Netleaf hackberry (Celtis reticulata) is a deciduous shrub native to the southwestern United States and northern Mexico. Previous field observations have shown limited numbers of juvenile hackberries in the wild. This could be due to low germination and survival rates, but field germination trials have not been done. In the foothills of the Wasatch Mountains in Utah, hackberry shrubs have been shown to grow in association with boulders, likely using them as nurse objects. This experimental study field-tested germination and survival rates around boulders in this area. We located 26 boulders and planted 25 hackberry seeds on the north, west, south, and east sides of each boulder (n = 2600 seeds). In the following year, we counted the number of hackberry seeds that had germinated and become established near each of the boulders' sides. Overall, germination rates were extremely low, with only 55 (2.1%) of the planted seeds germinating and only 19 (0.7%) persisting until the end of the growing season. Among the few seedlings that survived, we found even fewer on the east sides of boulders. In the west-facing Wasatch Range, the east side of a boulder typically has a higher elevation than the other sides of a boulder and may expose hackberry seedlings to excessively dry conditions and erosion as precipitation collects in the lower areas around a boulder. Additionally, the microclimate-stabilizing benefits of a boulder may be limited for plants growing on the east side of a boulder because the morning sun is blocked by the Wasatch Mountains. The highest rates of germination were found on the comparatively shady and moist north sides of boulders where greater plant competition may limit long-term establishment of hackberry seedlings. Our study furthers our understanding of nurse associations in semiarid environments and can be applied by land managers seeking to utilize hackberry in site restorations.
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1 December 2016
Netleaf Hackberry Seeds Planted Near Boulders in the Foothills of the Wasatch Mountains: Germination, Survival, and Patterns of Establishment
Michael T. Stevens,
Daniel L. Holland,
Nathan V. Tanner
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