Print PagePlants that show masting behavior, or synchronous and intermittent reproduction, are hypothesized to accumulate resources in years of low reproductive output, which are later allocated to reproduction in ‘mast’ years. This ‘stored resource hypothesis’ predicts that if individuals have their reproductive investment artificially reduced, then their resource accumulation will be relatively high. It follows that if individuals accumulate more resources, then reproductive output in the following year will be enhanced. We tested this prediction with data on acorn production by 179 individuals of two oak species (Quercus macrocarpa and Q. ellipsoidalis), collected over 17 years at Cedar Creek Natural History Area in Minnesota. The trees occurred in six sites throughout the reserve that were subject to controlled burns during early flower development at different frequencies. One of these species (Q. macrocarpa) exhibits considerable annual variation in acorn production while the other does not, and thus we predicted that fire, by reducing acorn production, would significantly influence subsequent productivity by Q. macrocarpa but not Q. ellipsoidalis.
Results/Conclusions
There were no systematic differences in acorn production between trees subjected to different frequencies of fire, with the exception of the low frequency site (0.06 fires/year), where acorn production by Q. ellipsoidalis was significantly less than at other sites. Fires significantly reduced acorn crops in both Q. macrocarpa and Q. ellipsoidalis relative to years without a fire (p=0.015 and p=0.045, respectively). Acorn production by Q. macrocarpa in years following a burn was significantly increased, even if the focal year was also a burn year (p=0.0003 and p=0.0035, respectively); there was no significant lag effect on acorn production in Q. ellipsoidalis. These results were in line with our predictions and support the hypothesis that stored resources are key to intermittent reproduction.
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