IMPACTS OF JAPANESE KNOTWEED (FALLOPIA JAPONICA) AT KOCHER PARK, COLUMBIA COUNTY, PA

Kocher Park is located in Columbia County, Pennsylvania, north of the town of Bloomsburg. The 30-hectare park lies in the floodplain of Fishing Creek, and is bisected by Stony Brook, which flows through the property. The invasive herbaceous perennial plant Japanese knotweed (Fallopia japonica) is spreading within the park, and has the potential to change the ecosystem services provided by the floodplain. To date little is known about the relationship between invasive emergents like knotweed and sediment trapping on floodplains. This study maps the extent of knotweed in the park and assesses the amount of sediment trapped on knotweed-dominated parts of the landscape.

Mapping of fluvial landscapes invaded by knotweed versus unaffected areas was completed in Fall of 2018. F. japonica stands are particularly abundant in areas of slightly lower elevation and towards the Northern portion of the park. Kocher Park was flooded by nearby Fishing Creek during the Summer of 2018, and accumulation of flood-related sediments was measured at five 2-by-2 meter study sites selected randomly. At each site samples were collected from associated micro highs (n=3) and lows (n=3). Each site was divided into four quadrants for knotweed stem counts, and soil samples were collected for physical (bulk density, particle size distribution, loss on ignition) and chemical analyses (ambient pH, x-ray fluorescence). The depth of sediment deposited in 2018 was measured relative to previously stable buried soil surfaces (A horizons or litter layer) and flood water heights were estimated by identifying debris caught on bark and tree limbs at the study sites. Floodwater height averaged 2.5-3 meters. Most recent sediment accumulation, ranging from 0.5 to 15 cm, was concentrated on the natural levee near the bank of Fishing Creek and in linear topographically low overflow channels of Fishing Creek and Stony Brook. Sediment depths did not correlate with the abundance of knotweed, suggesting this invasive species does not alter sediment trapping during floods. In our ongoing research we will quantify trace metals and phosphorus via x-ray fluorescence to calculate the water quality improvement ecosystem services provided by the floodplains at Kocher Park.