Documenting the regional and local distribution of Rosa multiflora and Kalmia latifolia in West Virginia, Ohio, and Pennsylvania forests along a soil fertility gradient

Background/Question/Methods

Soil fertility gradients have received less attention than soil moisture gradients, topography, and local disturbances as factors that define vegetation distribution patterns. A summary of Forest Inventory and Analysis data has confirmed vegetation gradients for Kalmia latifolia, an interfering native shrub, and Rosa multiflora, a nonnative invasive shrub, in West Virginia, Pennsylvania, and Ohio.The purpose of this research is to determine whether or not a soil fertility gradient may help explain these vegetation patterns.We evaluated the regional scale by sampling four 1-km transects in each of the three states. The local scale was evaluated by using K. latifolia and R. multiflora as focal species. Ten shrubs of each species in each state were randomly selected and plots were established using each shrub as the center point. The transect and shrub plots were randomly selected in forests that were at least 70 years of age.  Soil samples were collected from the B horizon. Additional data collected included species richness and diversity, canopy and subcanopy tree basal area, aspect, slope, elevation, light, and canopy opening. Data were analyzed using a generalized linear model.

Results/Conclusions

Results of both the regional scale and shrub-specific local scale confirmed a soil pH and fertility gradient, revealing higher soil pH, Ca, K, and Mg values in Ohio followed by Pennsylvania then West Virginia. An inverse relationship was found for total N and C as well as Mn, Fe, and Zn. Rosa multiflora plots were significantly associated with higher levels of plant species diversity, soil pH, Ca, K, and Mg than found for K. latifolia. Rosa multiflora’s tissue was typically higher in total N, as well as Ca, P, K, Mg, and Fe. Kalmia latifolia was limited to relatively extreme acidic sites in Ohio, even more acidic than the K. latifolia plots in Pennsylvania and West Virginia. Kalmia latifolia may be limited by Mn and Zn. However, the extreme acidity on which K. latifolia was found in Ohio may also result in absorption of Mn at toxic levels. These results enable us to predict that invasion of R. multiflora is more likely in areas of high soil fertility. Invasion of K. latifolia is more limited and less likely in areas of high soil fertility or low acidity. While elevation, moisture gradients, and historic disturbances play an important role in the current distribution of both species, our data show that soil pH and nutrients are also significant factors.