Thermodynamic Approach to Assessing Ecosystem Integrity of Gwangneung Old-Growth Forest Biosphere Reserve in Korea

Biodiversity and integrity are the key indicators representing ecosystem’s state. Much attention has been given to the former while less to the latter. This is because (1) the definition of integrity is ambiguous, (2) theoretical framework is lacking for quantitative assessment, and (3) observation data for quantification and validation are in paucity. The review of literature funnels down the definition of integrity to twofold perspectives: normative and thermodynamic. Accordingly, we define integrity as a state of ecosystem whose structure and function self-organize to an extent comparable to its reference state. Here, system’s self-organization can be expressed holistically based on non-equilibrium thermodynamics by quantifying the system’s thermodynamic entropy balance. We have tested this definition and the theoretical framework to assess the integrity of Gwangneung old-growth forest in Korea (GDK), which has been designated as one of the UNESCO’s Biosphere Reserves since 2010. Long-term observation (from 2005 to 2020) of energy, matter (water vapor and carbon dioxide) and information flows in and out of GDK were divided into the reference period (2006-2010) and the test period (2011-2020). These dataset emcompasses a wide range of environmental conditions and disturbances to examine ecosystem response and adaptability. GDK's self-organization was estimated in terms of entropy production (σ) and entropy transfer (J). Also, using information-theoretic approach, the behaviors of σ and J were analyzed in terms of the balance between informational emergence (flexibility) and self-organization (order, thus related to resilience). These results were compared and scrutinized by associating with the analyses of (1) linear cause and effect relationships between key variables representing ecosystem structure and function (e.g., energy capture, energy dissipation, biomass production, respiration, biodiversity) and (2) transfer entropy-based dynamic process network (of subsystems at various spatio-temporal scales, feedback types/loops and delay). Granting the necessity of further test and improvement, we argue that thermodynamic and information-theoretic frameworks are complementary and shed a light to development of more holistic and operational indicators for ecosystem integrity such as maximum complexity and antifragility.