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We investigated the microclimate, gas exchange, and growth of field-grown Norway maple (Acer platanoides L.) and green ash (Fraxinus pennsylvanica Marsh) trees nonsheltered, and in brown and white shelters. Shelter microclimate—air temperature (Ta), vapor pressure deficit (VPD), and radiation—and tree leaf area, growth in diameter, stomatal conductance (gs), and photosynthesis were measured during the first growing season after bare-root transplanting. Bark temperatures in midwinter were also measured. Treeshelter microclimate was greenhouse-like compared to ambient conditions, as shortwave radiation was lower, and midday Ta and relative humidity were higher. Although trees in shelters had greater shoot elongation and higher gs than trees grown without shelters, photosynthesis was not different. White shelters allowed 25% more shortwave radiation penetration and increased Ta by 2 to 4 °C and VPD by 0.5-1 kPa over brown shelters. However, tree growth and gas exchange generally were not affected by shelter color. Winter injury was increased for trees in shelters and varied with species and shelter color. Both species exhibited shoot dieback in shelters the spring following a winter where bark temperatures varied 40 to 50 °C diurnally. More new growth died on maple, particularly in white shelters where several trees were killed. These data suggest that supraoptimal summer and winter temperatures may reduce vigor and interfere with cold tolerance of some species grown in shelters.
Bigtoothmaple(Acer grandidentatum Nutt.) is of interest for its fall color and potential use in water-conserving landscapes. Clonal propagation of desirable selections would be beneficial. Since bigtooth maple commonly self-propagates by layering, we explored mound layering as a means of vegetative propagation. A stool bed was established in 1999 with seedlings grown from northern Utah seed. Beginning in 2001, seedlings were dormant pruned to their base and shoots allowed to grow until early July, when treatments were applied. At the time of treatment application for the reported experiments, shoot bases were girdled with 24-gauge copper wire, covered with conifer wood shavings, and kept moist during the growing season. The effects of rooting hormones and enclosure of the rooting environment on rooting were examined. On 7 July 2002, 32 trees were randomly selected and the four tallest shoots within each tree were treated with either 0, 1:5, 1:10, or 1:20 (v/v) solutions of Dip-N-Gro© rooting hormone (1% IBA, 0.5% NAA, boron). There was no significant difference in rooted shoots between treatments and 81% of the trees had at least one rooted shoot. On 9 July 2004, 39 trees were selected and two shoots per tree were girdled. One-half of the stool bed area was treated by underlaying the shavings with BioBarrier© (17.5% trifluralin a.i.). Measurements on 12 Nov. 2004 showed no apparent treatment effect on rooting and 90% of the trees had at least one rooted shoot. This research demonstrates that mound layering is an effective means of rooting shoots of juvenile bigtooth maples. Further research will examine the effectiveness of the technique in propagating mature clones.
Shepherdia ×utahensis ‘Torrey’ (‘Torrey’ hybrid buffaloberry) is an actinorhizal plant that can fix atmospheric nitrogen (N2) in symbiotic root nodules with Frankia. Actinorhizal plants with N2-fixing capacity are valuable in sustainable nursery production and urban landscape use. However, whether nodule formation occurs in S. ×utahensis ‘Torrey’ and its interaction with nitrogen (N) fertilization remain largely unknown. Increased mineral N in fertilizer or nutrient solution might inhibit nodulation and lead to excessive N leaching. In this study, S. ×utahensis ‘Torrey’ plants inoculated with soils containing Frankia were irrigated with an N-free nutrient solution with or without added 2 mm ammonium nitrate (NH4NO3) or with 0.0 to 8.4 g·L−1 controlled-release fertilizer (CRF; 15N–3.9P–10K) to study nodulation and plant morphological and physiological responses. The performance of inoculated plants treated with various amounts of CRF was compared with uninoculated plants treated with the manufacturer’s prescribed rate. Plant growth, gas exchange parameters, and shoot N content increased quadratically or linearly along with increasing CRF application rates (all P < 0.01). No parameters increased significantly at CRF doses greater than 2.1 g·L−1. Furthermore, the number of nodules per plant decreased quadratically (P = 0.0001) with increasing CRF application rates and nodule formation were completely inhibited at 2.9 g·L−1 CRF or by NH4NO3 at 2 mm. According to our results, nodulation of S. ×utahensis ‘Torrey’ was sensitive to N in the nutrient solution or in increasing CRF levels. Furthermore, plant growth, number of shoots, leaf area, leaf dry weight, stem dry weight, root dry weight, and N content of shoots of inoculated S. ×utahensis ‘Torrey’ plants treated with 2.1 g·L−1 CRF were similar to those of uninoculated plants treated with the manufacturer’s prescribed rate. Our results show that S. ×utahensis ‘Torrey’ plants inoculated with soil containing Frankia need less CRF than the prescribed rate to maintain plant quality, promote nodulation for N2 fixation, and reduce N leaching.
Fertilization effects on mycorrhizal formation by Tricholoma virgatum with three pine species were studied. Inoculum was mixed into a 1 peat: 1 vermiculite media (1:9, v/v), prior to seeding in 160-cm3 “Leach Containers”. Four nutritional regimens were used: Full-strength Ingestad solution with 10% P, 10% Ingestad solution, modified-exponential Ingestad, and a slow-release fertilizer (Sierra TM, 17N-6P-1OK). Seedlings were harvested at 3, 4, and 5 months after sowing. Tricholoma inoculation resulted in 11% of the short roots of all species forming ectomycorrhizae (ECM) and 40% of the seedlings being colonized. P. sylvestris and P. nigra had significantly more ECM than did P. ponderosa, The number of ECM increased from the 3rd to the 4th month, but no increase occurred after the 4th month. Treatment with full-strength Ingestad/10% P yielded the largest seedlings and the least ECM, while exponential and 10% Ingestad produced smaller seedlings with the most ECM. The slow-release fertilizer treatment resulted in trees with intermediate growth and ECM formation. No differences in growth were found between inoculated and uninoculated trees.
Shepherdia ×utahensis ‘Torrey’ (hybrid buffaloberry) is an actinorhizal plant that can form symbiotic nodules with the actinobacterial genus Frankia. However, little research has been conducted to investigate the presence of Frankia in their nodules and the effects on plant growth. In this study, plants were grown in a Metro-Mix® 820 substrate and inoculated with soils collected from Mohave County, AZ, or in a low organic-matter substrate inoculated with soils from North Logan, UT. The presence of Frankia was quantified using PolF/PolR primers to amplify their nitrogenase (nifH) gene sequences. In the Metro-Mix 820 substrate, plants irrigated with nitrogen (N)-free Hoagland’s solution at pH 6.5 formed nodules at week 12 after experiment initiation, whereas those receiving the same solution with 2 mm ammonium nitrate (NH4NO3) appeared healthy, but no nodules formed. In the low organic-matter substrate, nodules formed in 5 weeks when plants were irrigated with N-free Hoagland’s solution at pH 7.5. Four 300-bp fragments of query sequences (SU1, SU2, SU3, and SU4) were obtained from nodules. When compared with nifH gene sequences reported in the literature using the Basic Local Alignment Search Tool (BLAST), more than 90% similarity to the nifH of Frankia spp. was obtained. The Frankia strains in the nodules shared nifH sequences similar to those of the same host-specific group of Shepherdia. Furthermore, Frankia strains with similar nifH genes have been reported in nodules of Shepherdia argentea (silver buffaloberry). Additionally, Frankia strains belonging to cluster 3 infective strains consisting of Elaeagnaceae and Rhamnaceae infective Frankia showed high similarity to the query sequences. This research demonstrates that nodulation of S. ×utahensis is inhibited at 2 mm NH4NO3. Apart from N, nodule formation may be associated with the substrate type and pH of the nutrient solution. Based on nifH gene sequence amplification, Frankia strains in the root nodules may have the potential to fix atmospheric nitrogen (N2). These Frankia strains have signature gene sequence characteristics of Elaeagnaceae-infective Frankia, suggesting that S. ×utahensis shares Frankia strains similar to its parents.
The green industry in Utah is a large and diverse group that ranges from nursery/greenhouse growers and retailers to landscape maintenance and design professionals to irrigation and turf industry professionals. Because of the size and diverse membership of the Utah green industry, extension faculty are challenged to gauge the needs and attitudes of the industry as a clientele group. In 2007, we conducted a mail survey of the Utah green industry to identify the learning preferences of industry members, to better understand the structure and extent of Utah green industry businesses, and to elicit industry perceptions about present and future challenges to success. We found that the service sector is a significant component of Utah's green industry, and that extension-based short courses can be used to provide more advanced and targeted education to specific industry groups. Drought/water issues and labor shortages were viewed as significant challenges to the future of the green industry, and these could be used as a foundation for building strategic alliances between extension and the green industry in Utah. Results of our survey will be useful to green industry professionals and extension educators that deal with green industry education, particularly in states with service- rather than production-oriented businesses.
In response to a perceived need for the development and introduction of superior plant accessions for use in sustainable, low-water landscaping, land-grant universities in Colorado, Idaho, and Utah, have supported plant development programs. Each of these programs has unique characteristics and protocols for releasing plant materials and obtaining royalties to further support research and development. Colorado State University (CSU) is part of the Plant Select program, which evaluates and promotes native and non-native plants for use in low-water landscapes. Selected plants are released to commercial members who pay a membership fee and royalties for access to the selected plants. The University of Idaho focuses on selecting and evaluating native herbaceous perennials, which are then released through a contract and royalty program with a local nursery. Utah State University uses the Sego Supreme program to select, propagate, and evaluate native plants. Selected plants are released to interested growers who pay a royalty for production rights.
The potential of bigtooth maple (Acer grandidentatum) as a small, water-conserving landscape tree for the western United States is limited by the selection of superior accessions from a morphologically diverse gene pool and the ability to propagate wild plants in a nursery environment. Superior accessions were selected based primarily on red fall color. Aerial digital images taken during peak fall color in 2007 and 2008 were synchronized with flight global positioning system (GPS) track files using digital image editor software and visually compared with corresponding satellite images to determine the exact latitude and longitude of selected trees on the ground. Trees were physically located using GPS technology then visually evaluated for initial selection. Criteria included fall color, habitat, relative disease and insect resistance, bud quality, and plant form. From 56 observed trees of interest, six were selected for propagation. Through time-course experiments using multistemmed, bigtooth maple seedling rootstocks in a coppiced stoolbed, the optimum time for chip budding scions of wild accessions in northern Utah was determined to be July through mid-August. Further evaluation of accessions for use in the landscape industry is required.