| dc.description.abstract | Juniperus virginiana L. (eastern red cedar) is a species of interest throughout North America as a result of its rapid encroachment into historic grasslands, but the effects of nurse trees on J. virginiana seedling recruitment and survival patterns have not been characterized. Understanding spatial (in relation to nurse trees) and temporal (across seasons) seedling dynamics will not only contribute to our understanding of how this species is so successful in habitats generally unfavorable to woody plants, but will also aid in efforts to eradicate it from pastures and grasslands. J. virginiana has expanded into much of Kessler Atmospheric and Ecological Field Station (KAEFS) in central OK, a region characteristic of the southern Great Plains. We tracked the emergence and mortality dynamics of more than 1700 J. virginiana seedlings underneath and just outside the canopies of 173 potential nurse trees, and collected corresponding environmental and microclimate data. We found significantly more seedlings directly underneath J. virginiana canopies than outside the dripline. Survival was greater than mortality in each census period, and on average mortality occurred in the smallest seedlings regardless of location. J. virginiana tree gender, height (m), canopy area (m2), DBH (cm), and age were all significantly related to seedling presence and abundance, with larger, female trees associated with the greatest number and density of seedlings. Microclimate conditions were significantly drier, cooler, and darker underneath tree canopies than in open environments, and tree characteristics indicative of stand density and tree position within the canopy were significantly correlated with the degree of microclimate modifications. However, specific microclimate variables could not be quantitively linked to, nor were they useful predictors for, seedling spatial dynamics. This study marks the first time J. virginiana seedling dynamics have been characterized in a southern Great Plains grassland by tracking native cohorts spatially and temporally without manipulation. | en_US |
