Geology and Setting:

The 835 acre Lee and Rose Warner Nature Center (Warner) is located on an isolated remnant of the St. Croix Moraine that was deposited approximately 10,000 years ago. This phase of the Wisconsin glaciation entered the region from the Lake Superior Basin to the northeast depositing glacial till that is primarily comprised of Pre Cambrian igneous and metamorphic rock low in carbonates. Conversely, the bedrock underlying the till at Warner is comprised of Paleozoic limestone and sandstone exposed along the course of the St. Croix River approximately two miles to the east. The rolling ground moraine of the area forms a kettle/moraine complex known as the Baldwin Plains where practically every dip in the topography holds a wetland or lake (kettle). There are few streams, but there are more than 250 lakes over ten acres in size and thousands of wetlands within a ten-mile radius. The chemistry of each wetland or lake depends on the source of the groundwater (the underlying limestone or glacial till). For example, the acidic, low calcium, soils and shallow ground water of the St. Croix Moraine has produced numerous poor fens and bogs in and around Warner. In fact, lakes and wetlands on the Warner Nature Center proper are generally all dilute waters with pH values that range from near neutral (pH 7) to acidic (pH 3.8). However, wetlands and streams a few kilometers to the east draw water from the bedrock and thus form calcareous fens and artesian springs. Recent research on Warner’s Terrapin Lake revealed that it has one of the most diverse aquatic plant communities in Minnesota. This diverse set of undeveloped aquatic habitats supports a very diverse odonate fauna. The Warner Nature Center location will emphasize lake and wetland species while the other two locations will emphasize river and stream species.

Site 2 – The St. Croix Watershed Research Station (45.1712 -92.7607)

16910 152nd St North, Marine on St. Croix, MN

The St. Croix Watershed Research Station is located along a backwater of the St. Croix River. As you might expect, more stream and riverine species representing the Gomphidae, Cordulegastridae, and Macromiidae can be found at this site. Possible species include Gomphurus ventricosus (Skillet Clubtail), Gomphurus vastus (Cobra Clubtail), and Hylogomphus viridifrons (Green-faced Clubtail). There are three small calcareous streams that originate on the property, all fed by hundreds of artesian springs. The springs are the known breeding sites for Amphiagrion abbreviatum (Western Red Damsel) and Enallagma antennatum (Rainbow bluet). There are also several calcareous wetlands, fens, and one small impoundment. This site provides a nice mix of genera and species.

Site 3 – Pine Needles (45.2099, -92.7670 )

18037 St. Croix Trail North, Marine on st. Croix, MN

The Pine Needles site encompasses 20 acres of habitat surrounding a historic riverside cabin built in 1914. The site includes almost a half mile of shoreline along the St. Croix River and several small streams that originate directly from free flowing springs that arise directly from sandstone/limestone bluffs on the west side of the property. Some of these seeps are the known breeding habitat of Cordulegaster obliqua (Arrowhead Spiketail). The St. Croix River is the breeding site for numerous rare and uncommon Gomphidae including Ophiogomphus susbehcha (St. Croix Snaketail), Ophiogomphus howei (Pygmy Snaketail), and Stylurus scudderi (Zebra Clubtail). Other notable species include Neurocordulia yamaskanensis (Stygian Shadowdragon) and Neurocordulia molesta (Smoky Shadowdragon). See the flight charts for a more complete list of species.