Analysis of canopy temperature depression between tropical rainforest and rubber plantation in Southwest China

Temperature change is an important environmental variable for global change sciences since it largely affects the physiology of plants in forest ecosystems. Canopy temperature depression (CTD) - the result of the deviation of the air temperature (Ta) from the plant canopy surface temperature (Tc) - varies depending on the meteorological and environmental conditions of the forests. Here, we evaluated the differences in CTD between a rubber plantation (RP) and a tropical rainforest (TR) in Xishuangbanna, southwestern China across the various time series of the period of 2011 to 2015. The mean maximum CTD values at the TR site and the RP site were 2.4°C and 0.6°C at diurnal level, 1.3°C and -0.5°C at monthly level, 0.6°C and -0.8°C at seasonal level and 5.6°C and 0.2°C at yearly time series level, respectively, while they were only significant (p < 0.01) in the diurnal time series. There was a significant (p < 0.01) negative linear relationship between CTD and global radiation (Q) in both sites at diurnal level and a significant (p < 0.05) negative linear relationship in the RP site at monthly time series level. A significant (p < 0.05) positive linear relationship between CTD and precipitation (P) at the RP site was found at diurnal level, as well as a significant (p < 0.01) positive linear relationship in the TR site at monthly time series level. The variation of CTD was critical for these two sites and largely depended on the amount of global radiation and the precipitation, while it will mainly affect the physiological variables. This study may prove useful for assessing the physiological response in terms of high temperature and drought conditions to regional and global change.