Ecological Engineering 35 (2009) 1036–1042 Contents lists available at ScienceDirect Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng Soil bacterial community structure and physicochemical properties in mitigation wetlands created in the Piedmont region of Virginia (USA) Changwoo Ahn ∗ , Rita M. Peralta Department of Environmental Science and Policy, George Mason University, 4400 University Drive, Fairfax, VA 22030, USA article info Article history: Received 16 July 2008 Received in revised form 6 January 2009 Accepted 23 March 2009 Keywords: Soil bacterial community LH-PCR DNA finger printing Soil carbon and nitrogen ratio Wetland soils Created mitigation wetlands abstract Wetland creation is a common practice for compensatory mitigation in the United States. Vegetation attributes have been used as a quick measure of mitigation success in most post-creation monitoring, while little attention has been paid to soils that provide the substrate for flora and fauna to establish and develop. Created wetland soils are often found not indicative of ‘hydric soil’ with a lack of development of physicochemical properties (i.e., bulk density, moisture content, and carbon and nitrogen contents) com- parable to those in natural wetlands. Moreover, soil bacterial communities are rarely examined though they are integrally involved in biogeochemical functions that are critical for ecosystem development in created wetlands. We analyzed soil physicochemistry and profiled soil bacterial community structure using amplicon length heterogeneity polymerase chain reaction (LH-PCR) of 16S ribosomal DNA in three relatively young wetlands (<10 years old) created in the Piedmont region of Virginia. We examined the data by site and by specific conditions of each site (i.e., induced microtopography and hydrologic regime). Multidimensional scaling (MDS) and analysis of similarity (ANOSIM) showed clear clustering and signifi- cant differences both in soil physicochemistry (Global R = 0.70, p = 0.001) and in soil bacterial community profiles (Global R = 0. 77, p = 0.001) between sites. Soil physicochemistry (Global R = 1, p = 0.005) and bac- terial community structure (Global R = 0.79, p = 0.005) of soils significantly differed by hydrologic regime within a wetland, but not by microtopography treatment. A significant association was found between physicochemistry and bacterial community structure in wetland soils, revealing a close link between two attributes ( = 0.39, p = 0.002). C/N (carbon to nitrogen) ratio was the best predictor of soil bacterial com- munity patterns ( = 0.56, p = 0.001). The diversity of soil bacterial community (Shannon’s H ′ ) differed between sites with a slightly higher diversity observed in a relatively older created wetland, and seemed also fairly determined by hydrologic regime of a site, with a relatively dry site being more diverse. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Created wetlands often show little evidence of ecosystem devel- opment comparable to that of their natural counterparts, and many wetlands created to mitigate wetland losses fail to meet basic suc- cess criteria within the time frame legally mandated for monitoring (National Research Council, 2001; Spieles, 2005). In most cases of wetland mitigation, some measure of vegetation is a performance standard, and in many cases, vegetation is the only performance standard in the post-creation monitoring as a quick surrogate for the biogeochemical condition of the wetland and as a measure of success (Spieles, 2005). However, structural attributes of vegeta- tion may be a poor measure of wetland functions that should be in development (Breaux and Serefiddin, 1999). ∗ Corresponding author. Tel.: +1 703 993 3978; fax: +1 703 993 1066. E-mail address: cahn@gmu.edu (C. Ahn). Soil properties are often the least studied indicator of wetland quality (Shaffer and Ernst, 1999; Stolt et al., 2000). Soil physico- chemical properties are often found not indicative of ‘hydric soils’ in created wetlands. Moreover, failures of created/restored wetlands are often attributable to a lack of soil development (Bishel-Machung et al., 1996; Stolt et al., 2000; Cole et al., 2001; Campbell et al., 2002). Soil microbial communities are integrally involved in biogeochem- ical cycles and their activities are crucial to the functions of wetland systems because they play key roles in energy flows and nutrient transformation (Batzer and Sharitz, 2007), but are rarely examined in assessing ecosystem development in created wetlands. Ecolog- ical engineers often assume that microbes are passively reacting to abiotic and biotic stimuli rather than controlling soil processes explicitly, and have typically treated them as a “black box” (Nichols, 1983; Busnardo et al., 1992; Jordan et al., 2003). Yet these subsurface domains are now known to contain higher species diversity than the aboveground world (Beare et al., 1995; Pace, 1997; Kennedy, 1999; Emmerling et al., 2002). Moreover, there is increasing evi- 0925-8574/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ecoleng.2009.03.005