Wet-mesic Flatwoods CommunityWet-mesic Flatwoods, Abstract Page 1 Historical Range Prevalent or likely prevalent Infrequent or likely infrequent Absent or likely absent Photo by Suzan L. Campbell Overview: Wet-mesic flatwoods is a somewhat Rank Justification: The acreage of wet-mesic poorly drained to poorly drained forest on mineral flatwoods present in Michigan circa 1800 is difficult soils dominated by a mixture of lowland and upland to determine because the community type has hardwoods. The community occurs exclusively on characteristics that overlap those of several of the glacial lakeplain in southeastern Lower Michigan, forest types mapped based on General Land Office where an impermeable clay layer in the soil profile (GLO) survey notes, primarily hardwood swamp and contributes to poor internal drainage. Seasonal beech-sugar maple forest (Comer et al. 1995a, Kost hydrologic fluctuations and windthrow are important et al. 2007). Analysis of GLO survey notes reveals natural disturbances that influence community structure, that lowland forest dominated by hardwoods covered species composition, and successional trajectory of wet- approximately 570,000 ha (1,400,000 ac) of southern mesic flatwoods. Lower Michigan circa 1800 (Comer et al. 1995a). These stands were characterized by mixed hardwoods Global and State Rank: G2G3/S2 (490,000 ha or 1,200,000 ac), black ash (77,000 ha or 190,000 ac), elm (5,300 ha or 13,000 ac), and silver Range: Flatwoods communities characterized by maple-red maple (4,000 ha or 10,000 ac). The majority relatively flat topography, slowly permeable to of lowland forest acreage in southern Lower Michigan impermeable subsurface soil layers, and seasonal was associated with stream and river floodplains, hydrologic fluctuation occur scattered throughout the and is classified as floodplain forest (Tepley et al. eastern United States (NatureServe 2009). In the Great 2004, Kost et al. 2007). Extensive stands of lowland Lakes region, flatwoods communities on poorly drained hardwoods not associated with stream floodplains were glacial lakeplains and flat to undulating till plains concentrated on poorly drained lakeplain in Wayne, are distributed in Michigan, Ohio, Indiana, Illinois, Lenawee, Saginaw, St. Clair, Huron, Monroe, Sanilac, Pennsylvania, and Ontario, Canada (Fike 1999, Faber- and Macomb Counties (Comer et al. 1995a). These Langendoen 2001, NatureServe 2009). In Michigan, stands were characterized by southern hardwood swamp wet-mesic flatwoods is restricted to relatively flat on very poorly drained soils, and wet-mesic flatwoods glacial lakeplain in southeastern Lower Michigan in the on somewhat poorly to poorly drained soils. Wet-mesic Maumee Lake Plain ecological Sub-subsection (Albert flatwoods also likely occupied portions of the lakeplain 1995, Kost et al. 2007, Albert et al. 2008). characterized as mesic southern forest (i.e., beech-sugar maple forest) on the circa 1800 vegetation map (Comer et al. 1995a). Forests classified as hardwood swamp Michigan Natural Features Inventory P.O. Box 30444 - Lansing, MI 48909-7944 Phone: 517-373-1552 Wet-mesic Flatwoods, Page 2 Ecoregional map of Michigan (Albert 1995) depicting historical distribution of wet-mesic flatwoods (Albert et al. 2008) Michigan Natural Features Inventory P.O. Box 30444 - Lansing, MI 48909-7944 Phone: 517-373-1552 Wet-mesic Flatwoods, Page 3 and beech-sugar maple forest comprised a significant Currently, six occurrences of wet-mesic flatwoods proportion of the lakeplain in the early 1800s, covering are documented from Michigan, located in Macomb, > 60% of the land surface in Lenawee, Macomb, Wayne, and Monroe counties. These occurrences Monroe, St. Clair, and Wayne counties (Comer et al. range in size from 3 ha (7 ac) to 35 ac (87 ac), totaling 1995a). An additional natural community that may be approximately 96 ha (240 ac) (MNFI 2010). Only two successionally related to wet-mesic flatwoods, lakeplain occurrences are estimated to be of good to fair viability oak openings, covered significant acreage in Monroe (BC-rank), with the remaining occurrences estimated to (13%) and Wayne (5%) counties on sand lakeplain be of fair or fair to poor viability (C- to CD-rank). All of prone to frequent fires (Comer et al. 1995a, Kost et al. these sites are isolated woodlots in agricultural or urban 2007). The historic prevalence of hardwood swamp, landscapes, degraded by landscape-scale fragmentation beech-sugar maple forest, and lakeplain oak openings and hydrologic alteration (MNFI 2010). Additional in southeastern Lower Michigan suggests wet-mesic disturbances that have reduced viability of remnant flatwoods was common at the time of the GLO surveys. wet-mesic flatwoods over the past century include the introduction of non-native pests and pathogens (e.g., Conversion of the southeastern Michigan glacial elm blight and emerald ash borer), invasive plants, lakeplain for agricultural production accelerated in the and excessive deer herbivory, which have significantly early 1800s and resulted in the loss and degradation altered community structure, species composition, of wet-mesic flatwoods. Extensive drainage networks and successional trajectory (Barnes 1976, Rooney and created to expand agriculture lowered regional water Waller 2003, McCullough and Katovich 2004). For tables and reduced wet-mesic flatwoods to small, these reasons, the community is considered imperiled in isolated woodlots (Comer et al. 1995b, Knopp 1999). the state (Kost et al. 2007). This development led to the reduction of wetland acreage in southeastern Lower Michigan by 80-90%, the Physiographic Context: The Michigan range of wet- highest percentage loss of wetlands among all regions mesic flatwoods is in southeastern Lower Michigan, of the state (Comer et al. 1995b). Despite the significant in the Maumee Lake Plain Sub-subsection within the loss of wetlands statewide and in southeastern Lower Washtenaw Subsection (Albert 1995). This region has Michigan, MIRIS data (MDNR 1978) indicate that the longest growing season in the state, ranging from approximately 500,000 ha (1,200,000 ac) of lowland 160 to 170 days, averaging 163 days (Comer et al. hardwood forest occurred in southern Lower Michigan 1995b, Barnes and Wagner 2004). The daily maximum in the 1970s. This figure includes 28,000 ha (69,000 ac) temperature in July ranges from 28° to 29° C (82° to in the Maumee Lake Plain ecological Sub-subsection. 85° F), the daily minimum temperature in January The portion of this acreage represented by wet-mesic ranges from -10° to -7° C (14° to 19° F), and the annual flatwoods cannot be determined because wet-mesic average temperature is 9.3° C (48.7° F). Mean annual flatwoods does not correspond closely to any of total precipitation is 820 mm (32 in), with average the MIRIS cover type classifications. More recent seasonal snowfall less than 100 cm (40 in) (Eichenlaub data indicate 340,000 ha (840,000 ac) of lowland et al. 1990, Albert 1995, Barnes and Wagner 2004, MSU deciduous forest exists at present in the southern Climatology Office 2008). Lower Peninsula, including 17,000 ha (42,000 ac) in the Maumee Lake Plain (MDNR 2001). Again, the Wet-mesic flatwoods occurs exclusively in the portion of this acreage characterized by wet-mesic Maumee Lake Plain Sub-subsection in southeastern flatwoods cannot be determined with precision due to Lower Michigan (Kost et al. 2007, MNFI 2010). This broad cover type classification and resolution of the Sub-subsection is characterized by a broad, flat clay spectral data. However, the majority of lowland forest lakeplain containing broad channels of lacustrine in the ecoregion is comprised of fragmented, degraded sand that support low beach ridges and small dunes woodlots that do not closely approximate undisturbed (Albert 1995). Portions of the lakeplain with thick conditions. Some areas of wet-mesic flatwoods may clay deposits near the surface are characterized by be classified as upland deciduous forest in the MIRIS nearly level topography. In these areas, differences in and IFMAP land cover classifications due to the elevation of as little as 30 cm separate “upland flats” community’s naturally variable canopy composition from low, wet areas and depressions, and vernal pools (MDNR 1978, MDNR 2001). were historically common (Knopp 1999). Areas of Michigan Natural Features Inventory P.O. Box 30444 - Lansing, MI 48909-7944 Phone: 517-373-1552 Wet-mesic Flatwoods, Page 4 the lakeplain characterized by deep sand deposits on the forest floor. Seasonal water level fluctuations are better-drained and more topographically diverse, lead to mottling of the mineral soil layers. Soils on with development of beach ridges and low dunes on clay and sand/clay lakeplain contain a significant sand the otherwise level surface. Areas of the lakeplain fraction in the upper layers, and tend to be medium characterized by a relatively thin sand veneer over clay acid (pH= 5.6-6.0) to slightly acid (pH= 6.1-6.5) at are distributed throughout the clay plain, and exhibit the surface, although pH may be greater in sites with variable topography with level plains and low ridges high clay content in the upper layers. Clay fraction and (Knopp 1999). Wet-mesic flatwoods is concentrated on alkalinity increase with depth; soils are typically mildly the clay and sand/clay lakeplain, where impermeable alkaline (pH= 7.4-7.8) to moderately alkaline (pH= subsurface layers and low stream density impedes 7.9-8.4) 1 m below the surface (Knopp 1999). Soils on drainage and causes seasonal ponding (Albert et al. the sand lakeplain are characterized by very high sand 1986, Comer et al. 1995b). In these areas, wet-mesic fractions at all depths and pH ranging from strongly flatwoods occupies a topographic position between acid (pH= 5.1-5.5) at the surface to neutral (pH= 6.6- very poorly drained southern hardwood swamp in the 7.3) at greater depth. The neutral to alkaline subsurface wettest depressions and mesic southern forest where layers across the lakeplain are derived from calcareous slope and stream density permit favorable drainage.