Multi-method late-successional and old-growth (LSOG) forest mapping uncertainty for Maine's unorganized townships

This dataset quantifies the uncertainty in mapping late-successional and old-growth (LSOG) forest across the approximately 4.2 million hectares of Maine's unorganized townships, and tests whether LSOG is rapidly disappearing. Three to four independent, credible mapping methods are compared on a common 100 m grid: (M1) a reproduction of the Hagan et al. (2026) airborne-LiDAR canopy random forest, rebuilt from their public Zenodo deposit; (M2) a logistic model of the FIA field-structure LSOG class on Potapov (GEDI-calibrated) canopy height; (M3) a direct canopy-height threshold; and (M4) the FIA structural class imputed to every pixel via USFS TreeMap (2016, 2020, 2022). Materials behind the formal Ecosphere Comment on Hagan et al. (2026): a cross-validated accuracy assessment (AUC) of each mapping approach on the original authors' own training plots; an FIA design-based estimate of older forest with sampling-error confidence intervals (older forest about 3.9 percent [3.3 to 4.6] and rising, including on private commercial timberland); a threshold-sensitivity sweep and a 20-seed reproduction ensemble; an ownership-resolved breakdown; a hex-scale (8 km) summary of cross-method disagreement; and the Comment manuscript and Supporting Information. Version 1.5.1 (this version): revised after a three-perspective simulated peer review (remote sensing, forest biometrics, and an ecologist in the original author's voice; included). Refinements: the terrain/disturbance overlay now states it uses the airborne Hagan map (independent of the TreeMap-derived disturbance product) with slope as a first-order accessibility proxy; the four-axis classification thresholds are flagged as tunable with the dead-wood (snags-only, no coarse woody debris) and continuity (treatment-code, permissive) caveats, so 6.5 percent is an upper bound; the multidimensionality result is noted as conditional on a purposive training sample; and the broad-class breadth is reframed as an objective-dependent choice with continuity treated as a weighted axis rather than a disqualifier. Earlier: adds an overlay of the LSOG map with the satellite disturbance record and terrain over the Maine AOI (n = 3.8 million pixels). LSOG concentrates on steeper, less accessible ground (median slope 5.3 vs 3.0 degrees) and more disturbance-prone settings; the mapped-LSOG share rises from 12 percent on the gentlest terrain to 37 percent on the steepest and from 17 to 35 percent across the disturbance gradient. This reframes risk: much mapped LSOG persists where harvest is costly or impractical and where natural disturbance dominates, so a single flat loss rate overstates near-term harvest risk to the inaccessible majority. The CONUS harvest-probability model does not cover Maine's unorganized townships, so slope serves as the accessibility proxy. Earlier: adds the constructive endpoint, a repeatable multi-axis classification of true LSOG anchored in FIA. True LSOG must satisfy four axes (live structure, dead wood, compositional maturity, and temporal continuity), each a deterministic function of FIA records; the design-based area meeting all four is 6.5 percent [5.6, 7.4] of Maine forestland (between strict age-based old growth at 3.9 percent and broad canopy LSOG near 20 percent). The Comment shows which axis is limiting, an objective-to-threshold table, and the path from definition to map (LiDAR for live structure, the satellite disturbance record for continuity, plots or imputation for dead wood and composition), calibrated to FIA. Earlier: deepened the conceptual core around the question 'what is true LSOG?'. LSOG is framed as a multidimensional condition (live structure, dead wood, compositional maturity, temporal continuity); on the training plots a dominant stand-development gradient explains 59 percent of variance but dead wood forms a partially independent axis (r about 0.5), and canopy sensors are nearly blind to dead wood and to disturbance history, the last compromised in Maine by pervasive legacy skid trails even in canopy-classified LSOG. Adds a correlation/dimensionality figure, references (Franklin and Van Pelt 2004; Wirth et al. 2009), and moves the Maine-scale ensemble to the Supporting Information. Earlier: emphasized that a single-date classification is a snapshot that cannot credit future LSOG from ongoing conservation and natural ingrowth (the transitioning class, 15.8 percent of the area, becomes late-successional in 25 to 50 years per the original authors; reserved lands mature into LSOG), and added a brief synthesis of the complementary toolset (airborne LiDAR, spaceborne GEDI and canopy-height products, FIA design-based inventory, TreeMap imputation, and growth-and-yield models) that together can represent the forward trajectory a snapshot cannot. Earlier: added the threshold-independent ROC AUC (0.979) to the cutoff-sensitivity figure and variation metrics throughout; a figure of older forest over time under four definitions and thresholds; and a refined, robust New England multi-definition ensemble LSOG map summarized at the hexagon scale (built from the FIA condition imputed to each TreeMap pixel; structural class, stand age >= 120 yr, and large-tree basal area), with an uncertainty layer. The New England ensemble is presented hexagonally because TreeMap is an imputed product (finer resolution would overstate its precision) and is cross-consistent with the design-based state estimates. Across the region only 8.9 percent of forested area reaches high agreement and 24 percent is high-uncertainty. Earlier: incorporated a second simulated peer review (included). The prototype ensemble layer is now described as an unweighted agreement (membership) score rather than a calibrated probability; the threshold-sensitivity figure is clarified as computed on the labelled plots (training prevalence, not landscape area); FIA reserved status is framed as a conservative lower bound (formally reserved); and notes were added on the forest-type dependence of the structural threshold and on the Rhode Island age trend. Earlier: the Comment was expanded to 14 pages with new supporting evidence: an out-of-bag confusion matrix and a probability-threshold sensitivity figure; a multi-measure temporal panel (FIA stand age, FIA large-tree basal area, and the TreeMap-imputed LSOG classification over time); a New England regional-context section showing older forest stable to increasing in all six states by design-based FIA; a current-protection analysis (only ~12% of Maine older forest is reserved, almost all public; the resource is overwhelmingly private and unprotected); and a demonstrated prototype multi-method ensemble LSOG probability with a companion per-pixel uncertainty layer (archived as 100 m rasters), shown as hex and bivariate maps. Earlier: document layout finalized (captions placed above tables and below figures, tables kept from breaking across pages, white space reduced) and a new section of concrete recommendations for future research added. Earlier: the manuscript was stress-tested, with every quantity re-verified against the source data, and a single orphan reference (the rapid field protocol, Shamgochian et al. 2025) was cited in the text; the verification is documented in the included audit memo (Deep_review_Hagan_vs_Comment). Earlier in the 1.2.x line: authorship corrected to the sole author; the framing broadened (all maps and models are wrong, the question is whether they are useful) and the tone softened; the Comment now credits the original authors' Limitations section, future-work proposals, ingrowth caveat, and citation of the national FIA and GEDI LSOG literature, and adds an explicit treatment of remote-sensing noise and GEDI geolocation error (Shannon et al. 2024), with the design-based FIA estimate as the sole reference. The conclusion names three practices: benchmark against a design-based inventory (FIA), cross-compare against an independent product rather than rely on a single remote-sensing map, and report accuracy and uncertainty on every quantity. The proprietary Seven Islands comparison was removed. A document build error that had frozen the manuscript PDF at an earlier draft in versions 1.2.0 through 1.2.2 is fixed here, so this is the first version to contain the complete, current Comment and Supporting Information. Headline findings. Credible methods disagree by roughly 2.8 times on how much LSOG exists and on the location of most LSOG hectares, while agreeing closely on the rare, well-defined old-growth core. Top-priority protected sets selected by different maps overlap on only 16 to 30 percent of the ground. The design-based FIA estimate and TreeMap imputation both show older forest stable to increasing rather than rapidly declining; the apparent loss reported elsewhere is a gross harvest flux, not a net stock decline. Contents. Derived 100 m GeoTIFFs, summary tables, analysis R scripts, quick-look figures, the Ecosphere Comment manuscript and Supporting Information, the fairness-audit memo, and a full methods-and-findings report (PDF). No FIA plot coordinates are included.