Pennsylvania State University – DuBois Campus

Radnor Lake State Natural Area Ecology and Management Research Collaborative

Collaborative Lead Scientist: Robert E. Loeb, Ph.D., Professor of Biology and Forestry

Field-research-at-Hall-Farm-Area-on-March-11th-2015-Pix-by-Steve-Ward

Research Partners Dr. Douglas Heffington (MTSU Global Studies and Geography Program), Dr. Robert Loeb (Penn State University) and Roger McCoy (Director of Natural Areas) conducting research on the Hall Farm in March 2015. Pix by S.Ward

Overview of Natural Area Ecology and Management Research Collaborative

The Research Collaborative provides a scientific basis for the ecological management of Radnor Lake State Natural Area. The context of the Research Collaborative is long-term ecological research that informs adaptive management of Radnor Lake State Natural Area. Individual projects are focused on particular environmental concerns and land management challenges such as white-tailed deer browsing, beaver cutting of trees, invasive plant species, landslides, rare plant species, and sensitive forest communities. The research projects described below are divided into two categories: Ongoing Projects (with first generation results published) and New Initiatives.

Ongoing Projects

Long-term Forest Change Following the Reestablishment of a White-tailed Deer Population

Early research in 1974 and 1994 defined the forest communities of Radnor Lake State Natural Area and provided an array of research plots to be re-measured. In 1980, the first White-tailed Deer was observed in Radnor Lake State Natural Area but the population did not expand rapidly as evidenced by the presence of seedlings in the thousands per acre in 1994. By 2008, the seedling population in the research plots were decimated and the saplings population declined as well. Because Tennessee’s Natural Area Law precludes White-tailed Deer harvests, future re-measurements are expected to show the continuing expansion of the sugar maple, silver maple, and pawpaw populations which the White-tailed Deer avoid during browsing.

Contact Dr. Robert Loeb via e-mail at RXL5@PSU.EDU to obtain a copy of the scientific journal publication from this research: Loeb, R.E., Germeraad, J., Griffin, L., Ward, S. (2011). “Arboreal composition changes following Odocoileus virginianus Zimmerman restoration to urban park forests without off-trail park visitor trampling.” Urban Forestry & Urban Greening, 10(4):305-310.

Assessment of Invasive Plant Species Removal Efforts for Amur Honeysuckle

The invasive shrub Amur honeysuckle became established in Radnor Lake State Natural Area over 30 years ago and the alien species has spread across the Natural Area landscape. Amur honeysuckle grows to more than 10 feet tall and the dense foliage has shaded out the small flowering plants on the forest floor. By the year 2000 the effects of Amur honeysuckle could be observed across hundreds of acres of the Natural Area. The program of Amur honeysuckle removal went into high gear in 2002 and by 2009 a large portion of the invaded area was treated with some sections receiving treatment in only one year and other locales having treatments each year. For Amur honeysuckle even the most careful and comprehensive treatment does not result in species eradication because the tiny rootlets and seeds left in the soil after treatments result in Amur honeysuckle becoming reestablished. The research demonstrated that annual treatments are far more effective than treatment in only one year because the population of small Amur honeysuckle plants become reestablished within a year and therefore a program of ongoing treatments is necessary to fully control Amur honeysuckle.

Contact Dr. Robert Loeb via e-mail at RXL5@PSU.EDU to obtain a copy of the scientific journal publication from this research: Loeb, R.E., Germeraad, J., Treece, T., Wakefield, D., Ward, S. (2010). “Effects of 1-year vs annual treatment of Amur honeysuckle in forests.” Invasive Plant Science and Management. 3(3):334-339.

Effects of Record Breaking Rainfall on Forest Composition

The record breaking rains of May 1–2, 2010 caused a natural disaster at Radnor Lake State Natural Area with over 200 trees and saplings being lost at 40 sites in the Natural Area. As compared to the overall population of trees and saplings in the Natural Area, the rockslides and soil slides resulted in nearly five times more tree deaths than saplings deaths. Prior research on the distribution of trees and saplings by species with a lateral root system versus a tap or heart root system showed the Natural Area contains nearly equal numbers of tree and sapling possessing a lateral root system versus tap or heart root system However, 74% of the sapling losses to the slides were from surface root system species.

Contact Dr. Robert Loeb via e-mail at RXL5@PSU.EDU to obtain a copy of the scientific journal publication from this research: Loeb, R.E., King, S. (2011). “Landslides and the urban forest.” Arboriculture & Urban Forestry, 37(5):213-218.

Management of Beaver Damage in the Lake Shore Forest

The population of North American Beaver at Radnor Lake State Natural Area has built dens and dammed tributary streams along the shores of Radnor Lake. The most obvious effect of these activities is beaver cut tree and sapling stumps as well as damaged trees and saplings standing close to the shore of the lake. Beaver harvest is not an option at Radnor Lake State Natural Area because of the legal protection provided by Tennessee’s Natural Area Law. The area of trees cut by beavers is not limitless, because beavers have a very sensitive olfactory ability to detect predators. But the question was what species in Radnor Lake State Natural Area do beavers consider predators and the answer hypothesized was people. Remembering that off trail transit by people is strictly prohibited in Radnor Lake State Natural Area, the potential for human pathways, which collect the human odor of hikers, to serve as barriers to beaver cutting was examined. Comparisons of areas uphill of the human pathways to nearby lakeside areas showed beaver damage was virtually absent in the forests uphill of human pathways as compared to extensive damage in the shore line forests. Thusly, future trail renovations which include shifting the location of the trail can serve to change the extent of North American Beaver damage in the shore forests of Radnor Lake State Natural Area.

Contact Dr. Robert Loeb via e-mail at RXL5@PSU.EDU to obtain a copy of the scientific journal publication from this research: Loeb, R.E., King, S., Helton, J. “Human pathways are barriers to beaver damage in urban forests.” Urban Forestry & Urban Greening. 13(2:290-294).

Sensitive Forest Communities – Ridge Forests

Ridge forests are very limited in area because the tops of ridges are very narrow. Therefore, damage to soils and plants caused by hikers walking along trails is devastating because the trails occupy a large portion of the entire area of the Ridge Forest. Even in Radnor Lake State Natural Area where the prohibition on off-trailing is strictly enforced, the damage caused by hundreds of hikers each day damage can profoundly affect a ridge forest. Three Ridge Forests with different levels of hiking impact were compared in Radnor Lake State Natural Area: Ganier, Cherrywood, and Harris. The resilient species chestnut oak was dominant in all three ridge forests; however, tree, sapling, and seedling populations were significantly larger in Ganier than Cherrywood and Harris. Harris, the Ridge Forest least disturbed by hiking, had three species – shagbark hickory, common hackberry, and September elm – with significantly larger tree and seedling populations than Cherrywood and Ganier.

Contact Dr. Robert Loeb via e-mail at RXL5@PSU.EDU to obtain a copy of the scientific journal publication from this research: Loeb, R.E., King, S., Helton, J. “Ridge forests in urban natural areas.” Natural Areas Journal. 35(2:297-301).

New Initiatives

Influence of Historic Agriculture on the Forests of Radnor Lake State Natural Area
The extensive research on the archeology of Radnor Lake State Natural Area conduct by the Middle Tennessee State University Research Collaborative (insert link) has provided the opportunity to study the forests of Radnor Lake in regard to influences of the former farms that became the Natural Area. Current status of the research: Sites have been identified and the forest research will commence in March 2015.

Address questions concerning this project to Robert Loeb via e-mail at RXL5@PSU.EDU.

Establishment of Significant Species in Response to Invasive Species Removal

Over the past decade, two invasive alien species – Amur Honeysuckle and Tree-of-Heaven – have been the target of intensive removal efforts. The response of the native plants in the ground layer has been variable but recently three rare and sensitive native plant species have been found in areas treated for invasive species removal. Population distribution work is well underway for all three species: Deam’s Copperleaf, Nodding Rattlesnakeroot, and Wild Dill. Research sites were established in 2014 to measure the response of the Wild Dill population to Amur honeysuckle and Tree-of-Heaven removal.

Address questions concerning this project to Robert Loeb via e-mail at RXL5@PSU.EDU.

Grasslands Restoration

Today Radnor Lake State Natural Area is recognized for two natural communities – forests and the lake. However, historical evidence shows grasslands was the third community within the Natural Area. Invasive species have taken over the former grasslands; however removal of those invasive species alone does not result in the return of the grasslands. For grassland communities to return three basic steps are required: remove of the invasive species; seeding of native grassland species; and periodic burning to preclude the return of invasive species and support the biology of the native grassland species. The research will monitor the environmental changes during the progress of the three steps, which will require many years of sustained efforts, to examine the grassland restoration process.

Address questions concerning this project to Robert Loeb via e-mail at RXL5@PSU.EDU.

 

Excerpts from Dr. Loeb’s letter to Ranger Steve Ward

 

First and foremost, please accept my heartfelt thanks for the extensive assistance provided by you and the staff of Radnor Lake in support of my research on long-term forest change within the Natural Area site.

Even though I was very focused on the research and only had five days to conduct the field work, one cannot fail to take notice of the fabulous Radnor Lake Natural Area! I have been studying urban woodlands in the eastern United States for 35 years and none come close to Radnor Lake in terms of vegetation community diversity, landscape preservation from ongoing disturbance, visual accessibility to wild animals, and awe inspiring beauty. If it is not obvious, I am smitten by all that the Radnor Lake Natural Area has to offer. As we discussed months ago in planning my visit, I will return in five year intervals to resample the plots I measured last week. But today I hope to perform far more research and provide my thoughts in regard to planning for the future of the Radnor Lake Natural Area.

Extend my applause and thanks to the Radnor Lake staff and the “Friends of Radnor Lake” for the great work they are doing to protect the Natural Area!

My best,
Robert E. Loeb, Ph.D.