Cattle as partners in conservation: the effects of grazing on indicators of rangeland health
Date
2018
Authors
Monlezun, Anna Clare, author
Rhoades, Ryan, advisor
Ahola, Jason, advisor
Brummer, Joe, committee member
Meiman, Paul, committee member
Turk, Phillp, committee member
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Volume Title
Abstract
For centuries, the natural ecology of rangelands has supported large herds of herbivores. The partnership between these herbivores and the land has usually been, and can continue to be a sustainable one. However, the debate over the use of public lands for cattle grazing continues to intensify. Scientific literature and corresponding recommendations regarding cattle management on rangelands are conflictual. This thesis proposes that the resolution is not to remove grazing from rangelands, but to effectively manage grazing for specific landscapes and ecosystem types. Grassland ecosystems are highly dynamic and maintained by continuous adaptation to biotic and abiotic events. Therefore, strategic grazing management that also incorporates dynamic adaptation to environmental conditions may produce successful outcomes with respect to cattle grazing and sustainable land management. The objective of this study was to compare selected indicators of rangeland health in ungrazed areas to adjacent areas where strategic grazing management had been implemented. It was hypothesized that compared to areas excluded from grazing, areas where strategic grazing was implemented would exhibit: increased nutrient cycling by integration of organic carbon and nitrogen into the soil, increased abundance of native graminoids and native forbs, and reduced abundance of noxious weeds. It was hypothesized that forage quality would follow a particular pattern because of grazing: a decrease in forage quality shortly following grazing, an increase in forage quality with a period of rest, and a decrease in forage quality with continued absence of grazing. Paired grazed and ungrazed areas were established in 6 pastures across a grassland valley on Colorado's Front Range, which had not been grazed for at least 10 years. In 2016, baseline data were collected from both grazed and ungrazed areas prior to grazing. Subsequent data were collected in 2017, following strategic grazing management and adequate rest. Linear mixed models were used to compare differences between grazed and ungrazed areas. Results indicated no significant differences in soil organic carbon (P = 0.97), total nitrogen (P = 0.64), relative abundance of native graminoids (P = 0.15) or relative abundance of forbs/subshrubs (P = 0.74) between grazed and ungrazed areas. In regards to forage quality, crude protein was lower (P = <0.01) and neutral detergent fiber was higher (P = 0.05) at the conclusion of the grazing period, but acid detergent fiber did not differ (P = 0.51) in grazed versus ungrazed areas. Additionally, areas that were grazed in the spring and received 2-3 months of rest demonstrated higher forage quality than areas that were grazed in the fall and received 9-10 months of rest as indicated by higher crude protein (P = 0.03), and a tendency for lower neutral detergent fiber (P = 0.06), but no difference in acid detergent fiber (P = 0.97). Chi-square tests for soil and vegetation variables detected no variation between pairs of grazed and ungrazed areas across the landscape. This suggested that the biological variability within and between grazed and ungrazed areas was minimal, and that the strategic grazing regime, which incorporated flexibility in grazing intensity, stocking density, and season of grazing, produced homogeneous effects across all pastures. The results of this study indicated that one year of strategic grazing does not significantly affect select soil and vegetation variables and that further study is needed in order to inform application. As part of a long-term project, this collection of data and analysis was important for the initiation of a collaborative monitoring process, which will eventually determine if strategic grazing management proves to be helpful or harmful for land management goals. Continued research will aid ranchers and land managers in developing collaborations so that cattle might serve as partners in the conservation of rangelands, while maintaining animal performance and beef production objectives. Effective livestock management is key. Therefore, the human decision-making dimension is imperative to incorporate in future grazing studies.
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Subject
collaborative conservation
human dimension
rangeland management
grazing management
cattle grazing
public lands management