PARENT SESSION
Oral Session #87: Ecosystem Ecology.
Presiding: B. Currie
Thursday, August 8. 1:00 PM to 3:45 PM. Graham Meeting Room, TCC.
Insect herbivory alters soil microclimate in a semi-arid woodland: nutrient cycling implications.
Classen, Aimee*,1,3, Hart, Stephen2,3, Whitham, Thomas1,3, Cobb, Neil1,3, Koch, George1,3, 1 Department of Biological Sciences, Flagstaff, AZ3 Merriam-Powell Center for Environmental Research, Flagstaff, AZ2 School Of Forestry, Flagstaff, AZ
ABSTRACT- Herbivory effects on nutrient cycling have been examined primarily in terms of litter quality and quantity, but herbivory can also alter abiotic conditions that regulate decomposition and nutrient dynamics. Two distinct insect herbivores chronically infest pinyon pines (Pinus edulis) in northern Arizona. The stem-boring moth (Dioryctria albovittella) bores into terminal shoots of adult pinyons producing a dense shrub-like canopy architecture. The scale insect (Matsucoccus acalyptus) infests juvenile trees causing premature abscission of all but the current-year needle cohort, resulting in an open canopy architecture. We used a long-term herbivore removal experiment (16-18 years) to determine how these herbivore-caused changes in architecture alter soil microclimate. Chronic scale herbivory significantly reduced whole-tree leaf area and leaf area index by up to 75%, increasing soil insolation and mean maximum soil temperature by up to 5°C. Both scale and moth herbivory significantly decreased canopy interception of monsoonal precipitation, by 75% for adult (moth) trees and 34% for juvenile (scale) trees. Volumetric soil water content increased by up to 40% in juvenile trees with scale herbivory compared to scale-free trees. Together these experimental data demonstrate that insect herbivory alters soil microclimate. We propose that these indirect effects of herbivory interact with herbivory-caused changes in litter quality to alter litter decomposition and soil nutrient dynamics.
KEY WORDS: Herbivory, Ecosystem, Soil microclimate, Nutrient cycling