February 27, 2020

5:00pm 1100 TLSB

EcoEvoPub Series

" Graduate Student Presentations "

CASEY YOUNGFLESH

Department of Ecology and Evolutionary Biology,

Tingley Lab, UCLA

 

“Large-scale phenological dynamics of North American birds”

 

In seasonal environments, the timing of ecological events (known as phenology) plays a critical role in ecosystem functionality. Phenological changes have been observed across a number of ecological systems in recent years, yet much remains unknown, particularly with regard to how these changes vary over space and across species. Using large-scale observational data from both eBird, a community science platform, and MAPS, a continental-scale bird banding program, I estimated phenological metrics for over one hundred migratory forest dwelling songbird species across eastern North America over the last several decades. Hierarchical Bayesian spatial autoregressive models were used to evaluate phenological change over time and the degree to which these changes are due to earlier springs, as defined by vegetation phenology. I found that

across the species assemblage, both bird arrival and breeding are advancing in response to earlier vegetation ‘green-up’. This phenological sensitivity however varies across species’ ranges and is generally stronger for species that overwinter further south. Additionally, I found that migration and breeding phenology are changing at different rates, which has effectively led to a compression of the interval between these events over time. Results have implications for better understanding phenological responses under global change and what this might mean for phenological mismatch dynamics, whereby species are temporally out of sync with favorable environmental conditions.

 

EVAN DOUGHTY

Department of Ecology and Evolutionary Biology,

Van Valkenburgh Lab, UCLA

 

“Modeling the Entrainment of Bison Cranial Material During the Missouri River Flood of 2011”

 

A mathematical model was developed for estimating transport and accumulation of a sub-fossil bison assemblage discovered within the Missouri River south of the Oahe Dam, SD in late September of 2011. This assemblage, considered to be a byproduct of the 2011 flood of the Missouri River, was comprised of disarticulated skeletal material dispersed within an interstream sediment bar of poorly sorted, subrounded fluvial sediments. A total of twenty-four bison skulls were measured using five parameters which were used to calculate the volume of each skull. Volume was then approximated as a sphere of equivalent volume and density as a bison skull. Flow measurement data from 1/2/2002 to 2/13/2014 were acquired from the US Army Corps of Engineers Oahe Dam office. Channel area and perimeter was determined using the sediment range at river mile 1069.68, and gauge height data from USGS hydrologic station 064440000. Flow velocity was determined for each record by dividing discharge rate by the channel area. Once determined, the flow velocity was used to calculate the Reynolds number for each skull. Reynolds number was then utilized in determining the drag and lift forces. Discharge rates required to entrain a given skull sphere, were determined by calculating the lift and drag forces against the force of gravity. Results indicated a discharge rate of 6345 m^3/s was required for the vertical component of force to overcome gravity. This indicated that no vertical entrainment was possible given measured discharge rates. However, it was determined that horizontally oriented entrainment was possible in 4 of the 3353 records used in the analysis.