Indirect effects of biotic damage on photosynthesis in a forest understory.
Hamilton, Jason*,1, Aldea, Mihai2, Resti, Joseph1, Zangerl, Arthur2, Berenbaum, May2, DeLucia, Evan2, 1 Ithaca College, Ithaca, NY, email@example.com University of Illinois, Urbana, IL
ABSTRACT- Arthropods, pathogenic bacteria, and viruses are important causes of damage to photosynthetic tissues in natural ecosystems. Calculating losses in leaf function and plant production based on leaf area removed by herbivores or infected by pathogens can greatly underestimate the actual reduction because of the indirect effects to tissues not directly injured. We quantified the indirect effects of naturally-occurring biotic damage on the photosynthetic efficiency of understory temperate hardwoods at the FACTS-1 research site (North Carolina, USA), using chlorophyll fluorescence and thermal imaging. Different damage classes( e.g. fungal, galls and chewing) produced different effects in the photosynthesis of tissue adjacent to the damage, suggesting different mechanisms of damage propagation. Halos of reduced function produced by fungal infections and galls propagated more than 2.5 times further from the visible damage, and photosynthesis was about 40% more depressed compared to chewing damage. Chlorophyll fluorescence quenching analysis revealed correlations between depressions of PSII and increases in NPQ within the areas indirectly affected by damage. However, the temperature of fungal halos was higher than the remaining leaf area, while gall halos were cooler, suggesting different mechanisms of propagation.
Key words: chlorophyll fluorescence imaging, thermal imaging, herbivory, photosynthesis
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