The understory conditions of eastern hemlock stands in the Delaware Water Gap National Recreation Area have been altered by canopy decline caused by an exotic insect pest, the hemlock woolly adelgid. We consider the response of bryophytes to these changes, particularly increased availability of understory light and coarse woody debris (CWD). Pre-adelgid surveys and environmental measurements were taken at a network of 72 permanent plots in 1994 and 1995. Re-measurement of understory variables was conducted in 2003 and 2006. Bryophytes have responded to adelgid impacts through a sustained increase in plot-level richness, mainly achieved through a greater frequency of species occurring on CWD and to a lesser extent on bare soil in the plots. Greater gains in species richness took place in plots closer to the streams. Bryophyte responses to understory light availability and shrub density suggest that light availability may be more important for species maintenance than for species colonization. Orthodicranum montanum (Hedw.) Loeske had the greatest increase in frequency, occurring in two-thirds of all plots on one or more substrata by 2006. Several nitrophilous species had appeared by 2003 and 2006 including Brachythecium rutabulum (Hedw.) Schimp., which has now colonized almost one-third of the plots since the hemlock woolly adelgid invasion. Bryophytes are a significant component of the understory vegetation in eastern hemlock stands and this study is the first to document the dynamic nature of their response to hemlock woolly adelgid impacts.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 135 • No. 1