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.
Taryn L. Bauerle and Michela Centinari
Taryn L. Bauerle and Travis D. Park
Experiential learning can be an important part of an undergraduate curriculum in the sciences. A new course, The Nature of Plants, was developed to provide students across a broad range of majors with an in-depth study of plant science both basic and applied. The course was enriched by using a local natural area as an informal learning environment. We examined whether experiential learning improved homework scores among students who participated in a field trip by asking if simply attending the field trip increased the homework score or if participation in the tree climbing exercise had any additional benefit. Our results show participating in a field trip experience when coupled with a homework assignment increased student homework scores. Moreover, the tree climbing portion of the field trip increased homework scores particularly for students not in a science major. This research supports experiential learning and the value of field trips within science courses focused on a comprehensive exploration of plants.
Taryn L. Bauerle, William L. Bauerle, Marc Goebel and David M. Barnard
Substrate moisture sensors offer an affordable monitoring system for containerized tree production. However, root system distribution can vary greatly among species within ornamental container production systems, resulting in variation within substrate readings among sensors within a container. The aim of this study was to examine the relationship of substrate moisture sensor readings in six ornamental trees to their root distribution patterns within a container. Following root anatomical analysis, tree root systems were dissected by root order as a means to separate fine (uptake) roots and coarse (transport) roots. Substrate moisture variability was measured through the deployment of 12 substrate moisture sensors per container. Of the tree species studied, we found the following two patterns of root distribution: a shallow, “conical-shaped,” root system, with the broadest portion of the root system in the shallow soil layer, and a more evenly distributed “cylindrical-shaped” root system. Root system distribution type influenced substrate moisture reading variability. Conical root systems had lower substrate moisture variability and high fine root variability, whereas the opposite was true for cylindrical root systems—most likely due to the larger, coarse woody mass of roots. We were unable to find any correlations between fine root morphological features including root diameter, length, or surface area and substrate moisture variability. However, higher specific root length was associated with higher substrate moisture variability. Classifying a tree’s root system by its growth and distribution within a container can account for variation in substrate moisture readings and help inform future decisions on sensor placement within containerized systems.
Jingjing Yin, Nina L. Bassuk, Madeline W. Olberg and Taryn L. Bauerle
In our study, we investigated whether root hydraulic conductance is related to post-transplant recovery. We used two Quercus species that differ in their transplant ability, Q. bicolor and Q. macrocarpa. Q. bicolor easily survives transplanting, whereas Q. macrocarpa often does not. We compared root hydraulic conductance after transplanting between control (without root pruning) and root-pruned, 1-year-old, small-caliper trees. We also examined the effects of transplant timing on post-transplant recovery of large-caliper trees. Hydraulic conductance in fine roots was correlated with recovery of the two Quercus species after transplanting. Six months after transplanting, small-caliper Q. bicolor trees had similar specific hydraulic conductance (K S) in fine roots compared with the K S before root-pruning, whereas fine root K S in small-caliper Q. macrocarpa trees decreased. Lower pre-dawn and midday xylem water potential in root-pruned Q. macrocarpa 6 weeks after transplanting indicates that root-pruned Q. macrocarpa experienced transplanting-induced water stress. For large-caliper trees, all Q. macrocarpa trees exhibited typical symptoms of transplant shock regardless of transplant timing, which was the result of higher vulnerability to mild water stress compared with Q. bicolor, resulting in a large reduction in fine root K S. Fine root K S in spring-transplanted Q. bicolor trees was much higher than that in fall-transplanted trees, implying spring transplanting is optimal for Q. bicolor. Other intrinsic characteristics of the species should be considered in the future when making better decisions on transplant timing such as xylem anatomy, carbon storage, rhizosphere conditions, and plant growth.
John D. Lea-Cox, William L. Bauerle, Marc W. van Iersel, George F. Kantor, Taryn L. Bauerle, Erik Lichtenberg, Dennis M. King and Lauren Crawford
Wireless sensor networks (WSNs) transmit sensor data and control signals over long distances without the need for expensive infrastructure, allowing WSNs to add value to existing irrigation systems since they provide the grower with direct feedback on the water needs of the crop. We implemented WSNs in nine commercial horticulture operations. We provide an overview of the integration of sensors with hardware and software to form WSNs that can monitor and control irrigation water applications based on one of two approaches: 1) “set-point control” based on substrate moisture measurements or 2) “model-based control” that applied species-specific irrigation in response to transpiration estimates. We summarize the economic benefits, current and future challenges, and support issues we currently face for scaling WSNs to entire production sites. The series of papers that follow either directly describe or refer the reader to descriptions of the findings we have made to date. Together, they illustrate that WSNs have been successfully implemented in horticultural operations to greatly reduce water use, with direct economic benefits to growers.
David M. Eissenstat, Denise Neilsen, Alan N. Lakso, David R. Smart, Taryn L. Bauerle, Louise H. Comas and Gerry H. Neilsen
Growers plan most of their horticultural activities around certain shoot phenological stages, such as bloom, veraison, and harvest. Timing of root growth in relation to these stages of the shoot is of interest in fertilization scheduling and in understanding carbon allocation demands of the root system. With the recent use of minirhizotron root observation tubes, a much greater understanding of patterns of root growth has been made possible. In Fredonia, N.Y., 5 years of root investigation in `Concord' grape indicate considerable variability in timing of root flushes. Root flushes could occur any time between bloom and veraison, but were generally not observed after harvest. Wine grapes in the Napa Valley exhibited similar patterns. In apple, root flushes may occur at bloom, but often not after harvest. Consequently, we rarely observed the bimodal distribution of root flushes commonly depicted in textbooks for apple and grape. Our data suggest that general perceptions of the timing of root growth may be in error.