Russian Olive Fruit Production in Shelterbelt and Riparian Populations in Montana

Abstract

Russian olive (Eleagnus angustifolia) is a conflict tree species: it is invasive in riparian habitats throughout the western U.S., but is often considered desirable in uplands of the northern Great Plains (e.g. soil stabilization and providing windbreaks). Desirable and invasive populations of Russian olive have different demographic and ecological characteristics that will affect the persistence of biological control organisms. Current biological control development for Russian olive focuses on fruit-reducing agents anticipated to slow or halt the spread of invasion without causing individual tree mortality. Population demography data collected from upland and riparian populations of Russian olive from 2010-2012 show that fruit production is more variable among upland populations, with zero or few trees setting fruit in 2010. A greater degree of abiotic stress in upland populations (lower precipitation/water table, and higher temperature) may cause more variable fruit production compared to riparian populations. The spatial and temporal scale of resource availability (i.e. fruit production) differs between upland and riparian populations. A biological control agent would require very high dispersal ability to persist in upland populations with greater spatial separation and more variable fruit production. In contrast, agent dispersal capacity may be less important in riparian populations with lower spatial separation and less variable fruit production. Because rivers differ in degrees of spatial variability, we may expect differences in biological control agent persistence among drainages. Using ecological and demographic data of host resources with models of herbivore population persistence could provide a novel approach to resolving conflicts in invasive species management.