We outline a view of how road networks interact with stream networks at the landscape scale and, based on examples from recent and current research, illustrate how these interactions might affect biological and ecological processes in stream and riparian systems. At the landscape scale, certain definable geometric interactions involving peak flows ( floods) and debris flows (rapid movements of soil, sediment, and large wood down steep stream channels) are influenced by the arrangement of the road network relative to the stream network. Although disturbance patches are created by peak-flow and debris-flow disturbances in mountain landscapes without roads, roads can alter the landscape distributions of the starting and stopping points of debris flows, and they can alter the balance between the intensity of flood peaks and the stream network's resistance to change. We examined this conceptual model of interactions between road networks and stream networks based on observations from a number of studies in the H. J. Andrews Experimental Forest, Oregon (U.S.A.). Road networks appear to affect floods and debris flows and thus modify disturbance patch dynamics in stream and riparian networks in mountain landscapes. We speculate that these changes may influence the rates and patterns of survival and recovery of disturbed patches in stream networks, affecting ecosystem resilience, and we outline an approach for detecting such effects based on a patch dynamics perspective. A field sampling scheme for detecting the magnitude of various road effects on stream and riparian ecology could involve (1) landscape stratification of inherent stream network susceptibility to floods or debris flows, (2) overlay of road and stream networks and creation of areas with various densities of roadstream crossings, emphasizing midslope road-stream crossings, and (3) designations of expected high-and low-impact stream segments based on numbers of upstream road-stream crossings where sampling of selected biological variables would be conducted. Efectos de Carreteras en la Hidrología, Geomorfología y Parches de Perturbación en Redes de ArroyosResumen: Desglozamos una perspectiva sobre la interacción entre redes carreteras y redes de arroyos a escala de paisaje e ilustramos como estas interacciones pueden afectar procesos biológicos y ecológicos en sistemas de arroyos y riparios en base a ejemplos que parten de investigaciones recientes y en proceso. A escala de paisaje, ciertas interacciones geométricas definibles y que involucran flujos-pico (inundaciones) y flujos de detritus (movimientos rápidos de suelo, sedimentos y piezas grandes de madera en canales con pendiente pronunciada) son influenciadas por los arreglos de la red de carreteras en relación con la red de arroyos. A pesar de que los parches de perturbación son creados por perturbaciones en los flujos-pico y en los flujos de detritus en paisajes montañosos sin carreteras, las carreteras pueden alterar las distribuciones de puntos de inicio y final de flujos de detritus en el paisaje y p...

It is believed that atmospheric deposition of S and N in the Adirondack Mountains of New York has depleted soil‐base cation pools, reduced soil base saturation (BS), and contributed to enhanced acidification of soils and surface waters. However, data to determine changes in soil characteristics are generally lacking. It is expected that soil acid‐base status will improve as acidic deposition declines in response to atmospheric emissions controls. We studied edaphic characteristics at 199 locations within 44 statistically selected Adirondack lake‐watersheds, plus 26 additional watersheds that are included in long‐term lakewater monitoring programs. The statistically selected watersheds were chosen to be representative of Adirondack watersheds containing lakes larger than 1 ha and deeper than 1 m that have lakewater acid neutralizing capacity (ANC) less than or equal to 200 μmolc L−1 Results of soil analyses were extrapolated to the watersheds of 1320 low ANC lakes. In general, the concentrations of exchangeable base cations, base saturation, and soil pH were low. More than 75% of the target lakes received drainage from watersheds having average B horizon exchangeable Ca concentrations < 0.52 cmolc kg−1, base saturation < 10.3%, and pH (H2O) < 4.5. Variations in the effective cation exchange capacity in both O and B horizons were closely correlated with soil organic matter content. These data provide a baseline against which to compare future changes in regional soil chemistry, and provide input data for aquatic and terrestrial effects models intended to project future changes in surface water chemistry, biological conditions, and forest health.

A geologic classification scheme was combined with elevation to test hypotheses regarding watershed sensitivity to acidic deposition using available regional spatial data and to delimit a highinterest area for streamwater acidification sensitivity within the Southern Appalachian Mountains region. It covered only 28% of the region, and yet included almost all known streams that have low acid neutralizing capacity (ANC ≤20 μeq l −1 ) or that are acidic (ANC ≤0). The five-class geologic classification scheme was developed based on recent lithologic maps and streamwater chemistry data for 909 sites. The vast majority of the sampled streams that had ANC ≤20 μeq l −1 and that were totally underlainby a single geologic sensitivity class occurred in the siliceous class, which is represented by such lithologies as sandstone and quartzite. Streamwater acid-base chemistry throughout the region was also found to be associated with a number of watershed features that were mapped for the entire region, in addition to lithology and elevation, including ecoregion, physiographic province, soils type, forest type and watershed area. Logistic regression was used to model the presence/absence of acid-sensitive streams throughout the region.

[1] We constructed a model-based evaluation of current and future effects of atmospheric S and N deposition on aquatic resources in the eight-state southern Appalachian Mountains region. Modeling was conducted with the MAGIC model for about 40 to 50 sites within each of three physiographic provinces, stratified by stream water acid neutralizing capacity (ANC) class. Simulations were based on assumed constant future atmospheric deposition at 1995 levels and on three regional strategies of emissions controls provided by the Southern Appalachian Mountains Initiative (SAMI), based on the Urban to Regional Multiscale One-Atmosphere model. The National Stream Survey statistical frame was used to estimate the number and percentage of stream reaches in the region that were projected to change their chemistry in response to the emissions control strategies. There was a small decline in the estimated length of projected acidic (ANC 0) streams in 2040 from the least to the most restrictive emissions control strategy, but there was little difference in projected stream length in the other ANC classes as a consequence of adopting one or another strategy. However, projections of continued future acidification were substantially larger under a scenario in which S and N deposition were held constant into the future at 1995 levels. Model results suggested that the percent of potentially acid-sensitive streams having chemistry that is chronically unsuitable for brook trout would increase slightly between 1995 and 2040 under all except the most restrictive emissions control strategy.

Many lakes in the Adirondack Mountains, New York, have acidified over the past century due to acidic atmospheric deposition. More recently, most monitored lakes have shown signs of chemical recovery (increase in acid neutralizing capacity) as sulfur deposition levels have declined in response to the Clean Air Act and other emissions control legislation. We used measured and modeled trends in past lakewater acidification and projections of future recovery from acidification to extrapolate results from judgment samples of intensively studied lakes to the population of acid-sensitive Adirondack lakes. Simulations were developed for 70 watersheds using the Model of Acidification of Groundwater in Catchments (MAGIC) to classify lakes according to their sensitivity to change in atmospheric S and N deposition. MAGIC simulations suggested that the modeled Adirondack Long-Term Monitoring Project (ALTM) and Adirondack Effects Assessment Project (AEAP) lakes were largely among the lakes in the population that had acidified most between 1850 and 1990. Most of the modeled ALTM/AEAP lakes were within the top 36% of acid sensitivity, based on model projections of past acidification and future chemical recovery, compared with the 1,829 Adirondack lakes in EPA's Environmental Monitoring and Assessment Program (EMAP) statistical frame. Results of this research will allow fuller utilization of data from on-going chemical and biological monitoring and process-level studies by providing a basis for regionalization of findings and developing/refining relationships among watershed characteristics, chemical change, and biological responses to changing levels of acidic deposition.