Effect of Dung Beetles on Dung Decomposition and Nuntrient Cycling in a Nebraska Rangeland

Authors

Kenneth Shay Evans, University of Nebraska-LincolnFollow

Date of this Version

8-2016

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professor Martha Mamo. Lincoln, Nebraska: August, 2016

Copyright (c) 2016 Kenneth Shay Evans

Abstract

Management practice can have impacts on the abundance and frequency of dung beetle populations and nutrient cycling in grazing systems. Also, agriculture and livestock production land use is a considerable source of anthropogenic greenhouse gas (GHG) emissions, which are known to be one of the causes of global climate change. In this study, we evaluated the effect of dung beetle presence on the fluxes of greenhouse gasses (GHG’s) from dung pats in the semi-arid Sandhills region of Nebraska, by using closed chambers to measure the fluxes of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) from dung pats that were exposed and unexposed to dung beetles. We also quantified the effects of dung beetle activity on the timing and magnitude of decomposition of dung, and subsequent fluxes of dung derived C and N into soil. We measured indicators of dung pat decomposition, dung pat C, N, and P variables, and soil C, N, and P variables below dung pats that were either exposed or unexposed to dung beetles. Higher fluxes of GHG’s from dung pats were observed. However, while higher fluxes of CO₂ and N₂O, and lower fluxes of CH₄ due to dung pat exposure to dung beetles were observed, these effects were only significant in one experiment out of the four seasonal experiments performed. We also found that dung pat exposure to dung beetles can increase rates of mass loss in field moist dung pats, as well as rates of moisture loss. While higher concentrations of nutrients from dung pats in soil were observed, dung beetles had a minimal impact on the soil nutrient concentrations below decomposing dung pats. Environmental factors overall were much more impactful, and dung and soil nutrients, as well as GHG emissions, responded in accordance with temporal fluctuations in the environmental variables that were measured. Our study suggests that management considerations in regards to GHG emissions and nutrient cycling within subirrigated meadows of the Sandhills, might not need to offer as much concern to the effects of dung beetles as perhaps previously believed.

Advisor: Martha Mamo