Factors influencing the establishment and survival of native hardwood tree seedlings of the Kentucky Inner Bluegrass blue ash-oak savanna-woodland

Background/Question/Methods

Historical floristic surveys and anecdotal evidence suggest that the dominant habitat of the Inner Bluegrass Region of Kentucky was a savanna-woodland community. However, since the time of European settlement 99% of this community has been converted to agricultural or urban land uses and remaining savannas have been experiencing a lack of recruitment of later seedling cohorts. Currently only remnant tracts of Bluegrass savanna-woodland remain, primarily in nature preserves, of which Griffith Woods in Harrison Co. KY is the largest and best example. A long-term restoration ecology project has been established at this site to look at how various biotic and abiotic factors influence native hardwood tree seedling survival.

In March of 2011, 6,168 seedlings of fourteen different hardwood tree species were planted in an experimental block-plot design to assess how ecological factors affect their survival. Initial site conditions were documented through soil sampling, dried vegetation biomass, and surrounding vegetation community classification. How these factors influenced initial seedling survival are the specific aims of this preliminary research. This project is being conducted to determine what factors contribute to successful ecological restoration of remnant savanna tracts and our research will describe potential practices that will maximize seedling survival in restorative tree plantings. We look to evaluate how soil parameters have influenced the surrounding grassland vegetation and seedling survival in order to describe successful practices for Bluegrass savanna-woodland restoration.

Results/Conclusions

Initial seedling survival three months after planting indicate that 13 of 14 species experienced high survival (>90%). Soil analyses show that blocks did vary significantly in a multitude of parameters (Ca, Mg, P, Zn, pH, SOM, total N) and there were moderate correlations between overall seedling survival and soil pH, Mg, and Zn. However, there were not any relationships between soil parameters and the biomass, species richness, and diversity of surrounding vegetation.

These results suggest that soil conditions can influence restorative seedling plantings in the Kentucky Inner Bluegrass. Soil parameters should be considered, but tree species and additional environmental factors probably influence initial seedling survival as well. However, if attempting to establish a semi-native assemblage of grasses and forbs, soil conditions are less of a determining factor in their success. By restoring native Bluegrass savanna-woodland habitat one can reestablish ecological function by providing wildlife habitat, forage, and mast while also supporting native tree populations that are failing to naturally recruit subsequent age classes.