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Derald A. Harp

A major problem in golf course construction is trying to optimize the use of existing vegetation, especially trees. In North Central Texas, this is made more difficult by the predominance of post oak (Quercus stellata), a tree that declines severely when cultural conditions are modified. The purpose of this project was to create a map using GPS technology of the existing trees, before final planning and construction of the golf course. In addition to the map, a database was created which would be used for future maintenance and management decisions. The GPS equipment consisted of a Trimble PRO-XRS GPS receiver and Trimble TDC-1 data logger and a Laser Atlanta laser rangefinder. Information collected for the database included tree number, latitude, longitude, number, identification, caliper, estimated height, and quality. Quality ratings were defined as 1) specimen, 2) good, 3) fair, 4) poor, 5) unacceptable. Tree numbers were placed on each tree rated above unacceptable, using metal tree tags. Height estimates were made using the vertical offset feature of the GPS equipment. Base maps were created using Pathfinder Office. Hard copy maps were printed, and digital copies were saved in raw and.dxf format for importation into AutoCAD. This map was combined with existing course plans and adjustments were made to save as many specimen trees as possible. Raw information was also imported into a Microsoft Access 97 database. This project created a database and maps that will provide important information in the future, and the development of the course with minimal loss of specimen trees.

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Ed McWilliams and Derald A. Harp

Spanish moss (Tillandsia usneoides) samples were deployed at 36 locations in a 6 × 6-grid system in northeastern Texas during the summer months of 1989 and again in the winter months of 1990. Analytical methods, including inductively coupled plasma emission spectrometry (ICP) and neutron activation analysis (NAA), were used in analyzing samples for sulfur, selenium, arsenic, sodium, and aluminum. Concentrations of most elements in Spanish moss samples were much higher in summer than winter. The highest concentrations of sulfur were found in Van Zandt, Wood, Titus, and Bowie counties. These results suggest that on average sulfur stays in the region in which it was generated. Potassium and sodium were highly correlated with latitude and seem to originate from the Gulf of Mexico.

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Derald A. Harp and Ed McWilliams

The ability of water hyacinth to remove N from nursery runoff was evaluated in two separate experiments. In Expt. 1, individual plants were placed in 10-liter ceramic containers with nutrient solutions with varying levels of N (0, 1.5, 3, 6, 12, and 24 mm). In Expt. 2, plants were placed in pools used to mimic runoff ponds. Pools were filled with 80 liters of reverse osmosis water, 2 cm of a native sandy loam, and either 48.03 or 24.015 g of 20–10–20 Peters water-soluble fertilizer. Plants in ceramic containers had no significant difference in weight gain across treatments (P < 0.05). However, the 24 mm treatment did have significantly more N remaining in the solution than other treatment levels. Plants in the pool experiments exposed to 3.0 mm N had significant increases in number of new plants produced and total biomass production over those exposed to 1.5 mm N. No differences existed in the amount of time needed to remove N because N was undetectable after 18 to 23 days at 3 and 1.5 mm.

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Derald A. Harp, Cheng Chen and Curtis Jones

Green roofs provide multiple environmental and economic benefits, such as roof surface temperature reduction, reduced internal cooling needs, storm water management, and extended life span of roofing materials. However, green roof substrates must be relatively lightweight, so it is typically coarse with limited water holding capacity. We hypothesize the physical characteristics that make the substrates successful on a roof are likely to reduce seed germination. For this study, we tested the germination of three perennial species and one annual: shasta daisy (Leucanthemum ×superbum), yarrow (Achillea millefolium), and indian blanket (Gaillardia pulchella), and pinto bean (Phaseolus vulgaris) (as a control) across five different substrates: peat/perlite/large expanded shale, compost/sand/expanded shale, compost/black dirt/expanded shale, compost/expanded shale, and peat/perlite (control). Substrate physical and chemical properties were analyzed, and a germination test conducted using a randomized complete block design, with each species/substrate combination appearing once per block. Germination was defined as seedling emergence, and monitored every 7 days for 28 days. Pinto bean had the highest germination (76.2%) across all substrates, compared with 43.4% for indian blanket, 40.4% for yarrow, and 23.0% for shasta daisy. Seed germination, across all species, was lower in green roof substrates. Germination success was very strongly correlated with seed length, seed width, and seed area, while no relationship was found between seed germination and substrate pH or electrical conductivity (EC). Therefore, it is likely that the physical characteristics of green roof substrates create poor conditions for seed germination.

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Derald A. Harp and Edward L. McWilliams

Urban areas are typically 2 to 3°C warmer than surrounding rural areas throughout the year. Winter minimum temperatures are often 4 to 5 °C warmer in the city and, during extreme episodes may exhibit differences of 12 to 13°C. Because the USDA Hardiness Maps compile readings from individual stations in an area, temperature differences may not be apparent at the local scale. This study was conducted to compare ornamental plant damage during Winter 1995–96 in Fort Worth, Texas. AVHRR 1-km thermal satellite imagery was used to determine the warmest and coolest portions in Fort Worth, Texas. Each temperature area was divided into five 0.5-km blocks on the basis of similar landscape features and plant types. During Mar. 1996, these areas were evaluated on the basis of plant damage to several species. Asian jasmine (Trachelospermum asiaticum), indian hawthorn (Raphiolepis indica), St. augustine turf (Stenotaphrum secundatum), southern magnolia (Magnolia grandiflora), and Live Oak (Quercus virginiana) were the primary species damaged. Asian jasmine and St. Augustine turf were either completely killed or severely damaged in the coldest areas but suffered only moderate or light damage in the warmest areas. Indian hawthorn, live oak, and southern magnolia suffered leaf and stem damage in the coldest areas but little to no damage in the warmer areas.

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Derald A. Harp and Edward L. McWilliams

As the World Wide Web (WWW) expands, information is rapidly becoming more accessible. Using satellite data previously required high-end computers running complex imaging software, sophisticated downloading equipment, and high monetary support. Satellite data is now available on the internet for little or no cost and can be handled on standard desktop computers using common software programs. The purpose of our project was to determine the availability and cost of different types of data and how this data may benefit horticultural instruction. Satellite data currently is archived at NASA, NOAA, the Department of Defense, the US Geological Survey, and various meteorological departments throughout the world. Satellite data such as large-scale thermal imagery can be used to determine microclimate effects within urban areas, including the cooling effects of urban plants. Natural Density Vegetation Index (NDVI) imagery can indicate changes in vegetational cover or give general indications of plant health in large areas. NASA photographic imagery can show the effects of erosion on a large scale. Higher resolution imagery can give indications of plant stresses in large plantings such as orchards or vegetable plots.

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Derald A. Harp and Edward L. McWilliams

Urban areas have average annual temperatures 2–3°C warmer than surrounding rural areas, with daily differences of 5–6°C common. A suggested reason for this temperature difference is the extensive use of concrete, asphalt, and other building materials in the urban environment. Vegetation can moderate these temperatures by intercepting incoming radiation. The influence of vegetation patterns on the magnitude of urban and micro-urban “heat islands” (UHI and MUHI, respectively) is compared for several cities including Houston, Austin, College Station, and Ft. Worth, Texas; Huntsville, Ala.; and Gainesville, Fla. Temperatures for all cities studied were greatest in the built-up areas and dropped off in suburban areas and adjacent rural areas. In Houston, surrounding rice fields were 3–5°C cooler than urban areas. Heavily built-up areas of Austin were 2–4°C warmer than parks and fields outside of the city. In all of the cities, large parks were typically 2–3°C cooler than adjacent built-up areas. Large shopping malls varied in nocturnal winter and summer temperature, with winter temperatures near door openings 2–3°C warmer, and summer daytime temperatures as much as 17°C cooler beneath trees. This effect seemed to persist at the microclimatic scale. Areas beneath evergreen trees and shrubs were warmer in the winter than surrounding grass covered areas. Video thermography indicated that the lower surfaces of limbs in deciduous trees were warmer than the upper surfaces. Overall, vegetation played a significant role, both at the local and microscale, in temperature moderation.

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Kristen L. McDowell*, Kevin Ong and Derald A. Harp

A study was conducted on the Texas A&M Univ.-Commerce campus to evaluate the effect of compost type on the spread of bermudagrass into rose garden beds. Roses were planted in an randomized complete-block design in beds amended with composts derived from yard waste, manure, poultry litter, or dairy manure, or an unamended control. The study site was free of vegetation prior to planting. No pre- or post-emergent herbicides were applied after planting. Each bed was assessed visually monthly and scored on a scale of 0 to 10, with each point equivalent to 10% coverage. A bed received a score of 10 upon full coverage. Beds amended with poultry litter and yard waste had significantly higher bermudagrass invasion and reached 100% coverage more quickly than other treatments. Some of the poultry litter beds reached 100% coverage within 40 days of planting. The control planting had significantly lower coverage than all compost treatments throughout the study.

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Derald A. Harp, Michael Wade, D. Frank Gilman and John Calahan

Caryopses of Chasmanthium latifolium removed for the florets, treated with solutions containing 0.02 M KNO3, 0.5 mM GA3, and/or 0.1 mM kinetin, placed in germination chambers at alternating temperatures of 15/30C, and percentage germination was checked at 7, 14, and 21 days. Treatments with kinetin and/or KNO3 significantly increased germination percentage over other treatment combinations. The maximum germination percentage for Chasmanthium latifolium was achieved by removing the caryopsis from the floret, treating the caryopsis with 0.02 M KNO3, and germinating for 14 days at alternating temperatures of 15/30C.

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Shadd Taylor, Derald A. Harp, Kristen McDowell and Roque Lemus

It is generally accepted that plants closer to structures benefit from the warmth emitted via imperfect insulation and solar energy reemitted as long-wave, thermal radiation. However, while claims of protection are given, little quantifiable information exists on the extent or pattern of this protection. We studied existing plantings of Trachelospermum asiaticum, an evergreen groundcover that is frequently damaged in northeast Texas. The plantings studied were part of a landscape with at least five different identifiable microclimates: 1) near building (NB); 2) mid-bed (MB); 3) bed edge (BE); 4) beneath Quercus virginiana (LO); and 5) beneath Pyrus calleryana`Bradford' (BP). We placed HOBO temperature data loggers recording one temperature per minute in each location. Following our first damaging freeze, we waited 7 days before collecting leaf samples. Leaf samples were collected by using a 25-cm square, 2 cm deep on two sides. The square was placed on the groundcover so that the top of the groundcover was level with the top of the square. All leaves and stems that extruded through the top 2 cm of the square were excised. Four samples were taken from each location, and the number of damaged and nondamaged leaves were counted for each sample. Leaves that were at least 50% discolored were considered damaged. Leaf damage data were analyzed using SAS Proc ANOVA. Leaves in the BE and BP locations showed significantly fewer live leaves than any other locations. NB leaves were virtually undamaged. Average temperatures in the BE and BP locations were 4.5 to 5 °F colder than the “near building” locations, comparable to an a or b zone in the current USDA Plant Hardiness Zone map.