Orchid (Orchidaceae) decline in the Catoctin Mountains, Frederick County, Maryland as documented by a long-term dataset

Abstract

A 41-year study of the orchids of the Catoctin Mountains, Frederick County, Maryland reveals that 19 of 21 species have experienced precipitous declines. Four of these species are currently considered Threatened or Endangered by the State of Maryland and another two are considered Rare. Annual census data at 167 sites from throughout the Catoctin Mountains on protected and unprotected lands (private and public) show a loss of three species from the study area, a decline of[90 % (ranging from 99 to 91 %) in seven species, and a decline of \90 % (ranging from 51 to 87 %) for nine species. Each species was analyzed using Ordinary Least Squares Analysis to show trends and document corresponding R 2 and p values. We tested the hypothesis that this decline is due to intensified herbivory by white-tailed deer. The overall orchid census data is significantly inversely-correlated (R = -0.93) to the white-tailed deer harvest data of Frederick County (a surrogate for population size), which includes the entirety of the study area. Platanthera ciliaris showed a huge expansion at a single site explicitly managed for this species otherwise this orchid showed a decline similar to the other species. Proper management is critical for the continuation of the orchid species in this study, be it control of the white-tailed deer herd or combating woody plant succession in the case of P. ciliaris.

An indicator approach to capture impacts of white-tailed deer and other ungulates in the presence of multiple associated stressors

“…Our data provide clear evidence that efforts to reduce deer abundance and impact are needed to safeguard the more palatable and/or less browse-resistant species that continue to suffer at present deer densities ( Knapp and Wiegand 2014 ). All our sites at West Point allow access by recreational hunters, but that did not prevent high deer browse rates of oak seedlings.…”

Isotria medeoloides, a North American Threatened Orchid: Fungal Abundance May Be as Important as Light in Species Management

“…However, management whose only goal is to increase light levels may not be the most appropriate strategy because several factors may interact to influence plants’ performance. Dibble et al [ 20 ] found that increased canopy openness resulted in the increased growth of plants, especially ferns, that would compete with Isotria and increased herbivory that has been shown to have a negative impact on native orchids [ 9 , 52 ]. The increased competition was not a problem at our study sites because few other herbs were present and none that were there were dense enough or high enough to interfere with Isotria .…”

“…In the eastern US, fire suppression in forests has had a major impact on the characteristics of plant communities [ 8 ]. In some instances, orchid populations are threatened by the increased abundance of native species, especially herbivores [ 9 ].…”

Population dynamics and comparative demographics in sympatric populations of the round‐leaved orchids Platanthera macrophylla and P. orbiculata

“…Climate change could impact both their fungal partners and pollinators, with mismatches in phenology becoming more likely (Robbirt, Roberts, Hutchings, & Davy, 2014). Increases in deer populations and wintering grounds (from changes in snowpack) could reduce reproduction and survival (Knapp & Wiegand, 2014). Demographic modeling provides an avenue to understand which aspects of the life cycle most impact population growth currently and which may be most vulnerable to future change.…”