Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 14, 2002
Publication Date: December 1, 2002
Citation: HYDER, P.W., FREDRICKSON, E.L., ESTELL, R.E., LUCERO, M.E. TRANSPORT OF PHENOLIC COMPOUNDS FROM LEAF SURFACE OF CREOSOTEBUSH AND TARBUSH TO SOIL SURFACE BY PRECIPITATION. JOURNAL OF CHEMICAL ECOLOGY. 2002. V. 28(12). P. 2469-2476. Interpretive Summary: During the last 100 years, many Chihuahuan Desert grasslands have been replaced by desert scrub conditions. As a result of this change, there is a loss in forage productivity, increased soil erosion, and a decline in air quality. One possible mechanism by which shrubs replace grasses is through the release of compounds that interfere with the establishment, growth and development of neighboring plants. Our objective was to examine the movement of biologically active secondary compounds from the leaf surface of two increasingly dominant desert shrubs, creosotebush and tarbush, to the surrounding soil by rainfall. We found that low concentrations of secondary compounds were transported to the soil by rainfall falling through the shrub canopy with greater amounts found in water funneled down the branches to the base of the plant. At present, we are uncertain how long these compounds persist and their effects once in the soil. Due to the biological effects ascribed to some compounds in the class of chemicals tested, we feel that concentrations are sufficient to warrant further study. Work of this type may help understand processes promoting the continued degradation of desert grasslands.
Technical Abstract: During the last 100 years, many desert grasslands have been replaced by shrublands. One possible mechanism by which shrubs outcompete grasses is through the release of compounds that interfere with neighboring plants. Our objective was to examine the movement of secondary compounds from the leaf surface of creosotebush and tarbush to surrounding soil surfaces via precipitation. Units consisting of a funnel and bottle were used to collect stemflow, throughfall, and interspace precipitation samples from 20 creosotebush (two morphotypes) and 10 tarbush plants during three summer rainfall events in 1998. Precipitation samples were analyzed for total phenolics (both species) and nordihydroguaiaretic acid (creosotebush only). Phenolics were detected in throughfall and stemflow of both species with stemflow containing greater concentrations than throughfall (0.088 and 0.086 mg/ml for stemflow and 0.022 and 0.014 mg/ml for throughfall in creosotebush morphotypes "U" and "V," respectively; 0.044 and 0.006 mg/ml for tarbush stemflow and throughfall, respectively). Nordihydroguaiaretic acid was not found in any precipitation collections. Our results show that phenolic compounds produced by creosotebush and tarbush can be transported to the soil surface by precipitation, but whether concentrations are ecologically significant is uncertain. Secondly, nordihydroguaiaretic acid was not present in the runoff from creosotebush.