Threatened and endangered (T/E) plants have high conservation value, yet each year many T/E species continue to decline and are faced with possible extinction. Long-term monitoring is essential for rare plant conservation and for evaluating changes in population size over time. In fire-adapted ecosystems, natural disturbance and certain types of anthropogenic disturbance (e.g., mowing) can be positive for the establishment of early-successional rare plants. However, little is known about the habitat requirements for disturbance-dependent species associated with mid- and late-successional seres. We report the preliminary results of a long-term monitoring study being conducted at Warren Grove Gunnery Range (WGR), located in the New Jersey Pinelands. The major objective of the study is to examine the affect of habitat disturbance from military operations on representative populations of Narthecium americanum, Corema conradii, Rhynchospora knieskernii, and Gentiana autumnalis. Corema conradii and G. autumnalis have local or State protective status while N. americanum (C) and R. knieskerni (T) are Federally-listed. The four populations occur in four different habitat types, each with a different disturbance history.
Results/Conclusions
Populations of N. americanum and C. conradii have remained stable over two seasons of monitoring. The N. americanum population occurs in an open wetland that has not been disturbed in over 50 years, while the C. conradii population occurs in upland pine-oak habitat last disturbed approximately 20-30 years ago. The G. autumnalis population occurs in an open moist grassland in the target zone where there is a high level of repeated disturbance (e.g., ordnance delivery, mowing). This population has increased significantly over three years (2007-2009); the current disturbance regime appears positive for the maintenance of ideal environmental conditions for growth, flowering, and recruitment. The population of R. knieskernii has been monitored over five years (2005-2009) and occurs within an abandoned target site-line last disturbed seven years ago. Following the last disturbance the population first demonstrated a significant increase (62 plants/0.03 m2) but has shown an overall steady decline by 2009 (6.8 plants/0.03 m2). This decline over five years is attributable to the complex relationships between disturbance, canopy cover, and soil water availability and stresses the importance for long-term monitoring. The population estimates for G. autumnalis and R. knieskernii suggest they may be among the largest populations in the New Jersey Pinelands.
