Events & Media

The Bren School of Environmental Science & Management
at the University of California, Santa Barbara

Presents

A PhD DISSERTATION DEFENSE

"Landscape Effects on Crop Pollination Services"

Lorena Vieli
PhD Candidate
Bren School of Environmental Science & Management

Monday, March 3, 2014
3:00 p.m.
Bren Hall 1414

Frank Davis, faculty advisor
Bruce Kendall (Bren School), Miguel Altieri (UC Berkeley), PhD committee members

Abstract
Animal-mediated crop pollination is an essential ecosystem service for the production of 75% of globally important crops. In intensive agricultural production systems, this service is usually provided by managed honeybees, but wild bees are natural providers of this service and can enhance crop pollination even in the presence of honeybees.

For the first chapter, I sampled pollinators associated with blueberry fields in south-central Chile and explore how landscape context can affect queen bumblebee ("Bombus terrestris") densities, which is the most abundant wild pollinator found in these systems. Queen bumblebees can be positively affected by forest area and negatively affected by a high-food resource area (flowering crops that are attractive to pollinators). Both effects were strongest at spatial scales of 2500-meter radius distance.

In the second chapter, I study the movement behavior of queen bumblebees foraging in blueberry fields, which was used to link bumblebee densities to the number of times each flower in the field is visited by a bumblebee. A higher number of flower visits translates into larger fruit set/weight, up to a threshold at which pollen saturation occurs. Movement patterns were highly directional along blueberry rows, and individuals tended to move toward the nearest plants. Using movement models, I show that observed movement patterns translate into a more efficient crop pollination service provision compared to movement patterns with random directionality.

In the last chapter, I explore how crop heterogeneity at the landscape scale can increase the provision of crop pollination services. Crop heterogeneity was measured by classifying crops according to their timing of flowering. Higher crop heterogeneity translates into a more continuous food supply that promotes colony growth. It also decreases the transient dilution effect which consists on pollinator density declines due to larger amount of flowering crop area.