2000 Progress Report: Riparian Reforestation in an Urbanizing Watershed: Effects of Upland Conditions on Instream Ecological BenefitsEPA Grant Number: R825798
Title: Riparian Reforestation in an Urbanizing Watershed: Effects of Upland Conditions on Instream Ecological Benefits
Investigators: Hession, W. C. , Charles, Donald F. , Hart, D. D. , Johnson, T. E. , Kreeger, D. A. , Newbold, J. Denis , Pizzuto, J. E. , Velinsky, D. J.
Current Investigators: Hession, W. C. , Charles, Donald F. , Hart, D. D. , Horwitz, R. J. , Kreeger, D. A. , Newbold, J. Denis , Pizzuto, J. E. , Velinsky, D. J.
Institution: Academy of Natural Sciences , Patrick Center for Environmental Research , University of Delaware
Current Institution: Academy of Natural Sciences , University of Delaware
EPA Project Officer: Hahn, Intaek
Project Period: June 1, 1998 through May 31, 2001
Project Period Covered by this Report: June 1, 1999 through May 31, 2000
Project Amount: $837,685
RFA: Ecosystem Restoration (1997) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Hazardous Waste/Remediation , Land and Waste Management , Ecosystems
Objective:The objectives of this research project are to: (1) understand the effects of riparian reforestation on the structure, function, and dynamics of stream ecosystems in urbanizing watersheds; (2) define exposure-response relationships for structural and functional stream ecosystem attributes (chemical, physical, and biological) based on the level of upland or contributing watershed urbanization for streams with and without riparian forests; (3) develop models so local and state decision makers can prioritize riparian reforestation efforts based on expected ecological benefit; and (4) measure and evaluate the rates at which various chemical, physical, and biological variables respond to riparian reforestation, in order to define effectiveness criteria for a restoration activity that may take many years to be fully manifested.
As of September 2000, detailed physical, chemical, and biological sampling has been conducted at 12 "paired-reach" study sites composed of adjacent forested and meadow stream reaches. In addition, sampling has been conducted at four forested stream reaches in highly urbanized watersheds, and two restored stream reaches. Six of the paired-reach sites, two of the forested reaches, and the two restored reaches were sampled during the 1998/1999 field season, and are referred to as Year 1 sites. The remaining six paired-reach sites and two forested reaches were sampled during the 1999/2000 field season, and are referred to as Year 2 sites. Sampling included watershed land cover, channel morphology, physical habitat, bank erosion, riparian vegetation, algae community composition, macroinvertebrate community composition, fish community composition, food web linkages, and nutrient uptake rates by benthic organisms. Our progress to date is in general keeping with the goals outlined in the experimental design (as described in the 1999 annual report, and modified from the original proposal), and we are on track to complete the project by the project end-date of September 30, 2001.
During the period from October 1, 1999 to September 30, 2000, all remaining field sampling at Year 2 sites was completed, and we began the computer entry, analysis, and interpretation of data from Year 1 and Year 2 sites. Also during this period, follow-up field studies of all ecosystem attributes previously sampled were conducted at one of the Year 1 paired reach sites, and one of the restored reaches. Followup sampling at the restored site was conducted to monitor ecological changes over time follow restoration, and at the paired-reach site to monitor annual variability in ecological attributes during the project period. Currently, we are nearing completion of all fieldwork specified in the experimental design, and are moving into the analysis and interpretation phase of the project. Followup macroinvertebrate sampling will be conducted in February 2001, and tracer injection studies will be conducted at two additional paired-reach sites in spring 2001. The following paragraphs provide a brief description of work in various component areas from October 1, 1999 to September 30, 2000.
Watershed Characterization. During winter 2000, a GIS-based assessment of watershed land cover and physiographic characteristics was conducted for all Year 2 sites. Several indices of "urban development" were calculated for each watershed including percent urban, percent impervious cover, percent urban within a 300 meter buffer of streams, percent impervious within a 300 meter buffer, ratio of percent urban to percent forest, and others. Urban development indices together with field sampling data will be used to evaluate the influence of urban development on stream ecology.
Riparian Vegetation. Quantitative measures of riparian vegetation at each Year 1 and Year 2 study site were used to develop indices of riparian "condition," which will be used to assess the influence of riparian vegetation to stream health. Calculated indices include basal area of trees, canopy density, abundance of native versus exotic species, and others.
Geomorphology. Geomorphic sampling in the past year included continued surveys of stream channel morphology, measurements of bank erosion rates at a number of reaches, and continued monitoring of bedload transport at Beaver Run. Progress was also made in data analysis and interpretation. Preliminary results suggest that riparian vegetation is more important than urban development in terms of influencing channel morphology, and that bank erosion rates are greater in meadow reaches than forested reaches.
Habitat Assessment. During spring and summer 2000, a detailed habitat assessment was conducted at each Year 2 site which included mapping habitat types, substrate size, cover, and abundance of large woody debris. Habitat data will be used to link channel geomorphology and observed biological changes among urban/non-urban and forest/non-forest stream reaches.
Chemistry. Water quality samples were collected seasonally from each Year 2 study site, and were analyzed for a standard suite of analytes. In addition, nutrient cycling experiments using injected bromide, nitrogen, and phosphorus tracers were conducted at one restored site and two of the Year 2 paired-reach sites. These experiments will provide information about nutrient uptake in forested and non-forested stream reaches along an urban gradient.
Algae. Algae and diatom samples from Year 2 sites were identified and counted during winter, 2000, and progress was made with data analysis and interpretation. Preliminary results suggest that forested reaches had higher Shannon-Weiner diversity values and lower percent dominance values compared with open reaches. Algal biomass was significantly higher in open reaches, and was associated with a proliferation of green alga Cladophora sp. and Spirogyra sp. Results of ordination and Monte Carlo analysis show that the environmental variables basin area, percent forest, percent urbanization, N:P and pH contributed significantly to the variability in diatom assemblages between sites.
Macroinvertebrates. Macroinvertebrate samples were collected from each Year 2 site during winter 2000. Samples were identified and counted during spring 2000. Macroinvertebrate sampling was conducted in February to coincide with the period of maximum larval abundance in low order streams of southeastern Pennsylvania. Preliminary results suggest that forested reaches have slightly greater species diversity than open reaches. The EPT index was lower and Chiromonid Dominance was significantly higher in urban watersheds than in non-urban watersheds.
Fish. Fish samples were collected at all Year 2 sites during late fall 1999, using a two- or three-pass depletion method. Selected sites were sampled in late fall 2000, as well. Fish sampling was conducted in late fall in order to survey a full season's production and to avoid sampling during low-flow periods. Preliminary results suggest a greater abundance of fish in most non-intermittent meadow reaches. There are some differences between urban and non-urban fish communities, but these are complicated by differences in stream size and other factors..
Food Web Linkages. Samples of leaf litter, algae, macroinvertebrates from
various feeding niches, and fishes from various feeding niches were collected
and analyzed for carbon and nitrogen isotopic composition to determine food web
linkages. In addition, gross biochemical characterization (i.e., total proteins,
carbohydrates, lipids) are being determined to help elucidate food quality for
various consumer groups. The carbon and nitrogen isotopic composition of the
various producers and consumers suggest that the peripyton is a dominant source
of carbon to macroinvertebrates and most fish during the summer. Leaf litter
(both fresh and microbially altered) was not a major food source during this
time period but maybe more in the winter. Further analysis of winter samples at
selected reaches is ongoing.