Robert P. Brooks

A comparison of created and natural wetlands in Pennsylvania, USA

Recent research suggests that created wetlands do not look, or function, like the natural systems they are intended to replace. Proper planning, construction, and the introduction of appropriate biotic material should initiate natural processes which continue indefinitely in a successful wetland creation project, with minimal human input. To determine if differences existed between created and natural wetlands, we compared soil matrix chroma, organic matter content, rock fragment content, bulk density, particle size distribution, vegetation species richness, total plant cover, and average wetland indicator status in created (n = 12) and natural (n = 14)wetlands in Pennsylvania (USA). Created wetlands ranged in age from two to 18 years. Soils in created wetlands had less organic matter content, greater bulk densities, higher matrix chroma, and more rock fragments than reference wetlands. Soils in reference wetlands had clay loam textures with high silt content, while sandy clay loam textures predominated in the created sites. Vegetation species richness and total cover were both greater in natural reference wetlands. Vegetation in created wetlands included a greater proportion of upland species than found in the reference wetlands. There were significant differences in soils and vegetation characteristics between younger and older created wetlands, though we could not say older created sites were trending towards the reference wetland condition. Updated site selection practices, more careful consideration of monitoring period lengths, and, especially, a stronger effort to recreate wetland types native to the region should result in increased similarity between created and natural wetlands.

Use of avian and mammalian guilds as indicators of cumulative impacts in riparian-wetland areas

A new method of assessing cumulative effects of human activities on bird and mammal communities of riparian-wetland areas was developed by using response guilds to reflect how species theoretically respond to habitat disturbance on a landscape level. All bird and mammal species of Pennsylvania were assigned values for each response guild using documented information for each species, to reflect their sensitivity to disturbances; high guild scores corresponded to low tolerance toward habitat disturbance. We hypothesized that, given limited time and resources, determining how wildife communities change in response to environmental impacts can be done more efficiently with a response-guild approach than a single-species approach. To test the model, censuses of birds and mammals were conducted along wetland and riparian areas of a protected and a disturbed watershed in central Pennsylvania. The percent of bird species with high response-guild scores (i.e., species that had specific habitat requirements and/or were neotropical migrants) remained relatively stable through the protected watershed. As intensity of habitat alteration increased through the disturbed watershed, percentage of bird species with high response-guild scores decreased. Only 2%–3% of the neotropical migrants that had specific habitat requirements were breeding residents in disturbed habitats as compared to 17%–20% in reference areas. Species in the edge and exotic guild classifications (low guild scores) were found in greater percentages in the disturbed watershed. Composition of mammalian guilds showed no consistent pattern associated with habitat disturbance. Avian response guilds reflected habitat disturbance more predictively than mammalian response guilds.

Rationale for a new generation of indicators for coastal waters.

More than half the world’s human population lives within 100 km of the coast, and that number is expected to increase by 25% over the next two decades. Consequently, coastal ecosystems are at serious risk. Larger coastal populations and increasing development have led to increased loading of toxic substances, nutrients and pathogens with subsequent algal blooms, hypoxia, beach closures, and damage to coastal fisheries. Recent climate change has led to the rise in sea level with loss of coastal wetlands and saltwater intrusion into coastal aquifers. Coastal resources have traditionally been monitored on a stressor-by-stressor basis such as for nutrient loading or dissolved oxygen. To fully measure the complexities of coastal systems, we must develop a new set of ecologic indicators that span the realm of biological organization from genetic markers to entire ecosystems and are broadly applicable across geographic regions while integrating stressor types. We briefly review recent developments in ecologic indicators and emphasize the need for improvements in understanding of stress–response relationships, contributions of multiple stressors, assessments over different spatial and temporal scales, and reference conditions. We provide two examples of ecologic indicators that can improve our understanding of these inherent problems: a) the use of photopigments as indicators of the interactive effects of nutrients and hydrology, and b) biological community approaches that use multiple taxa to detect effects on ecosystem structure and function. These indicators are essential to measure the condition of coastal resources, to diagnose stressors, to communicate change to the public, and ultimately to protect human health and the quality of the coastal environment.

Wetland hydrology as a function of hydrogeomorphic (HGM) subclass

Characterizing wetland hydrology is key to assessing relative function over a range of wetland types. However, hydrologic data are often lacking. To address this lack of information, we categorized a set of 24 reference wetlands by hydrogeomorphic (HGM) subclass from 1993 to 1995, installed monitoring wells and piezometers, and assessed local water-table levels, pH, and specific conductance by month. Four HGM wetland subclasses were common to central Pennsylvania (riparian depression (n=8), slope (n=7), mainstem floodplain (n=5), and headwater floodplain (n=4)) and formed the basis for our analysis. Median depth to water in the wells differed by HGM subclass. Riparian depressions had the shallowest depth to water (−8 cm) and headwater floodplain wetlands the greatest (−70 cm). Comparisons of the percent occurrence of a piezometric head (from comparisons between paired piezometer and slotted wells) indicated that riparian depressions and slopes had significant ground-water inputs (47 and 48%, respectively), whereas the mainstem floodplain (31%) and headwater floodplain wetlands (23%) were more surface-water-driven systems. Water occurred within the root zone (30 cm) most often for riparian depressions (80% of observations), intermediate for slopes (48%), and least for mainstem floodplains (17%) and headwater floodplains (6%). Headwater floodplain wetlands were never inundated by overbank flow during this study but instead received water from snowmelt and overland flow after rain events. Mainstem floodplain wetlands were inundated by floods during major storm events. The upper 30 cm of soil (i.e., the root zone of plants) was almost continually saturated in riparian depressions, but rarely for both floodplain systems. Slope wetlands were intermediate between riparian depressions and floodplain systems in the amount of time water was present within 30 cm of the ground surface. Riparian depressions and slopes had lower pH than floodplain systems, and pH did not vary significantly by month for any HGM subclass. Floodplain systems (both headwater and mainstem) had greater values of specific conductance than either riparian depressions or slopes; riparian depressions were the only HGM subclass to show seasonality in specific conductance. Factors other than HGM subclass that may have influenced the hydrologic pattern and water quality parameters included bedrock geology, disturbance levels, and watershed attributes.

Soil properties of reference wetlands and wetland creation projects in Pennsylvania

Soil organic matter content, matrix chroma, bulk density, total nitrogen, and pH were compared in naturally occurring reference wetlands and wetland creation projects in Pennsylvania. Soil samples were collected at two depths, 5 cm and 20 cm, from randomly selected points in 20 reference wetlands and 44 wetland creation projects. Reference sites contained more soil organic matter at 5 cm than wetland creation projects. Reference wetlands were higher in organic matter at 5 cm than at 20 cm, while wetland creation projects were uniform between the two depths. No relationship was found between time elapsed since construction and soil organic matter content in wetland creation projects. Neither landscape position nor wetland class significantly accounted for the variance in soil organic matter between reference wetlands and wetland creation projects. Organic matter was negatively related to pH, bulk density, and chroma and was positively related to total nitrogen. Hence, reference wetlands had lower pH, bulk density, and matrix chroma and were higher in total nitrogen than wetland creation projects. Wetland creation projects contained more sand and less clay than reference wetlands at 20 cm, and reference wetlands were siltier at 5 cm.

Effects of landscape patterns on biotic communities

A comparative evaluation was performed using descriptors oflandscape and land cover patterns as to how they relate tovarying levels of anthropogenic disturbance and the structure ofbiotic communities. A spatial analysis program (a modifiedversion of SPAN) was used to compute measures of land coverdiversity, dominance, contagion, scaled dominance and contagion,fractal dimension of land cover patches, mean forest-wetlandpatch size, amount of forest edge, clustering of selected foresttypes, and the largest cover patches within two 100-km2watersheds of the Ridge and Valley province of centralPennsylvania. Landscape pattern analysis was conducted on asubwatershed basis, emphasizing different levels ofresidential-agricultural versus forest land cover, the majordifference between the two watersheds. Bird and vascular plantguilds were chosen to represent the overall biotic community. Thegeneral descriptors of diversity, contagion, mean forest-wetlandpatch size, proportion of forest cover, and the amount of forestedge were most effective in reflecting the disturbance levelswithin the watersheds and changes in guild composition for bothbirds and plants.

A comparison of the hydrologic characteristics of natural and created mainstem floodplain wetlands in Pennsylvania

Abstract An understanding of wetland hydrology is critical for the assessment of the success of created wetlands relative to natural wetlands. Our objective was to determine if hydrologic characteristics differed between natural and created mainstem floodplain wetlands. We measured water depth every 6 h, between November 1, 1996 and August 31, 1998, and determined median depth to the water table, range of water table fluctuation, percent of time water was within the root zone (30 cm), and the number and duration of periods where water remained in the root zone. The natural wetlands were different from the created wetlands as median depth to water was generally deeper, there were shorter periods where soils were saturated or inundated, and there was a lower percentage of time where water was in the root zone. The created wetlands, in effect, were wetter and for longer periods. The created wetlands had a large component of open water at each site. Most naturally occurring mainstem floodplain wetlands in central Pennsylvania are vegetated with very little open water. We suggest that in the rush to make sure there is some water in mitigation wetlands we have gone too far in keeping sites inundated. In reality, many natural wetlands are merely saturated, or much drier.

Plant and soil responses to salvaged marsh surface and organic matter amendments at a created wetland in central Pennsylvania

To evaluate the efficiency of different methods of wetland plant establishment and different soil amendments, 16 experimental plots in 4 treatment groups were established at a 6-ha created palustrine wetland in Tipton, PA. Response of vegetation, soil, and hydrology were evaluated. The first objective of the study was to determine if salvaged marsh surface (SMS) from a donor wetland can be used to effectivly vegetate experimental plots. The results were compared with control plots. In addition, the possibility of using a non-toxic organic waste (leaf litter compost) as a soil amendment to created wetland projects was examined. Lurid sedge (Carex lurida) tubers were hand-planted in the leaf litter plots and in the existing mineral soils of the remaining experimental plots. SMS plots had significantly greater plant species richness, total vegetative coverage, and diversity than control plots. SMS plots contained more hydrophytic vegetation and less undesirable vegetation than control plots. SMS added significant amounts of organic matter and soil nutrients (e.g., nitrogen) to the soils in treated plots. Survivorship of hand-plantedCarex was greater (79.0 ±5.0 % for both July and August 1992) on plots treated with leaf litter compost than on plots with existing mineral soils (45.0±20.0% in July and 38.0±20.0% in August 1992). Organic matter, pH, total N, and N03 levels were all significantly greater on leaf litter plots than on hand-planted plots after the 1991 growing season. At the end of the 1992 growing season, organic matter, pH, NO3, and NH4 levels were significantly greater on leaf litter plots than on hand-planted plots. The results of the study suggest that SMS can be used as a method to successfully revegetate created wetlands. Also, the addition of leaf litter compost to experimental plots helped to retain soil moisture and provide nutrients that enhanced survivorship of hand-plantedCarex.

The Occurrence and Impact of Sedimentation in Central Pennsylvania Wetlands

Sedimentation rates and deposited sediment characteristics in twenty-five wetlands in central Pennsylvania were measured during the period Fall 1994 to Fall 1995. Wetlands were located primarily in five watersheds, and represented a variety of hydrogeomorphic (HGM) subclasses and surrounding land use. Sedimentation rates were measured via the placement of 135 Plexiglas disks. Annual organic and inorganic loadings were determined. Sedimentation rates ranged from 0 to 8 cm/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 (+/- 1417) and 550 g m2 yr-1 (+/- 589), respectively. Mean mineral and organic accretion rates were significantly different 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 was also investigated, in order to develop a conceptual model to predict sedimentation rates for a given wetland in a variety of landscape settings. Different HGM subclasses exhibited significantly different mineral and organic accumulation rates, and varied in their responses to landscape disturbance and spatial variability in sedimentation patterns. Characterization of wetland plant communities in these same wetlands showed clear associations between individual plant species and ability to tolerate sediment. Species were categorized as very tolerant, moderately tolerant, slightly tolerant, and intolerant based on their association with environments of varying sedimentation magnitude. In general, species that were categorized as very tolerant or moderately tolerant increased their percent cover (dominance) over the sedimentation gradient. These observations were supported by greenhouse germination trials of eight species of wetland plants under a variety of sediment depths, ranging from 0 to 2 cm.

ASSESSMENT OF WETLAND CONDITION: AN EXAMPLE FROM THE UPPER JUNIATA WATERSHED IN PENNSYLVANIA, USA

The requirement of Section 305(b) of the Clean Water Act (CWA) that all waters of the U.S. be assessed every two years has been historically ignored for wetlands, even though they are included in the definition of “waters of the U.S.” This paper presents the use of a landscape and rapid assessment to describe the wetland resource and assess wetland condition in the Upper Juniata watershed in central Pennsylvania, USA. A Floristic Quality Assessment Index (FQAI) is used to calibrate and refine the landscape and rapid assessments. The landscape assessment defined ecological condition of sites in terms of the degree of departure from reference standard condition (i.e., wetlands in predominantly forested settings). Criteria for condition categories were based on the literature or best professional judgment and resulted in more than half of the area of the resource being rated in high or the highest condition, while about 12% was rated in low condition. The rapid assessment adjusts the landscape assessment by accounting for the presence of Stressors and the ameliorating effects of a buffer. This resulted in a 38% decrease in the proportion of wetland area in the highest and high condition categories and almost quadrupled the area in low condition. Classification and Regression Tree (CART) analysis was used to evaluate 1) whether the results of the landscape and rapid assessments correspond to those from the more quantitative data in FQAI and 2) whether the condition categories established for the landscape and rapid assessments agree with those established using FQAI. CART results indicate that our initial delineation of condition categories for the landscape and rapid assessments should be more stringent. However, it appears that the rapid assessment does a better job of gauging the factors important to wetland condition, as measured by FQAI, than the landscape assessment. This work can serve as a template for wetland monitoring and assessment and reporting as required by the U.S. Clean Water Act. Overall, such monitoring provides information that can be used to target areas for attention or protection, prioritize sites for restoration, design restoration projects, and choose best management practices.