Mon, Aug 02, 2021:On Demand
Background/Question/Methods
Cattle have influenced the environment in the western United States from European settlement in the 1800s. Continuous grazing has resulted in decreased biodiversity and increased vulnerability to exotic invasive plants. Limited knowledge of effective means of habitat restoration is a concern for land managers who seek to maintain these intricate systems. Consequently, there is a critical need to understand system’s response to grazing pressure, release from grazing, and how to best restore quality rangeland. Key questions include: How has the rangeland responded to heavy grazing? What are the differences in species composition, percent cover, cryptobiotic soil species, and soil microbial/fungal communities in areas that sustained grazing verses areas without grazing, and how doe climate fluctuations impact these relationships? I plan to answer these questions by exploring various changes inside and outside grazing exclosures that were established in the 1980s in Capitol Reef National Park. In 7 locations throughout the Park in 2020, I resampled shrub cover and height, herbaceous cover, and cryptogamic crust cover, having been sampled over a 7-year time frame in the 1980s. In addition, we collected soil samples for an analysis of soil microorganisms. Grazing has since been stopped at all sites but at different times.
Results/Conclusions Results from the 1980s data showed that grazing can alter rangeland communities. By altering the abundance of species, grazing influenced shifts in community composition. In addition, and more specifically, grazing appeared to change compositional stability in response to climatic pulses, such as droughts. Grazed plots tended to experience larger abundances in annual species with decreased abundance of perennial grasses. Other correlations between these vegetation shifts and climate in the grazed sites support that the climate influence on species composition is less at non-grazed sites and more at grazed sites. In some areas, such as Cathedral Valley, there was a 71% decrease in native perennial grass cover. Data from the 2020 resampling confirm these relationships, but also show that sites are becoming more similar subsequent to grazing release.
Results/Conclusions Results from the 1980s data showed that grazing can alter rangeland communities. By altering the abundance of species, grazing influenced shifts in community composition. In addition, and more specifically, grazing appeared to change compositional stability in response to climatic pulses, such as droughts. Grazed plots tended to experience larger abundances in annual species with decreased abundance of perennial grasses. Other correlations between these vegetation shifts and climate in the grazed sites support that the climate influence on species composition is less at non-grazed sites and more at grazed sites. In some areas, such as Cathedral Valley, there was a 71% decrease in native perennial grass cover. Data from the 2020 resampling confirm these relationships, but also show that sites are becoming more similar subsequent to grazing release.