 seeds m(-2) total in the 3 yr. Kentucky bluegrass (Poa pratensis L.) and white clover (Trifolium repens L.) were the most common forage species in the seed bank. There was little relation between the species composition of the seed bank and the composition of the aboveground vegetation. Data from this study indicate that previous land management had larger effects on the soil seed bank than did planting diverse mixtures of forages.

Drought is common in rangeland environments and an understanding of its impacts on the structure and function of rangeland ecosystems is paramount for developing effective management strategies. This research was the second of a series of studies investigating the impacts of varying seasonal droughts on northern Great Plains rangelands. Research was conducted on native rangeland during the 1998 through 2001 growing seasons. Study plots were twelve 5 3 10 m nonweighing lysimeters. An automated rainout shelter was used to establish drought conditions on 6 lysimeters during April, May, and June of 1998 and 1999. Single-day, flash grazing events were imposed at the beginning of May, June, and July. Grazing treatments were 1) graze during the 2 years of drought and the year after; 2) graze during the 2 years of drought and rest the year after; and 3) rest all years. Results showed that the intense spring drought reduced soil water content in the upper 30 cm of the soil profile and subsequently reduced total herbage production 20% to 40%; cool-season perennial grasses were the primary contributor to the reduction and cool-season annual grasses were secondary. Periodic grazing during drought had minimal impact on herbage production, whereas impacts on nondrought plots ranged from moderate enhancement to moderate suppression, with effects varying depending on functional group. Results also showed that substantial recovery occurred during the 1st postdrought year, with near full recovery realized within 2 years.

A 3-yr study evaluated late winter (Feb), early spring (Apr), and late spring (Jun) calving systems in conjunction with varied weaning strategies on beef cow and calf performance from Northern Great Plains rangelands. Crossbred cows were randomly assigned to one of three calving systems (on average n= 168.calving system(-1).yr(-1)) and one of two weaning times (Wean 1, 2) within each calving system. The Feb and Apr calves were weaned at 190 and 240 d of age, whereas Jun calves were weaned at 140 and 190 d of age. Breeding by natural service occurred in a 32-d period that included estrous synchronization. Cows were managed throughout the year as appropriate for their calving season. Quantity and quality of hay and supplements were provided based on forage and weather conditions, physiological state of the cows, and available harvested feed resources within a year. After weaning, two-thirds of the early weaned steers were fed in confinement in Montana, and one-third were shipped to Oklahoma and were grazed or fed forage. One-half of the early weaned heifers grazed seeded pastures, and the other half was fed in confinement. Early weaned calves were weighed on approximately the same day as late-weaned calves. Birth weight and overall rate of gain from birth to weaning did not differ for calves from the three calving systems. Calf weaning weight differed by weaning age within calving system (P = 0.001), and calves from the Jun calving system that were weaned at 190 d of age tended (P = 0.06) to be lighter than calves of the same age from the Feb or Apr calving systems. Cow BW change and BCS dynamics were affected by calving system, but the proportion of cows pregnant in the fall was not. Cows suckled until later dates gained less or lost more BW during the 50 d between the first and second weaning than dry cows during this period. The previous year's weaning assignment did not affect production in the following year. Estimated harvested feed inputs were less for the Jun cows than for the Feb and Apr cows. We conclude that season of calving and weaning age affect outputs from rangeland-based beef cattle operations.

Some producers believe that planting pastures to several forage species benefits sustainability of grazing systems. We conducted a grazing study to determine if forage species diversity in pastures affects herbage productivity and weed invasion. One‐hectare pastures were planted to four mixtures in August 2001 and then grazed with lactating dairy cattle during 2002 and 2003. The mixtures were two species [orchardgrass (Dactylis glomerata L.) and white clover (Trifolium repens L.)], three species [orchardgrass, white clover, and chicory (Cichorium intybus L.)], six species [orchardgrass, tall fescue (Festuca arundinacea Schreb.), perennial ryegrass (Lolium perenne L.), red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.), and chicory], and nine species [the six‐species mixture plus white clover, alfalfa (Medicago sativa L.), and bluegrass (Poa pratensis L.)]. When rainfall was plentiful (2003), there were no differences in herbage yield among the mixtures; all averaged 9800 kg ha−1 dry matter. During 2002, which was dry, the two‐species mixture produced less herbage than the other mixtures (4800 vs. 7600 kg ha−1 dry matter). The proportion of nonsown species in the sward was lower for the six‐ and nine‐species mixtures than the two‐and three‐species mixtures, indicating less weed invasion for these complex mixtures. Red clover and chicory proportions decreased by 80% after 2 yr, and orchardgrass dominated in all pastures by May 2004. We conclude that planting a mixture of grasses, legumes, and chicory will benefit herbage production during dry years and will reduce weed invasion for a few years after planting under management similar to ours. Producers would have to reestablish the chicory and legume components relatively frequently to maintain these benefits.

Integrating use of seeded perennial cool-season grass pastures with native rangeland can increase available forage and provide a high plane of nutrition for grazing livestock. Our objective was to compare performance of yearling beef heifers grazing native rangeland with those grazing an integrated system that included seeded forages. Twice-replicated, 3-ha pastures seeded to either ‘Rosana’ western wheatgrass (Pascopyron smithii [Rydb.] A. Love), ‘Luna’ pubescent wheatgrass (Elytrigia intermedia [Host] Nevski), or ‘Hycrest’ crested wheatgrass (Agropyron cristatum [L.] Gaertn. ssp. desertorum [Fisch. ex Link] A. Love) were grazed in spring, whereas twice-replicated, 3.24-ha pastures seeded to either ‘Alkar’ tall wheatgrass (Thinopyrum ponticum [Podp.] ZW Liu RC Wang), ‘NewHy’ hybrid wheatgrass (Elymus hoffmannii KB Jensen KH Asay), ‘Bozoisky’ Russian wildrye (Psathyrostachys juncea [Fisch.] Nevski.), or ‘Prairieland’ Altai wildrye (Leymus angustus [Trin.] Pilger) were grazed in autumn. Native rangeland was grazed during summer in the integrated system and spring, summer, and autumn in the rangeland treatment. Heifers exhibited greater weight gains on seeded pastures than on native rangeland in spring and autumn of most years. In 2 out of 3 years, heifers that grazed native rangeland during spring gained more (P = 0.012 for gain head-1 and P = 0.021 for gain head-1 day-1) while grazing native rangeland during summer than heifers that grazed seeded pastures in spring. Spring + summer gains averaged (mean +/- SE) 0.56 +/- 0.01 kg head-1 d-1 and 73.1 +/- 1.6 kg head-1. Livestock managers need to consider their livestock marketing and management strategies when using seeded pastures for seasonal grazing.

Recent environmental literature contains claims that livestock grazing has caused reduction in species diversity on Western rangelands. Data of species richness (number of species) is presented from inside and outside 24 long-term exclosures in Montana, Utah, and Wyoming. For the average of all exclosures there was no difference between species richness inside and outside the exclosures. Overlap of species (those found both inside and outside of the exclosures) was high (69 to 72 percent), and the species found either inside only or outside only did not reveal any trend related to grazing or successional status. The areas inside and outside eight exclosures in Wyoming were sampled in 2 successive years. Growing season moisture was above normal the first year and far below normal the second. Species richness sampled was more than 40 percent lower in the second year than in the first. The rather small difference in species richness inside and outside all of the exclosures indicates that neither grazing nor lack of grazing has much long-term influence on species richness. However, growing season moisture can greatly influence how many species are encountered when sampling an area.