USDA wildlife-habitat ratings connected to island-scale SSURGO map units

Summary

This crosswalk connects the 1974 USDA soil survey’s wildlife-habitat ratings to the held SSURGO map units that intersect seven named islands: Beaver, Garden, High, Hog, Whiskey, North Fox, and South Fox. It makes a useful bridge between soil conditions, woodland and habitat suitability, and island geography while keeping the two source systems distinguishable.

The join covers 61 SSURGO map units by exact map symbol, 18 more as soil-series-name candidates, and 7 with no corresponding row or series name in the held USDA Table 4 index. The candidate tier is especially important for the Fox Islands, whose MI089 map-unit symbols differ from the Charlevoix County symbols used in the 1974 table. The component tables add 283 component records: 197 resolve to a unique USDA series row, 63 remain within multi-row USDA series families, and 23 have no matching series in the held USDA index.

Island summary

Counts are map units, not acres, species, or habitat occurrences. The JSON also preserves each map unit’s intersected area, polygon count, SSURGO symbol, map-unit name, and survey area.

Three join tiers

An exact map-symbol join means that the SSURGO musym, case-folded, is explicitly present in a scan-verified USDA Table 4 row. Examples include Beaver’s Rc Roscommon, Ca Carbondale, Gr Greenwood, DDB/DDC/DDE Deer Park, and TC Tawas map units. The crosswalk carries the USDA row’s 11 verified columns forward, but marks composite, association, complex, and undifferentiated map units with a caveat.

A component-series join reads held SSURGO comp.txt records keyed to a map-unit mukey. It records the component name and representative percentage. When one component name resolves to one USDA series row, that row’s historical ratings are exposed at component level. When a series has several USDA rows—as Emmet, Leelanau, Mancelona, Nester, and related families do—the candidates remain separate and no single rating is selected.

A soil-series-name candidate means the SSURGO muname names a USDA series but the symbol is not present in the 1974 table, or the map unit names several components. These are map-unit review leads, not rating assignments. The component tier now resolves many of those leads without flattening their mixtures.

Fox Island connectivity

The crosswalk materially changes how the Fox Islands can be represented in the ecology graph. North Fox has only three direct symbol matches—Lake beaches and two East Lake units—but its component records resolve DkF and DkD as 100% Deer Park, Du as 100% Dune land, DtB as 90% Detour, EaB/EaC as 90% East Lake, and Ie as 50% Iosco plus 30% Epoufette. The Emmet-Omena units are 50% Emmet but also contain Omena, which has no USDA row in this index.

South Fox has two direct matches—Eastport and Lake beaches—but the component records resolve DkF and DkD as 100% Deer Park, Du as 100% Dune land, and EdB as 93% Eastport. They also expose Leelanau/East Lake mixtures (LlB, LlD, LlE), 70% Mancelona in MrB, 55% Kalkaska and 35% East Lake in KeB, and 50% Mancelona, 30% East Lake, and 10% Kiva in MlD.

This is evidence of source coverage and a much stronger path for comparison. It still is not evidence that a Fox Island has one uniform habitat rating. The component percentages describe the SSURGO map-unit composition; they do not establish current forest or wildlife conditions, and multi-row USDA series families still require slope/map-symbol resolution before choosing a rating.

What the join supports

The crosswalk supports questions such as:

• Which islands contain SSURGO map units whose exact symbols have historical USDA ratings for woodland wildlife, wetland wildlife, coniferous plants, or wetland food and cover plants?
• Where do Fox Island map-unit names point toward the same soil-series families already described in the USDA table, even when symbols differ?
• Which soil settings can be compared with MNFI natural-community records, DNR forest stands, plant and tree indexes, GBIF observations, and bird or wildlife habitat studies?

It does not establish current forest composition, bird or mammal presence, nesting, abundance, parcel conditions, or management prescriptions. The USDA ratings describe suitability categories in a historical county soil survey; they are not field observations.

Evidence and limits

• SSURGO polygons and OSM island outlines are research layers, not legal boundaries or parcel determinations.
• Exact symbol matches can still be composite, association, complex, or undifferentiated map units; the JSON preserves mukind and an application note for every one.
• Component-series joins can expose a unique USDA series row, but they do not assign that row’s historical rating to the entire composite map unit.
• Multi-row series families and unmatched component names remain candidates for review rather than being collapsed into a single rating.
• Water, Lake bluffs, Wind eroded land, and the Beaver Ausable- Winterfield-Tawas complex illustrate why an unmatched or candidate result is not an absence claim.
• The USDA survey reflects fieldwork from 1959–1962 and conditions generally described around 1966; SSURGO and OSM layers are later research snapshots.

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Added 3 August 2026. Recent changes