Ecological Indicators 23 (2012) 46–55 Contents lists available at SciVerse ScienceDirect Ecological Indicators jo ur n al homep ag e: www.elsevier.com/locate/ecolind Integrating forest biomass and distance from channel to develop an indicator of riparian condition Richard Rheinhardt a,∗ , Mark Brinson a , Gregory Meyer a , Kevin Miller b,c,1 a Department of Biology, East Carolina University, Greenville, NC 27858, United States b Coastal Resources Management, East Carolina University, Greenville, NC 27858, United States c North Carolina Department of Environment and Natural Resources, Raleigh, NC 27699, United States a r t i c l e i n f o Article history: Received 16 June 2011 Received in revised form 25 January 2012 Accepted 14 March 2012 Keywords: Assessment Biomass Buffer Condition Inverse distance weighting Water quality a b s t r a c t Living and detrital biomass in a riparian buffer zones ameliorate diffuse-source pollution originating from adjacent landscapes, with higher nutrient removal potential, particularly with respect to nitrogen and sediments, associated with more biomass (i.e., older forests). Pollution removal is mediated by sediment trapping and uptake of nitrogen by plants and by denitrification by microbial communities in root zones using organic matter and root exudates as energy sources. However, as a consequence of various land management activities, the amount of biomass of most forest riparian zones is much lower than its potential, which is mature forest. This makes restoration of riparian buffer zones to mature forest an ideal way to both improve water quality and increase carbon sequestration. This study measures the amount of biomass aboveground and in soils for a variety of common, age-related condition-types associated with riparian buffer zones along low order (headwater) streams in agricultural landscapes of Coastal Plain North Carolina. The data are used to determine pollution removal potential in relation to stand age and distance from channel and a basis for developing an indicator of riparian condition. Mean biomass for common riparian cover types were Mature Forest (>50 y old): 483 Mg/ha; Young Forest (25–50 y old): 257 Mg/ha; Regenerating Forest (5–25 y old): 205 Mg/ha; recently Harvested Forest (0–5 y old): 165 Mg/ha; Perennial Herb: 67 Mg/ha; Shrub/Sapling: 63 Mg/ha; and Annual Rowcrop: 36 Mg/ha. Trees contained >96% of all aboveground biomass and >58% of total biomass present in the forested conditions. Biomass in recently harvested forests were >97% detrital, mostly due to the large amount of slash left after harvesting and the mostly intact soil organic matter. Most (>80%) of the biomass in non-forest cover types was stored in the detrital pool. By partitioning the riparian zone into inverse distance-weighted subzones based on distance from stream channel, we developed an indicator for determining riparian condition based on both biomass and proximity of biomass to channel. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction The condition of vegetation adjacent to streams has been shown to exert a major effect on water quality in downstream rivers, lakes, and estuaries (Boyer et al., 1994; Garten and Ashwood, 2003; Pinckney et al., 1998; Stanley, 1988, 1993; Stow et al., 2001). The condition of headwater riparian ecosystems is particularly impor- tant because headwaters constitute the majority of the stream length in watersheds (Brinson, 1993; Gomi et al., 2008; Rheinhardt et al., 2007b). Because most headwater reaches in agricultural landscapes lack sufficient buffers, the headwater portions of most ∗ Corresponding author. E-mail address: rheinhardtr@ecu.edu (R. Rheinhardt). 1 Present address: Bureau of Land Management, Grand Staircase-Escalante National Monument, Kanab, UT 84741, United States. agricultural stream networks provide a direct conduit for the intro- duction of most diffuse-source pollution into stream networks (Allan, 2004; Freeman et al., 2007; Naiman and Decamps, 1997), particularly nitrogen and sediment. Unfortunately, stream maps are usually too coarse to include the most-headwater reaches of stream networks (Baker et al., 2006). As a result, studies relating buffer condition to water quality have overlooked the most impor- tant portion of the stream network, and as a consequence, have likely underestimated the relationship between buffer condition and water quality at a landscape level. Further, many resource agencies have neglected to manage the buffer zone of headwa- ter reaches, which are the places most in need of protection for maintaining or improving water quality. Forest vegetation in near-stream buffer zones is important because it can assimilate and detain diffuse-source nutrients in surface and surficial groundwater that would otherwise be trans- ported downstream (Dosskey et al., 2010; Jacobs and Gilliam, 1985; 1470-160X/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecolind.2012.03.017