PS 76-171
The distribution of invasive Celastrus orbiculatus in an anthropogenically disturbed riparian ecosystem
The Hudson River Estuary has been colonized by numerous terrestrial invasive plant species, due in part to its history of anthropogenic and natural disturbance riparian dynamics. This study investigates the spatial patterns of a widespread invasion by Oriental (or Asiatic) bittersweet (Celastrus orbiculatusThunb) in Schodack Island State Park, Rensselaer and Columbia Counties. The park is home to rare species and communities, several of which are threatened by the encroachment of bittersweet. Bittersweet populations were mapped and surveyed on a fixed grid throughout the island, to determine distribution patterns. Local experimental tests were carried out to investigate the establishment limitations of new populations. Five site types were selected based on substrate properties (dredge materials and forest floodplain) and local bittersweet densities. Ten greenhouse-grown seedlings (transplants) and 100 seeds were planted at each site, and then tracked for their survival and growth.
Results/Conclusions
Transplants survived and grew at similar rates among the five experimental site types, but seed germination varied, with the highest rate in the dredge materials zones (p=0.05). Mean stem densities of established adult bittersweet were about 50% higher (p= 0.002) in sites with dredge materials substrate. Higher levels of Ca, Mg, and Mn may be attributable to greater clay content in native floodplains, in addition to a higher fraction of organic matter. Likewise, highly soluble nitrate may be bound less tightly in the sandy soild of dredge material origin. Due to the invasive plasticity of bittersweet seedlings and adults, these results indicate that controlling bittersweet expansion areas should be focused in anthropogenically disturbed or dredge material-covered areas, which is home to a large fraction of the island's invasive plant communities.