Three prong adult ginseng plant in late August. The most valuable wild harvested plant in West Virginia. Dried ginseng root can bring as much as $500 per pound to rural harvesters. Over $6 million of root is sold every year in West Virginia alone. Increasing rarity of this species has prompted our research on how to regulate harvest in such a way that harvesters may actually improve ginseng’s long-term prospects for survival.
Ginseng is America's premiere wild harvested medicinal plant, bringing millions of dollars to harvesters of rural Appalachia each year. It is relatively uncommon to rare, and is listed on Appendix II of CITES (the Convention on International Trade in Endangered Species). These two facts alone would make it a fascinating plant to study, but in addition to its economic and cultural value, ginseng is a perfect plant for long-term population studies. As such, ginseng has become our 'canary in the coal fields' for all kinds of environmental impacts of human activities. Thus, my students and I have studied genetic and demographic effects of harvest, overbrowsing by white-tailed deer, effects of invasive species, and consequences of climate change, using ginseng as a model species.
A series of National Science Foundation grants have funded our work in several linked areas of ecology and ecological genetics:
Harvest studies: Erin Hackney’s (MS) work, published in Conservation Biology, clearly showed the existence of an Allee effect (lowered reproductive output) in small experimental populations ginseng (Hackney and McGraw 2001). Martha Van der Voort’s (PhD) work (Van der Voort et al. 2003) showed that ginseng recovers only slowly from harvest. She also showed dramatic demographic effects of harvester behavior on ginseng population growth (Van der Voort and McGraw 2006). Our work has also shown that the distribution of ginseng is more widespread than previously thought (McGraw et al. 2003). A study of herbarium specimens showed a century-long decline in ginseng plant size range-wide (McGraw 2001). Emily Mooney's PhD project examined the selective effects of harvest (Mooney and McGraw 2007) as well as the prevalence of inbreeding and outbreeding depression (Mooney and McGraw 2007). Emily Mooney's work also showed how life history shifts were related to harvest history in a population, demonstrating that the human-ginseng interaction extends to evolutionary effects beyond the obvious effects on selective harvest (Mooney and McGraw 2009).
Effects of deer overpopulation: Mary Ann Furedi’s PhD work on the deer-ginseng interaction demonstrated clear negative effects and added substantively to the call to control deer overpopulation. The population viability analysis of this remarkable data set led to our paper in the journal Science (McGraw and Furedi (2005). This work resulted in coverage by NPR's All Things Considered, National Geographic, Scientific American, USA Today, New York Times, Washington Post, LA Times, and over 100 other news outlets.
Effects of invasive species: MS student Kerry Wixted studied the effects of invasive species, especially garlic mustard, on ginseng seedlings and adults (Wixted and McGraw 2010). We also pioneered plant-centric sampling for invasive species using our annually censused plants (Wixted and McGraw 2008), showing that ca. 2/3 of ginseng populations contain invasives within competitive range, and about 1/3 of all individual plants are exposed to one or more of 12 invasive species. Kerry also worked with fellow graduate student Alyssa Hanna on a study of the effects of the overstory invasive, tree-of-heaven (Ailanthus altissima) on ginseng (Hanna, Wixted and McGraw, submitted).
Effects of climate change: Conservation Fellow and PhD student Sara Souther studied the effects of climate warming on population distribution and viability. This revealed some fascinating and unexpected effects such as increased vulnerability to frost damage due to early development of plants in warmer winters (Souther and McGraw 2010). Sara also showed that with respect to growing season daily maximum temperatures, the demographic response shows a pattern consistent with local adaptation; each population does best at the long-term temperature observed at that site, with a fall-off in population growth in warmer or cooler years (Souther and McGraw 2011). Using a two-year growth chamber study carried out at McGill Phytotron, we collaborated with Marty Lechowicz to test whether this apparently ecotypic response was due to the direct effect of temperature. Surprisingly, there was no clear pattern of growth or reproductive response to temperature alone, therefore we concluded the responses observed in the field were due to indirect effects of temperature (Souther, Lechowicz, and McGraw 2012). Sara completed her PhD in Summer, 2011 and began a Smith postdoctoral conservation fellowship at University of Wisconsin-Madison in August of that year. She is now studying assisted relocation as a conservation strategy in the face of climate change.
Effects of urbanization and habitat fragmentation: MS student Zach Bradford is using ginseng to study 'edge effects' on demography of understory species, with special attention to the effects of forest fragmentation on reproductive biology. Stay tuned.
Land use and impacts on natural populations of ginseng: PhD student and Conservation Fellow Jessica Turner is developing her PhD project centered on the effect of mountaintop removal mining on ginseng populations and the harvest culture. She is interfacing with WVU's HSTA (Health Sciences Technology Academy) program to work with students to understand how harvesters perceive the effect of mining on ginseng availability. In addition, she is interested in the potential to use medicinal plants such as ginseng and goldenseal to restore the understory community on abanddoned mine sites. Jennifer Chandler is examining the effect of timber harvest on understory plants, using ginseng as a model system. She is testing the hypothesis that moderate canopy openings may benefit understory plants that are selected for existence in old growth forests (such as ginseng), but deep shade or large canopy openings may be detrimental.
Dispersal in ginseng: Amy Hruska is using game cameras and cafeteria feeding boxes to identify the dispersers of ginseng fruit and using additional experiments attempting to determine whether birds and small mammals are seed predators or mutualists. This is key information for improving our demographic modeling of the species, understanding potential gene flow in response to climate change, and for developing metapopulation models of the species.
Our ginseng research is continuing full steam ahead with our NSF LTREB (Long-term Research in Environmental Biology) grant (2006-2011, with 2011-2016 continuation now funded). The long-term data set has allowed us to carry out unique studies, including some of those mentioned above. In addition, we have continued our long-term interest in human interactions with this species by documenting for the first time the rate and legality of harvest in natural populations; heretofore very difficult information to obtain (McGraw, Souther and Lubbers 2010).
Future research: We have funding to continue our in-depth demographic censusing of 30 populations of ginseng over a wide portion of its range until 2016. This means we will have amassed a huge reservoir of detailed census data that can be used in exciting new ways. For example, we will be in an excellent position to examine the importance to population viability of rare events in the history of populations. We will have a sufficient sample size to begin parsing the interactive effects of multiple factors on demographic performance and persistence. We also plan to systematically examine the role of additional factors known to influence ginseng viability, including land use history and disease. Numerous opportunities will be made available to graduate students to develop their own interest in ecological stressors using this system as a starting point.
Capacity building: Each summer, we train conservation interns to participate in large-scale censusing of ginseng populations, and encourage them to develop independent research projects as well. Recent undegraduate interns include: Allison Kenyon, Clare Maloy, Mark Guido, Allison Kenyon, Jackie Boyczuk, Zach Bradford, Caitlin McGraw, Danielle Doll, Lorraine Carter-Lovejoy, Diana Black, Alixandra Wagner, Stevia Morawski, and Zack Zacavish.