Abstract Detail

Ecology

Rosburg, Thomas [1].

Effects of cattle grazing on the species composition of prairie communities in northwest Iowa.

Kirchner Prairie is a 158-acre site in northwest Iowa near Spencer owned and managed by the Iowa Department of Natural Resources. Grazing is considered to be an important environmental factor in grassland and prairie management, and interest in using cattle as a surrogate for native mammalian grazers is increasing. This 4-year study investigated the role that low intensity cattle grazing could have in prairie management. Eight blocks, each containing a control (within an exclosure) and grazed plot, were established at Kircher Prairie in July 2012. The blocks were balanced between the east and west halves of the prairie, which reflects a difference in land use history when it was privately owned. The blocks were also distributed among 3 burn units for the site. Baseline data on the species composition of the prairie communities was collected in July and August 2012. Cattle grazing commenced in May 2013 and continued in 2014 and 2015 from May to September. The plots were resampled in 2014 and at the end of the study in 2016. Species composition was measured in 10x30 m plots, each with 3 2x30 m belt transects (for shrubs) and 15 1x1 m quadrats as well as 60 25x25 cm subquadrats for herbaceous layer species. Plant species abundance was measured with absolute frequency and ramet density. Statistical analyses with two-way repeated measures ANOVA and paired two sample tests were used to compare 2012 baseline vegetation with 2016 vegetation. DECORANA ordinations were used to evaluate the variation in community composition over the 4-year study. Variables analyzed included over 30 variables reflecting prairie diversity, structure and quality, the density of 57 plant species and genera, and several variables that measured the dissimilarity in species composition among samples from the ordination. There were 180 plant species observed on the plots. Many of the variables demonstrated either land use history effects, treatment effects, or treatment by history interactions. Significant outcomes attributed to grazing included an increase in the density and frequency of non-native grasses, a decrease in the conservatism of native graminoids, an increase in the richness of high conservative native herb species, and a decrease in the mean weighted conservatism for all species. Five species or genera increased under grazing, while four species were indicated as grazing decreasers. A far greater number of plant species, 43 in total, exhibited no effect of grazing.

1 - Drake University, Biology Dept, Olin Hall, 2507 University Ave, Des Moines, IA, 50311, USA

Keywords:
cattle grazing
Iowa
tallgrass prairie
ramet density
frequency
species composition
community structure.

Presentation Type: Oral Paper
Session: 7, Ecology Section - Community Interactions and Responses
Location: 106/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 10:30 AM
Number: 7008
Abstract ID:883
Candidate for Awards:None