Understanding the ecological distribution range of exotic trees in an arboreal ecosystem is essential to managing natural forest resources sustainably. Forest resource mapping can be applied as a powerful tool in the identification of forest resource threat patterns, and in monitoring ongoing changes associated with a landscape. This study offers an insight on Russian-olive and its impact on a spatially bound ecosystem, namely, Bismarck–Mandan Wildland–Urban Interface (BMWUI). Data from the National Agricultural Imagery Program collected in 2005 and 2010 and in situ reference data were used to estimate the potential habitat of Russian-olive using ArcGIS ArcInfo® 9.3 (ESRI, Redlands, CA). Russian-olive plants are discernible on aerial photographs with a fine spatial resolution because of silvery gray-green leaves in the upper strata of their canopies. Results showed that Russian-olive occupied 110 ha (272 acres) in BMWUI in 2005 and of that, 13 ha (12%) was in inundated habitats. In addition, Russian-olive in 2010 covered 125 ha within the BMWUI and of that, 25 ha (20%) was in inundated habitats. Russian-olive showed a close association with the silt loam and silty clay soil type, which occurs along the Missouri River floodplain. Our findings revealed that the species is well established in riparian habitats and other open habitats such as roadside and agricultural lands. There is a greater likelihood of lateral spread of Russian-olive throughout the BMWUI that may require active management to avert undesirable conservation impacts.
Nomenclature: Russian-olive, Elaeagnus angustifolia L.
Management Implications: Understanding vulnerable habitats for rapid invasions by exotic species is crucial for land managers to identify and implement successful management strategies. Habitat suitability modelling is useful for identifying critical arboreal ecosystems that can be targeted with surveillance, prevention and eradication measures to avoid wide-scale infestations. This study provides valuable baseline information of preferred habitats for current and potential future distribution of Russian-olive within the Bismarck-Mandan Wildland Urban Interface (BMWUI) on the banks of Missouri River. For example, we found that riparian habitats are more suitable for establishment of Russian-olive than terrestrial habitats. Forest managers can use our distribution data to monitor how Russian-olive colonization of an area may impact growth and survivability of native trees such as cottonwood and willow at similar sites. North Dakota Parks and Recreation Department's Natural Heritage Inventory (NDNHI) has carried out botanical surveys, for example, creating an inventory of rare plants, and our results are important to evaluating whether Russian-olive has also been threatening rare plants in this region. Weed managers in other regions of the Missouri River can compare our results with their data to create strategies to manage Russian-olive regionally through prescribed restoration programs. This study also provides valuable information from which city and wildlife managers can make better management plans to conserve native plants, protecting them from the invasive species in the riparian and upland regions.