We investigated growth and water relations of London plane and corkscrew willow irrigated at 80% and 0% replacement of potential evapotranspiration (ETo). In Spring 1991, whips were planted in a randomized complete-block design in a silt loam soil that was clean-cultivated through two seasons. In 1992, tree response was measured in water relations [water potential (ψ)] at predawn and midday and dawn-to-dusk stomatal conductance (gs), trunk growth, and total leaf area. Soil-water depletion was monitored with a neutron probe. Measured ETo was 98.6 mm, and actual water applied based on final leaf area was 92% and 38% of ETo for plane trees and willows, respectively. Nonirrigated trees received 4% of ETo from rain. Soil water content at the 0.90-m depth was lower in the 0% ETo treatment. There were, however, no differences in predawn ψ through the season. Plane trees had consistently higher dawn-to-dusk gs than the willows, but there were no differences in gs or midday ψ between irrigation treatments for either species. Despite lower gs, willows had greater total leaf area and trunk growth than the plane trees, but again, there were no differences among irrigation treatments. Lack of detectable water-stress effects suggests that, in the absence of competition from other species, an expanding perimeter of root growth explored new soil and allowed nonirrigated trees to exploit soil water ahead of moisture depletion within the root zone.
In 1992 and 1993, we taught the course “Landscape Management in the Interior West” by satellite in four states in the mountain west. The broadcast originated from an on-campus studio without students present, but with a two-way audio link. About one-third of the students viewed the course for credit and were located both on and off campus, while the remainder were not on campus and took the course for personal knowledge. In 1992, the course was broadcast live, but in 1993 it was restructured in a modular format and videotaped before broadcast. In 1994, videotapes from the previous year were used to offer the course on a semi-independent study basis on the Utah State Univ. campus. Videotaping the course in discrete content modules substantially improved the quality of the course by eliminating production problems and creating better content flow. The videotapes in turn provided a readily usable off-the-shelf course. Student response, however, varied with location and degree of involvement. On-campus students were critical of a perceived lack of face-to-face contact with faculty. Positive responses came from viewers in remote locations where access to college-level courses is otherwise limited. Distance education through studio-produced, videotaped lectures provides a visually engaging format that is easily disseminated. Such courses will less likely succeed on client campuses, however, unless there is an onsite individual mediating between the tapes and students.
We developed two courses, sustainable landscaping and landscape water conservation, to meet time-constrained students on campus and place-bound students off campus. Lecture material consisting of text, slides, drawings, and some video were assembled digitally using presentation software. Each course was broken into nine to10 units by topic matter, and each unit consisted of 50 to 100 individual “slides” containing visuals, text, and audio narration. The lecture material was then packaged for student consumption onto videotape and CD-ROM, and on the Web (without audio) and as hard copy. Students taking the course received a course reader of the lecture material in hard copy and CD format. Contact with the instructor was through e-mail and a threaded newsgroup on the Web. All testing was with take-home quizzes and an exam. These courses had 700 to 800 slides averaging 1 min of narration per slide, equaling 12 to 14 h of audio. Assembly time for 1 h of narration, or about 60 slides, was 20 to 30 h. These courses are taught live in a classroom, where the presentation time is doubled compared to audio narration, alternate years, and have been available every term on an arranged basis. Survey results of 40 students to date taking the course on an arranged basis, obtaining lecture material mainly through CD-ROM, showed that by a 6:1 margin, their learning experience was overall positive. However, by a 19:1 margin, students would have preferred to have taken the course with live classroom instruction. Developing digital courses such as these is only feasible if a faculty member has unequivocal and ample administrative and financial support, and is only cost-effective if there is sufficient student demand outside of conventional scheduling.
As populations become increasingly urbanized, landscape water conservation becomes more important. Landscape water consumption can increase municipal water use up to 4-fold during the growing season, and account for half the total yearly water use. Landscape water conservation is important in decreasing peak summer water demand to reduce the strain on delivery systems, and to reduce total demand so that development of new sources can be forestalled. Potential water savings from existing landscapes can be estimated by comparing historical usage gleaned from water meter readings to plant water needs estimated from reference evapotranspiration. Estimating water needs for turf is straightforward because of the few species involved and the uniformity of turf landscapes. Estimating water needs of woody plants is more difficult because of the heterogeneity of woody plants and how they are used, and woody plants respond to evaporative demand differently than turfgrass. Many woody plants will actually use less water as reference evapotranspiration increases due to stomatal closure induced by high leaf-air vapor pressure gradients. Landscape water is then conserved by either applying water more effectively in scheduling when and how long to irrigate based on estimating water use again from reference evapotranspiration, or by replacing areas in turfgrass with plants more-adapted to the existing conditions. Encouraging water conservation by end users is the final and largest challenge. Automated irrigation systems makes wasting water easy, while conserving water takes more effort. Education is the key to successful landscape water conservation.
Technology allows educators to convey information be conveyed more flexibly and visually. How to access and make use of technological teaching tools is the challenge facing educators. HortBase provides the framework for educators to create and access educational chunks. How to make use of the information in HortBase in distance teaching is a three-step process. 1) Before assembling the teaching material, the educator must decide on who the target audience is and what information to convey. Audiences on campus have higher expectations of how they learn, as they are used to live teaching and guidance, and often do not have a clear idea of what they want to learn. Off-campus audiences have lower expectations and are more focused on the information they want. 2) The educator then decides how much of the information to bring into digital form oneself and what to draw from elsewhere. Pieces of digitized information can be created by scanning existing images into the computer or created on computer with drawing programs. Once digitized images can be manipulated to get the desired look. This is a very time-consuming step, so much effort can be saved by taking created “chunks” from HortBase. 3) Finally, what medium and tools to use must be decided. Course content can be presented with slide-show software that incorporates digitized slides, drawing, animations, video footage with text. Lectures can then be outputted to videotape or broadcast via over an analog network. Alternatively, the digitized information can be incorporated into interactive packages for CD-ROM or the World Wide Web.
The fabled “wide open spaces” of the west make travel an integral, though expensive, part of most extension programs. As an alternative, Utah State Univ. has been successful in targeting a major extension audience for service via satellite teleconferences. The audience we have worked with consists primarily of landscape managers at institutional facilities, such as schools, cities, churches, hospitals, and parks, who do not have formal training in horticulture. The primary impetus and key to the success of this program is a collaboration between the university (provides content material and production) and an outside institution (provides satellite broadcasting and receives employee training). As a result, the program simultaneously reaches three main audiences: employees of the partnering institution, county extension audiences throughout the state, and any private party with a satellite who watches. Keys to the success of this program include a statewide system of satellite dishes at all county extension offices, close collaboration between content and distance-learning specialists, marketing assistance to county agents, endorsement of the program for employee training by employers, a workbook to supplement broadcast material, administrative support, and careful identification of the target audience. Concepts we are struggling with include bridging regional to national audiences and improved marketing.
We investigated gas-exchange response of norway maple and crabapple to the energy balance of turf, bark-mulch, and asphalt surfaces. In each surface stomatal conductance, leaf temperature (T1), and photosynthesis, were measured during two dawn-to-dusk studies concurrent with soil (To), top surface (Ta), and air temperature (Ta) measurements. Different properties affected the energy balance of each surface. Turf transpiration moderated To and Ts while low thermal conductivity of the mulch resulted in To similar to turf but Ts23C higher. Higher thermal conductivity of the asphalt resulted in higher To but Ts intermediate to mulch and turf surfaces. We did not detect differences in Ta, probably due to close proximity to one another that allowed substantial air mixing between treatments. Higher Ts increased longwave radiation flux that raised midday T1 of trees in the mulch and asphalt 3 to 8C higher than trees in the turf. Differences in T1 between the asphalt and mulch were minimal. Stomatal conductance declined with increasing leaf-to-air vapor pressure gradient in all trees, and was consistently lower for trees in the mulch and asphalt through the day due to larger gradients induced by higher T1. Midday photosynthesis was highest for trees in the turf and lowest for those in the mulch. Foliar interception of higher energy fluxes from mulch and asphalt surfaces apparently limited gas exchange in both species due to over-optimal leaf temperatures as compared to trees in the turf
Typically, dormant seedlings are transplanted when revegetating disturbed lands to prevent transplant shock triggered by water stress. It may be possible to transplant nondormant seedlings by inducing drought-tolerant acclimation responses such as solute accumulation. Artemisia cana and Agropyron intermedium seedlings were subjected to three different water stress preconditioning treatments. After conditioning, seedlings were dried down in their containers until leaf senescence, or were transplanted to disturbed land sites. Leaf water potential components and relative water content were measured. Following treatments, water relations parameters of preconditioned seedlings were not markedly different from controls in either species. At the end of the final dry-down, water stress preconditioning had not induced active or passive solute accumulation, prolonged leaf survival during lethal drought conditions, or differences in transplant survival under the experimental conditions of this study.
Growth of woody landscape plants is strongly affected by the underlying surface. In urban areas, plants are subjected to energy balance characteristics of a variety of surfaces. This research investigated energy balance properties of six common urban surfaces: Kentucky bluegrass, pine bark mulch, concrete, asphalt, lava rock mulch, and gravel rock mulch. Each summer over a 2-year period incoming global radiation (GW), relative humidity, and air temperature were measured over each surface, and surface reflectivity (AW), surface temperature (TS), soil temperature (TO), and soil heat flux (SF) were measured below each surface. Thermal conductivity (K) and emitted surface longwave radiation (LW) were also calculated. Surface property differences were determined by regression analysis. Incoming global radiation (independent variable) versus TS, TO, SF, LW data (dependent variable) were analyzed. Linear or quadratic curves were selected according to significance of each variable and the coefficient of determination (R2). Surface reflectivity was greatest for concrete and least for lava rock mulch, and K was greatest for asphalt and concrete and least for lava rock and pine bark mulch. Under maximum GW, regression data indicate that SF and TO would be greatest under asphalt and least under lava rock and pine bark mulch. Under similar circumstances, TS and LW would be greatest for pine bark mulch and least for Kentucky bluegrass. This research revealed that more energy was conducted into the soil below asphalt and concrete, and that a greater portion of GW was prevented from entering the soil below pine bark and lava rock mulch than below other surfaces. Due to these effects, and the lack of evaporative cooling, surface temperatures were greater, and more longwave radiation was emitted from, non-vegetative surfaces than from turf.