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

Wesley M Knapp,Richard Wiegand

doi:10.1007/s10531-014-0698-2

Wesley M Knapp, Richard Wiegand

Open Access

https://doi.org/10.1007/s10531-014-0698-2

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Abstract

A 41-year study (1968–2008) 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 R2 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.

Highlights

Of all the land plants the orchids (Orchidaceae) are among the most beautiful and charismatic
The overall orchid census data is significantly inversely-correlated (R = -0.93) to the white-tailed deer harvest data of Frederick County, 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

Summary

Introduction

Of all the land plants the orchids (Orchidaceae) are among the most beautiful and charismatic. Found on all continents except Antarctica, the Orchidaceae is one of the most diverse families of flowering plants with approximately 20,000 species (Smith et al Smith 2004). In the Catoctin Mountains of Frederick Co., Maryland, 27 species (native and non-native) have been informally reported (Wieg and unpublished data). Of these 27 species, 21 were readily occurring at the onset of this study. Four are listed as threatened or endangered (Maryland Natural Heritage Program 2010): longbract frog orchid Two are listed as rare (Maryland Natural Heritage Program 2010): brown widelip orchid (Liparis liliifolia), and palegreen orchid Two are listed as rare (Maryland Natural Heritage Program 2010): brown widelip orchid (Liparis liliifolia), and palegreen orchid (Platanthera flava var. herbiola)

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