Grantee Research Project Results
Final Report: Watersheds and Wetlands: Large Scale Disturbances and Small Scale Responses
EPA Grant Number: R824905Title: Watersheds and Wetlands: Large Scale Disturbances and Small Scale Responses
Investigators: Cole, Charles Andrew , Wardrop, Denice Heller , Brooks, Robert P.
Institution: Pennsylvania State University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 1996 through August 31, 1999 (Extended to August 31, 2000)
Project Amount: $742,079
RFA: Water and Watersheds Research (1996) RFA Text | Recipients Lists
Research Category: Watersheds , Water
Objective:
Currently, information necessary to understand watershed-scale impacts from permit decisions made at a wetland-scale is lacking. We do not know how individually small wetland impacts cascade to cumulative watershed impacts. Moreover, as wetlands are permitted for damage or destruction, created replacements are becoming common. Very little quantitative information is available on the success of these efforts, including data on possible successional trajectories. Our general objectives are to: (1) assess characteristics of sets of reference and created wetlands (within four watersheds in central Pennsylvania) by watershed, disturbance, and hydrogeomorphic (HGM) category; and (2) assess characteristics of created wetlands of different ages to delineate wetland successional trajectories. Furthermore, (3) we will assess watershed disturbance regime and HGM class within those reference and created wetlands to show the range of conditions possible for natural sites and how close created sites approach that goal; (4) we will assess natural succession in reference wetlands using seed bank analyses and Cs137 and Pb210 soil dating, and within created sites by substituting space for time; and (5) we will use disturbance theory to assess the impacts of surrounding landscapes on the composition and function of wetlands within a watershed. Successional processes will be assessed using Odum's trends in ecosystem development (Odum, 1969) as a framework.
Summary/Accomplishments (Outputs/Outcomes):
Wetlands in the Landscape. Assessment of wetlands is inaccurate without first completing an inventory of wetlands. National Wetland Inventory (NWI) maps are noted for their inaccuracy in heavily forested regions. This study looked at underlying geology to develop a set of decision rules that would allow for the assignment of wetland probabilities based on broad geologic features. We looked at formations within the floodplain, formations outside of the floodplain, geologic contacts, and fault zones. Each formation, contact, or fault was assigned a probability based on the amount of wetlands found through a field verification effort. Probability classes were checked in a region with good NWI coverage (Spring Creek) and then against one with poor coverage (White Deer Creek). Geologic and topographic settings had a dramatic effect on the occurrence of wetlands. Fault zones account for the greatest area of wetlands, followed by geologic contacts and formations within the floodplain. The relative amount of wetland area in each of these geologic settings is the result of variation in primary and secondary porosity of the formation(s) involved. This project demonstrated the utility of using broad geologic parameters for predicting wetland occurrence in the landscape. A correct identification of extant wetland resources is the first step towards intelligent management of those resources.
Hydrology. We installed 63 water level recorders at more than 40 wetlands throughout Pennsylvania. Our data collection efforts approach 6 years for some sites, and 29 of 39 sites have data records for more than 3 years. We have been able to demonstrate differences in hydrologic behavior by HGM subclass (Cole, et al., 1997; Cole and Brooks, 2000a). From this analysis, we have been able to develop a general predictive model of hydrologic characteristics by HGM subclass, thereby allowing managers to assess hydrology without a long-term data set. Disturbance is a factor in hydrologic behavior and serves as a surrogate for watershed. We have shown that hydrology of created wetlands does not equal that of their natural counterparts (Cole and Brooks, 2000b). It is clear from our data that created wetlands do not resemble their natural counterparts (Cole, et al., 1998). We are working in collaboration with the U.S. Environmental Protection Agency's National Health and Environmental Effects Research Laboratory in Corvallis, Oregon, to analyze the importance of sampling interval in hydrologic assessment (Shaffer, et al., 2000). We found that regular, but infrequent sampling (monthly), is all that is required for the generation of basic hydrologic characteristics. However, more intensive sampling (daily) is needed for the determination of the impacts of events such as flooding. We also are examining regional differences in hydrology to determine if similar wetlands in Oregon and Pennsylvania are hydrologically comparable (Cole, et al., in preparation).
Soils and Sedimentation. Sedimentation rates and deposited sediment characteristics in 25 wetlands in central Pennsylvania were measured. Wetlands represented several watersheds and HGM subclasses. Sedimentation rates were assessed using Plexiglas disks, and annual organic and inorganic loadings were measured. Sedimentation rates varied from 0 to 8 cm per year with sedimentation rates significantly correlated with surrounding land use and HGM subclass. Overall, mean mineral and organic accretion rates were 778 g m2 yr-1 and 550 g m2 yr-1. Mean mineral and organic accretion rates differed by HGM subclass. The highest mineral accretion rates were for headwater floodplains, followed by impoundments, riparian depressions, mainstem floodplains, and slopes. The highest organic accretion rates were for riparian depressions, followed by impoundments, slopes, headwater floodplains, and mainstem floodplains. The potential effects of landscape disturbance on these sedimentation rates also was investigated to develop a conceptual model to predict sedimentation rates for a given wetland in a variety of landscape settings. Characterization of wetland plant communities showed clear associations between individual plant species and their ability to tolerate sediment loads. In general, tolerant species increased their dominance over increasing sedimentation gradients.
Macroinvertebrates. Wetland macroinvertebrates were sampled on a subset of the reference and created wetlands. Three HGM subclasses were assessed (headwater floodplain, riparian depression, and slope) in conjunction with high and low levels of disturbance. Sites that were wetter had significantly more macroinvertebrates (riparian depressions > slopes > headwater floodplains). Disturbed sites had greater numbers of individuals, though neither HGM nor disturbance was a significant factor in either taxa richness or diversity. The dominant taxa were the true flies (Diptera), and the Chironomidae were the most dominant group within the diptera. Oligochaetes were the next most dominant taxa. These taxa are known for being pollution tolerant in streams, but their role in wetlands is less well understood. As generalists, they may offer little information regarding hydrology or disturbance. If only presence/absence of taxa is analyzed, then HGM becomes a significant predictor of macroinvertebrates in saturated soils. In ephemeral pools, disturbance was a significant factor for the presence and absence of taxa. The created wetlands also were studied for their macroinvertebrates. In general, taxa diversity is lower than for the reference wetlands, disturbed sites notwithstanding. Most of the individuals were dipterans.
Biomass. We examined above- and below-ground biomass (g/m2) for created wetlands ranging between 5 and 20 years of age and compared it with biomass from reference wetlands. We discovered that total biomass was higher than is typically reported for natural wetlands of mid-latitudes. However, our created sites also had biomass comparable to the reference sites. Many studies have found much less biomass on created wetlands. We could find no relationship between biomass and the age of a created wetland. We could not find any relationship between biomass production, age of the wetland, and soil organic matter. The development of soil organic matter is critical for the restoration of function in created wetlands. Sites that should have been accumulating soil organic matter over time were not. Our findings indicate that the created wetlands we found in the landscape do not resemble the natural sites that had been destroyed. Other work has noted the lack of increasing soil organic matter with age (Bishel, 1994; Campbell, 1996), but our assessment of biomass production was a critical element to understand. Some mechanism is missing in created wetlands that prevents the accumulation of organic matter. This does not bode well for restoration efforts.
PCMs. We now have substantially increased the amount of data from reference wetlands in Pennsylvania relative to earlier efforts (Brooks, et al., 1996). These data can then be used, as needed, in the design and monitoring of wetland mitigation projects. As of this report, we now have more than 100 reference wetlands in Pennsylvania. PCM data can now be derived from our extensive database on our reference wetlands in Pennsylvania. query can be made relative to landscape position, disturbance, and desired wetland type, and the typical range of physical and biological characteristics can be generated. These, then, are the PCMs.
Cesium137
A Method for Coring
Inland, Freshwater Wetland Soils. Currently, there exists no method to core
inland freshwater wetland soils that maintains stratigraphic integrity,
minimizes unnecessary disturbance, and cores up to a depth of 50 cm. Our
objective was to create a large-volume soil coring method that could be applied
with consistency to a variety of wetland substrates. The result was a
hand-operated soil corer that resembles DeLaune, et al.'s (1978) aluminum
irrigation pipe corer used to core soft marshy substrates. Instead of aluminum
pipe, we used regular steel stovepipe and a variety of tools for insertion.
After the sample is extracted from the sediment, the handle can be quickly
removed for ease of transportation and storage of a core. The stovepipe can be
cut open to expose the soil sample so it can easily be sectioned for incremental
analysis. The corer was used to take 130 samples in 18 different sites, spanning
many different wetland substrate types. Our method has many applications,
including: radiochronologic dating, seed bank analysis, bulk density
measurement, and soil contaminants analysis.
Assessing Historical Wetland Vegetation Community Response to Disturbance. Wetlands provide functions such as wildlife habitat, flood storage, and water quality. These functions are intimately connected with wetland biota. Anthropogenic influences in the landscape may cause changes in wetland biota, leading to possible decreases and even losses of functions. Plant communities in wetlands may be influenced by the surrounding landscape. This study examined how wetland plant community composition varies with the level of urban and agricultural development in the surrounding landscape. To provide temporally quantified evidence of plant community history over the past 50 years, we dated and characterized the soil seed bank at different depths. We used Cs137 as a radioactive marker to date wetland soils (as well as the accompanying seed bank) from 11 reference wetlands in central Pennsylvania. Seed bank composition was determined by germination studies followed by a direct count of ungerminated seed. Land use in the surrounding landscape was assessed with historical aerial photographs, and disturbance was measured in the surrounding 3.14 km2. Plant communities in wetlands with highly developed landscapes had more invasive species, lower average Wetland Indicator Status, and few rare plants. Detrended Correspondence Analysis (DCA) identified percent development as an important predictor of species composition. We also found that wetland plant communities in highly developed landscapes had accelerated rates of change in species composition compared to wetland plant communities in less developed landscapes. There was significant germination from seeds dated as 43 or more years old, which has implications for the restorative capacity of seed banks.
Since the beginning of our efforts to characterize wetlands in Pennsylvania (e.g., Brooks, et al., 1996), we have strived to understand the variability in the natural wetland ecosystems throughout the state. This project has allowed for the significant enhancement of that understanding, as we have been able to greatly expand the reference sites (currently more than 100) as well as extend our study of created wetlands. We know a great deal more about the importance of location when classifying a wetland or when attempting to assess its condition. Location is now known to be a critical aspect to understand when placing a mitigation wetland into the landscape. We have extended the knowledge of wetlands, both in a regional sense, as well as in basic wetland ecology. We continue to develop and refine techniques that allow for the assessment of a wetland's condition and to design functional mitigation wetlands if a natural site is lost. We will continue to expand our knowledge of wetlands of the mid-Atlantic region and disseminate that information to the widest possible audience.
Journal Articles on this Report : 10 Displayed | Download in RIS Format
| Other project views: | All 34 publications | 14 publications in selected types | All 10 journal articles |
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Babb JS, Cole CA, Brooks RP, Rose AW. Hydrogeomorphology, watershed geology, and water quality of wetlands in central Pennsylvania. Journal of the Pennsylvania Academy of Science 1997;71(1):21-28. |
R824905 (1999) R824905 (Final) |
Exit |
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Cole CA, Brooks RP, Wardrop DH. Wetland hydrology as a function of hydrogeomorphic (HGM) subclass. Wetlands 1997;17(4):456-467. |
R824905 (1998) R824905 (1999) R824905 (Final) |
Exit |
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Cole CA, Brooks RP, Wardrop DH. Building a better wetland—a response to Linda Zug. Wetland Journal 1998;10(2):8-11. |
R824905 (1998) R824905 (1999) R824905 (Final) |
not available |
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Cole CA, Brooks RP. A comparison of the hydrologic characteristics of natural and created mainstem floodplain wetlands in Pennsylvania. Ecological Engineering 2000;14(3):221-231. |
R824905 (1999) R824905 (Final) R824803 (1998) R824803 (Final) R826110 (Final) |
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Cole CA, Brooks RP. Patterns of wetland hydrology in the Ridge and Valley Province, Pennsylvania, USA. Wetlands 2000;20(3):438-447. |
R824905 (1999) R824905 (Final) |
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Cole CA, Brooks RP, Wardrop DH. Assessing the relationship between biomass and soil organic matter in created wetlands of central Pennsylvania, USA. Ecological Engineering 2001;17(4):423-428. |
R824905 (1999) R824905 (Final) |
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Reinhardt CH, Cole CA, Brooks RP. Assessing historical wetland seed banks using Cs137: a pilot study. Journal of the Pennsylvania Academy of Science 1998;71(3):125-134. |
R824905 (1998) R824905 (1999) R824905 (Final) |
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Reinhardt CH, Cole CA, Stover LR. A method for coring inland, freshwater wetland soils. Wetlands 2000;20(2):422-426. |
R824905 (1998) R824905 (1999) R824905 (Final) |
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Shaffer PW, Cole CA, Kentula ME, Brooks RP. Effects of measurement frequency on water-level summary statistics. Wetlands 2000;20(1):148-161. |
R824905 (1999) R824905 (Final) |
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Wardrop DH, Brooks RP. The occurrence and impact of sedimentation in central Pennsylvania wetlands. Environmental Monitoring and Assessment 1998;51(1-2):119-130. |
R824905 (1999) R824905 (Final) |
Exit |
Supplemental Keywords:
aquatic, biology, Chesapeake Bay, disturbance, ecology, ecosystem, EPA Region 3, groundwater, hydrology, inventory, northeast, PA, Pennsylvania, public policy, restoration, seed banks, watersheds, wetlands., RFA, Scientific Discipline, Water, Water & Watershed, Hydrology, Ecology and Ecosystems, Watersheds, created wetlands, large scale disturbances, Penn State Cooperative Wetland Center, hydrogeomorphic categories, seed banks, aquatic ecosystems, wildlife habitat, ecology assessment modelsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.