Synthesis Paper: Targeted Livestock Grazing: Prescription for Healthy Rangelands

Targeted livestock grazing is a proven tool for manipulating rangeland vegetation, and current knowledge about targeted livestock grazing is extensive and expanding rapidly. Targeted grazing prescriptions optimize the timing, frequency, intensity, and selectivity of grazing (or browsing) in combinations that purposely exert grazing/browsing pressure on specific plant species or portions of the landscape. Targeted grazing differs from traditional grazing management in that the goal of targeted grazing is to apply defoliation or trampling to achieve specific vegetation management objectives, whereas the goal of traditional livestock grazing management is generally the production of livestock commodities. A shared aim of targeted livestock grazing and traditional grazing management is to sustain healthy soils, flora, fauna, and water resources that, in turn, can sustain natural ecological processes (e.g., nutrient cycle, water cycle, energy flow). Targeted grazing prescriptions integrate knowledge of plant ecology, livestock nutrition, and livestock foraging behavior. Livestock can be focused on target areas through fencing, herding, or supplement placement. Although practices can be developed to minimize the impact of toxins contained in target plants, the welfare of the animals used in targeted grazing must be a priority. Monitoring is needed to determine if targeted grazing is successful and to refine techniques to improve efficacy and efficiency. Examples of previous research studies and approaches are presented to highlight the ecological benefits that can be achieved when targeted grazing is applied properly. These cases include ways to suppress invasive plants and ways to enhance wildlife habitat and biodiversity. Future research should address the potential to select more adapted and effective livestock for targeted grazing and the associated animal welfare concerns with this practice. Targeted livestock grazing provides land managers a viable alternative to mechanical, chemical, and prescribed fire treatments to manipulate rangeland vegetation

The effects of defoliation on Bromus tectorum seed production and growth

Cheatgrass (Bromus tectorum L.) is a widespread exotic weed in the Intermountain sagebrush steppe. An annual grass, it is highly prolific and very competitive with native perennial grass seedlings. A clipping experiment carried out at two cheatgrass-dominated sites (Lincoln Bench and Succor Creek) in eastern Oregon analyzed effects of defoliation on cheatgrass seed production, investigated mechanisms of altered seed production and plant recovery, and considered the potential of defoliation as a cheatgrass control method. Treatments involved hand clipping plants at two heights (tall - 7.6-cm (T) and short - 2.5 cm (S)), two stages of phenological development (boot (B) and purple (P) stages), and two frequencies (once (1) and twice (2)), though purple stage clippings were clipped only once. Treatments were replicated in a randomized complete block design, which included a control with no defoliation. End of season seed production (seeds/m²), plant density (plants/m²), plant seed production (seeds/plant), and tiller production (percentage of plants with greater than 1 inflorescence) were estimated by sampling plants and litter from each treatment plot at the end of the growing season. Seeds were hand-collected from these samples, counted, and tested for viability. Soil moisture was measured with a TDR device in three randomly selected blocks, and averaged over the season for each treatment. End of season seed production was greater than zero for all treatments at both sites. At Lincoln Bench, all treatments excluding the TB1 treatment produced significantly less seed than the control. At Succor Creek, only the SB2 and SP treatments produced significantly less seed than the control. The SB2 treatment had the lowest seed production at both sites, at 119 and 1243 seeds/m² at Lincoln Bench and Succor Creek, respectively, along with the SP treatment at 1115 seeds/m² at Succor Creek. The response patterns for plant density and seed production of individual plants were similar to that for overall seed production, which suggests that these treatments reduced seed production by increasing plant mortality and reducing plant reproductive ability. Tiller production increased for the SB1 treatment, which suggests that cheatgrass plants were able to recover from defoliation partly through asynchronous or increased tiller development. There was no significant effect of treatment on seasonal soil moisture. In conclusion, although the SB2 and SP treatments showed the greatest reduction in seed production, plants in these treatments still produced viable seed. Thus, applying a similar defoliation treatment for seedbed preparation with livestock-assuming similar treatment effects- may not be sufficient by itself to reduce cheatgrass to levels low enough to reduce competition in native reseeding projects. Alternatively, defoliation treatments could be intensified, and/or combined with other weed control methods as part of an integrated weed management approach

Defoliation Effects on Bromus tectorum Seed Production: Implications for Grazing

Cheatgrass (Bromus tectorum L.) is an invasive annual grass that creates near-homogenous stands in areas throughout the Intermountain sagebrush steppe and challenges successful native plant restoration in these areas. A clipping experiment carried out at two cheatgrass-dominated sites in eastern Oregon (Lincoln Bench and Succor Creek) evaluated defoliation as a potential control method for cheatgrass and a seeding preparation method for native plant reseeding projects. Treatments involved clipping plants at two heights (tall=7.6cm, and short=2.5cm), two phenological stages (boot and purple), and two frequencies (once and twice), although purple-stage treatments were clipped only once. Treatments at each site were replicated in a randomized complete block design that included a control with no defoliation. End-of-season seed density (seeds m-2) was estimated by sampling viable seeds from plants, litter, and soil of each treatment. Unclipped control plants produced an average of approximately 13 000 and 20 000 seeds m-2 at Lincoln Bench and Succor Creek, respectively. Plants clipped short at the boot stage and again 2 wk later had among the lowest mean seed densities at both sites, and were considered the most successful treatments (Lincoln Bench: F6, 45 = 47.07, P < 0.0001; Succor Creek: F6, 40 = 19.60, P < 0.0001). The 95% confidence intervals for seed densities were 123–324 seeds m-2 from the Lincoln Bench treatment, and 769–2 256 seeds m-2 from the Succor Creek treatment. Literature suggests a maximum acceptable cheatgrass seed density of approximately 330 seeds m-2 for successful native plant restoration through reseeding. Thus, although this study helped pinpoint optimal defoliation parameters for cheatgrass control, it also called into question the potential for livestock grazing to be an effective seed-bed preparation technique in native plant reseeding projects in cheatgrass-dominated areas. The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Summer and Winter Defoliation Impacts on Mixed-Grass Rangeland

Combined growing- and dormant-season pasture use has potential to increase herbage harvest without causing the undesirable shift in species composition that occurs with excessive utilization. The objective of this study was to determine the effect of summer clipping on winterpastures and winter clipping on summer pastures regarding standing crop, plant community composition, and forage quality. The study was conducted from 2003–2006 at the Antelope and Cottonwood Research Stations located in the mixed-grass prairie of western South Dakota. At each location, the experimental design was a randomized complete block with three replications that included 18 clipping treatments arranged as a split-split plot. Whole plots consisted of four summer clipping dates (May–August). Subplot treatments were two clipping intensities (clipped to residual height to achieve 25% or 50% utilization). Sub-subplots consisted of two winter clipping intensities (unharvested or clipped to a residual height to achieve a total utilization of 65%). Two winter control treatments were arranged in the subplot and split into two clipping intensities of 50% and 65% utilization. Winter biomass for the May 25% clipping treatment was similar to winter biomass for winter-only clipping. No increase in forage quality resulted from summer clipping compared with winter clipping. Three consecutive yr of combined growing-season and dormant-season defoliation to 65% utilization resulted in no change in functional groupcomposition compared with ≤ 50% utilization treatments. Clipping in June resulted in reduced midgrass biomass at both stations and increased shortgrass biomass at Cottonwood. Results suggest that producers could combine growing and dormant-season grazing to increase the harvest of herbage on mixed-grass prairie, but should change season of use periodically to avoid an undesirable shift in plant composition