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Tree root systems are inherently dynamic in their distribution within a soil volume. Analysis of tree root system space occupation through time can improve not only our implicit understanding of a virtually hidden portion of a plant, but influence future management decisions through a more thorough understanding of root placement within a soil volume. We compared root standing crop populations of four ornamental tree species including Acer rubrum L. ‘Franksred’ (Acer), Carpinus betula L. ‘Columnaris’ (Carpinus), Gleditsia tricanthos L. var. inermis ‘Skycole’ (Gleditsia), and Quercus rubra L. ‘Rubrum’ (Quercus) grown in a nursery mix substrate within large 57-L containers using an X-ray computed tomography (CT) approach through time. Individual root identification was performed manually on two-dimensional slices of CT scans. Our data show high variation in species total root number through time with Carpinus exhibiting the largest root population throughout the study period. However, species exhibited differences in root distribution patterns as exemplified by the shallow and horizontally more uniform rooting pattern of Acer in comparison with the highly plastic root distribution in space through time in Gleditsia. Root frequencies within 1-mm root diameter class distributions shifted by species with the most drastic differences found between high frequencies of relatively small diameter roots in Acer vs. pronounced shifts in dominate root diameter size class as found in Gleditsia and lesser so in Carpinus during a growing season. Our findings demonstrate differences in whole tree root systems space occupation non-destructively through time and highlight a disparity in how species fill a container volume during growth.

Elaeocarpus yoga Merr. (Tiliaceae) is an attractive tree indigenous to the Mariana Islands and Palau. Recently its population has declined due to deforestation, typhoon damage, and pest problems. Stem cuttings of E. yoga were taken from hardwood, semihardwood, or softwood and treated with acid or salt forms of indole-3-butyric acid (IBA) or napthaleneacetic acid (NAA) at several concentrations. The cuttings were treated with on of the following: acid form at 0.5 mL·L-1 IBA + 0.25 mL·L-1 NAA; 1 mL·L-1 IBA + 0.5 mL·L-1 NAA, 2 mL·L-1 IBA + 1 mL·L-1 NAA; salt form at 1, 3, and 8 g·kg-1 IBA/. Rooting after 8 weeks was compared among treatments. The salt form of the IBA treatment at 3 g·kg-1 produced the greatest rooting percentage, root number and length. The acid form containing both IBA and NAA produced the smallest average rooting percentage.

This study was undertaken to determine if there was a combination of tree species and mulch type which resulted in a most favorable plant water potential when plants were subjected to induced drought. Fraxinus pennsylvanica, glabrous, and F.p. `Emerald', pubescent, trees were combined with either a four cm application of medium grade gravel, shredded bark, a fused polypropylene geotextile or no mulch treatment. After the first drought period, across all treatments, the pubescent `Emerald' trees maintained less negative water potentials than the Fraxinus pennsylvanlca trees. In the species comparison the particulate mulches, shredded bark and gravel, were associated with less negative water potentials then the other treatments. Between these, the shredded bark was associated with the least negative readings. After the second consecutive dry down there was not a significant difference in predawn water potentials between the species and cultivar. However, within the `Emerald' comparison there was a non-significant difference between the particulate mulches and the shredded bark was associated with the least negative potentials.