Restoration Ecology
Presiding: D Walther, Southern Illinois University; D Tullos, North Carolina State University
NB32A-01 10:30h
Homogenization of Environmental Condition and Benthic Communities in Restored Streams of the North Carolina Piedmont.
Stream ecosystems, as described through benthic communities and twenty environmental variables, exhibited decreased variances and reduced ordinal dimensionality in restored streams when compared to associated upstream reaches in this upstream-downstream investigation of stream restoration in the North Carolina Piedmont. Through paired t-tests of the environmental variables and several descriptions of community structure and function, the variance for restored stream reaches was lower than the upstream reaches for 70% of environmental characteristics, for 75% of Functional Feeding and Habitat Groups, and for all of the community descriptions, including the Q statistic, Shannon Index, Simpson Index, EPT taxa richness, and NCBI. Further, Nonmetric Multidimensional Scaling of the sites best expressed the upstream reaches on three axes, while the restored stream reaches required only one axis to effectively describe variation in the benthic communities. These results suggest that simplification of the biota may occur following steam restoration activities, indicating the biological losses associated with early recovery in these streams. While the science of stream restoration has advanced since the early construction and implementation at these sites, the consequential homogenization demonstrated by these biotic and abiotic stream corridor features emphasizes the importance of a concentrated effort to re-establish heterogeneity in restoration designs.
NB32A-02 10:45h
Assessment of Instream Restoration in the Cache River, Illinois: Macroinvertebrate Community Structure on Rock Weirs Compared to Snag and Streambed Habitats
Rock weirs were constructed in a degraded section of the Cache River in southern Illinois in 2001 and 2003 to prevent channel incision and protect riparian wetlands. We sampled macroinvertebrates in two older weirs and in two sites downstream of the restored section in April 2003, October 2003, and April 2004 to evaluate differences in community structure between weir, snag, and streambed (scoured clay) habitats. Three recently constructed weirs were also sampled in April 2004. Functional composition differed among sample dates and habitats. Although collector-gatherers consistently dominated streambed habitats, functional composition on weirs and snags was more variable. Filterer and predator biomass was generally higher on weirs, and snags harbored the only shredders collected in the system (Pycnopsyche spp.). Weirs generally supported higher biomass of Ephemeroptera, Plecoptera, and Trichoptera than other habitats. For example, mean EPT biomass on weirs in 2003 (April=187 mgAFDM/m2; October=899 mgAFDM/m2) was 4 to 10-fold higher than EPT biomass in snag or streambed habitats. Late instar Pycnopsyche contributed 41% of snag biomass in April 2004, resulting in EPT biomass similar to rock weirs. Results indicate rock weirs provide suitable stable substrate for macroinvertebrates and may enhance populations of sensitive EPT taxa in degraded systems.
NB32A-03 11:00h
The Relevance and Applicability of Phylogeographic Analyses to Conservation and Restoration Efforts
The combined analysis of geographic distribution and phylogenetic information, commonly known as phylogeography, is often overlooked by restoration and conservation efforts. This powerful tool can be extremely useful in both the planning and evaluation stages of a project. One use of phylogeographic analyses is the comparison of current and historical patterns of gene flow, allowing restoration efforts to focus on reconnecting recently isolated populations. They can also be used to identify genetically similar and therefore potentially better adapted populations to serve as a source for reintroductions, i.e. restoration genetics. From a conservation standpoint, phylogeographic studies help support causality between environmental stressors and changes in population structure (e.g., Theodorakis 2003). A brief explanation of phylogeographic analyses will be followed by case studies showing some of the applications of this tool for restoration and conservation projects.
NB32A-04 11:15h
Assessment of Stream Restoration Based on Measurements of Water Transit Time and Nutrient Retention.
Injection experiments (Cl, N, P) were performed to quantify stream nutrient retention and related hydrodynamics (water transit time and transient storage) before and after restoration. A 1-km length of Wilson Creek (KY) was re-located from an incised and straightened channel along the margin of its former floodplain to a meandering constructed channel that followed remnant floodplain contours. Thirty experiments were conducted during a spring index period (2002-2003) in the channelized stream (pre-restoration), naturalized stream (post-restoration) and reference stream (Harts Run). Water velocity was higher and transient storage was lower through much of the naturalized (restored) segment relative to pre-restoration and reference stream conditions. Reductions in water transit time were a result of higher specific discharge (ratio of discharge to width) in the narrower, constructed channel. Despite faster water transit, nutrient retention was higher in the naturalized segment with values comparable to (P) or exceeding (N) those observed in the reference stream. Highest water and nutrient retention occurred in naturalized segments that were connected to the former channel. Retention was attributed to re-circulating zones that exchanged water between the active channel and the upstream backwater which was a remnant of the former channel.
NB32A-05 11:30h
Effects of large woody debris addition on organic matter retention and nutrient uptake in three headwater streams in the Upper Peninsula of Michigan
To examine the influence of large woody debris (LWD) on organic matter retention and nutrient uptake, we added 25 logs (0.4m x 2.4m) to three replicate 100m reaches in tributaries of the Jumbo River, MI. We collected 1yr of pre-treatment data in upstream control and downstream treatment reaches before adding logs in May 2004. We measured nitrate, ammonium, and phosphate uptake velocity (vf), organic matter retention as depositional velocity (dep) using releases of stick, leaf and fine particle analogs, and physical characteristics such as geomorphology and transient storage. After 9 months, the logs altered stream geomorphology: distinct scour/deposition zones revealed gravel formerly buried by sand and increased the number of pools. In Walton Creek, average reach velocity declined; however, transient storage has not increased in any of the three streams. In Shane and State Creeks, during late summer there was an increase in organic matter retention, but after autumn leaf-fall differences disappeared. To date there has not been an increase in demand for nitrate, phosphate or ammonium. In summary, the experimental LWD addition rapidly changed stream geomorphology, e.g. number of pools and benthic substrates, but there appears to be a time-lag in biological response to LWD addition.