Sensor evaluation for leaf temperature within a minimally invasive leaf cuvette

Leaf surface temperature is a key factor impacting plant physiological activity and reflects processes such as transpirational cooling and interactions between air temperature and radiation. In forests, precise monitoring of leaf temperature aids in assessing tree resilience to climate change and detecting water stress. Climate change has led to hot droughts in the last decade, which can drive species to their thermal limits, inducing leaf scorching. Nevertheless, long-term, minimally invasive monitoring remains a challenge. We evaluate commercial sensors regarding their suitability for measuring leaf temperature. This includes contact-based sensors, such as thermocouples and semiconductor sensors, as well as non-contact infrared sensors. A particular focus is the challenge of establishing a reliable contact between the sensor and the leaf surface, which is crucial for accurate and consistent readings. Their performance regarding response time, measurement accuracy, and reliability under different environmental conditions is assessed. These leaf temperature sensor types are compared for integration into measurement systems that require precise leaf temperature data, such as the ECOvette, a minimally invasive leaf cuvette. The ECOvette was developed to measure the gas exchange of a leaf under outdoor conditions; it also tracks environmental parameters like leaf temperature throughout the lifespan of a leaf. Our findings show that particularly semiconductor-based devices provide fast and stable temperature readings. These results contribute to improving long-term leaf monitoring in both natural and managed ecosystems, offering valuable insights for climate research. • Non-invasive sensors are essential for continuous and undisturbed leaf temperature monitoring. • Semiconductor sensors enable fast and stable leaf temperature measurements. • Sensor size and thermal contact affect accuracy in outdoor leaf monitoring. • Small sensors with good contact improve long-term field measurements. • Data support plant stress and climate studies in natural forest environments.