The concentration levels of monoterpenes, including ${alpha}$- and ${eta}$-pinene, were measured in a pine forest in Florida, USA, over about one year. Based on this measurement data, the current study then investigated the factors affecting the environmental behavior of monoterpenes. Despite a moderately weak temperature variability in the study area, the temperature dependence of the concentration variations was still evident. The concentrations of the two pinenes were significantly affected by changes in the air temperature, as indicated by strong correlations with temperature. A close relation among the measured parameters was also found between the ${eta}$-pinene and ozone concentrations, which is also in line with previous findings from other studies. In addition, it was interesting to note that the ${eta}$/${alpha}$ pinene concentration ratio exhibited a strong inverse correlation to temperature, with the seasonal mean ranging from 0.51(summer) to 0.93(winter). Accordingly, the current results indicate that, in a forest environment, the major terpene species concentrations are affected by both meteorological conditions and chemical reactions.