Phytophagous insects enhance nitrogen flux in a desert creosotebush community

TitlePhytophagous insects enhance nitrogen flux in a desert creosotebush community
Publication TypeJournal Article
Year of Publication1990
AuthorsLightfoot DC, Whitford WG
Date Published1990
Accession NumberJRN00126
Call Number00179
Keywordsarthropod, also SEE <INSECT>, article, articles, creosotebush, insect, phytophagous, journal, journals, nitrogen amendment, nitrogen cycling, Larrea, nitrogen flux, phytophagous insects, rainfall simulation, water amendment

We tested the hypothesis that herbivorous insects on desert shrubs contribute to short-term nitrogen cycling, and increase rates of nitrogen flux from nutrient rich plants. Creosotebush (Larrea tridentata) shrubs were treated with different combinations of fertilizer and water augmentations, resulting in different levels of foliage production and foliar nitrogen contents. Foliage arthropod populations, and nitrogen in canopy dry throughfall, wet throughfall and stemflow were measured to assess nitrogen flux rates relative to arthropod abundances on manipulated and unmanipulated shrubs over a one-month period during peak productivity. Numbers and biomass of foliage arthropods were significantly higher on fertilized shrubs. Sap-sucking phytophagous insects accounted for the greatest numbers of foliage arthropods, but leaf-chewing phytophagous insects represented the greatest biomass of foliage arthropods. Measured amounts of bulk frass (from leaf-chewing insects) were not significantly different among the various treatments. Amounts of nitrogen from dry and wet throughfall and stemflow were significantly greater under fertilized shrubs due to fine frass input from sap-sucking insects. Increased numbers and biomass of phytophagous insects on fertilized shrubs increased canopy to soil nitrogen flux due to increased levels of herbivory and excrement. Nitrogen excreted by foliage arthropods accounted for about 20% of the total one month canopy to soil nitrogen flux, while leaf litter accounted fro about 80%.