Late-successional and old-growth forest across the Northeast: definition, mapping, temporal (in)stability, and the consolidated regional product archive

Aggregated results, analysis code, figures, and the full multi-state raster product set supporting the Northeast late-successional and old-growth (LSOG) forest work. The study defines LSOG through a multi-axis structural label built on U.S. Forest Inventory and Analysis (FIA) data, produces design-based four-state estimates (Maine, New Hampshire, Vermont, New York) with a New Brunswick provincial-inventory extension, maps the probability of LSOG from AlphaEarth satellite embeddings, and assesses the temporal stability of those embedding-based predictions. Headline findings. (1) Design-based FIA estimates place any-LSOG at roughly 15% of forest in Maine, 28% in New Hampshire, 28% in Vermont, and 33% in New York (2019-2023 panel). (2) A single-time LSOG classifier trained on the multi-axis structural label discriminates well against reserve-anchored references (AUC ~0.84). (3) Canopy-height resolution and AlphaEarth-plus-canopy-height fusion tests show only marginal gains over AlphaEarth alone. (4) AlphaEarth embedding vectors are highly stable year to year (median cosine similarity ~0.98), a classifier refit independently each year shows no temporal decay (pooled per-year AUC ~0.64 to 0.65), yet year-to-year embedding change does not track disturbance at the plot scale (change-detection AUC ~0.45, at chance), so LSOG trends should rest on design-based FIA rather than on differencing satellite embeddings between years. Consolidated regional products (v3.0.0). This version brings the full multi-state raster product set for the Acadian and northern New England region into this single archive, so that all openly available LSOG data, code, and products now live under one concept DOI (10.5281/zenodo.20614496). Added products span Maine, New Hampshire, Vermont, New York, Massachusetts, and New Brunswick: per-state LSOG probability at 10 m and 30 m, calibrated LSOG grade and grade index at 30 m, per-class probability at 30 m, 2018 to 2024 change layers, and 150 m conservation-prioritization surfaces, together with the regional probability mosaic, the finalized regional and Maine technical reports, and the companion manuscript. This record supersedes and absorbs the earlier Maine mapping record (10.5281/zenodo.21070969) and the regional products record (10.5281/zenodo.21070977); cite this concept DOI going forward. Associated outputs. These results and products underpin two CRSF technical reports, a four-state regional report and a Maine-focused report (Weiskittel, Woodall and D'Amato 2026), and two peer-reviewed manuscripts in review: a methods paper (Ecological Applications) and a Comment on Hagan et al. 2026 (Ecosphere). Restricted data. FIA true plot coordinates, New Brunswick MagPlot per-plot records, and JDI ownership layers are NOT included and remain restricted; only aggregated summaries (H3 hexagon and state-level tables), analysis code, figures, and the derived raster products are provided. The lead file 00_LSOG_NE_graphical_abstract.png is a graphical abstract summarizing the study.