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Sick-a-more? Effects of junipers on sycamore growth rates

Ellen Buening, Linda Sebisaho, Jia Qi (Blair), Ashley Junger, Cassidy Ragains


Sycamore trees grow in eastern and central U.S.  Prefers sedimentary soil.  Grows alone or in small groups of other trees.  Intermediate shade tolerance.

Juniper trees are conifers.  Tolerant of climate and soil.  Limestone rock soils.  Competitive.

Previous studies have shown pH differences in soil between sites where juniper and sycamore grow.  


Junipers growing next to sycamore trees will have a negative effect on growth of sycamore trees.

Research sites

Section A:  moist soil, limited sunlight, moderate competition
Section B:  moist soil, unlimited sunlight, low competition
Section C:  rocky soil, moderate competition
Section D:  rocky soil, high competition, low sunlight 


Selected paired and unpaired sycamore trees in different areas.  "Paired" refers to sycamore and juniper less than 3 meters apart and juniper at least 25 percent the height of the sycamore.

Used an increment borer, clinometer, measuring tape.  Cored individual trees.  Measured width of growth rings to estimate growth rates.  Measured height, circumference, distance between trees.


There was no difference in growth rates between paired and unpaired sycamore trees (p = 0.36).


Growth rates of sycamores differed significantly among the four sites (p = 0.006).


We observed no effect of junipers on growth of sycamore trees.  

Junipers grow best in limestone soil.  Perhaps junipers are growing better in area C, creating more acidic soil conditions which may be hurting the sycamores.  There was a severe summer drought several years ago; this may have affected growth rates of the sycamore trees

Area B had the most distinct growth conditions.  Closer to the quarry bottom, the soil becomes rockier with higher limestone content and less water retention.  Soil with very large particles and more rocks reduces water retention.  The soil may not hold enough water needed for optimal growth of sycamores.  Juniper trees, on the other hand, can survive in a wide range of stressful conditions.

The sites contained other plants that were competing with sycamore and juniper trees.  The lack of effects of tree pairing on sycamore growth rates may have been due to the presence of another competitor with a stronger effect on juniper and sycamore trees.


Kozlowski, T. T., and S. G. Pallardy.  2002.  Acclimation and adaptive responses of woody plants to environmental stresses.  Botanical Review 68:  270-334.

Tipple, B. J., and M. Pagani.  2013.  Environmental control on eastern broadleaf forest species' leaf wax distributions and D/H (deuterium/hydrogen) ratios.  Geochimica et Cosmochimica Acta 111:  64–77.

Ware, S., et al.  1992.  Soil pH, topography, and forest vegetation in the Central Ozarks.  American Midland Naturalist 128:  40-52.

U.S. Forest Service Silvics Manual, Sycamore.

U.S. Forest Service Silvics Manual, Eastern Red Cedar.

Eastern Tennessee State University, Eastern Red Cedar.