Long-term burning interacts with herbivory to slow decomposition.

Area of Science:

• Ecology
• Forest Science
• Nutrient Cycling

Background:

• Fire frequency influences spatial variation in trophic interactions, potentially affecting nutrient cycling.
• Insect herbivory on oak trees can alter litter quality and decomposition rates.
• Understanding these interactions is crucial for predicting ecosystem responses to fire.

Purpose of the Study:

• To investigate herbivore-induced effects on oak litter quality and decomposition under varying fire frequencies.
• To determine if specific insect herbivores (lace bugs, aphids) differentially impact oak decomposition.
• To assess how fire frequency modulates these herbivore-litter-decomposition dynamics.

Main Methods:

• Long-term manipulation of fire frequency in central Minnesota, USA.
• Targeted exclusion experiments to isolate herbivore effects on bur oak (Quercus macrocarpa).
• Analysis of litter chemistry (lignin) and subsequent decomposition rates.

Main Results:

• Exclusion of lace bugs (Corythuca arcuata) resulted in lower litter lignin and accelerated decomposition.
• Aphid (Hoplochaithropsus quercicola) exclusion did not affect litter chemistry or decomposition.
• Lace bug herbivory, more common in burned areas, decelerated decomposition, while aphid herbivory was more prevalent in unburned areas.

Conclusions:

• Frequent fires promote oak-lace bug interactions that decelerate litter decomposition.
• This herbivore-mediated effect amplifies fire's impact on slowing nitrogen cycling.
• Fire management strategies should consider indirect effects on trophic interactions and nutrient dynamics.