Utility Rights-of-Way Wildlife Research at Penn State
Plant and animal community response to long-term vegetation management on rights-of-way

Bee Community Research

There are at least 4000 species of bees in North America: of these, at least 371 can be found in Pennsylvania 35. Bees pollinate roughly 75% of the fruits, nuts and vegetables that are grown in the United States alone 36, and conservation of bees has become a worldwide priority.

Previous studies at State Game Lands 33, Centre County, Pennsylvania (SGL33) have examined the diversity of plants, mammals, birds, reptiles, amphibians, and butterflies found at the different treatment sites. With industry, government, and society increasingly focused on the conservation of pollinators and their habitats, the Project Director and Sponsors found that little is known about how different vegetation management methods used on power line rights-of-way affect our native bee populations. In 2016, the first survey of bees at SGL33 began.

From May to August 2016, bee surveys were conducted monthly on SGL 33 plots that were each scheduled to follow one of six different vegetation management practices in late August of 2016. The practices included the following application methods and relative volume of herbicide used: two plots of high volume foliar application of herbicide (one plot at 249.04 L/ha and a second plot at 70.63 L/ha), one plot of low volume basal application of herbicide (9.71 L/ha), two plots of low volume foliar application of herbicide (9.35 L/ha and 2.33 L/ha), and one plot of hand-cutting (0 L/ha).

Initial Findings: 2016

  1. The greatest numbers of bees (both the number of individual bees and the number of bee species) were collected from the plot where individual, noncompatible and/or non-native plants were scheduled to be selectively treated using low volume basal herbicide application.
  2. The least number of bees (individuals and species) were collected from the plot where hand-cutting has always been employed, resulting in an abundance of woody vegetation and few flowering, herbaceous plants.
  3. The most diverse collection of bees was gathered from a plot scheduled for a broadly-applied treatment (high volume foliar).
  4. The least diverse collection of bees was gathered from a plot scheduled for a low volume basal herbicide treatment.

Post-Treatment Findings: 2017

  1. The greatest number of individual bees was collected from the low volume basal plot, and the greatest number of bee species was collected from one of the low volume foliar plots.
  2. The least number of individual bees was collected from the hand-cutting plot, followed by one of the low-volume foliar plots. The least number of bee species was also collected from the hand-cutting plot, followed by both high volume foliar plots.
  3. The most diverse collection of bees was gathered from one of the low volume foliar plots.
  4. The least diverse collection of bees was gathered from the low volume basal plot.

While there are a number of factors leading to declines in native bee populations, species richness, and diversity, one of the greatest threats is the loss or fragmentation of habitat. There are millions of acres of transportation and power line rights-of-ways in the United States. The vegetation within these corridors are routinely managed and could serve as valuable habitat for native bee species. Better understanding the impacts that commonly used vegetation management practices have on bees will allow vegetation managers to develop improved strategies for promoting native flowering plants and suitable nesting habitat in these spaces.

References


35Donovall, III, L.R. and D. vanEngelsdorp. 2010. A checklist of the bees (Hymenoptera: Apoidea) of Pennsylvania. Journal of the Kansas Entomological Society. 83(1): 7-24.


36Moisset, B. and S. Buchmann. 2015. Bee Basics: An Introduction to Our Native Bees. A USDA Forest Service and Pollinator Partnership Publication. 42 pages.