[MPWG] WEB: Havest & Deer Herbivory Effects on American Ginseng

[Olivia Kwong]

The full paper can be accessed with a subscription.

http://www3.interscience.wiley.com/journal/121572130/abstract

Contributed Paper
Interactive Effects of Harvest and Deer Herbivory on the Population 
Dynamics of American Ginseng
SUSAN J. FARRINGTON*, ROSE-MARIE MUZIKA*, DAN DREES., AND TIFFANY M. 
KNIGHT.
Copyright 2008 Society for Conservation Biology

ABSTRACT

Abstract:  Few demographic models for any species consider the role of 
multiple, interacting ecological threats. Many forest herbs are heavily 
browsed by white-tailed deer (Odocoileus virginianus) and a number of 
these are also harvested for the medicinal, floral, or horticultural 
trades. Previous studies of the viability of American ginseng (Panax 
quinquefolius) have separately examined the effects of harvesting and deer 
herbivory. We followed individually marked ginseng plants in 6 populations 
for 8 years and documented deer browse levels, conducted helicopter 
surveys to estimate the deer herd size, and documented 2 ginseng harvests. 
We used this long-term data set to develop a stochastic demographic model 
that quantified the separate and interactive role of these threats to 
ginseng viability. Although harvesting and deer herbivory negatively 
affected ginseng population growth, their effects were not additive. Deer 
herbivory negatively affected population growth in the absence but not in 
the presence of harvesting. Life table response experiments revealed that 
in the presence of harvesting, deer herbivory had some positive effects on 
vital rates because browsed plants were less apparent to harvesters. 
Ginseng populations that were harvested responsibly (i.e., planting seeds 
from harvested individuals) had higher growth rates than those that were 
harvested irresponsibly. We concluded that both deer populations and 
harvesting must be managed to ensure sustainable populations of American 
ginseng. Our findings underscore the importance of long-term monitoring to 
assess threats to viability and the need for a broad ecological 
understanding of the complexity of ecosystem management.