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Citation. Strengbom, J.; Reich, P.B. 2006. Elevated [CO2] and increased N supply reduce leaf disease and related photosynthetic impacts on Solidago rigida. OECOLOGIA 149:519-525.
Abstract. To evaluate whether leaf spot disease and related effects on photosynthesis
are influenced by increased nitrogen (N) input and elevated atmospheric CO2
concentration ([CO2]), we examined disease incidence and photosynthetic
rate of Solidago rigida grown in monoculture under ambient or elevated
(560 μmol mol−1) [CO2] and ambient or elevated (+4 g N m−2 year−1) N
conditions in a field experiment in Minnesota, USA. Disease incidence was
lower in plots with either elevated [CO2] or enriched N (−57 and −37%,
respectively) than in plots with ambient conditions. Elevated [CO2] had no
significant effect on total plant biomass, or on photosynthetic rate, but
reduced tissue%N by 13%. In contrast, N fertilization increased both
biomass and total plant N by 70%, and as a consequence tissue%N was
unaffected and photosynthetic rate was lower on N fertilized plants than on
unfertilized plants. Regardless of treatment, photosynthetic rate was reduced
on leaves with disease symptoms. On average across all treatments,
asymptomatic leaf tissue on diseased leaves had 53% lower photosynthetic
rate than non-diseased leaves, indicating that the negative effect from the
disease extended beyond the visual lesion area. Our results show that, in this
instance, indirect effects from elevated [CO2], i.e., lower disease incidence,
had a stronger effect on realized photosynthetic rate than the direct effect of
higher [CO2].
Key Words. Carbon dioxide concentration - Global change - Nitrogen deposition - Photosynthesis - Plant pathogens