31 research outputs found
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Botanical composition and diet quality of beef cattle grazing at three stocking rates following fuels reduction in mixed conifer forests
Due to the increasing cost and concern of catastrophic wildfires in the Western United States, there is an increasing interest in fuels reduction projects. Fuel reduction treatments utilize various methods of thinning and/or prescribed fire to obtain desirable forest stand conditions. However, the effects of fuels reduction on ecosystem function are not well known. To explore the effects of fuel reduction, a series of studies have been developed. One of these studies was designed to look at how cattle diets are affected by fuels reduction and stocking rate. The study occurred at the Starkey Experimental Forest and Range in Northeast Oregon. A split plot factorial study design was used, with the whole plots (3 ha) being fuel reduced or no treatment (extant) and the split plots (1 ha) within grazed to three levels of forage utilization; (1) 3 cows/ha, (2) 6 cows/ha, (3) 9 cows/ha, with a 48 hour grazing duration. Grazing treatments were applied in August of 2005 and 2006. Cattle dietary composition information was collected from six cows in each experimental unit (1 ha) using the bite-count method with 20 minute grazing bouts. Masticate samples were collected after each 20 minute grazing bout from six ruminally cannulated cows in each experimental unit in order to determine diet quality. Masticate samples were analyzed for CP, ADF, NDF, and invitro digestibility. Preliminary results indicate foraging efficiency of cattle decreases with increased stocking rates along with an increase in shrub use across both treated and untreated sites. The results of this study will be used as part of a larger, long-term study that will provide information and models on the interaction of ungulate herbivory and episodic disturbance that will help inform and guide the management of multi-use forests
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Species Composition and Diversity on Northwestern Bunchgrass Prairie Rangelands
Management and conservation of rangelands are increasingly concerned with maintaining productivity, species composition, and diversity of native plant communities. We estimated aboveground annual productivity, species composition, and diversity of a native bunchgrass type community across 1152, 0.5 m2 plots at The Nature Conservancy’s Zumwalt Prairie Preserve in northeastern Oregon. Standing crop was estimated by clipping current year’s crop to ground level and canopy cover was estimated visually as cover classes. The Shannon diversity index (H) was used to characterize species diversity in the study area. Across the study sites 186 plant species were observed, approximately 80% of which were native perennial species. Native bunchgrasses and perennials contributed nearly 80% to the total standing crop with 16% attributed to invading and/or introduced species. We found that the prairie was low in productivity but high in evenness of species abundance
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Changes in Forage Quantity and Quality with Continued Cattle Grazing in a Mountain Riparian Pasture
The objective of this study was to evaluate changes in the quantity, quality, and moisture of available forage in a riparian pasture, and shrub utilization by cattle during a 30-d late summer grazing period. A riparian pasture (44.7 ha) in northeast of Oregon was grazed with 30 yearlings (419 kg, BCS = 5.05) and 30 mature cows with calves (499 kg, BCS = 4.65) from early August to early September in 2001, and from late July to late August in 2002. Sampling dates were d 0, d 10, d 20, and d 30. The forage availability before grazing was 1058 kg/ha and declined to 323 kg/ha at the end of the grazing period (P 0.10). In contrast, the moisture content of grasses were over 50% at the beginning of the grazing period and declined to 34% by d 20. Likewise, forbs and shrubs were higher than grasses in CP (11, 14, and 6%, respectively) and IVDMD (58, 49, and 42% respectively). In summary, our results suggest that cattle grazing late summer riparian pastures will switch to intensive shrub utilization when grasses decline in quality and quantity, and forbs decline in quantity
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Estimating Shrub Forage Yield and Utilization Using a Photographic Technique
We assessed a photographic technique to estimate shrub yield and utilization of common snowberry, snowbrush, and heart-leafed willow found in mixed-conifer rangelands. We determined the correlation between green leaf area size (LA) and forage yield (Y) and compared plant utilization estimated by photographic technique (ULA) to actual utilization (UY) values. Shrub forage yield and utilization were determined by hand plucking in five to eight increments. Before the first plucking, and after each subsequent plucking, we took two photos that were perpendicular to each other at the intersection of the shrub. Each photo was evaluated using image-processing software to produce red (R), green (G), and blue (B) color band images. Green leaf area was determined as follows: pixel = ([G-R] + [G-B])/ (G+R+G+B); Green leaf area, cm2 = (Calibration [C], cm2∙pixel-1) × (LA, pixel). Green leaf area calculated from the photographic technique was strongly correlated (r2 = 0.83-0.94, P < 0.001) with forage yield for all three shrubs. A strong correlation (r2 = 0.95, n = 142) was detected between utilization values estimated through green leaf area size and actual values. Utilization estimated by LA did not differ (P = 0.60, n = 142) from actual utilization values. In summary, our results indicate the photographic technique could be used once calibration curves are developed, to measure available browse yield and utilization of shrubs in a nondestructive approach
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Diet composistion, dry matter intake, and diet overlap of mule deer, elk, and cattle
Mule deer (Odocoileus hemionus), elk (Cervus elaphus), and cattle share rangelands throughout much of interior western North America. Considerable debate exists about the degree to which facilitation or competition occurs for forage between these three species (Nelson 1982, Wisdom and Thomas 1996, Miller 2002). Prior cattle grazing can have beneficial effects on elk nutrition. The removal of forage by cattle can improve forage quality by enhancing regrowth of forage or by changing ratios of live to dead plant material (Cook 2002), and forage quality on elk winter ranges in the interior Northwest can be improved by cattle grazing in the spring (Anderson and Scherzinger 1975, Clark 1996). To date, however, studies have not shown enhancement of forage quality in the summer following late spring or early summer grazing by elk or cattle.
Competition for forage between mule deer, elk, and cattle is probably greatest on winter and spring/autumn ranges (Nelson 1982, Wisdom and Thomas 1996), and minimal between wild ungulates and cattle during summer (Miller 2002). Most summer ranges for mule deer and elk are on large areas of public land containing a diversity of habitats and high potential for forage production (Miller 2002). On some summer ranges, however, competition for forage may exist in late summer and early fall because forage quality can be poor and not meet nutritional requirements of wild ungulates and cattle (Torbit 1985, Hanley et al. 1989, Cook 2002). This is especially evident in regions where summer drought is the normal part of the climatic regime (Vavra and Phillips 1980, Svejcar and Vavra 1985).
On the Starkey Experimental Forest and Range (Starkey), northeast Oregon, competition for forage may occur in late summer among all three species, especially between elk and cattle (Coe et al. 2001, Stewart et al. 2002). Conditions at Starkey typify those on summer ranges shared by mule deer, elk, and cattle in forests of the interior western United States. Consequently, we conducted a manipulative experiment on Starkey summer range to evaluate the potential for competition or facilitation for forage among mule deer, elk, and cattle in grand fir (Abies grandis) forests. Our specific objectives were to determine diet composition, dry matter intake rates, and percent dietary overlap of all three species in response to prior grazing by elk and cattle. In this paper we focus on results obtained from the bite count data. A detailed analysis of the nutritional consequences of previous grazing by elk or cattle on subsequent diets of mule deer, elk, or cattle will be presented elsewhere (Damiran in prep.). Results from
our study could improve range management for mule deer, elk and cattle on public land, especially with regards to allocating forage among these three species when ranges are shared in forested habitats (Ager et al. 2004)
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Influence of previous cattle and elk grazing on the subsequent quality and quantity of diets for cattle, deer, and elk grazing late-summer mixed-conifer rangelands
A study was conducted to determine foraging efficiency of cattle, mule deer, and elk in response to previous grazing by elk and cattle. Four enclosures, in previously logged mixed conifer (Abies grandis) rangelands were chosen, and within each enclosure, three 0.75 ha pastures were either: 1) ungrazed, 2) grazed by cattle, or 3) grazed by elk in mid-June and mid-July to remove approximately 40% of total forage yield. After grazing treatments, each pasture was subdivided into three 0.25 ha sub-pastures and 16 (4 animals and 4 bouts/animal) 20 min grazing trials were conducted in each sub-pasture using four steers, four tame mule deer (deer), or four tame elk during August 1998 and 1999. A bite-count technique was used to determine foraging efficiency and composition of diet. Crude protein content of deer diets tended to be higher (P 0.20) by previous grazing, but diet ADF, NDF were lower (P 0.10) intake rates of deer and elk. In response to cattle grazing, cattle and elk diets shifted to more (P < 0.10) forbs and shrub/trees. In response to elk grazing, cattle consumed more grasses; whereas elk consumed more (P < 0.10) grasses and shrub/tree. Deer increased (P < 0.10) shrub/tree intake in previously grazed pastures. This study suggests that early summer grazing by cattle or elk has very little effect on the subsequent foraging efficiency of deer and elk. In addition, early summer grazing by cattle improve the quality of subsequent elk diets, but previous grazing by elk may reduce subsequent diet quality for cattle, deer, and elk
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The Influence of Cow Age on Botanical Composition of Diets in Mixed Conifer Mountain Riparian Areas and Adjacent Uplands
The objective of this study was to evaluate the effect of cow age on botanical composition of diets in mountain riparian areas. Treatments consisted of 30 first calf heifers, and 30 mature cows randomly assigned to four pastures (2 pastures/treatment, average 21.5 ha) in a two-year study with a cross over design. Botanical composition of diets was determined in fecal samples obtained from 10 animals in each treatment from d 36 to 39 of a 42-day grazing period using microhistological techniques. The crude protein (CP) content and in vitro dry matter digestibility (IVDMD) were determined, and correction factors were calculated for 22 major plant species. There was no between age class differences in the total number of plant species in the diet (P >0.10) than for heifers. Heifers consumed more (P 0.10) except for western needlegrass (Stipa occidentalis) (P < 0.10). The diet proportion of ponderosa pine needles (Pinus ponderosa) was significantly different between age classes across the study years with consistently being found more in the diet of mature cows (P < 0.10). In summary, mature cows appeared to have selected a diet that contained less grass species and more shrubs and trees compared to younger cows
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Understory production of transitional forested rangelands in the Blue Mountains of Eastern Oregon
The objective of this study was to quantify understory vegetation response to overstory manipulation of Blue Mountain eco-region forest. Forty nine ecological land units, including differing successional stages (sapling, pole, small saw, and saw log) and canopy cover (light and medium) in dry Grand Fir (Abies grandis), wet Grand Fir, dry Douglas Fir (Pseudotsuga menziesii), wet Douglas Fir, Ponderosa Pine (Pinus ponderosa) habitat types, and non-forest communities (Wet Meadow, Riparian Grass, Grassland, and Scabland) were sampled with 3 to 15 replicates per ecological land unit for production by species over 3 consecutive years. Production ranged from 799.9 to 1050.6 kg/ha for forest communities and from 686.5 to 3534.5 kg/ha for non-forest communities. Within forest communities, wet Douglas Fir habitats had lower production (P 0.01). Light and medium densities of overstory canopy cover did not influence (P > 0.01) understory production, except light covered wet Grand Fir having greater production (P 0.01) between successional stages, although later successional stages of wet Douglas Fir habitats declined in grasses and forbs with an increasing shrub component. In summary, overstory manipulation changes understory vegetation by increasing grasses and forbs in dry and wet environments of Grand Fir and in dry Douglas Fir communities, but did not influence other habitat types
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Species diversity in understory vegetation of transitional forested rangelands in the Blue Mountains of Eastern Oregon
The objective of this study was to quantify understory species diversity response to overstory manipulation of Blue Mountain eco-region forest. Forty nine ecological land units, including differing successional stages (sapling, pole, small saw, and saw log) and canopy cover (light and medium) in dry Grand Fir (Abies grandis), wet Grand Fir, dry Douglas Fir (Pseudotsuga menziesii), wet Douglas Fir, Ponderosa Pine (Pinus ponderosa) habitat types, and non-forest communities (Wet Meadow, Riparian Grass, Grassland, and Scabland) were sampled for production by species with 3 to 15 replicates per ecological land unit, over 3 consecutive years. The Shannon diversity index (H) was used to characterize species diversity in a community. Species diversity (H) and evenness (EH) for forest communities ranged from 1.61 to 1.96 and from 0.61 to 0.68, respectively. Wet Grand Fir habitat type had higher diversity (P 0.01) in species diversity and evenness, ranging from 1.46 to 1.62 and from 0.54 to 0.67, respectively. Although dry and wet environments did not influence (P > 0.01) Douglas Fir understory diversity, wet Grand Fir habitat type tended to be more diverse. Early successional stage in forest habitats had higher (P 0.01) diversity of understory vegetation. Diversity in recently logged habitats was not different (P > 0.01) from other successional stages. In summary, diversity of forest communities was influenced by overstory manipulation with greater diversity in early successional stages
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Visual Obstruction: Weight Technique for Estimating Production on Northwestern Bunchgrass Prairie Rangelands
The estimation of standing crop is important in the management of rangeland resources. Direct measurements by clipping, drying, and weighing of herbaceous vegetation are time-consuming and labor-intensive. Therefore, non-destructive methods for efficiently and accurately estimating standing crop are needed in rangeland forage management. We assessed a visual obstruction (VO) technique to estimate standing crop (SC) of northwest native bunchgrass communities at The Nature Conservancy’s Zumwalt Prairie Preserve in northeastern Oregon. This method involves obtaining a height-density index by measuring the height of a pole that is obscured by vegetation when viewed from the side. Five hundred seventy six plots (0.5 m2) were subjected to VO measurement; and subsequently, all vegetation within a plot was clipped to ground level. Only current year’s crop was taken. Regression analysis was used to evaluate the relationships of VO to standing crop, with standing crop as the dependent variable. Total standing crop was 1261 ± 51 kg∙ha-1 and mean of VO measurement was 12.8 ± 0.4 cm for vegetation in the study site. By growth habit of plants, standing crops were 688 ± 26, 13 ± 26, 416 ± 26, and 144 ± 26 kg∙ha-1 for grasses, grasslikes, forbs, and shrubs, respectively, and all growth habits differed from each other (P < 0.01). A positive (P < 0.01) linear relationship occurred between VO and SC measurements, however, correlation was low with only 46% of the variation in standing crop being attributable to VO (y, kg∙ha-1 = 270.58 + 77.66x, cm; r2 = 0.46, n = 576). In heterogeneous mid-height bunchgrass communities like the Zumwalt Prairie Preserve, the VO technique will not accurately predict standing crop although many wildlife investigators will still find it useful for describing vegetative structure in these communities. Consequently, we recommend that, if considering VO as a surrogate for SC, investigators should calibrate VO technique against clip plots to evaluate applicability to their situation