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 (Tmax) and minimum (Tmin) 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
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