The continuum of plant responses to herbivory: The influence of plant association, nutrient availability, and timing
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Authors: J. Maschinski, and T. G. Whitham
Date: 1989
Journal: The American Naturalist
Volume: 134
Number: 1
Pages: 1-19
Summary of Methods: The single and interactive effects of plant association, nutrient availability, and timing of herbivory on reproductive fitness of Ipomopsis arizonica near Sunset Crater National Monument, Arizona were examined. To address how plant association interacted with herbivory, triplets (grouping of three rosettes) located near ponderosa pine, bunchgrass, or open areas were identified and measured. One rosette had previously been grazed (1-8 months earlier than clipping), one was clipped early in the growing season to base, and the other remained ungrazed for the control. Four fertilizer and water treatments (only fertilizer, only water, water and fertilizer and no water or fertilizer) were also applied. Total fruit set was counted from late-August to mid-September, seed weight, and number of seeds per fruit from three mature fruits were counted and weighed for all treatments.
Article Summary / Main Points: The number of seeds per fruit and seed weight did not vary in response to plant association, nutrient treatment, or herbivory (natural or simulated). The association of I. arizonica with other plants decreased fruit set, and fertilization resulted in more fruits than water-treated or control plants. Water treatment alone did not increase fruit in two of the three years. Grazed plants produced as many fruits as ungrazed plants while clipped plant response varied with time of clipping. Early season clipping had no effect on fruit production but clipping later in the growing season decreased fruit production. For clipped plants production was decreased when nutrients were absent or when neighbors were present.
Vegetation Types: Ponderosa Pine Woodlands
MLRA Ecoregions: 35 Colorado Plateau 39 Arizona and New Mexico Mountains
Agrovoc Control Words: Grazing Rangelands Water stress
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: grazing response, analysis of covariance, water stress, nutrient levels, ipomopsis arizonica, compensatory growth
Annotation: The specific results from this study are applicable to rangelands with I. arizonica. The underlying principals of how individual plants respond to herbivory, timing of herbivory, interspecies completion and nutrients are applicable across all rangelands. It is imperative to remember that each species responds differently to these factors based on their physiological characteristics.
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