Effects of Fire, Browsers and Gallers on New Jersey Tea (Ceanothus Herbaceous) Growth and Reproduction
Throop, Heather L., Fay, Philip A., The American Midland Naturalist
ABSTRACT.-Woody plant species in grassland ecosystems can be subjected to damage from fire and multiple herbivore species, but interactions between fire and galling (by Periploca ceanothiella, Lepidoptera: Cosmopterigidae), deer browsing (Odocoilius virginianus) and fire affected the growth and reproduction of the woody shrub Ceanothus herbaceous (Rhamnaceae) on a burned and an unburned site at Konza Prairie Research Natural Area in eastern Kansas. Fire was the major influence on C. herbaceous growth, causing plants to produce long unbranched vegetative ramets from protected belowground meristems, while unburned plants were heavily branched and bore shorter shoots and numerous inflorescences. Unburned plants experiences higher gall frequencies, more galls on their longest shoots, but similar deer browsing compared to burned plants. Ramets with herbivore damage had more branches and inflorescences than undamaged ramets, especially where both herbivores were present. Ceanothus herbaceous' flexible lfie history repsonses suggest tolerance of multiple forms of damage.
Fire and herbivory exert pervasive influences on the composition and productivity of many ecosystems, including the tallgrass prairies of North America. One major effect of fire is suppression of woody plants in favor of grasses and forbs (Bragg and Hulbert, 1976). Fire typically suppresses woody species by destroying aboveground biomass and meristems, which alters subsequent plant growth, architecture, reproductive capacity and competitive interactions (Glenn-Lewin et al., 1990; Yeaton and Bond, 1991; Matlack et aL, 1993). In addition, fire modifies abiotic parameters important to plant growth, including temperature, light and resource availability (Old, 1969; Hulbert, 1988; Niesenbaum, 1992; Turner et al., 1997). Herbivory has many of the same influences on woody plants as fire including biomass removal, meristem death and reduced growth, reproduction and competitive ability (Fay and Hartnett, 1991; Erasmus et al., 1992; Brown, 1994). The severity of herbivore impacts on plants depends on the timing, intensity and type of damage inflicted, and a plant's postdamage growth and physiological responses (Watson and Casper, 1984; Rosenthal and Kotanen, 1994; Fay et al., 1996). Herbivore impacts may be compounded when plants are damaged by several herbivore species (Willis et al., 1993).
Fire can strongly affect the extent to which herbivore damage actually occurs. For example, fire affects which herbivore species are present (Warren et al., 1987). Some herbivore species tend to be killed in fires because their phenologies or life histories render them unable to escape. Other species mainly experience indirect effects such as postfire changes in host plant quality and abundance (Stein et al., 1992) or abiotic conditions (Hulbert, 1988). These direct and indirect effects of fires can affect herbivore abundances (Warren et al., 1987) and within-plant herbivore distributions (Rosenthal and Kotanen, 1994). As a result, the net impact on woody plant life histories of a fire/herbivore damage regime can be difficult to predict.
New Jersey Tea (Ceanothus herbaceous: Rhamnaceae) is found primarily on prairies and open woodlands throughout the midwest and south, and locally in the eastern United States (Bartgis et al., 1997). It is an abundant shrub in Flint Hills tallgrass prairies (Gibson and Hulbert, 1987), where it persists despite regular damage from fire and herbivores. Fire damage typically occurs during spring prescribed burns, which are often conducted to reduce woody species populations. In addition, two herbivores commonly damage C. herbaceous; a stem-galling moth (Periploca ceanothiella, Lepidoptera: Cosmopterigidae) whose abundance is directly influenced by spring fires (PAF and D.C. Hartnett, pers. observ.), and a browsing mammal, white-tailed deer (Odocoileus virginianus). The abundance of C. herbaceous despite consistent pressure from fire and multiple herbivores suggests that this species possesses effective tolerance mechanisms. …