Initial effects of woody biomass removal and intercropping of switchgrass (Panicum virgatum) on herpetofauna in eastern North Carolina

Background/Question/Methods

Forests are potential sources for a wide range of alternative fuels, which could reduce dependency on fossil fuels and carbon emissions.  In addition to generating biofuels from gleaning coarse woody debris after harvesting pine plantations, biofuels could also be produced from perennial grasses that are either planted alone or intercropped with other biofuel feedstocks.  Despite the potential benefits associated with production of biofuels, sustainability of producing biofuels from forests must be substantiated from experimental research that examines effects of feedstock production on wildlife populations.  Therefore, we conducted an experiment on twenty, 0.81-hectare plots in eastern North Carolina, USA on sites established and maintained by Catchlight Energy LLC, a Chevron|Weyerhaeuser Joint Venture. Here, we independently manipulated whether coarse woody debris was removed from loblolly pine (Pinus taeda)  plantations for biofuel production and whether pine was intercropped with the perennial grass, switchgrass (Panicum virgatum) to assess effects on herpetofauna diversity and abundance.  We also included a treatment to evaluate whether diversity and abundance of herpetofauna differed in areas managed for pine production compared to areas managed primarily for switchgrass production.  We sampled amphibians and small reptiles with drift fence arrays spring-summer 1- and 2-years after treatment establishment.

Results/Conclusions

We had 425 captures of 15 species of herpetofauna across the two sampling seasons but we were unable to detect large general effects of coarse woody debris removal or planting of switchgrass in pine plantations on measures of herpetofauna diversity or relative abundance.  However, Simpson’s Diversity index was greater in areas managed for switchgrass only than in pine plantations during the second year of study and captures of southern toads were less common in switchgrass only areas than in pine plantations. We also observed a substantial reduction in total abundance of herpetofauna in switchgrass only plots relative to treatments with pine production.  Our work indicates that neither intercropping switchgrass with pine nor removal of coarse woody debris from pine plantations caused herpetofauna diversity or abundance to differ from traditional management of pine plantations during the first two years following plantation establishment.  Future research, however, should monitor populations through succession as the canopy of pine plantations continues to close and consider effects from landscape scales and other potential feedstock sources.  Our work also indicates that managing areas for switchgrass production alone could cause diversity and abundance of herpetofauna present to differ from those observed in pine plantations.