The Phenological Effect of Climate Change on the Northern Highbush Blueberry
The agricultural industry is harshly impacted by global warming because of its dependence on crop’s responses to changing weather patterns. Phenology, the timing of biological events, can be used to study the effect of climate change on plants. Phenological shifts caused by climate change can occur because flowering and fruiting times are often temperature-dependent events. Herbarium records, dried plant samples catalogued by collection date, are useful when studying phenological changes for particular species, as many specimens are collected during flowering and/or fruiting periods. The northern highbush blueberry (Vaccinium corymbosum) is grown throughout the United States and has individual herbarium records dating back 170 years. Based on the phenological trends of other spring-flowering species, I hypothesized that V. corymbosum would flower and fruit earlier in response to rising temperatures. Although it has not yet been explored for this species, it is known that Vaccinium corymbosum requires a chilling period, therefore I also included average winter temperatures in my study along with climatic factors relating to moisture prevalence. PRISM database was used to obtain climate data for each specimen collection site. A minimum AiC model determined that Vaccinium corymbosum is flowering earlier due to increasing average temperatures in April and May and fruiting earlier in response to warming temperatures during May and the month of specimen collection. Moisture prevalence was found to delay flowering and fruiting times, but those effects did not offset the overwhelming trend of premature phenological events caused by rising spring temperatures. Based on these results, Vaccinium corymbosum is likely flowering 12 days earlier and fruiting 19 days earlier today than it did 170 years ago.