The role of suburban horticulture in structuring plant invasions in natural areas on the suburban/wildland interface at William Floyd Estate, Fire Island National Seashore

Background/Question/Methods

Non-native plant species are known to disrupt the ecological services of native ecosystems, change the composition of native habitats, and cause declines in populations of native species. Suburban developments are routinely planted with non-native horticultural species and the horticultural trade is a well-known source of invasive plant introductions. These non-native species are planted in high abundances in residential developments, thus there is high propagule pressure of these species on adjacent natural areas.         

Understanding the spread of non-native species and predicting invasions is critical for the management of natural habitats. In order to best manage the impacts of these invasive plant species, Early Detection and Rapid Response (EDRR) has been adopted by federal agencies. This study uses surveys of both natural and residential areas to track the spread of invasive plant species and target problem species for EDRR. Our study targets species identified as high-risk by the Long Island Invasive Species Management Area for EDRR with the ultimate goal of preventing non-native plant species invasions and preserving biodiversity across Long Island, NY. We explored the similarities in non-native plant community composition between a remnant natural habitat and the surrounding residential communities to assess propagule pressure from horticultural species planted in neighborhoods.

Results/Conclusions

In the natural area, we identified 16 LIISMA-listed non-native species. The three most frequently occurring non-native species in the natural area were Lonicera japonica, Rosa multiflora and Celastrus orbiculatus.

In residential areas we identified 23 LIISMA-listed non-native species. Of 162 properties surveyed, 144 appeared to be occupied and maintained by residents; 18 appeared unmaintained or abandoned. Unmaintained properties had significantly more invasive species than maintained properties. The three most frequently occurring LIISMA-listed non-native species in surveyed residential areas were Acer platanoides, Artemisia vulgaris and Celastrus orbiculatus. Non-native species composition between the natural area and residential neighborhoods was not significantly different. However, residential non-native plant communities had significantly lower beta diversity than the natural area. Multiple regression revealed that in natural area plots distance from suburban edge and native richness were significant drivers of invasion, with plots closer to the forest edge and plots with fewer natives being more highly invaded.

Proximity to forest edge has been shown to be a predictor of invasion across many forest ecosystems. Our data are consistent with the concept of detrimental edge effects as multiple regression showed distance from edge to be a significant driver of invasion at the local scale.