Environmental Site Index (ESI) v8: climate-led forest site-potential surfaces for North America

First public release (record version 1.0.0) of the gridded Environmental Site Index (ESI) v8 surfaces, a climate-led estimate of forest site potential on the site-index scale (meters). Includes a CONUS 1 km surface, a North America ~1 km surface, and a 30 m cross-border Acadian surface (Maine, New Brunswick, Nova Scotia, Prince Edward Island). Read before use. ESI predicts a harmonized site-index target; its honest accuracy against measured site index is a spatially blocked R-squared near 0.45 to 0.51 for the broad-scale surfaces. Absolute values are not comparable across regions (site-index scale conventions differ), so cross-region productivity comparison should use a realized-productivity measure such as BGI. Where a layer is finer than 1 km, the climate component is terrain-downscaled 1 km; only terrain and soils carry genuine fine structure. Each surface is valid only within its calibration domain. Acadian 30 m surface is a v1 prototype. It is released as a first cut. Its independent validation against measured Maritime site index is weak (Pearson near 0.15) and it is calibrated mostly against United States side plots; true Canadian permanent-plot coordinates were not yet available at release. A soils-augmented refit was tested and did not improve the surface (restricting training to the Acadian box compressed the site-index range further), so this v1 uses the broader v8 climate-and-terrain surface. The Acadian layer should be treated as a methods demonstration pending the Canadian plot data, not a production Maritime product, and will be superseded in a later version.