AI Generated
The study published in Forest Ecology and Management, titled ‘A perfect storm: Weather variability, mast failure, and the 1968 gray squirrel irruption in the eastern US’, investigate the possible causes, scientists examined oak seed production in the Asheville region of North Carolina, an area associated with the 1968 squirrel irruption. Their analysis covered 12 years, from 1962 to 1973, and included five oak species.
The effects varied according to the type of oak and the stage of development, meaning that a single weather pattern did not affect every tree in the same way. They compared annual acorn production with temperature and rainfall during the growing season, looking for weather patterns that might help explain why some years produced plentiful crops while others did not. The findings pointed towards a complicated relationship between weather and tree reproduction. Warmer spring and summer conditions were associated with reduced acorn production in several of the species examined. The scientists also examined whether the unusual weather associated with the North Carolina records could be detected across the wider northeastern United States. This helped establish whether the conditions affecting local oak production were part of a broader regional pattern rather than something confined to a small area. The relationship was not as simple as saying that one cold summer caused millions of animals to migrate. Tree reproduction responds to conditions over different stages of development, and the effects of weather can carry over from one growing season to another. The study also found evidence that a large crop in one year could be followed by a smaller crop in the next, supporting the idea that trees may need time to replenish resources used during heavy seed production.