Relationships between creosotebush productivity and associated foliage arthropod assemblages

Title	Relationships between creosotebush productivity and associated foliage arthropod assemblages
Publication Type	Thesis
Year of Publication	1988
Authors	Lightfoot DC
Number of Pages	159
Date Published	1988
University	New Mexico State University
City	Las Cruces, New Mexico
Thesis Type	Ph.D. Dissertationpp
Accession Number	JRN00083
Call Number	00176
Keywords	arthropod, foliage, dissertation, dissertations, Larrea, arthropods, Larrea, productivity, model, Larrea arthropods, nutrient amendment, nitrogen, nutrient amendment, water, rainfall simulation, theses, thesis, water amendment
Abstract	I conducted field experiments to examine relationships between creosotebush (Larrea tridentata) foliage production and associated foliage arthropods. Chapter One presents the results of an experiment designed to assess the effects of increased nitrogen and water on creosotebush foliage arthropods. Nitrogen fertilizer and irrigation treatments were applied to creosotebush shrubs. Water with nitrogen, and nitrogen alone, increased foliage production, foliar nitrogen contents, and numbers of foliage arthropods. Water alone had less effect on foliage production, and no effect on foliar nitrogen or numbers of arthropods. Sap-sucking insects were the most abundant arthropods responding to increased foliage production and foliar nitrogen contents. The experiment presented in Chapter Two was designed to determine if phytophagous insects on creosotebush increase rates of plant to soil nitrogen flux from nutrient-rich shrubs. Foliage arthropod populations, and nitrogen in canopy throughfall and stemflow, were measured to assess nitrogen flux rates relative to arthropod densities on fertilized and unfertilized shrubs. Foliage arthropod densities and biomasses, and amounts of nitrogen in throughfall, were greater from fertilized shrubs. Nitrogen excreted by foliage arthropods accounted for about 20% of the total nitrogen flux from unfertilized shrubs. I propose a model predicting foliage arthropods to enhance nitrogen availability to creosotebush shrubs. In Chapter Three, I tested the hypothesis that creosotebush shrubs growing in nutrient-rich micro-sites support more insects than shrubs growing in less productive sites. Shrubs from nutrient-rich sites had greater branch growth, flower production, and foliar nitrogen, than shrubs from less productive sites. Shrubs from nutrient-rich sites also supported greater densities of foliage arthropods. Shrub characteristics indicative of productivity covaried positively with foliage arthropod densities, and foliar resin concentrations covaried negatively with arthropod guilds. These findings are inconsistent with the theory that phytophagous insects are more successful on stressed host plants.