Arboriculture & Urban Forestry 33(3): May 2007 203 survivability and establishment (Kraus 1998). However, en- vironmental factors can increase plant stress and delay estab- lishment of woody plants in landscapes (Montague et al. 2000b). Little information is available on whether organic mulch influences gas exchange and establishment of newly transplanted containerized shrub species. In addition, infor- mation is lacking on the amount of water required to establish container-grown woody shrub species in landscapes. There- fore, this research was conducted to document plant gas ex- change and growth of four container-grown shrub species exposed to three irrigation levels and soil surfaces covered with organic mulch or left bare. MATERIALS AND METHODS Research was conducted in field plots over two growing sea- sons (2001 and 2002) at the Texas A&M research and Ex- tension Center in Dallas, Texas, U.S. Each year, nine land- scape plots were used. Each whole plot (3 m × 4 m [9.9 ft × 13.2 ft]) was constructed with timber frames (10 cm × 10 cm × 3m[4in × 4 in × 9.9 ft]) around each plot. Using corru- gated sheet fiberglass (buried 30 cm [12 in]) below soil level and raised 30 cm [12 in] above soil level), each plot was further divided in half into two subplots (forming 18 sub- plots). Soil consisted of an Austin silty clay (fine-silty, car- bonatic, thermic Udorthentic Haplustolls). Drip irrigation (model R17-35B030; Netafim Inc., Fresno, CA) was installed on a 30 cm (12 in) grid inside each plot. Irrigation tubing was equipped with one 3.8 L/h−1 (1 gal/h−1) pressure- compensating emitter every 30 cm (12 in). Each whole plot was fitted with one flow meter (model Bermadon MTA; Ber- mad Inc., Anaheim, CA) and a 138 kPa (20 psi) pressure regulator (model PMR 20 MF; Senninger Irrigation, Inc., Orlando, FL). An automated weather station (Model Met- data1; Campbell Scientific, Inc., Logan, UT) located on the experiment site was used to monitor weather conditions. Data received from this weather station were used to calculate weekly cool-season grass reference evapotranspiration (ETO). Grass reference ETO was calculated using ETO cal- culation software (Allen 2000). Irrigation to each plot was applied twice each week at three rates: 100% ETO (high), 75% ETO (medium), and 50% ETO (low) replacement rates (based on total ETO [mm] for the previous 3 or 4 days and plot area [m2]. Before irrigation calculations, daily precipita- tion depth was subtracted from total ETO. Mid-May 2001 and 2002, three uniform plants of four different woody shrub species commonly grown in the region were planted in each plot. All plants were selected from a local nursery and were grown in 3.8 L (1 gal) containers. Species included crapemyrtle (Lagerstroemia indica ‘Vic- tor’), forsythia (Forsythia × intermedia ‘Lynwood’), photinia (Photinia × fraseri), and Vanhoutte spirea (Spiraea × van- houttei). Shrubs were planted in rows (three plants of the same species in each row and four rows in each plot) 60 cm (24 in) apart. Within each subplot, species were randomly assigned to each row. After planting, 10 cm (4 in) of cypress bark mulch (shredded, 7.6 to 10 cm [3 to 4 in] long) was placed on one randomly selected subplot of each whole plot. Mulch was maintained at this height throughout the experi- ment and weeds that appeared after planting were removed by hand. Throughout the experiment, pruning was not performed and fertilizer was not applied. Throughout each growing season, midday stomatal con- ductance (GS) was measured each week. Measurements were taken twice each week (two species each day) on the same day but before application of irrigation. Midday GS was mea- sured on three recently mature full sun leaves from two ran- domly selected plants of each species within each subplot. Midday GS measurements began at 1200 P.M. each day. Mid- day GS was measured with a steady-state porometer (Model 1600; LI-COR Inc., Lincoln, NE). Midday GS measurements began with the random selection of one subplot. Measure- ments were made on two species within the selected subplot and then another subplot was randomly selected. Midday GS concluded each day around 230 P.M. At the conclusion of each year’s experiment (1 October), each plant was carefully uprooted and prepared for dry mass analysis. Soil was washed from roots and when clean of soil particles, roots and shoots of each plant were placed in separate paper bags and placed in a drying room. Plant material was dried at 70°C (158°F) for 1 week and weighed. Each species was treated as a separate experiment (Arnold et al. 2005); therefore, species comparisons were not statis- tically analyzed. Midday GS and growth data of each species were subjected to analysis of variance appropriate for a split plot design (large plotwhole plot, mulch treatmentsplit plot) arranged in completely randomized blocks with three irrigation levels and two mulch treatments for each species. Therefore, there were three blocks and each block contained three plants of each species/irrigation/mulch combination (nine plants for each species/irrigation/mulch treatment). Data were analyzed using the general linear models proce- dures in the SAS System for Windows (release 8.01; SAS Institute, Inc., Cary, NC). For each species, there were no irrigation/mulch treatment interactions. Therefore, only main effect data are presented. Midday GS for each species/ irrigation treatment combination was taken as the mean of 18 measurements and midday GS for each species/mulch treat- ment combination was taken as the mean of 27 measure- ments. Midday GS data were plotted against weeks after transplanting (WAT). For growth data, if significant differ- ences were found, means were separated by Fisher’s least significance difference procedure (P 0.05). Daily midday GS and shoot and root mass data from each season produced similar results. Therefore, only data from the 2001 growing season are presented. ©2007 International Society of Arboriculture
May 2007
| Title Name |
Pages |
Delete |
Url |
| Empty |
Ai generated response may be inaccurate.
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success.
Downloading PDF
Generating your PDF, please wait...
This process might take longer please wait
