Chapter 6: Meadow-Stream Processes and Aquatic Invertebrate Community Structure

Riparian areas make up less than 1 percent of the total area of the Great Basin, yet they provide many critical ecosystem services, and they support a disproportionately large percentage of the regional biodiversity (Hubbard 1977; Saab and Groves 1992). Jenson and Platts (1990) estimate that over 50 percent of the riparian areas in the Great Basin are in poor ecological condition due to various forms of disturbance and climate change (Chambers and Miller 2004). Ongoing stream incision in the region and progressive degradation of riparian meadow complexes make meadow systems a management priority (Chambers and Miller 2004). Understanding the connections between benthic macroinvertebrate (BMI) communities and meadow-stream environmental characteristics provides managers with important information about the effects of this degradation. Biological surveys of BMI communities have been used along with water chemistry analyses to indicate environmental conditions in other lotic ecosystems (Yoder and Rankin 1998; Karr and Chu 1999). Benthic invertebrates are relatively long-lived, diverse, and ubiquitous (Linke and others 1999). Due to these factors and because their response to disturbance is broad, they are good indicators of system changes. Previous ecological research in Great Basin streams of Nevada has focused on links between riparian condition and aquatic invertebrate community structure (Kennedy and others 2000); invertebrate community responses to spring disturbance (Sada and others 2005); and assemblage clustering driven by natural environmental gradients (Myers and Resh 2002). Our study builds, in part, upon the work of Kennedy and others (2000), who found that community composition was strongly related to a number of environmental parameters such as total dissolved residue, fish diversity, and percent silt. Since relationships between landscape and benthic composition have been demonstrated, we sought to examine whether such relationships could be shown using common benthic measurements. While there have been studies of the nutrient dynamics of central Great Basin streams, little research has documented the temporal and spatial patterns of environmental characteristics and the resulting implications for aquatic invertebrate communities in meadow reaches. Amacher and others (2004) demonstrated that catchment lithology is an important driver of stream water chemistry in Kingston Creek and other upland Toiyabe streams. Mast and Clow (2000) showed that early season snowmelt can dilute aqueous nutrients derived from catchment lithology. In 2005, we initiated a study to determine if multimetric bioassessment methods that are commonly used by management agencies in the United States are sensitive to riparian meadow influences on benthic communities at Kingston Creek. Comparing multimetric and multivariate methods, we investigated whether a meadow environment affects community structure by sampling invertebrates and environmental characteristics at finer spatial and temporal scales than in previous work.