Richard G. Lathrop

A Spatial Model of Atmospheric Deposition for the Northeastern U.S.

Spatial patterns of atmospheric deposition across the northeastern United States were evaluated and summarized in a simple model as a function of elevation and geographic position within the region. For wet deposition, 3-11 yr of annual concentration data for the major ions in precipitation were obtained from the National Atmospheric Deposition Program/National Trend Network (NADP/NTN) for 26 sites within the region. Concentration trends were evaluated by regression of annual mean concentrations against latitude and longitude. For nitrate, sulfate, and ammonium concentrations, a more than twofold linear decrease occurs from western New York and Pennsylvania to eastern Maine. These trends were combined with regional and elevational trends of precipitation amount, obtained from 30-yr records of annual precipitation at >300 weather stations, to provide long-term patterns of wet deposition. Regional trends of dry deposition of N and S compounds were determined using 2-3 yr of particle and gas concentration data collected by the National Dry Deposition Network (NDDN) and several other sources, in combination with estimates of deposition velocities. Contrary to wet deposition trends, the dominant air concentration trends were steep decreases from south to north, creating regional decreases in total deposition (wet + dry) from the southwest to the northeast. This contrast between wet and dry deposition trends suggests that within the northeast the two deposition forms are received in different proportions from different source areas, wet deposited materials primarily from areas to the west and dry deposited materials primarily from urban areas along the southern edge of the region. The equations generated describing spatial patterns of wet and dry deposition within the region were entered into a geographic information system (GIS) containing a digital elevation model (DEM) in order to develop spatially explicit predictions of atmospheric deposition for the region.

Effects of Phragmites australis (common reed) invasion on aboveground biomass and soil properties in brackish tidal marsh of the Mullica river, New Jersey

Phragmites australis (common reed) has been increasing in brackish tidal wetlands of the eastern United States coast over the last century. Whereas several researchers have documented changes in community structure, this research explores the effects of Phragmites expansion on aboveground biomass and soil properties. We used historical aerial photography and a global positioning system (GPS) to identify and age Phragmites patches within a high marsh dominated by shortgrasses (Spartina patens and Distichlis spicata). Plots along transects were established within the vegetation types to represent a gradient of species dominance and a variety of ages of the Phragmites plots. In comparison to neighboring shortgrass communities, Phragmites communities were found to have nearly 10 times the live aboveground biomass. They also had lower soil salinity at the surface, a lower water level, less pronounced microtopographic relief, and higher redox potentials. These soil factors were correlated with the age and biomass of Phragmites communities, were increasingly different with increasing Phragmites dominance along the transects, and were increasingly altered by the ages of Phragmites communities until the factors stabilized in plots of 8 yr to 15 yr of age. We propose that Phragmites expansion plays an important role in altering these soil properties and suggest a variety of mechanisms to explain these alterations.

THE EFFECT OF LANDSCAPE FEATURES ON DEPOSITION TO HUNTER MOUNTAIN, CATSKILL MOUNTAINS, NEW YORK

Atmospheric deposition to montane ecosystems is higher than to adjacent lowlands. However, because of the heterogeneity of mountainous landscapes, rates of deposition are likely to vary considerably across major landscape features. Estimates of total atmospheric deposition for montane areas in the United States are wide ranging and usually based on models that do not take into account landscape heterogeneity. Thus, little is known about the spatial variability of atmospheric deposition to these high-elevation ecosystems. We identified four landscape features that are likely to control patterns and rates of atmospheric deposition in mountainous terrain, including (1) forest edges or gaps, (2) elevation, (3) aspect, and (4) vegetation type, and we measured patterns of atmospheric deposition across them in the Catskill Mountains of New York State. We measured lead amount in the forest floor as an index of atmospheric deposition, used these data to estimate relative deposition to the Hunter Mountain massif, a...

A Multi-scale Segmentation Approach to Mapping Seagrass Habitats Using Airborne Digital Camera Imagery

The purpose of this study was to map the areal extent and density of submerged aquatic vegetation, principally the seagrasses, Zostera marina and Ruppia maritima, as part of ongoing monitoring for the Barnegat Bay, New Jersey National Estuary Program. We examine the utility of multiscale image segmentation/object-oriented image classification using the eCognition software to map seagrass across our 36,000 ha study area. The multi-scale image segmentation/ object oriented classification approach closely mirrored our conceptual model of the spatial structure of the seagrass habitats and successfully extracted the features of ecological interest. The agreement between the mapped results and the original field reference was 68 percent (Kappa � 56.5 percent) for the four category map and 83 percent (Kappa � 63.1 percent) for the presence/absence map; the agreement between the mapped results and the independent reference data was 71 percent (Kappa � 43.0 percent) for a simple presence/absence map. While the aerial digital camera imagery employed in this study had the advantage of flexible acquisition, suitable image scale, fast processing return time, and comparatively low cost, it had inconsistent radiometric response from image to image. This inconsistency made it difficult to develop a rule-based classification that was universally applicable across the 14 individual image mosaics. However, within the individual scene mosaics, using the eCognition software in a “manual classification” mode provided a flexible and time effective approach to mapping seagrass habitats.

Temporal and spatial changes in an area of the New Jersey Pine Barrens landscape

In order to document the extent of landscape fragmentation for a section of the New Jersey Pine Barrens region, we have used satellite image and spatial analysis to monitor landscape change between 1972 and 1988. Land-cover patterns were quantified by mean, number, and size of patches; and amount of edges between land cover types. During the intervening sixteen year period, fractal dimension, diversity, and contagion generally decreased while dominance, disturbance and edges increased, indicating a trend to a more dissected and disturbed landscape. There was an increase in the number of forest patches and a significant decrease in the average size of forest patches. In contrast, the mean patch size for the non-forest category has increased as a result of a coalescence of patches. The landscape fragmentation is shown by a downward shift in the distribution of forest patches by size class. These changes in landscape pattern have implications for many ecological processes and resources. Management practices need to consider landscape fragmentation in the Pinelands National Reserve in order to preserve the essential character of the Pine Barrens landscape.

Use of GIS mapping and modeling approaches to examine the spatial distribution of seagrasses in Barnegat Bay, New Jersey

Due to the ecological importance of seagrasses and recent indications of disease and dieback, we have synthesized existing mapped survey information concerning the spatial and temporal distribution of seagrass beds (primarily eelgrass,Zostera marina) in Barnegat Bay, New Jersey. Mapped surveys from the 1960s, 1970s, 1980s, and 1990s were digitized and compiled in a geographic information system to facilitate analysis. Comparison of the earlier maps with the 1990s survey shows an overall decrease of approximately 2,000 to 3,000 ha in the area of seagrass beds. While there are indications of seagrass decline, due to the great difference in mapping methods used for each of the surveys, we are cautious in directly attributing the decrease in mapped eelgrass acreage to a large-scale dieback. We examined the extent to which light could be used to predict the distribution of seagrass in Barnegat Bay. Data on Secchi depth throughout the bay were combined with a modification of an existing model (Duarte 1991) of the relationship betweenZ. marina compensation depths and light attenuation coefficients to predict the distribution of seagrasses in Barnegat Bay. When compared with mapped seagrass distribution in the bay, the model correctly predicts seagrass presence-absence over two-thirds of the time. The majority of the model error is due to errors of commission, i.e., the model predicts seagrass occurrence where it was not observed to occur. Most of this commission error is located in specific geographic areas (i.e., southern third of Little Egg Harbor and the western shoreline of the bay).

Does Phragmites Expansion Alter the Structure and Function of Marsh Landscapes? Patterns and Processes Revisited

We assess the probability and importance of different spatial distributions ofPhragmites australis (Trin Ex Steud) within brackish tidal marshes of the mid-Atlantic United States coast. The comparative impact ofPhragmites expansion on the larger coupled marsh-estuary system may partially be a function of the landscape area dominated byPhragmites, the landscape position occupied byPhragmites, the landscape pattern created byPhragmites expansions, and the resulting impact on tidal drainage networks. We find evidence thatPhragmites establishment can occur at many landscape positions, and thatPhragmites spread within a marsh can occur via colonization (new patches), linear clonal growth (along a preferred axis), or circular clonal growth (non-directional, random spread). Early intervals ofPhragmites spread were dominated by colonization for all sites except for Piermont Marsh (which appeared to be dominated by linear clonal growth) and Lang Tract (which appeared to be dominated by circular clonal growth). Although 46–100% of new patches ofPhragmites occurred within 5 m of drainages, at only one site (Piermont Marsh, New York) didPhragmites populations remain concentrated along creek banks. Except for Iona Island, New York, which appears to be in an early stage ofPhragmites invasion, patch dynamics at all sites showed an increase followed by a decrease in patch number, as independent patches became established, expanded, and coalesced. We also found some evidence for a loss of first order streams at later stages ofPhragmites invasions in several sites (Hog Island, Lang Tract, Silver Run).

Sub-pixel estimation of urban land cover components with linear mixture model analysis and Landsat Thematic Mapper imagery

We examine the utility of linear mixture modelling in the sub-pixel analysis of Landsat Enhanced Thematic Mapper (ETM) imagery to estimate the three key land cover components in an urban/suburban setting: impervious surface, managed/unmanaged lawn and tree cover. The relative effectiveness of two different endmember sets was also compared. The interior endmember set consisted of the median pixel value of the training pixels of each land cover and the exterior endmember set was the extreme pixel value. As a means of accuracy assessment, the resulting land cover estimates were compared with independent estimates obtained from the visual interpretation of digital orthophotography and classified IKONOS imagery. Impervious surface estimates from the Landsat ETM showed a high degree of similarity (RMS error (RMSE) within approximately ±10 to 15%) to that obtained using high spatial resolution digital orthophotography and IKONOS imagery. The partition of the vegetation component into tree vs grass cover was more problematic due to the greater spectral similarity between these land cover types with RMSE of approximately ±12 to 22%. The interior endmember set appeared to provide better differentiation between grass and urban tree cover than the exterior endmember set. The ability to separate the grass vs tree components in urban vegetation is of major importance to the study of the urban/suburban ecosystems as well as watershed assessment.

Integrating GIS into farmland preservation policy and decision making

Abstract The paper describes an experiment with the integration of geographic information systems (GIS) into farmland preservation techniques using the data and policies of Hunterdon County, NJ as a case study. The automation process incorporates a variety of factors as criteria for evaluating properties for a purchase of development rights. The spatially explicit criteria include evaluations of the soils, neighboring land uses, proximity to preserved farms, and local communities’ commitment to practices contributing to sustaining farming. This automation is particularly notable in that it uses a parcel-based approach at a county-wide scale. This supports both an assessment of individual farms and a broad understanding of policy outcomes and pattern across the entire county. More interesting are the emerging pattern of benefits and barriers in the automation process highlighted by this exploration.

Ground-based canopy transmittance and satellite remotely sensed measurements for estimation of coniferous forest canopy structure☆

Abstract Ground-based measurements of forest canopy transmittance provide a ready means of estimating intercepted photosynthetically active radiation (IPAR) for use in calibrating satellite remotely sensed estimates of forest canopy structure. The relationship between canopy transmittance and Landsat Thematic Mapper (TM) near IR/red radiance ratio data was examined for a temperature coniferous forest study site in northwestern Montana. Semivariogram analysis showed that the canopy transmittance and the TM near IR/red ratio had a similar spatial autocorrelation structure. Due to the fine scale patchiness of the forest canopy, the canopy transmittance and TM data were averaged at the coarser scale of the hillslope terrain units for regression analysis. These hillslope averaged data sets showed a strong linear relationship (R2 = 0.66). The transmittance measurements were converted to leaf area index (LAI) but comparison with previous results obtained for coniferous forests in Oregon (Peterson et al., 1987) shows some differences in the relationship between LAI and TM near IR/red ratio.