Author(s)

José O. Payero^1,2

¹Edisto Research and Education Center, Clemson University, Blackville, SC, USA.
²Department of Agricultural Sciences, Clemson University, Clemson, SC, USA.

There is considerable concern about the potential impact of climate change on agriculture, such as the accumulation of chilling hours needed to break the dormancy of many perennial plants, like fruit trees. Therefore, this study aimed to determine if there had been a significant change in air temperatures and chill hours, chill units, and chill portion accumulation in South Carolina over the last two decades. Two decades of daily maximum (T_max) and minimum (T_min) air temperature records were obtained from weather stations in thirty-one counties in South Carolina. Hourly temperature data, reconstructed from the daily data, were used to calculate the daily and annual chill hours, chill units, and chill portions accumulation using four different chill models for each location and year. The chill models included the T(t) < 7.2°C model, the 0°C < T(t) < 7.2°C model, the Utah model, and the Dynamic model. For each county, regression analyses were conducted to evaluate the historical trends. Despite year-to-year variability, the tendency was a statistically significant (α = 0.05) increase in air temperature, averaging 0.089°C per year for 20 out of 31 counties in South Carolina. The other 11 counties had no significant change in temperature. The average temperature increase in the 31 counties was 0.072°C per year. The temperature increase resulted in a decrease in annual chill accumulation during the fall to spring, averaging 17.7 chill hours, 8.6 chill hours, 17.0 chill units, and 0.40 chill portions per year calculated with the T(t) < 7.2°C, 0°C < T(t) < 7.2°C, Utah, and Dynamic models, respectively. However, whether this decrease in chill values was statistically significant or not depended on the chill model used. This study did not investigate the cause of the observed historical trends in temperature and chill accumulation. Still, if the trends continue, they could significantly impact the future of the temperate fruit tree industry in the state.

Chill Hours, Chill Units, Chill Portions, Temperature, Fruit Trees, Climate Change, Dormancy

Payero, J. (2024) Temperature Trends and Accumulation of Chill Hours, Chill Units, and Chill Portions in South Carolina. Atmospheric and Climate Sciences, 14, 173-190. doi: 10.4236/acs.2024.142011.