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Our objective was to assess the effect of changes in rainfall amount and distribution on CO 2 emissions and dissolved organic C (DOC) leaching. We manipulated soil moisture, using a roof constructed below the canopy of a 65‐yr‐old Norway spruce plantation Picea abies (L.) Karst. at Solling, Germany. We simulated two scenarios: a prolonged summer drought of 172 d followed by a rewetting period of 19 d and a shorter summer drought of 108 d followed by a rewetting period of 33 d. Soil CO 2 emission, DOC, soil matric potential, and soil temperature were monitored in situ for 2 yr. On an annual basis no significant influence of the droughts on DOC leaching rates below the rhizosphere was observed. Although not significantly, the droughts tended to reduce soil respiration. Rewetting increased CO 2 emissions in the first 30 d by 48% ( P < 0.08) in 1993 and 144% ( P < 0.01) in 1994. The CO 2 flush during rewetting was highest at high soil temperatures and strongly affected the annual soil respiration rate. The annual emission rate from the drought plot was not affected by the drought and rewetting treatments in 1993 (2981 kg C ha −1 yr −1 ), but increased by 51% ( P < 0.05) to 4813 kg C ha −1 yr −1 in 1994. Our results suggest that reduction of rainfall or changes in rainfall distribution due to climate change will affect soil CO 2 emissions and possibly C storage in temperate forest ecosystems.
Borken et al. (Mon,) studied this question.