1. Resilient and functional landscapes are essential for climate change adaptation. Thermodynamic theory has been applied increasingly to ecological studies to understand ecosystem resilience and integrity. Resilient ecosystems have complex structure and greater levels of biomass and functional diversity, which act to enhance the degradation of solar energy. Forests that exhibit these characteristics express thermodynamic efficiency through a greater capacitance effect that promotes cooler surface temperatures under extreme weather conditions.
2. With forest disturbance, complex structures and functional linkages are simplified, reducing the capacity of the system to degrade energy. Such changes can lead to dysfunctional ecosystem states, impaired provision of ecosystem services and a weakened resilience.
3. This study has applied indicators based on thermodynamic theory to a chronosequence of forest ecosystems in the UK, Germany and Ukraine. Surface temperatures were measured to test thermodynamic theories relating to energy degradation and temperature moderation. Grime’s CSR model was applied to plant data to compare functional complexity in vegetation between stands.
4. Old-growth woodlands are shown to attenuate surface temperature more effectively than native species plantations. Consistently lower temperatures were observed in European old-growth forests with high proportions of biomass when compared to managed stands of similar species composition, suggesting a greater efficiency of energy degradation in complex forest ecosystems, particularly at higher temperatures.
5. Analysis of plant species data using Grime’s CSR model indicated that old-growth forests ordinate towards competitive and stress-tolerant communities in contrast to intensively managed forests, which had a greater proportion of generalist and ruderal species. High CSR functional scores were associated with moderated temperature extremes.
6. Synthesis and applications. Our results suggest an important thermodynamic basis for conservation in the context of climate change. Conservation practice and management policy, which is based on preserving ecosystem complexity and function, can aid in mitigating the effects of extreme temperatures, enhancing vital services such as climate regulation, primary production and water retention. Old-growth forests have a significant climate mitigation role alongside other recognised ecosystem services such as carbon sequestration.