Cattle Exclusion Research Articles

Short-Term Response of Riparian Vegetation to 4 Grazing Treatments

The Sheep Creek watershed of northcentral Colorado provided an ideal site to collect baseline trend data and to estimate foliar cover responses of montane riparian vegetation. Percent relative cover data were compared with Sorensen's similarity index and were analyzed with a 2-stage nested analysis of variance (ANOVA) to assess differences among 4 grazing treatments: long-term grazing (G), protection from livestock grazing since 1956 (P), recent protection following long-term grazing (P88), and recent livestock grazing following protection (G88). This study utilized 3 replications of each treatment. Data were collected in August 1988, June 1989, and August 1989, employing permanent and randomly placed transects and plots. When percent foliar cover means were paired using Sorensen's similarity index, long-term grazing and short-term grazing treatments were least similar in August 1988. Long-term protection and short-term grazing were most similar in June 1989. Average percent cover of bare ground, common dandelion (Taraxacum officinale Wiggers), white Dutch clover (Trifolium repens L.), and legumes grouped as lifeforms were significantly different among treatments, with long-term grazing being significantly different from long-term protection. Average sedge and forb cover was least affected. However, responses of individual sedge species varied with treatments. Average percent grass cover increased under short-term protection after a history of long-term grazing. Short-term grazing stimulated foliar cover of forbs, grasses, and sedges after more than 30 years of cattle exclusion.

Differences in Riparian Vegetation Structure between Grazed Areas and Exclosures

The valuable role that healthy riparian ecosystems play in regional diversity of plant and wildlife communities is just beginning to be recognized. Resource managers need to know how degraded riparian areas respond to changes in management, such as reduction and elimination of grazing. Differences in vegetation structure were examined in a montane riparian zone in northcentral Colorado after 30 years of cattle exclusion and continued, but reduced, grazing pressure. In order to assess the changes in the riparian community, canopy coverage, density, and standing crop of important riparian species were measured in 1985 and 1986. Total vascular vegetation, shrub, and graminoid canopy cover was greater (P?0.05) in the exclosures as compared to grazed areas, while forb canopy cover was similar (P>0.05) between treatments. Exclosures had nearly 2 times the litter cover, while grazed areas had 4 times more bare ground. Willow canopy coverage was 8 1/2 times greater in protected areas than in grazed areas. Kentucky bluegrass (Poa pratensis L.) cover was 4 times greater in grazed areas than exclosures, while the cover of fowl bluegrass (Poa palustris L.) was 6 times greater in the protected sites. Canopy cover of other important riparian species, such as tufted hairgrass (Deschampsia caespitosa (L.) Beauv.), Nebraska sedge (Carex nebraskensis Dewey), and beaked sedge (C. rostrata Stokes), was similar (F>0.05) between treatments. Mean peak standing crop over the 2 years of the study ws 2,410 kg/ha in the exclosures and 1,217 kg/ha in caged plots within grazed areas. Cattle utilized approximately 65% of the current year's growth of vegetation during the 1985 and 1986 grazing seasons. Riparian areas provide habitat for wildlife and fish species, while providing forage for domestic livestock. These areas provide a diversity of foraging and breeding sites that permit coexistence of many wildlife species. Intact aquatic ecosystems with abundant streamside vegetation insure healthy fish populations (Kauffman and Kreuger 1984). Improper livestock use of riparian areas can increase erosion and reduce plant vigor, resulting in lowered forage production and altered plant age structure and species composition (Knopf and Cannon 1982, Kauffman and Krueger 1984, Skov

Preovulatory exclusion of inferior embryo donor cattle by means of sequential plasma hormone determinations

Thirty-one cycling heifers were superovulated and subsequently ovanectomized to determine if preovulatory follicles could be induced to ovulate by the administration of cloprostenol, a potent agonist of prostaglandin F2α. Superovulation was induced, during the mid-luteal phase, with a total dose of 20 mg porcine pituitary extract of follicle stimulating hormone (FSH) given twice daily over 4 days in decreasing doses; a luteolytic dose of cloprostenol was administered on the third day. Two experiments were carried out in which ovariectomies (OVX) were performed at 64 h following cloprostenol injection. Owing to the variable interval between the preovulatory peak of luteinizing hormone (LH) and OVX observed in Experiment I, the preovulatory LH surge was induced in Experiment II by 100 μg of a synthetic analogue of gonadotropin releasing hormone (GnRH) given 36 h after the luteolysin. To test the hypothesis that cloprostenol is able to induce, enhance or synchronize ovulation, two different doses of this hormone, 1.25 or 2.5 mg, were injected at 4 and 2 h or at 2 and 1 h prior to OVX. Plasma progesterone (P4) and LH concentrations and follicular fluid P4: estradiol-17β (E2) ratios in the non-ovulated follicles were utilized to identify animals that had a typical response to the superovulatory treatment and, at OVX, total number of follicles 8 mm or more in diameter, and number of ovulations were recorded. When data from both experiments were considered, it was observed that: (1) GnRH injection did not affect ovulation rate; (2) cloprostenol injections induced more follicles (P < 0.01) to ovulate, 59.3% vs. 20.1%, SE = 9.8, in cloprostenol-treated vs. controls, respectively, at the time tested; (3) cloprostenol dose had a positive linear effect (P < 0.01) on ovulation rate. In conclusion, the data suggest that prostaglandin F2α or its analogues could be used to induce a more synchronous ovulation of follicles in superovulated heifers.

Use of fertilization and grazing exclusion in mitigating lost meadow production in the Sierra Nevada, California, USA

The effects of a single fertilizer treatment (ammonium phosphate at 841 kg/ha, plus dolomite at 336 kg/ha) and cattle exclusion were studied in two meadows in the Sierra Nevada of California in the USA. Grazing exclusion had no effects on soil bulk density during the three years of the study. Fertilization had no effect on total soil nitrogen, soil pH, or crude protein concentrations in graminoids or forbs. Saturated soils and the development of anaerobic conditions close to the surface may have led to denitrification and the loss of usable nitrogen. Fertilization did result in short-term (one- to two-year) increases in available soild phosphorus in the drier of the two meadows, and in total phosphorus concentrations in graminoids and forbs, which were otherwise generally deficient in phosphorus. Few changes in plant species composition or production were detected, although a combination of fertilization and grazing exclusion increased forb production in the drier meadow. Based on our initial results, fertilization with phosphorus was the recommended treatment for meadow improvement projects in the central Sierra Nevada.

Influence of Cattle Stocking Rate on the Structural Profile of Deer Hiding Cover

Hiding cover available for California (Odocoileus hemionus californicus) and Rocky Mountain (0. h. hemionus) mule deer was monitored during summer under no, moderate, and heavy cattle stocking rates in quaking aspen (Populus tremuloides) and meadow-riparian habitats in the central Sierra Nevada, California. Use of willow (Salix spp.) and herbaceous vegetation in meadow-riparian habitat was also measured using exclosure plots. Hiding cover in aspen and corn lily (Veratrum californicum) vegetation types was not reduced through mid-season in ungrazed treatments but was significantly (P < 0.05) reduced under moderate and heavy grazing. Increases in cover of aspen understory were detected after 2 years of cattle exclusion. Willow vegetation was resilient to the impacts of cattle under moderate grazing, but hiding cover was significantly (P < 0.05) reduced with heavy stocking rates. Browsing of willows by deer was light in ungrazed treatments but increased as the season progressed in cattle-grazed areas and as stocking rate increased. Natural weathering was partly responsible for overall hiding cover lost during the summer but reductions prior to mid-summer were attributed to cattle. The high proportion of hiding cover lost early in the season coincided with the 1st 2 months of life for fawns. J. WILDL. MANAGE. 51(3):655-664 The structure of vegetation provides important thermal and hiding cover for California and Rocky Mountain mule deer in the Sierra Nevada Mountains, California. An overstory canopy assists deer in minimizing energy expenditure for thermoregulation by creating a microclimate that buffers extreme weather conditions (Leckenby 1977, Peek et al. 1982). Understory vegetation provides relief from the weather for ungulate species that inhabit dense shrub or forest environments but is more important in providing deer with valuable hiding cover to escape danger (Taber 1961). Mule deer are regarded as classic hiders (Geist 1981). Most susceptible to predation are neonatal animals, which have not fully developed the coordination or speed for flight and are therefore dependent upon cover for escape. High rates of predation on deer fawns in the 1st 2 months of life have been reported in several studies (Cook et al. 1971, Salwasser 1974, Trainer 1975). Bowyer and Bleich (1984) suggested that lack of suitable cover due to cattle grazing may contribute to reduced fawn survival because of increased susceptibility to predation. Similarly, Smith and Lecount (1979) found that survival of fawns was influenced by vegetation because increased cover reduced predation. Pronghorn (Antilocapra americana) fawn survival has also been found to be higher on sites with more cover (Barrett 1981). Hamlin et al. (1984) concluded that poor hiding cover did not appear to be a factor in fawn mortality because fawns shifted habitat use to maintain adequate cover. Riley and Dood (1984) also reported that mule deer fawns selected habitats with dense vegetative cover. Hiding cover contributed significantly to habitat use by black-tailed deer (0. h. columbianus) in northern California (Loft and Menke 1984), and may be required even in the absence of predation risk if full use of a habitat is to occur (Black et al. 1976). The long history of livestock grazing in the western states has altered vegetation structure and species composition considerably from pristine conditions (Wagner 1978). Cattle are credited as having both detrimental (Mackie 1978) and beneficial (Urness 1976, Longhurst et al. 1982) effects on deer through their impact on plant communities. The overstory canopy is relatively free from the effects of cattle on a shortterm basis. Over several years though, regeneration and survival of young trees and vigor of mature trees can be adversely affected by browsing, trampling, soil compaction, trunk damage, and nutrient accumulation. However, understory vegetation, which provides the majority of wildlife hiding cover, can be affected by livestock grazing and trampling on a seasonal basis every year. On summer ranges, cattle and

Impact of SO 2 Exposure on the Response of Agropyron smithii to Defoliation

Agropyron smithii populations exposed to 3 controlled SO2 concentrations were defoliated either once or twice during the growing season at a light and a heavy intensity. The intensity and frequency of defoliation were most influential in determining growth and tillering responses. Defoliating twice, at either intensity, had a large negative impact on plant growth whereas compensatory growth occurred after defoliating once at either intensity. Sulfur dioxide alone had no significant effect on biomass or the number of tillers, even though sulfur accumulated approximately in proportion to exposure concentration. Sulfur dioxide exposure with the additional influence of defoliation affected both the regrowth of A. smithii in terms of biomass and tiller numbers and forage sulfur concentration. Decreased plant growth in response to SO2 plus defoliation was dependent on defoliation frequency, whereas the effect of SO2 plus defoliation on plant sulfur concentration was positive and negative and depended on a complex interaction of SO2 concentration and defoliation frequency and intensity. The results are discussed in relation to the shortand long-term compensatory growth potential of a system simultaneously exposed to grazing and air pollution and the potential effect on consumers. During the first 4 years of a field experiment designed to investigate the response of a native North American grassland to controlled low concentrations of sulfur dioxide, it was observed that exposures during the growing season had subtle, but potentially important effects upon the system (Lauenroth and Heasley 1980). For example, exposure of Agropyron smithii Rydb. to S02 reduced chlorophyll concentration (Lauenroth and Dodd 1981), increased sulfur concentration (Lauenroth et al. 1979, Milchunas et al. 198 la), decreased the functional lives of leaves (Heitschmidt et al. 1978, Milchunas et al. 198 lb), and decreased the amount of labile carbon stored in the rhizomes (Lauenroth and Heasley 1980). Regrowth of A. smithii in the spring or after defoliation is thought to be dependent upon carbohydrates stored in rhizomes and roots (Bokhari 1977). Before the SO2 treatments were begun the area had been grazed by cattle. Following exclusion of cattle, a significant year to year increment in rhizome biomass was observed on the control plot. This was interpreted as an indication of recovery from grazing. B3y contrast, rhizome biomass failed to recover on the 170 ,Ag . mSO2 treatment. This suggested that, although the mechanisms by which SO2 exposure and grazing effect plants are different, the response of the plants to SO2 or grazing may be similar and/or additive. Populations under stress are often considered to be more susceptible to damage caused by additional perturbations. Because of the importance of these grasslands to the livestock economy of the northern Great Plains and the high probability that coal combustion for electric power production will increase in this area, a field experiment was conducted to examine the potential interactions between defoliation and SO2 exposure on the native vegetation. The hypothesis was that defoliation would be more detrimental to Authors are associate professor, Range Science Department, and Natural Resource Ecology Laboratory; associate director, Natural Resource Ecology Laboratory, and associate professor, Range Science Department; research associate, Natural Resource Ecology Laboratory, Colorado State University, Fort Collins; and professor, Range Management Division, University of Wyoming, Laramie. Manuscript accepted April 30, 1984. regrowth of A. smithii populations which had been exposed to S02 for 4 years than to populations not exposed to SO2.

The ecology of the Bogong High Plains. II. Fencing experiments in grassland C

A 10-year fencing experiment in the eroded grassland, type C, of the Bogong High Plains has established the value of the point analysis method for the quantitative study of continuing change in vegetation. The results show that the exclusion of cattle from this widespread type of subalpine grassland results in a gradual improvement in the amount of vegetative cover, especially in that provided by the herb Celmisia. Over the 10-year period there have been striking soil changes in the fenced plot, resulting in an increase in organic matter and in field capacity, and a significant decrease in bulk density. These findings enable one to make recommendations on catchment management in this area. They have also led to the hypothesis that the eroded grassland has been derived from a herb-field similar to that still existing in the higher parts of the area.

The incandescent electrical lamp decided to be Edison's invention

Unrestricted cattle access to pastoral wetlands can result in increased pollutant loads from agricultural areas. We quantified the time a herd of dairy cattle spent grazing a pastoral headwater wetland and its associated impact on water quality. Over a two year period a herd of ∼220 dairy cattle rotationally grazed a paddock containing a permanently saturated pastoral wetland. Flow and turbidity were continuously monitored at a v-notch weir and baseflow and event samples were collected and analysed for TSS, Escherichia coli and various forms of N and P. Cattle were detected grazing the wetland paddock on 18 days by time-lapse cameras. Cattle only entered and grazed the saturated wetland area for 30–40% of the time and there were usually only a few animals in the wetland at one time. Cattle that did graze the wetland tended to remain near the edge. We attribute the low level of wetland grazing to the cattle recognizing the risk of entrapment in the deep (up to 2 m), boggy wetland soil. A measurable increase in pollutants (attributable solely to cattle generated disturbance) occurred only once. This occurred when a cow became entrapped in close proximity to the water quality monitoring location on a day when wetland flow was elevated. Exclusion of cattle from our study wetland by fencing is therefore unlikely to substantially improve downstream water quality. Further research is required to determine whether this is the case for similar wetlands in different environments.