Volume 76 - Issue 1 (March 2011)

ABSTRACT The largest Maryland population of the federally threatened tidal freshwater wetlands legume, Aeschynomene virginica (Sensitive Joint-vetch), is comprised of two subpopulations in the Manokin River watershed. To provide baseline data fundamental to understanding annual fluctuations and long-term trends, annual censuses began in 1991 and 1994 for Taylor Branch and Manokin River subpopulations, respectively, and continued through 2009. In addition, distributional limits, phenology, average plant height, associated plant species, and muskrat activity were recorded to better understand plant and habitat characteristics. Large annual fluctuations in size were common to both subpopulations. The Manokin River subpopulation (2 km in extent) averaged 1,867 6 268 plants (n 5 16), ranged from 715–4,394 plants, and inhabited marshes (56%) and banks (44%). Subpopulation size increased significantly during the survey period. June rainfall may have contributed to a tripling in subpopulation size from 2005 to 2009, but a significant increase from 1994–2006 was related to some undetermined environmental factor. The Taylor Branch subpopulation (0.6 km in extent) averaged 400 6 122 plants (n 5 18), ranged from 42–1,797 plants, occurred almost solely in marshes, and did not change significantly in size over the study period. Seed germination occurred in late April, shoot growth through July, and flowering and fruiting peaked by mid-August and early October, respectively. Muskrat effects were negligible for both subpopulations. Although continued subpopulation monitoring is important, sediment accretion and wetland hydrology studies are needed to predict long-term viability of A. virginica in the Manokin River watershed.

ABSTRACT Over the past several decades, naturally occurring populations of Fraser fir (Abies fraseri) in the Black Mountains of North Carolina have been heavily impacted by both direct and indirect anthropogenic disturbances, including logging and logging-associated fires, and high mortality rates due to the balsam woolly adelgid (Adelges piceae) (BWA). The decline in Fraser fir is worrisome because it serves as a foundation species of the spruce-fir forests of the Southern AppalachianMountains.Our objectives for this research were to: 1) characterize the current status of Fraser fir trees with respect to potential population decline, as identified by the regenerationmortality hypothesis, by using stand structure and infestation levels, 2) determine the influence of slope, elevation, aspect, and disturbance history on stand structure,mortality, and BWA infestation level, and 3) examine broad trends of Fraser fir cover change caused by BWAover a 60 year period by using repeat aerial photography. We conducted detailed field surveys of Fraser fir trees throughout the Black Mountains using 44 circular plots. Analysis of repeat aerial and ground photographs revealed a decline in Fraser fir cover.60%from1954 to 1988, followed by regeneration from1988 to 2006. Our results indicate that Fraser fir stands at higher elevations are currently in a state of recovery, whereas Fraser fir stands at lower elevations have the potential to become increasingly susceptible to BWA-induced mortality in the future. Our results call attention to the significant impact of direct and indirect anthropogenic disturbance upon Fraser fir stand structure, but also provide evidence for the ability of an imperiled ecosystem to recover from such activity.