Vernal pool productivity and percent canopy cover after transmission line construction: Does canopy cover minimize the effects of habitat fragmentation?

Background/Question/Methods

Vernal pools provide critical habitat for a wide variety of animal species including the indicator amphibian species (Lithobates (Rana) sylvatica, Ambystoma laterale, A. maculatum).  It is widely presumed that indicator amphibian species respond negatively to overstory removal.  Studies analyzing the effects of various canopy removal buffer treatments have concluded varying degrees of impact on different life stages and the initial and long term use of several amphibian species in altered areas surrounding vernal pools.  In recent years the number of utility corridors being constructed or proposed for construction in the Northeast has increased significantly.  These new corridors, even when co-located, can substantially change the landscape around vernal pools.  These developments are often sited in relatively undeveloped habitat blocks resulting in forested canopy fragmentation and direct impact to terrestrial habitat for amphibians and reptiles.  Vernal pool productivity is evaluated based on the number of egg masses of each of the indicator species.  Highly productive pools in Maine are defined by the State of Maine and there are specific limitations to the amount of clearing which can occur in the critical terrestrial buffer habitat surrounding them.

Results/Conclusions

Our study’s utility corridor includes 11 vernal pools in northern Maine. Pools were visited twice during appropriate seasonal conditions, once early in the season to capture wood frog egg mass abundance and again two weeks afterwards to capture salamander egg mass abundances.  The vernal pools were surveyed in 2007 prior to the 2008 construction and yearly post-construction (2009 through 2012).  Orthophoto analysis was completed on pre- and post-construction buffer canopy conditions to assess the forested buffer impacts at varying buffer widths according to known biological terrestrial habitat zones, regulatory guidelines and vernal pool best management clearing practices.  Our research analyzes the indicator amphibian abundance from 2007 through 2012 with the pre- and post- forested buffer percent canopy cover and change in canopy from buffer alterations during construction. Results indicate that median pre-construction amphibian productivity is not correlated to percent canopy cover; however, post-construction productivity is correlated to percent canopy cover.  Many states in the Northeast seek to protect vernal pools and their critical terrestrial habitat areas with best management practices and these results support the importance of maintaining canopy cover in the terrestrial habitat during and after activities which cause habitat fragmentation.