Invasive Species Compendium

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Abstract

The vascular flora and plant communities of Holthouse Woods Nature Preserve in Wayne County, Indiana.

Abstract

Holthouse Woods Nature Preserve (HWNP), owned by the Whitewater Valley Land Trust, Inc., is located along the east fork of the Whitewater River in south-central Wayne County, Indiana, in Abington Township. An inventory of the vascular flora indicates that the 8.9 ha site contains significant regional plant diversity with 331 taxa representing 227 genera and 73 families. Of the 331 taxa, 227 taxa (∼69%) are native and 104 taxa (∼31%) are non-native, and five represented first records for Wayne County. Although none of the plants documented at the site have state or federal status, one species is on the Indiana Watch List, i.e., Prenanthes crepidinea. A detailed physiognomic analysis revealed that the native species consisted of 38 woody species, 155 herbaceous vines or forbs, 33 graminoids, and one fern ally. Of the 104 non-native species, nine were woody, 74 were herbaceous vines or forbs, and 21 were grasses. The major habitats at HWNP are mesic slope woodland, floodplain woodland, a seasonal creek bed, roadside, old-field, drier woodland along River Road, and the Whitewater River corridor which includes the riverbank and sandy/gravel shoreline and two sandy/gravel islands. Floristic Quality Index (FQI) for native species was 43.3, and a mean Coefficient of Conservatism (mean C) was 2.9. For all species FQI=35.8 and the mean C=2.0. Given that most of the area is floodplain forest, these numbers indicate that HWNP is a nature preserve quality site but is being compromised by non-natives. The four most invasive non-natives were Lonicera maackii in the sloping woodland, Ranunculus ficaria var. bulbifera in the floodplain woods, and Artemisia vulgaris and Humulus japonicus along the river corridor. A census of all trees with a dbh ≥20 cm revealed that the floodplain woodland is dominated by woody species commonly characteristic of this habitat, e.g., Acer negundo, Populus deltoides, Acer saccharinum, Platanus occidentalis, Juglans nigra, Aesculus glabra, Celtis occidentalis, and Ulmus americana. A sample of trees with a dbh ≥5 cm but <20 cm suggest that A. negundo, J. nigra, and A. glabra will continue to dominate the site, but that A. saccharinum, P. deltoides, and P. occidentalis will decrease in importance.