Soil, substrate, hydrology, and landform evidence crosswalk

What this crosswalk adds

Soil evidence was already present in the corpus, but it was scattered among MNFI occurrence pages, GLO field notes, SSURGO intersections, physical-geology layers, and the newer EGLE mapped-dune reports. This crosswalk makes those records searchable together while preserving their different scales and dates.

It contains 124 evidence rows:

The 16 input records without soil, landform, or water text are not silently treated as negative evidence: 13 are non-soil MNFI 2015 records and three are GLO 1845–1849 records. Their identifiers are retained in the JSON audit as excluded input records.

MNFI soil and hydrology gradients

The 2017 MNFI records show that “forest,” “bog,” or “shore” is not a sufficient soil description. Fox Lake Bog is a large ombrotrophic bog on poorly drained lakeplain, with deep sphagnum peat over sand; the peat is strongly acidic, saturated, and inundated along the lake margin. Greene’s Lake Bog adds a weakly minerotrophic condition, localized groundwater/surface-water enrichment, and sphagnum hummock-and-hollow microtopography.

French Bay’s boreal forest shows a different substrate pattern: a shallow acidic A horizon at pH 4.5–5.0 over acidic medium-textured sands at pH 5.0–6.0, with sand locally over cobble. The source links former sand shoreline to pine dominance and former limestone cobble shore to northern white-cedar dominance. That is a source-preserved ecological relationship, not a rule applied to every shoreline forest.

Across the 43 occurrence records, the extracted evidence terms include acidic, alkaline, calcareous, clay, cobble, dune, fen, groundwater, lakeplain, limestone, marl, marsh, organic material, peat, poorly drained, sand, saturated, seepage, sphagnum, swamp, till, water-level fluctuation, and wetland. The broader crosswalk vocabulary also captures historical stone and stony ground, beaches, bluffs, and dune blowouts. The JSON retains the exact source sentences behind every derived term.

Garden and High Island soil contrasts

The 2015 MNFI addendum provides unusually useful forest-soil comparisons. The Garden Island boreal forest is described on shallow alkaline loams and loamy organics over limestone cobble at pH 7.5–8.0. High Island’s boreal forest has alkaline sands, gravelly sands, and clayey sands at pH 7.5–7.8, with a shallow acidic organic layer at pH 4.5–4.8. High’s dry-mesic northern forest has a shallow acidic horizon over acidic sands at pH 4.5–5.0, while Nezewabegon Forest has acidic loamy sands at pH 5.0–5.5.

Garden’s Red Oak Garden is especially valuable because it preserves contrast within one named site: a southern polygon with shallow alkaline loams over limestone cobble and a northern polygon with deeper sands over cobble and an acidic organic/sand horizon. The vegetation and tree records should therefore be read with soil position and substrate, not as a single islandwide forest class.

Historical GLO substrate vocabulary

The GLO layer is not a modern soil survey, but it provides a rare historical vocabulary for the physical settings encountered by surveyors. The 1845–1849 records describe thin vegetable soils, sand, gravel, stone, cobble, marsh, swamp, low ridges, beaches, windfall, and fire disturbance across Big Beaver, Garden, Hog, Hat, High, Ojibwa, Trout, Whiskey, Gull, and both Fox Islands.

North Fox has page-bounded descriptions involving hard-pan, coarse gravel and pebbles, rocky or pebbly shore, clay banks, gravel beach, and lime pebbles. South Fox is described with fine sand, vegetable mould, and sand drifts. Big Beaver records repeatedly connect first-, second-, and third-rate ground to sugar, beech, birch, maple, hemlock, fir, cedar, spruce, pine, tamarack, ash, aspen, marsh, and swamp. These are surveyor line observations and historical land-use context, not inferred modern soil polygons.

The separate 1942 records for Shoe and Pismire add a later comparison point: low gravel/boulder or gravel/humus formations, sparse weeds and grass, small willows, and dated gull or duck use. They should remain separate from the 1845–1849 descriptions because their source form and date differ.

Fox and Hog landform processes

The EGLE mapped-dune records connect substrate to active landform processes. North Fox’s MDC 76 is a parabolic barrier-dune system with active foredune, blowouts, abrasion, sand burial, and aeolian movement, grading into vernal pools, old forest, and a sand-and-gravel beach. South Fox’s island-scale MDC 75 combines perched and parabolic dunes, beach ridges, clay bluffs, landslides, seepage, blowouts, and interdunal depressions. Its interdunal wetland occurrence shows standing water, water-level-dependent vegetation, calcareous indicators, and wildlife use that can vary by year.

Hog’s MDC 101 is lower relief: wooded dune-and-swale terrain meets Great Lakes marsh and limestone cobble shore. The source describes water-level fluctuation, storm waves, and ice shear reworking the cobble substrate and removing fine mineral and organic sediment. Only part of the larger MNFI occurrences lies in this mapped complex, so the record cannot be generalized to every Hog Island soil or forest stand.

Map context and scale discipline

The crosswalk attaches three kinds of island-level context:

• SSURGO mapunit names and clipped areas for all seven named islands, including sand, loam, dune, beach, bluff, gravelly-sandy-loam, and wetland-associated mapunits where the regional map reports them.
• The MNFI environmental crosswalk’s island-level hydric-soil, NWI, Quaternary, and circa-1800 context for the four islands represented there.
• The physical-geology crosswalk’s aquifer, SGMC, bedrock, fault, and glacial-lobe context for all seven islands.

These joins answer “what regional mapped context surrounds this island?” They do not answer “which soil polygon contains this individual MNFI occurrence?” The latter requires authorized occurrence geometry or field-level soil data. Representative EGLE points likewise remain representative points, not natural-community boundaries.

Seven-island SSURGO and aquifer frame

The synchronized matrix makes the island-scale soil comparison explicit. The SSURGO columns count map-unit intersections in the held polygon extract; “exact-symbol units” counts the subset whose map symbols resolve directly to a reported map-unit record; and component counts come from the associated SSURGO component tables. The last two columns keep the soil frame connected to the regional glacial-drift aquifer layer and show the largest reported units, not a complete soil-series list:

The Fox rows show why “map-unit count” and “resolved exact-symbol count” must remain separate: a regional intersection can be present even when the held symbol/name crosswalk resolves only part of the extract. The aquifer column is also a regional screening class, not a well-yield, groundwater-quality, or parcel-scale determination. None of these values assigns a soil series to a tree, MNFI occurrence, bird record, or property.

Added 3 August 2026. Recent changes