Lowell-Dracut-Tyngsborough State Forest
Vernal Pool Inventory
Prepared by:
Timothy Beaulieu
Background
Vernal pools are temporary to semi-permanent pools occurring in shallow depressions that typically fill during the spring or fall and may dry during the summer or in drought years (Calhoun and deMaynadier 2008). Vernal pools provide breeding habitat for a unique group of amphibians and invertebrates that depend on wetlands absent of fish, which would otherwise prey upon and greatly reduce the breeding success of these species.
Vernal pools occur across the landscape in isolated,
confined basins with no permanent hydrological connection to a stream or other
permanent water body (Massachusetts Division of Fisheries and Wildlife 1988).
These pools exist as temporary to semi-permanent waters in shallow natural
depressions surrounded by uplands (Tiner 2003).
Vernal pools habitats are recognized under the Massachusetts Wetlands Protection Act if they have been documented and officially certified with the Massachusetts Natural Heritage and Endangered Species Program (NHESP). This study was conducted in order to inventory, document, and certify vernal pools within the Lowell-Dracut-Tyngsborough State Forest.
Vernal pool inventory
During the spring and summer months of 2007 I conducted an inventory of the Dracut portion of the Lowell-Dracut-Tyngsborough State Forest on behalf of the ‘Friends of the Forest’. This study took place in order to locate and map all existing vernal pool locations. I located vernal pools on foot through systematic ground transects throughout the Forest.
Vernal pool wildlife surveys
In accordance with the Massachusetts NHESP vernal pool certification criteria (NHESP 2000), I visually surveyed all vernal pool sites for obligate species breeding activity within each pool. I conducted amphibian surveys during the spring months 2007 based on the breeding phenologies of pool breeding amphibians in eastern Massachusetts (Burne 2005; Paton and Crouch 2002). Amphibian eggs and larvae as well as fairy shrimp were surveyed visually, captured by hand, or captured with the use of an aquatic fine mesh dip net, and photographed.
Facultative invertebrate species were also captured and documented as a bycatch from obligate species survey methodologies. Facultative species are organisms that utilize but do not require vernal pools for their continued survival.
Spotted turtles (a protected species) and Blanding’s turtles (listed as a Threatened species in Massachusetts) were documented through visual encounter or hand capture techniques as part of this study.
Vernal Pool Mapping
I estimated the length and width for each pool in the
field and digitally re-measured the pools on aerial imagery in a Geographic
Information System (GIS). I used Global Positioning System (GPS) track points
collected by walking along the edge of each pool as reference points. I
measured the depth of each pool using a 4-foot aquatic dip as a measuring
device marked at 1-foot intervals. A GPS point was taken near the center of
every pool encountered on the ground and the coordinates were uploaded into a
GIS.
Results
The results of
this study show that there exist many certifiable vernal pools within the
Forest along with two turtle species protected under the Massachusetts
Endangered Species Act.
Vernal Pools
Twenty vernal pool locations were identified and found to meet the criteria for Certification under the NHESP certification guidelines within the Dracut portion of the Forest. (Table 1)
Endangered Species
I documented two state listed turtle species within the Forest during this study: the Blanding’s turtle and the spotted turtle (Figure 1). Blanding’s and spotted turtles are long lived species with delayed sexual maturity. Both species will typically become sexually mature only after approximately 15 years of age. These species have relatively large home ranges and prefer a mosaic of wetland types from large forested wetlands to small vernal pools. These turtles visit vernal pools to feed on amphibian eggs, as mating sites, or as staging areas prior to nesting in order to stay hydrated.
Three Blanding’s turtles were observed within the Forest. Blandings’ turtles have large home ranges and have been known to travel 3.2 kilometer straight line distances within one season (Grugrovic and Sievert 2007). There is currently no data showing the movements and habitat utilization of this species within the Forest.
Discussion
This inventory of the vernal pools located within the Dracut portion of the Forest proved to be highly successful with a total of 20 certifiable vernal pools.
In 2007, I submitted all rare species observations to NHESP on official rare species observation forms. In 2007, I also submitted all required vernal pool data to NHESP in order to have each site officially certified. All data is currently under review by NHESP staff as of February 2008.
At the request of the ‘Friends of the Forest’, I plan to conduct a vernal pool inventory of the Lowell portion of the Forest during the spring months of 2008.
Recommendations
Within Dracut, several pools were found to lack the necessary biological evidence for certification. Future monitoring over several years may prove that some of these sites may in fact be certifiable vernal pools.
As housing developments continue to encroach upon the edges of the Forest, it becomes increasingly more important to understand the habitat requirements of rare species such as Blanding’s and spotted turtles with known large home ranges. I recommend that resources be acquired and allocated to conduct a census of the Blanding’s and spotted turtle populations within the Forest. Additionally it would be beneficial to conduct a trapping and telemetry study of these turtles in order to map the home ranges of these populations, especially to identify turtle nesting habitat.
Blue spotted salamanders, a state listed Species of Special Concern, potentially exist within the Forest. It is very difficult to locate and identify egg masses of this species. Methods of detection for adult salamanders of this species include: laying drift fencing and pitfall traps around vernal pools, this method is extremely labor intensive; setting minnow traps to catch adult salamanders within pool sites; and visual encounter surveys using high powered flashlights at night when the species is active.
References:
Burne M.R.
(2005) Habitat associations of pool-breeding amphibians in eastern
Calhoun, A.J.K. and P.G. deMaynadier
(2008) Science and Conservation of Vernal
Pools in Northeastern North America. CRC Press,
Grugovic M. and Sievert P. (2005) Movement patterns of Blanding’s turtles (Emydoidea blandingii) in
the suburban landscape of eastern
Paton P.W.C. and Crouch III. W.B. (2002) Using the phenology of pond-breeding amphibians to develop conservation strategies. Conservation Biology 16: 194–204.
Tiner, R.W. (2003) Geographically isolated wetlands of the