Ecological Engineering 17 (2001) 423 – 428 Assessing the relationship between biomass and soil organic matter in created wetlands of central Pennsylvania, USA Charles Andrew Cole *, Robert P. Brooks, Denice Heller Wardrop Penn State Cooperatie Wetlands Center, Forest Resources Laboratory, Uniersity Park, PA16802, USA Received 15 June 2000; received in revised form 29 September 2000; accepted 6 November 2000 Abstract Created wetlands are frequently structurally different from the natural wetlands they are intended to replace. With differences in structure might come differences in function. Most created wetlands in central Pennsylvania have very low amounts of soil organic matter relative to levels found in natural wetlands. However, anecdotal evidence also suggests that plant production is equivalent in created wetlands to natural wetlands. There is little evidence to indicate that this plant biomass in created wetlands is finding its way into the soil as organic matter. This might translate into a lack of function in the mitigation wetlands. To address this issue, we studied plant biomass production in seven created wetlands in central Pennsylvania (USA). We measured above- and below-ground biomass and compared results with known values of soil organic matter and hydrology for the same wetlands. We found biomass to be approximately equivalent to that produced in natural freshwater marshes, although the below-ground component was somewhat higher. We found no relationship of biomass to soil organic matter, even though site conditions were wet enough to retard plant decomposition. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Biomass; HGM; Hydrogeomorphic; Mitigation; Pennsylvania; Wetland; Wetland creation www.elsevier.com/locate/ecoleng 1. Introduction In the United States, wetland ecosystems are frequently created as replacements for natural wetlands destroyed during some developmental activity. The expectation is that created wetlands will become functional wetlands (defined as com- parable to similar natural [reference] wetlands of the same type). Many authors have questioned this assumption (Race, 1985; Langis et al., 1991; Zedler and Langis, 1991; Reinartz and Warne, 1993; Mitsch and Wilson, 1996; Cole et al., 1998; Shaffer and Ernst, 1999). Traditionally, to assess created wetland success, we consider structural characteristics of the plant community such as species richness (Laidig and Zampella, 1999) or percent cover (Wilson and Mitsch, 1996; Perry and Hershner, 1999). Gala- towitsch and van der Valk (1994) noted that structure (being more readily measured) is com- * Corresponding author. Present address: Center for Water- shed Stewardship, The Pennsylvania State University, 227 East Calder Way, University Park, PA 16801, USA. Tel./fax: +1- 814-8655735. E-mail address: cac13@psu.edu (C.A. Cole). 0925-8574/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0925-8574(00)00171-3