One Hundred and Thirty Years of Plant Succession in a Southeastern Wisconsin Lowland

The post—glacial history of a marl and peat marsh contained evidence that early hydrarch succession may have been relatively rapid due to higher plant as well as invertebrate animal productivity. Pristine open marsh, sedge meadow, and wet prairie were held in quasi—equilibrium by alternations of floods during wet periods and fires during drought. Fires either checked terrestrial advancement or turned it back to earlier aquatic stages by organic substrate removal. Recent fire control and continued lowering of water levels hastened intermediate hydrarch succession by quickly and directly converting aquatic to terrestrial sites. A peat burn increased soil pH and soil nutrients, particularly the phosphates, and eliminated plant competition so that open marsh was immediately invaded by aspen forest, which if uninterrupted, will be converted to lowland hardwood forest. Recurring fires could perpetuate the sucker—sprouting aspen, but burning decadent aspen forest might originate true prairie. Although fire is usually catastrophic and retrogressive, it produced successional stability and even acted as a successional accelerator in this lowland.