Amphibian and Vegetation Dynamics in a Restored Wetland in Maine

Wetland restoration and creation are used to offset wetland losses to development, but constructed wetlands frequently fail to replicate the functions of the natural wetlands they replace. We monitored a wetland restoration site in Maine from 1999-2002 to determine if the restored wetland successfully replicated the functions of the original forested wetland. We used a combination of pitfall trapping and egg mass counts to determine if three vernal pools created within the restoration site provide suitable breeding habitat for wood frogs (Rana sylvatica) and spotted salamanders (Ambystoma maculatum). We also tracked changes in hydrology and vegetation within the pools and in the restored wetland habitat surrounding the pools. Wood frogs and spotted salamanders colonized the three pools during the first spring following construction. Breeding effort (the number of egg masses deposited per female) was similar in all three pools for both species, but reproductive success (the number of juveniles produced per egg mass) was highest for both species in the one pool with temporary hydrology. The failure of two pools to develop the desired temporary hydrology allowed significant populations of green frogs (Rana clamitans) to persist. Green frog tadpoles preyed upon wood frog eggs and embryos, causing near-complete losses in the last two years of the study, and may have indirectly competed with developing salamander larvae. Percent cover and species richness of wetland plants within the pools and surrounding habitat increased throughout the study, but the vegetation that developed was not characteristic of forested wetlands in the northeast, and a single species, common cattail (Typha latifolia), became increasingly dominant. We also used drift fences and pitfall traps to study the movement patterns of adult and juvenile wood frogs and spotted salamanders within the restored wetland and surrounding habitat. Adults and juveniles of both species exhibited non-random movement at breeding pools directed preferentially from and toward closed-canopy forested habitat. Marked adult and juvenile wood frogs were recaptured at 30 m, 150 m, and 300 m from their breeding pool in the surrounding terrestrial environment. The majority of terrestrial recaptures occurred within the forested habitat to the north of the pool. The median snout-to-vent lengths of recaptured juvenile wood frogs were progressively larger at greater distances from the pool. The number of juveniles emerging from the pool was positively correlated with the number of juveniles recaptured two days later at 30 m, four days later at 150 m, and six days later at 300 m. Adult wood frogs were 95% faithful to their breeding pools from 2001 -2002, and adult spotted salamanders were 100% faithful to their breeding pools during the same period. For wood frogs, adult migration to and from breeding pools was positively correlated with minimum nightly temperature, juvenile dispersal from pools was positively correlated with precipitation, and terrestrial activity of juveniles was positively correlated with both maximum daily and minimum nightly temperature. For spotted salamanders, adult migration to breeding pools was positively correlated with minimum nightly temperature and precipitation, adult migration from pools was positively correlated with precipitation, and juvenile dispersal from pools was positively correlated with precipitation