Effects of Forest Management Practices on Mid-Atlantic Streams

Agricultural and urban land use activities have affected stream ecosystems throughout the mid-Atlantic region. However, over 60% of the mid-Atlantic region is forested. A study was conducted to investigate the effects of management practices on forested stream ecosystems throughout the mid-Atlantic region. The study consisted of two phases: Phase 1 was a literature synthesis of information available on the effects of forest management practices on stream hydrology, erosion and sedimentation, riparian habitat alteration, chemical addition, and change in biotic diversity in the mid-Atlantic region. In Phase 2, data from mid-Atlantic streams were analyzed to assess the effects of forest land use on stream quality at the regional scale. Typically, it is the larger order streams in which monitoring and assessment occurs—3^rd order or higher streams. The impacts of forest management practices, particularly hydrologic modifications and riparian buffer zone alteration, occur predominantly in first and second order streams with cumulative impacts translating to higher order streams. Based on the literature review and mid-Atlantic Highland streams analysis, there are short-term (e.g., 2 to 5 years) effects of forest management practices on stream quality at local scales. However, signatures of cumulative effects from forest management practices are not apparent at regional scales in the Highlands. In general, forested land use is associated with good stream quality in the region compared with other land use practices.     

Paleoecological Assessment of Watershed History in PRIMENet Watersheds at Acadia National Park, USA

Paleoecological reconstructions of forest stand histories for two upland watersheds at Acadia National Park in Maine were completed to support related watershed chemistry studies. The project hypothesis was that forest type and fire history influence long-term cycling and storage of atmospheric mercury and nitrogen within watersheds. The reconstructions document differences in major vegetation composition and disturbance between the burned and unburned watersheds during the past several centuries. Pollen and charcoal stratigraphies from organic sediment accumulations in forested wet depressions indicate that the present experimental design of contrasting disturbance and forest histories has persisted during recent centuries. The unburned watershed has been dominated by spruce (Picea rubens) and fir (Abies balsamea) for 500 years or more and has not recently burned or been substantially cleared. The burned watershed is dominated by a heterogeneous forest of patchy hardwood, mixed wood, and softwood stands. A large portion of this watershed burned severely in 1947 and probably more than once in the 1800s, and has supported heterogeneous successional forests for 200 years or longer. Overall, these results support the underlying premise that the experimental design of this watershed research can be used to infer landscape controls on biogeochemical processes.     

Nutrient Export from Watersheds on Mt. Desert Island, Maine, as a Function of Land Use and Fire History

A study of 13 small (less than 7.5 km²) watersheds on Mt. Desert Island, Maine, was conducted from January 1999 to September 2000 to determine nutrient export delivery to coastal waters around the island, and to determine whether a series of wildfires in 1947 have affected nutrient export in burned watersheds. Nutrient export (nitrate–nitrogen, total nitrogen, total phosphorus) was determined for each watershed during the study period, and was normalized by watershed area. The yield of nitrate–nitrogen (N) ranged from 10 to 140 kg/km²/year. Total N yield ranged from 42 to 250 kg/km²/year. Total phosphorus (P) yield ranged from 1.4 to 7.9 kg/km²/year. Watersheds entirely within Acadia National Park (lacking human land-based nutrient sources) exported significantly less total N and total P than watersheds that were partly or entirely outside the park boundary. Nitrate–N export was not significantly different in these two groups of watersheds, perhaps because atmospheric deposition is a dominant source of nitrate in the study area. No relation was observed between burn history and nutrient export. Any effect of burn history may be masked by other landscape-level factors related to nutrient export.     

Separate estimation of N export into baseline N leakage without disturbance and N loss due to insect defoliation in a pine forest watershed in central Japan

Pine wilt disease (PWD) is caused by a non-native pest that has spread extensively throughout Japan. Previous research has indicated that most infected trees have died and the litter deposited has resulted in changes to stream-water chemistry, particularly increased nitrate (NO ₃ ^? ) concentrations. In this study, we divided stream nitrogen (N) export into N loss due to PWD and baseline N leakage without disturbance based on long-term monitoring. The annual N export was 110.0 mol N ha^?1 year^?1 in 1990 and 749.8 mol N ha^?1 year^?1 in 1997, and had decreased to 37.0 mol N ha^?1 year^?1 in 2005. N export under PWD influence was estimated to be 3697 mol N ha^?1, and N loss due to PWD was 2810 mol N ha^?1. N loss due to PWD was three times larger than baseline N leakage for the disturbed period. These changes in plant–herbivore relationships could affect N status in a forest ecosystem. So-called “semi-natural” disturbances related to non-native species invasion and increases of atmospheric N deposition caused by human activity will increase. Long-term monitoring studies of various aspects are necessary to offer insight into this ecosystem.     

Ecological Benefits of Riparian Reforestation in Urban Watersheds: Study Design and Preliminary Results

Riparian forest restoration has become a major focus of watershed initiatives to improve degraded stream ecosystems. In urban watersheds, however, the ability of riparian forests to improve stream ecosystems may be diminished due to widespread, upland disturbance. This paper presents the methodology and some preliminary results from the first year of fieldwork on a 3-year project designed to assess the ecological benefits of riparian reforestation in urban watersheds. The study is based on an integrated, multidisciplinary sampling of physical, chemical, and biological attributes at forested and non-forested sections of 12 streams with different amounts of urban developement within their watersheds. Restored sections of three streams are also being monitored over the 3-year duration of the project. Sampling and analysis will continue through December 2000.     

Monitoring global change: Comparison of forest cover estimates using remote sensing and inventory approaches

Satellite-based remote sensing offers great potential for frequent assessment of forest cover over broad spatial scales, however, calibration and validation using ground-based surveys are needed. In this study, forest cover estimates for the United States from a recently developed land surface cover map generated from satellite remote sensing data were compared to state-level inventory data from the U.S. National Resources Planning Act Timber Database. The land cover map was produced at the U.S. Geological Survey EROS Data Center and is based on imagery from the AVHRR sensor (spatial resolution 1.1 km). Vegetation type was classified using the temporal signal in the Normalized Difference Vegetation Index derived from AVHRR data. Comparisons revealed close agreement in the estimate of forest cover for extensively forested states with large polygons of relatively similar vegetation such as Oregon. Larger forest cover differences were observed in other states with some regional patterns in the level of agreement apparent.Comparisons in inventory- and remote sensing-based estimates of current forested area with potential vegetation maps indicated the magnitude of past land use change and the potential for future changes. The remote sensing approach appears to hold promise for conducting surveys of forest cover where inventory data are limited or where rates of vegetation change, due to human or climatic factors, are rapid.     

Comparing decadal responses of whole-watershed manipulations at the Bear Brook and Fernow experiments

The Bear Brook Watershed in Maine (BBWM), USA, and the Fernow Experimental Forest in West Virginia, USA, represent unique, long-term, paired, whole watershed, experimental manipulations focusing on the effects of nitrogen (N) and sulfur (S) deposition on temperate forests. Both watersheds began whole-ecosystem additions of N and S as (NH₄)₂SO₄ in the fall of 1989, and both are entering their third decade of chronic enrichment of the treated watersheds, while the reference watersheds offer unique opportunities to evaluate forest watershed responses to recovery. Differences between BBWM and Fernow in the history of atmospheric deposition, soil properties, and forest composition all contribute to different response trajectories in stream chemical exports over time. The four watersheds represent a spectrum of N enrichment and retention, ranging from ≈98% N retention in the reference watershed in Maine, to ≈20% N retention in the treated watershed in West Virginia. Despite these differences, there is evidence that mechanisms of response in base cation leaching and other processes are similar among all four watersheds. In both cases, the history to date of two decades of research and monitoring has provided new insights into ecosystem response not evident in more traditional short-term research.     

Hurricane Katrina-induced forest damage in relation to ecological factors at landscape scale

Forest stand stability to strong winds such as hurricanes has been found to be associated with a number of forest, soil and topography factors. In this study, through applying geographic information system (GIS) and logit regression, we assessed effects of forest characteristics and site conditions on pattern, severity and probability of Hurricane Katrina disturbance to forests in the Lower Pearl River Valley, USA. The factors included forest type, forest coverage, stand density, soil great group, elevation, slope, aspect, and stream buffer zone. Results showed that Hurricane Katrina damaged 60% of the total forested land in the region. The distribution and intensity of the hurricane disturbance varied across the landscape, with the bottomland hardwood forests on river floodplains most severely affected. All these factors had a variety of effects on vulnerability of the forests to the hurricane disturbance and thereby spatial patterns of the disturbance. Soil groups and stand factors including forest types, forest coverage and stand density contributed to 85% of accuracy in modeling the probability of the hurricane disturbance to forests in this region. Besides assessment of Katrina's damage, this study elucidates the great usefulness of remote sensing and GIS techniques combined with statistics modeling in assessment of large-scale risks of hurricane damage to coastal forests.     

Effect of development on water quality for seven streams in North Carolina

In this study, baseflow and storm discharges were monitored in seven watersheds of varying development density to document the effects of development on stream water quality. In addition, two of the watersheds contained package wastewater treatment facilities, which were evaluated as an alternative to residential on-site septic systems. Monthly grab samples of baseflow and flow-proportional samples of storm event discharge were collected and analyzed for nitrogen, phosphorus, sediment, and bacteria. For the five watersheds without wastewater treatment facilities, a significant linear relationship was documented between fecal coliform and enterococci levels in baseflow samples and the percentage of residential or impervious area. For the two watersheds with wastewater discharge, bacteria levels were significantly greater than those from the two relatively undeveloped watersheds. These results indicate that bacteria levels increased with increasing residential development even if many of the septic systems were replaced by a community wastewater treatment system. Computed annual export rates for ammonia nitrogen (NH₃-N) were correlated to the percentage of impervious surfaces in the watersheds, while the rates for other nitrogen forms, total phosphorus, and total suspended sediment were not. Annual export rates from the two mostly undeveloped watersheds were greater than a compilation of rates for undeveloped areas across the USA. Export from the four watersheds with more than 68 % residential land use was less than those reported from local and national studies of residential areas.     

Trends in Nitrogen Transport in Swedish Rivers

Concern about nitrogen loads in marine environments has drawn attention to the existence and possible causes of long-term trends in nitrogen transport in rivers. The present study was based on data from the Swedish environmental monitoring programme for surface water quality; the continuity of these data is internationally unique. A recently developed semiparametric method was employed to study the development of relationships between runoff and river transport of nitrogen since 1971; the observed relationships were then used to produce time series of flow-normalised transports for 66 sites in 39 river basins. Subsequent statistical analyses of flow-normalised data revealed only few significant downward trends (p 0.05) during the time period 1971–1994, and the most pronounced of these downward trends were caused by reduced point emissions of nitrogen. The number of significant upward trends was substantially larger (15 for total-N and 18 for NO₃-N). Closer examination of obtained results revealed the following: (i) the most pronounced upward trends were present downstream of lakes, and (ii) observed increases in nitrogen transport coincided in time and space with reduced point emissions of phosphorus or organic matter. This indicated that changes in the retention of nitrogen in lakes were responsible for the upward nitrogen trends. The hypothesis that nitrogen saturation of forest soils has caused a general increase in the riverine export of nitrogen from forested catchments in Sweden was not confirmed. Neither did the results indicate that improved agricultural practices have reduced the export of nitrogen from agricultural catchments.     

Statistically Extracted Fundamental Watershed Variables for Estimating the Loads of Total Nitrogen in Small Streams

Accurate estimation of total nitrogen loads is essential for evaluating conditions in the aquatic environment. Extrapolation of estimates beyond measured streams will greatly expand our understanding of total nitrogen loading to streams. Recursive partitioning and random forest regression were used to assess 85 geospatial, environmental, and watershed variables across 636 small (<585 km²) watersheds to determine which variables are fundamentally important to the estimation of annual loads of total nitrogen. Initial analysis led to the splitting of watersheds into three groups based on predominant land use (agricultural, developed, and undeveloped). Nitrogen application, agricultural and developed land area, and impervious or developed land in the 100-m stream buffer were commonly extracted variables by both recursive partitioning and random forest regression. A series of multiple linear regression equations utilizing the extracted variables were created and applied to the watersheds. As few as three variables explained as much as 76 % of the variability in total nitrogen loads for watersheds with predominantly agricultural land use. Catchment-scale national maps were generated to visualize the total nitrogen loads and yields across the USA. The estimates provided by these models can inform water managers and help identify areas where more in-depth monitoring may be beneficial.     

The new flora of northeastern USA: quantifying introduced plant species occupancy in forest ecosystems

Introduced plant species have significant negative impacts in many ecosystems and are found in many forests around the world. Some factors linked to the distribution of introduced species include fragmentation and disturbance, native species richness, and climatic and physical conditions of the landscape. However, there are few data sources that enable the assessment of introduced species occupancy in native plant communities over broad regions. Vegetation data from 1,302 forest inventory plots across 24 states in northeastern and mid-western USA were used to examine and compare the distribution of introduced species in relation to forest fragmentation across ecological provinces and forest types, and to examine correlations between native and introduced species richness. There were 305 introduced species recorded, and 66 % of all forested plots had at least one introduced species. Forest edge plots had higher constancy and occupancy of introduced species than intact forest plots, but the differences varied significantly among ecological provinces and, to a lesser degree, forest types. Weak but significant positive correlations between native and introduced species richness were observed most often in intact forests. Rosa multiflora was the most common introduced species recorded across the region, but Hieracium aurantiacum and Epipactus helleborine were dominant in some ecological provinces. Identifying regions and forest types with high and low constancies and occupation by introduced species can help target forest stands where management actions will be the most effective. Identifying seemingly benign introduced species that are more prevalent than realized will help focus attention on newly emerging invasives.     

Biological Integrity in Mid-Atlantic Coastal Plains Headwater Streams

The objective of this study was to assess the applicability of using landscape variables in conjunction with water quality and benthic data to efficiently estimate stream condition of select headwater streams in the Mid-Atlantic Coastal Plains. Eighty-two streams with riffle sites were selected from eight-two independent watersheds across the region for sampling and analyses. Clustering of the watersheds by landscape resulted in three distinct groups (forest, crop, and urban) which coincided with watersheds dominant land cover or use. We used non-parametric analyses to test differences in benthos and water chemistry between groups, and used regression analyses to evaluate responses of benthic communities to water chemistry within each of the landscape groups. We found that typical water chemistry measures associated with urban runoff such as specific conductance and dissolved chloride were significantly higher in the urban group. In the crop group, we found variables commonly associated with farming such as nutrients and pesticides significantly greater than in the other two groups. Regression analyses demonstrated that the numbers of tolerant and facultative macroinvertebrates increased significantly in forested watersheds with small shifts in pollutants, while in human use dominated watersheds the intolerant macroinvertebrates were more sensitive to shifts in chemicals present at lower concentrations. The results from this study suggest that landscape based clustering can be used to link upstream landscape characteristics, water chemistry and biotic integrity in order to assess stream condition and likely cause of degradation without the use of reference sites. Notice: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.     

Watershed Nitrogen and Mercury Geochemical Fluxes Integrate Landscape Factors in Long-term Research Watersheds at Acadia National Park, Maine, USA

This paper is an overview of this special issue devoted to watershed research in Acadia National Park (Acadia NP). The papers address components of an integrated research program on two upland watersheds at Acadia NP, USA (44° 20′ N latitude; 68° 15′ E longitude). These watersheds were instrumented in 1998 to provide a long-term foundation for regional ecological and watershed research. The research was initiated as part of EPA/NPS PRIMENet (Park Research and Intensive Monitoring of Ecosystems Network), a system of UV-monitoring stations and long-term watershed research sites located in US national parks. The initial goals at Acadia NP were to address research questions about mercury, acid rain, and nitrogen saturation developed from prior research. The project design was based on natural differences in forests and soils induced by an intense wildfire in one watershed in 1947. There is no evidence of fire in the reference watershed for several hundred years. We are testing hypotheses about controls on surface water chemistry, and bioavailability of contaminants in the contrasting watersheds. The unburned 47-ha Hadlock Brook watershed is 70% spruce-fir mature conifer forest. In contrast, burned 32-ha Cadillac Brook watershed, 4 km northeast of the Hadlock watershed, is 20% regenerating mixed northern hardwoods and 60% shrub/rocky balds. Differences in atmospheric deposition are controlled primarily by forest stand composition and age. The watersheds are gauged and have water chemistry stations at 122 m (Cadillac) and 137 m (Hadlock); watershed maximum elevations are 468 and 380 m, respectively. The stream water chemistry patterns reflect, in part, the legacy of the intense fire, which, in turn, controls differences in forest vegetation and soil characteristics. These factors result in higher nitrogen and mercury flux from the unburned watershed, reflecting differences in atmospheric deposition, contrasting ecosystem pools of nitrogen and mercury, and inferred differences in internal cycling and bioavailabilty.     

Using Resource Economics to Anticipate Forest Land Use Change in the U.S. Mid-Atlantic Region

Demands for forest, farm, and developed land are evolving in the U.S. mid-Atlantic region. The demand for land in developed uses, as well as demands for various forest and farm products are changing in response to population growth, demographic shifts, and market forces. As demand factors change so do relative land values. Land area in future forest, farm, and developed uses may shift as landowners re-evaluate relative net benefits from land use alternatives. This study examines the effects of various land demand and supply factors on the determination of land use patterns in the mid-Atlantic region. Driving variables include costs and benefits from various uses, population density, and measures of land quality. Model parameters are estimated using a binomial logit procedure. Results from the study are used to estimate proportions of forest area on a county by county basis. Simulated forest landscapes under hypothetical future conditions are prepared and illustrated using geographic information system (GIS) techniques.     

Using Ion-Exchange Resins to Study Soil Response to Experimental Watershed Acidification

Ion-exchange resins (IER) offer alternative approaches to measuring ionic movement in soils that may have advantages over traditional approaches in some settings, but more information is needed to understand how IER compare with traditional methods of measurement in forested ecosystems. At the Bear Brook Watershed in Maine (BBWM), one of two paired, forested watersheds is treated bi-monthly with S and N (28.8 and 25.2kgha⁻¹yr⁻¹ of S and N, respectively). Both IER and ceramic cup tension lysimeters were used to study soil solution responses after ∼11 years of treatment. Results from both methods showed treatments resulted in the mobilization of base cations and Al, and higher SO₄—S and inorganic N in the treated watershed. Both methods indicated similar differences in results associated with forest type (hardwoods versus softwoods), a result of differences in litter quality and atmospheric aerosol interception capacity. The correlation between lysimeter and IER data for individual analytes varied greatly. Significant correlations were evident for Na (r=0.75), Al (r=0.65), Mn (r=0.61), Fe (r=0.57), Ca (r=0.49), K (r=0.41) and NO₃—N (r=0.59). No correlation was evident between IER and soil solution data for NH₄—N and Pb. Both IER and soil solution techniques suggested similar interpretations of biogeochemical behavior in the watershed.     

A Zooplankton-N:P-Ratio Indicator for Lakes

We develop the conceptual and empirical basis for a multi-level ecosystem indicator for lakes. The ratio of total N to total P in lake water is influenced or regulated by a variety of ecosystem processes operating at several organizational levels and spatial scales: atmospheric, terrestrial watershed, lake water, and aquatic community. The character of the pelagic zooplankton assemblage is shown to be well correlated with lake water N:P ratio, with species assemblages arrayed along the N:P gradient in accordance with resource supply theory. Features of specific zooplankton assemblages or deviations from expected assemblages can provide information useful for lake managers, such as the efficiency of pollutant transfer and biomagnification of toxins, loss of cool-water refuge areas, degree of zooplanktivory and food web simplification related to changes in fisheries, and assemblage changes due to anthropogenic acidification. Evaluation of the influence of watershed land use, forest cover and vegetation type, atmospheric deposition, and basin hydrology on the supply of N and P to lake ecosystems provides a means to couple changes in the terrestrial environment to potential changes in aquatic ecosystems. Deviations of lake water N:P values from expected values based on analysis of watershed and lake basin characteristics, including values inferred from appropriate diatom microfossil deposits, can provide an independent validation and baseline reference for assessing the extent and type of disturbance. Therefore, the N:P ratio of lake water can serve as a potentially useful and inexpensively obtained proxy measure for assessing changes or shifts in the biological and nutrient status of lakes.     

Mass Balances of Mercury and Nitrogen in Burned and Unburned Forested Watersheds at Acadia National Park, Maine, USA

Precipitation and streamwater samples were collected from 16 November 1999 to 17 November 2000 in two watersheds at Acadia National Park, Maine, and analyzed for mercury (Hg) and dissolved inorganic nitrogen (DIN, nitrate plus ammonium). Cadillac Brook watershed burned in a 1947 fire that destroyed vegetation and soil organic matter. We hypothesized that Hg deposition would be higher at Hadlock Brook (the reference watershed, 10.2 μg/m²/year) than Cadillac (9.4 μg/m²/year) because of the greater scavenging efficiency of the softwood vegetation in Hadlock. We also hypothesized the Hg and DIN export from Cadillac Brook would be lower than Hadlock Brook because of elemental volatilization during the fire, along with subsequently lower rates of atmospheric deposition in a watershed with abundant bare soil and bedrock, and regenerating vegetation. Consistent with these hypotheses, Hg export was lower from Cadillac Brook watershed (0.4 μg/m²/year) than from Hadlock Brook watershed (1.3 μg/m²/year). DIN export from Cadillac Brook (11.5 eq/ha/year) was lower than Hadlock Brook (92.5 eq/ha/year). These data show that ∼50 years following a wildfire there was lower atmospheric deposition due to changes in forest species composition, lower soil pools, and greater ecosystem retention for both Hg and DIN.     

Assessing the Impacts of Forests on Human Welfare: Preliminary Results from the Mid-Atlantic Integrated Assessment

This paper presents results from the first phase of the socio-economic assessment of forest ecosystems in the Mid-Atlantic Integrated Assessment (MAIA). First, we present results of the analysis of changes in the distribution of human population and forest land use in the region. Then, trends in wood products employment and income between 1975–95 are used to examine the economic contributions of forest-based industries in the Mid-Atlantic region. Between 1970–90 the population of the MAIA region increased by 14% (4.3 million people) resulting in the average population density increasing by 25 people per square mile from 179 to 204 people per square mile. Nevertheless, population density was lower in large parts of the region in 1990 than in 1950. Although forests dominate the MAIA landscape, the trend is toward more people owning smaller forest land holdings, with developed lands increasing by 21% and rural lands decreasing by 2.64% between 1982–94. All of this suggests increasing forest fragmentation in all states of the region except New York, Pennsylvania, and West Virginia. Forest industry has been an important contributor to the economy of the MAIA region, producing an average of a quarter million jobs (2.03% of all wage employment) and generating $4.5 billion in wages and salaries each year between 1975–95. If recent trends continue, forest industry will continue to be an important source of employment and income for parts of some states in the MAIA region; however, the forest industry's importance relative to the entire mid-Atlantic economy will likely continue to decline in the 21^st century.     

Use of Stable Nitrogen Isotopes and Permeable Membrane Devices to Study what Factors Influence Freshwater Mollusk Survival in the Conasauaga River

Recent biological inventory data shows severe declines in freshwater mussel abundance and biodiversity in the Conasauga River Basin in Northwest Georgia, USA. Based on assessments of habitat conditions, mussel populations should be sustainable. We conducted a study of sediment and water quality to evaluate the impact of anthropogenic contamination on mussel populations. Permeable membrane devices (PMD), polar organic chemical integrative samplers (POCIS™), conventional water and sediment quality analyses, and stable nitrogen isotope ratio analyses (δ¹⁵N) of snails and sediments were used to assess sediment and water quality at target sites throughout the basin. Ambient concentrations of organic contaminants in water were well below any aquatic life criteria; concentrations of some nutrients were detected above aquatic life criteria levels. Most mussel species in the river are endangered or threatened; therefore, snails were collected for δ¹⁵N analyses. Mean δ¹⁵N values for snails collected at forested upper watershed sites (national forest areas) were significantly lower than δ¹⁵N values from snails in agricultural areas. δ¹⁵N values for raw cow manure and manure-treated soil were similar to δ¹⁵N values for snails collected in agricultural areas. Dissolved nitrate from water samples had elevated δ¹⁵N values similar to the upper range of δ¹⁵N values for snails in agricultural areas. Data, particularly stable nitrogen isotope data, indicates that a land use change from national forest land to agriculture alters nitrogen sources to the basin and snails. Implications of nutrient release on freshwater molluscan reproduction, growth, and survival are discussed.