597 Tree Establishment and Soil Surface Covers

Abstract

The purpose of this study is to determine the effects of a variety of commonly used soil surface covers on the establishment of Cercis canadensis L. var. texensis (Wats.) Rose. `Alba'. Containerized 23.3-L trees were planted into 1.1 × 1.5-m plots separated by metal landscape edging in 20-cm-deep raised beds constructed of exterior treated landscape timbers. Eight soil surface treatments were imposed with five replicates each. Controls included bare soil with no cover. The remaining seven treatments consisted of 8-cm depth of pine bark mulch, Trachelospermum asiaticum (Siebold & Zucc.) Nakai on 30-cm centers mulched with 8 cm of pine bark, solid sodded Stenotaphrum secundatum (Walt.) Kuntze, 8 cm of decorative gravel, 3 cm of recycled paper mulch, brick pavers underline with 5 cm of coarse builders sand (brick-on-sand), and seasonal color mulched with 8 cm of pine bark. The color rotation for summer, fall / winter, and spring is Catharanthus roseus (L.) G. Don, Viola × wittrockiana Gams., and Petunia × hybrida Hort. Vilm.-Andr., respectively. Preliminary data indicates that mulching with pine bark resulted in similar or slightly increased trunk diameter growth over that of bare soil. Brick-on-sand and the recycled paper mulch had smaller increases in trunk diameter than the other treatments. Mid-day leaf water potentials of most treatments were similar to bare soil, but the mid-day water potentials of trees mulched with recycled paper were among the most negative. All treatments except brick-on-sand trees recovered as well or better than trees in the bare soil by the next morning. Poor predawn water potential recovery of brick-on-sand trees may be due to the elevated temperatures observed in their root zone. Bare soil, recycled paper mulch, and the annual treatments had the most negative soil moisture tensions on average. The bare soil may be due to increased evaporative loose over mulched soils. The large biomass of vinca as the season progressed may account for the more negative readings in the annual seasonal color plots.