PROTECTING WISCONSIN'S BIODIVERSITY

Southern tamarack swamps are characterized by their minerotrophic organic soils of weakly to moderately acidic (pH >5.5) muck to mucky peat, canopy dominated by tamarack and swamp hardwood associates, and prevalence of tall shrubs, especially poison sumac and winterberry. They are most similar to bog relicts, but bog relicts have more acidic peat soils (pH 3.0-5.0), much higher coverage of Sphagnum moss (>40% cover, often approaching 90% cover) and higher coverage of ericaceous shrubs, especially leatherleaf and huckleberry. Bog relicts may have a sparse to moderate tamarack canopy but lack the hardwood associates and abundance of nutrient demanding shrubs.

Southern tamarack swamps have many species in common with northern hardwood swamps but the latter is usually dominated by hardwoods with tamarack usually sparse to absent. While northern hardwood swamps are more common in northern Wisconsin, they can be found scattered throughout southern Wisconsin in areas of calcareous groundwater seepage.

Southern tamarack swamps are also similar to northern tamarack swamps but the latter tends to be more acidic with a lower prevalence of strong calciphiles like poison sumac. Although the two communities are generally confined to the southern and northern parts of the state, respectively, they do overlap somewhat in the Central Sands region. Although this region is within and south of Wisconsin's climatic tension zone, northern tamarack swamps are common in the ancient lakebed of Glacial Lake Wisconsin where flat, acid peatlands are underlain by nutrient-poor sands. Just to the east in the end moraines above the ancient lakeplain, southern tamarack swamps predominate due to the more minerotrophic groundwater seeping through the calcareous glacial deposits. Thus, nutrient status and the relative abundance of nutrient-demanding species is more useful than latitude in differentiating the two communities.