Experimental Reintroduction of Beach Pea (Lathyrus japonicus) to the Indiana Dunes National Lakeshore

Abstract

Reintroduction of plants has become an increasingly important restoration tool as more natural landscapes are impacted by urban development. Beach pea (Lathyrus japonicus) is an early successional plant growing in foredunes throughout the Great Lakes, U.S.A. This species is sensitive to trampling and recreational use and currently is endangered in Indiana. We reintroduced 350 plants into seven reintroduction sites (50 plants/site) in three locations at the Indiana Dunes National Lakeshore (INDU) in 2008. Experimental design at each site comprised of ten, 1 m² quadrats grouped into five blocks, with each block consisting of a quadrat without supplemental watering and a quadrat with supplemental watering three times/week. We transplanted five plants into each quadrat. To decrease transplant mortality from sand burial, we installed sand barriers windward of each transect. By the end of October, 56 (16%) plants survived. We used logistic regression with backwards stepwise elimination to analyze effects of predictor variables (watering treatment, percent open canopy, distance from lake, foredune/blowout, plant stem length, and precipitation) on probability of survival. Supplemental watering, closer proximity to the lake, and longer stem length were associated with higher rates of survival. Quadrats with supplemental watering had higher percent soil water than non-watered quadrats, and sand barriers decreased sand accretion near transplants. We recommend initiating future reintroductions with more mature transplants on lower foredunes and in blowouts. Blowouts can also act as refuges from stochastic events such as high lake or ocean water levels related to climate change.