Comparison of infrared canopy temperature in a rubber plantation and tropical rain forest

Abstract

Canopy temperature is a result of the canopy energy balance and is driven by climate conditions, plant architecture, and plant-controlled transpiration. Here, we evaluated canopy temperature in a rubber plantation (RP) and tropical rainforest (TR) in Xishuangbanna, southwestern China. An infrared temperature sensor was installed at each site to measure canopy temperature. In the dry season, the maximum differences (T - T) between canopy temperature (T) and air temperature (T) in the RP and TR were 2.6 and 0.1 K, respectively. In the rainy season, the maximum (T - T) values in the RP and TR were 1.0 and -1.1 K, respectively. There were consistent differences between the two forests, with the RP having higher (T - T) than the TR throughout the entire year. Infrared measurements of T can be used to calculate canopy stomatal conductance in both forests. The difference in (T - T) at three g levels with increasing direct radiation in the RP was larger than in the TR, indicating that change in (T - T) in the RP was relatively sensitive to the degree of stomatal closure.

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

“…In terms of the yearly time series, the same results were found, with the exception of the period between June and November of 2014. Song et al (2017) found in their one-year data analysis of the canopy temperature difference between Tc and Ta at these two sites that the differences at the RP site were higher than those of the TR site throughout the whole year. When we analysed the five-year data related to the canopy temperature depression between Tc and Ta, the same results were observed.…”

“…At the vegetation level, canopy height and structure affected the Tc (Greco et al 2012). Song et al (2017) found that a normalised condition (Tc-Ta) was very sensitive to all simulated meteorological conditions that were linearly, directly proportional to solar radiation and inversely proportional with the vapor pressure deficit (VPD) and also non-linearly, inversely proportional to Ta and wind speed (Ws). Canopy height had a large influence on (Tc-Ta), in that it decreased with increasing height and increased in very low vegetation under drought stress (Greco et al 2012).…”

“…The two sites (TR and RP) are located about 10 km apart and share similar climatic conditions. According to climatic observations made at a meteorological station over five decades , the mean annual temperature was 21.8 °C, while the mean annual rainfall was 1511 mm, with over 85% of the annual rainfall occurring in the rainy season; the mean monthly rainfall during the dry season is less than 40 mm (Song et al 2017).…”

“…2 °C. In fact, the instruments used here were similar to those used in the study by Song et al (2017), who found that the radiation detected using an infrared radiometer includes two components: the radiation directly emitted by the target surface, and the reflected background radiation (often neglected). The magnitude of the two components in the radiation detected by the radiometer was estimated using the emissivity and reflectivity of the target surface.…”

Estimating Crop Transpiration of Soybean under Different Irrigation Treatments Using Thermal Infrared Remote Sensing Imagery

“…In fact, according to many other studies [46][47][48][49][50][51][52][53][54], we can conclude that heterogeneity of canopy temperature mainly results from physical and biological interactions, which are affected by climatic conditions (such as wind, temperature, vapor-pressure deficit, relative humidity, long wave radiation, and the angle of radiation incident on the leaf surface), environmental conditions (soil temperature at 2 cm depth, soil moisture, adjacent objects, and solar height), canopy structure complexity (leaf inclination distribution frequency, size, shape, and position), canopy parameters (canopy albedo, emissivity, and stomatal resistance) and ecosystem functions (evapotranspiration and photosynthesis). Among these studies, the result of Smith and Carter [47] showed that the temperatures of needle-leaf were closer to air temperature than that of broad leaves, and needle leaves usually remained within 4-8 K of air temperature, whereas Jones [48] reported that sunlit broadleaves might be 10-15 K higher than air temperatures.…”