Restoration of a coastal sandplain grassland: Reducing biotic and abiotic barriers to native plant establishment in a former agricultural field

Background/Question/Methods

Coastal sandplain grasslands are globally rare and provide habitat for rare and endangered plant and animal species. More than 90% of coastal grasslands in the northeastern U.S. have been lost, in part to agriculture.  Agricultural abandonment has become widespread; however regeneration of native species-rich grasslands has been limited on former agricultural lands.  Biotic and abiotic agricultural land-use legacies such as the introduction of nonnative species, modified soils from agricultural amendments, and the elimination of historic disturbance regimes have been limiting factors in native species establishment.  We conducted a restoration experiment to test the effect of vegetation removal treatments and soil amendments on the abundance of native and nonnative plant species in a former dairy pasture that is currently dominated by nonnative species on Martha’s Vineyard, MA.  Vegetation removal treatments were single tillage, multiple tillage, glyphosate, black plastic, and mechanical hot water injection. Soil amendments were 3 levels (1x, 2x, 3x) of sulfur additions designed to lower pH and sawdust additions to lower soil nitrogen availability. We quantified nonnative and native species composition and cover, seeded a uniform mix of native sandplain grassland species into all plots, and followed plant responses for two years.

Results/Conclusions

Percent cover of nonnative species decreased from 100 to 83% across treatments. However, nonnative species richness increased, on average, by three species per plot in every treatment, indicating that the seed bank contained nonnative species that were not originally present.  Native species also increased on average, in cover from 3% to 22% and in richness by seven species across all treatments.  Emergence of seeded sandplain species occurred in every treatment except the control. The tilled treatments showed greater response of native species richness than glyphosate, plastic, and hot water treatments.  Native species cover and recruitment increased in response to the increasing levels of carbon but showed no trends in response to sulfur.  Our results suggest that native species establishment in abandoned agricultural lands may be limited by seed dispersal as well as availability of open sites for recruitment.  While the treatments reduced nonnative biomass, none completely eliminated nonnative species that were originally present.  Thus, understanding both competitive interactions and the effects of soil conditions in the relative performance of native and nonnative species will be important for predicting the success of native species persistence over the long term.