|Title||Volatile compounds on the leaf surface of intactand regrowth tarbush (Flourensia cernua DC) canopies|
|Publication Type||Journal Article|
|Year of Publication||2007|
|Authors||Fredrickson, EL, Estell, RE, Remmenga, MD|
|Journal||Journal of Chemical Ecology|
|Keywords||flourensia cernua dc, JRN|
Shrub expansion into desert grasslands is a serious problem resulting in loss of forage and rangeland productivity. Flourensia cernua DC (tarbush) is one such shrub contributing to the decline of Chihuahuan Desert grasslands. Our previous research has shown tarbush consumption by sheep and goats to be negatively related to leaf surface concentration of individual terpenes and epicuticular wax. Concentrations of compounds such as terpenes often change with plant age and phenology. Our objective was to examine the effect of altering the vegetative state of tarbush on volatile chemicals. Ninety tarbush plants were randomly selected and all biomass within 10 cm of the soil surface was removed from 45 plants during winter dormancy. Leaves were collected the following summer during active growth from the canopy of intact controls and resprouts. Leaf surface volatiles were analyzed by gas chromatography-mass spectroscopy and subjected to univariate analysis of variance and stepwise discriminate analysis. Of the 87 compounds present on tarbush leaves, 35 were greater in canopy samples and 16 were greater in regrowth samples based on univariate analysis (PP = 0.062) than that of regrowth (3642 vs. 4684 ìg/g DM). Nine compounds in the discriminant analysis (á-muurolene, iso-borneol, unknown#6, p-cymen-8-ol, unknown#7, sabinene, â-caryophyllene, ä-cadinene, and á-copaene) explained 95% of the variation between canopy and regrowth samples. Lower cumulative concentration of volatile compounds in canopy than regrowth samples suggests repsrouts may be less vulnerable to herbivory than intact tarbush.