| 20 Nov 2025
Global parameter sensitivity analysis of modelling water, energy and carbon dynamics in a temperate swamp
Abstract. Forested peatlands cover a land area of 7 x 105 km2 and store ~77 Pg C in Canada. However, the carbon (C) cycling of forested peatlands, particularly swamps, has been understudied. Few modelling studies have been done on temperate swamp C cycling partly because of the scarcity of field measurements in this ecosystem. These gaps create uncertainties in modelling the C dynamics of temperate swamps and consequently limit our understanding of this ecosystem. To improve our understanding of the processes, interactions and feedbacks that mediate temperate swamp C cycling, we simulated the long-term (40 years) plant processes, energy, water and C fluxes of Beverly Swamp, a well-preserved swamp in Southern Ontario using a process-based model (CoupModel). CoupModel v6 was systematically calibrated for Beverly Swamp using the Generalized Likelihood Uncertainty Estimate (GLUE) method and validated with field measurements. The GLUE approach and its multicriteria constraints reduced the uncertainties associated with the modelling process and reasonably improved some of the simulation outcomes when compared to the initial single run and prior uniform distribution. Global sensitivity analysis of the parameters identified the important parameters that greatly influence temperate swamp C flux simulations and the interconnections that exist between simulated variables and parameters. Plant-related processes and hydrological variables exerted the strongest control on soil respiration simulation. However, these dynamics may be altered as climate continues to warm in coming decades. Results from this study provide valuable knowledge for predicting the fate of swamp C cycle in the region under a changing climate.
The manuscript addresses a relevant topic and applies established modelling and uncertainty analysis approaches; however, several substantive issues need to be addressed before it can be considered for publication. A moderate revision is recommended.
The scientific contribution remains somewhat limited. The study mainly applies existing methods (CoupModel + GLUE + GSA) to a swamp system, but the advancement beyond previous studies is not sufficiently articulated. The authors should clearly define the key scientific questions and explicitly state what new insights are gained at the process or system level.
Section 5.1 should be moved to the Discussion section. Its current content focuses on interpretation and mechanism explanation rather than presenting new results. Integrating it into the Discussion would improve the logical coherence of the manuscript.
The data basis raises concerns regarding robustness. Key calibration and validation datasets are sparse and temporally inconsistent (e.g., combining 1998–2000 and 2022–2023 observations). The authors should better justify this strategy and discuss its implications for model reliability and uncertainty.
The treatment of lateral water flow using proxy data is a critical assumption. Although acknowledged, it is not sufficiently quantified. A more rigorous uncertainty assessment or sensitivity discussion specific to this assumption is needed.
The Results section is overly descriptive, particularly in terms of parameter sensitivity rankings. The authors should better synthesize the findings, highlight dominant controls, and link them more explicitly to physical processes rather than listing parameter importance.
The Discussion is currently insufficient in depth. It should be strengthened by (i) systematic comparison with existing studies (especially bog and fen systems), (ii) clearer interpretation of process interactions, and (iii) explicit discussion of model limitations and applicability.
Model structural limitations need to be more explicitly addressed. The use of a one-dimensional model for a spatially heterogeneous swamp system may constrain interpretation, and this should be critically discussed.
The manuscript would benefit from improved integration between sections. Currently, the linkage between objectives, methods, results, and conclusions is somewhat loose. The authors should ensure that each objective is clearly addressed and revisited in the results and discussion.
Overall, the manuscript has a solid foundation, but requires deeper analysis, clearer positioning of its contribution, and improved discussion to meet publication standards.