| 06 Jan 2026
Scale-Dependent Transition in Soil Moisture Memory and Its Environmental Controls in Complex Mountain Terrain
Abstract. Soil moisture memory (SMM) defines the antecedent wetness states that modulate catchment responses to meteorological triggers, serving as a critical determinant of background hydraulic susceptibility. However, its multi-scale characteristics and environmental drivers remain poorly understood in complex terrain. This study characterizes SMM dynamics across daily-to-interannual scales using daily data (2003–2022) from three hazard-prone watersheds in southwestern China (Dali River, Anning River, and Jiangjia Ravine). By integrating Power Spectrum Analysis, Detrended Fluctuation Analysis (DFA-2), and a spatial attribution modeling framework, we identify a distinct scale-dependent transition in SMM persistence and its controls. Results revealed that while memory intensity generally weakened with scale, humid catchments exhibited a robust "inherent persistence" regime extending to multi-year scales. Crucially, feature importance analysis uncovered a structural transition at approximately the 5-year scale: atmospheric variables and vegetation dominated short-term variability, whereas soil properties and topography governed the system's long-term capacity to integrate low-frequency signals. Mechanistically, this marks a shift from event-driven hydraulic responses to background storage trends regulated by deep soil buffering. These findings provide a basis for distinguishing event-scale hydraulic preconditioning from long-term background susceptibility, offering a conceptual framework for incorporating operational persistence horizons into hierarchical hazard assessment strategies.
This paper investigates soil moisture memory (SMM) across multiple temporal scales in three catchments located in complex mountain terrain in southwestern China. Power spectral analysis (PSA) and DFA-2 are used to derive SMM metrics, which are then related to static and dynamic environmental variables using a Boruta Random Forest Algorithm. The stated aims are to: (1) identify thresholds for significant SMM transitions across temporal scales; (2) explain inter-catchment differences in SMM; and (3) develop a conceptual framework linking SMM to hazard preconditioning mechanisms.
My overall opinion is that this paper should be rejected for publication. Presented below are the reasons for my choice.
Scope, Motivation, and Contribution
The motivation for selecting these specific catchments and this regional setting is not sufficiently justified. It remains unclear why complex mountain terrain in southwestern China was chosen over other environments, or how the findings extend beyond the study area. The broader contribution to soil science and hydrology is therefore ambiguous.
The manuscript overstates its scope in places. For example, L54–56 claims a “comprehensive, multiscale characterization” of SMM, which is difficult to support given the analysis of only three catchments within a single climatic regime. This claim should be tempered or the scope clarified.
While the authors suggest relevance to hazard prediction in mountainous regions, this motivation is not consistently developed. Despite references to hazard susceptibility, the analysis focuses on a single debris-flow event in one catchment, which is insufficient to support the third stated research aim. As currently presented, the study does not robustly demonstrate how the proposed SMM metrics advance hazard prediction.
The paper would benefit from clearer positioning within the existing SMM literature. A more thorough review of prior work on SMM across temporal scales is needed to contextualize the novelty of the study (e.g., Rahmati et al., 2024, Reviews of Geophysics, Table 1).
Language, Terminology, and Clarity
The manuscript frequently relies on dense, jargon-heavy language that obscures meaning. Many sections are difficult to follow due to the use of neologistic or uncommon terms that are insufficiently explained or referenced.
For example, the discussion repeatedly introduces concepts such as “Sink to Structure,” “Dynamic Sink,” and “Static Structural Modifier” without clear definitions or grounding in prior literature. This overuse of unexplained terminology makes the discussion hard to interpret and gives the impression that complex physical processes are being compressed rather than critically examined.
Similarly, statements such as “no persistence,” “stronger influence of soil properties,” or “conditioning the baseline hydrological state” require clearer physical interpretation and explicit linkage to results.
Abstract and Introduction
Several abstract statements are vague or ambiguous:
The introduction would benefit from a clearer articulation of why SMM in complex terrain is important, particularly in relation to hazard prediction, and why southwestern China is an appropriate study region. Quantitative context and clearer linkage to hazards would strengthen the motivation.
Methods and Reproducibility
The methods section lacks sufficient explanation to ensure reproducibility. Many critical definitions and justifications are deferred to the appendices, which is not standard practice.
Across PSA, DFA-2, and Boruta analysis, the manuscript does not adequately explain:
Key terms such as “persistence horizons,” “reliable memory window,” and “significant memory” are introduced without explanation. For example:
Several specific methodological statements require clarification:
β and α are suggested to be the chosen memory metrics from the PSA and DFA-2 analysis but their physical meaning is never discussed, only vaguely as ‘strength of SMM’. Additionally, the relationship between PSA-derived β and DFA-derived α is unclear. Why are both used, and how do they complement each other?
The physical meaning of SMM itself is never clearly described (e.g., how long a soil moisture anomaly persists following a rainfall event).
Cryptic or vague sentences are also common further impairing interpretability. E.g.:
There are many cases where the same notation is used for different variables such as β for the PSA memory metric and slope aspect or τ for the decay timescale and characteristic response time.
Figures and Presentation of Results
The figures are difficult to interpret and do not enhance the results and discussion interpretability.
Overall, results are often reported numerically without adequate physical interpretation. Differences across months, seasons, and basins are described, but their implications for soil moisture dynamics or hazard relevance are not clearly articulated.
Results and Discussion
The discussion does not sufficiently situate the findings within the broader SMM literature. Recent syntheses (e.g., Rahmati et al., 2024) identify multiple controlling factors on SMM that should be explicitly compared with the results presented here.
Interpretation of results is frequently weak or unsupported. For example:
It is recommended the authors include at the end of every sub-section in results a summary paragraph written for a general audience with the key findings and implications/interpretations; otherwise it is very hard to follow the results.
Section 4.2 focuses on a single event in one catchment, raising concerns about selective emphasis. Claims regarding early-warning system applicability are therefore not substantiated, particularly given the lack of validation against hazard inventories. The use of basin-averaged soil moisture also contradicts earlier emphasis on slope-scale control of debris flows. Even if the proposed approach attempts to conceptualise these processes, it is unclear what the predictive power is for forecasting landslides and how it can be used in the region, and most importantly elsewhere.
Overall Assessment
While the research questions are potentially interesting, the manuscript suffers from insufficient methodological clarity, overuse of jargon, weak physical interpretation of results, and limited engagement with the broader SMM literature. Conclusions regarding hazard relevance and early-warning systems are not adequately supported by the analyses presented. Substantial revision would be required to clarify methods, strengthen interpretation, and better articulate the study’s contribution. Overall, my conclusion is to reject the paper.
Line specific comments: