The tropical rainforest, hot and humid, nurtures countless forms of life and is home to the greatest biodiversity on Earth. In 1993, Xishuangbanna was designated a UNESCO Biosphere Reserve, preserving China's most complete tropical rainforest ecosystems.

Led by Professor LIN Hua from the Xishuangbanna Tropical Botanical Garden of the Chinese Academy of Sciences, a research team ventures deep into the forests at the border of China, Myanmar, and Laos. Their task seems simple—measuring leaf temperature—but it carries profound implications for how plants respond to climate change.

When Thermodynamics Meets Ecology

Thermal ecology explores the relationships between heat and other forms of energy, as well as how these relationships influence the states of organic life and ecosystems, offering a new lens to understand the health and dynamics of ecosystems. Heat is the lowest-grade form of energy—the more heat produced, the lower the energy utilization efficiency.

Just like an overheated computer slows down or crashes, ecosystems too can "run a fever". Healthy forests make efficient use of solar energy, dissipate heat through transpiration and canopy structure to lower surface temperatures, and channel more energy into maintaining and building the system.

The "Three-Temperature Method"

Temperature is not just a number but a reflection of the overall state of a system. As ecosystems grow, recover, or degrade, their surface temperatures change. Temperatures vary across vegetation types, and successional stages.

To capture this, LIN's team developed the "Three-Temperature Method": the temperature of a normal leaf, the temperature of a non-transpiring leaf, and the temperature of the reference (air or artificial leaf).

By comparing these three values, the team can quantify a plant's transpirational cooling and physical thermal effect—allowing them to assess whether a forest is degrading or recovering. Tools such as thermocouples or thermal cameras make these measurements possible in the field.

Why Does It Matter?

Thermal images reveal temperature differences among plants in real time. The team will measure transpirational cooling, collect leaves and analyze leaf traits in the lab, e.g., leaf size and water content, helping uncover the drivers behind the differences.

These insights not only inform forest restoration and species selection, but also guide vegetation planning and even local climate improvement.

Prof. LIN's team is uncovering the secrets of climate and ecology—leaf temperature—pushing science forward into our shared future.